Sample records for blood flow restriction

  1. Brachial blood flow under relative levels of blood flow restriction is decreased in a nonlinear fashion.

    PubMed

    Mouser, J Grant; Ade, Carl J; Black, Christopher D; Bemben, Debra A; Bemben, Michael G

    2018-05-01

    Blood flow restriction (BFR), the application of external pressure to occlude venous return and restrict arterial inflow, has been shown to increase muscular size and strength when combined with low-load resistance exercise. BFR in the research setting uses a wide range of pressures, applying a pressure based upon an individual's systolic pressure or a percentage of occlusion pressure; not a directly determined reduction in blood flow. The relationship between relative pressure and blood flow has not been established. To measure blood flow in the arm under relative levels of BFR. Forty-five people (18-40 years old) participated. Arterial occlusion pressure in the right arm was measured using a 5-cm pneumatic cuff. Blood flow in the brachial artery was measured at rest and at pressures between 10% and 90% of occlusion using ultrasound. Blood flow decreased in a nonlinear, stepped fashion. Blood flow decreased at 10% of occlusion and remained constant until decreasing again at 40%, where it remained until 90% of occlusion. The decrease in brachial blood flow is not proportional to the applied relative pressure. The prescription of blood flow restriction should take into account the stimulus provided at each relative level of blood flow. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  2. MUSCLE METABOLISM WITH BLOOD FLOW RESTRICTION IN CHRONIC FATIGUE SYNDROME

    PubMed Central

    McCully, Kevin K.; Smith, Sinclair; Rajaei, Sheeva; Leigh, John S.; Natelson, Benjamin H.

    2009-01-01

    The purpose of this study was to determine if chronic fatigue syndrome (CFS) is associated with reduced blood flow and muscle oxidative metabolism. Patients with CFS according to CDC criteria (n=19) were compared to normal sedentary subjects (n = 11). Muscle blood flow was measured in the femoral artery with Doppler ultrasound after exercise. Muscle metabolism was measured in the medial gastrocnemius muscle using 31P magnetic resonance spectroscopy (MRS). Muscle oxygen saturation and blood volume were measured using near-infrared spectroscopy. CFS and controls were not different in hyperemic blood flow or phosphocreatine recovery rate. Cuff pressures of 50,60,70,80,and 90 mmHg were used to partially restrict blood flow during recovery. All pressures reduced blood flow and oxidative metabolism, with 90 mmHg reducing blood flow by 46% and oxidative metabolism by 30.7% in CFS patients. Hyperemic blood flow during partial cuff occlusion was significantly reduced in CFS patients (P < 0.01), and recovery of oxygen saturation was slower (P < 0.05). No differences were seen in the amount of reduction in metabolism with partially reduced blood flow. In conclusion, CFS patients showed evidence of reduced hyperemic flow and reduced oxygen delivery, but no evidence that this impaired muscle metabolism. Thus, CFS patients might have altered control of blood flow, but this is unlikely to influence muscle metabolism. Further, abnormalities in muscle metabolism do not appear to be responsible for the CFS symptoms. PMID:14578362

  3. Post-exercise blood flow restriction attenuates hyperemia similarly in males and females.

    PubMed

    Dankel, Scott J; Mouser, J Grant; Jessee, Matthew B; Mattocks, Kevin T; Buckner, Samuel L; Loenneke, Jeremy P

    2017-08-01

    Our laboratory recently demonstrated that post-exercise blood flow restriction attenuated muscle hypertrophy only in females, which we hypothesized may be due to alterations in post-exercise blood flow. The aim of this study is to test our previous hypothesis that sex differences in blood flow would exist when employing the same protocol. Twenty-two untrained individuals (12 females; 10 males) performed two exercise sessions, each involving one set of elbow flexion exercise to volitional failure on the right arm. The experimental condition had blood flow restriction applied for a 3 min post-exercise period, whereas the control condition did not. Blood flow was measured using an ultrasound at the brachial artery and was taken 1 and 4 min post-exercise. This corresponded to 1 min post inflation and 1 min post deflation in the experimental condition. There were no differences in the alterations in blood flow between the control and experimental conditions when examined across sex. Increases in blood flow [mean (standard deviation)] were as follows: males 1 min [control 764 (577) %; experimental 113 (108) %], males 4 min [control 346 (313) %; experimental 449 (371) %], females 1 min [control 558 (367) %; experimental 87 (105) %], and females 4 min [control 191 (183) %; experimental 328 (223) %]. It does not appear that the sex-specific attenuation of muscle hypertrophy we observed previously can be attributed to different alterations in post-exercise blood flow. Future studies may wish to replicate our previous training study, or examine alternative mechanisms which may be sex specific.

  4. Benefits of Resistance Training with Blood Flow Restriction in Knee Osteoarthritis.

    PubMed

    Ferraz, Rodrigo Branco; Gualano, Bruno; Rodrigues, Reynaldo; Kurimori, Ceci Obara; Fuller, Ricardo; Lima, Fernanda Rodrigues; DE Sá-Pinto, Ana Lúcia; Roschel, Hamilton

    2018-05-01

    Evaluate the effects of a low-intensity resistance training (LI-RT) program associated with partial blood flow restriction on selected clinical outcomes in patients with knee osteoarthritis (OA). Forty-eight women with knee OA were randomized into one of the three groups: LI-RT (30% one repetition maximum [1-RM]) associated (blood flow restriction training [BFRT]) or not (LI-RT) with partial blood flow restriction, and high-intensity resistance training (HI-RT, 80% 1-RM). Patients underwent a 12-wk supervised training program and were assessed for lower-limb 1-RM, quadriceps cross-sectional area, functionality (timed-stands test and timed-up-and-go test), and disease-specific inventory (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]) before (PRE) and after (POST) the protocol. Similar within-group increases were observed in leg press (26% and 33%, all P < 0.0001), knee extension 1-RM (23% and 22%; all P < 0.0001) and cross-sectional area (7% and 8%; all P < 0.0001) in BFRT and HI-RT, respectively, and these were significantly greater (all P < 0.05) than those of LI-RT. The BFRT and HI-RT showed comparable improvements in timed-stands test (7% and 14%, respectively), with the latter showing greater increases than LI-RT. Timed-up-and-go test scores were not significantly changed within or between groups. WOMAC physical function was improved in BFRT and HI-RT (-49% and -42%, respectively; all P < 0.05), and WOMAC pain was improved in BFRT and LI-RT (-45% and -39%, respectively; all P < 0.05). Four patients (of 16) were excluded due to exercise-induced knee pain in HI-RT. Blood flow restriction training and HI-RT were similarly effective in increasing muscle strength, quadriceps muscle mass, and functionality in knee OA patients. Importantly, BFRT was also able to improve pain while inducing less joint stress, emerging as a feasible and effective therapeutic adjuvant in OA management.

  5. Effect of training level and blood flow restriction on thermal parameters: Preliminary study

    NASA Astrophysics Data System (ADS)

    Sampaio, Lucas; Bezerra, Ewertton; Paladino, Kayo; dos Santos, João Otacílio Libardoni; Priego Quesada, Jose I.; Rossato, Mateus

    2016-11-01

    Training with blood flow restriction could lead to an effect on skin temperature. Additionally, this effect could be higher in people with lower physical fitness level due to their lower capacity of heat loss. The aim of this preliminary study was therefore to evaluate the effects of training experience on the acute and chronic thermal skin responses after performing exercise with and without blood flow restriction. The study included ten men, of these, five were trained. All subjects performed tests and re-tests for maximum strength (1 repetition maximum) through unilateral leg extensions (right thigh at 45 ± 6.7 kg and left thigh at 45.5 ± 8.1 kg, p > 0.05). The protocol consisted of four sets to concentric failure, with one-minute rest intervals between sets at an intensity corresponding to 40% of 1 RM. There were 7-day intervals between experimental sessions (150 mmHg versus unrestricted flow restriction). The thermal images were made before the protocol (pre), immediately after the end of the series (post), and 24 h afterward (post 24 h). When comparing temperature variation (Δ exercise and Δ 24 h) between groups, it was observed that the trained participants showed a greater drop in temperature 24 h after exercise with 150 mmHg restriction (confidence interval: 95% of Δ 24 h [-0.2 to -0.9 °C]) compared to untrained subjects (p = 0.006 and ES > 1.5, confidence interval: 95% Δ 24 h [-0.1 to 0.6 °C].) In conclusion, this preliminary study showed that training experience interferes with the chronic cutaneous thermal temperature of the anterior thigh when strength training associated with blood flow restriction 150 mmHg was performed.

  6. Rhabdomyolysis After Performing Blood Flow Restriction Training: A Case Report.

    PubMed

    Tabata, Shogo; Suzuki, Yukio; Azuma, Koichiro; Matsumoto, Hideo

    2016-07-01

    Tabata, S, Suzuki, Y, Azuma, K, and Matsumoto, H. Rhabdomyolysis after performing blood flow restriction training: a case report. J Strength Cond Res 30(7): 2064-2068, 2016-Rhabdomyolysis is a serious and potentially life-threatening condition related to resistance training. Despite numerous reports of low-intensity blood flow restriction (BFR) training inducing muscle hypertrophy and increasing strength, few reports of rhabdomyolysis related to BFR training have been published. Here, we report a 30-year-old obese Japanese man admitted to our hospital the day after his first BFR training session with complaints of severe muscle pain in his upper and lower extremities, high fever, and pharyngeal pain. He was diagnosed with acute rhabdomyolysis based on a serum creatine phosphokinase level of 56,475 U·L and a urine myoglobin level of >3,000 ng·ml, and with acute tonsillitis based on a white blood cell count of 17,390 and C-reactive protein level of 10.43 mg·dl. A number of factors are suspected to be related to the onset and exacerbation of rhabdomyolysis, including excessive muscular training with BFR, bacterial infection, and medication. After 10 days of hospitalization with intravenous fluids and antibacterial drugs, he recovered without complications. This case indicates that BFR training should be conducted with careful consideration of the physical condition and strength of the individual to prevent serious complications, such as rhabdomyolysis.

  7. Efficacy, Safety and Mechanisms of Blood Flow Restricted Exercise

    NASA Technical Reports Server (NTRS)

    Ploutz-Snyder, Lori

    2009-01-01

    This 20 minute talk will review studies in the peer-reviewed literature related to the effectiveness of blood flow restricted exercise as an exercise training program. There is controversy regarding the talk with cover the effectiveness of various exercise protocols and these differences will be compared and contrasted. Unpublished data from my laboratory at Syracuse University will be presented (see other abstract), as well as some unpublished work from the labs of Manini, Clark and Rasmussen (none are NASA funded).

  8. The influence of participant characteristics on the relationship between cuff pressure and level of blood flow restriction.

    PubMed

    Hunt, Julie E A; Stodart, Clare; Ferguson, Richard A

    2016-07-01

    Previous investigations to establish factors influencing the blood flow restriction (BFR) stimulus have determined cuff pressures required for complete arterial occlusion, which does not reflect the partial restriction prescribed for this training technique. This study aimed to establish characteristics that should be accounted for when prescribing cuff pressures required for partial BFR. Fifty participants were subjected to incremental blood flow restriction of the upper and lower limbs by proximal pneumatic cuff inflation. Popliteal and brachial artery diameter, blood velocity and blood flow was assessed with Doppler ultrasound. Height, body mass, limb circumference, muscle-bone cross-sectional area, adipose thickness (AT) and arterial blood pressure were measured and used in different models of hierarchical linear regression to predict the pressure at which 60 % BFR (partial occlusion) occurred. Combined analysis revealed a difference in cuff pressures required to elicit 60 % BFR in the popliteal (111 ± 12 mmHg) and brachial arteries (101 ± 12 mmHg). MAP (r = 0.58) and AT (r = -0.45) were the largest independent determinants of lower and upper body partial occlusion pressures. However, greater variance was explained by upper and lower limb regression models composed of DBP and BMI (48 %), and arm AT and DBP (30 %), respectively. Limb circumference has limited impact on the cuff pressure required for partial blood flow restriction which is in contrast to its recognised relationship with complete arterial occlusion. The majority of the variance in partial occlusion pressure remains unexplained by the predictor variables assessed in the present study.

  9. [Influence of non-sodium restricted diet with diuretics on plasma rennin, renal blood flow and in patients with cirrhotic ascites].

    PubMed

    Zhu, Yin-fang; Gu, Xi-bing; Zhu, Hong-ying; Yang, Xiao-juan; Wang, Dong; Yu, Ping

    2013-02-01

    To explore influence of sodium restricted diet and non-sodium restricted diet on plasma rennin (PRA), angiotensin II (All), ALD, renal blood flow (RBF) and subside of ascites in patients with cirrhotic ascites. Eighty cases of hepatitis B with cirrhotic ascites were randomly divided into sodium restricted diet group and non-sodium restricted diet group. 39 cases were in non-sodium restricted diet group, taking sodium chloride 6500-8000 mg daily; 41 cases were in sodium restricted diet group, taking sodium chloride 5000 mg daily. Both groups received diuretics furosemide and spironolactone. Blood sodium, urine sodium, PRA, AII, ALD, RBF ascites subsiding were compared after treatment. In non-sodium restricted diet group, blood sodium and urine sodium increased 10 days after treatment compared with those before treatment, and compared with those of sodium restricted diet group 10 days after treatment, P <0. 01. RBF increased compared with that before treatment, and compared with that of sodium restricted diet group 10 days after treatment, P < 0. 01. Renal damage induced by low blood sodium after treatment was less in non-sodium restricted diet group than that in sodium restricted diet group, P <0. 05. Ascites disappearance upon discharge was more in sodium restricted diet group than that in non-sodium restricted diet group, P <0. 01. Time of ascites disappearance was shorter in non-sodium restricted diet group than that in sodium restricted diet group, P < 0. 01. Compared with sodium restricted diet, while using diuretics of both groups, non-sodium restricted diet can increase level of blood sodium, thus increasing excretion of urine sodium and diuretic effect. It can also decrease levels of PRA, AII and ALD, increase renal blood flow and prevent renal damage induced by low blood sodium and facilitate subsiding of ascites.

  10. Cyclical blood flow restriction resistance exercise: a potential parallel to remote ischemic preconditioning?

    PubMed

    Sprick, Justin D; Rickards, Caroline A

    2017-11-01

    Remote ischemic preconditioning (RIPC) is characterized by the cyclical application of limb blood flow restriction and reperfusion and has been shown to protect vital organs during a subsequent ischemic insult. Blood flow restriction exercise (BFRE) similarly combines bouts of blood flow restriction with low-intensity exercise and thus could potentially emulate the protection demonstrated by RIPC. One concern with BFRE, however, is the potential for an augmented rise in sympathetic outflow due to greater activation of the exercise pressor reflex. Because of the use of lower workloads, however, we hypothesized that BFRE would elicit an attenuated increase in sympathetic outflow [assessed via plasma norepinephrine (NE) and mean arterial pressure (MAP)] and middle cerebral artery velocity (MCAv) when compared with conventional exercise (CE). Fifteen subjects underwent two leg press exercise interventions: 1 ) BFRE-220 mmHg bilateral thigh occlusion at 20% 1 rep-max (1RM), and 2 ) CE-65% 1RM without occlusion. Each condition consisted of 4 × 5-min cycles of exercise, with 3 × 10-reps in each cycle. Five minutes of rest and reperfusion (for BFRE) followed each cycle. MAP increased with exercise ( P < 0.001) and was 4-5 mmHg higher with CE versus BFRE ( P ≤ 0.09). Mean MCAv also increased with exercise ( P < 0.001) and was higher with CE compared with BFRE during the first bout of exercise only ( P = 0.07). Plasma NE concentration increased with CE only ( P < 0.001) and was higher than BFRE throughout exercise ( P ≤ 0.02). The attenuated sympathetic response, combined with similar cerebrovascular responses, suggest that cyclical BFRE could be explored as an alternative to CE in the clinical setting. Copyright © 2017 the American Physiological Society.

  11. A study of the blood flow restriction pressure of a tourniquet system to facilitate development of a system that can prevent musculoskeletal complications.

    PubMed

    Maeda, Hiroyuki; Iwase, Hideaki; Kanda, Akio; Morohashi, Itaru; Kaneko, Kazuo; Maeda, Mutsuhiro; Kakinuma, Yuki; Takei, Yusuke; Amemiya, Shota; Mitsui, Kazuyuki

    2017-01-01

    After an emergency or disaster, subsequent trauma can cause severe bleeding and this can often prove fatal, so promptly stopping that bleeding is crucial to preventing avoidable trauma deaths. A tourniquet is often used to restrict blood flow to an extremity. In operation and hospital, the tourniquet systems currently in use are pneumatically actuated by an air compressor, so they must have a steady power supply. These devices have several drawbacks: they vibrate and are noisy since they are pneumatically actuated and they are far from portable since they are large and heavy. Presumably, the drawbacks of pneumatic tourniquets could be overcome by developing a small, lightweight, vibration-free, quiet, and battery-powered tourniquet system. The current study built a small, vibration-free electrohydrodynamic (EHD) pump and then used that pump to restrict blood flow to the leg of rats in an experiment. This study explored the optimal conditions for effective restriction of blood flow by assessing biochemical and musculoskeletal complications following the restriction of blood flow, and this study also examined whether or not an EHD pump could be used to actuate a tourniquet system. A tourniquet cuff (width 12 mm × length 150 mm, material: polyolefin) was placed on the thigh of Wistar rats and pressure was applied for 2 hours by a device that uses EHD phenomena to generate pressure (an EHD pump). Animals were divided into four groups based on how much compressive pressure was applied with a tourniquet: 40 kPa (300 mm Hg, n = 13), 30 kPa (225 mm Hg, n = 12), 20 kPa (150 mm Hg, n = 15), or 0 kPa (controls, n = 25). Tissue oxygen saturation (regional oxygen saturation, denoted here as rSO 2 ) was measured to assess the restriction of blood flow. To assess behavior once blood flow resumed, animal activity was monitored for third day and the amount of movement was counted with digital counters. Body weight was measured before and after the behavioral experiment, and

  12. Efficacy of blood flow restriction exercise during dialysis for end stage kidney disease patients: protocol of a randomised controlled trial.

    PubMed

    Clarkson, Matthew J; Fraser, Steve F; Bennett, Paul N; McMahon, Lawrence P; Brumby, Catherine; Warmington, Stuart A

    2017-09-11

    Exercise during haemodialysis improves strength and physical function. However, both patients and clinicians are time poor, and current exercise recommendations add an excessive time burden making exercise a rare addition to standard care. Hypothetically, blood flow restriction exercise performed during haemodialysis can provide greater value for time spent exercising, reducing this time burden while producing similar or greater outcomes. This study will explore the efficacy of blood flow restriction exercise for enhancing strength and physical function among haemodialysis patients. This is a randomised controlled trial design. A total of 75 participants will be recruited from haemodialysis clinics. Participants will be allocated to a blood flow restriction cycling group, traditional cycling group or usual care control group. Both exercising groups will complete 3 months of cycling exercise, performed intradialytically, three times per week. The blood flow restriction cycling group will complete two 10-min cycling bouts separated by a 20-min rest at a subjective effort of 15 on a 6 to 20 rating scale. This will be done with pressurised cuffs fitted proximally on the active limbs during exercise at 50% of a pre-determined limb occlusion pressure. The traditional cycling group will perform a continuous 20-min bout of exercise at a subjective effort of 12 on the same subjective effort scale. These workloads and volumes are equivalent and allow for comparison of a common blood flow restriction aerobic exercise prescription and a traditional aerobic exercise prescription. The primary outcome measures are lower limb strength, assessed by a three repetition maximum leg extension test, as well as objective measures of physical function: six-minute walk test, 30-s sit to stand, and timed up and go. Secondary outcome measures include thigh muscle cross sectional area, body composition, routine pathology, quality of life, and physical activity engagement. This study will

  13. Repeated blood flow restriction induces muscle fiber hypertrophy.

    PubMed

    Sudo, Mizuki; Ando, Soichi; Kano, Yutaka

    2017-02-01

    We recently developed an animal model to investigate the effects of eccentric contraction (ECC) and blood flow restriction (BFR) on muscle tissue at the cellular level. This study clarified the effects of repeated BFR, ECC, and BFR combined with ECC (BFR+ECC) on muscle fiber hypertrophy. Male Wistar rats were assigned to 3 groups: BFR, ECC, and BFR+ECC. The contralateral leg in the BFR group served as a control (CONT). Muscle fiber cross-sectional area (CSA) of the tibialis anterior was determined after the respective treatments for 6 weeks. CSA was greater in the BFR+ECC group than in the CONT (P < 0.01) and ECC (P < 0.05) groups. CSA was greater in the BFR group than that in the CONT group (P < 0.05). These results suggest that repeated BFR alone as well as BFR+ECC induces muscle fiber hypertrophy at the cellular level. Muscle Nerve 55: 274-276, 2017. © 2016 Wiley Periodicals, Inc.

  14. Combining remote ischemic preconditioning and aerobic exercise: a novel adaptation of blood flow restriction exercise.

    PubMed

    Sprick, Justin D; Rickards, Caroline A

    2017-11-01

    Remote ischemic preconditioning (RIPC) can attenuate tissue damage sustained by ischemia-reperfusion injury. Blood flow restriction exercise (BFRE) restricts blood flow to exercising muscles. We implemented a novel approach to BFRE with cyclical bouts of blood flow restriction-reperfusion, reflecting the RIPC model. A concern about BFRE, however, is potential amplification of the exercise pressor reflex, which could be unsafe in at-risk populations. We hypothesized that cyclical BFRE would elicit greater increases in sympathetic outflow and arterial pressure than conventional exercise (CE) when performed at the same relative intensity. We also assessed the cerebrovascular responses due to potential implementation of BFRE in stroke rehabilitation. Fourteen subjects performed treadmill exercise at 65-70% maximal heart rate with and without intermittent BFR (4 × 5-min intervals of bilateral thigh-cuff pressure followed by 5-min reperfusion periods). Mean arterial pressure (MAP), plasma norepinephrine (NE), and middle and posterior cerebral artery velocities (MCAv and PCAv) were compared between trials. As expected, BFRE elicited higher concentration NE compared with CE (1249 ± 170 vs. 962 ± 114 pg/ml; P = 0.06). Unexpectedly, however, there were no differences in MAP between conditions (overall P = 0.33), and MAP was 4-5 mmHg lower with BFRE versus CE during the reperfusion periods ( P ≤ 0.05 for reperfusion periods 3 and 4 ). There were no differences in MCAv or PCAv between trials ( P ≥ 0.22), suggesting equivalent cerebrometabolic demand. The exaggerated sympathoexcitatory response with BFRE was not accompanied by higher MAP, likely because of the cyclical reperfusions. This cyclical BFRE paradigm could be adapted to cardiac or stroke rehabilitation, where exercising patients could benefit from the cardio and cerebro protection associated with RIPC. Copyright © 2017 the American Physiological Society.

  15. A Case of Rhabdomyolysis Caused by Blood Flow-Restricted Resistance Training.

    PubMed

    Krieger, Joshua; Sims, Donald; Wolterstorff, Cameron

    2018-01-01

    Blood flow-restricted resistance (BFRR) training is effective as a means to improve muscle strength and size while enduring less mechanical stress. It is generally safe but can have adverse effects. We present a case of an active duty Soldier who developed rhabdomyolysis as a result of a single course of BFRR training. He was presented to the emergency department with bilateral lower extremity pain, was admitted for electrolyte monitoring and rehydration, and had an uncomplicated hospital course and full recovery. This is an increasingly common mode of rehabilitation in the military, and practitioners and providers should be aware of it and its possible adverse effects. 2018.

  16. Effects of maternal nutrient restriction followed by realimentation during midgestation on uterine blood flow in beef cows

    USDA-ARS?s Scientific Manuscript database

    The objective was to examine the effect of maternal nutrient restriction followed by realimentation during mid-gestation on uterine blood flow (BF). On Day 30 of pregnancy, lactating, multiparous Simmental beef cows were assigned randomly to treatments: control (CON; 100% National Research Council; ...

  17. Caloric restriction increases ketone bodies metabolism and preserves blood flow in aging brain.

    PubMed

    Lin, Ai-Ling; Zhang, Wei; Gao, Xiaoli; Watts, Lora

    2015-07-01

    Caloric restriction (CR) has been shown to increase the life span and health span of a broad range of species. However, CR effects on in vivo brain functions are far from explored. In this study, we used multimetric neuroimaging methods to characterize the CR-induced changes of brain metabolic and vascular functions in aging rats. We found that old rats (24 months of age) with CR diet had reduced glucose uptake and lactate concentration, but increased ketone bodies level, compared with the age-matched and young (5 months of age) controls. The shifted metabolism was associated with preserved vascular function: old CR rats also had maintained cerebral blood flow relative to the age-matched controls. When investigating the metabolites in mitochondrial tricarboxylic acid cycle, we found that citrate and α-ketoglutarate were preserved in the old CR rats. We suggest that CR is neuroprotective; ketone bodies, cerebral blood flow, and α-ketoglutarate may play important roles in preserving brain physiology in aging. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  18. The role of blood flow distribution in the regulation of cerebral oxygen availability in fetal growth restriction.

    PubMed

    Luria, Oded; Bar, Jacob; Kovo, Michal; Malinger, Gustavo; Golan, Abraham; Barnea, Ofer

    2012-04-01

    Fetal growth restriction (FGR) elicits hemodynamic compensatory mechanisms in the fetal circulation. These mechanisms are complex and their effect on the cerebral oxygen availability is not fully understood. To quantify the contribution of each compensatory mechanism to the fetal cerebral oxygen availability, a mathematical model of the fetal circulation was developed. The model was based on cardiac-output distribution in the fetal circulation. The compensatory mechanisms of FGR were simulated and their effects on cerebral oxygen availability were analyzed. The mathematical analysis included the effects of cerebral vasodilation, placental resistance to blood flow, degree of blood shunting by the ductus venosus and the effect of maternal-originated placental insufficiency. The model indicated a unimodal dependency between placental blood flow and cerebral oxygen availability. Optimal cerebral oxygen availability was achieved when the placental blood flow was mildly reduced compared to the normal flow. This optimal ratio was found to increase as the hypoxic state of FGR worsens. The model indicated that cerebral oxygen availability is increasingly dependent on the cardiac output distribution as the fetus gains weight. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

  19. Femoral Blood Flow and Cardiac Output During Blood Flow Restricted Leg Press Exercise

    NASA Technical Reports Server (NTRS)

    Everett, M. E.; Hackney, K.; Ploutz-Snyder, L.

    2011-01-01

    Low load blood flow restricted resistance exercise (LBFR) causes muscle hypertrophy that may be stimulated by the local ischemic environment created by the cuff pressure. However, local blood flow (BF) during such exercise is not well understood. PURPOSE: To characterize femoral artery BF and cardiac output (CO) during leg press exercise (LP) performed at a high load (HL) and low load (LL) with different levels of cuff pressure. METHODS: Eleven subjects (men/women 4/7, age 31.4+/-12.8 y, weight 68.9+/-13.2 kg, mean+/-SD) performed 3 sets of supine left LP to fatigue with 90 s of rest in 4 conditions: HL (%1-RM/cuff pressure: 80%/0); LL (20%/0); LBFR(sub DBP) (20%/1.3 x diastolic blood pressure, BP); LBFR(sub SBP) (20%/1.3 x supine systolic BP). The cuff remained inflated throughout the LBFR exercise sessions. Artery diameter, velocity time integral (VTI), and stroke volume (SV) were measured using Doppler ultrasound at rest and immediately after each set of exercise. Heart rate (HR) was monitored using a 3-lead ECG. BF was calculated as VTI x vessel cross-sectional area. CO was calculated as HR x SV. The data obtained after each set of exercise were averaged and used for analyses. Multi-level modeling was used to determine the effect of exercise condition on dependent variables. Statistical significance was set a priori at p< 0.05. RESULTS: Artery diameter did not change from baseline. BF increased (p<0.05) after exercise in each condition except LBFR(sub SBP) in the order of HL (12.73+/-1.42 cm3,mean+/-SE) > LL (9.92+/-0.82 cm3) > LBFR(sub dBP)(6.47+/-0.79 cm3) > LBFR(sub SBP) (3.51+/-0.59 cm3). Blunted exercise induced increases occurred in HR, SV, and CO after LBFR compared to HL and LL. HR increased 45% after HL and LL and 28% after LBFR (p<0.05), but SV increased (p<0.05) only after HL. Consequently, the increase (p<0.05) in CO was greater in HL and LL (approximately 3 L/min) than in LBFR (approximately 1 L/min). CONCLUSION: BF during LBFR(sub SBP) was 1/3 of

  20. Low-Intensity Sprint Training With Blood Flow Restriction Improves 100-m Dash.

    PubMed

    Behringer, Michael; Behlau, Daniel; Montag, Johannes C K; McCourt, Molly L; Mester, Joachim

    2017-09-01

    Behringer, M, Behlau, D, Montag, JCK, McCourt, ML, and Mester, J. Low-intensity sprint training with blood flow restriction improves 100-m dash. J Strength Cond Res 31(9): 2462-2472, 2017-We investigated the effects of practical blood flow restriction (pBFR) of leg muscles during sprint training on the 100-m dash time in well-trained sport students. Participants performed 6 × 100-m sprints at 60-70% of their maximal 100-m sprinting speed twice a week for 6 weeks, either with (intervention group [IG]; n = 12) or without pBFR (control group [CG]; n = 12). The 100-m dash time significantly decreased more in the IG (-0.38 ± 0.24 seconds) than in the CG (-0.16 ± 0.17 seconds). The muscle thickness of the rectus femoris increased only in the IG, whereas no group-by-time interactions were found for the muscle thickness of the biceps femoris and the biceps brachii. The maximal isometric force, measured using a leg press, did not change in either group. However, the rate of force development improved in the IG. Growth hormone, testosterone, insulin-like growth factor 1, and cortisol concentrations did not significantly differ between both groups at any measurement time point (pre, 1 minute, 20 minutes, 120 minutes, and 24 hours after the 6 all-out sprints of the first training session). The muscle damage marker h-FABP increased significantly more in the CG than in the IG. The pBFR improved the 100-m dash time significantly more than low-intensity sprint interval training alone. Other noted benefits of training with pBFR were a decreased level of muscle damage, a greater increase of the rectus femoris muscle thickness, and a higher rate of force development. However, the tested hormones were unable to explain the additional beneficial effects.

  1. Blood flow restriction training and the exercise pressor reflex: a call for concern.

    PubMed

    Spranger, Marty D; Krishnan, Abhinav C; Levy, Phillip D; O'Leary, Donal S; Smith, Scott A

    2015-11-01

    Blood flow restriction (BFR) training (also known as Kaatsu training) is an increasingly common practice employed during resistance exercise by athletes attempting to enhance skeletal muscle mass and strength. During BFR training, blood flow to the exercising muscle is mechanically restricted by placing flexible pressurizing cuffs around the active limb proximal to the working muscle. This maneuver results in the accumulation of metabolites (e.g., protons and lactic acid) in the muscle interstitium that increase muscle force and promote muscle growth. Therefore, the premise of BFR training is to simulate and receive the benefits of high-intensity resistance exercise while merely performing low-intensity resistance exercise. This technique has also been purported to provide health benefits to the elderly, individuals recovering from joint injuries, and patients undergoing cardiac rehabilitation. Since the seminal work of Alam and Smirk in the 1930s, it has been well established that reductions in blood flow to exercising muscle engage the exercise pressor reflex (EPR), a reflex that significantly contributes to the autonomic cardiovascular response to exercise. However, the EPR and its likely contribution to the BFR-mediated cardiovascular response to exercise is glaringly missing from the scientific literature. Inasmuch as the EPR has been shown to generate exaggerated increases in sympathetic nerve activity in disease states such as hypertension (HTN), heart failure (HF), and peripheral artery disease (PAD), concerns are raised that BFR training can be used safely for the rehabilitation of patients with cardiovascular disease, as has been suggested. Abnormal BFR-induced and EPR-mediated cardiovascular complications generated during exercise could precipitate adverse cardiovascular or cerebrovascular events (e.g., cardiac arrhythmia, myocardial infarction, stroke and sudden cardiac death). Moreover, although altered EPR function in HTN, HF, and PAD underlies our

  2. Effect of prolonged hypokinesia on tissue blood flow

    NASA Technical Reports Server (NTRS)

    Levites, Z. P.; Fedotova, V. F.

    1979-01-01

    The influence of hypokinesia on the blood flow in the tissues of rabbits was studied. Motor activity of animals was restricted during 90 days and blood flow recorded through resorption rate of NaI-131. Perfusion of tissues under the influence of hypokinesia was found to be reduced.

  3. Some potential blood flow experiments for space

    NASA Technical Reports Server (NTRS)

    Cokelet, G. R.; Meiselman, H. J.; Goldsmith, H. L.

    1979-01-01

    Blood is a colloidal suspension of cells, predominantly erythrocytes, (red cells) in an aqueous solution called plasma. Because the red cells are more dense than the plasma, and because they tend to aggregate, erythrocyte sedimentation can be significant when the shear stresses in flowing blood are small. This behavior, coupled with equipment restrictions, has prevented certain definitive fluid mechanical studies from being performed with blood in ground-based experiments. Among such experiments, which could be satisfactorily performed in a microgravity environment, are the following: (1) studies of blood flow in small tubes, to obtain pressure-flow rate relationships, to determine if increased red cell aggregation can be an aid to blood circulation, and to determine vessel entrance lengths, and (2) studies of blood flow through vessel junctions (bifurcations), to obtain information on cell distribution in downstream vessels of (arterial) bifurcations, and to test flow models of stratified convergent blood flows downstream from (venous) bifurcations.

  4. Acute physiological responses to low-intensity blood flow restriction cycling.

    PubMed

    Thomas, H J; Scott, B R; Peiffer, J J

    2018-04-09

    Blood flow restriction (BFR) during interval cycling may stimulate aerobic and anaerobic adaptations. However, acute physiological responses to BFR interval cycling have not been extensively investigated. Eighteen males completed low-intensity (LI), low-intensity with BFR (LI BFR ) and high-intensity (HI) interval cycling sessions in randomised and counterbalanced order. These included a standardised warm-up and three two-min intervals interspersed with two-min recovery. Interval intensity during HI, LI and LI BFR were 85%, 40% and 40% of peak power output obtained during graded exercise tests. During LI BFR , 80% arterial occlusion was applied to both legs during the interval efforts and removed during recovery. Continuous measures of heart rate (HR), cardiac output (CO) and oxygen consumption (V˙O 2 ) were recorded. Blood pressure (BP) and rating of perceived exertion (RPE) were measured following intervals. Blood lactate concentration was measured pre- and post-exercise. BP, HR, CO, V˙O 2 , lactate and RPE were greatest during HI. During the active intervals, BP, HR and CO were greater during LI BFR than LI. V˙O 2 during recovery periods were greater in LI BFR than LI. Post-session lactate was greater during LI BFR than LI. Importantly, mean arterial pressure during interval three was significantly greater in LI BFR (124±2mmHg) than HI (114±3mmHg). LI BFR increases cardiovascular and metabolic stress compared with LI and could provide an alternative aerobic training method for individuals unable to perform high-intensity exercise. However, increases in mean arterial pressure during LI BFR indicates high myocardial workload, and practitioners should therefore use caution if prescribing LI BFR for vascular compromised individuals. Copyright © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  5. Effects of low-intensity bench press training with restricted arm muscle blood flow on chest muscle hypertrophy: a pilot study.

    PubMed

    Yasuda, Tomohiro; Fujita, Satoshi; Ogasawara, Riki; Sato, Yoshiaki; Abe, Takashi

    2010-09-01

    Single-joint resistance training with blood flow restriction (BFR) results in significant increases in arm or leg muscle size and single-joint strength. However, the effect of multijoint BFR training on both blood flow restricted limb and non-restricted trunk muscles remain poorly understood. To examine the impact of BFR bench press training on hypertrophic response to non-restricted (chest) and restricted (upper-arm) muscles and multi-joint strength, 10 young men were randomly divided into either BFR training (BFR-T) or non-BFR training (CON-T) groups. They performed 30% of one repetition maximal (1-RM) bench press exercise (four sets, total 75 reps) twice daily, 6 days week(-1) for 2 weeks. During the exercise session, subjects in the BFR-T group placed elastic cuffs proximally on both arms, with incremental increases in external compression starting at 100 mmHg and ending at 160 mmHg. Before and after the training, triceps brachii and pectoralis major muscle thickness (MTH), bench press 1-RM and serum anabolic hormones were measured. Two weeks of training led to a significant increase (P<0.05) in 1-RM bench press strength in BFR-T (6%) but not in CON-T (-2%). Triceps and pectoralis major MTH increased 8% and 16% (P<0.01), respectively, in BFR-T, but not in CON-T (-1% and 2%, respectively). There were no changes in baseline concentrations of anabolic hormones in either group. These results suggest that BFR bench press training leads to significant increases in muscle size for upper arm and chest muscles and 1-RM strength.

  6. The effects of sildenafil citrate (Viagra) on uterine blood flow and well being in the intrauterine growth-restricted fetus.

    PubMed

    Miller, Suzanne L; Loose, Jan M; Jenkin, Graham; Wallace, Euan M

    2009-01-01

    This study examined whether the type-5 phosphodiesterase inhibitor sildenafil citrate (Viagra; Pfizer, New York, NY) could increase uterine blood flow in intrauterine growth restriction (IUGR), thereby improving fetal oxygenation and well being. In fetal sheep, we induced IUGR at 105-110 days (0.7 gestation) using single umbilical artery ligation (SUAL). In SUAL and control animals, we measured uterine blood flow (UBF) and blood gases before and after sildenafil administration. SUAL fetuses were hypoxemic compared with controls. Following sildenafil, UBF was significantly decreased in both SUAL and control ewes for approximately 40 minutes. In response to sildenafil, pO(2) was decreased in SUAL and control fetuses and both groups displayed significant hypotension and tachycardia. At postmortem SUAL fetal body weight was significantly reduced by 23% compared with controls. Sildenafil does not improve UBF or fetal well being in SUAL-induced IUGR pregnancies and should be used with caution in IUGR and healthy pregnancies because of its detrimental effects on uteroplacental perfusion and on the fetus.

  7. Impact of Blood Flow Restriction Exercise on Muscle Fatigue Development and Recovery.

    PubMed

    Husmann, Florian; Mittlmeier, Thomas; Bruhn, Sven; Zschorlich, Volker; Behrens, Martin

    2018-03-01

    The present study was designed to provide mechanistic insight into the time course and etiology of muscle fatigue development and recovery during and after low-intensity exercise when it is combined with blood flow restriction (BFR). Seventeen resistance-trained males completed four sets of low-intensity isotonic resistance exercise under two experimental conditions: knee extension exercise (i) with BFR and (ii) without BFR (CON). Neuromuscular tests were performed before, during (immediately after each set of knee extension exercise), and 1, 2, 4, and 8 min after each experimental condition. Maximal voluntary torque, quadriceps twitch torque in response to paired electrical stimuli at 10 Hz (PS10) and 100 Hz (PS100), PS10·PS100 ratio as an index of low-frequency fatigue, and voluntary activation were measured under isometric conditions. Perceptual and EMG data were recorded during each exercise condition. After the first set of exercise, BFR induced significantly greater reductions in maximal voluntary torque, PS100, and PS10·PS100 ratio compared with CON. These parameters progressively declined throughout the BFR protocol but recovered substantially within 2 min postexercise when blood flow was restored. Neither a progressive decline in the course of the exercise protocol nor a substantial recovery of these parameters occurred during and after CON. Only at exercise termination, voluntary activation differed significantly between BFR and CON with greater reductions during BFR. At the early stage of exercise, BFR exacerbated the development of muscle fatigue mainly due to a pronounced impairment in contractile function. Despite the high level of muscle fatigue during BFR exercise, the effect of BFR on muscle fatigue was diminished after 2 min of reperfusion, suggesting that BFR has a strong but short-lasting effect on neuromuscular function.

  8. Muscle damage and repeated bout effect following blood flow restricted exercise.

    PubMed

    Sieljacks, Peter; Matzon, Andreas; Wernbom, Mathias; Ringgaard, Steffen; Vissing, Kristian; Overgaard, Kristian

    2016-03-01

    Blood-flow restricted resistance exercise training (BFRE) is suggested to be effective in rehabilitation training, but more knowledge is required about its potential muscle damaging effects. Therefore, we investigated muscle-damaging effects of BFRE performed to failure and possible protective effects of previous bouts of BFRE or maximal eccentric exercise (ECC). Seventeen healthy young men were allocated into two groups completing two exercise bouts separated by 14 days. One group performed BFRE in both exercise bouts (BB). The other group performed ECC in the first and BFRE in the second bout. BFRE was performed to failure. Indicators of muscle damage were evaluated before and after exercise. The first bout in the BB group led to decrements in maximum isometric torque, and increases in muscle soreness, muscle water retention, and serum muscle protein concentrations after exercise. These changes were comparable in magnitude and time course to what was observed after first bout ECC. An attenuated response was observed in the repeated exercise bout in both groups. We conclude that unaccustomed single-bout BFRE performed to failure induces significant muscle damage. Additionally, both ECC and BFRE can precondition against muscle damage induced by a subsequent bout of BFRE.

  9. Transcriptional profiling of rat skeletal muscle hypertrophy under restriction of blood flow.

    PubMed

    Xu, Shouyu; Liu, Xueyun; Chen, Zhenhuang; Li, Gaoquan; Chen, Qin; Zhou, Guoqing; Ma, Ruijie; Yao, Xinmiao; Huang, Xiao

    2016-12-15

    Blood flow restriction (BFR) under low-intensity resistance training (LIRT) can produce similar effects upon muscles to that of high-intensity resistance training (HIRT) while overcoming many of the restrictions to HIRT that occurs in a clinical setting. However, the potential molecular mechanisms of BFR induced muscle hypertrophy remain largely unknown. Here, using a BFR rat model, we aim to better elucidate the mechanisms regulating muscle hypertrophy as induced by BFR and reveal possible clinical therapeutic targets for atrophy cases. We performed genome wide screening with microarray analysis to identify unique differentially expressed genes during rat muscle hypertrophy. We then successfully separated the differentially expressed genes from BRF treated soleus samples by comparing the Affymetrix rat Genome U34 2.0 array with the control. Using qRT-PCR and immunohistochemistry (IHC) we also analyzed other related differentially expressed genes. Results suggested that muscle hypertrophy induced by BFR is essentially regulated by the rate of protein turnover. Specifically, PI3K/AKT and MAPK pathways act as positive regulators in controlling protein synthesis where ubiquitin-proteasome acts as a negative regulator. This represents the first general genome wide level investigation of the gene expression profile in the rat soleus after BFR treatment. This may aid our understanding of the molecular mechanisms regulating and controlling muscle hypertrophy and provide support to the BFR strategies aiming to prevent muscle atrophy in a clinical setting. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Blood flow patterns underlie developmental heart defects

    PubMed Central

    Midgett, Madeline; Thornburg, Kent

    2017-01-01

    Although cardiac malformations at birth are typically associated with genetic anomalies, blood flow dynamics also play a crucial role in heart formation. However, the relationship between blood flow patterns in the early embryo and later cardiovascular malformation has not been determined. We used the chicken embryo model to quantify the extent to which anomalous blood flow patterns predict cardiac defects that resemble those in humans and found that restricting either the inflow to the heart or the outflow led to reproducible abnormalities with a dose-response type relationship between blood flow stimuli and the expression of cardiac phenotypes. Constricting the outflow tract by 10–35% led predominantly to ventricular septal defects, whereas constricting by 35–60% most often led to double outlet right ventricle. Ligation of the vitelline vein caused mostly pharyngeal arch artery malformations. We show that both cardiac inflow reduction and graded outflow constriction strongly influence the development of specific and persistent abnormal cardiac structure and function. Moreover, the hemodynamic-associated cardiac defects recapitulate those caused by genetic disorders. Thus our data demonstrate the importance of investigating embryonic blood flow conditions to understand the root causes of congenital heart disease as a prerequisite to future prevention and treatment. NEW & NOTEWORTHY Congenital heart defects result from genetic anomalies, teratogen exposure, and altered blood flow during embryonic development. We show here a novel “dose-response” type relationship between the level of blood flow alteration and manifestation of specific cardiac phenotypes. We speculate that abnormal blood flow may frequently underlie congenital heart defects. PMID:28062416

  11. Integrable Rosochatius deformations of the restricted soliton flows

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhou Ruguang

    2007-10-15

    A method to construct integrable Rosochatius deformations of the restricted soliton flows in the setup of Lax formulation is presented. The integrable Rosochatius deformations of the restricted soliton flows such as the restricted Ablowitz-Kaup-Newell-Segur flow, the restricted Tu-Meng flow, the restricted Tu flow with Neumann-type constraints, and the restricted modified Korteweg-de Vries flow, together with their Lax representations, are presented. In addition, a Lax representation of the Jacobi-Rosochatius system is obtained.

  12. Effect of strength training with blood flow restriction on muscle power and submaximal strength in eumenorrheic women.

    PubMed

    Gil, Ana L S; Neto, Gabriel R; Sousa, Maria S C; Dias, Ingrid; Vianna, Jeferson; Nunes, Rodolfo A M; Novaes, Jefferson S

    2017-03-01

    Blood flow restriction (BFR) training stimulates muscle size and strength by increasing muscle activation, accumulation of metabolites and muscle swelling. This method has been used in different populations, but no studies have evaluated the effects of training on muscle power and submaximal strength (SS) in accounted for the menstrual cycle. The aim of this study was to analyse the effect of strength training (ST) with BFR on the muscle power and SS of upper and lower limbs in eumenorrheic women. Forty untrained women (18-40 years) were divided randomly and proportionally into four groups: (i) high-intensity ST at 80% of 1RM (HI), (ii) low-intensity ST at 20% of 1RM combined with partial blood flow restriction (LI + BFR), (iii) low-intensity ST at 20% of 1RM (LI) and d) control group (CG). Each training group performed eight training sessions. Tests with a medicine ball (MB), horizontal jump (HJ), vertical jump (VJ), biceps curls (BC) and knee extension (KE) were performed during the 1st day follicular phase (FP), 14th day (ovulatory phase) and 26-28th days (luteal phase) of the menstrual cycle. There was no significant difference among groups in terms of the MB, HJ, VJ or BC results at any time point (P>0·05). SS in the KE exercise was significantly greater in the LI + BFR group compared to the CG group (P = 0·014) during the LP. Therefore, ST with BFR does not appear to improve the power of upper and lower limbs and may be an alternative to improve the SS of lower limbs of eumenorrheic women. © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  13. The Effects of Blood Flow Restricted Electrostimulation on Strength and Hypertrophy.

    PubMed

    Slysz, Joshua T; Burr, Jamie F

    2018-05-22

    The combined effect of neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) on muscle mass and strength has not been thoroughly investigated. To examine the effects of combined and independent BFR and a low-intensity NMES on skeletal muscle adaptation. Exploratory study. Laboratory. Twenty recreationally active subjects. Subjects had each leg randomly allocated to 1 of 4 possible intervention groups: (1) cyclic BFR alone, (2) NMES alone, (3) BFR + NMES, or (4) control. Each leg was stimulated in its respective intervention group for 32 minutes, 4 days per week for 6 weeks. Mean differences in size (in grams) and isometric strength (in kilograms), between week 0 and week 6, were calculated for each group. Leg strength increased 32 (19) kg in the BFR + NMES group, which differed from the 3 (11) kg change in the control group (P = .03). The isolated NMES and BFR groups revealed increases of 16 (28) kg and 18 (17) kg, respectively, but these did not statistically differ from the control, or one another. No alterations were statistically significant for leg size. Compared with a control that received no treatment, the novel combination of BFR and NMES led to increasing muscular strength of the knee extensors, but not muscle mass which had a large interindividual variability in response.

  14. Haemodynamics of aerobic and resistance blood flow restriction exercise in young and older adults.

    PubMed

    Staunton, Craig A; May, Anthony K; Brandner, Christopher R; Warmington, Stuart A

    2015-11-01

    Light-load blood flow restriction exercise (BFRE) may provide a novel training method to limit the effects of age-related muscle atrophy in older adults. Therefore, the purpose of this study was to compare the haemodynamic response to resistance and aerobic BFRE between young adults (YA; n = 11; 22 ± 1 years) and older adults (OA; n = 13; 69 ± 1 years). On two occasions, participants completed BFRE or control exercise (CON). One occasion was leg press (LP; 20 % 1-RM) and the other was treadmill walking (TM; 4 km h(-1)). Haemodynamic responses (HR, Q, SV and BP) were recorded during baseline and exercise. At baseline, YA and OA were different for some haemodynamic parameters (e.g. BP, SV). The relative responses to BFRE were similar between YA and OA. Blood pressures increased more with BFRE, and also for LP over TM. Q increased similarly for BFRE and CON (in both LP and TM), but with elevated HR and reduced SV (TM only). While BFR conferred slightly greater haemodynamic stress than CON, this was lower for walking than leg-press exercise. Given similar response magnitudes between YA and OA, these data support aerobic exercise being a more appropriate BFRE for prescription in older adults that may contribute to limiting the effects of age-related muscle atrophy.

  15. Uterine artery blood flow, fetal hypoxia and fetal growth

    PubMed Central

    Browne, Vaughn A.; Julian, Colleen G.; Toledo-Jaldin, Lillian; Cioffi-Ragan, Darleen; Vargas, Enrique; Moore, Lorna G.

    2015-01-01

    Evolutionary trade-offs required for bipedalism and brain expansion influence the pregnancy rise in uterine artery (UtA) blood flow and, in turn, reproductive success. We consider the importance of UtA blood flow by reviewing its determinants and presenting data from 191 normotensive (normal, n = 125) or hypertensive (preeclampsia (PE) or gestational hypertension (GH), n = 29) Andean residents of very high (4100–4300 m) or low altitude (400 m, n = 37). Prior studies show that UtA blood flow is reduced in pregnancies with intrauterine growth restriction (IUGR) but whether the IUGR is due to resultant fetal hypoxia is unclear. We found higher UtA blood flow and Doppler indices of fetal hypoxia in normotensive women at high versus low altitude but similar fetal growth. UtA blood flow was markedly lower in early-onset PE versus normal high-altitude women, and their fetuses more hypoxic as indicated by lower fetal heart rate, Doppler indices and greater IUGR. We concluded that, despite greater fetal hypoxia, fetal growth was well defended by higher UtA blood flows in normal Andeans at high altitude but when compounded by lower UtA blood flow in early-onset PE, exaggerated fetal hypoxia caused the fetus to respond by decreasing cardiac output and redistributing blood flow to help maintain brain development at the expense of growth elsewhere. We speculate that UtA blood flow is not only an important supply line but also a trigger for stimulating the metabolic and other processes regulating feto-placental metabolism and growth. Studies using the natural laboratory of high altitude are valuable for identifying the physiological and genetic mechanisms involved in human reproductive success. PMID:25602072

  16. Relationship Between Blood Flow and Performance Recovery: A Randomized, Placebo-Controlled Study.

    PubMed

    Borne, Rachel; Hausswirth, Christophe; Bieuzen, François

    2017-02-01

    To investigate the effect of different limb blood-flow levels on cycling-performance recovery, blood lactate concentration, and heart rate. Thirty-three high-intensity intermittent-trained athletes completed two 30-s Wingate anaerobic test sessions, 3 × 30-s (WAnT 1-3) and 1 × 30-s (WAnT 4), on a cycling ergometer. WAnT 1-3 and WAnT 4 were separated by a randomly assigned 24-min recovery intervention selected from among blood-flow restriction, passive rest, placebo stimulation, or neuromuscular electrical-stimulation-induced blood flow. Calf arterial inflow was measured by venous occlusion plethysmography at regular intervals throughout the recovery period. Performance was measured in terms of peak and mean power output during WAnT 1 and WAnT 4. After the recovery interventions, a large (r = .68 [90% CL .42; .83]) and very large (r = .72 (90% CL .49; .86]) positive correlation were observed between the change in calf arterial inflow and the change in mean and peak power output, respectively. Calf arterial inflow was significantly higher during the neuromuscular-electrical-stimulation recovery intervention than with the blood-flow-restriction, passive-rest, and placebo-stimulation interventions (P < .001). This corresponds to the only intervention that allowed performance recovery (P > .05). No recovery effect was linked to heart rate or blood lactate concentration levels. For the first time, these data support the existence of a positive correlation between an increase in blood flow and performance recovery between bouts of high-intensity exercise. As a practical consideration, this effect can be obtained by using neuromuscular electrical stimulation-induced blood flow since this passive, simple strategy could be easily applied during short-term recovery.

  17. Effects of 4 weeks of low-load unilateral resistance training, with and without blood flow restriction, on strength, thickness, V wave, and H reflex of the soleus muscle in men.

    PubMed

    Colomer-Poveda, David; Romero-Arenas, Salvador; Vera-Ibáñez, Antonio; Viñuela-García, Manuel; Márquez, Gonzalo

    2017-07-01

    To test the effects of 4 weeks of unilateral low-load resistance training (LLRT), with and without blood flow restriction (BFR), on maximal voluntary contraction (MVC), muscle thickness, volitional wave (V wave), and Hoffmann reflex (H reflex) of the soleus muscle. Twenty-two males were randomly distributed into three groups: a control group (CTR; n = 8); a low-load blood flow restriction resistance training group (BFR-LLRT; n = 7), who were an inflatable cuff to occlude blood flow; and a low-load resistance training group without blood flow restriction (LLRT; n = 7). The training consisted of four sets of unilateral isometric LLRT (25% of MVC) three times a week over 4 weeks. MVC increased 33% (P < 0.001) and 22% (P < 0.01) in the trained leg of both BFR-LLRT and LLRT groups, respectively. The soleus thickness increased 9.5% (P < 0.001) and 6.5% (P < 0.01) in the trained leg of both BFR-LLRT and LLRT groups, respectively. However, neither MVC nor thickness changed in either of the legs tested in the CTR group (MVC -1 and -5%, and muscle thickness 1.9 and 1.2%, for the control and trained leg, respectively). Moreover, V wave and H reflex did not change significantly in all the groups studied (V wave /M wave ratio -7.9 and -2.6%, and H max /M max ratio -3.8 and -4%, for the control and trained leg, respectively). Collectively, the present data suggest that in spite of the changes occurring in soleus strength and thickness, 4 weeks of low-load resistance training, with or without BFR, does not cause any change in neural drive or motoneuronal excitability.

  18. Acute resistance exercise with blood flow restriction in elderly hypertensive women: haemodynamic, rating of perceived exertion and blood lactate.

    PubMed

    Pinto, Roberta R; Karabulut, Murat; Poton, Roberto; Polito, Marcos D

    2018-01-01

    This study aimed to compare haemodynamic, rating of perceived exertion and blood lactate responses during resistance exercise with blood flow restriction (BFR) compared with traditional high-intensity resistance exercise in hypertensive older women. Eighteen hypertensive women (age = 67·0 ± 1·7 years.) undertook three random sessions: (i) three sets; 10 repetitions; 20% of one repetition maximum (1RM) with BFR; (ii) three sets; 10 repetitions; 65% of 1RM; without BFR; and (iii) no-exercise with BFR. The exercise sessions were performed on knee extension equipment. Systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), stroke volume (SV) and cardiac output (CO) were significantly higher (P<0·05) in all sets of exercise sessions than the control. No statistically significant differences were detected between exercise sessions. However, SBP, DBP and systemic vascular resistance were higher (P<0·05) and SV and CO were lower (P<0·05) during the rest intervals in the session with BFR. The perceived exertion was significantly higher (P<0·01) in the 1st (4·8 ± 0·4 versus 3·1 ± 0·3), 2nd (7·3 ± 0·4 versus 5·7 ± 0·4) and 3rd sets (8·6 ± 0·5 versus 7·5 ± 0·4) of the traditional high-intensity resistance exercise compared with the exercise with BFR. Blood lactate was higher (P<0·05) in the traditional high-intensity resistance exercise (6·2 ± 0·7 mmol) than in the exercise with BFR (4·5 ± 0·4 mmol). In comparison with high-intensity resistance exercise, low-intensity resistance exercise with BFR can elicit: (i) same haemodynamic values during exercise; (ii) lower rating of perceived exertion; (iii) lower blood lactate; (iv) higher haemodynamic demand during the rest intervals. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  19. [THE STATE OF HEPATIC AND SPLANCHNIC BLOOD FLOW IN VARIOUS TYPES OF COMPLICATED PANCREATIC PSEUDOCYSTS].

    PubMed

    Kryvoruchko, I A; Goncharova, N M; Andreyeshchev, S A; Yavorska, T P

    2015-05-01

    Investigations were conducted in 37 patients, suffering complicated pancreatic pseudocysts. In accordance to data of ultrasound Doppler flowmetry for the blood flow along portal vein, a. hepatis communis, a. mesenterica superior in complicated pancreatic pseudocysts compensatory--adaptive reactions on level of hepatic--spanchnic blood flow are directed towards restriction of the blood inflow through the portal vein system. This is accompanied by the common peripheral vascular resistence raising in basin of a. mesenterica superior, which have depended upon the patients' state severity, caused by reduction of the volume blood flow in a certan vascular collector. The oxygen debt of the liver in these patients is compensated by the volume blood flow enhancement along a. hepatis communis.

  20. The Effects of Supplementary Low-Load Blood Flow Restriction Training on Morphological and Performance-Based Adaptations in Team Sport Athletes.

    PubMed

    Scott, Brendan R; Peiffer, Jeremiah J; Goods, Paul S R

    2017-08-01

    Scott, BR, Peiffer, JJ, and Goods, PSR. The effects of supplementary low-load blood flow restriction training on morphological and performance-based adaptations in team sport athletes. J Strength Cond Res 31(8): 2147-2154, 2017-Low-load resistance training with blood flow restriction (BFR) may be a method to enhance muscular development even in trained athletes. This study aimed to assess whether supplemental low-load BFR training can improve muscle size, strength, and physical performance characteristics in team sport athletes. Twenty-one semiprofessional Australian football athletes were assessed for 3-repetition maximum (3RM) and muscular endurance in the back squat, vastus lateralis muscle architecture, and performance in sprint and vertical jump tasks. Participants then undertook a 5-week training program, consisting of normal high-load resistance training supplemented by low-load squats with (LLBFR) or without (LL) BFR. Participants also performed regular conditioning and football training during this period. After the training intervention, participants again completed the pretraining testing battery. Squat 3RM and endurance increased from pretraining levels in both LL (3RM = 12.5% increase; endurance = 24.1% increase; p ≤ 0.007) and LLBFR (3RM = 12.3% increase; endurance = 21.2% increase; p = 0.007) groups, though there were no between-group differences. No post-training changes were observed for muscle architecture, or performance in sprinting and jumping tasks. Although squat 3RM and endurance performance increased in both groups, adding BFR during supplemental exercise did not enhance these responses. Similarly, there were no large differences in the assessments of sprint, acceleration, and jumping performance between the groups after training. These findings suggest that although LLBFR did not negatively affect adaptive responses to resistance training, this training strategy may not provide added benefit for healthy Australian football athletes

  1. Blood flow restriction attenuates eccentric exercise-induced muscle damage without perceptual and cardiovascular overload.

    PubMed

    Curty, Victor M; Melo, Alexandre B; Caldas, Leonardo C; Guimarães-Ferreira, Lucas; de Sousa, Nuno F; Vassallo, Paula F; Vasquez, Elisardo C; Barauna, Valério G

    2018-05-01

    The aim of this study was to evaluate the acute effects of high-intensity eccentric exercise (HI-ECC) combined with blood flow restriction (BFR) on muscle damage markers, and perceptual and cardiovascular responses. Nine healthy men (26 ± 1 years, BMI 24 ± 1 kg m - ²) underwent unilateral elbow extension in two conditions: without (HI-ECC) and with BFR (HI-ECC+BFR). The HI-ECC protocol corresponded to three sets of 10 repetitions with 130% of maximal strength (1RM). The ratings of perceived exertion (RPE) and pain (RPP) were measured after each set. Muscle damage was evaluated by range of motion (ROM), upper arm circumference (CIR) and muscle soreness using a visual analogue scale at different moments (pre-exercise, immediately after, 24 and 48 h postexercise). Systolic (SBP), diastolic (DBP), mean blood pressure (MBP) and heart rate (HR) were measured before exercise and after each set. RPP was higher in HI-ECC+BFR than in HI-ECC after each set. Range of motion decreased postexercise in both conditions; however, in HI-ECC+BFR group, it returned to pre-exercise condition earlier (post-24 h) than HI-ECC (post-48 h). CIR increased only in HI-ECC, while no difference was observed in HI-ECC+BFR condition. Regarding cardiovascular responses, MBP and SBP did not change at any moment. HR showed similar increases in both conditions during exercise while DBP decreased only in HI-ECC condition. Thus, BFR attenuated HI-ECC-induced muscle damage and there was no increase in cardiovascular responses. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  2. Short-term low-intensity blood flow restricted interval training improves both aerobic fitness and muscle strength.

    PubMed

    de Oliveira, M F M; Caputo, F; Corvino, R B; Denadai, B S

    2016-09-01

    The present study aimed to analyze and compare the effects of four different interval-training protocols on aerobic fitness and muscle strength. Thirty-seven subjects (23.8 ± 4 years; 171.7 ± 9.5 cm; 70 ± 11 kg) were assigned to one of four groups: low-intensity interval training with (BFR, n = 10) or without (LOW, n = 7) blood flow restriction, high-intensity interval training (HIT, n = 10), and combined HIT and BFR (BFR + HIT, n = 10, every session performed 50% as BFR and 50% as HIT). Before and after 4 weeks training (3 days a week), the maximal oxygen uptake (VO2max ), maximal power output (Pmax ), onset blood lactate accumulation (OBLA), and muscle strength were measured for all subjects. All training groups were able to improve OBLA (BFR, 16%; HIT, 25%; HIT + BFR, 22%; LOW, 6%), with no difference between groups. However, VO2max and Pmax improved only for BFR (6%, 12%), HIT (9%, 15%) and HIT + BFR (6%, 11%), with no difference between groups. Muscle strength gains were only observed after BFR training (11%). This study demonstrates the advantage of short-term low-intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  3. Effects of Blood-Flow Restriction Combined With Postactivation Potentiation Stimuli on Jump Performance in Recreationally Active Men.

    PubMed

    Miller, Ryan M; Keeter, Victoria M; Freitas, Eduardo D S; Heishman, Aaron D; Knehans, Allen W; Bemben, Debra A; Bemben, Michael G

    2018-07-01

    Miller, RM, Keeter, VM, Freitas, EDS, Heishman, AD, Knehans, AW, Bemben, DA, and Bemben, MG. Effects of blood-flow restriction combined with postactivation potentiation stimuli on jump performance in recreationally active men. J Strength Cond Res 32(7): 1869-1874, 2018-Whole-body vibration (WBV) and maximum voluntary contractions (MVCs) combined with blood-flow restriction (BFR) to augment postactivation potentiation have yet to be examined. Therefore, the purpose of this investigation was to examine the augmented effects of postactivation potentiation when WBV and MVC are combined with BFR. Twenty men (21.8 ± 2.6 years, 180.5 ± 6.2 cm and 84.5 ± 12.1 kg) completed the study. Participants completed 3 testing sessions in a randomized design that included one of the following: (a) control (CON), (b) WBV and WBV combined with BFR (WBV + BFR), or (c) MVC and MVC combined with BFR (MVC + BFR). Jump height and power were recorded for 3 trials, PRE and POST jump height (cm) mean ± SD for each were as follows: CON 58.9 ± 8.6 and 57.9 ± 8.6, WBV 58.2 ± 8.1 and 59.9 ± 8.1, WBV + BFR 58.7 ± 7.6 and 60.2 ± 8.1, MVC 59.7 ± 7.4 and 60.2 ± 8.6, and MVC + BFR 57.7 ± 7.9 and 59.4 ± 8.1. PRE and POST jump power (W) mean ± SD for each were as follows: CON 1,224.3 ± 221.5 and 1,234.3 ± 189.2, WBV 1,251.1 ± 230.4 and 1,266.1 ± 215.7, WBV + BFR 1,265.8 ± 207.9 and 1,259 ± 223.3, MVC 1,264.7 ± 211.9 and 1,263.5 ± 236.5, and MVC + BFR 1,252.3 ± 222.0 and 1,294.6 ± 256.6. Significant differences were revealed in jump height between the 5 interventions (p < 0.01), WBV (p < 0.01), WBV + BFR (p < 0.01), and MVC + BFR (p < 0.01) revealed significant differences in time but no differences in jump power. In conclusion, the results of this study indicate that WBV, WBV + BFR, and MVC + BFR significantly improve jump height and time in air but not jump power.

  4. Exercise intensity and muscle hypertrophy in blood flow-restricted limbs and non-restricted muscles: a brief review.

    PubMed

    Abe, Takashi; Loenneke, Jeremy P; Fahs, Christopher A; Rossow, Lindy M; Thiebaud, Robert S; Bemben, Michael G

    2012-07-01

    Although evidence for high-intensity resistance training-induced muscle hypertrophy has accumulated over the last several decades, the basic concept of the training can be traced back to ancient Greece: Milo of Croton lifted a bull-calf daily until it was fully grown, which would be known today as progressive overload. Now, in the 21st century, different types of training are being tested and studied, such as low-intensity exercise combined with arterial as well as venous blood flow restriction (BFR) to/from the working muscles. Because BFR training requires the use of a cuff that is placed at the proximal ends of the arms and/or legs, the BFR is only applicable to limb muscles. Consequently, most previous BFR training studies have focused on the physiological adaptations of BFR limb muscles. Muscle adaptations in non-BFR muscles of the hip and trunk are lesser known. Recent studies that have reported both limb and trunk muscle adaptations following BFR exercise training suggest that low-intensity (20-30% of 1RM) resistance training combined with BFR elicits muscle hypertrophy in both BFR limb and non-BFR muscles. However, the combination of leg muscle BFR with walk training elicits muscle hypertrophy only in the BFR leg muscles. In contrast to resistance exercise with BFR, the exercise intensity may be too low during BFR walk training to cause muscle hypertrophy in the non-BFR gluteus maximus and other trunk muscles. Other mechanisms including hypoxia, local and systemic growth factors and muscle cell swelling may also potentially affect the hypertrophic response of non-BFR muscles to BFR resistance exercise. © 2012 The Authors Clinical Physiology and Functional Imaging © 2012 Scandinavian Society of Clinical Physiology and Nuclear Medicine.

  5. Blood flow restricted resistance training in older adults at risk of mobility limitations.

    PubMed

    Cook, Summer B; LaRoche, Dain P; Villa, Michelle R; Barile, Hannah; Manini, Todd M

    2017-12-01

    High-load resistance training (HL) may be contraindicated in older adults due to pre-existing health conditions (e.g. osteoarthritis). Low-load blood flow restricted (BFR) resistance training offers an alternative to HL with potentially similar strength improvement. To compare muscle strength, cross-sectional area (CSA), physical function, and quality of life (QOL) following 12-weeks of HL or BFR training in older adults at risk of mobility limitations. Thirty-six males and females (mean: 75.6years 95% confidence interval: [73.4-78.5], 1.67m [1.64-1.70], 74.3kg [69.8-78.8]) were randomly assigned to HL (70% of one repetition maximum [1-RM]) or low-load BFR (30% 1-RM coupled with a vascular restriction) exercise for the knee extensors and flexors twice per week for 12weeks. A control (CON) group performed light upper body resistance and flexibility training. Muscle strength, CSA of the quadriceps, 400-m walking speed, Short Physical Performance Battery (SPPB), and QOL were assessed before, midway and after training. Within 6-weeks of HL training, increases in all strength measures and CSA were evident and the gains were significantly greater than the CON group (P<0.05). The BFR group had strength increases in leg extension and leg press 1-RM tests, but were significantly lower in leg extension isometric maximum voluntary contraction (MVC) and leg extension 1-RM than the HL group (P<0.01). At 12-weeks HL and BFR training did not differ in MVC (P=0.14). Walking speed increased 4% among all training groups (P<0.01) and no changes were observed for overall SPPB score and QOL (P>0.05). Both training programs resulted in muscle CSA improvements and HL training had more pronounced strength gains than BFR training after 6-weeks and were more similar to BFR after 12-weeks of training. These changes in both groups did not transfer to improvements in QOL, SPPB, and walking speed. Since both programs result in strength and CSA gains, albeit at different rates, future research

  6. Cellular and physiological mechanisms underlying blood flow regulation in the retina choroid in health disease

    PubMed Central

    Kur, Joanna; Newman, Eric A.; Chan-Ling, Tailoi

    2012-01-01

    We review the cellular and physiological mechanisms responsible for the regulation of blood flow in the retina and choroid in health and disease. Due to the intrinsic light sensitivity of the retina and the direct visual accessibility of fundus blood vessels, the eye offers unique opportunities for the non-invasive investigation of mechanisms of blood flow regulation. The ability of the retinal vasculature to regulate its blood flow is contrasted with the far more restricted ability of the choroidal circulation to regulate its blood flow by virtue of the absence of glial cells, the markedly reduced pericyte ensheathment of the choroidal vasculature, and the lack of intermediate filaments in choroidal pericytes. We review the cellular and molecular components of the neurovascular unit in the retina and choroid, techniques for monitoring retinal and choroidal blood flow, responses of the retinal and choroidal circulation to light stimulation, the role of capillaries, astrocytes and pericytes in regulating blood flow, putative signaling mechanisms mediating neurovascular coupling in the retina, and changes that occur in the retinal and choroidal circulation during diabetic retinopathy, age-related macular degeneration, glaucoma, and Alzheimer's disease. We close by discussing issues that remain to be explored. PMID:22580107

  7. Blood flow

    NASA Technical Reports Server (NTRS)

    Jones, R. T.

    1976-01-01

    A heuristic treatment of blood flow in the heart and the aorta together with some of the main branches considers the effects of fluid viscosity and vessel elasticity as well as pressure distribution in the typical pulsating flow.

  8. Low birth weight in response to salt restriction during pregnancy is not due to alterations in uterine-placental blood flow or the placental and peripheral renin-angiotensin system.

    PubMed

    Leandro, Sandra Márcia; Furukawa, Luzia Naôko Shinohara; Shimizu, Maria Heloisa Massola; Casarini, Dulce Elena; Seguro, Antonio Carlos; Patriarca, Giuliana; Coelho, Michella Soares; Dolnikoff, Miriam Sterman; Heimann, Joel Claudio

    2008-09-03

    A number of studies conducted in humans and in animals have observed that events occurring early in life are associated with the development of diseases in adulthood. Salt overload and restriction during pregnancy and lactation are responsible for functional (hemodynamic and hormonal) and structural alterations in adult offspring. Our group observed that lower birth weight and insulin resistance in adulthood is associated with salt restriction during pregnancy. On the other hand, perinatal salt overload is associated with higher blood pressure and higher renal angiotensin II content in adult offspring. Therefore, we hypothesised that renin-angiotensin system (RAS) function is altered by changes in sodium intake during pregnancy. Such changes may influence fetoplacental blood flow and thereby fetal nutrient supply, with effects on growth in utero and, consequently, on birth weight. Female Wistar rats were fed low-salt (LS), normal-salt (NS), or high-salt (HS) diet, starting before conception and continuing until day 19 of pregnancy. Blood pressure, heart rate, fetuses and dams' body weight, placentae weight and litter size were measured on day 19 of pregnancy. Cardiac output, uterine and placental blood flow were also determined on day 19. Expressions of renin-angiotensin system components and of the TNF-alpha gene were evaluated in the placentae. Plasma renin activity (PRA) and plasma and tissue angiotensin-converting enzyme (ACE) activity, as well as plasma and placental levels of angiotensins I, II, and 1-7 were measured. Body weight and kidney mass were greater in HS than in NS and LS dams. Food intake did not differ among the maternal groups. Placental weight was lower in LS dams than in NS and HS dams. Fetal weight was lower in the LS group than in the NS and HS groups. The PRA was greater in LS dams than in NS and HS dams, although ACE activity (serum, cardiac, renal, and placental) was unaffected by the level of sodium intake. Placental levels of

  9. Impact of chronic hypoxemia on blood flow to the brain, heart, and adrenal gland in the late-gestation IUGR sheep fetus.

    PubMed

    Poudel, Rajan; McMillen, I Caroline; Dunn, Stacey L; Zhang, Song; Morrison, Janna L

    2015-02-01

    In the fetus, there is a redistribution of cardiac output in response to acute hypoxemia, to maintain perfusion of key organs, including the brain, heart, and adrenal glands. There may be a similar redistribution of cardiac output in the chronically hypoxemic, intrauterine growth-restricted fetus. Surgical removal of uterine caruncles in nonpregnant ewe results in the restriction of placental growth (PR) and intrauterine growth. Vascular catheters were implanted in seven control and six PR fetal sheep, and blood flow to organs was determined using microspheres. Placental and fetal weight was significantly reduced in the PR group. Despite an increase in the relative brain weight in the PR group, there was no difference in blood flow to the brain between the groups, although PR fetuses had higher blood flow to the temporal lobe. Adrenal blood flow was significantly higher in PR fetuses, and there was a direct relationship between mean gestational PaO2 and blood flow to the adrenal gland. There was no change in blood flow, but a decrease in oxygen and glucose delivery to the heart in the PR fetuses. In another group, there was a decrease in femoral artery blood flow in the PR compared with the Control group, and this may support blood flow changes to the adrenal and temporal lobe. In contrast to the response to acute hypoxemia, these data show that there is a redistribution of blood flow to the adrenals and temporal lobe, but not the heart or whole brain, in chronically hypoxemic PR fetuses in late gestation. Copyright © 2015 the American Physiological Society.

  10. Blood flow and blood cell interactions and migration in microvessels

    NASA Astrophysics Data System (ADS)

    Fedosov, Dmitry; Fornleitner, Julia; Gompper, Gerhard

    2011-11-01

    Blood flow in microcirculation plays a fundamental role in a wide range of physiological processes and pathologies in the organism. To understand and, if necessary, manipulate the course of these processes it is essential to investigate blood flow under realistic conditions including deformability of blood cells, their interactions, and behavior in the complex microvascular network which is characteristic for the microcirculation. We employ the Dissipative Particle Dynamics method to model blood as a suspension of deformable cells represented by a viscoelastic spring-network which incorporates appropriate mechanical and rheological cell-membrane properties. Blood flow is investigated in idealized geometries. In particular, migration of blood cells and their distribution in blood flow are studied with respect to various conditions such as hematocrit, flow rate, red blood cell aggregation. Physical mechanisms which govern cell migration in microcirculation and, in particular, margination of white blood cells towards the vessel wall, will be discussed. In addition, we characterize blood flow dynamics and quantify hemodynamic resistance. D.F. acknowledges the Humboldt Foundation for financial support.

  11. Pressure-driven occlusive flow of a confined red blood cell.

    PubMed

    Savin, Thierry; Bandi, M M; Mahadevan, L

    2016-01-14

    When red blood cells (RBCs) move through narrow capillaries in the microcirculation, they deform as they flow. In pathophysiological processes such as sickle cell disease and malaria, RBC motion and flow are severely restricted. To understand this threshold of occlusion, we use a combination of experiment and theory to study the motion of a single swollen RBC through a narrow glass capillary of varying inner diameter. By tracking the movement of the squeezed cell as it is driven by a controlled pressure drop, we measure the RBC velocity as a function of the pressure gradient as well as the local capillary diameter, and find that the effective blood viscosity in this regime increases with both decreasing RBC velocity and tube radius by following a power-law that depends upon the length of the confined cell. Our observations are consistent with a simple elasto-hydrodynamic model and highlight the role of lateral confinement in the occluded pressure-driven slow flow of soft confined objects.

  12. A Computational Model of the Fetal Circulation to Quantify Blood Redistribution in Intrauterine Growth Restriction

    PubMed Central

    Garcia-Canadilla, Patricia; Rudenick, Paula A.; Crispi, Fatima; Cruz-Lemini, Monica; Palau, Georgina; Camara, Oscar; Gratacos, Eduard; Bijens, Bart H.

    2014-01-01

    Intrauterine growth restriction (IUGR) due to placental insufficiency is associated with blood flow redistribution in order to maintain delivery of oxygenated blood to the brain. Given that, in the fetus the aortic isthmus (AoI) is a key arterial connection between the cerebral and placental circulations, quantifying AoI blood flow has been proposed to assess this brain sparing effect in clinical practice. While numerous clinical studies have studied this parameter, fundamental understanding of its determinant factors and its quantitative relation with other aspects of haemodynamic remodeling has been limited. Computational models of the cardiovascular circulation have been proposed for exactly this purpose since they allow both for studying the contributions from isolated parameters as well as estimating properties that cannot be directly assessed from clinical measurements. Therefore, a computational model of the fetal circulation was developed, including the key elements related to fetal blood redistribution and using measured cardiac outflow profiles to allow personalization. The model was first calibrated using patient-specific Doppler data from a healthy fetus. Next, in order to understand the contributions of the main parameters determining blood redistribution, AoI and middle cerebral artery (MCA) flow changes were studied by variation of cerebral and peripheral-placental resistances. Finally, to study how this affects an individual fetus, the model was fitted to three IUGR cases with different degrees of severity. In conclusion, the proposed computational model provides a good approximation to assess blood flow changes in the fetal circulation. The results support that while MCA flow is mainly determined by a fall in brain resistance, the AoI is influenced by a balance between increased peripheral-placental and decreased cerebral resistances. Personalizing the model allows for quantifying the balance between cerebral and peripheral-placental remodeling

  13. Effects of Blood Flow and/or Ventilation Restriction on Radiofrequency Coagulation Size in the Lung: An Experimental Study in Swine

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Anai, Hiroshi; Uchida, Barry T.; Pavcnik, Dusan, E-mail: pavcnikd@ohsu.edu

    2006-10-15

    The purpose of this study was to investigate how the restriction of blood flow and/or ventilation affects the radiofrequency (RF) ablation coagulation size in lung parenchyma. Thirty-one RF ablations were done in 16 normal lungs of 8 living swine with 2-cm LeVeen needles. Eight RF ablations were performed as a control (group G1), eight with balloon occlusion of the ipsilateral mainstem bronchus (G2), eight with occlusion of the ipsilateral pulmonary artery (G3), and seven with occlusion of both the ipsilateral bronchus and pulmonary artery (G4). Coagulation diameters and volumes of each ablation zone were compared on computed tomography (CT) andmore » gross specimen examinations. Twenty-six coagulation zones were suitable for evaluation: eight in G1, five in G2, seven in G3, and six in G4 groups. In G1, the mean coagulation diameter was 21.5 {+-} 3.5 mm on CT and 19.5 {+-} 1.78 mm on gross specimen examination. In G2, the mean diameters were 26.5 {+-} 5.1 mm and 23.0 {+-} 2.7 mm on CT and gross specimen examination, respectively. In G3, the mean diameters were 29.4 {+-} 2.2 mm and 27.4 {+-} 2.9 mm on CT and gross specimen examination, respectively, and in G4, they were 32.6 {+-} 3.33 mm and 28.8 {+-} 2.6 mm, respectively. The mean coagulation volumes were 3.39 {+-} l.52 cm{sup 3} on CT and 3.01 {+-} 0.94 cm{sup 3} on gross examinations in G1, 6.56 {+-} 2.47 cm{sup 3} and 5.22 {+-} 0.85 cm{sup 3} in G2, 10.93 {+-} 2.17 cm{sup 3} and 9.97 {+-} 2.91 cm{sup 3} in G3, and 13.81 {+-} 3.03 cm{sup 3} and 11.06 {+-} 3.27 cm{sup 3} in G4, respectively. The mean coagulation diameters on gross examination and mean coagulation volumes on CT and gross examination with G3 and G4 were significantly larger than those in G1 (p < 0.0001, p < 0.0001, p < 0.0001, respectively) or in G2 (p < 0.05, p < 0.005, p < 0.005, respectively). Pulmonary collapse occurred in one lung in G2 and pulmonary artery thrombus in two lungs of G3 and two lungs of G4. The coagulation size of RF ablation

  14. Effects of dorzolamide on choroidal blood flow, ciliary blood flow, and aqueous production in rabbits.

    PubMed

    Reitsamer, Herbert A; Bogner, Barbara; Tockner, Birgit; Kiel, Jeffrey W

    2009-05-01

    To determine the effects of topical dorzolamide (a carbonic anhydrase inhibitor) on choroidal and ciliary blood flow and the relationship between ciliary blood flow and aqueous flow. The experiments were performed in four groups of pentobarbital-anesthetized rabbits treated with topical dorzolamide (2%, 50 microL). In all groups, intraocular pressure (IOP) and mean arterial pressure (MAP) at the eye level were measured continuously by direct cannulation. In group 1, aqueous flow was measured by fluorophotometry before and after dorzolamide treatment. In group 2, aqueous flow was measured after dorzolamide at normal MAP and while MAP was held constant at 80, 55, or 40 mm Hg with occluders on the aorta and vena cava. In group 3, the same MAP levels were used, and ciliary blood flow was measured transsclerally by laser Doppler flowmetry (LDF). In group 4, choroidal blood flow was measured by LDF with the probe tip positioned in the vitreous over the posterior pole during ramp increases and decreases in MAP before and after dorzolamide. Dorzolamide lowered IOP by 19% (P < 0.01) and aqueous flow by 17% (P < 0.01), and increased ciliary blood flow by 18% (P < 0.01), which was associated with a significant reduction in ciliary vasculature resistance (-7%, P < 0.01). Dorzolamide shifted the relationship between ciliary blood flow and aqueous flow downward relative to the previously determined control relationship in the rabbit. Dorzolamide did not alter choroidal blood flow, choroidal vascular resistance, or the choroidal pressure flow relationship. Acute topical dorzolamide is a ciliary vasodilator and has a direct inhibitory effect on aqueous production, but it does not have a detectable effect on choroidal hemodynamics at the posterior pole in the rabbit.

  15. Disorders of cochlear blood flow.

    PubMed

    Nakashima, Tsutomu; Naganawa, Shinji; Sone, Michihiko; Tominaga, Mitsuo; Hayashi, Hideo; Yamamoto, Hiroshi; Liu, Xiuli; Nuttall, Alfred L

    2003-09-01

    The cochlea is principally supplied from the inner ear artery (labyrinthine artery), which is usually a branch of the anterior inferior cerebellar artery. Cochlear blood flow is a function of cochlear perfusion pressure, which is calculated as the difference between mean arterial blood pressure and inner ear fluid pressure. Many otologic disorders such as noise-induced hearing loss, endolymphatic hydrops and presbycusis are suspected of being related to alterations in cochlear blood flow. However, the human cochlea is not easily accessible for investigation because this delicate sensory organ is hidden deep in the temporal bone. In patients with sensorineural hearing loss, magnetic resonance imaging, laser-Doppler flowmetry and ultrasonography have been used to investigate the status of cochlear blood flow. There have been many reports of hearing loss that were considered to be caused by blood flow disturbance in the cochlea. However, direct evidence of blood flow disturbance in the cochlea is still lacking in most of the cases.

  16. Regulation of coronary blood flow

    PubMed Central

    Gorlin, Richard

    1971-01-01

    Coronary blood flow is dependent upon arterial pressure, diastolic time, and small vessel resistance. The system is regulated to achieve a low flow high oxygen extraction and low myocardial Po2. This setting is sensitive to change in oxygen needs. Regulation of blood flow occurs primarily through local intrinsic regulation, most likely through production of vasodilating metabolites in response to minimal degrees of ischaemia. Local regulation appears to dominate over remote regulation in most circumstances. Blood flow distribution to the myocardium is depth dependent as well as regional in variation. Both types of distribution of blood flow are profoundly disturbed in the presence of obstructive coronary atherosclerosis. This results in either concentric myocardial shells or patchy transmural zones of selective ischaemia with clear-cut but local abnormalities in metabolism and performance. Images PMID:4929442

  17. Non-invasive pulmonary blood flow analysis and blood pressure mapping derived from 4D flow MRI

    NASA Astrophysics Data System (ADS)

    Delles, Michael; Rengier, Fabian; Azad, Yoo-Jin; Bodenstedt, Sebastian; von Tengg-Kobligk, Hendrik; Ley, Sebastian; Unterhinninghofen, Roland; Kauczor, Hans-Ulrich; Dillmann, Rüdiger

    2015-03-01

    In diagnostics and therapy control of cardiovascular diseases, detailed knowledge about the patient-specific behavior of blood flow and pressure can be essential. The only method capable of measuring complete time-resolved three-dimensional vector fields of the blood flow velocities is velocity-encoded magnetic resonance imaging (MRI), often denoted as 4D flow MRI. Furthermore, relative pressure maps can be computed from this data source, as presented by different groups in recent years. Hence, analysis of blood flow and pressure using 4D flow MRI can be a valuable technique in management of cardiovascular diseases. In order to perform these tasks, all necessary steps in the corresponding process chain can be carried out in our in-house developed software framework MEDIFRAME. In this article, we apply MEDIFRAME for a study of hemodynamics in the pulmonary arteries of five healthy volunteers. The study included measuring vector fields of blood flow velocities by phase-contrast MRI and subsequently computing relative blood pressure maps. We visualized blood flow by streamline depictions and computed characteristic values for the left and the right pulmonary artery (LPA and RPA). In all volunteers, we observed a lower amount of blood flow in the LPA compared to the RPA. Furthermore, we visualized blood pressure maps using volume rendering and generated graphs of pressure differences between the LPA, the RPA and the main pulmonary artery. In most volunteers, blood pressure was increased near to the bifurcation and in the proximal LPA, leading to higher average pressure values in the LPA compared to the RPA.

  18. Acute effect of glucose on cerebral blood flow, blood oxygenation, and oxidative metabolism.

    PubMed

    Xu, Feng; Liu, Peiying; Pascual, Juan M; Xiao, Guanghua; Huang, Hao; Lu, Hanzhang

    2015-02-01

    While it is known that specific nuclei of the brain, for example hypothalamus, contain glucose-sensing neurons thus their activity is affected by blood glucose level, the effect of glucose modulation on whole-brain metabolism is not completely understood. Several recent reports have elucidated the long-term impact of caloric restriction on the brain, showing that animals under caloric restriction had enhanced rate of tricarboxylic acid cycle (TCA) cycle flux accompanied by extended life span. However, acute effect of postprandial blood glucose increase has not been addressed in detail, partly due to a scarcity and complexity of measurement techniques. In this study, using a recently developed noninvasive MR technique, we measured dynamic changes in global cerebral metabolic rate of O2 (CMRO2 ) following a 50 g glucose ingestion (N = 10). A time dependent decrease in CMRO2 was observed, which was accompanied by a reduction in oxygen extraction fraction (OEF) with unaltered cerebral blood flow (CBF). At 40 min post-ingestion, the amount of CMRO2 reduction was 7.8 ± 1.6%. A control study without glucose ingestion was performed (N = 10), which revealed no changes in CMRO2 , CBF, or OEF, suggesting that the observations in the glucose study was not due to subject drowsiness or fatigue after staying inside the scanner. These findings suggest that ingestion of glucose may alter the rate of cerebral metabolism of oxygen in an acute setting. © 2014 Wiley Periodicals, Inc.

  19. Skin cooling on contact with cold materials: the effect of blood flow during short-term exposures.

    PubMed

    Jay, Ollie; Havenith, George

    2004-03-01

    This study investigates the effect of blood flow upon the short-term (<180 s) skin contact cooling response in order to ascertain whether sufferers of circulatory disorders, such as the vasospastic disorder Raynaud's disease, are at a greater risk of cold injury than people with a normal rate of blood flow. Eight female volunteers participated, touching blocks of stainless steel and nylon with a finger contact force of 2.9 N at a surface temperature of -5 degrees C under occluded and vasodilated conditions. Contact temperature (Tc) of the finger pad was measured over time using a T-type thermocouple. Forearm blood flow was measured using strain gauge plethysmography. Contact cooling responses were analysed by fitting a modified Newtonian cooling curve. A significant difference was found between the starting skin temperatures for the two blood flow conditions (P<0.001). However, no effect of blood flow was found upon any of the derived cooling curve parameters characterizing the skin cooling response (P>0.05). It is hypothesized that the finger contact force used (2.9 N) and the resultant pressure upon the tissue of the contact finger pad restricted the blood supply to the contact area under both blood flow conditions; therefore, no effect of blood flow was found upon the parameters describing the contact cooling response. Whilst the findings of this study are sufficient to draw a conclusion for those in a working environment, i.e. contact forces below 2.9 N will seldom be encountered, a further study will be required to ascertain conclusively whether blood flow does affect the contact cooling response at a finger contact force low enough to allow unrestricted blood flow to the finger pad. Further protocol improvements are also recommended.

  20. Endovascular blood flow measurement system

    NASA Astrophysics Data System (ADS)

    Khe, A. K.; Cherevko, A. A.; Chupakhin, A. P.; Krivoshapkin, A. L.; Orlov, K. Yu

    2016-06-01

    In this paper an endovascular measurement system used for intraoperative cerebral blood flow monitoring is described. The system is based on a Volcano ComboMap Pressure and Flow System extended with analogue-to-digital converter and PC laptop. A series of measurements performed in patients with cerebrovascular pathologies allows us to introduce “velocity-pressure” and “flow rate-energy flow rate” diagrams as important characteristics of the blood flow. The measurement system presented here can be used as an additional instrument in neurosurgery for assessment and monitoring of the operation procedure. Clinical data obtained with the system are used for construction of mathematical models and patient-specific simulations. The monitoring of the blood flow parameters during endovascular interventions was approved by the Ethics Committee at the Meshalkin Novosibirsk Research Institute of Circulation Pathology and included in certain surgical protocols for pre-, intra- and postoperative examinations.

  1. 21 CFR 870.2120 - Extravascular blood flow probe.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Extravascular blood flow probe. 870.2120 Section... blood flow probe. (a) Identification. An extravascular blood flow probe is an extravascular ultrasonic or electromagnetic probe used in conjunction with a blood flowmeter to measure blood flow in a...

  2. 21 CFR 870.2120 - Extravascular blood flow probe.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Extravascular blood flow probe. 870.2120 Section... blood flow probe. (a) Identification. An extravascular blood flow probe is an extravascular ultrasonic or electromagnetic probe used in conjunction with a blood flowmeter to measure blood flow in a...

  3. 21 CFR 870.2120 - Extravascular blood flow probe.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Extravascular blood flow probe. 870.2120 Section... blood flow probe. (a) Identification. An extravascular blood flow probe is an extravascular ultrasonic or electromagnetic probe used in conjunction with a blood flowmeter to measure blood flow in a...

  4. 21 CFR 870.2120 - Extravascular blood flow probe.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Extravascular blood flow probe. 870.2120 Section... blood flow probe. (a) Identification. An extravascular blood flow probe is an extravascular ultrasonic or electromagnetic probe used in conjunction with a blood flowmeter to measure blood flow in a...

  5. Ultrasonic Blood Flow Measurement in Haemodialysis

    PubMed Central

    Sampson, D.; Papadimitriou, M.; Kulatilake, A. E.

    1970-01-01

    A 5-megacycle Doppler flow meter, calibrated in-vitro, was found to give a linear response to blood flow in the ranges commonly encountered in haemodialysis. With this, blood flow through artificial kidneys could be measured simply and with a clinically acceptable error. The method is safe, as blood lines do not have to be punctured or disconnected and hence there is no risk of introducing infection. Besides its value as a research tool the flow meter is useful in evaluating new artificial kidneys. Suitably modified it could form the basis of an arterial flow alarm system. PMID:5416812

  6. Modified Beer-Lambert law for blood flow.

    PubMed

    Baker, Wesley B; Parthasarathy, Ashwin B; Busch, David R; Mesquita, Rickson C; Greenberg, Joel H; Yodh, A G

    2014-11-01

    We develop and validate a Modified Beer-Lambert law for blood flow based on diffuse correlation spectroscopy (DCS) measurements. The new formulation enables blood flow monitoring from temporal intensity autocorrelation function data taken at single or multiple delay-times. Consequentially, the speed of the optical blood flow measurement can be substantially increased. The scheme facilitates blood flow monitoring of highly scattering tissues in geometries wherein light propagation is diffusive or non-diffusive, and it is particularly well-suited for utilization with pressure measurement paradigms that employ differential flow signals to reduce contributions of superficial tissues.

  7. Finger blood flow in Antarctica

    PubMed Central

    Elkington, E. J.

    1968-01-01

    1. Finger blood flow was estimated, by strain-gauge plethysmography, before and during a 1 hr immersion in ice water, on twenty-five men throughout a year at Wilkes, Antarctica. A total of 121 satisfactory immersions were made. 2. Blood flow before and during immersion decreased significantly in the colder months of the year, and the increase caused by cold-induced vasodilatation (CIVD) became less as the year progressed. The time of onset, blood flow at onset, and frequency of the cycles of CIVD showed no significant relation to the coldness of the weather (as measured by mean monthly wind chill) or the time in months. Comparisons of blood flow before and after five field trips (average duration 42 days), on which cold exposure was more severe than at Wilkes station, gave similar results. 3. The results suggest that vasoconstrictor tone increased. This interpretation agrees with previous work on general acclimatization in Antarctica, but contrasts with work elsewhere on local acclimatization of the hands. PMID:5684034

  8. Modified Beer-Lambert law for blood flow

    NASA Astrophysics Data System (ADS)

    Baker, Wesley B.; Parthasarathy, Ashwin B.; Busch, David R.; Mesquita, Rickson C.; Greenberg, Joel H.; Yodh, A. G.

    2015-03-01

    The modified Beer-Lambert law is among the most widely used approaches for analysis of near-infrared spectroscopy (NIRS) reflectance signals for measurements of tissue blood volume and oxygenation. Briefly, the modified Beer-Lambert paradigm is a scheme to derive changes in tissue optical properties based on continuous-wave (CW) diffuse optical intensity measurements. In its simplest form, the scheme relates differential changes in light transmission (in any geometry) to differential changes in tissue absorption. Here we extend this paradigm to the measurement of tissue blood flow by diffuse correlation spectroscopy (DCS). In the new approach, differential changes of the intensity temporal auto-correlation function at a single delay-time are related to differential changes in blood flow. The key theoretical results for measurement of blood flow changes in any tissue geometry are derived, and we demonstrate the new method to monitor cerebral blood flow in a pig under conditions wherein the semi-infinite geometry approximation is fairly good. Specifically, the drug dinitrophenol was injected in the pig to induce a gradual 200% increase in cerebral blood flow, as measured with MRI velocity flow mapping and by DCS. The modified Beer-Lambert law for flow accurately recovered these flow changes using only a single delay-time in the intensity auto-correlation function curve. The scheme offers increased DCS measurement speed of blood flow. Further, the same techniques using the modified Beer-Lambert law to filter out superficial tissue effects in NIRS measurements of deep tissues can be applied to the DCS modified Beer-Lambert law for blood flow monitoring of deep tissues.

  9. Local Control of Blood Flow

    ERIC Educational Resources Information Center

    Clifford, Philip S.

    2011-01-01

    Organ blood flow is determined by perfusion pressure and vasomotor tone in the resistance vessels of the organ. Local factors that regulate vasomotor tone include myogenic and metabolic autoregulation, flow-mediated and conducted responses, and vasoactive substances released from red blood cells. The relative importance of each of these factors…

  10. Modified Beer-Lambert law for blood flow

    PubMed Central

    Baker, Wesley B.; Parthasarathy, Ashwin B.; Busch, David R.; Mesquita, Rickson C.; Greenberg, Joel H.; Yodh, A. G.

    2014-01-01

    We develop and validate a Modified Beer-Lambert law for blood flow based on diffuse correlation spectroscopy (DCS) measurements. The new formulation enables blood flow monitoring from temporal intensity autocorrelation function data taken at single or multiple delay-times. Consequentially, the speed of the optical blood flow measurement can be substantially increased. The scheme facilitates blood flow monitoring of highly scattering tissues in geometries wherein light propagation is diffusive or non-diffusive, and it is particularly well-suited for utilization with pressure measurement paradigms that employ differential flow signals to reduce contributions of superficial tissues. PMID:25426330

  11. Reactive hyperemia is not responsible for stimulating muscle protein synthesis following blood flow restriction exercise

    PubMed Central

    Gundermann, David M.; Fry, Christopher S.; Dickinson, Jared M.; Walker, Dillon K.; Timmerman, Kyle L.; Drummond, Micah J.; Volpi, Elena

    2012-01-01

    Blood flow restriction (BFR) to contracting skeletal muscle during low-intensity resistance exercise training increases muscle strength and size in humans. However, the mechanism(s) underlying these effects are largely unknown. We have previously shown that mammalian target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis (MPS) are stimulated following an acute bout of BFR exercise. The purpose of this study was to test the hypothesis that reactive hyperemia is the mechanism responsible for stimulating mTORC1 signaling and MPS following BFR exercise. Six young men (24 ± 2 yr) were used in a randomized crossover study consisting of two exercise trials: low-intensity resistance exercise with BFR (BFR trial) and low-intensity resistance exercise with sodium nitroprusside (SNP), a pharmacological vasodilator infusion into the femoral artery immediately after exercise to simulate the reactive hyperemia response after BFR exercise (SNP trial). Postexercise mixed-muscle fractional synthetic rate from the vastus lateralis increased by 49% in the BFR trial (P < 0.05) with no change in the SNP trial (P > 0.05). BFR exercise increased the phosphorylation of mTOR, S6 kinase 1, ribosomal protein S6, ERK1/2, and Mnk1-interacting kinase 1 (P < 0.05) with no changes in mTORC1 signaling in the SNP trial (P > 0.05). We conclude that reactive hyperemia is not a primary mechanism for BFR exercise-induced mTORC1 signaling and MPS. Further research is necessary to elucidate the cellular mechanism(s) responsible for the increase in mTOR signaling, MPS, and hypertrophy following acute and chronic BFR exercise. PMID:22362401

  12. Reactive hyperemia is not responsible for stimulating muscle protein synthesis following blood flow restriction exercise.

    PubMed

    Gundermann, David M; Fry, Christopher S; Dickinson, Jared M; Walker, Dillon K; Timmerman, Kyle L; Drummond, Micah J; Volpi, Elena; Rasmussen, Blake B

    2012-05-01

    Blood flow restriction (BFR) to contracting skeletal muscle during low-intensity resistance exercise training increases muscle strength and size in humans. However, the mechanism(s) underlying these effects are largely unknown. We have previously shown that mammalian target of rapamycin complex 1 (mTORC1) signaling and muscle protein synthesis (MPS) are stimulated following an acute bout of BFR exercise. The purpose of this study was to test the hypothesis that reactive hyperemia is the mechanism responsible for stimulating mTORC1 signaling and MPS following BFR exercise. Six young men (24 ± 2 yr) were used in a randomized crossover study consisting of two exercise trials: low-intensity resistance exercise with BFR (BFR trial) and low-intensity resistance exercise with sodium nitroprusside (SNP), a pharmacological vasodilator infusion into the femoral artery immediately after exercise to simulate the reactive hyperemia response after BFR exercise (SNP trial). Postexercise mixed-muscle fractional synthetic rate from the vastus lateralis increased by 49% in the BFR trial (P < 0.05) with no change in the SNP trial (P > 0.05). BFR exercise increased the phosphorylation of mTOR, S6 kinase 1, ribosomal protein S6, ERK1/2, and Mnk1-interacting kinase 1 (P < 0.05) with no changes in mTORC1 signaling in the SNP trial (P > 0.05). We conclude that reactive hyperemia is not a primary mechanism for BFR exercise-induced mTORC1 signaling and MPS. Further research is necessary to elucidate the cellular mechanism(s) responsible for the increase in mTOR signaling, MPS, and hypertrophy following acute and chronic BFR exercise.

  13. Noninvasive blood-flow meter using a curved cannula with zero compensation for an axial flow blood pump.

    PubMed

    Kosaka, Ryo; Fukuda, Kyohei; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

    2013-01-01

    In order to monitor the condition of a patient using a left ventricular assist system (LVAS), blood flow should be measured. However, the reliable determination of blood-flow rate has not been established. The purpose of the present study is to develop a noninvasive blood-flow meter using a curved cannula with zero compensation for an axial flow blood pump. The flow meter uses the centrifugal force generated by the flow rate in the curved cannula. Two strain gauges served as sensors. The first gauges were attached to the curved area to measure static pressure and centrifugal force, and the second gauges were attached to straight area to measure static pressure. The flow rate was determined by the differences in output from the two gauges. The zero compensation was constructed based on the consideration that the flow rate could be estimated during the initial driving condition and the ventricular suction condition without using the flow meter. A mock circulation loop was constructed in order to evaluate the measurement performance of the developed flow meter with zero compensation. As a result, the zero compensation worked effectively for the initial calibration and the zero-drift of the measured flow rate. We confirmed that the developed flow meter using a curved cannula with zero compensation was able to accurately measure the flow rate continuously and noninvasively.

  14. Blood cell interactions and segregation in flow.

    PubMed

    Munn, Lance L; Dupin, Michael M

    2008-04-01

    For more than a century, pioneering researchers have been using novel experimental and computational approaches to probe the mysteries of blood flow. Thanks to their efforts, we know that blood cells generally prefer to migrate to the axis of flow, that red and white cells segregate in flow, and that cell deformability and their tendency to reversibly aggregate contribute to the non-Newtonian nature of this unique fluid. All of these properties have beneficial physiological consequences, allowing blood to perform a variety of critical functions. Our current understanding of these unusual flow properties of blood have been made possible by the ingenuity and diligence of a number of researchers, including Harry Goldsmith, who developed novel technologies to visualize and quantify the flow of blood at the level of individual cells. Here we summarize efforts in our lab to continue this tradition and to further our understanding of how blood cells interact with each other and with the blood vessel wall.

  15. Blood Cell Interactions and Segregation in Flow

    PubMed Central

    Munn, Lance L.; Dupin, Michael M.

    2009-01-01

    For more than a century, pioneering researchers have been using novel experimental and computational approaches to probe the mysteries of blood flow. Thanks to their efforts, we know that blood cells generally prefer to migrate to the axis of flow, that red and white cells segregate in flow, and that cell deformability and their tendency to reversibly aggregate contribute to the non-Newtonian nature of this unique fluid. All of these properties have beneficial physiological consequences, allowing blood to perform a variety of critical functions. Our current understanding of these unusual flow properties of blood have been made possible by the ingenuity and diligence of a number of researchers, including Harry Goldsmith, who developed novel technologies to visualize and quantify the flow of blood at the level of individual cells. Here we summarize efforts in our lab to continue this tradition and to further our understanding of how blood cells interact with each other and with the blood vessel wall. PMID:18188702

  16. Cardiac autonomic and haemodynamic recovery after a single session of aerobic exercise with and without blood flow restriction in older adults.

    PubMed

    Ferreira, Marina Lívia Venturini; Sardeli, Amanda Veiga; Souza, Giovana Vergínia De; Bonganha, Valéria; Santos, Lucas Do Carmo; Castro, Alex; Cavaglieri, Cláudia Regina; Chacon-Mikahil, Mara Patrícia Traina

    2017-12-01

    This study investigated the autonomic and haemodynamic responses to different aerobic exercise loads, with and without blood flow restriction (BFR). In a crossover study, 21 older adults (8 males and 13 females) completed different aerobic exercise sessions: low load without BFR (LL) (40% VO 2 max ), low load with BFR (LL-BFR) (40% VO 2 max + 50% BFR) and high load without BFR (HL) (70% VO 2 max ). Heart rate variability and haemodynamic responses were recorded during rest and throughout 30 min of recovery. HL reduced R-R interval, the root mean square of successive difference of R-R intervals and high frequency during 30 min of recovery at a greater magnitude compared with LL and LL-BFR. Sympathetic-vagal balance increased the values for HL during 30 min of recovery at a greater magnitude when compared with LL and LL-BFR. Post-exercise haemodynamic showed reduced values of double product at 30 min of recovery compared to rest in LL-BFR, while HL showed higher values compared to rest, LL-BFR and LL. Reduced systolic blood pressure was observed for LL-BFR (30 min) compared to rest. Autonomic and haemodynamic responses indicate lower cardiovascular stress after LL-BFR compared to HL, being this method, besides the functional adaptations, a potential choice to attenuate the cardiovascular stress after exercise in older adults.

  17. The effect of partial portal decompression on portal blood flow and effective hepatic blood flow in man: a prospective study.

    PubMed

    Rosemurgy, A S; McAllister, E W; Godellas, C V; Goode, S E; Albrink, M H; Fabri, P J

    1995-12-01

    With the advent of transjugular intrahepatic porta-systemic stent shunt and the wider application of the surgically placed small diameter prosthetic H-graft portacaval shunt (HGPCS), partial portal decompression in the treatment of portal hypertension has received increased attention. The clinical results supporting the use of partial portal decompression are its low incidence of variceal rehemorrhage due to decreased portal pressures and its low rate of hepatic failure, possibly due to maintenance of blood flow to the liver. Surprisingly, nothing is known about changes in portal hemodynamics and effective hepatic blood flow following partial portal decompression. To prospectively evaluate changes in portal hemodynamics and effective hepatic blood flow brought about by partial portal decompression, the following were determined in seven patients undergoing HGPCS: intraoperative pre- and postshunt portal vein pressures and portal vein-inferior vena cava pressure gradients, intraoperative pre- and postshunt portal vein flow, and pre- and postoperative effective hepatic blood flow. With HGPCS, portal vein pressures and portal vein-inferior vena cava pressure gradients decreased significantly, although portal pressures remained above normal. In contrast to the significant decreases in portal pressures, portal vein blood flow and effective hepatic blood flow do not decrease significantly. Changes in portal vein pressures and portal vein-inferior vena cava pressure gradients are great when compared to changes in portal vein flow and effective hepatic blood flow. Reduction of portal hypertension with concomitant maintenance of hepatic blood flow may explain why hepatic dysfunction is avoided following partial portal decompression.

  18. Increased hippocampal blood volume and normal blood flow in schizophrenia

    PubMed Central

    Talati, Pratik; Rane, Swati; Skinner, Jack; Gore, John; Heckers, Stephan

    2015-01-01

    Neuroimaging studies have provided compelling evidence for abnormal hippocampal activity in schizophrenia. Most studies made inferences about baseline hippocampal activity using a single hemodynamic parameter (e.g., blood volume or blood flow). Here we studied several hemodynamic measures in the same cohort to test the hypothesis of increased hippocampal activity in schizophrenia. We used dynamic susceptibility contrast- (DSC-) magnetic resonance imaging to assess blood volume, blood flow, and mean transit time in the hippocampus of 15 patients with chronic schizophrenia and 15 healthy controls. Left and right hippocampal measurements were combined for absolute measures of cerebral blood volume (CBV), blood flow (CBF), and mean transit time (MTT). We found significantly increased hippocampal CBV, but normal CBF and MTT, in schizophrenia. The uncoupling of CBV and CBF could be due to several factors, including antipsychotic medication, loss of cerebral perfusion pressure, or angiogenesis. Further studies need to incorporate several complementary imaging modalities to better characterize hippocampal dysfunction in schizophrenia. PMID:25896442

  19. Effect of Intermittent Energy Restriction on Flow Mediated Dilatation, a Measure of Endothelial Function: A Short Report.

    PubMed

    Headland, Michelle L; Clifton, Peter M; Keogh, Jennifer B

    2018-06-04

    Intermittent energy restriction is a popular alternative to daily energy restriction for weight loss; however, it is unknown if endothelial function, a risk factor for cardiovascular disease, is altered by periods of severe energy restriction. The objective of the study was to determine the impact of two consecutive very low energy intake days, which is the core component of the 5:2 intermittent energy restriction diet strategy, on endothelial function compared to consecutive ad libitum eating days. The secondary objective was to explore the effects of these dietary conditions on fasting glucose concentrations. This was a 4-week randomized, single-blinded, crossover study of 35 participants. Participants consumed a very low energy diet (500 calories for women, 600 calories for men) on two consecutive days per week and 5 days of habitual eating. In weeks 3 and 4 of the trial, participants had measurements of flow mediated dilatation (FMD) and blood samples taken following either 2 habitual eating days or 2 energy restricted days in a randomized order. FMD values were not different after the two eating states (8.6% vs. 8.3%, p = 0.7). All other outcome variables were unchanged. Endothelial function, as measured by flow mediated dilatation, was not altered by two consecutive very low energy intake days. Further investigations assessing the impact in specific population groups as well as different testing conditions would be beneficial.

  20. Three-dimensional imaging of absolute blood flow velocity and blood vessel position under low blood flow velocity based on Doppler signal information included in scattered light from red blood cells

    NASA Astrophysics Data System (ADS)

    Kyoden, Tomoaki; Akiguchi, Shunsuke; Tajiri, Tomoki; Andoh, Tsugunobu; Hachiga, Tadashi

    2017-11-01

    The development of a system for in vivo visualization of occluded distal blood vessels for diabetic patients is the main target of our research. We herein describe two-beam multipoint laser Doppler velocimetry (MLDV), which measures the instantaneous multipoint flow velocity and can be used to observe the blood flow velocity in peripheral blood vessels. By including a motorized stage to shift the measurement points horizontally and in the depth direction while measuring the velocity, the path of the blood vessel in the skin could be observed using blood flow velocity in three-dimensional space. The relationship of the signal power density between the blood vessel and the surrounding tissues was shown and helped us identify the position of the blood vessel. Two-beam MLDV can be used to simultaneously determine the absolute blood flow velocity distribution and identify the blood vessel position in skin.

  1. Heterogeneity of human adipose blood flow

    PubMed Central

    Levitt, David G

    2007-01-01

    Background The long time pharmacokinetics of highly lipid soluble compounds is dominated by blood-adipose tissue exchange and depends on the magnitude and heterogeneity of adipose blood flow. Because the adipose tissue is an infinite sink at short times (hours), the kinetics must be followed for days in order to determine if the adipose perfusion is heterogeneous. The purpose of this paper is to quantitate human adipose blood flow heterogeneity and determine its importance for human pharmacokinetics. Methods The heterogeneity was determined using a physiologically based pharmacokinetic model (PBPK) to describe the 6 day volatile anesthetic data previously published by Yasuda et. al. The analysis uses the freely available software PKQuest and incorporates perfusion-ventilation mismatch and time dependent parameters that varied from the anesthetized to the ambulatory period. This heterogeneous adipose perfusion PBPK model was then tested by applying it to the previously published cannabidiol data of Ohlsson et. al. and the cannabinol data of Johansson et. al. Results The volatile anesthetic kinetics at early times have only a weak dependence on adipose blood flow while at long times the pharmacokinetics are dominated by the adipose flow and are independent of muscle blood flow. At least 2 adipose compartments with different perfusion rates (0.074 and 0.014 l/kg/min) were needed to describe the anesthetic data. This heterogeneous adipose PBPK model also provided a good fit to the cannabinol data. Conclusion Human adipose blood flow is markedly heterogeneous, varying by at least 5 fold. This heterogeneity significantly influences the long time pharmacokinetics of the volatile anesthetics and tetrahydrocannabinol. In contrast, using this same PBPK model it can be shown that the long time pharmacokinetics of the persistent lipophilic compounds (dioxins, PCBs) do not depend on adipose blood flow. The ability of the same PBPK model to describe both the anesthetic and

  2. Effects of adenosine on intraocular pressure, optic nerve head blood flow, and choroidal blood flow in healthy humans.

    PubMed

    Polska, Elzbieta; Ehrlich, Paulina; Luksch, Alexandra; Fuchsjäger-Mayrl, Gabriele; Schmetterer, Leopold

    2003-07-01

    There is evidence from a variety of animal studies that the adenosine system plays a role in the control of intraocular pressure (IOP) and ocular blood flow. However, human data on the effect of adenosine on IOP and choroidal and optic nerve blood flow are not available. The effect of stepwise increases in doses of adenosine (10, 20, and 40 micro g/kg per minute, 30 minutes per infusion step) on optic nerve head blood flow, choroidal blood flow, and IOP was determined in a placebo-controlled double-masked clinical trial in 12 healthy male volunteers. Blood flow in the optic nerve head and choroid was measured with laser Doppler flowmetry. In addition, fundus pulsation amplitude in the macula (FPAM) and the optic nerve head (FPAO) were assessed with laser interferometry. Adenosine induced a small but significant decrease in IOP (at 40 microg/kg per minute: 12% +/- 13%), which was significant versus placebo (P = 0.046). In addition, adenosine induced a significant increase in choroidal blood flow (P < 0.001) and optic nerve head blood flow (P = 0.037), and FPAM (P = 0.0014) and tended to increase FPAO (P = 0.057). At the highest administered dose, the effect on choroidal hemodynamic parameters between 14% and 17%, whereas the effect on optic nerve hemodynamic parameters was between 3% and 11%. These data are consistent with adenosine inducing choroidal and optic nerve head vasodilatation and reducing IOP in healthy humans. Considering the neuroprotective properties of adenosine described in previous animal experiments the adenosine system is an attractive target system for therapeutic approaches in glaucoma.

  3. The acute angiogenic signalling response to low-load resistance exercise with blood flow restriction.

    PubMed

    Ferguson, Richard A; Hunt, Julie E A; Lewis, Mark P; Martin, Neil R W; Player, Darren J; Stangier, Carolin; Taylor, Conor W; Turner, Mark C

    2018-04-01

    This study investigated protein kinase activation and gene expression of angiogenic factors in response to low-load resistance exercise with or without blood flow restriction (BFR). In a repeated measures cross-over design, six males performed four sets of bilateral knee extension exercise at 20% 1RM (reps per set = 30:15:15:continued to fatigue) with BFR (110 mmHg) and without (CON). Muscle biopsies were obtained from the vastus lateralis before, 2 and 4 h post-exercise. mRNA expression was determined using real-time RT-PCR. Protein phosphorylation/expression was determined using Western blot. p38MAPK phosphorylation was greater (p = 0.05) at 2 h following BFR (1.3 ± 0.8) compared to CON (0.4 ± 0.3). AMPK phosphorylation remained unchanged. PGC-1α mRNA expression increased at 2 h (5.9 ± 1.3 vs. 2.1 ± 0.8; p = 0.03) and 4 h (3.2 ± 0.8 vs. 1.5 ± 0.4; p = 0.03) following BFR exercise with no change in CON. PGC-1α protein expression did not change following either exercise. BFR exercise enhanced mRNA expression of vascular endothelial growth factor (VEGF) at 2 h (5.2 ± 2.8 vs 1.7 ± 1.1; p = .02) and 4 h (6.8 ± 4.9 vs. 2.5 ± 2.7; p = .01) compared to CON. mRNA expression of VEGF-R2 and hypoxia-inducible factor 1α increased following BFR exercise but only eNOS were enhanced relative to CON. Matrix metalloproteinase-9 mRNA expression was not altered in response to either exercise. Acute low-load resistance exercise with BFR provides a targeted angiogenic response potentially mediated through enhanced ischaemic and shear stress stimuli.

  4. Transcranial Doppler-determined change in posterior cerebral artery blood flow velocity does not reflect vertebral artery blood flow during exercise.

    PubMed

    Washio, Takuro; Sasaki, Hiroyuki; Ogoh, Shigehiko

    2017-04-01

    We examined whether a change in posterior cerebral artery flow velocity (PCAv) reflected the posterior cerebral blood flow in healthy subjects during both static and dynamic exercise. PCAv and vertebral artery (VA) blood flow, as an index of posterior cerebral blood flow, were continuously measured during an exercise trial using transcranial Doppler (TCD) ultrasonography and Doppler ultrasound, respectively. Static handgrip exercise significantly increased both PCAv and VA blood flow. Increasing intensity of dynamic exercise further increased VA blood flow from moderate exercise, while PCAv decreased to almost resting level. During both static and dynamic exercise, the PCA cerebrovascular conductance (CVC) index significantly decreased from rest (static and high-intensity dynamic exercise, -11.5 ± 12.2% and -18.0 ± 16.8%, means ± SD, respectively) despite no change in the CVC of VA. These results indicate that vasoconstriction occurred at PCA but not VA during exercise-induced hypertension. This discrepancy in vascular response to exercise between PCA and VA may be due to different cerebral arterial characteristics. Therefore, to determine the effect of exercise on posterior cerebral circulation, at least, we need to carefully consider which cerebral artery to measure, regardless of exercise mode. NEW & NOTEWORTHY We examined whether transcranial Doppler-determined flow velocity in the posterior cerebral artery can be used as an index of cerebral blood flow during exercise. However, the changes in posterior cerebral artery flow velocity during exercise do not reflect vertebral artery blood flow. Copyright © 2017 the American Physiological Society.

  5. Pancreatic islet blood flow and its measurement

    PubMed Central

    Jansson, Leif; Barbu, Andreea; Bodin, Birgitta; Drott, Carl Johan; Espes, Daniel; Gao, Xiang; Grapensparr, Liza; Källskog, Örjan; Lau, Joey; Liljebäck, Hanna; Palm, Fredrik; Quach, My; Sandberg, Monica; Strömberg, Victoria; Ullsten, Sara; Carlsson, Per-Ola

    2016-01-01

    Pancreatic islets are richly vascularized, and islet blood vessels are uniquely adapted to maintain and support the internal milieu of the islets favoring normal endocrine function. Islet blood flow is normally very high compared with that to the exocrine pancreas and is autonomously regulated through complex interactions between the nervous system, metabolites from insulin secreting β-cells, endothelium-derived mediators, and hormones. The islet blood flow is normally coupled to the needs for insulin release and is usually disturbed during glucose intolerance and overt diabetes. The present review provides a brief background on islet vascular function and especially focuses on available techniques to measure islet blood perfusion. The gold standard for islet blood flow measurements in experimental animals is the microsphere technique, and its advantages and disadvantages will be discussed. In humans there are still no methods to measure islet blood flow selectively, but new developments in radiological techniques hold great hopes for the future. PMID:27124642

  6. Prediction of blood pressure and blood flow in stenosed renal arteries using CFD

    NASA Astrophysics Data System (ADS)

    Jhunjhunwala, Pooja; Padole, P. M.; Thombre, S. B.; Sane, Atul

    2018-04-01

    In the present work an attempt is made to develop a diagnostive tool for renal artery stenosis (RAS) which is inexpensive and in-vitro. To analyse the effects of increase in the degree of severity of stenosis on hypertension and blood flow, haemodynamic parameters are studied by performing numerical simulations. A total of 16 stenosed models with varying degree of stenosis severity from 0-97.11% are assessed numerically. Blood is modelled as a shear-thinning, non-Newtonian fluid using the Carreau model. Computational Fluid Dynamics (CFD) analysis is carried out to compute the values of flow parameters like maximum velocity and maximum pressure attained by blood due to stenosis under pulsatile flow. These values are further used to compute the increase in blood pressure and decrease in available blood flow to kidney. The computed available blood flow and secondary hypertension for varying extent of stenosis are mapped by curve fitting technique using MATLAB and a mathematical model is developed. Based on these mathematical models, a quantification tool is developed for tentative prediction of probable availability of blood flow to the kidney and severity of stenosis if secondary hypertension is known.

  7. Multifractality of cerebral blood flow

    NASA Astrophysics Data System (ADS)

    West, Bruce J.; Latka, Miroslaw; Glaubic-Latka, Marta; Latka, Dariusz

    2003-02-01

    Scale invariance, the property relating time series across multiple scales, has provided a new perspective of physiological phenomena and their underlying control systems. The traditional “signal plus noise” paradigm of the engineer was first replaced with a model in which biological time series have a fractal structure in time (Fractal Physiology, Oxford University Press, Oxford, 1994). This new paradigm was subsequently shown to be overly restrictive when certain physiological signals were found to be characterized by more than one scaling parameter and therefore to belong to a class of more complex processes known as multifractals (Fractals, Plenum Press, New York, 1988). Here we demonstrate that in addition to heart rate (Nature 399 (1999) 461) and human gait (Phys. Rev. E, submitted for publication), the nonlinear control system for cerebral blood flow (CBF) (Phys. Rev. Lett., submitted for publication; Phys. Rev. E 59 (1999) 3492) is multifractal. We also find that this multifractality is greatly reduced for subjects with “serious” migraine and we present a simple model for the underlying control process to describe this effect.

  8. Interaction between left ventricular twist mechanics and arterial haemodynamics during localised, non-metabolic hyperaemia with and without blood flow restriction.

    PubMed

    van Mil, Anke C C M; Pearson, James; Drane, Aimee L; Cockcroft, John R; McDonnell, Barry J; Stöhr, Eric J

    2016-04-01

    What is the central question of this study? Left ventricular (LV) twist is reduced when afterload is increased, but the meaning of this specific heart muscle response and its impact on cardiac output are not well understood. What is the main finding and its importance? This study shows that LV twist responds even when arterial haemodynamics are altered only locally, and without apparent change in metabolic (i.e. heat-induced) demand. The concurrent decline in cardiac output and LV twist during partial arterial occlusion despite the increased peripheral demand caused by heat stress suggests that LV twist may be involved in the protective sensing of heart muscle stress that can override the provision of the required cardiac output. Whether left ventricular (LV) twist and untwisting rate (LV twist mechanics) respond to localised, peripheral, non-metabolic changes in arterial haemodynamics within an individual's normal afterload range is presently unknown. Furthermore, previous studies indicate that LV twist mechanics may override the provision of cardiac output, but this hypothesis has not been examined purposefully. Therefore, we acutely altered local peripheral arterial haemodynamics in 11 healthy humans (women/men n = 3/8; age 26 ± 5 years) by bilateral arm heating (BAH). Ultrasonography was used to examine arterial haemodynamics, LV twist mechanics and the twist-to-shortening ratio (TSR). To determine the arterial function-dependent contribution of LV twist mechanics to cardiac output, partial blood flow restriction to the arms was applied during BAH (BAHBFR ). Bilateral arm heating increased arm skin temperatures [change (Δ) +6.4 ± 0.9°C, P < 0.0001] but not core temperature (Δ -0.0 ± 0.1°C, P > 0.05), concomitant to increases in brachial artery blood flow (Δ 212 ± 77 ml, P < 0.0001), cardiac output (Δ 495 ± 487 l min(-1) , P < 0.05), LV twist (Δ 3.0 ± 3.5 deg, P < 0.05) and TSR (Δ 3.3 ± 1.3, P < 0.05) but

  9. Blood flow and microgravity

    NASA Astrophysics Data System (ADS)

    Bureau, Lionel; Coupier, Gwennou; Dubois, Frank; Duperray, Alain; Farutin, Alexander; Minetti, Christophe; Misbah, Chaouqi; Podgorski, Thomas; Tsvirkun, Daria; Vysokikh, Mikhail

    2017-01-01

    The absence of gravity during space flight can alter cardio-vascular functions partially due to reduced physical activity. This affects the overall hemodynamics, and in particular the level of shear stresses to which blood vessels are submitted. Long-term exposure to space environment is thus susceptible to induce vascular remodeling through a mechanotransduction cascade that couples vessel shape and function with the mechanical cues exerted by the circulating cells on the vessel walls. Central to such processes, the glycocalyx - i.e. the micron-thick layer of biomacromolecules that lines the lumen of blood vessels and is directly exposed to blood flow - is a major actor in the regulation of biochemical and mechanical interactions. We discuss in this article several experiments performed under microgravity, such as the determination of lift force and collective motion in blood flow, and some preliminary results obtained in artificial microfluidic circuits functionalized with endothelium that offer interesting perspectives for the study of the interactions between blood and endothelium in healthy condition as well as by mimicking the degradation of glycocalyx caused by long space missions. A direct comparison between experiments and simulations is discussed. xml:lang="fr"

  10. Regional Blood Volume and Peripheral Blood Flow in the Postural Tachycardia Syndrome

    PubMed Central

    Stewart, Julian M.; Montgomery, Leslie D.

    2015-01-01

    Variants of postural tachycardia syndrome (POTS) are associated with increased (“high flow” POTS, HFP), decreased (“low flow POTS”, LFP) and normal (“normal flow POTS”, NFP) blood flow measured in the lower extremities while supine. We propose that postural tachycardia is related to thoracic hypovolemia during orthostasis but that the patterns of peripheral blood flow relate to different mechanisms for thoracic hypovolemia. We studied 37 POTS patients aged 14-21 years: 14 LFP, 15 NFP and 8 HFP patients and 12 healthy control subjects. Peripheral blood flow was measured supine by venous occlusion strain gauge plethysmography of the forearm and calf in order to subgroup patients. Using indocyanine green techniques we showed decreased cardiac index (CI) and increased total peripheral resistance (TPR) in LFP, increased CI and decreased TPR in HFP, and unchanged CI and TPR in NFP while supine compared to control subjects. Blood volume tended to be decreased in LFP compared to control subjects. We used impedance plethysmography to assess regional blood volume redistribution during upright tilt. Thoracic blood volume decreased while splanchnic, pelvic and leg blood volumes increased for all subjects during orthostasis, but were markedly lower than control for all POTS groups. Splanchnic volume was increased in NFP and LFP. Pelvic blood volume was increased in HFP only. Calf volume was increased above control in HFP and LFP. The results support the hypothesis of [at least] three pathophysiologic variants of POTS distinguished by peripheral blood flow related to characteristic changes in regional circulations. The data demonstrate enhanced thoracic hypovolemia during upright tilt and confirm that POTS is related to inadequate cardiac venous return during orthostasis. PMID:15117717

  11. Mild aerobic training with blood flow restriction increases the hypertrophy index and MuSK in both slow and fast muscles of old rats: Role of PGC-1α.

    PubMed

    Bahreinipour, Mohammad-Ali; Joukar, Siyavash; Hovanloo, Fariborz; Najafipour, Hamid; Naderi, Vida; Rajiamirhasani, Alireza; Esmaeili-Mahani, Saeed

    2018-06-01

    Existing evidence emphasize the role of mitochondrial dysfunction in sarcopenia which is revealed as loss of skeletal muscle mass and neuromuscular junction remodeling. We assessed the effect of low-intensity aerobic training along with blood flow restriction on muscle hypertrophy index, muscle-specific kinase (MuSK), a pivotal protein of the neuromuscular junction and Peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC-1α) in aged male rats. Animals groups were control (CTL), sham (Sh), leg blood flow restriction (BFR), exercise (Ex), sham + exercise (Sh + Ex), and BFR plus exercise (BFR + Ex) groups. The exercise groups were trained with low intensity exercise for 10 weeks. 48 h after the last training session, animals were sacrificed under anesthesia. Soleus and EDL muscles were isolated, hypertrophy index was estimated and MuSK and PGC-1α were measured by western blot method. Hypertrophy index enhanced in soleus and Extensor digitorum longus (EDL) muscles of BFR + Ex group (P < 0.01 versus CTL and Sh groups, and P < 0.001 versus other groups). The MuSK protein of soleus and EDL muscles increased in BFR + Ex group (P < 0.01 and P < 0.001, respectively) in comparison with CTL and Sh groups. In BFR + Ex group, the PGC-1α protein increased in both soleus and EDL (P < 0.001 compared to other groups). Also the PGC-1α of soleus muscle was higher in Ex and Sh + Ex groups versus CTL and Sh groups (P < 0.05). Findings suggest that low endurance exercise plus BFR improves the MuSK and hypertrophy index of both slow and fast muscles of elderly rats probably through the rise of PGC-1α expression. Copyright © 2018. Published by Elsevier Inc.

  12. Self-separation of blood plasma from whole blood during the capillary flow in microchannel

    NASA Astrophysics Data System (ADS)

    Nunna, Bharath Babu; Zhuang, Shiqiang; Lee, Eon Soo

    2017-11-01

    Self-separation of blood plasma from whole blood in microchannels is of great importance due to the enormous range of applications in healthcare and diagnostics. Blood is a multiphase complex fluid, composed of cells suspended in blood plasma. RBCs are the suspended particles whose shape changes during the flow of blood. The primary constituents of blood are erythrocytes or red blood cells (RBCs), leukocytes or white blood cells (WBCs), thrombocytes or platelets and blood plasma. The existence of RBCs in blood makes the blood a non-Newtonian fluid. The current study of separation of blood plasma from whole blood during self-driven flows in a single microchannel without bifurcation, by enhancing the capillary effects. The change in the capillary effect results in a change in contact angle which directly influences the capillary flow. The flow velocity directly influences the net force acting on the RBCs and influence the separation process. The experiments are performed on the PDMS microchannels with different contact angles by altering the surface characteristics using plasma treatment. The change in the separation length is studied during the capillary flow of blood in microchannel. Bharath Babu Nunna is a researcher in mechanical engineering and implementing the novel and innovative technologies in the biomedical devices to enhance the sensitivity of the disease diagnosis.

  13. Modeling microcirculatory blood flow: current state and future perspectives.

    PubMed

    Gompper, Gerhard; Fedosov, Dmitry A

    2016-01-01

    Microvascular blood flow determines a number of important physiological processes of an organism in health and disease. Therefore, a detailed understanding of microvascular blood flow would significantly advance biophysical and biomedical research and its applications. Current developments in modeling of microcirculatory blood flow already allow to go beyond available experimental measurements and have a large potential to elucidate blood flow behavior in normal and diseased microvascular networks. There exist detailed models of blood flow on a single cell level as well as simplified models of the flow through microcirculatory networks, which are reviewed and discussed here. The combination of these models provides promising prospects for better understanding of blood flow behavior and transport properties locally as well as globally within large microvascular networks. © 2015 Wiley Periodicals, Inc.

  14. Spiral blood flow in aorta-renal bifurcation models.

    PubMed

    Javadzadegan, Ashkan; Simmons, Anne; Barber, Tracie

    2016-01-01

    The presence of a spiral arterial blood flow pattern in humans has been widely accepted. It is believed that this spiral component of the blood flow alters arterial haemodynamics in both positive and negative ways. The purpose of this study was to determine the effect of spiral flow on haemodynamic changes in aorta-renal bifurcations. In this regard, a computational fluid dynamics analysis of pulsatile blood flow was performed in two idealised models of aorta-renal bifurcations with and without flow diverter. The results show that the spirality effect causes a substantial variation in blood velocity distribution, while causing only slight changes in fluid shear stress patterns. The dominant observed effect of spiral flow is on turbulent kinetic energy and flow recirculation zones. As spiral flow intensity increases, the rate of turbulent kinetic energy production decreases, reducing the region of potential damage to red blood cells and endothelial cells. Furthermore, the recirculation zones which form on the cranial sides of the aorta and renal artery shrink in size in the presence of spirality effect; this may lower the rate of atherosclerosis development and progression in the aorta-renal bifurcation. These results indicate that the spiral nature of blood flow has atheroprotective effects in renal arteries and should be taken into consideration in analyses of the aorta and renal arteries.

  15. Mammary blood flow regulation in the nursing rabbit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Katz, M.; Creasy, R.K.

    Cardiac output and mammary blood flow distribution prior to and after suckling were studied in 10 nursing rabbits by means of radionuclide-labeled microspheres. Suckling was followed by a 5.8% rise in cardiac output and a 20.4% rise in mammary blood flow. Determinations of intraglandular blood flow distribution have shown that there was a 43% increase in blood flow to the glands suckled from as compared to a 22.7% rise to the contralateral untouched glands and a 4.9% rise in the remainder of untouched glands. The conclusion is that a local mechanism may be involved in the regulation of mammary bloodmore » flow in the nursing rabbit.« less

  16. Cerebellar blood flow in methylmercury poisoning (Minamata disease).

    PubMed

    Itoh, K; Korogi, Y; Tomiguchi, S; Takahashi, M; Okajima, T; Sato, H

    2001-04-01

    We looked at regional cerebellar blood flow in patients with Minamata disease (MD) using technetium-99m ethyl cysteinate dimer (99m-Tc-ECD). We carried out single-photon emission computed tomography (SPECT) on 15 patients with MD (eight men, seven women, aged 51-78 years, mean 70.5 years) and 11 control subjects (eight men, three women, aged 62-80 years, mean 72.5 years). Regional blood flow was measured in the superior, middle, and inferior portions of the cerebellar hemispheres, and the frontal, temporal and occipital cerebral lobes. The degree of cerebellar atrophy was assessed on MRI. There were significant differences in regional blood flow in all parts of the cerebellum between patients and control, but no significant decrease was observed in the cerebrum. Blood flow was lower in the inferior cerebellum than in the other parts. Even in patients without cerebellar atrophy, flow was significantly decreased regional blood flow in the inferior part.

  17. Sildenafil Citrate in Fetal Growth Restriction

    PubMed Central

    Panda, Subrat; Das, Ananya; Md Nowroz, Hossain

    2014-01-01

    Background Pregnancies with early onset fetal growth restriction have poor perinatal outcome. Sildenafil citrate (PDE -5 inhibitor) as a vasodilator increases utero-placental blood flow and potentiates fetal growth. Case Presentation In this study, a case was examined and Sildenafil was administered for her. It was found that Sildenafil improved the uterine blood flow with a favorable fetal outcome at delivery. Conclusion Sildenafil, as a vasodilator has emerged as a potential management option in the treatment of Intra Uterine Growth Retardation (IUGR) and preeclampsia by later normalization in velocimetric profile. PMID:25202677

  18. Supplementation of corn dried distillers' grains plus solubles to gestating beef cows fed low-quality forage:II. Impacts on uterine blood flow, circulating estradiol-17beta and progesterone, and hepatic steriod metabolizing

    USDA-ARS?s Scientific Manuscript database

    Improving uterine blood flow in nutrient restricted cows is vital to prevent under development of the fetus leading to decreased production characteristics of the offspring. This study examined uterine blood flow, steroid concentrations, and the activity of steroid metabolizing enzymes in pregnant b...

  19. Hemodilution increases cerebral blood flow in acute ischemic stroke

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vorstrup, S.; Andersen, A.; Juhler, M.

    1989-07-01

    We measured cerebral blood flow in 10 consecutive, but selected, patients with acute ischemic stroke (less than 48 hours after onset) before and after hemodilution. Cerebral blood flow was measured by xenon-133 inhalation and emission tomography, and only patients with focal hypoperfusion in clinically relevant areas were included. Hemodilution was done according to the hematocrit level: for a hematocrit greater than or equal to 42%, 500 ml whole blood was drawn and replaced by the same volume of dextran 40; for a hematocrit between 37% and 42%, only 250 ml whole blood was drawn and replaced by 500 cc ofmore » dextran 40. Mean hematocrit was reduced by 16%, from 46 +/- 5% (SD) to 39 +/- 5% (SD) (p less than 0.001). Cerebral blood flow increased in both hemispheres by an average of 20.9% (p less than 0.001). Regional cerebral blood flow increased in the ischemic areas in all cases, on an average of 21.4 +/- 12.0% (SD) (p less than 0.001). In three patients, a significant redistribution of flow in favor of the hypoperfused areas was observed, and in six patients, the fractional cerebral blood flow increase in the hypoperfused areas was of the same magnitude as in the remainder of the brain. In the last patient, cerebral blood flow increased relatively less in the ischemic areas. Our findings show that cerebral blood flow increases in the ischemic areas after hemodilution therapy in stroke patients. The marked regional cerebral blood flow increase seen in some patients could imply an improved oxygen delivery to the ischemic tissue.« less

  20. On the Restricted Toda and c-KdV Flows of Neumann Type

    NASA Astrophysics Data System (ADS)

    Zhou, RuGuang; Qiao, ZhiJun

    2000-09-01

    It is proven that on a symplectic submanifold the restricted c-KdV flow is just the interpolating Hamiltonian flow of invariant for the restricted Toda flow, which is an integrable symplectic map of Neumann type. They share the common Lax matrix, dynamical r-matrix and system of involutive conserved integrals. Furthermore, the procedure of separation of variables is considered for the restricted c-KdV flow of Neumann type. The project supported by the Chinese National Basic Research Project "Nonlinear Science" and the Doctoral Programme Foundation of Institution of High Education of China. The first author also thanks the National Natural Science Foundation of China (19801031) and "Qinglan Project" of Jiangsu Province of China; and the second author also thanks the Alexander von Humboldt Fellowships, Deutschland, the Special Grant of Excellent Ph. D Thesis of China, the Science & Technology Foundation (Youth Talent Foundation) and the Science Research Foundation of Education Committee of Liaoning Province of China.

  1. Dynamic Effect of Rolling Massage on Blood Flow

    NASA Astrophysics Data System (ADS)

    Chen, Yan-Yan; Yi, Hou-Hui; Li, Hua-Bing; Fang, Hai-Ping

    2009-02-01

    The Chinese traditional medical massage has been used as a natural therapy to eliminate some diseases. Here, the effect of the rolling massage frequency to the blood flow in the blood vessels under the rolling massage manipulation is studied by the lattice Boltzmann simulation. The simulation results show that when the frequency is smaller than or comparable to the pulsatile frequency of the blood flow, the effect on the blood flux by the rolling massage is small. On the contrast, if the frequency is twice or more times of the pulsatile frequency of the blood flow, the blood flux is greatly enhanced and increases linearly with respect to the frequency. Similar behavior has also been observed on the shear stress on the blood vessel walls. The result is helpful for understanding that the rolling massage has the function of promoting the blood circulation and removing the blood stasis.

  2. Cerebral blood flow regulation during cognitive tasks

    PubMed Central

    Sorond, Farzaneh A.; Schnyer, D.M.; Serrador, J.M.; Milberg, W.P.; Lipsitz, L.A.

    2008-01-01

    Aging is associated with frontal subcortical microangiopathy and executive cognitive dysfunction, suggesting that elderly individuals may have impaired metabolic activation of cerebral blood flow to the frontal lobes. We used transcranial Doppler (TCD) ultrasound to examine the cerebral blood flow response to executive control and visual tasks in the anterior and posterior cerebral circulations and to determine the effects of healthy aging on cerebral blood flow regulation during cognitive tasks. Continuous simultaneous anterior cerebral artery (ACA) and posterior cerebral artery (PCA) blood flow velocities (BFVs) and mean arterial pressure (MAP) were measured in response to word stem completion (WSC) and a visual search (VS) task in 29 healthy subjects (14 young, 30 ± 1.5 years; 15 old, 74 ± 1.4 years). We found that: (1) ACA and PCA blood flow velocities are both significantly increased during WSC and VS cognitive tasks, (2) ACA and PCA activations were task specific in our young volunteers, with ACA > PCA BFV during the WSC task and PCA > ACA BFV during the VS task, (3) while healthy elderly subjects also had PCA > ACA BFV during the VS task, they did not have ACA > PCA activation during the WSC task, and (4) healthy elderly subjects tend to have overall greater increases in BFV during both cognitive tasks. We conclude that TCD can be used to monitor cerebrovascular hemodynamics during the performance of cognitive tasks. Our data suggest that there is differential blood flow increase in the ACA and PCA in young versus elderly subjects during cognitive tasks. PMID:18387547

  3. The Role of Neuronal Signaling in Controlling Cerebral Blood Flow

    ERIC Educational Resources Information Center

    Drake, Carrie T.; Iadecola, Costantino

    2007-01-01

    Well-regulated blood flow within the brain is vital to normal function. The brain's requirement for sufficient blood flow is ensured by a tight link between neural activity and blood flow. The link between regional synaptic activity and regional cerebral blood flow, termed functional hyperemia, is the basis for several modern imaging techniques…

  4. Monitoring blood flow responses during topical ALA-PDT

    PubMed Central

    Becker, Theresa L.; Paquette, Anne D.; Keymel, Kenneth R.; Henderson, Barbara W.; Sunar, Ulas

    2011-01-01

    Photodynamic therapy (PDT) using topical 5-aminolevulinic acid (ALA) is currently used as a clinical treatment for nonmelanoma skin cancers. In order to optimize PDT treatment, vascular disruption early in treatment must be identified and prevented. We present blood flow responses to topical ALA-PDT in a preclinical model and basal cell carcinoma patients assessed by diffuse correlation spectroscopy (DCS). Our results show that ALA-PDT induced early blood flow changes and these changes were irradiance dependent. It is clear that there exists considerable variation in the blood flow responses in patients from lesion to lesion. Monitoring blood flow parameter may be useful for assessing ALA-PDT response and planning. PMID:21326642

  5. Postexercise blood flow restriction does not enhance muscle hypertrophy induced by multiple-set high-load resistance exercise.

    PubMed

    Madarame, Haruhiko; Nakada, Satoshi; Ohta, Takahisa; Ishii, Naokata

    2018-05-01

    To test the applicability of postexercise blood flow restriction (PEBFR) in practical training programmes, we investigated whether PEBFR enhances muscle hypertrophy induced by multiple-set high-load resistance exercise (RE). Seven men completed an eight-week RE programme for knee extensor muscles. Employing a within-subject design, one leg was subjected to RE + PEBFR, whereas contralateral leg to RE only. On each exercise session, participants performed three sets of unilateral knee extension exercise at approximately 70% of their one-repetition maximum for RE leg first, and then performed three sets for RE + PEBFR leg. Immediately after completion of the third set, the proximal portion of the RE + PEBFR leg was compressed with an air-pressure cuff for 5 min at a pressure ranging from 100 to 150 mmHg. If participants could perform 10 repetitions for three sets in two consecutive exercise sessions, the work load was increased by 5% at the next exercise session. Muscle thickness and strength of knee extensor muscles were measured before and after the eight-week training period and after the subsequent eight-week detraining period. There was a main effect of time but no condition × time interaction or main effect of condition for muscle thickness and strength. Both muscle thickness and strength increased after the training period independent of the condition. This result suggests that PEBFR would not be an effective training method at least in an early phase of adaptation to high-load resistance exercise. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  6. The effects of recirculation flows on mass transfer from the arterial wall to flowing blood.

    PubMed

    Zhang, Zhiguo; Deng, Xiaoyan; Fan, Yubo; Guidoin, Robert

    2008-01-01

    Using a sudden tubular expansion as a model of an arterial stenosis, the effect of disturbed flow on mass transfer from the arterial wall to flowing blood was studied theoretically and tested experimentally by measuring the dissolution rate of benzoic acid disks forming the outer tube of a sudden tubular expansion. The study revealed that mass transfer from vessel wall to flowing fluid in regions of disturbed flow is independent of wall shear rates. The rate of mass transfer is significantly higher in regions of disturbed flow with a local maximum around the reattachment point where the wall shear rate is zero. The experimental study also revealed that the rate of mass transfer from the vessel wall to a flowing fluid is much higher in the presence of microspheres (as models of blood cells) in the flowing fluid and under the condition of pulsatile flow than in steady flow. These results imply that flow disturbance may enhance the transport of biochemicals and macromolecules, such as plasma proteins and lipoproteins synthesized within the blood vessel wall, from the blood vessel wall to flowing blood.

  7. Blood Flow After Exercise-Induced Muscle Damage

    PubMed Central

    Selkow, Noelle M.; Herman, Daniel C.; Liu, Zhenqi; Hertel, Jay; Hart, Joseph M.; Saliba, Susan A.

    2015-01-01

    Context: The most common modality used to address acute inflammation is cryotherapy. Whereas pain decreases with cryotherapy, evidence that changes occur in perfusion of skeletal muscle is limited. We do not know whether ice attenuates the increases in perfusion associated with acute inflammation. Objective: To examine the effects of repeated applications of ice bags on perfusion of the gastrocnemius muscle after an eccentric exercise protocol. Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants: Eighteen healthy participants (3 men, 15 women; age = 22.2 ± 2.2 years, height = 166.0 ± 11.9 cm, mass = 69.4 ± 25.0 kg). Intervention(s): To induce eccentric muscle damage, participants performed 100 unilateral heel-lowering exercises off a step to the beat of a metronome. A randomized intervention (cryotherapy, sham, control) was applied to the exercised lower extremity immediately after the protocol and again at 10, 24, and 34 hours after the protocol. Main Outcome Measure(s): Baseline perfusion measurements (blood volume, blood flow, and blood flow velocity) were taken using contrast-enhanced ultrasound of the exercised leg. Perfusion was reassessed after the first intervention and 48 hours after the protocol as percentage change scores. Pain was measured with a visual analog scale at baseline and at 10, 24, 34, and 48 hours after the protocol. Separate repeated-measures analyses of variance were used to assess each dependent variable. Results: We found no interactions among interventions for microvascular perfusion. Blood volume and blood flow, however, increased in all conditions at 48 hours after exercise (P < .001), and blood flow velocity decreased postintervention from baseline (P = .041). We found a time-by-intervention interaction for pain (P = .009). Visual analog scale scores were lower for the cryotherapy group than for the control group at 34 and 48 hours after exercise. Conclusions: Whereas eccentric muscle damage

  8. Blood Flow through an Open-Celled Foam

    NASA Astrophysics Data System (ADS)

    Ortega, Jason; Maitland, Duncan

    2011-11-01

    The Hazen-Dupuit-Darcy (HDD) equation is commonly used in engineering applications to model the pressure gradient of flow through a porous media. One major advantage of this equation is that it simplifies the complex geometric details of the porous media into two coefficients: the permeability, K, and form factor, C. However through this simplification, the flow details within the porous media are no longer accessible, making it difficult to study the phenomena that contribute to changes in K and C due to clotting of blood flow. To obtain a more detailed understanding of blood flow through a porous media, a direct assessment of the complex interstitial geometry and flow is required. In this study, we solve the Navier-Stokes equations for Newtonian and non-Newtonian blood flow through an open-celled foam geometry obtained from a micro-CT scan. The nominal strut size of the foam sample is of O(10e-5) m and the corresponding Reynolds number based upon this length ranges up to O(10). Fitting the pressure gradient vs. Darcy velocity data with the HDD equation demonstrates that both viscous and inertial forces play an important role in the flow through the foam at these Reynolds numbers. Recirculation zones are observed to form in the wake of the pore struts, producing regions of flow characterized by both low shear rates and long fluid residence times, factors of which have been shown in previous studies to promote blood clotting.

  9. Methods of blood flow measurement in the arterial circulatory system.

    PubMed

    Tabrizchi, R; Pugsley, M K

    2000-01-01

    The most commonly employed techniques for the in vivo measurement of arterial blood flow to individual organs involve the use of flow probes or sensors. Commercially available systems for the measurement of in vivo blood flow can be divided into two categories: ultrasonic and electromagnetic. Two types of ultrasonic probes are used. The first type of flow probe measures blood flow-mediated Doppler shifts (Doppler flowmetry) in a vessel. The second type of flow probe measures the "transit time" required by an emitted ultrasound wave to traverse the vessel and are transit-time volume flow sensors. Measurement of blood flow in any vessel requires that the flow probe or sensor be highly accurate and exhibit signal linearity over the flow range in the vessel of interest. Moreover, additional desirable features include compact design, size, and weight. An additional important feature for flow probes is that they exhibit good biocompatability; it is imperative for the sensor to behave in an inert manner towards the biological system. A sensitive and reliable method to assess blood flow in individual organs in the body, other than by the use of probes/sensors, is the reference sample method that utilizes hematogeneously delivered microspheres. This method has been utilized to a large extend to assess regional blood flow in the entire body. Obviously, the purpose of measuring blood flow is to determine the amount of blood delivered to a given region per unit time (milliliters per minute) and it is desirable to achieve this goal by noninvasive methodologies. This, however, is not always possible. This review attempts to offer an overview of some of the techniques available for the assessment of regional blood flow in the arterial circulatory system and discusses advantages and disadvantages of these common techniques.

  10. Effects of Aortic Irregularities on the Blood Flow

    NASA Astrophysics Data System (ADS)

    Gutmark-Little, Iris; Prahl-Wittberg, Lisa; van Wyk, Stevin; Mihaescu, Mihai; Fuchs, Laszlo; Backeljauw, Philippe; Gutmark, Ephraim

    2013-11-01

    Cardiovascular defects characterized by geometrical anomalies of the aorta and its effect on the blood flow are investigated. The flow characteristics change with the aorta geometry and the rheological properties of the blood. Flow characteristics such as wall shear stress often play an important role in the development of vascular disease. In the present study, blood is considered to be non-Newtonian and is modeled using the Quemada model, an empirical model that is valid for different red blood cell loading. Three patient-specific aortic geometries are studied using Large Eddy Simulations (LES). The three geometries represent malformations that are typical in patients populations having a genetic disorder called Turner syndrome. The results show a highly complex flow with regions of recirculation that are enhanced in two of the three aortas. Moreover, blood flow is diverted, due to the malformations, from the descending aorta to the three side branches of the arch. The geometry having an elongated transverse aorta has larger areas of strong oscillatory wall shear stress.

  11. Dynamics of blood flow in a microfluidic ladder network

    NASA Astrophysics Data System (ADS)

    Maddala, Jeevan; Zilberman-Rudenko, Jevgenia; McCarty, Owen

    The dynamics of a complex mixture of cells and proteins, such as blood, in perturbed shear flow remains ill-defined. Microfluidics is a promising technology for improving the understanding of blood flow under complex conditions of shear; as found in stent implants and in tortuous blood vessels. We model the fluid dynamics of blood flow in a microfluidic ladder network with dimensions mimicking venules. Interaction of blood cells was modeled using multiagent framework, where cells of different diameters were treated as spheres. This model served as the basis for predicting transition regions, collision pathways, re-circulation zones and residence times of cells dependent on their diameters and device architecture. Based on these insights from the model, we were able to predict the clot formation configurations at various locations in the device. These predictions were supported by the experiments using whole blood. To facilitate platelet aggregation, the devices were coated with fibrillar collagen and tissue factor. Blood was perfused through the microfluidic device for 9 min at a physiologically relevant venous shear rate of 600 s-1. Using fluorescent microscopy, we observed flow transitions near the channel intersections and at the areas of blood flow obstruction, which promoted larger thrombus formation. This study of integrating model predictions with experimental design, aids in defining the dynamics of blood flow in microvasculature and in development of novel biomedical devices.

  12. Blood Pump Development Using Rocket Engine Flow Simulation Technology

    NASA Technical Reports Server (NTRS)

    Kwak, Dochan; Kiris, Cetin

    2001-01-01

    This paper reports the progress made towards developing complete blood flow simulation capability in humans, especially in the presence of artificial devices such as valves and ventricular assist devices. Devices modeling poses unique challenges different from computing the blood flow in natural hearts and arteries. There are many elements needed to quantify the flow in these devices such as flow solvers, geometry modeling including flexible walls, moving boundary procedures and physiological characterization of blood. As a first step, computational technology developed for aerospace applications was extended to the analysis and development of a ventricular assist device (VAD), i.e., a blood pump. The blood flow in a VAD is practically incompressible and Newtonian, and thus an incompressible Navier-Stokes solution procedure can be applied. A primitive variable formulation is used in conjunction with the overset grid approach to handle complex moving geometry. The primary purpose of developing the incompressible flow analysis capability was to quantify the flow in advanced turbopump for space propulsion system. The same procedure has been extended to the development of NASA-DeBakey VAD that is based on an axial blood pump. Due to massive computing requirements, high-end computing is necessary for simulating three-dimensional flow in these pumps. Computational, experimental, and clinical results are presented.

  13. Vascular structure determines pulmonary blood flow distribution

    NASA Technical Reports Server (NTRS)

    Hlastala, M. P.; Glenny, R. W.

    1999-01-01

    Scientific knowledge develops through the evolution of new concepts. This process is usually driven by new methodologies that provide observations not previously available. Understanding of pulmonary blood flow determinants advanced significantly in the 1960s and is now changing rapidly again, because of increased spatial resolution of regional pulmonary blood flow measurements.

  14. Quadriceps muscle blood flow and oxygen availability during repetitive bouts of isometric exercise in simulated sailing.

    PubMed

    Vogiatzis, Ioannis; Andrianopoulos, Vasileios; Louvaris, Zafeiris; Cherouveim, Evgenia; Spetsioti, Stavroula; Vasilopoulou, Maroula; Athanasopoulos, Dimitrios

    2011-07-01

    In this study, we wished to determine whether the observed reduction in quadriceps muscle oxygen availability, reported during repetitive bouts of isometric exercise in simulated sailing efforts (i.e. hiking), is because of restricted muscle blood flow. Six national-squad Laser sailors initially performed three successive 3-min hiking bouts followed by three successive 3-min cycling tests sustained at constant intensities reproducing the cardiac output recorded during each of the three hiking bouts. The blood flow index (BFI) was determined from assessment of the vastus lateralis using near-infrared spectroscopy in association with the light-absorbing tracer indocyanine green dye, while cardiac output was determined from impedance cardiography. At equivalent cardiac outputs (ranging from 10.3±0.5 to 14.8±0.86 L · min(-1)), the increase from baseline in vastus lateralis BFI across the three hiking bouts (from 1.1±0.2 to 3.1±0.6 nM · s(-1)) was lower (P = 0.036) than that seen during the three cycling bouts (from 1.1±0.2 to 7.2±1.4 nM · s(-1)) (Cohen's d: 3.80 nM · s(-1)), whereas the increase from baseline in deoxygenated haemoglobin (by ∼17.0±2.9 μM) (an index of tissue oxygen extraction) was greater (P = 0.006) during hiking than cycling (by ∼5.3±2.7 μM) (Cohen's d: 4.17 μM). The results suggest that reduced vastus lateralis muscle oxygen availability during hiking arises from restricted muscle blood flow in the isometrically acting quadriceps muscles.

  15. Dehydration accelerates reductions in cerebral blood flow during prolonged exercise in the heat without compromising brain metabolism

    PubMed Central

    Trangmar, Steven J.; Chiesa, Scott T.; Llodio, Iñaki; Garcia, Benjamin; Kalsi, Kameljit K.; Secher, Niels H.

    2015-01-01

    Dehydration hastens the decline in cerebral blood flow (CBF) during incremental exercise, whereas the cerebral metabolic rate for O2 (CMRO2) is preserved. It remains unknown whether CMRO2 is also maintained during prolonged exercise in the heat and whether an eventual decline in CBF is coupled to fatigue. Two studies were undertaken. In study 1, 10 male cyclists cycled in the heat for ∼2 h with (control) and without fluid replacement (dehydration) while internal and external carotid artery blood flow and core and blood temperature were obtained. Arterial and internal jugular venous blood samples were assessed with dehydration to evaluate CMRO2. In study 2, in 8 male subjects, middle cerebral artery blood velocity was measured during prolonged exercise to exhaustion in both dehydrated and euhydrated states. After a rise at the onset of exercise, internal carotid artery flow declined to baseline with progressive dehydration (P < 0.05). However, cerebral metabolism remained stable through enhanced O2 and glucose extraction (P < 0.05). External carotid artery flow increased for 1 h but declined before exhaustion. Fluid ingestion maintained cerebral and extracranial perfusion throughout nonfatiguing exercise. During exhaustive exercise, however, euhydration delayed but did not prevent the decline in cerebral perfusion. In conclusion, during prolonged exercise in the heat, dehydration accelerates the decline in CBF without affecting CMRO2 and also restricts extracranial perfusion. Thus, fatigue is related to a reduction in CBF and extracranial perfusion rather than CMRO2. PMID:26371170

  16. Ultrasonic Doppler measurement of renal artery blood flow

    NASA Technical Reports Server (NTRS)

    Freund, W. R.; Beaver, W. L.; Meindl, J. D.

    1976-01-01

    Studies were made of (1) blood flow redistribution during lower body negative pressure (LBNP), (2) the profile of blood flow across the mitral annulus of the heart (both perpendicular and parallel to the commissures), (3) testing and evaluation of a number of pulsed Doppler systems, (4) acute calibration of perivascular Doppler transducers, (5) redesign of the mitral flow transducers to improve reliability and ease of construction, and (6) a frequency offset generator designed for use in distinguishing forward and reverse components of blood flow by producing frequencies above and below the offset frequency. Finally methodology was developed and initial results were obtained from a computer analysis of time-varying Doppler spectra.

  17. Collision Based Blood Cell Distribution of the Blood Flow

    NASA Astrophysics Data System (ADS)

    Cinar, Yildirim

    2003-11-01

    Introduction: The goal of the study is the determination of the energy transferring process between colliding masses and the application of the results to the distribution of the cell, velocity and kinetic energy in arterial blood flow. Methods: Mathematical methods and models were used to explain the collision between two moving systems, and the distribution of linear momentum, rectilinear velocity, and kinetic energy in a collision. Results: According to decrease of mass of the second system, the velocity and momentum of constant mass of the first system are decreased, and linearly decreasing mass of the second system captures a larger amount of the kinetic energy and the rectilinear velocity of the collision system on a logarithmic scale. Discussion: The cause of concentration of blood cells at the center of blood flow an artery is not explained by Bernoulli principle alone but the kinetic energy and velocity distribution due to collision between the big mass of the arterial wall and the small mass of blood cells must be considered as well.

  18. Blood in the gastric lumen increases splanchnic blood flow and portal pressure in portal-hypertensive rats.

    PubMed

    Chen, L; Groszmann, R J

    1996-10-01

    In portal-hypertensive humans, portal blood flow and pressure increase after a meal. These hemodynamic changes may increase variceal rupture risk. The aim of this study was to determine whether blood in the stomach lumen increases splanchnic flow and portal pressure (PP) in portal-hypertensive rats. superior mesenteric artery flow and PP were measured in conscious, unrestrained, fasted partial portal vein-ligated rats with chronically implanted Doppler flow probes or portal vein catheters before and after gavage with heparinized, warmed blood from donor rats, air, standard meal, or empty tube. Percentage of changes in flow and pressure from baseline were significantly greater after gavage with blood (an increase of 22.6% +/- 3.5% and an increase of 16.4% +/- 3.1%, respectively) than empty tube (an increase of 3.4% +/- 0.6% and a decrease of 5.4% +/- 3.5%, respectively) (P < 0.005). Percentage of changes in flow and pressure were slightly but insignificantly greater after gavage with air vs. empty tube (P < 0.005). In portal-hypertensive rats, blood in the stomach lumen significantly increases splanchnic blood flow and PP. Splanchnic hyperemia from absorption of blood's calories probably contributes to these hemodynamic changes. In patients with variceal hemorrhage, blood in the stomach may increase the risk of persistent variceal bleeding or rebleeding.

  19. Blood flow structure in patients with coronary heart disease

    NASA Astrophysics Data System (ADS)

    Malinova, Lidia I.; Simonenko, Georgy V.; Denisova, Tatyana P.; Tuchin, Valery V.

    2007-05-01

    Blood flow structure was studied by PC integrated video camera with following slide by slide analysis. Volumetric blood flow velocity was supporting on constant level (1 ml/h). Silicone tube of diameter comparable with coronary arteries diameter was used as vessel model. Cell-cell interactions were studied under glucose and anticoagulants influence. Increased adhesiveness of blood cells to tube walls was revealed in patient with coronary heart disease (CHD) compare to practically healthy persons (PHP). In patients with stable angina pectoris of high functional class and patients with AMI shear stress resistant erythrocyte aggregates were predominating in blood flow structure up to microclots formation. Clotting and erythrocytes aggregation increase as response to glucose solution injection, sharply defined in patients with CHD. Heparin injection (10 000 ED) increased linear blood flow velocity both in patients with CHD and PHP. After compare our results with other author's data we can consider that method used in our study is sensible enough to investigate blood flow structure violations in patients with CHD and PHP. Several differences of cell-cell interaction in flow under glucose and anticoagulant influence were found out in patients with CHD and PHP.

  20. One dimensional blood flow in a planetocentric orbit

    NASA Astrophysics Data System (ADS)

    Haranas, Ioannis; Gkigkitzis, Ioannis

    2012-05-01

    All life on earth is accustomed to the presence of gravity. When gravity is altered, biological processes can go awry. It is of great importance to ensure safety during a spaceflight. Long term exposure to microgravity can trigger detrimental physiological responses in the human body. Fluid redistribution coupled with fluid loss is one of the effects. In particular, in microgravity blood volume is shifted towards the thorax and head. Sympathetic nervous system-induced vasoconstriction is needed to maintain arterial pressure, while venoconstriction limits venous pooling of blood prevents further reductions in venous return of blood to the heart. In this paper, we modify an existing one dimensional blood flow model with the inclusion of the hydrostatic pressure gradient that further depends on the gravitational field modified by the oblateness and rotation of the Earth. We find that the velocity of the blood flow VB is inversely proportional to the blood specific volume d, also proportional to the oblateness harmonic coefficient J2, the angular velocity of the Earth ωE, and finally proportional to an arbitrary constant c. For c = -0.39073 and ξH = -0.5 mmHg, all orbits result to less blood flow velocities than that calculated on the surface of the Earth. From all considered orbits, elliptical polar orbit of eccentricity e = 0.2 exhibit the largest flow velocity VB = 1.031 m/s, followed by the orbits of inclination i = 45°and 0°. The Earth's oblateness and its rotation contribute a 0.7% difference to the blood flow velocity.

  1. Effects of melatonin or maternal nutrient restriction on vascularity and cell proliferation in the ovine placenta

    USDA-ARS?s Scientific Manuscript database

    Previously we reported increased umbilical artery blood flow in ewes supplemented with melatonin from mid- to late-pregnancy, while maternal nutrient restriction decreased uterine artery blood flow. To further unravel these responses, this study was designed to assess placental cell proliferation an...

  2. Brain–blood amino acid correlates following protein restriction in murine maple syrup urine disease

    PubMed Central

    2014-01-01

    Background Conventional therapy for patients with maple syrup urine disease (MSUD) entails restriction of protein intake to maintain acceptable levels of the branched chain amino acid, leucine (LEU), monitored in blood. However, no data exists on the correlation between brain and blood LEU with protein restriction, and whether correction in blood is reflected in brain. Methods To address this question, we fed intermediate MSUD mice diets of 19% (standard) and 6% protein, with collection of sera (SE), striata (STR), cerebellum (CE) and cortex (CTX) for quantitative amino acid analyses. Results LEU and valine (VAL) levels in all brain regions improved on average 28% when shifting from 19% to 6% protein, whereas the same improvements in SE were on average 60%. Isoleucine (ILE) in brain regions did not improve, while the SE level improved 24% with low-protein consumption. Blood-branched chain amino acids (LEU, ILE, and VAL in sera (SE)) were 362-434 μM, consistent with human values considered within control. Nonetheless, numerous amino acids in brain regions remained abnormal despite protein restriction, including glutamine (GLN), aspartate (ASP), glutamate (GLU), gamma-aminobutyric acid (GABA), asparagine (ASN), citrulline (CIT) and serine (SER). To assess the specificity of these anomalies, we piloted preliminary studies in hyperphenylalaninemic mice, modeling another large neutral aminoacidopathy. Employing an identical dietary regimen, we found remarkably consistent abnormalities in GLN, ASP, and GLU. Conclusions Our results suggest that blood amino acid analysis may be a poor surrogate for assessing the outcomes of protein restriction in the large neutral amino acidopathies, and further indicate that chronic neurotransmitter disruptions (GLU, GABA, ASP) may contribute to long-term neurocognitive dysfunction in these disorders. PMID:24886632

  3. Brain-blood amino acid correlates following protein restriction in murine maple syrup urine disease.

    PubMed

    Vogel, Kara R; Arning, Erland; Wasek, Brandi L; McPherson, Sterling; Bottiglieri, Teodoro; Gibson, K Michael

    2014-05-08

    Conventional therapy for patients with maple syrup urine disease (MSUD) entails restriction of protein intake to maintain acceptable levels of the branched chain amino acid, leucine (LEU), monitored in blood. However, no data exists on the correlation between brain and blood LEU with protein restriction, and whether correction in blood is reflected in brain. To address this question, we fed intermediate MSUD mice diets of 19% (standard) and 6% protein, with collection of sera (SE), striata (STR), cerebellum (CE) and cortex (CTX) for quantitative amino acid analyses. LEU and valine (VAL) levels in all brain regions improved on average 28% when shifting from 19% to 6% protein, whereas the same improvements in SE were on average 60%. Isoleucine (ILE) in brain regions did not improve, while the SE level improved 24% with low-protein consumption. Blood-branched chain amino acids (LEU, ILE, and VAL in sera (SE)) were 362-434 μM, consistent with human values considered within control. Nonetheless, numerous amino acids in brain regions remained abnormal despite protein restriction, including glutamine (GLN), aspartate (ASP), glutamate (GLU), gamma-aminobutyric acid (GABA), asparagine (ASN), citrulline (CIT) and serine (SER). To assess the specificity of these anomalies, we piloted preliminary studies in hyperphenylalaninemic mice, modeling another large neutral aminoacidopathy. Employing an identical dietary regimen, we found remarkably consistent abnormalities in GLN, ASP, and GLU. Our results suggest that blood amino acid analysis may be a poor surrogate for assessing the outcomes of protein restriction in the large neutral amino acidopathies, and further indicate that chronic neurotransmitter disruptions (GLU, GABA, ASP) may contribute to long-term neurocognitive dysfunction in these disorders.

  4. Blood flow characteristics in the aortic arch

    NASA Astrophysics Data System (ADS)

    Prahl Wittberg, Lisa; van Wyk, Stevin; Mihaiescu, Mihai; Fuchs, Laszlo; Gutmark, Ephraim; Backeljauw, Philippe; Gutmark-Little, Iris

    2012-11-01

    The purpose with this study is to investigate the flow characteristics of blood in the aortic arch. Cardiovascular diseases are associated with specific locations in the arterial tree. Considering atherogenesis, it is claimed that the Wall Shear Stress (WSS) along with its temporal and spatial gradients play an important role in the development of the disease. The WSS is determined by the local flow characteristics, that in turn depends on the geometry as well as the rheological properties of blood. In this numerical work, the time dependent fluid flow during the entire cardiac cycle is fully resolved. The Quemada model is applied to account for the non-Newtonian properties of blood, an empirical model valid for different Red Blood Cell loading. Data obtained through Cardiac Magnetic Resonance Imaging have been used in order to reconstruct geometries of the the aortic arch. Here, three different geometries are studied out of which two display malformations that can be found in patients having the genetic disorder Turner's syndrome. The simulations show a highly complex flow with regions of secondary flow that is enhanced for the diseased aortas. The financial support from the Swedish Research Council (VR) and the Sweden-America Foundation is gratefully acknowledged.

  5. Regulation of Coronary Blood Flow

    PubMed Central

    Goodwill, Adam G.; Dick, Gregory M.; Kiel, Alexander M.; Tune, Johnathan D.

    2018-01-01

    The heart is uniquely responsible for providing its own blood supply through the coronary circulation. Regulation of coronary blood flow is quite complex and, after over 100 years of dedicated research, is understood to be dictated through multiple mechanisms that include extravascular compressive forces (tissue pressure), coronary perfusion pressure, myogenic, local metabolic, endothelial as well as neural and hormonal influences. While each of these determinants can have profound influence over myocardial perfusion, largely through effects on end-effector ion channels, these mechanisms collectively modulate coronary vascular resistance and act to ensure that the myocardial requirements for oxygen and substrates are adequately provided by the coronary circulation. The purpose of this series of Comprehensive Physiology is to highlight current knowledge regarding the physiologic regulation of coronary blood flow, with emphasis on functional anatomy and the interplay between the physical and biological determinants of myocardial oxygen delivery. PMID:28333376

  6. Blood flow patterns during incremental and steady-state aerobic exercise.

    PubMed

    Coovert, Daniel; Evans, LeVisa D; Jarrett, Steven; Lima, Carla; Lima, Natalia; Gurovich, Alvaro N

    2017-05-30

    Endothelial shear stress (ESS) is a physiological stimulus for vascular homeostasis, highly dependent on blood flow patterns. Exercise-induced ESS might be beneficial on vascular health. However, it is unclear what type of ESS aerobic exercise (AX) produces. The aims of this study are to characterize exercise-induced blood flow patterns during incremental and steady-state AX. We expect blood flow pattern during exercise will be intensity-dependent and bidirectional. Six college-aged students (2 males and 4 females) were recruited to perform 2 exercise tests on cycleergometer. First, an 8-12-min incremental test (Test 1) where oxygen uptake (VO2), heart rate (HR), blood pressure (BP), and blood lactate (La) were measured at rest and after each 2-min step. Then, at least 48-hr. after the first test, a 3-step steady state exercise test (Test 2) was performed measuring VO2, HR, BP, and La. The three steps were performed at the following exercise intensities according to La: 0-2 mmol/L, 2-4 mmol/L, and 4-6 mmol/L. During both tests, blood flow patterns were determined by high-definition ultrasound and Doppler on the brachial artery. These measurements allowed to determine blood flow velocities and directions during exercise. On Test 1 VO2, HR, BP, La, and antegrade blood flow velocity significantly increased in an intensity-dependent manner (repeated measures ANOVA, p<0.05). Retrograde blood flow velocity did not significantly change during Test 1. On Test 2 all the previous variables significantly increased in an intensity-dependent manner (repeated measures ANOVA, p<0.05). These results support the hypothesis that exercise induced ESS might be increased in an intensity-dependent way and blood flow patterns during incremental and steady-state exercises include both antegrade and retrograde blood flows.

  7. Sex-specific effect of endothelin in the blood pressure response to acute angiotensin II in growth-restricted rats

    PubMed Central

    Intapad, Suttira; Ojeda, Norma B.; Varney, Elliott; Royals, Thomas P.; Alexander, Barbara T.

    2015-01-01

    The renal endothelin system contributes to sex differences in blood pressure with males demonstrating greater endothelin type-A receptor-mediated responses relative to females. Intrauterine growth restriction programs hypertension and enhanced renal sensitivity to acute angiotensin II in male growth-restricted rats. Endothelin is reported to work synergistically with angiotensin II. Thus, this study tested the hypothesis that endothelin augments the blood pressure response to acute angiotensin II in male growth-restricted rats. Systemic and renal hemodynamics were determined in response to acute angiotensin II (100 nanogram/kilogram/minute for 30 minutes) with and without the endothelin type-A receptor antagonist, ABT 627(10 nanogram/kilogram/minute for 30 minutes), in rats pretreated with enalapril (250 milligram/Liter for one week) to normalize the endogenous renin angiotensin system. Endothelin type-A receptor blockade reduced angiotensin II-mediated increases in blood pressure in male control and male growth-restricted rats. Endothelin type-A receptor blockade also abolished hyper-responsiveness to acute angiotensin II in male growth-restricted rats. Yet, blood pressure remained significantly elevated above baseline following endothelin type-A receptor blockade suggesting that factors in addition to endothelin contribute to the basic angiotensin II-induced pressor response in male rats. We also determined sex-specific effects of endothelin on acute angiotensin II-mediated hemodynamic responses. Endothelin type-A receptor blockade did not reduce acute angiotensin II-mediated increases in blood pressure in female control or growth-restricted rats, intact or ovariectomized. Thus, these data suggest that endothelin type-A receptor blockade contributes to hypersensitivity to acute angiotensin II in male growth-restricted rats and further supports the sex-specific effect of endothelin on blood pressure. PMID:26459423

  8. Cerebral blood flow in humans following resuscitation from cardiac arrest

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cohan, S.L.; Mun, S.K.; Petite, J.

    1989-06-01

    Cerebral blood flow was measured by xenon-133 washout in 13 patients 6-46 hours after being resuscitated from cardiac arrest. Patients regaining consciousness had relatively normal cerebral blood flow before regaining consciousness, but all patients who died without regaining consciousness had increased cerebral blood flow that appeared within 24 hours after resuscitation (except in one patient in whom the first measurement was delayed until 28 hours after resuscitation, by which time cerebral blood flow was increased). The cause of the delayed-onset increase in cerebral blood flow is not known, but the increase may have adverse effects on brain function and maymore » indicate the onset of irreversible brain damage.« less

  9. Local viscosity distribution in bifurcating microfluidic blood flows

    NASA Astrophysics Data System (ADS)

    Kaliviotis, E.; Sherwood, J. M.; Balabani, S.

    2018-03-01

    The red blood cell (RBC) aggregation phenomenon is majorly responsible for the non-Newtonian nature of blood, influencing the blood flow characteristics in the microvasculature. Of considerable interest is the behaviour of the fluid at the bifurcating regions. In vitro experiments, using microchannels, have shown that RBC aggregation, at certain flow conditions, affects the bluntness and skewness of the velocity profile, the local RBC concentration, and the cell-depleted layer at the channel walls. In addition, the developed RBC aggregates appear unevenly distributed in the outlets of these channels depending on their spatial distribution in the feeding branch, and on the flow conditions in the outlet branches. In the present work, constitutive equations of blood viscosity, from earlier work of the authors, are applied to flows in a T-type bifurcating microchannel to examine the local viscosity characteristics. Viscosity maps are derived for various flow distributions in the outlet branches of the channel, and the location of maximum viscosity magnitude is obtained. The viscosity does not appear significantly elevated in the branches of lower flow rate as would be expected on the basis of the low shear therein, and the maximum magnitude appears in the vicinity of the junction, and towards the side of the outlet branch with the higher flow rate. The study demonstrates that in the branches of lower flow rate, the local viscosity is also low, helping us to explain why the effects of physiological red blood cell aggregation have no adverse effects in terms of in vivo vascular resistance.

  10. Glucose-dependent blood flow dynamics in murine pancreatic islets in vivo

    PubMed Central

    Nyman, Lara R.; Ford, Eric

    2010-01-01

    Pancreatic islets are highly vascularized and arranged so that regions containing β-cells are distinct from those containing other cell types. Although islet blood flow has been studied extensively, little is known about the dynamics of islet blood flow during hypoglycemia or hyperglycemia. To investigate changes in islet blood flow as a function of blood glucose level, we clamped blood glucose sequentially at hyperglycemic (∼300 mg/dl or 16.8 mM) and hypoglycemic (∼50 mg/dl or 2.8 mM) levels while simultaneously imaging intraislet blood flow in mouse models that express green fluorescent protein in the β-cells or yellow fluorescent protein in the α-cells. Using line scanning confocal microscopy, in vivo blood flow was assayed after intravenous injection of fluorescent dextran or sulforhodamine-labeled red blood cells. Regardless of the sequence of hypoglycemia and hyperglycemia, islet blood flow is faster during hyperglycemia, and apparent blood volume is greater during hyperglycemia than during hypoglycemia. However, there is no change in the order of perfusion of different islet endocrine cell types in hypoglycemia compared with hyperglycemia, with the islet core of β-cells usually perfused first. In contrast to the results in islets, there was no significant difference in flow rate in the exocrine pancreas during hyperglycemia compared with hypoglycemia. These results indicate that glucose differentially regulates blood flow in the pancreatic islet vasculature independently of blood flow in the rest of the pancreas. PMID:20071562

  11. Penile blood flow by xenon-133 washout

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Haden, H.T.; Katz, P.G.; Mulligan, T.

    1989-06-01

    Penile erectile failure is often attributed to abnormalities of vascular supply or drainage, but few direct measurements of penile blood flow have been made. We describe the xenon washout method for measurement of penile blood flow, and present the results obtained in a group of normal and impotent subjects. The procedure was performed with standard nuclear imaging equipment. Flaccid-state penile blood flow in the impotent patients studied was not significantly different from the normal group, suggesting that flaccid-state measurements may not be helpful in evaluation of erectile failure. However, this method can be used to measure penile venous outflow withmore » stimulated or induced erection, and may provide a method for detecting abnormal venous leakage.« less

  12. Gingival blood flow measurement with a non-contact laser flowmeter.

    PubMed

    Matsuki, M; Xu, Y B; Nagasawa, T

    2001-07-01

    A non-contact laser flowmeter was used to measure the changing of the gingival blood flow. Five university students with healthy oral condition were selected in this study. The blood flow measurement on the extensor digitorum (above the head of third metacarpal), with the changing of distance and angle between the probe and the tissue was used as a pre-study experiment. Blood flow rate was determined in the labial gingiva (2 mm above the cervical line) of upper central incisor using a stent fixing the probe at a 3-mm distance from the tissue. A basal level of gingival blood flow was taken two times each day for 5 days. The effects of water of different temperatures on the gingival blood flow are discussed. With the changing of distance, the blood flow rate became smaller, but there was no significant effect from the angle. The reproducibility was acceptable through the 5-day measurement. After stimulating with warm and body temperature water, the blood flow first increased significantly and then went back to the basal line (faster with the body temperature water). With cold water, different reactions between the subjects were observed.

  13. Numerical Simulation of Sickle Cell Blood Flow in the Microcirculation

    NASA Astrophysics Data System (ADS)

    Berger, Stanley A.; Carlson, Brian E.

    2001-11-01

    A numerical simulation of normal and sickle cell blood flow through the transverse arteriole-capillary microcirculation is carried out to model the dominant mechanisms involved in the onset of vascular stasis in sickle cell disease. The transverse arteriole-capillary network is described by Strahler's network branching method, and the oxygen and blood transport in the capillaries is modeled by a Krogh cylinder analysis utilizing Lighthill's lubrication theory, as developed by Berger and King. Poiseuille's law is used to represent blood flow in the arterioles. Applying this flow and transport model and utilizing volumetric flow continuity at each network bifurcation, a nonlinear system of equations is obtained, which is solved iteratively using a steepest descent algorithm coupled with a Newton solver. Ten different networks are generated and flow results are calculated for normal blood and sickle cell blood without and with precapillary oxygen loss. We find that total volumetric blood flow through the network is greater in the two sickle cell blood simulations than for normal blood owing to the anemia associated with sickle cell disease. The percentage of capillary blockage in the network increases dramatically with decreasing pressure drop across the network in the sickle cell cases while there is no blockage when normal blood flows through simulated networks. It is concluded that, in sickle cell disease, without any vasomotor dilation response to decreasing oxygen concentrations in the blood, capillary blockage will occur in the microvasculature even at average pressure drops across the transverse arteriole-capillary networks.

  14. Topical Menthol, Ice, Peripheral Blood Flow, and Perceived Discomfort

    PubMed Central

    Topp, Robert; Ledford, Elizabeth R.; Jacks, Dean E.

    2013-01-01

    Context: Injury management commonly includes decreasing arterial blood flow to the affected site in an attempt to reduce microvascular blood flow and edema and limit the induction of inflammation. Applied separately, ice and menthol gel decrease arterial blood flow, but the combined effects of ice and menthol gel on arterial blood flow are unknown. Objectives: To compare radial artery blood flow, arterial diameter, and perceived discomfort before and after the application of 1 of 4 treatment conditions. Design: Experimental crossover design. Setting: Clinical laboratory. Participants or Other Participants: Ten healthy men, 9 healthy women (mean age = 25.68 years, mean height = 1.73 m, mean weight = 76.73 kg). Intervention(s): Four treatment conditions were randomly applied for 20 minutes to the right forearm of participants on 4 different days separated by at least 24 hours: (1) 3.5 mL menthol gel, (2) 0.5 kg of crushed ice, (3) 3.5 mL of menthol gel and 0.5 kg of crushed ice, or (4) no treatment (control). Main Outcome Measure(s): Using high-resolution ultrasound, we measured right radial artery diameter (cm) and blood flow (mL/min) every 5 minutes for 20 minutes after the treatment was applied. Discomfort with the treatment was documented using a 1-to-10 intensity scale. Results: Radial artery blood flow decreased (P < .05) from baseline in the ice (−20% to −24%), menthol (−17% to −24%), and ice and menthol (−36% to −39%) treatments but not in the control (3% to 9%) at 5, 10, and 15 minutes. At 20 minutes after baseline, only the ice (−27%) and combined ice and menthol (−38%) treatments exhibited reductions in blood flow (P < .05). Discomfort was less with menthol than with the ice treatment at 5, 10, and 20 minutes after application (P < .05). Arterial diameter and heart rate did not change. Conclusions: The application of 3.5 mL of menthol was similar to the application of 0.5 kg of crushed ice in reducing peripheral blood flood. Combining

  15. Regional blood flow volume in the eustachian tube.

    PubMed

    Minami, T; Kubo, N; Tomoda, K; Yamashita, T; Kumazawa, T

    1993-01-01

    Measurements of regional blood flow around the pharyngeal orifice of the Eustachian tube were carried out after topical administration of various inflammatory mediators in 14 mongrel dogs by the hydrogen clearance method. Histamine and platelet-activating factor (PAF) resulted in a significant alteration of blood flow volume. Histamine was found to induce a dose-response related increase, whereas blood flow volume tended to decrease in each concentration range in the series of PAF administration. There was no significant difference in blood flow between topical application of leukotriene C4 and leukotriene D4. It is likely that in upper respiratory tract inflammation, such as in otitis media and in nasal allergy, activated histamine and PAF affect the microcirculation of the tubal orifice. These results suggest that disturbance of the microcirculatory system in the Eustachian tube mucosa could be involved in the pathogenesis of chronic otitis media with effusion.

  16. Mathematical models of real geometrical factors in restricted blood vessels for the analysis of CAD (coronary artery diseases) using Legendre, Boubaker and Bessel polynomials.

    PubMed

    Awojoyogbe, O B; Faromika, O P; Dada, M; Boubaker, Karem; Ojambati, O S

    2011-12-01

    Most cardiovascular emergencies are directly caused by coronary artery disease. Coronary arteries can become clogged or occluded, leading to damage to the heart muscle supplied by the artery. Modem cardiovascular medicine can certainly be improved by meticulous analysis of geometrical factors closely associated with the degenerative disease that results in narrowing of the coronary arteries. There are, however, inherent difficulties in developing this type of mathematical models to completely describe the real or ideal geometries that are very critical in plaque formation and thickening of the vessel wall. Neither the mathematical models of the blood vessels with arthrosclerosis generated by the heart and blood flow or the NMR/MRI data to construct them are available. In this study, a mathematical formulation for the geometrical factors that are very critical for the understanding of coronary artery disease is presented. Based on the Bloch NMR flow equations, we derive analytical expressions to describe in detail the NMR transverse magnetizations and signals as a function of some NMR flow and geometrical parameters which are invaluable for the analysis of blood flow in restricted blood vessels. The procedure would apply to the situations in which the geometry of the fatty deposits, (plague) on the interior walls of the coronary arteries is spherical. The boundary conditions are introduced based on Bessel, Boubaker and Legendre polynomials.

  17. [Echocardiography in Boid snakes: Demonstration and blood flow measurements].

    PubMed

    Schroff, S; Starck, J M; Krautwald-Junghanns, M-E; Pees, M

    2012-01-01

    Comparative echocardiography and blood flow measurements in different boid species. 51 healthy snakes from seven different species were examined echocardiographically under standardized conditions. The heart and the great vessels were displayed using 2-D-ultrasonography. Pulsed-wave doppler technique measurements of the blood flow within the vessels were performed and results analyzed statistically. The examinations could be performed in non-sedated snakes in ventral recumbency. The best image quality was obtained using the ventrolateral coupling site. An examination scheme applicable to all examined snake species was established. Diversity in the anatomy of vessels could be detected in different snake species. A characteristic shape of the curve demonstrating the blood flow against time could be shown for the respective vessels. There were positive correlations between the size of the snakes and the absolute blood flow (total flow, systemic flow, pulmonary flow to body length: p<0.001; r=0.770; r=0.627; r=0.766; respectively to body mass: p<0.001; r=0.815; r=0.698; r=0.788), as well as negative correlations between the size of the animals and the blood flow relative to body mass (total flow, systemic flow, pulmonary flow to body length: p<0.001; r=-0.533; r=-0.512; r=-0.478; respectively total flow to body mass: p<0.001; r=-0.768). When using standardized conditions, echocardiography in boid snakes is a useful diagnostic tool for the assessment of cardiac function. Reference values provided in this study serve as a basis for ultrasound examination in veterinary practice.

  18. A feasability study of color flow doppler vectorization for automated blood flow monitoring.

    PubMed

    Schorer, R; Badoual, A; Bastide, B; Vandebrouck, A; Licker, M; Sage, D

    2017-12-01

    An ongoing issue in vascular medicine is the measure of the blood flow. Catheterization remains the gold standard measurement method, although non-invasive techniques are an area of intense research. We hereby present a computational method for real-time measurement of the blood flow from color flow Doppler data, with a focus on simplicity and monitoring instead of diagnostics. We then analyze the performance of a proof-of-principle software implementation. We imagined a geometrical model geared towards blood flow computation from a color flow Doppler signal, and we developed a software implementation requiring only a standard diagnostic ultrasound device. Detection performance was evaluated by computing flow and its determinants (flow speed, vessel area, and ultrasound beam angle of incidence) on purposely designed synthetic and phantom-based arterial flow simulations. Flow was appropriately detected in all cases. Errors on synthetic images ranged from nonexistent to substantial depending on experimental conditions. Mean errors on measurements from our phantom flow simulation ranged from 1.2 to 40.2% for angle estimation, and from 3.2 to 25.3% for real-time flow estimation. This study is a proof of concept showing that accurate measurement can be done from automated color flow Doppler signal extraction, providing the industry the opportunity for further optimization using raw ultrasound data.

  19. Cimetidine and hepatic blood flow in polytrauma patients.

    PubMed

    Ivatury, R R; Khan, M B; Nallathambi, M; Davis, K; Stahl, W M

    1985-05-01

    Recent reports suggest that cimetidine acutely reduces liver blood flow in normal healthy subjects. To determine whether this finding is applicable to critically ill patients, we studied nine polytrauma patients admitted to a surgical ICU. All patients were being monitored with pulmonary artery catheters; all were stable with normal liver function. Liver blood flow was estimated by indocyanine green clearance, before and after administration of a single dose of 600 mg cimetidine. Hemodynamic variables were measured at the same times. Cimetidine did not significantly alter either hepatic blood flow or cardiovascular status in these critically ill patients.

  20. Connexin 36 mediates blood cell flow in mouse pancreatic islets

    PubMed Central

    Short, Kurt W.; Head, W. Steve

    2013-01-01

    The insulin-secreting β-cells are contained within islets of Langerhans, which are highly vascularized. Blood cell flow rates through islets are glucose-dependent, even though there are no changes in blood cell flow within in the surrounding exocrine pancreas. This suggests a specific mechanism of glucose-regulated blood flow in the islet. Pancreatic islets respond to elevated glucose with synchronous pulses of electrical activity and insulin secretion across all β-cells in the islet. Connexin 36 (Cx36) gap junctions between islet β-cells mediate this synchronization, which is lost in Cx36 knockout mice (Cx36−/−). This leads to glucose intolerance in these mice, despite normal plasma insulin levels and insulin sensitivity. Thus, we sought to investigate whether the glucose-dependent changes in intraislet blood cell flow are also dependent on coordinated pulsatile electrical activity. We visualized and quantified blood cell flow using high-speed in vivo fluorescence imaging of labeled red blood cells and plasma. With the use of a live animal glucose clamp, blood cell flow was measured during either hypoglycemia (∼50 mg/dl) or hyperglycemia (∼300 mg/dl). In contrast to the large glucose-dependent islet blood velocity changes observed in wild-type mice, only minimal differences are observed in both Cx36+/− and Cx36−/− mice. This observation supports a novel model where intraislet blood cell flow is regulated by the coordinated electrical activity in the islet β-cells. Because Cx36 expression and function is reduced in type 2 diabetes, the resulting defect in intraislet blood cell flow regulation may also play a significant role in diabetic pathology. PMID:24326425

  1. Methods for determination of optic nerve blood flow.

    PubMed Central

    Glazer, L. C.

    1988-01-01

    A variety of studies have been conducted over the past two decades to determine if decreased optic nerve blood flow has a role in the etiology of glaucomatous nerve damage. Five basic methods have been employed in examining blood flow. Invasive studies, utilizing electrodes placed in the optic nerve head, represent one of the first attempts to measure blood flow. More recently, the methodologies have included axoplasmic flow analysis, microspheres, radioactive tracers such as iodoantipyrine, and laser doppler measurements. The results of these studies are inconclusive and frequently contradictory. When the studies are grouped by methodology, only the iodoantipyrine data are consistent. While each of the experimental techniques has limitations, iodoantipyrine appears to have better resolution than either invasive studies or microspheres. PMID:3284212

  2. Noxious heat and scratching decrease histamine-induced itch and skin blood flow.

    PubMed

    Yosipovitch, Gil; Fast, Katharine; Bernhard, Jeffrey D

    2005-12-01

    The aim of this study was to assess the effect of thermal stimuli or distal scratching on skin blood flow and histamine-induced itch in healthy volunteers. Twenty-one healthy volunteers participated in the study. Baseline measurements of skin blood flow were obtained on the flexor aspect of the forearm. These measurements were compared with skin blood flow after various stimuli: heating the skin, cooling the skin, noxious cold 2 degrees C, noxious heat 49 degrees C, and scratching via a brush with controlled pressure. Afterwards histamine iontophoresis was performed and skin blood flow and itch intensity were measured immediately after the above-mentioned stimuli. Scratching reduced mean histamine-induced skin blood flow and itch intensity. Noxious heat pain increased basal skin blood flow but reduced histamine-induced maximal skin blood flow and itch intensity. Cold pain and cooling reduced itch intensity, but neither affected histamine-induced skin blood flow. Sub-noxious warming the skin did not affect the skin blood flow or itch intensity. These findings suggest that heat pain and scratching may inhibit itch through a neurogenic mechanism that also affects skin blood flow.

  3. A Microfluidics-based Pulpal Arteriole Blood Flow Phantom for Validation of Doppler Ultrasound Devices in Pulpal Blood Flow Velocity Measurement.

    PubMed

    Kim, Dohyun; Park, Sung-Ho

    2016-11-01

    Recently, Doppler ultrasound has been used for the measurement of pulpal blood flow in human teeth. However, the reliability of this method has not been verified. In this study, we developed a model to simulate arteriole blood flow within the dental pulp by using microfluidics. This arteriole simulator, or flow phantom, was used to determine the reliability of measurements obtained by using a Doppler ultrasound device. A microfluidic chip was fabricated by using the soft lithography technique, and blood-mimicking fluid was pumped through the channel by a microfluidic system. A Doppler ultrasound device was used for the measurement of flow velocity. The peak, mean, and minimal flow velocities obtained from the phantom and the Doppler ultrasound device were compared by using linear regression analysis and Pearson correlation coefficient. Bland-Altman analyses were performed to evaluate the velocity differences between the flow generated by the phantom and the flow measurements made with the Doppler ultrasound device. The microfluidic system was able to generate the flow profiles as intended, and the fluid flow could be monitored and controlled by the software program. There were excellent linear correlations between the peak, mean, and minimal flow velocities of the phantom and those of the Doppler ultrasound device (r = 0.94-0.996, P < .001). However, the velocities were overestimated by the Doppler ultrasound device. This phantom provides opportunities for research and education involving the Doppler ultrasound technique in dentistry. Although Doppler ultrasound can be an effective tool for the measurement of pulpal blood flow velocity, it is essential to validate and calibrate the device before clinical use. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  4. Exercise training with blood flow restriction has little effect on muscular strength and does not change IGF-1 in fit military warfighters.

    PubMed

    Jensen, Andrew E; Palombo, Laura J; Niederberger, Brenda; Turcotte, Lorraine P; Kelly, Karen R

    2016-04-01

    Aerobic exercise with blood flow restriction (aBFR) has been proposed as an adjunctive modality in numerous populations, potentially via an enhanced growth factor response. However, the effects of aBFR on highly trained warfighters have yet to be examined. The purpose of this study was to determine if adjunctive aBFR as part of a regular physical training regimen would increase markers of aerobic fitness and muscle strength in elite warfighters. In addition, we sought to determine whether the changes in blood lactate concentration induced by aBFR would be associated with alterations in the insulin-like growth factor (IGF) axis. Active-duty US Naval Special Warfare Operators (n=18, age=36.8 ± 2.2 years, weight=89.1 ± 1.2 kg, height=181.5 ± 1.4 cm) from Naval Amphibious Base Coronado were recruited to participate in 20 days of adjunctive aBFR training. Peak oxygen consumption (VO2 peak), ventilatory threshold (VT), and 1-repetition max (1-RM) bench press and squat were assessed pre- and post-aBFR training. Blood lactate and plasma IGF-1 and IGF-binding protein-3 (IGFBP-3) were assessed pre-, 2 min post-, and 30 min post-aBFR on days 1, 9, and 20 of aBFR training. Following aBFR training there were no changes in VO2 peak or VT, but there was an increase in the 1-RM for the bench press and the squat (5.0 and 3.9%, respectively, P<0.05). Blood lactate concentration at the 2-min post-exercise time point was 4.5-7.2-fold higher than pre-exercise levels on all days (P<0.001). At the 30-min post-exercise time point, blood lactate was still 1.6-2.6-fold higher than pre-exercise levels (P<0.001), but had decreased by 49-56% from the 2-min post-exercise time point (P<0.001). Plasma IGF-1 concentrations did not change over the course of the study. On day 9, plasma IGFBP-3 concentration was 4-22% lower than on day 1 (P<0.01) and 22% lower on day 9 than on day 20 at the 30-min post-exercise time point (P<0.001). Our data suggest that aBFR training does not lead to practical

  5. Effect of hindlimb unweighting on tissue blood flow in the rat

    NASA Technical Reports Server (NTRS)

    Mcdonald, K. S.; Delp, M. D.; Fitts, R. H.

    1992-01-01

    This study characterized distribution of blood flow in the rat during hindlimb unweighting (HU), and post-HU standing and exercise. The relationship between reduced hindlimb blood flow and the previously observed elevation in anaerobic metabolism observed with contractile activity in the atrophied soleus muscle was examined (Witzmann et al., 1992). Blood flow was measured during unweighting, normal standing, and running on a treadmill (15 m/min), after 15 days of HU or cage control. For another group blood flow was measured during preexercise treadmill standing and treadmill running. During unweighting, PE standing, and running no difference in soleus blood flow was observed between groups. Muscles composed mainly of fast twitch glycolytic fibers received greater blood flow during chronic unweighting. With exercise blood flow to visceral organs was reduced in control animals, a similar change was not seen in 15 day HU rats. These changes suggest a reduction in the ability of the sympathetic nervous system to distribute cardiac output after chronic HU. A reduction in blood flow to the soleus during exercise was not observed after HU and so does not explain the increased dependence of the atrophied soleus on anerobic energy production during contractile activity.

  6. Dehydration accelerates reductions in cerebral blood flow during prolonged exercise in the heat without compromising brain metabolism.

    PubMed

    Trangmar, Steven J; Chiesa, Scott T; Llodio, Iñaki; Garcia, Benjamin; Kalsi, Kameljit K; Secher, Niels H; González-Alonso, José

    2015-11-01

    Dehydration hastens the decline in cerebral blood flow (CBF) during incremental exercise, whereas the cerebral metabolic rate for O2 (CMRO2 ) is preserved. It remains unknown whether CMRO2 is also maintained during prolonged exercise in the heat and whether an eventual decline in CBF is coupled to fatigue. Two studies were undertaken. In study 1, 10 male cyclists cycled in the heat for ∼2 h with (control) and without fluid replacement (dehydration) while internal and external carotid artery blood flow and core and blood temperature were obtained. Arterial and internal jugular venous blood samples were assessed with dehydration to evaluate CMRO2 . In study 2, in 8 male subjects, middle cerebral artery blood velocity was measured during prolonged exercise to exhaustion in both dehydrated and euhydrated states. After a rise at the onset of exercise, internal carotid artery flow declined to baseline with progressive dehydration (P < 0.05). However, cerebral metabolism remained stable through enhanced O2 and glucose extraction (P < 0.05). External carotid artery flow increased for 1 h but declined before exhaustion. Fluid ingestion maintained cerebral and extracranial perfusion throughout nonfatiguing exercise. During exhaustive exercise, however, euhydration delayed but did not prevent the decline in cerebral perfusion. In conclusion, during prolonged exercise in the heat, dehydration accelerates the decline in CBF without affecting CMRO2 and also restricts extracranial perfusion. Thus, fatigue is related to a reduction in CBF and extracranial perfusion rather than CMRO2 . Copyright © 2015 the American Physiological Society.

  7. Sodium nitroprusside increases human skeletal muscle blood flow, but does not change flow distribution or glucose uptake.

    PubMed

    Pitkanen, O P; Laine, H; Kemppainen, J; Eronen, E; Alanen, A; Raitakari, M; Kirvela, O; Ruotsalainen, U; Knuuti, J; Koivisto, V A; Nuutila, P

    1999-12-15

    1. The role of blood flow as a determinant of skeletal muscle glucose uptake is at present controversial and results of previous studies are confounded by possible direct effects of vasoactive agents on glucose uptake. Since increase in muscle blood flow can be due to increased flow velocity or recruitment of new capillaries, or both, it would be ideal to determine whether the vasoactive agent affects flow distribution or only increases the mean flow. 2. In the present study blood flow, flow distribution and glucose uptake were measured simultaneously in both legs of 10 healthy men (aged 29 +/- 1 years, body mass index 24 +/- 1 kg m-2) using positron emission tomography (PET) combined with [15O]H2O and [18F]fluoro-2-deoxy-D-glucose (FDG). The role of blood flow in muscle glucose uptake was studied by increasing blood flow in one leg with sodium nitroprusside (SNP) and measuring glucose uptake simultaneously in both legs during euglycaemic hyperinsulinaemia (insulin infusion 6 pmol kg-1 min-1). 3. SNP infusion increased skeletal muscle blood flow by 86 % (P < 0.01), but skeletal muscle flow distribution and insulin-stimulated glucose uptake (61.4 +/- 7. 5 vs. 67.0 +/- 7.5 micromol kg-1 min-1, control vs. SNP infused leg, not significant), as well as flow distribution between different tissues of the femoral region, remained unchanged. The effect of SNP infusion on blood flow and distribution were unchanged during infusion of physiological levels of insulin (duration, 150 min). 4. Despite a significant increase in mean blood flow induced by an intra-arterial infusion of SNP, glucose uptake and flow distribution remained unchanged in resting muscles of healthy subjects. These findings suggest that SNP, an endothelium-independent vasodilator, increases non-nutritive, but not nutritive flow or capillary recruitment.

  8. Regulation of exercise blood flow: Role of free radicals.

    PubMed

    Trinity, Joel D; Broxterman, Ryan M; Richardson, Russell S

    2016-09-01

    During exercise, oxygen and nutrient rich blood must be delivered to the active skeletal muscle, heart, skin, and brain through the complex and highly regulated integration of central and peripheral hemodynamic factors. Indeed, even minor alterations in blood flow to these organs have profound consequences on exercise capacity by modifying the development of fatigue. Therefore, the fine-tuning of blood flow is critical for optimal physical performance. At the level of the peripheral circulation, blood flow is regulated by a balance between the mechanisms responsible for vasodilation and vasoconstriction. Once thought of as toxic by-products of in vivo chemistry, free radicals are now recognized as important signaling molecules that exert potent vasoactive responses that are dependent upon the underlying balance between oxidation-reduction reactions or redox balance. Under normal healthy conditions with low levels of oxidative stress, free radicals promote vasodilation, which is attenuated with exogenous antioxidant administration. Conversely, with advancing age and disease where background oxidative stress is elevated, an exercise-induced increase in free radicals can further shift the redox balance to a pro-oxidant state, impairing vasodilation and attenuating blood flow. Under these conditions, exogenous antioxidants improve vasodilatory capacity and augment blood flow by restoring an "optimal" redox balance. Interestingly, while the active skeletal muscle, heart, skin, and brain all have unique functions during exercise, the mechanisms by which free radicals contribute to the regulation of blood flow is remarkably preserved across each of these varied target organs. Published by Elsevier Inc.

  9. Regulation of Exercise Blood Flow: Role of Free Radicals

    PubMed Central

    Trinity, Joel D.; Broxterman, Ryan M.; Richardson, Russell S.

    2016-01-01

    During exercise, oxygen and nutrient rich blood must be delivered to the active skeletal muscle, heart, skin, and brain through the complex and highly regulated integration of central and peripheral hemodynamic factors. Indeed, even minor alterations in blood flow to these organs have profound consequences on exercise capacity by modifying the development of fatigue. Therefore, the fine-tuning of blood flow is critical for optimal physical performance. At the level of the peripheral circulation, blood flow is regulated by a balance between the mechanisms responsible for vasodilation and vasoconstriction. Once thought of as toxic by-products of in vivo chemistry, free radicals are now recognized as important signaling molecules that exert potent vasoactive responses that are dependent upon the underlying balance between oxidation-reduction reactions or redox balance. Under normal healthy conditions with low levels of oxidative stress, free radicals promote vasodilation, which is attenuated with exogenous antioxidant administration. Conversely, with advancing age and disease where background oxidative stress is elevated, an exercise-induced increase in free radicals can further shift the redox balance to a pro-oxidant state, impairing vasodilation and attenuating blood flow. Under these conditions, exogenous antioxidants improve vasodilatory capacity and augment blood flow by restoring an “optimal” redox balance. Interestingly, while the active skeletal muscle, heart, skin, and brain all have unique functions during exercise, the mechanisms by which free radicals contribute to the regulation of blood flow is remarkably preserved across each of these varied target organs. PMID:26876648

  10. Cutaneous Microvascular Blood Flow and Reactivity in Hypoxia

    PubMed Central

    Treml, Benedikt; Kleinsasser, Axel; Stadlbauer, Karl-Heinz; Steiner, Iris; Pajk, Werner; Pilch, Michael; Burtscher, Martin; Knotzer, Hans

    2018-01-01

    As is known, hypoxia leads to an increase in microcirculatory blood flow of the skin in healthy volunteers. In this pilot study, we investigated microcirculatory blood flow and reactive hyperemia of the skin in healthy subjects in normobaric hypoxia. Furthermore, we examined differences in microcirculation between hypoxic subjects with and without short-term acclimatization, whether or not skin microvasculature can acclimatize. Fourty-six healthy persons were randomly allocated to either short-term acclimatization using intermittent hypoxia for 1 h over 7 days at an FiO2 0.126 (treatment, n = 23) or sham short-term acclimatization for 1 h over 7 days at an FiO2 0.209 (control, n = 23). Measurements were taken in normoxia and at 360 and 720 min during hypoxia (FiO2 0.126). Microcirculatory cutaneous blood flow was assessed with a laser Doppler flowmeter on the forearm. Reactive hyperemia was induced by an ischemic stimulus. Measurements included furthermore hemodynamics, blood gas analyses and blood lactate. Microcirculatory blood flow increased progressively during hypoxia (12.3 ± 7.1–19.0 ± 8.1 perfusion units; p = 0.0002) in all subjects. The magnitude of the reactive hyperemia was diminished during hypoxia (58.2 ± 14.5–40.3 ± 27.4 perfusion units; p = 0.0003). Short-term acclimatization had no effect on microcirculatory blood flow. When testing for a hyperemic response of the skin's microcirculation we found a diminished signal in hypoxia, indicative for a compromised auto-regulative circulatory capacity. Furthermore, hypoxic short-term acclimatization did not affect cutaneous microcirculatory blood flow. Seemingly, circulation of the skin was unable to acclimatize using a week-long short-term acclimatization protocol. A potential limitation of our study may be the 7 days between acclimatization and the experimental test run. However, there is evidence that the hypoxic ventilatory response, an indicator of acclimatization, is increased for 1 week after

  11. Effect of Hindlimb Unweighting on Tissue Blood Flow in the Rat

    NASA Technical Reports Server (NTRS)

    McDonald, K. S.; Delp, M. D.; Fitts, R. H.

    1992-01-01

    The purpose of this study was to characterize the distribution of blood flow in the rat during hindlimb unweighting (HU) and post-HU standing and exercise and examine whether the previously reported elevation in anaerobic metabolism observed with contractile activity in the atrophied soleus muscle was caused by a reduced hindlimb blood flow. After either 15 days of HU or cage control, blood flow was measured with radioactive microspheres during unweighting, normal standing, and running on a treadmill (15 m/min). In another group of control and experimental animals, blood flow was measured during preexercise (PE) treadmill standing and treadmill running (15 m/min). Soleus muscle blood flow was not different between groups during unweighting, PE standing, and running at 15 m/min. Chronic unweighting resulted in the tendency for greater blood flow to muscles composed of predominantly fast-twitch glycolytic fibers. With exercise, blood flow to visceral organs was reduced compared with PE values in the control rats, whereas flow to visceral organs in 15-day HU animals was unaltered by exercise. These higher flows to the viscera and to muscles composed of predominantly fast-twitch glycolytic fibers suggest an apparent reduction in the ability of the sympathetic nervous system to distribute cardiac output after chronic HU. In conclusion, because 15 days of HU did not affect blood flow to the soleus during exercise, the increased dependence of the atrophied soleus on anerobic energy production during contractile activity cannot be explained by a reduced muscle blood flow.

  12. Ultrafast Ultrasound Imaging of Ocular Anatomy and Blood Flow

    PubMed Central

    Urs, Raksha; Ketterling, Jeffrey A.; Silverman, Ronald H.

    2016-01-01

    Purpose Ophthalmic ultrasound imaging is currently performed with mechanically scanned single-element probes. These probes have limited capabilities overall and lack the ability to image blood flow. Linear-array systems are able to detect blood flow, but these systems exceed ophthalmic acoustic intensity safety guidelines. Our aim was to implement and evaluate a new linear-array–based technology, compound coherent plane-wave ultrasound, which offers ultrafast imaging and depiction of blood flow at safe acoustic intensity levels. Methods We compared acoustic intensity generated by a 128-element, 18-MHz linear array operated in conventionally focused and plane-wave modes and characterized signal-to-noise ratio (SNR) and lateral resolution. We developed plane-wave B-mode, real-time color-flow, and high-resolution depiction of slow flow in postprocessed data collected continuously at a rate of 20,000 frames/s. We acquired in vivo images of the posterior pole of the eye by compounding plane-wave images acquired over ±10° and produced images depicting orbital and choroidal blood flow. Results With the array operated conventionally, Doppler modes exceeded Food and Drug Administration safety guidelines, but plane-wave modalities were well within guidelines. Plane-wave data allowed generation of high-quality compound B-mode images, with SNR increasing with the number of compounded frames. Real-time color-flow Doppler readily visualized orbital blood flow. Postprocessing of continuously acquired data blocks of 1.6-second duration allowed high-resolution depiction of orbital and choroidal flow over the cardiac cycle. Conclusions Newly developed high-frequency linear arrays in combination with plane-wave techniques present opportunities for the evaluation of ocular anatomy and blood flow, as well as visualization and analysis of other transient phenomena such as vessel wall motion over the cardiac cycle and saccade-induced vitreous motion. PMID:27428169

  13. Brain blood flow and blood pressure during hypoxia in the epaulette shark Hemiscyllium ocellatum, a hypoxia-tolerant elasmobranch.

    PubMed

    Söderström, V; Renshaw, G M; Nilsson, G E

    1999-04-01

    The key to surviving hypoxia is to protect the brain from energy depletion. The epaulette shark (Hemiscyllium ocellatum) is an elasmobranch able to resist energy depletion and to survive hypoxia. Using epi-illumination microscopy in vivo to observe cerebral blood flow velocity on the brain surface, we show that cerebral blood flow in the epaulette shark is unaffected by 2 h of severe hypoxia (0.35 mg O2 l-1 in the respiratory water, 24 C). Thus, the epaulette shark differs from other hypoxia- and anoxia-tolerant species studied: there is no adenosine-mediated increase in cerebral blood flow such as that occurring in freshwater turtles and cyprinid fish. However, blood pressure showed a 50 % decrease in the epaulette shark during hypoxia, indicating that a compensatory cerebral vasodilatation occurs to maintain cerebral blood flow. We observed an increase in cerebral blood flow velocity when superfusing the normoxic brain with adenosine (making sharks the oldest vertebrate group in which this mechanism has been found). The adenosine-induced increase in cerebral blood flow velocity was reduced by the adenosine receptor antagonist aminophylline. Aminophylline had no effect upon the maintenance of cerebral blood flow during hypoxia, however, indicating that adenosine is not involved in maintaining cerebral blood flow in the epaulette shark during hypoxic hypotension.

  14. Numerical simulation of the non-Newtonian blood flow through a mechanical aortic valve. Non-Newtonian blood flow in the aortic root

    NASA Astrophysics Data System (ADS)

    De Vita, F.; de Tullio, M. D.; Verzicco, R.

    2016-04-01

    This work focuses on the comparison between Newtonian and non-Newtonian blood flows through a bileaflet mechanical heart valve in the aortic root. The blood, in fact, is a concentrated suspension of cells, mainly red blood cells, in a Newtonian matrix, the plasma, and consequently its overall behavior is that of a non-Newtonian fluid owing to the action of the cells' membrane on the fluid part. The common practice, however, assumes the blood in large vessels as a Newtonian fluid since the shear rate is generally high and the effective viscosity becomes independent of the former. In this paper, we show that this is not always the case even in the aorta, the largest artery of the systemic circulation, owing to the pulsatile and transitional nature of the flow. Unexpectedly, for most of the pulsating cycle and in a large part of the fluid volume, the shear rate is smaller than the threshold level for the blood to display a constant effective viscosity and its shear thinning character might affect the system dynamics. A direct inspection of the various flow features has shown that the valve dynamics, the transvalvular pressure drop and the large-scale features of the flow are very similar for the Newtonian and non-Newtonian fluid models. On the other hand, the mechanical damage of the red blood cells (hemolysis), induced by the altered stress values in the flow, is larger for the non-Newtonian fluid model than for the Newtonian one.

  15. Computational Analysis of Human Blood Flow

    NASA Astrophysics Data System (ADS)

    Panta, Yogendra; Marie, Hazel; Harvey, Mark

    2009-11-01

    Fluid flow modeling with commercially available computational fluid dynamics (CFD) software is widely used to visualize and predict physical phenomena related to various biological systems. In this presentation, a typical human aorta model was analyzed assuming the blood flow as laminar with complaint cardiac muscle wall boundaries. FLUENT, a commercially available finite volume software, coupled with Solidworks, a modeling software, was employed for the preprocessing, simulation and postprocessing of all the models.The analysis mainly consists of a fluid-dynamics analysis including a calculation of the velocity field and pressure distribution in the blood and a mechanical analysis of the deformation of the tissue and artery in terms of wall shear stress. A number of other models e.g. T branches, angle shaped were previously analyzed and compared their results for consistency for similar boundary conditions. The velocities, pressures and wall shear stress distributions achieved in all models were as expected given the similar boundary conditions. The three dimensional time dependent analysis of blood flow accounting the effect of body forces with a complaint boundary was also performed.

  16. Optical measurement of blood flow in exercising skeletal muscle: a pilot study

    NASA Astrophysics Data System (ADS)

    Wang, Detian; Baker, Wesley B.; Parthasarathy, Ashwin B.; Zhu, Liguo; Li, Zeren; Yodh, Arjun G.

    2017-07-01

    Blood flow monitoring during rhythm exercising is very important for sports medicine and muscle dieases. Diffuse correlation spectroscopy(DCS) is a relative new invasive way to monitor blood flow but suffering from muscle fiber motion. In this study we focus on how to remove exercise driven artifacts and obtain accurate estimates of the increase in blood flow from exercise. Using a novel fast software correlator, we measured blood flow in forearm flexor muscles of N=2 healthy adults during handgrip exercise, at a sampling rate of 20 Hz. Combining the blood flow and acceleration data, we resolved the motion artifact in the DCS signal induced by muscle fiber motion, and isolated the blood flow component of the signal from the motion artifact. The results show that muscle fiber motion strongly affects the DCS signal, and if not accounted for, will result in an overestimate of blood flow more than 1000%. Our measurements indicate rapid dilation of arterioles following exercise onset, which enabled blood flow to increase to a plateau of 200% in 10s. The blood flow also rapidly recovered to baseline following exercise in 10s. Finally, preliminary results on the dependence of blood flow from exercise intensity changes will be discussed.

  17. Gestational Dietary Protein Is Associated with Sex Specific Decrease in Blood Flow, Fetal Heart Growth and Post-Natal Blood Pressure of Progeny

    PubMed Central

    2015-01-01

    Study Overview The incidence of adverse pregnancy outcomes is higher in pregnancies where the fetus is male. Sex specific differences in feto-placental perfusion indices identified by Doppler assessment have recently been associated with placental insufficiency and fetal growth restriction. This study aims to investigate sex specific differences in placental perfusion and to correlate these changes with fetal growth. It represents the largest comprehensive study under field conditions of uterine hemodynamics in a monotocous species, with a similar long gestation period to the human. Primiparous 14mo heifers in Australia (n=360) and UK (n=180) were either individually or group fed, respectively, diets with differing protein content (18, 14, 10 or 7% crude protein (CP)) from 60d prior to 98 days post conception (dpc). Fetuses and placentae were excised at 98dpc (n = 48). Fetal development an median uterine artery blood flow were assessed monthly from 36dpc until term using B-mode and Doppler ultrasonography. MUA blood flow to the male feto-placental unit increased in early pregnancy associated with increased fetal growth. Protein restriction before and shortly after conception (-60d up to 23dpc) increased MUA diameter and indices of velocity during late pregnancy, reduced fetal heart weight in the female fetus and increased heart rate at birth, but decreased systolic blood pressure at six months of age. Conclusion and Significance Sex specific differences both in feto-placental Doppler perfusion indices and response of these indices to dietary perturbations were observed. Further, maternal diet affected development of fetal cardiovascular system associated with altered fetal haemodynamics in utero, with such effects having a sex bias. The results from this study provide further insight into the gender specific circulatory differences present in the fetal period and developing cardiovascular system. PMID:25915506

  18. Gestational dietary protein is associated with sex specific decrease in blood flow, fetal heart growth and post-natal blood pressure of progeny.

    PubMed

    Hernandez-Medrano, Juan H; Copping, Katrina J; Hoare, Andrew; Wapanaar, Wendela; Grivell, Rosalie; Kuchel, Tim; Miguel-Pacheco, Giuliana; McMillen, I Caroline; Rodgers, Raymond J; Perry, Viv E A

    2015-01-01

    The incidence of adverse pregnancy outcomes is higher in pregnancies where the fetus is male. Sex specific differences in feto-placental perfusion indices identified by Doppler assessment have recently been associated with placental insufficiency and fetal growth restriction. This study aims to investigate sex specific differences in placental perfusion and to correlate these changes with fetal growth. It represents the largest comprehensive study under field conditions of uterine hemodynamics in a monotocous species, with a similar long gestation period to the human. Primiparous 14 mo heifers in Australia (n=360) and UK (n=180) were either individually or group fed, respectively, diets with differing protein content (18, 14, 10 or 7% crude protein (CP)) from 60 d prior to 98 days post conception (dpc). Fetuses and placentae were excised at 98 dpc (n = 48). Fetal development an median uterine artery blood flow were assessed monthly from 36 dpc until term using B-mode and Doppler ultrasonography. MUA blood flow to the male feto-placental unit increased in early pregnancy associated with increased fetal growth. Protein restriction before and shortly after conception (-60 d up to 23 dpc) increased MUA diameter and indices of velocity during late pregnancy, reduced fetal heart weight in the female fetus and increased heart rate at birth, but decreased systolic blood pressure at six months of age. Sex specific differences both in feto-placental Doppler perfusion indices and response of these indices to dietary perturbations were observed. Further, maternal diet affected development of fetal cardiovascular system associated with altered fetal haemodynamics in utero, with such effects having a sex bias. The results from this study provide further insight into the gender specific circulatory differences present in the fetal period and developing cardiovascular system.

  19. Thermographic venous blood flow characterization with external cooling stimulation

    NASA Astrophysics Data System (ADS)

    Saxena, Ashish; Ng, E. Y. K.; Raman, Vignesh

    2018-05-01

    Experimental characterization of blood flow in a human forearm is done with the application of continuous external cooling based active thermography method. Qualitative and quantitative detection of the blood vessel in a thermal image is done, along with the evaluation of blood vessel diameter, blood flow direction, and velocity in the target blood vessel. Subtraction based image manipulation is performed to enhance the feature contrast of the thermal image acquired after the removal of external cooling. To demonstrate the effect of occlusion diseases (obstruction), an external cuff based occlusion is applied after the removal of cooling and its effect on the skin rewarming is studied. Using external cooling, a transit time method based blood flow velocity estimation is done. From the results obtained, it is evident that an external cooling based active thermography method can be used to develop a diagnosis tool for superficial blood vessel diseases.

  20. The effects of water-based exercise in combination with blood flow restriction on strength and functional capacity in post-menopausal women.

    PubMed

    Araújo, Joamira P; Neto, Gabriel R; Loenneke, Jeremy P; Bemben, Michael G; Laurentino, Gilberto C; Batista, Gilmário; Silva, Júlio C G; Freitas, Eduardo D S; Sousa, Maria S C

    2015-12-01

    Water-based exercise and low-intensity exercise in combination with blood flow restriction (BFR) are two methods that have independently been shown to improve muscle strength in those of advancing age. The objective of this study was to assess the long-term effect of water-based exercise in combination with BFR on maximum dynamic strength and functional capacity in post-menopausal women. Twenty-eight women underwent an 8-week water-based exercise program. The participants were randomly allocated to one of the three groups: (a) water exercise only, (b) water exercise + BFR, or (c) a non-exercise control group. Functional capacity (chair stand test, timed up and go test, gait speed, and dynamic balance) and strength testing were tested before and after the 8-week aquatic exercise program. The main findings were as follows: (1) water-based exercise in combination with BFR significantly increased the lower limb maximum strength which was not observed with water-based exercise alone and (2) water-based exercise, regardless of the application of BFR, increased functional performance measured by the timed up and go test over a control group. Although we used a healthy population in the current study, these findings may have important implications for those who may be contraindicated to using traditional resistance exercise. Future research should explore this promising modality in these clinical populations.

  1. Three-dimensional multi-scale model of deformable platelets adhesion to vessel wall in blood flow

    PubMed Central

    Wu, Ziheng; Xu, Zhiliang; Kim, Oleg; Alber, Mark

    2014-01-01

    When a blood vessel ruptures or gets inflamed, the human body responds by rapidly forming a clot to restrict the loss of blood. Platelets aggregation at the injury site of the blood vessel occurring via platelet–platelet adhesion, tethering and rolling on the injured endothelium is a critical initial step in blood clot formation. A novel three-dimensional multi-scale model is introduced and used in this paper to simulate receptor-mediated adhesion of deformable platelets at the site of vascular injury under different shear rates of blood flow. The novelty of the model is based on a new approach of coupling submodels at three biological scales crucial for the early clot formation: novel hybrid cell membrane submodel to represent physiological elastic properties of a platelet, stochastic receptor–ligand binding submodel to describe cell adhesion kinetics and lattice Boltzmann submodel for simulating blood flow. The model implementation on the GPU cluster significantly improved simulation performance. Predictive model simulations revealed that platelet deformation, interactions between platelets in the vicinity of the vessel wall as well as the number of functional GPIbα platelet receptors played significant roles in platelet adhesion to the injury site. Variation of the number of functional GPIbα platelet receptors as well as changes of platelet stiffness can represent effects of specific drugs reducing or enhancing platelet activity. Therefore, predictive simulations can improve the search for new drug targets and help to make treatment of thrombosis patient-specific. PMID:24982253

  2. Effect of age on cerebral blood flow during hypothermic cardiopulmonary bypass

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brusino, F.G.; Reves, J.G.; Smith, L.R.

    1989-04-01

    Cerebral blood flow was measured in 20 patients by xenon 133 clearance methodology during nonpulsatile hypothermic cardiopulmonary bypass to determine the effect of age on regional cerebral blood flow during these conditions. Measurements of cerebral blood flow at varying perfusion pressures were made in patients arbitrarily divided into two age groups at nearly identical nasopharyngeal temperature, hematocrit value, and carbon dioxide tension and with equal cardiopulmonary bypass flows of 1.6 L/min/m2. The range of mean arterial pressure was 30 to 110 mm Hg for group I (less than or equal to 50 years of age) and 20 to 90 mmmore » Hg for group II (greater than or equal to 65 years of age). There was no significant difference (p = 0.32) between the mean arterial pressure in group I (54 +/- 28 mm Hg) and that in group II (43 +/- 21 mm Hg). The range of cerebral blood flow was 14.8 to 29.2 ml/100 gm/min for group I and 13.8 to 37.5 ml/100 gm/min for group II. There was no significant difference (p = 0.37) between the mean cerebral blood flow in group I (21.5 +/- 4.6 ml/100 gm/min) and group II (24.3 +/- 8.1 ml/100 gm/min). There was a poor correlation between mean arterial pressure and cerebral blood flow in both groups: group I, r = 0.16 (p = 0.67); group II, r = 0.5 (p = 0.12). In 12 patients, a second cerebral blood flow measurements was taken to determine the effect of mean arterial pressure on cerebral blood flow in the individual patient. Changes in mean arterial pressure did not correlate with changes in cerebral blood flow (p less than 0.90). We conclude that age does not alter cerebral blood flow and that cerebral blood flow autoregulation is preserved in elderly patients during nonpulsatile hypothermic cardiopulmonary bypass.« less

  3. Distribution of intrarenal blood flow consequent to left atrial balloon inflation.

    PubMed

    Passmore, J C; Stremel, R W; Hock, C E; Allen, R L; Bradford, W B

    1985-01-01

    The effects of inflation of a balloon within, and consequent distension of, the left atrium (LABI, left atrial balloon inflation) on total renal blood flow (RBF) and intrarenal blood flow distribution were measured and compared to values obtained from another group of dogs that were hemorrhaged (HEM) to the same level of hypotension as that produced by LABI, a mean systemic arterial pressure of 88 mm Hg. Kidney wt/kg, RBF/kg body wt, and urine flow were markedly reduced during the hemorrhage period in the HEM group when compared to values obtained during the experimental period for the LABI group. Data from the freeze-dissection (133Xe) analysis revealed that the percentage distribution of blood flow as renal outer cortical (OC) blood flow was less (26%) in the HEM group than in the LABI group (50%), this latter value being very similar to that of control dogs that experienced no hypotension (49%). LABI better maintains OC blood flow and urine flow when compared to HEM at the same systemic blood pressure, suggesting a role for cardiopulmonary receptors in reflex sympathetic control of renal blood flow distribution during hypotension.

  4. Altered Regional Cerebral Blood Flow in Idiopathic Hypersomnia.

    PubMed

    Boucetta, Soufiane; Montplaisir, Jacques; Zadra, Antonio; Lachapelle, Francis; Soucy, Jean-Paul; Gravel, Paul; Dang-Vu, Thien Thanh

    2017-10-01

    Idiopathic hypersomnia is characterized by excessive daytime sleepiness, despite normal or long sleep time. Its pathophysiological mechanisms remain unclear. This pilot study aims at characterizing the neural correlates of idiopathic hypersomnia using single photon emission computed tomography. Thirteen participants with idiopathic hypersomnia and 16 healthy controls were scanned during resting wakefulness using a high-resolution single photon emission computed tomography scanner with 99mTc-ethyl cysteinate dimer to assess cerebral blood flow. The main analysis compared regional cerebral blood flow distribution between the two groups. Exploratory correlations between regional cerebral blood flow and clinical characteristics evaluated the functional correlates of those brain perfusion patterns. Significance was set at p < .05 after correction for multiple comparisons. Participants with idiopathic hypersomnia showed regional cerebral blood flow decreases in medial prefrontal cortex and posterior cingulate cortex and putamen, as well as increases in amygdala and temporo-occipital cortices. Lower regional cerebral blood flow in the medial prefrontal cortex was associated with higher daytime sleepiness. These preliminary findings suggest that idiopathic hypersomnia is characterized by functional alterations in brain areas involved in the modulation of vigilance states, which may contribute to the daytime symptoms of this condition. The distribution of regional cerebral blood flow changes was reminiscent of the patterns associated with normal non-rapid-eye-movement sleep, suggesting the possible presence of incomplete sleep-wake transitions. These abnormalities were strikingly distinct from those induced by acute sleep deprivation, suggesting that the patterns seen here might reflect a trait associated with idiopathic hypersomnia rather than a non-specific state of sleepiness. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep

  5. Non-invasive determination of instantaneous brachial blood flow using the oscillometric method.

    PubMed

    Liu, Shing-Hong; Wang, Jia-Jung; Cheng, Da-Chuan

    2009-08-01

    The oscillometric method has been widely used to measure arterial systolic and diastolic blood pressures, but its potential for arterial blood flow measurements still remains to be explored. The aim of this study was to non-invasively determine arterial blood flow using an oscillometric blood flow measurement system. The system consists of a pneumatic elastic cuff, an air-pumping motor, a releaser valve, a pressure transducer, and an airflow meter. To build a non-linear cuff model, we measured airflow pumped into the pneumatic cuff and cuff pressure using an airflow meter and pressure transducer during the inflation period, respectively. During the deflation period, only the pressure transducer was used to record cuff pressure. Based on the cuff model, the oscillometric blood flow waveform was obtained by integrating the oscillometric pressure waveform. We compared arterial blood flow derived from the maximum amplitude of the oscillometric blood flow waveform with Doppler-measured blood flow calculated with the diameters and blood velocities of the brachial arteries in 32 subjects who underwent diagnostic evaluations for peripheral arterial embolism. A linear correlation coefficient of r = 0.716 was found between the oscillometry- and Doppler-based blood flow measurements in the 32 subjects. These results suggest that blood flow passing through the brachial artery can be quantified non-invasively using the oscillometric approach after appropriate calibration.

  6. Blood flow to the promontory in cochlear otosclerosis.

    PubMed

    Nakashima, T; Sone, M; Fujii, H; Teranishi, M; Yamamoto, H; Otake, H; Sugiura, M; Naganawa, S

    2006-04-01

    To investigate Schwartze sign with measurements of blood flow to the promontory in patients with cochlear otosclerosis. Prospective clinical study. Tertiary referral centre. Five patients with cochlear otosclerosis and five control subjects. Significant decalcification around the cochlea was observed by computed tomography (CT) in patients with cochlear otosclerosis. However, no recognizable lesion was observed at the oval window in two patients. One patient had mixed hearing loss and four patients had sensorineural hearing loss without an air-bone gap. The relationship between CT findings and the presence or absence of Schwartze sign was investigated. Blood flow to the promontory was measured through the tympanic membrane using laser speckle flowgraphy and laser Doppler flowmetry. The Schwartze sign correlated significantly with otosclerotic lesions invading the promontory. Patients with otosclerosis exhibited elevated and pulsating blood flow to the promontory with the Schwartze sign. Computed tomography demonstrated that cochlear otosclerosis can exist without the oval window lesion. Schwartze sign can be used as a sign of the otosclerotic invasion to the promontory. The reddening of the Schwartze sign is likely due to increased blood flow.

  7. Microprobes For Blood Flow Measurements In Tissue And Small Vessels

    NASA Astrophysics Data System (ADS)

    Oberg, P. A.; Salerud, E. G.

    1988-04-01

    Laser Doppler flowmetry is a method for the continuous and non-invasive recording of tissue blood flow. The method has already proved to be advantageous in a number of clinical as well as theoretical medical disciplines. In dermatology, plastic- and gastrointestinal surgery laser Doppler measurements have substantially contributed to increase knowledge of microvascular perfusion. In experimental medicine, the method has been used in the study of a great variety of microvascular problems. Spontaneous rhythmical variations, spatial and temporal fluctuations in human skin blood flow are mentioned as examples of problem areas in which new knowledge has been generated. The method has facilitated further investigations of the nature of spongeous bone blood flow, testis and kidney cortex blood flow. Recently we have showed that a variant of the laser Doppler method principle, using a single optical fiber, can be advantageous in deep tissue measurements. With this method laser light is transmitted bidirectionally in a single fiber. The tissue trauma which affects blood flow can be minimized by introducing small diameter fibers (0.1-0.5 mm). A special set-up utilizing the same basic principle has been used for the recording of blood flow in small vessels.

  8. Segmental Blood Flow and Hemodynamic State of Lymphedematous and Nonlymphedematous Arms

    PubMed Central

    Montgomery, Leslie D.; Dietrich, Mary S.; Armer, Jane M.; Stewart, B. R.

    2011-01-01

    Abstract Background Findings regarding the influence hemodynamic factors, such as increased arterial blood flow or venous abnormalities, on breast cancer treatment-related lymphedema are mixed. The purpose of this study was to compare segmental arterial blood flow, venous blood return, and blood volumes between breast cancer survivors with treatment-related lymphedema and healthy normal individuals without lymphedema. Methods and Results A Tetrapolar High Resolution Impedance Monitor and Cardiotachometer were used to compare segmental arterial blood flow, venous blood return, and blood volumes between breast cancer survivors with treatment-related lymphedema and healthy normal volunteers. Average arterial blood flow in lymphedema-affected arms was higher than that in arms of healthy normal volunteers or in contralateral nonlymphedema affected arms. Time of venous outflow period of blood flow pulse was lower in lymphedema-affected arms than in healthy normal or lymphedema nonaffected arms. Amplitude of the venous component of blood flow pulse signal was lower in lymphedema-affected arms than in healthy or lymphedema nonaffected arms. Index of venular tone was also lower in lymphedema-affected arms than healthy or lymphedema nonaffected arms. Conclusions Both arterial and venous components may be altered in the lymphedema-affected arms when compared to healthy normal arms and contralateral arms in the breast cancer survivors. PMID:21417765

  9. Coronary blood flow during cardiopulmonary resuscitation in swine

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bellamy, R.F.; DeGuzman, L.R.; Pedersen, D.C.

    1984-01-01

    Recent papers have raised doubt as to the magnitude of coronary blood flow during closed-chest cardiopulmonary resuscitation. We will describe experiments that concern the methods of coronary flow measurement during cardiopulmonary resuscitation. Nine anesthetized swine were instrumented to allow simultaneous measurements of coronary blood flow by both electromagnetic cuff flow probes and by the radiomicrosphere technique. Cardiac arrest was caused by electrical fibrillation and closed-chest massage was performed by a Thumper (Dixie Medical Inc., Houston). The chest was compressed transversely at a rate of 66 strokes/min. Compression occupied one-half of the massage cycle. Three different Thumper piston strokes were studied:more » 1.5, 2, and 2.5 inches. Mean aortic pressure and total systemic blood flow measured by the radiomicrosphere technique increased as Thumper piston stroke was lengthened (mean +/- SD): 1.5 inch stroke, 23 +/- 4 mm Hg, 525 +/- 195 ml/min; 2 inch stroke, 33 +/- 5 mm Hg, 692 +/- 202 ml/min; 2.5 inch stroke, 40 +/- 6 mm Hg, 817 +/- 321 ml/min. Both methods of coronary flow measurement (electromagnetic (EMF) and radiomicrosphere (RMS)) gave similar results in technically successful preparations (data expressed as percent prearrest flow mean +/- 1 SD): 1.5 inch stroke, EMF 12 +/- 5%, RMS 16 +/- 5%; 2 inch stroke, EMF 30 +/- 6%, RMS 26 +/- 11%; 2.5 inch stroke, EMF 50 +/- 12%, RMS 40 +/- 20%. The phasic coronary flow signal during closed-chest compression indicated that all perfusion occurred during the relaxation phase of the massage cycle. We concluded that coronary blood flow is demonstrable during closed-chest massage, but that the magnitude is unlikely to be more than a fraction of normal.« less

  10. Limb Blood Flow After Class 4 Laser Therapy

    PubMed Central

    Larkin, Kelly A.; Martin, Jeffrey S.; Zeanah, Elizabeth H.; True, Jerry M.; Braith, Randy W.; Borsa, Paul A.

    2012-01-01

    Context: Laser therapy is purported to improve blood flow in soft tissues. Modulating circulation would promote healing by controlling postinjury ischemia, hypoxia, edema, and secondary tissue damage. However, no studies have quantified these responses to laser therapy. Objective: To determine a therapeutic dose range for laser therapy for increasing blood flow to the forearm. Design: Crossover study. Setting: Controlled laboratory setting. Patients or Other Participants: Ten healthy, college-aged men (age = 20.80 ± 2.16 years, height = 177.93 ± 3.38 cm, weight = 73.64 ± 9.10 kg) with no current history of injury to the upper extremity or cardiovascular conditions. Intervention(s): A class 4 laser device was used to treat the biceps brachii muscle. Each grid point was treated for 3 to 4 seconds, for a total of 4 minutes. Each participant received 4 doses of laser therapy: sham, 1 W, 3 W, and 6 W. Main Outcome Measure(s): The dependent variables were changes in blood flow, measured using venous occlusion plethysmography. We used a repeated-measures analysis of variance to analyze changes in blood flow for each dose at 2, 3, and 4 minutes and at 1, 2, 3, 4, and 5 minutes after treatment. The Huynh-Feldt test was conducted to examine differences over time. Results: Compared with baseline, blood flow increased over time with the 3-W treatment (F3,9 = 3.468, P < .011) at minute 4 of treatment (2.417 ± 0.342 versus 2.794 ± 0.351 mL/min per 100 mL tissue, P = .032), and at 1 minute (2.767 ± 0.358 mL/min per 100 mL tissue, P < .01) and 2 minutes (2.657 ± 0.369 mL/min per 100 mL tissue, P = .022) after treatment. The sham, 1-W, and 6-W treatment doses did not change blood flow from baseline at any time point. Conclusions: Laser therapy at the 3-W (360-J) dose level was an effective treatment modality to increase blood flow in the soft tissues. PMID:22488283

  11. Influence of Dai-kenchu-to (DKT) on human portal blood flow.

    PubMed

    Ogasawara, Takashi; Morine, Yuji; Ikemoto, Tetsuya; Imura, Satoru; Fujii, Masahiko; Soejima, Yuji; Shimada, Mitsuo

    2008-01-01

    Dai-kenchu-to (DKT) is known as an herbal medicine used for postoperative ileus. However, no report exists about the effect of DKT on portal blood flow. The aim of this study is to clarify the influence of DKT on portal blood flow. To healthy volunteers (Healthy; n = 6), cirrhotic patients (Cirrhosis; n = 7) and liver-transplant patients (LTx; n = 3), DKT (2.5g) with 100mL of warm water was orally administrated in the DKT group, and only warm water was administrated in the control group. The portal blood flow rate (M-VEL: cm/sec.) and portal blood flow (Flow volume: mL/min.) was measured each time after administration using an ultrasonic Doppler method. Furthermore, the arterial blood pressure and heart rate was measured at the same time points. In the DKT group, a significant increase of M-VEL (120%) and flow volume (150%) 30 minutes after administration was observed in both Healthy and Cirrhosis in comparison with the control group. In LTx, there was also a significant increase of flow volume (128%) 30 minutes after administration. However, there was no change in average blood pressure and heart rate in all groups. DKT increases portal blood flow in early phase after oral administration without any significant changes in the blood pressure and heart rate.

  12. Investigation of spiral blood flow in a model of arterial stenosis.

    PubMed

    Paul, Manosh C; Larman, Arkaitz

    2009-11-01

    The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system [Stonebridge PA, Brophy CM. Spiral laminar flow in arteries? Lancet 1991; 338: 1360-1]. We investigate the effects of the spiral blood flow in a model of three-dimensional arterial stenosis with a 75% cross-sectional area reduction at the centre by means of computational fluid dynamics (CFD) techniques. The standard k-omega model is employed for simulation of the blood flow for the Reynolds number of 500 and 1000. We find that for Re=500 the spiral component of the blood flow increases both the total pressure and velocity of the blood, and some significant differences are found between the wall shear stresses of the spiral and non-spiral induced flow downstream of the stenosis. The turbulent kinetic energy is reduced by the spiral flow as it induces the rotational stabilities in the forward flow. For Re=1000 the tangential component of the blood velocity is most influenced by the spiral speed, but the effect of the spiral flow on the centreline turbulent kinetic energy and shear stress is mild. The results of the effects of the spiral flow are discussed in the paper along with the relevant pathological issues.

  13. Effect of sumatriptan on cerebral blood flow in the baboon model.

    PubMed

    Oliver, D W; Dormehl, I C; Hugo, N

    1994-08-01

    Changes in cerebral blood flow are implicated to be important in the pathophysiology of migraine. Furthermore, serotonin (5-HT) is known to be the most important substance in the etiology of migraine. Sumatriptan (CAS 103628-46-2), a 5-HTID receptor agonist was recently introduced in the treatment of migraine. In the present study a baboon model was used to investigate the changes in cerebral blood flow due to anaesthesia and pharmacological interventions using 99mTc-labelled hexamethylpropylene amine oxime (99mTc-HMPAO) and single photon emission computed tomography (SPECT). The effect of sumatriptan on cerebral blood flow was investigated after 10 min and again after 23 min, with the animal under anaesthesia, i.e. induction with ketamine and maintenance on thiopental. Sumatriptan did not alter the cerebral blood flow during the 10 min procedure. However, sumatriptan reversed the increased cerebral blood flow due to the prolonged anaesthesia (23 min), lowering the cerebral blood flow by more than 20%. No significant changes in the biochemical parameters (blood pressure, heart rate, pO2 and pCO2) were observed. These results also suggest that sumatriptan reverses the increased cerebral blood flow most likely via 5-HTID receptor stimulation.

  14. Muscle blood flow at onset of dynamic exercise in humans.

    PubMed

    Rådegran, G; Saltin, B

    1998-01-01

    To evaluate the temporal relationship between blood flow, blood pressure, and muscle contractions, we continuously measured femoral arterial inflow with ultrasound Doppler at onset of passive exercise and voluntary, one-legged, dynamic knee-extensor exercise in humans. Blood velocity and inflow increased (P < 0.006) with the first relaxation of passive and voluntary exercise, whereas the arterial-venous pressure difference was unaltered [P = not significant (NS)]. During steady-state exercise, and with arterial pressure as a superimposed influence, blood velocity was affected by the muscle pump, peaking (P < 0.001) at approximately 2.5 +/- 0.3 m/s as the relaxation coincided with peak systolic arterial blood pressure; blood velocity decreased (P < 0.001) to 44.2 +/- 8.6 and 28.5 +/- 5.5% of peak velocity at the second dicrotic and diastolic blood pressure notches, respectively. Mechanical hindrance occurred (P < 0.001) during the contraction phase at blood pressures less than or equal to that at the second dicrotic notch. The increase in blood flow (Q) was characterized by a one-component (approximately 15% of peak power output), two-component (approximately 40-70% of peak power output), or three-component exponential model (> or = 75% of peak power output), where Q(t) = Qpassive + delta Q1.[1 - e-(t - TD1/tau 1)]+ delta Q2.[1 - e-(t - TD2/tau 2)]+ delta Q3.[1 - e-(t - TD3/tau 3)]; Qpassive, the blood flow during passive leg movement, equals 1.17 +/- 0.11 l/min; TD is the onset latency; tau is the time constant; delta Q is the magnitude of blood flow rise; and subscripts 1-3 refer to the first, second, and third components of the exponential model, respectively. The time to reach 50% of the difference between passive and voluntary asymptotic blood flow was approximately 2.2-8.9 s. The blood flow leveled off after approximately 10-150 s, related to the power outputs. It is concluded that the elevation in blood flow with the first duty cycle(s) is due to muscle

  15. Effect of warming and flow rate conditions of blood warmers on red blood cell integrity.

    PubMed

    Poder, T G; Pruneau, D; Dorval, J; Thibault, L; Fisette, J-F; Bédard, S K; Jacques, A; Beauregard, P

    2016-11-01

    Fluid warmers are routinely used to reduce the risk of hypothermia and cardiac complications associated with the infusion of cold blood products. However, warming blood products could generate haemolysis. This study was undertaken to compare the impact of temperature of blood warmers on the per cent haemolysis of packed red blood cells (RBCs) heated at different flow rates as well as non-flow conditions. Infusion warmers used were calibrated at 41·5°C ± 0·5°C and 37·5°C ± 0·5°C. Cold RBC units stored at 4°C in AS-3 (n = 30), aged 30-39 days old, were divided into half units before being allocated under two different scenarios (i.e. infusion pump or syringe). Blood warmers were effective to warm cold RBCs to 37·5°C or 41·5°C when used in conjunction with an infusion pump at flow rate up to 600 ml/h. However, when the warmed blood was held in a syringe for various periods of time, such as may occur in neonatal transfusions, the final temperature was below the expected requirements with measurement as low as 33·1°C. Increasing the flow with an infusion pump increased haemolysis in RBCs from 0·2% to up to 2·1% at a flow rate of 600 ml/h regardless of the warming device used (P < 0·05). No relevant increase of haemolysis was observed using a syringe. The use of a blood warmer adjusted to 41·5°C is probably the best choice for reducing the risk of hypothermia for the patient without generating haemolysis. However, we should be cautious with the use of an infusion pump for RBC transfusion, particularly at high flow rates. © 2016 International Society of Blood Transfusion.

  16. Increased blood flow and vasculature in solar lentigo.

    PubMed

    Hasegawa, Kiyotaka; Fujiwara, Rumiko; Sato, Kiyoshi; Park, Ji-Youn; Kim, Sang Jin; Kim, Misun; Kang, Hee Young

    2016-10-01

    Solar lentigo (SL) is a hallmark of ultraviolet (UV)-induced photoaged skin and growing evidence implicates blood vessels in UV-associated pigmentation. In this study, we investigated whether the vasculatures are modified in SL. Twenty-five women with facial SL were enrolled and colorimetric and blood flow studies were performed. There was a significant increase in erythema which was associated with increased blood flow in the lesional skin compared with perilesional normal skin. Immunohistochemical studies with 24 facial SL biopsies consistently revealed a significant increase in vessel density accompanied by increased levels of vascular endothelial growth factor expression. CD68 immunoreactivity was significantly higher in lesional skin suggesting increased macrophage infiltration in SL. In conclusion, SL is characterized by increased blood flow and vasculature. These findings suggest the possible influence of the characteristics of vasculature on development of SL. © 2016 Japanese Dermatological Association.

  17. Extensional flow of blood analog solutions in microfluidic devices

    PubMed Central

    Sousa, P. C.; Pinho, F. T.; Oliveira, M. S. N.; Alves, M. A.

    2011-01-01

    In this study, we show the importance of extensional rheology, in addition to the shear rheology, in the choice of blood analog solutions intended to be used in vitro for mimicking the microcirculatory system. For this purpose, we compare the flow of a Newtonian fluid and two well-established viscoelastic blood analog polymer solutions through microfluidic channels containing both hyperbolic and abrupt contractions∕expansions. The hyperbolic shape was selected in order to impose a nearly constant strain rate at the centerline of the microchannels and achieve a quasihomogeneous and strong extensional flow often found in features of the human microcirculatory system such as stenoses. The two blood analog fluids used are aqueous solutions of a polyacrylamide (125 ppm w∕w) and of a xanthan gum (500 ppm w∕w), which were characterized rheologically in steady-shear flow using a rotational rheometer and in extension using a capillary breakup extensional rheometer (CaBER). Both blood analogs exhibit a shear-thinning behavior similar to that of whole human blood, but their relaxation times, obtained from CaBER experiments, are substantially different (by one order of magnitude). Visualizations of the flow patterns using streak photography, measurements of the velocity field using microparticle image velocimetry, and pressure-drop measurements were carried out experimentally for a wide range of flow rates. The experimental results were also compared with the numerical simulations of the flow of a Newtonian fluid and a generalized Newtonian fluid with shear-thinning behavior. Our results show that the flow patterns of the two blood analog solutions are considerably different, despite their similar shear rheology. Furthermore, we demonstrate that the elastic properties of the fluid have a major impact on the flow characteristics, with the polyacrylamide solution exhibiting a much stronger elastic character. As such, these properties must be taken into account in the

  18. Synchronization patterns in cerebral blood flow and peripheral blood pressure under minor stroke

    NASA Astrophysics Data System (ADS)

    Chen, Zhi; Ivanov, Plamen C.; Hu, Kun; Stanley, H. Eugene; Novak, Vera

    2003-05-01

    Stroke is a leading cause of death and disability in the United States. The autoregulation of cerebral blood flow that adapts to changes in systemic blood pressure is impaired after stroke. We investigate blood flow velocities (BFV) from right and left middle cerebral arteries (MCA) and beat-to-beat blood pressure (BP) simultaneously measured from the finger, in 13 stroke and 11 healthy subjects using the mean value statistics and phase synchronization method. We find an increase in the vascular resistance and a much stronger cross-correlation with a time lag up to 20 seconds with the instantaneous phase increment of the BFV and BP signals for the subjects with stroke compared to healthy subjects.

  19. Follicle vascularity coordinates corpus luteum blood flow and progesterone production.

    PubMed

    de Tarso, S G S; Gastal, G D A; Bashir, S T; Gastal, M O; Apgar, G A; Gastal, E L

    2017-03-01

    Colour Doppler ultrasonography was used to compare the ability of preovulatory follicle (POF) blood flow and its dimensions to predict the size, blood flow and progesterone production capability of the subsequent corpus luteum (CL). Cows (n=30) were submitted to a synchronisation protocol. Follicles ≥7mm were measured and follicular wall blood flow evaluated every 12h for approximately 3.5 days until ovulation. After ovulation, cows were scanned daily for 8 days and similar parameters were evaluated for the CL. Blood samples were collected and plasma progesterone concentrations quantified. All parameters were positively correlated. Correlation values ranged from 0.26 to 0.74 on data normalised to ovulation and from 0.31 to 0.74 on data normalised to maximum values. Correlations between calculated ratios of both POF and CL in data normalised to ovulation and to maximum values ranged from moderate (0.57) to strong (0.87). Significant (P<0.0001) linear regression analyses were seen in all comparisons. In conclusion, higher correlations were observed between the dimensions of POF and/or CL and blood flow of both structures, as well as POF and/or CL blood flow with plasma progesterone concentrations of the resultant CL. These findings indicate that follicle vascularity coordinates CL blood flow and progesterone production in synchronised beef cows.

  20. Amino Acids That Centrally Influence Blood Pressure and Regional Blood Flow in Conscious Rats

    PubMed Central

    Takemoto, Yumi

    2012-01-01

    Functional roles of amino acids have increasingly become the focus of research. This paper summarizes amino acids that influence cardiovascular system via the brain of conscious rats. This paper firstly describes why amino acids are selected and outlines how the brain regulates blood pressure and regional blood flow. This section includes a concise history of amino acid neurotransmitters in cardiovascular research and summarizes brain areas where chemical stimulations produce blood pressure changes mainly in anesthetized animals. This is followed by comments about findings regarding several newly examined amino acids with intracisternal stimulation in conscious rats that produce changes in blood pressure. The same pressor or depressor response to central amino acid stimulations can be produced by distinct mechanisms at central and peripheral levels, which will be briefly explained. Thereafter, cardiovascular actions of some of amino acids at the mechanism level will be discussed based upon findings of pharmacological and regional blood flow measurements. Several examined amino acids in addition to the established neurotransmitter amino acids appear to differentially activate brain structures to produce changes in blood pressure and regional blood flows. They may have physiological roles in the healthy brain, but pathological roles in the brain with cerebral vascular diseases such as stroke where the blood-brain barrier is broken. PMID:22690328

  1. Blood Flow Modulation of Vascular Dynamics

    PubMed Central

    Lee, Juhyun; Sevag Packard, René R.; Hsiai, Tzung K.

    2015-01-01

    Purpose of review Blood flow is intimately linked with cardiovascular development, repair, and dysfunction. The current review will build on the fluid mechanical principle underlying hemodynamic shear forces, mechanotransduction, and metabolic effects. Recent findings Pulsatile flow produces both time- (∂τ /∂t)and spatial-varying shear stress (∂τ /∂x) to modulate vascular oxidative stress and inflammatory response with pathophysiological significance to atherosclerosis. The characteristics of hemodynamic shear forces; namely, steady laminar (∂τ /∂t= 0), pulsatile (PSS: unidirectional forward flow), and oscillatory shear stress (OSS: bidirectional with a near net 0 forward flow) modulate mechano-signal transduction to influence metabolic effects on vascular endothelial function. Atheroprotective PSS promotes anti-oxidant, anti-inflammatory, and anti-thrombotic responses, whereas atherogenic OSS induces NADPH oxidase–JNK signaling to increase mitochondrial superoxide production, protein degradation of manganese superoxide dismutase (MnSOD), and post-translational protein modifications of LDL particles in the disturbed flow-exposed regions of vasculature. In the era of tissue regeneration, shear stress has been implicated in re-activation of developmental genes; namely, Wnt and Notch signaling, for vascular development and repair. Summary Blood flow imparts a dynamic continuum from vascular development to repair. Augmentation of PSS confers atheroprotection and re-activation of developmental signaling pathways for regeneration. PMID:26218416

  2. Cerebral blood flow changes during sodium-lactate-induced panic attacks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stewart, R.S.; Devous, M.D. Sr.; Rush, A.J.

    1988-04-01

    Dynamic single-photon emission computed axial tomography (CAT) with inhaled xenon-133 was used to measure regional cerebral blood flow in 10 drug-free patients with DSM-III-diagnosed panic disorder and in five normal control subjects. All subjects underwent regional cerebral blood flow studies while at rest or during normal saline infusion and during sodium lactate infusion. Six of the 10 patients and none of the control subjects experienced lactate-induced panic attacks. Lactate infusion markedly raised hemispheric blood flow levels in both control subjects and patients who did not panic. Patients who did panic experienced either a minimal increase or a decrease in hemisphericmore » blood flow.« less

  3. Laser Doppler anemometer signal processing for blood flow velocity measurements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Borozdova, M A; Fedosov, I V; Tuchin, V V

    A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (lasermore » applications and other topics in quantum electronics)« less

  4. Positron emission tomography detects greater blood flow and less blood flow heterogeneity in the exercising skeletal muscles of old compared with young men during fatiguing contractions

    PubMed Central

    Rudroff, Thorsten; Weissman, Jessica A; Bucci, Marco; Seppänen, Marko; Kaskinoro, Kimmo; Heinonen, Ilkka; Kalliokoski, Kari K

    2014-01-01

    The purpose of this study was to investigate blood flow and its heterogeneity within and among the knee muscles in five young (26 ± 6 years) and five old (77 ± 6 years) healthy men with similar levels of physical activity while they performed two types of submaximal fatiguing isometric contraction that required either force or position control. Positron emission tomography (PET) and [15O]-H2O were used to determine blood flow at 2 min (beginning) and 12 min (end) after the start of the tasks. Young and old men had similar maximal forces and endurance times for the fatiguing tasks. Although muscle volumes were lower in the older subjects, total muscle blood flow was similar in both groups (young men: 25.8 ± 12.6 ml min−1; old men: 25.1 ± 15.4 ml min−1; age main effect, P = 0.77) as blood flow per unit mass of muscle in the exercising knee extensors was greater in the older (12.5 ± 6.2 ml min−1 (100 g)−1) than the younger (8.6 ± 3.6 ml min−1 (100 g)−1) men (age main effect, P = 0.001). Further, blood flow heterogeneity in the exercising knee extensors was significantly lower in the older (56 ± 27%) than the younger (67 ± 34%) men. Together, these data show that although skeletal muscles are smaller in older subjects, based on the intact neural drive to the muscle and the greater, less heterogeneous blood flow per gram of muscle, old fit muscle achieves adequate exercise hyperaemia. Key points The results of previous studies that attempted to demonstrate the effects of ageing on skeletal muscle blood flow are controversial because these studies used indirect assessments of skeletal muscle blood flow obtained via whole limb blood flow measurements that provide no information on the distribution of blood flow within particular muscles. We used positron emission tomography to measure blood flow per gram of muscle in old and young men with similar levels of physical activity

  5. Regulation of human retinal blood flow by endothelin-1.

    PubMed

    Polak, Kaija; Luksch, Alexandra; Frank, Barbara; Jandrasits, Kerstin; Polska, Elzbieta; Schmetterer, Leopold

    2003-05-01

    There is evidence from in vitro and animal studies that endothelin is a major regulator of retinal blood flow. We set out to characterize the role of the endothelin-system in the blood flow control of the human retina. Two studies in healthy subjects were performed. The study design was randomized, placebo-controlled, double-masked, balanced, two-way crossover in protocol A and three way-way crossover in protocol B. In protocol A 18 healthy male subjects received intravenous endothelin-1 (ET-1) in a dose of 2.5 ng kg (-1)min(-1) for 30 min or placebo on two different study days and retinal vessel diameters were measured. In protocol B 12 healthy male subjects received ET-1 in stepwise increasing doses of 0, 1.25, 2.5 and 5 ng kg (-1)min(-1) (each infusion step over 20 min) in co-infusion with the specific ET(A)-receptor antagonist BQ123 (60 microg min (-1)) or placebo or BQ123 alone investigating retinal vessel diameters, retinal blood velocity and retinal blood flow. Measurements of retinal vessel size were done with the Zeiss retinal vessel analyzer. Measurements of blood velocities were done with bi-directional laser Doppler velocimetry. From these measurements retinal blood flow was calculated. In protocol A exogenous ET-1 tended to decrease retinal arterial diameter, but this effect was not significant versus placebo. No effect on retinal venous diameter was seen. In protocol B retinal venous blood velocity and retinal blood flow was significantly reduced after administration of exogenous ET-1. These effects were significantly blunted when BQ-123 was co-administered. By contrast, BQ-123 alone had no effect on retinal hemodynamic parameters. Concluding, BQ123 antagonizes the effects of exogenously administered ET-1 on retinal blood flow in healthy subjects. In addition, the results of the present study are compatible with the hypothesis that ET-1 exerts its vasoconstrictor effects in the retina mainly on the microvessels.

  6. In vivo imaging of mammalian cochlear blood flow using fluorescence microendoscopy.

    PubMed

    Monfared, Ashkan; Blevins, Nikolas H; Cheung, Eunice L M; Jung, Juergen C; Popelka, Gerald; Schnitzer, Mark J

    2006-02-01

    We sought to develop techniques for visualizing cochlear blood flow in live mammalian subjects using fluorescence microendoscopy. Inner ear microcirculation appears to be intimately involved in cochlear function. Blood velocity measurements suggest that intense sounds can alter cochlear blood flow. Disruption of cochlear blood flow may be a significant cause of hearing impairment, including sudden sensorineural hearing loss. However, inability to image cochlear blood flow in a nondestructive manner has limited investigation of the role of inner ear microcirculation in hearing function. Present techniques for imaging cochlear microcirculation using intravital light microscopy involve extensive perturbations to cochlear structure, precluding application in human patients. The few previous endoscopy studies of the cochlea have suffered from optical resolution insufficient for visualizing cochlear microvasculature. Fluorescence microendoscopy is an emerging minimally invasive imaging modality that provides micron-scale resolution in tissues inaccessible to light microscopy. In this article, we describe the use of fluorescence microendoscopy in live guinea pigs to image capillary blood flow and movements of individual red blood cells within the basal turn of the cochlea. We anesthetized eight adult guinea pigs and accessed the inner ear through the mastoid bulla. After intravenous injection of fluorescein dye, we made a limited cochleostomy and introduced a compound doublet gradient refractive index endoscope probe 1 mm in diameter into the inner ear. We then imaged cochlear blood flow within individual vessels in an epifluorescence configuration using one-photon fluorescence microendoscopy. We observed single red blood cells passing through individual capillaries in several cochlear structures, including the round window membrane, spiral ligament, osseous spiral lamina, and basilar membrane. Blood flow velocities within inner ear capillaries varied widely, with

  7. Establishing the diffuse correlation spectroscopy signal relationship with blood flow.

    PubMed

    Boas, David A; Sakadžić, Sava; Selb, Juliette; Farzam, Parisa; Franceschini, Maria Angela; Carp, Stefan A

    2016-07-01

    Diffuse correlation spectroscopy (DCS) measurements of blood flow rely on the sensitivity of the temporal autocorrelation function of diffusively scattered light to red blood cell (RBC) mean square displacement (MSD). For RBCs flowing with convective velocity [Formula: see text], the autocorrelation is expected to decay exponentially with [Formula: see text], where [Formula: see text] is the delay time. RBCs also experience shear-induced diffusion with a diffusion coefficient [Formula: see text] and an MSD of [Formula: see text]. Surprisingly, experimental data primarily reflect diffusive behavior. To provide quantitative estimates of the relative contributions of convective and diffusive movements, we performed Monte Carlo simulations of light scattering through tissue of varying vessel densities. We assumed laminar vessel flow profiles and accounted for shear-induced diffusion effects. In agreement with experimental data, we found that diffusive motion dominates the correlation decay for typical DCS measurement parameters. Furthermore, our model offers a quantitative relationship between the RBC diffusion coefficient and absolute tissue blood flow. We thus offer, for the first time, theoretical support for the empirically accepted ability of the DCS blood flow index ([Formula: see text]) to quantify tissue perfusion. We find [Formula: see text] to be linearly proportional to blood flow, but with a proportionality modulated by the hemoglobin concentration and the average blood vessel diameter.

  8. Flow of Red Blood Cells in Stenosed Microvessels.

    PubMed

    Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

    2016-06-20

    A computational study is presented on the flow of deformable red blood cells in stenosed microvessels. It is observed that the Fahraeus-Lindqvist effect is significantly enhanced due to the presence of a stenosis. The apparent viscosity of blood is observed to increase by several folds when compared to non-stenosed vessels. An asymmetric distribution of the red blood cells, caused by geometric focusing in stenosed vessels, is observed to play a major role in the enhancement. The asymmetry in cell distribution also results in an asymmetry in average velocity and wall shear stress along the length of the stenosis. The discrete motion of the cells causes large time-dependent fluctuations in flow properties. The root-mean-square of flow rate fluctuations could be an order of magnitude higher than that in non-stenosed vessels. Several folds increase in Eulerian velocity fluctuation is also observed in the vicinity of the stenosis. Surprisingly, a transient flow reversal is observed upstream a stenosis but not downstream. The asymmetry and fluctuations in flow quantities and the flow reversal would not occur in absence of the cells. It is concluded that the flow physics and its physiological consequences are significantly different in micro- versus macrovascular stenosis.

  9. Flow of Red Blood Cells in Stenosed Microvessels

    NASA Astrophysics Data System (ADS)

    Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

    2016-06-01

    A computational study is presented on the flow of deformable red blood cells in stenosed microvessels. It is observed that the Fahraeus-Lindqvist effect is significantly enhanced due to the presence of a stenosis. The apparent viscosity of blood is observed to increase by several folds when compared to non-stenosed vessels. An asymmetric distribution of the red blood cells, caused by geometric focusing in stenosed vessels, is observed to play a major role in the enhancement. The asymmetry in cell distribution also results in an asymmetry in average velocity and wall shear stress along the length of the stenosis. The discrete motion of the cells causes large time-dependent fluctuations in flow properties. The root-mean-square of flow rate fluctuations could be an order of magnitude higher than that in non-stenosed vessels. Several folds increase in Eulerian velocity fluctuation is also observed in the vicinity of the stenosis. Surprisingly, a transient flow reversal is observed upstream a stenosis but not downstream. The asymmetry and fluctuations in flow quantities and the flow reversal would not occur in absence of the cells. It is concluded that the flow physics and its physiological consequences are significantly different in micro- versus macrovascular stenosis.

  10. Modeling Blood Flow in the Aorta.

    ERIC Educational Resources Information Center

    McConnell, Colin J.; Carmichael, Jonathan B.; DeMont, M. Edwin

    1997-01-01

    Presents an exercise to demonstrate two fundamental concepts of fluid mechanics: the Reynolds number and the Principle of Continuity. The exercise demonstrates flow in a major blood vessel, such as the aorta, with and without a stenosis. Students observe the transition from laminar to turbulent flow as well as downstream persistence of turbulence.…

  11. Effect of renal denervation on dynamic autoregulation of renal blood flow.

    PubMed

    DiBona, Gerald F; Sawin, Linda L

    2004-06-01

    Vasoconstrictor intensities of renal sympathetic nerve stimulation elevate the renal arterial pressure threshold for steady-state stepwise autoregulation of renal blood flow. This study examined the tonic effect of basal renal sympathetic nerve activity on dynamic autoregulation of renal blood flow in rats with normal (Sprague-Dawley and Wistar-Kyoto) and increased levels of renal sympathetic nerve activity (congestive heart failure and spontaneously hypertensive rats). Steady-state values of arterial pressure and renal blood flow before and after acute renal denervation were subjected to transfer function analysis. Renal denervation increased basal renal blood flow in congestive heart failure (+35 +/- 3%) and spontaneously hypertensive rats (+21 +/- 3%) but not in Sprague-Dawley and Wistar-Kyoto rats. Renal denervation significantly decreased transfer function gain (i.e., improved autoregulation of renal blood flow) and increased coherence only in spontaneously hypertensive rats. Thus vasoconstrictor intensities of renal sympathetic nerve activity impaired the dynamic autoregulatory adjustments of the renal vasculature to oscillations in arterial pressure. Renal denervation increased renal blood flow variability in spontaneously hypertensive rats and congestive heart failure rats. The contribution of vasoconstrictor intensities of basal renal sympathetic nerve activity to limiting renal blood flow variability may be important in the stabilization of glomerular filtration rate.

  12. Study of blood flow sensing with microwave radiometry

    NASA Technical Reports Server (NTRS)

    Porter, R. A.; Wentz, F. J., III

    1973-01-01

    A study and experimental investigation has been performed to determine the feasibility of measuring regional blood flow and volume in man by means of microwave radiometry. An indication was expected of regional blood flow from measurement of surface and subsurface temperatures with a sensitive radiometer. Following theoretical modeling of biological tissue, to determine the optimum operating frequency for adequate sensing depth, a sensitive microwave radiometer was designed for operation at 793 MHz. A temperature sensitivity of of 0.06 K rms was realized in this equipment. Measurements performed on phantom tissue models, consisting of beef fat and lean beefsteak showed that the radiometer was capable of sensing temperatures from a depth between 3.8 and 5.1 cm. Radiometric and thermodynamic temperature measurements were also performed on the hind thighs of large dogs. These showed that the radiometer could sense subsurface temperatures from a depth of, at least, 1.3 cm. Delays caused by externally-generated RF interference, coupled with the lack of reliable blood flow measurement equipment, prevented correlation of radiometer readings with reginal blood flow. For the same reasons, it was not possible to extend the radiometric observations to human subjects.

  13. An implantable blood pressure and flow transmitter.

    NASA Technical Reports Server (NTRS)

    Rader, R. D.; Meehan, J. P.; Henriksen, J. K. C.

    1973-01-01

    A miniature totally implantable FM/FM telemetry system has been developed to simultaneously measure blood pressure and blood flow, thus providing an appreciation of the hemodynamics of the circulation to the entire body or to a particular organ. Developed for work with animal subjects, the telemetry system's transmission time is controlled by an RF signal that permits an operating life of several months. Pressure is detected by a miniature intravascular transducer and flow is detected by an extravascular interferometric ultrasonic technique. Both pressure and flow are calibrated prior to implanting. The pressure calibration can be checked after the implanting by cannulation; flow calibration can be verified only at the end of the experiment by determining the voltage output from the implanted sensing system as a function of several measured flow rates. The utility of this device has been established by its use in investigating canine renal circulation during exercise, emotional encounters, administration of drugs, and application of accelerative forces.

  14. Evaluating anesthetic protocols for functional blood flow imaging in the rat eye

    NASA Astrophysics Data System (ADS)

    Moult, Eric M.; Choi, WooJhon; Boas, David A.; Baumann, Bernhard; Clermont, Allen C.; Feener, Edward P.; Fujimoto, James G.

    2017-01-01

    The purpose of this study is to evaluate the suitability of five different anesthetic protocols (isoflurane, isoflurane-xylazine, pentobarbital, ketamine-xylazine, and ketamine-xylazine-vecuronium) for functional blood flow imaging in the rat eye. Total retinal blood flow was measured at a series of time points using an ultrahigh-speed Doppler OCT system. Additionally, each anesthetic protocol was qualitatively evaluated according to the following criteria: (1) time-stability of blood flow, (2) overall rate of blood flow, (3) ocular immobilization, and (4) simplicity. We observed that different anesthetic protocols produced markedly different blood flows. Different anesthetic protocols also varied with respect to the four evaluated criteria. These findings suggest that the choice of anesthetic protocol should be carefully considered when designing and interpreting functional blood flow studies in the rat eye.

  15. Concomitant administration of nitrous oxide and remifentanil reduces oral tissue blood flow without decreasing blood pressure during sevoflurane anesthesia in rabbits.

    PubMed

    Kasahara, Masataka; Ichinohe, Tatsuya; Okamoto, Sota; Okada, Reina; Kanbe, Hiroaki; Matsuura, Nobuyuki

    2015-06-01

    To determine whether continuous administration of nitrous oxide and remifentanil—either alone or together—alters blood flow in oral tissues during sevoflurane anesthesia. Eight male tracheotomized Japanese white rabbits were anesthetized with sevoflurane under mechanical ventilation. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), common carotid arterial blood flow (CCBF), tongue mucosal blood flow (TMBF), mandibular bone marrow blood flow (BBF), masseter muscle blood flow (MBF), upper alveolar tissue blood flow (UBF), and lower alveolar tissue blood flow (LBF) were recorded in the absence of all test agents and after administration of the test agents (50 % nitrous oxide, 0.4 μg/kg/min remifentanil, and their combination) for 20 min. Nitrous oxide increased SBP, DBP, MAP, CCBF, BBF, MBF, UBF, and LBF relative to baseline values but did not affect HR or TMBF. Remifentanil decreased all hemodynamic variables except DBP. Combined administration of nitrous oxide and remifentanil recovered SBP, DBP, MAP, and CCBF to baseline levels, but HR and oral tissue blood flow remained lower than control values. Our findings suggest that concomitant administration of nitrous oxide and remifentanil reduces blood flow in oral tissues without decreasing blood pressure during sevoflurane anesthesia in rabbits.

  16. Effects of respiratory muscle work on respiratory and locomotor blood flow during exercise.

    PubMed

    Dominelli, Paolo B; Archiza, Bruno; Ramsook, Andrew H; Mitchell, Reid A; Peters, Carli M; Molgat-Seon, Yannick; Henderson, William R; Koehle, Michael S; Boushel, Robert; Sheel, A William

    2017-11-01

    What is the central question of this study? Does manipulation of the work of breathing during high-intensity exercise alter respiratory and locomotor muscle blood flow? What is the main finding and its importance? We found that when the work of breathing was reduced during exercise, respiratory muscle blood flow decreased, while locomotor muscle blood flow increased. Conversely, when the work of breathing was increased, respiratory muscle blood flow increased, while locomotor muscle blood flow decreased. Our findings support the theory of a competitive relationship between locomotor and respiratory muscles during intense exercise. Manipulation of the work of breathing (WOB) during near-maximal exercise influences leg blood flow, but the effects on respiratory muscle blood flow are equivocal. We sought to assess leg and respiratory muscle blood flow simultaneously during intense exercise while manipulating WOB. Our hypotheses were as follows: (i) increasing the WOB would increase respiratory muscle blood flow and decrease leg blood flow; and (ii) decreasing the WOB would decrease respiratory muscle blood flow and increase leg blood flow. Eight healthy subjects (n = 5 men, n = 3 women) performed a maximal cycle test (day 1) and a series of constant-load exercise trials at 90% of peak work rate (day 2). On day 2, WOB was assessed with oesophageal balloon catheters and was increased (via resistors), decreased (via proportional assist ventilation) or unchanged (control) during the trials. Blood flow was assessed using near-infrared spectroscopy optodes placed over quadriceps and the sternocleidomastoid muscles, coupled with a venous Indocyanine Green dye injection. Changes in WOB were significantly and positively related to changes in respiratory muscle blood flow (r = 0.73), whereby increasing the WOB increased blood flow. Conversely, changes in WOB were significantly and inversely related to changes in locomotor blood flow (r = 0.57), whereby decreasing the

  17. Correlation between uteroplacental three-dimensional power Doppler indices and true uterine blood flow: evaluation in a pregnant sheep model.

    PubMed

    Morel, O; Pachy, F; Chavatte-Palmer, P; Bonneau, M; Gayat, E; Laigre, P; Evain-Brion, D; Tsatsaris, V

    2010-11-01

    Three-dimensional (3D) Doppler quantification within the uteroplacental unit could be of great help in understanding and screening for pre-eclampsia and intrauterine growth restriction. Yet the correlation between 3D Doppler indices and true blood flow has not been confirmed in vivo. The aim of this study was to evaluate this correlation in a pregnant sheep model. A blood flow quantitative sensor and a controllable vascular occlusion system were placed around the common uterine artery in seven sheep in late pregnancy, while all the other arterial supplies were ligated. Several occlusion levels were applied, from 0 to 100%, simultaneously with 3D Doppler acquisitions of several placentomes, using standardized settings. Each placentome was analyzed using VOCAL™ (Virtual Organ Computer-aided AnaLysis) software. The correlation between true blood flow and Doppler indices (vascularization index (VI), flow index (FI) and vascularization flow index (VFI)) was evaluated, together with measurement reproducibility. Forty-eight acquisitions were analyzed. All 3D Doppler indices were significantly correlated with true blood flow. Higher correlations were observed for VI and VFI (r = 0.81 (0.74-0.87), P < 0.0001 and r = 0.75 (0.67-0.82), P < 0.0001) compared with FI (r = 0.53 (0.38-0.64) P < 0.0001). Both intra- and interobserver reproducibility were high, with intraclass correlation coefficients of at least 0.799. This is the first in-vivo experimental study confirming a significant correlation between true blood perfusion and quantitative 3D Doppler indices measured within the uteroplacental unit. These results confirm the potential usefulness of 3D Doppler ultrasound for the assessment of placental vascular insufficiency both in clinical cases and in a research setting. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.

  18. Blood Flow: Multi-scale Modeling and Visualization (July 2011)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None

    2011-01-01

    Multi-scale modeling of arterial blood flow can shed light on the interaction between events happening at micro- and meso-scales (i.e., adhesion of red blood cells to the arterial wall, clot formation) and at macro-scales (i.e., change in flow patterns due to the clot). Coupled numerical simulations of such multi-scale flow require state-of-the-art computers and algorithms, along with techniques for multi-scale visualizations. This animation presents early results of two studies used in the development of a multi-scale visualization methodology. The fisrt illustrates a flow of healthy (red) and diseased (blue) blood cells with a Dissipative Particle Dynamics (DPD) method. Each bloodmore » cell is represented by a mesh, small spheres show a sub-set of particles representing the blood plasma, while instantaneous streamlines and slices represent the ensemble average velocity. In the second we investigate the process of thrombus (blood clot) formation, which may be responsible for the rupture of aneurysms, by concentrating on the platelet blood cells, observing as they aggregate on the wall of an aneruysm. Simulation was performed on Kraken at the National Institute for Computational Sciences. Visualization was produced using resources of the Argonne Leadership Computing Facility at Argonne National Laboratory.« less

  19. Doppler ultrasound to detect pulpal blood flow changes during local anaesthesia.

    PubMed

    Yoon, M J; Lee, S J; Kim, E; Park, S H

    2012-01-01

      To examine whether Doppler ultrasound can detect changes in pulpal blood flow after infiltration anaesthesia.   Changes in pulpal blood flow in maxillary central incisor teeth of 18 patients (mean age 26.7 years, 13 men, five women) after infiltration anaesthesia were examined. Before infiltration anaesthesia, the pulpal blood flow was measured using Doppler ultrasound. A local anaesthetic solution containing 2% lidocaine with 1:80,000 epinephrine was injected into the submucosa above the experimental tooth. The Doppler ultrasound test was carried out at 5, 10, 20, 30, 45 and 60 min after infiltration. The parameters were Vas (maximum linear velocity, cm s(-1) ), Vam (average linear velocity, cm s(-1) ) and Vakd (minimum linear velocity, cm s(-1) ), which are indicators of the level of blood flow. The mixed procedure at the 95% confidence interval was used to examine the changes in pulpal blood flow after the injection.   The linear velocity profiles (Vas, Vam, and Vakd) decreased sharply 5 min after anaesthesia and then reduced continuously for 30 min. The maximum degree of blood flow reduction in Vas, Vam and Vakd was 58%, 83% and 82%, respectively. After 30 min, the linear velocities increased gradually. The Vam returned to the pre-anaesthesia state at 60 minutes but the Vas and Vakd did not recover completely.   Doppler ultrasound can detect changes in pulpal blood flow after infiltration anaesthesia. In the future, Doppler ultrasound can be used as a tool for measuring pulpal blood flow. © 2011 International Endodontic Journal.

  20. Brain Perfusion and Arterial Blood Flow Velocity During Prolonged Body Tilting.

    PubMed

    Montero, David; Rauber, Sven

    2016-08-01

    It remains unknown whether brain perfusion is preserved and mirrored by middle cerebral blood flow velocity (MCA BFV) during prolonged changes in body posture. Herein, we examined the impact of sustained (180 min) 30° head-up (HUT) and head-down (HDT) tilt on brain perfusion, as determined by MCA BFV and blood flow in the extracranial arteries. In 10 healthy male subjects, arterial diameters, BFVs, and blood flows were determined in the left internal carotid (ICA) and vertebral (VA) arteries using duplex Doppler ultrasound in supine rest, and 5, 20, 60, 120, and 180 min following 30° HUT and HDT. MCA BFV was recorded throughout with transcranial Doppler ultrasound. ICA as well as VA diameters and blood flows were unaltered during HUT. Likewise, brain blood flow and MCA BFV were preserved with HUT. In the HDT protocol, ICA and VA diameters were gradually increased, although ICA, VA, and brain blood flows were preserved. MCA BFV was progressively reduced during HDT. In addition, MCA BFV was positively associated with ICA BFV (β = 0.9) and negatively associated with ICA diameter (β = -125.5). MCA BFV was positively associated with brain blood flow during HUT (β = 0.2) but not HDT. Brain perfusion is preserved whereas MCA BFV is progressively decreased and associated with extracranial arterial BFV during sustained 30° HDT. Therefore, MCA BFV may not be a surrogate of brain perfusion in conditions including prolonged HDT. Montero D, Rauber S. Brain perfusion and arterial blood flow velocity during prolonged body tilting. Aerosp Med Hum Perform. 2016; 87(8):682-687.

  1. Relationship among visual field, blood flow, and neural structure measurements in glaucoma.

    PubMed

    Hwang, John C; Konduru, Ranjith; Zhang, Xinbo; Tan, Ou; Francis, Brian A; Varma, Rohit; Sehi, Mitra; Greenfield, David S; Sadda, Srinivas R; Huang, David

    2012-05-17

    To determine the relationship among visual field, neural structural, and blood flow measurements in glaucoma. Case-control study. Forty-seven eyes of 42 patients with perimetric glaucoma were age-matched with 27 normal eyes of 27 patients. All patients underwent Doppler Fourier-domain optical coherence tomography to measure retinal blood flow and standard glaucoma evaluation with visual field testing and quantitative structural imaging. Linear regression analysis was performed to analyze the relationship among visual field, blood flow, and structure, after all variables were converted to logarithmic decibel scale. Retinal blood flow was reduced in glaucoma eyes compared to normal eyes (P < 0.001). Visual field loss was correlated with both reduced retinal blood flow and structural loss of rim area and retinal nerve fiber layer (RNFL). There was no correlation or paradoxical correlation between blood flow and structure. Multivariate regression analysis revealed that reduced blood flow and structural loss are independent predictors of visual field loss. Each dB decrease in blood flow was associated with at least 1.62 dB loss in mean deviation (P ≤ 0.001), whereas each dB decrease in rim area and RNFL was associated with 1.15 dB and 2.56 dB loss in mean deviation, respectively (P ≤ 0.03). There is a close link between reduced retinal blood flow and visual field loss in glaucoma that is largely independent of structural loss. Further studies are needed to elucidate the causes of the vascular dysfunction and potential avenues for therapeutic intervention. Blood flow measurement may be useful as an independent assessment of glaucoma severity.

  2. Measurement of bronchial blood flow in the sheep by video dilution technique.

    PubMed Central

    Link, D P; Parsons, G H; Lantz, B M; Gunther, R A; Green, J F; Cross, C E

    1985-01-01

    Bronchial blood flow was determined in five adult anaesthetised sheep by the video dilution technique. This is a new fluoroscopic technique for measuring blood flow that requires only arterial catheterisation. Catheters were placed into the broncho-oesophageal artery and ascending aorta from the femoral arteries for contrast injections and subsequent videotape recording. The technique yields bronchial blood flow as a percentage of cardiac output. The average bronchial artery blood flow was 0.6% (SD 0.20%) of cardiac output. In one sheep histamine (90 micrograms) injected directly into the bronchial artery increased bronchial blood flow by a factor of 6 and histamine (90 micrograms) plus methacholine (4.5 micrograms) augmented flow by a factor of 7.5 while leaving cardiac output unchanged. This study confirms the high degree of reactivity of the bronchial circulation and demonstrates the feasibility of using the video dilution technique to investigate the determinants of total bronchial artery blood flow in a stable animal model avoiding thoracotomy. Images PMID:3883564

  3. Dynamic change of collateral flow varying with distribution of regional blood flow in acute ischemic rat cortex

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Luo, Weihua; Zhou, Fangyuan; Li, Pengcheng; Luo, Qingming

    2012-12-01

    Cerebral blood flow (CBF) is critical for the maintenance of cerebral function by guaranteed constant oxygen and glucose supply to brain. Collateral channels (CCs) are recruited to provide alternatives to CBF to ischemic regions once the primary vessel is occluded during ischemic stroke. However, the knowledge of the relationship between dynamic evolution of collateral flow and the distribution of regional blood flow remains limited. In this study, laser speckle imaging was used to assess dynamic changes of CCs and regional blood flow in a rat cortex with permanent middle cerebral artery occlusion (MCAo). We found that CCs immediately provided blood flow to ischemic territories after MCAo. More importantly, there were three kinds of dynamic changes of CCs during acute stroke: persistent CC, impermanent CC, and transient CC, respectively, related to different distributions of regional blood flow. Although there was the possible occurrence of peri-infarct depolarization (PID) during ischemia, there was no obvious significance about the onset time and duration of CCs between rats with and without PID. These results suggest that the initial arising of CCs does not ensure their persistence, and that collateral flow could be varied with distribution of regional blood flow in acute ischemic stroke, which may facilitate the understanding of collateral recruitment and promote the development of collateral therapeutics in the future.

  4. Dynamic change of collateral flow varying with distribution of regional blood flow in acute ischemic rat cortex.

    PubMed

    Wang, Zhen; Luo, Weihua; Zhou, Fangyuan; Li, Pengcheng; Luo, Qingming

    2012-12-01

    Cerebral blood flow (CBF) is critical for the maintenance of cerebral function by guaranteed constant oxygen and glucose supply to brain. Collateral channels (CCs) are recruited to provide alternatives to CBF to ischemic regions once the primary vessel is occluded during ischemic stroke. However, the knowledge of the relationship between dynamic evolution of collateral flow and the distribution of regional blood flow remains limited. In this study, laser speckle imaging was used to assess dynamic changes of CCs and regional blood flow in a rat cortex with permanent middle cerebral artery occlusion (MCAo). We found that CCs immediately provided blood flow to ischemic territories after MCAo. More importantly, there were three kinds of dynamic changes of CCs during acute stroke: persistent CC, impermanent CC, and transient CC, respectively, related to different distributions of regional blood flow. Although there was the possible occurrence of peri-infarct depolarization (PID) during ischemia, there was no obvious significance about the onset time and duration of CCs between rats with and without PID. These results suggest that the initial arising of CCs does not ensure their persistence, and that collateral flow could be varied with distribution of regional blood flow in acute ischemic stroke, which may facilitate the understanding of collateral recruitment and promote the development of collateral therapeutics in the future.

  5. In vivo lateral blood flow velocity measurement using speckle size estimation.

    PubMed

    Xu, Tiantian; Hozan, Mohsen; Bashford, Gregory R

    2014-05-01

    In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is "smeared") if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method

  6. Modelling the effect of laminar axially directed blood flow on the dissolution of non-occlusive blood clots.

    PubMed

    Sersa, I; Vidmar, J; Grobelnik, B; Mikac, U; Tratar, G; Blinc, A

    2007-06-07

    Axially directed blood plasma flow can significantly accelerate thrombolysis of non-occlusive blood clots. Viscous forces caused by shearing of blood play an essential role in this process, in addition to biochemical fibrinolytic reactions. An analytical mathematical model based on the hypothesis that clot dissolution dynamics is proportional to the power of the flowing blood plasma dissipated along the clot is presented. The model assumes cylindrical non-occlusive blood clots with the flow channel in the centre, in which the flow is assumed to be laminar and flow rate constant at all times during dissolution. Effects of sudden constriction on the flow and its impact on the dissolution rate are also considered. The model was verified experimentally by dynamic magnetic resonance (MR) microscopy of artificial blood clots dissolving in an in vitro circulation system, containing plasma with a magnetic resonance imaging contrast agent and recombinant tissue-type plasminogen activator (rt-PA). Sequences of dynamically acquired 3D low resolution MR images of entire clots and 2D high resolution MR images of clots in the axial cross-section were used to evaluate the dissolution model by fitting it to the experimental data. The experimental data fitted well to the model and confirmed our hypothesis.

  7. Self-sustaining turbulence in a restricted nonlinear model of plane Couette flow

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thomas, Vaughan L.; Gayme, Dennice F.; Lieu, Binh K.

    2014-10-15

    This paper demonstrates the maintenance of self-sustaining turbulence in a restricted nonlinear (RNL) model of plane Couette flow. The RNL system is derived directly from the Navier-Stokes equations and permits higher resolution studies of the dynamical system associated with the stochastic structural stability theory (S3T) model, which is a second order approximation of the statistical state dynamics of the flow. The RNL model shares the dynamical restrictions of the S3T model but can be easily implemented by reducing a DNS code so that it retains only the RNL dynamics. Comparisons of turbulence arising from DNS and RNL simulations demonstrate thatmore » the RNL system supports self-sustaining turbulence with a mean flow as well as structural and dynamical features that are consistent with DNS. These results demonstrate that the simplified RNL system captures fundamental aspects of fully developed turbulence in wall-bounded shear flows and motivate use of the RNL/S3T framework for further study of wall-turbulence.« less

  8. Cerebral blood flow in patients with congestive heart failure treated with captopril.

    PubMed

    Paulson, O B; Jarden, J O; Godtfredsen, J; Vorstrup, S

    1984-05-31

    The effect of captopril on cerebral blood flow was studied in five patients with severe congestive heart failure and in five control subjects. Cerebral blood flow was measured by inhalation of 133xenon and registration of its uptake and washout from the brain by single photon emission computer tomography. In addition, cerebral (internal jugular) venous oxygen tension was determined in the controls. The measurements were made before and 15, 60, and 180 minutes after a single oral dose of captopril (6.25 mg in patients with congestive heart failure and 25 mg in controls). Despite a marked decrease in blood pressure, cerebral blood flow increased slightly in the patients with severe congestive heart failure. When a correction was applied to take account of a change in arterial carbon dioxide tension, however, cerebral blood flow was unchanged after captopril administration even in patients with the greatest decrease in blood pressure, in whom a decrease in cerebral blood flow might have been expected. In the controls, blood pressure was little affected by captopril, whereas a slight, but not statistically significant, decrease in cerebral blood flow was observed. The cerebral venous oxygen tension decreased concomitantly.

  9. Mesoscale Simulation of Blood Flow in Small Vessels

    PubMed Central

    Bagchi, Prosenjit

    2007-01-01

    Computational modeling of blood flow in microvessels with internal diameter 20–500 μm is a major challenge. It is because blood in such vessels behaves as a multiphase suspension of deformable particles. A continuum model of blood is not adequate if the motion of individual red blood cells in the suspension is of interest. At the same time, multiple cells, often a few thousands in number, must also be considered to account for cell-cell hydrodynamic interaction. Moreover, the red blood cells (RBCs) are highly deformable. Deformation of the cells must also be considered in the model, as it is a major determinant of many physiologically significant phenomena, such as formation of a cell-free layer, and the Fahraeus-Lindqvist effect. In this article, we present two-dimensional computational simulation of blood flow in vessels of size 20–300 μm at discharge hematocrit of 10–60%, taking into consideration the particulate nature of blood and cell deformation. The numerical model is based on the immersed boundary method, and the red blood cells are modeled as liquid capsules. A large RBC population comprising of as many as 2500 cells are simulated. Migration of the cells normal to the wall of the vessel and the formation of the cell-free layer are studied. Results on the trajectory and velocity traces of the RBCs, and their fluctuations are presented. Also presented are the results on the plug-flow velocity profile of blood, the apparent viscosity, and the Fahraeus-Lindqvist effect. The numerical results also allow us to investigate the variation of apparent blood viscosity along the cross-section of a vessel. The computational results are compared with the experimental results. To the best of our knowledge, this article presents the first simulation to simultaneously consider a large ensemble of red blood cells and the cell deformation. PMID:17208982

  10. Validation of thermal techniques for measurement of pelvic organ blood flows in the nonpregnant sheep: comparison with transit-time ultrasonic and microsphere measurements of blood flow

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Randall, N.J.; Beard, R.W.; Sutherland, I.A.

    1988-03-01

    Data obtained from a thermal system capable of measuring changes in organ temperature as well as tissue thermal clearance in the uterus and vagina have been compared with blood flow measured continuously with a transit-time ultrasound volume-flow sensor placed around the common internal iliac artery and intermittently with radioactive microspheres in the chronically instrumented nonpregnant sheep. Temperature changes in both the uterus and the vagina correlated well with blood flow changes measured by both techniques after intravenous administration of estradiol or norepinephrine. Thermal clearance did not correlate well with blood flow in the vagina or uterus. These methods may havemore » value in the investigation of blood flow patterns in various clinical situations such as the pelvic pain syndrome and early pregnancy.« less

  11. Ultrasound predictors of neonatal outcome in intrauterine growth restriction.

    PubMed

    Craigo, S D; Beach, M L; Harvey-Wilkes, K B; D'Alton, M E

    1996-11-01

    Our purpose was to assess the value of commonly performed ultrasound parameters in predicting neonatal outcome of fetuses with intrauterine growth restriction (IUGR). One hundred twenty-seven patients were identified on ultrasound examination to have IUGR. Estimated weight percentile, amniotic fluid volume, umbilical artery Doppler velocimetry, and head circumference/abdominal circumference ratio were compared with neonatal outcome. Thirty infants had severely adverse courses. The degree of growth restriction was strongly associated with adverse outcome and neonatal death. Umbilical artery Doppler waveforms with absent or reverse end-diastolic flow were predicted of neonatal death, bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), and adverse outcome in general. Oligohydramnios was predictive of adverse outcome and neonatal death. Logistic regression also showed that absent or reverse end-diastolic flow and oligohydramnios were independent predictors of adverse outcome. Ultrasound findings of low estimated weight percentile, absent or reverse end-diastolic umbilical blood flow, and oligohydramnios are independent predictors of adverse neonatal outcome of growth restricted fetuses.

  12. Numerical Modeling of Interstitial Fluid Flow Coupled with Blood Flow through a Remodeled Solid Tumor Microvascular Network

    PubMed Central

    Soltani, M.; Chen, P.

    2013-01-01

    Modeling of interstitial fluid flow involves processes such as fluid diffusion, convective transport in extracellular matrix, and extravasation from blood vessels. To date, majority of microvascular flow modeling has been done at different levels and scales mostly on simple tumor shapes with their capillaries. However, with our proposed numerical model, more complex and realistic tumor shapes and capillary networks can be studied. Both blood flow through a capillary network, which is induced by a solid tumor, and fluid flow in tumor’s surrounding tissue are formulated. First, governing equations of angiogenesis are implemented to specify the different domains for the network and interstitium. Then, governing equations for flow modeling are introduced for different domains. The conservation laws for mass and momentum (including continuity equation, Darcy’s law for tissue, and simplified Navier–Stokes equation for blood flow through capillaries) are used for simulating interstitial and intravascular flows and Starling’s law is used for closing this system of equations and coupling the intravascular and extravascular flows. This is the first study of flow modeling in solid tumors to naturalistically couple intravascular and extravascular flow through a network. This network is generated by sprouting angiogenesis and consisting of one parent vessel connected to the network while taking into account the non-continuous behavior of blood, adaptability of capillary diameter to hemodynamics and metabolic stimuli, non-Newtonian blood flow, and phase separation of blood flow in capillary bifurcation. The incorporation of the outlined components beyond the previous models provides a more realistic prediction of interstitial fluid flow pattern in solid tumors and surrounding tissues. Results predict higher interstitial pressure, almost two times, for realistic model compared to the simplified model. PMID:23840579

  13. Red blood cell microparticles and blood group antigens: an analysis by flow cytometry

    PubMed Central

    Canellini, Giorgia; Rubin, Olivier; Delobel, Julien; Crettaz, David; Lion, Niels; Tissot, Jean-Daniel

    2012-01-01

    Background The storage of blood induces the formation of erythrocytes-derived microparticles. Their pathogenic role in blood transfusion is not known so far, especially the risk to trigger alloantibody production in the recipient. This work aims to study the expression of clinically significant blood group antigens on the surface of red blood cells microparticles. Material and methods Red blood cells contained in erythrocyte concentrates were stained with specific antibodies directed against blood group antigens and routinely used in immunohematology practice. After inducing erythrocytes vesiculation with calcium ionophore, the presence of blood group antigens was analysed by flow cytometry. Results The expression of several blood group antigens from the RH, KEL, JK, FY, MNS, LE and LU systems was detected on erythrocyte microparticles. The presence of M (MNS1), N (MNS2) and s (MNS4) antigens could not be demonstrated by flow cytometry, despite that glycophorin A and B were identified on microparticles using anti-CD235a and anti-MNS3. Discussion We conclude that blood group antigens are localized on erythrocytes-derived microparticles and probably keep their immunogenicity because of their capacity to bind specific antibody. Selective segregation process during vesiculation or their ability to elicit an immune response in vivo has to be tested by further studies. PMID:22890266

  14. Insight of Human Stroke from blood flow and blood pressure

    NASA Astrophysics Data System (ADS)

    Chen, Zhi; Ivanov, Plamen Ch.; Hu, Kun; Stanley, H. Eugene

    2003-03-01

    Stroke is is one of the leading cause of death and disability in the world. It is well believed that stroke is caused by the disturbance of cerebrovascular autoregulation. We investigate the blood flow on the left and right middle cerebral artery and beat-to-beat blood pressure simultaneously measured from the finger, for both subjects with stroke and healthy subjects. Synchronization technique is used to distinguish the difference between these two groups.

  15. Longitudinal optical monitoring of blood flow in breast tumors during neoadjuvant chemotherapy

    NASA Astrophysics Data System (ADS)

    Cochran, J. M.; Chung, S. H.; Leproux, A.; Baker, W. B.; Busch, D. R.; DeMichele, A. M.; Tchou, J.; Tromberg, B. J.; Yodh, A. G.

    2017-06-01

    We measure tissue blood flow markers in breast tumors during neoadjuvant chemotherapy and investigate their correlation to pathologic complete response in a pilot longitudinal patient study (n  =  4). Tumor blood flow is quantified optically by diffuse correlation spectroscopy (DCS), and tissue optical properties, blood oxygen saturation, and total hemoglobin concentration are derived from concurrent diffuse optical spectroscopic imaging (DOSI). The study represents the first longitudinal DCS measurement of neoadjuvant chemotherapy in humans over the entire course of treatment; it therefore offers a first correlation between DCS flow indices and pathologic complete response. The use of absolute optical properties measured by DOSI facilitates significant improvement of DCS blood flow calculation, which typically assumes optical properties based on literature values. Additionally, the combination of the DCS blood flow index and the tissue oxygen saturation from DOSI permits investigation of tissue oxygen metabolism. Pilot results from four patients suggest that lower blood flow in the lesion-bearing breast is correlated with pathologic complete response. Both absolute lesion blood flow and lesion flow relative to the contralateral breast exhibit potential for characterization of pathological response. This initial demonstration of the combined optical approach for chemotherapy monitoring provides incentive for more comprehensive studies in the future and can help power those investigations.

  16. Blood Flow in the Stenotic Carotid Bifurcation

    NASA Astrophysics Data System (ADS)

    Rayz, Vitaliy

    2005-11-01

    The carotid artery is prone to atherosclerotic disease and the growth of plaque in the vessel, leading often to severe occlusion or plaque rupture, resulting in emboli and thrombus, and, possibly, stroke. Modeling the flow in stenotic blood vessels can elucidate the influence of the flow on plaque growth and stability. Numerical simulations are carried out to model the complex flows in anatomically realistic, patient-specific geometries constructed from magnetic resonance images. The 3-D unsteady Navier-Stokes equations are solved in a finite-volume formulation, using an iterative pressure-correction algorithm. The flow field computed is highly three-dimensional, with high-speed jets and strong recirculating secondary flows. Sharp spatial and temporal variations of the velocities and shear stresses are observed. The results are in a good agreement with the available experimental and clinical data. The influence of non-Newtonian blood behavior and arterial wall compliance are considered. Transitional and turbulent regimes have been looked at using LES. This work supports the conjecture that numerical simulations can provide a diagnostic tool for assessing plaque stability.

  17. Influence of Gravity on Blood Volume and Flow Distribution

    NASA Technical Reports Server (NTRS)

    Pendergast, D.; Olszowka, A.; Bednarczyk, E.; Shykoff, B.; Farhi, L.

    1999-01-01

    In our previous experiments during NASA Shuttle flights SLS 1 and 2 (9-15 days) and EUROMIR flights (30-90 days) we observed that pulmonary blood flow (cardiac output) was elevated initially, and surprisingly remained elevated for the duration of the flights. Stroke volume increased initially and then decreased, but was still above 1 Gz values. As venous return was constant, the changes in SV were secondary to modulation of heart rate. Mean blood pressure was at or slightly below 1 Gz levels in space, indicating a decrease in total peripheral resistance. It has been suggested that plasma volume is reduced in space, however cardiac output/venous return do not return to 1 Gz levels over the duration of flight. In spite of the increased cardiac output, central venous pressure was not elevated in space. These data suggest that there is a change in the basic relationship between cardiac output and central venous pressure, a persistent "hyperperfusion" and a re-distribution of blood flow and volume during space flight. Increased pulmonary blood flow has been reported to increase diffusing capacity in space, presumably due to the improved homogeneity of ventilation and perfusion. Other studies have suggested that ventilation may be independent of gravity, and perfusion may not be gravity- dependent. No data for the distribution of pulmonary blood volume were available for flight or simulated microgravity. Recent studies have suggested that the pulmonary vascular tree is influenced by sympathetic tone in a manner similar to that of the systemic system. This implies that the pulmonary circulation is dilated during microgravity and that the distribution of blood flow and volume may be influenced more by vascular control than by gravity. The cerebral circulation is influenced by sympathetic tone similarly to that of the systemic and pulmonary circulations; however its effects are modulated by cerebral autoregulation. Thus it is difficult to predict if cerebral perfusion is

  18. Early phase adaptations in muscle strength and hypertrophy as a result of low-intensity blood flow restriction resistance training.

    PubMed

    Hill, Ethan C; Housh, Terry J; Keller, Joshua L; Smith, Cory M; Schmidt, Richard J; Johnson, Glen O

    2018-06-22

    Low-intensity venous blood flow restriction (vBFR) resistance training has been shown to promote increases in muscle strength and size. Eccentric-only muscle actions are typically a more potent stimulus to increase muscle strength and size than concentric-only muscle actions performed at the same relative intensities. Therefore, the purpose of this investigation was to examine the time-course of changes in muscle strength, hypertrophy, and neuromuscular adaptations following 4 weeks of unilateral forearm flexion low-intensity eccentric vBFR (Ecc-vBFR) vs. low-intensity concentric vBFR (Con-vBFR) resistance training performed at the same relative intensity. Thirty-six women were randomly assigned to either Ecc-vBFR (n = 12), Con-vBFR (n = 12) or control (no intervention, n = 12) group. Ecc-vBFR trained at 30% of eccentric peak torque and Con-vBFR trained at 30% of concentric peak torque. All training and testing procedures were performed at an isokinetic velocity of 120° s - ¹. Muscle strength increased similarly from 0 to 2 and 4 weeks of training as a result of Ecc-vBFR (13.9 and 35.0%) and Con-vBFR (13.4 and 31.2%), but there were no changes in muscle strength for the control group. Muscle thickness increased similarly from 0 to 2 and 4 weeks of training as a result of Ecc-vBFR (11.4 and 12.8%) and Con-vBFR (9.1 and 9.9%), but there were no changes for the control group. In addition, there were no changes in any of the neuromuscular responses. The Ecc-vBFR and Con-vBFR low-intensity training induced comparable increases in muscle strength and size. The increases in muscle strength, however, were not associated with neuromuscular adaptations.

  19. Emesis, radiation exposure, and local cerebral blood flow in the ferret

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tuor, U.I.; Kondysar, M.H.; Harding, R.K.

    1988-06-01

    We examined the sensitivity of the ferret to emetic stimuli and the effect of radiation exposure near the time of emesis on local cerebral blood flow. Ferrets vomited following the administration of either apomorphine (approx 45% of the ferrets tested) or peptide YY (approx 36% of those tested). Exposure to radiation was a very potent emetic stimulus, but vomiting could be prevented by restraint of the hindquarters of the ferret. Local cerebral blood flow was measured using a quantitative autoradiographic technique and with the exception of several regions in the telencephalon and cerebellum, local cerebral blood flow in the ferretmore » was similar to that in the rat. In animals with whole-body exposure to moderate levels of radiation (4 Gy of /sup 137/Cs), mean arterial blood pressure was similar to that in the control group. However, 15-25 min following irradiation there was a general reduction of local cerebral blood flow ranging from 7 to 33% of that in control animals. These cerebral blood flow changes likely correspond to a reduced activation of the central nervous system.« less

  20. Oscillations and Multiple Equilibria in Microvascular Blood Flow.

    PubMed

    Karst, Nathaniel J; Storey, Brian D; Geddes, John B

    2015-07-01

    We investigate the existence of oscillatory dynamics and multiple steady-state flow rates in a network with a simple topology and in vivo microvascular blood flow constitutive laws. Unlike many previous analytic studies, we employ the most biologically relevant models of the physical properties of whole blood. Through a combination of analytic and numeric techniques, we predict in a series of two-parameter bifurcation diagrams a range of dynamical behaviors, including multiple equilibria flow configurations, simple oscillations in volumetric flow rate, and multiple coexistent limit cycles at physically realizable parameters. We show that complexity in network topology is not necessary for complex behaviors to arise and that nonlinear rheology, in particular the plasma skimming effect, is sufficient to support oscillatory dynamics similar to those observed in vivo.

  1. Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects.

    PubMed

    Polska, E; Polak, K; Luksch, A; Fuchsjager-Mayrl, G; Petternel, V; Findl, O; Schmetterer, L

    2004-04-01

    To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours. The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%. These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency.

  2. Blood flow regulation and oxygen uptake during high-intensity forearm exercise.

    PubMed

    Nyberg, S K; Berg, O K; Helgerud, J; Wang, E

    2017-04-01

    The vascular strain is very high during heavy handgrip exercise, but the intensity and kinetics to reach peak blood flow, and peak oxygen uptake, are uncertain. We included 9 young (25 ± 2 yr) healthy males to evaluate blood flow and oxygen uptake responses during continuous dynamic handgrip exercise with increasing intensity. Blood flow was measured using Doppler-ultrasound, and venous blood was drawn from a deep forearm vein to determine arteriovenous oxygen difference (a-vO 2diff ) during 6-min bouts of 60, 80, and 100% of maximal work rate (WR max ), respectively. Blood flow and oxygen uptake increased ( P < 0.05) from 60%WR max [557 ± 177(SD) ml/min; 56.0 ± 21.6 ml/min] to 80%WR max (679 ± 190 ml/min; 70.6 ± 24.8 ml/min), but no change was seen from 80%WR max to 100%WR max Blood velocity (49.5 ± 11.5 to 58.1 ± 11.6 cm/s) and brachial diameter (0.49 ± 0.05 to 0.50 ± 0.06 cm) showed concomitant increases ( P < 0.05) with blood flow from 60% to 80%WR max, whereas no differences were observed in a-vO 2diff Shear rate also increased ( P < 0.05) from 60% (822 ± 196 s -1 ) to 80% (951 ± 234 s -1 ) of WR max The mean response time (MRT) was slower ( P < 0.05) for blood flow (60%WR max 50 ± 22 s; 80%WR max 51 ± 20 s; 100%WR max 51 ± 23 s) than a-vO 2diff (60%WR max 29 ± 9 s; 80%WR max 29 ± 5 s; 100%WR max 20 ± 5 s), but not different from oxygen uptake (60%WR max 44 ± 25 s; 80%WR max 43 ± 14 s; 100%WR max 41 ± 32 s). No differences were observed in MRT for blood flow or oxygen uptake with increased exercise intensity. In conclusion, when approaching maximal intensity, oxygen uptake appeared to reach a critical level at ~80% of WR max and be regulated by blood flow. This implies that high, but not maximal, exercise intensity may be an optimal stimulus for shear stress-induced small muscle mass training adaptations. NEW & NOTEWORTHY This study evaluated blood flow regulation and oxygen uptake during small muscle mass forearm exercise with high to

  3. Blood flow and oxygen uptake during exercise

    NASA Technical Reports Server (NTRS)

    Mitchell, J. W.; Stolwijk, J. A. J.; Nadel, E. R.

    1973-01-01

    A model is developed for predicting oxygen uptake, muscle blood flow, and blood chemistry changes under exercise conditions. In this model, the working muscle mass system is analyzed. The conservation of matter principle is applied to the oxygen in a unit mass of working muscle under transient exercise conditions. This principle is used to relate the inflow of oxygen carried with the blood to the outflow carried with blood, the rate of change of oxygen stored in the muscle myoglobin, and the uptake by the muscle. Standard blood chemistry relations are incorporated to evaluate venous levels of oxygen, pH, and carbon dioxide.

  4. Nucleated red blood cells in growth-restricted fetuses: associations with short-term neonatal outcome.

    PubMed

    Minior, V K; Bernstein, P S; Divon, M Y

    2000-01-01

    To determine the utility of the neonatal nucleated red blood cell (NRBC) count as an independent predictor of short-term perinatal outcome in growth-restricted fetuses. Hospital charts of neonates with a discharge diagnosis indicating a birth weight <10th percentile were reviewed for perinatal outcome. We studied all eligible neonates who had a complete blood count on the first day of life. After multiple gestations, anomalous fetuses and diabetic pregnancies were excluded; 73 neonates comprised the study group. Statistical analysis included ANOVA, simple and stepwise regression. Elevated NRBC counts were significantly associated with cesarean section for non-reassuring fetal status, neonatal intensive care unit admission and duration of neonatal intensive care unit stay, respiratory distress and intubation, thrombocytopenia, hyperbilirubinemia, intraventricular hemorrhage and neonatal death. Stepwise regression analysis including gestational age at birth, birth weight and NRBC count demonstrated that in growth-restricted fetuses, NRBC count was the strongest predictor of neonatal intraventricular hemorrhage, neonatal respiratory distress and neonatal death. An elevated NRBC count independently predicts adverse perinatal outcome in growth-restricted fetuses. Copyright 2000 S. Karger AG, Basel.

  5. Rosetting of Plasmodium falciparum-infected red blood cells with uninfected red blood cells enhances microvascular obstruction under flow conditions.

    PubMed

    Kaul, D K; Roth, E F; Nagel, R L; Howard, R J; Handunnetti, S M

    1991-08-01

    The occurrence of rosetting of Plasmodium falciparum-infected human red blood cells (IRBC) with uninfected red blood cells (RBC) and its potential pathophysiologic consequences were investigated under flow conditions using the perfused rat mesocecum vasculature. Perfusion experiments were performed using two knobby (K+) lines of P falciparum, ie, rosetting positive (K+R+) and rosetting negative (K+R-). The infusion of K+R+ IRBC resulted in higher peripheral resistance (PRU) than K+R- IRBC (P less than .0012). Video microscopy showed that under conditions of flow, in addition to cytoadherence of K+R+ IRBC to the venular endothelium, rosette formation was also restricted to venules, especially in the areas of slow flow. Rosettes were absent in arterioles and were presumably dissociated by higher wall shear rates. The presence of rosettes in the venules must therefore reflect their rapid reformation after disruption. Cytoadherence of K+R+ IRBC was characterized by formation of focal clusters along the venular wall. In addition, large aggregates of RBC were frequently observed at venular junctions, probably as a result of interaction between flowing rosettes, free IRBC, and uninfected RBC. In contrast, the infusion of K+R+ IRBC resulted in diffuse cytoadherence of these cells exclusively to the venular endothelium but not in rosetting or large aggregate formation. The cytoadherence of K+R+ IRBC showed strong inverse correlation with the venular diameter (r = -.856, P less than .00001). Incubation of K+R+ IRBC with heparin and with monoclonal antibodies to glycoprotein IV/CD36 abolished the rosette formation and resulted in decreased PRU and microvascular blockage. These findings demonstrate that rosetting of K+R+ IRBC with uninfected RBC enhances vasocclusion, suggesting an important in vivo role for rosetting in the microvascular sequestration of P falciparum-infected RBC.

  6. Simulating Nailfold Capillaroscopy Sequences to Evaluate Algorithms for Blood Flow Estimation

    PubMed Central

    Tresadern, P. A.; Berks, M.; Murray, A. K.; Dinsdale, G.; Taylor, C. J.; Herrick, A. L.

    2016-01-01

    The effects of systemic sclerosis (SSc) – a disease of the connective tissue causing blood flow problems that can require amputation of the fingers – can be observed indirectly by imaging the capillaries at the nailfold, though taking quantitative measures such as blood flow to diagnose the disease and monitor its progression is not easy. Optical flow algorithms may be applied, though without ground truth (i.e. known blood flow) it is hard to evaluate their accuracy. We propose an image model that generates realistic capillaroscopy videos with known flow, and use this model to quantify the effect of flow rate, cell density and contrast (among others) on estimated flow. This resource will help researchers to design systems that are robust under real-world conditions. PMID:24110268

  7. Simulating nailfold capillaroscopy sequences to evaluate algorithms for blood flow estimation.

    PubMed

    Tresadern, P A; Berks, M; Murray, A K; Dinsdale, G; Taylor, C J; Herrick, A L

    2013-01-01

    The effects of systemic sclerosis (SSc)--a disease of the connective tissue causing blood flow problems that can require amputation of the fingers--can be observed indirectly by imaging the capillaries at the nailfold, though taking quantitative measures such as blood flow to diagnose the disease and monitor its progression is not easy. Optical flow algorithms may be applied, though without ground truth (i.e. known blood flow) it is hard to evaluate their accuracy. We propose an image model that generates realistic capillaroscopy videos with known flow, and use this model to quantify the effect of flow rate, cell density and contrast (among others) on estimated flow. This resource will help researchers to design systems that are robust under real-world conditions.

  8. Ultrasonic Doppler blood flow meter for extracorporeal circulation

    NASA Astrophysics Data System (ADS)

    Dantas, Ricardo G.; Costa, Eduardo T.; Maia, Joaquim M.; Nantes Button, Vera L. d. S.

    2000-04-01

    In cardiac surgeries it is frequently necessary to carry out interventions in internal heart structures, and where the blood circulation and oxygenation are made by artificial ways, out of the patient's body, in a procedure known as extracorporeal circulation (EC). During this procedure, one of the most important parameters, and that demands constant monitoring, is the blood flow. In this work, an ultrasonic pulsed Doppler blood flowmeter, to be used in an extracorporeal circulation system, was developed. It was used a 2 MHz ultrasonic transducer, measuring flows from 0 to 5 liters/min, coupled externally to the EC arterial line destined to adults perfusion (diameter of 9.53 mm). The experimental results using the developed flowmeter indicated a maximum deviation of 3.5% of full scale, while the blood flow estimator based in the rotation speed of the peristaltic pump presented deviations greater than 20% of full scale. This ultrasonic flowmeter supplies the results in a continuous and trustworthy way, and it does not present the limitations found in those flowmeters based in other transduction methods. Moreover, due to the fact of not being in contact with the blood, it is not disposable and it does not need sterilization, reducing operational costs and facilitating its use.

  9. Influence of exercise induced hyperlactatemia on retinal blood flow during normo- and hyperglycemia.

    PubMed

    Garhöfer, Gerhard; Kopf, Andreas; Polska, Elzbieta; Malec, Magdalena; Dorner, Guido T; Wolzt, Michael; Schmetterer, Leopold

    2004-05-01

    Short term hyperglycemia has previously been shown to induce a blood flow increase in the retina. The mechanism behind this effect is poorly understood. We set out to investigate whether exercise-induced hyperlactatemia may alter the response of retinal blood flow to hyperglycemia. We performed a randomized, controlled two-way cross over study comprising 12 healthy subjects, performed a 6-minutes period of dynamic exercise during an euglcaemic or hyperglycaemic insulin clamp. Retinal blood flow was assessed by combined vessel size measurement with the Zeiss retinal vessel analyzer and measurement of red blood cell velocities using bi-directional laser Doppler velocimetry. Retinal and systemic hemodynamic parameters were measured before, immediately after and 10 and 20 minutes after isometric exercise. On the euglycemic study day retinal blood flow increased after dynamic exercise. The maximum increase in retinal blood flow was observed 10 minutes after the end of exercise when lactate plasma concentration peaked. Hyperglycemia increased retinal blood flow under basal conditions, but had no incremental effect during exercise induced hyperlactatemia. Our results indicate that both lactate and glucose induce an increase in retinal blood flow in healthy humans. This may indicate a common pathway between glucose and lactate induced blood flow changes in the human retina.

  10. Blood flow dynamics in heart failure

    NASA Technical Reports Server (NTRS)

    Shoemaker, J. K.; Naylor, H. L.; Hogeman, C. S.; Sinoway, L. I.

    1999-01-01

    BACKGROUND: Exercise intolerance in heart failure (HF) may be due to inadequate vasodilation, augmented vasoconstriction, and/or altered muscle metabolic responses that lead to fatigue. METHODS AND RESULTS: Vascular and metabolic responses to rhythmic forearm exercise were tested in 9 HF patients and 9 control subjects (CTL) during 2 protocols designed to examine the effect of HF on the time course of oxygen delivery versus uptake (protocol 1) and on vasoconstriction during exercise with 50 mm Hg pressure about the forearm to evoke a metaboreflex (protocol 2). In protocol 1, venous lactate and H+ were greater at 4 minutes of exercise in HF versus CTL (P<0.05) despite similar blood flow and oxygen uptake responses. In protocol 2, mean arterial pressure increased similarly in each group during ischemic exercise. In CTL, forearm blood flow and vascular conductance were similar at the end of ischemic and ambient exercise. In HF, forearm blood flow and vascular conductance were reduced during ischemic exercise compared with the ambient trial. CONCLUSIONS: Intrinsic differences in skeletal muscle metabolism, not vasodilatory dynamics, must account for the augmented glycolytic metabolic responses to moderate-intensity exercise in class II and III HF. The inability to increase forearm vascular conductance during ischemic handgrip exercise, despite a normal pressor response, suggests that enhanced vasoconstriction of strenuously exercising skeletal muscle contributes to exertional fatigue in HF.

  11. Effects of hypothyroidism on the skeletal muscle blood flow response to contractions.

    PubMed

    Bausch, L; McAllister, R M

    2003-04-01

    Hypothyroidism is associated with impaired blood flow to skeletal muscle under whole body exercise conditions. It is unclear whether poor cardiac and/or vascular function account for blunted muscle blood flow. Our experiment isolated a small group of hindlimb muscles and simulated exercise via tetanic contractions. We hypothesized that muscle blood flow would be attenuated in hypothyroid rats (HYPO) compared with euthyroid rats (EUT). Rats were made hypothyroid by mixing propylthiouracil in their drinking water (2.35 x 10-3 mol/l). Treatment efficacy was evidenced by lower serum T3 concentrations and resting heart rates in HYPO (both P<0.05). In the experimental preparation, isometric contractions of the lower right hindlimb muscles at a rate of 30 tetani/min were induced via sciatic nerve stimulation. Regional blood flows were determined by the radiolabelled microsphere method at three time points: rest, 2 min of contractions and 10 min of contractions. Muscle blood flow generally increased from rest ( approximately 5-10 ml/min per 100 g) through contractions for both groups. Further, blood flow during contractions did not differ between groups for any muscle (eg. red section of gastrocnemius muscle; EUT, 59.9 +/- 14.1; HYPO, 61.1 +/- 15.0; NS between groups). These findings indicate that hypothyroidism does not significantly impair skeletal muscle blood flow when only a small muscle mass is contracting. Our findings suggest that impaired blood flow under whole body exercise is accounted for by inadequate cardiac function rather than abnormal vascular function.

  12. The effects of hypoxemia on myocardial blood flow during exercise.

    PubMed

    Paridon, S M; Bricker, J T; Dreyer, W J; Reardon, M; Smith, E O; Porter, C B; Michael, L; Fisher, D J

    1989-03-01

    We evaluated the adequacy of regional and transmural blood flow during exercise and rapid pacing after 1 wk of hypoxemia. Seven mature mongrel dogs were made hypoxemic (mean O2 saturation = 72.4%) by anastomosis of left pulmonary artery to left atrial appendage. Catheters were placed in the left atrium, right atrium, pulmonary artery, and aorta. Atrial and ventricular pacing wires were placed. An aortic flow probe was placed to measure cardiac output. Ten nonshunted dogs, similarly instrumented, served as controls. Recovery time was approximately 1 wk. Cardiac output, mean aortic pressure, and oxygen saturation were measured at rest, with ventricular pacing, atrial pacing, and with treadmill exercise. Ventricular and atrial pace and exercise were at a heart rate of 200. Right ventricular free wall, left ventricular free wall, and septal blood flow were measured with radionuclide-labeled microspheres. Cardiac output, left atrial blood pressure, and aortic blood pressure were similar between the two groups of dogs in all testing states. Myocardial blood flow was significantly higher in the right and left ventricular free wall in the hypoxemic animals during resting and exercise testing states. Myocardial oxygen delivery was similar between the two groups of animals. Pacing resulted in an increase in myocardial blood flow in the control animals but not the hypoxemic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Methods for the determination of skeletal muscle blood flow: development, strengths and limitations.

    PubMed

    Gliemann, Lasse; Mortensen, Stefan P; Hellsten, Ylva

    2018-06-01

    Since the first measurements of limb blood flow at rest and during nerve stimulation were conducted in the late 1800s, a number of methods have been developed for the determination of limb and skeletal muscle blood flow in humans. The methods, which have been applied in the study of aspects such as blood flow regulation, oxygen uptake and metabolism, differ in terms of strengths and degree of limitations but most have advantages for specific settings. The purpose of this review is to describe the origin and the basic principles of the methods, important aspects and requirements of the procedures. One of the earliest methods, venous occlusion plethysmography, is a noninvasive method which still is extensively used and which provides similar values as other more direct blood flow methods such as ultrasound Doppler. The constant infusion thermodilution method remains the most appropriate for the determination of blood flow during maximal exercise. For resting blood flow and light-to-moderate exercise, the non-invasive ultrasound Doppler methodology, if handled by a skilled operator, is recommendable. Positron emission tomography with radiolabeled water is an advanced method which requires highly sophisticated equipment and allows for the determination of muscle-specific blood flow, regional blood flows and estimate of blood flow heterogeneity within a muscle. Finally, the contrast-enhanced ultrasound method holds promise for assessment of muscle-specific blood flow, but the interpretation of the data obtained remains uncertain. Currently lacking is high-resolution methods for continuous visualization and monitoring of the skeletal muscle microcirculation in humans.

  14. Simple Radiowave-Based Method For Measuring Peripheral Blood Flow Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J.

    2014-01-01

    Project objective is to design small radio frequency based flow probes for the measurement of blood flow velocity in peripheral arteries such as the femoral artery and middle cerebral artery. The result will be the technological capability to measure peripheral blood flow rates and flow changes during various environmental stressors such as microgravity without contact to the individual being monitored. This technology may also lead to an easier method of detecting venous gas emboli during extravehicular activities.

  15. Analysis of blood flow in the long posterior ciliary artery of the cat.

    PubMed

    Koss, M C

    1999-03-01

    Experiments were undertaken to use a new technique for direct on-line measurement of blood flow in the long posterior ciliary artery (LPCA) in cats and to evaluate possible physiological mechanisms controlling blood flow in the vascular beds perfused by this artery. Blood flow in the temporal LPCA was measured on a continuous basis using ultrasonic flowmetry in anesthetized cats. Effects of acute sectioning of the sympathetic nerve and changes in LPCA and cerebral blood flows in response to altered levels of inspired CO2 and O2 were tested in some animals. In others, the presence of vascular autoregulatory mechanisms in response to stepwise elevations of intraocular pressure was studied. Blood flow in the temporal LPCA averaged 0.58+/-0.03 ml/min in 45 cats anesthetized with pentobarbital. Basal LPCA blood flow was not altered by acute sectioning of the sympathetic nerve or by changes in low levels of inspired CO2 and O2, although 10% CO2 caused a modest increase. Stepwise elevations of intraocular pressure resulted in comparable stepwise decreases of LPCA blood flow, with perfusion pressure declining in a linear manner throughout the perfusion-pressure range. Ultrasonic flowmetry seems to be a useful tool for continuous on-line measurement of LPCA blood flow in the cat eye. Blood flow to vascular beds perfused by this artery does not seem to be under sympathetic neural control and is refractory to modest alterations of blood gas levels of CO2 and O2. Blood vessels perfused by the LPCA show no clear autoregulatory mechanisms.

  16. Facial skin blood flow responses during exposures to emotionally charged movies.

    PubMed

    Matsukawa, Kanji; Endo, Kana; Ishii, Kei; Ito, Momoka; Liang, Nan

    2018-03-01

    The changes in regional facial skin blood flow and vascular conductance have been assessed for the first time with noninvasive two-dimensional laser speckle flowmetry during audiovisually elicited emotional challenges for 2 min (comedy, landscape, and horror movie) in 12 subjects. Limb skin blood flow and vascular conductance and systemic cardiovascular variables were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by the subjective rating from -5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious). Facial skin blood flow and vascular conductance, especially in the lips, decreased during viewing of comedy and horror movies, whereas they did not change during viewing of a landscape movie. The decreases in facial skin blood flow and vascular conductance were the greatest with the comedy movie. The changes in lip, cheek, and chin skin blood flow negatively correlated (P < 0.05) with the subjective ratings of pleasantness and consciousness. The changes in lip skin vascular conductance negatively correlated (P < 0.05) with the subjective rating of pleasantness, while the changes in infraorbital, subnasal, and chin skin vascular conductance negatively correlated (P < 0.05) with the subjective rating of consciousness. However, none of the changes in limb skin blood flow and vascular conductance and systemic hemodynamics correlated with the subjective ratings. The mental arithmetic task did not alter facial and limb skin blood flows, although the task influenced systemic cardiovascular variables. These findings suggest that the more emotional status becomes pleasant or conscious, the more neurally mediated vasoconstriction may occur in facial skin blood vessels.

  17. An estimation of intracranial blood flow in the new-born infant.

    PubMed Central

    Cross, K W; Dear, P R; Hathorn, M K; Hyams, A; Kerslake, D M; Milligan, D W; Rahilly, P M; Stothers, J K

    1979-01-01

    1. A non-invasive method for the estimation of the intracranial blood flow of the new-born infant is described, and results obtained with it are presented. 2. The technique is a novel application of the principle of blood flow measurement by venous occlusion plethysmography. It is possible to apply a plethysmographic technique to the neonatal cranium because the presence of open sutures between the component bones permits small, but readily measurable, changes in intracranial volume to occur. 3. Skull volume changes are calculated from changes in the occipito-frontal circumference of the cranium as recorded and measured with a mercury-in-Silastic strain gauge. 4. The jugular veins in the baby's neck are occluded by finger pressure and there follows an increase in skull volume, which is rapid at first, but which decreases exponentially as venous drainage diverts to non-occluded channels such as the vertebral venous plexus. At the instant of jugular occlusion the rate of skull volume increase is representative of the rate of flow in the jugular vessels prior to occlusion, and so provides an index of the relative magnitude of the intracranial blood flow. The method thus allows changes in intracranial blood flow to be followed. When occlusion is released cranial volume decreases, initially rapidly, but slowing exponentially as resting volume is regained. 5. A theoretical model of the events occurring during the inflow and outflow phases has been developed, and a formula derived which allows an estimation to be made of the flow of blood through uncompressed channels. The measured value of jugular blood flow can then be augmented to an estimate of total intracranial flow. 6. The mean cerebral blood flow of sixteen normal babies was estimated to be 40 ml. 100 g-1.min-1 (S.D. = +/- 11.63). Images Fig. 2 Fig. 6 PMID:458665

  18. Whole-body vibration and blood flow and muscle oxygenation: a meta-analysis.

    PubMed

    Games, Kenneth E; Sefton, JoEllen M; Wilson, Alan E

    2015-05-01

    The use and popularity of whole-body vibration (WBV) has increased in recent years, but there is a lack of consensus in the literature about the effectiveness of the treatment. To quantitatively examine the effects of WBV on muscle oxygenation and peripheral blood flow in healthy adults. We searched Web of Science and PubMed databases and reference lists from relevant articles using the key terms whole body vibration, whole-body vibration, WBV, blood flow, peripheral blood flow, oxygenation, muscle oxygenation, circulation, circulatory, near infrared spectroscopy, NIRS, and power Doppler. Key terms were searched using single word and combination searches. No date range was specified. Criteria for inclusion were (1) use of a commercially available WBV device, (2) a human research model, (3) a pre-WBV condition and at least 1 WBV experimental condition, and (4) reporting of unstandardized means and standard deviations of muscle oxygenation or peripheral blood flow. Means, standard deviations, and sample sizes were extracted from the text, tables, and figures of included studies. A total of 35 and 90 data points were extracted for the muscle-oxygenation and blood-flow meta-analyses, respectively. Data for each meta-analysis were combined and analyzed using meta-analysis software. Weighted, random-effects meta-analyses using the Hedges g metric were completed for muscle oxygenation and blood flow. We then conducted follow-up analyses using the moderator variables of vibration type, vibration time, vibration frequency, measurement location, and sample type. We found 18 potential articles. Further examination yielded 10 studies meeting the inclusion criteria. Whole-body vibration was shown to positively influence peripheral blood flow. Additionally, the moderators of vibration type and frequency altered the influence of WBV on blood flow. Overall, WBV did not alter muscle oxygenation; however, when the measurement site was considered, muscle oxygenation increased or

  19. Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects

    PubMed Central

    Polska, E; Polak, K; Luksch, A; Fuchsjager-Mayrl, G; Petternel, V; Findl, O; Schmetterer, L

    2004-01-01

    Aims/background: To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours. Methods: The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. Results: None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%. Conclusions: These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency. PMID:15031172

  20. Elevated Skin Blood Flow Influences Near Infrared Spectroscopy Measurements During Supine Rest

    NASA Technical Reports Server (NTRS)

    Lee, Stuart M. C.; Clarke, Mark S. F.

    2004-01-01

    Near infrared spectroscopy is a non-invasive technique that allows determination of tissue oxygenation/blood flow based on spectrophotometric quantitation of oxy- and deoxyhemoglobin present within a tissue. This technique has gained acceptance as a means of detecting and quantifying changes in tissue blood flow due to physiological perturbation, such as that which is elicited in skeletal muscle during exercise. Since the NIRS technique requires light to penetrate the skin and subcutaneous fat in order to reach the muscle of interest, changes in skin blood flow may alter the NIRS signal in a fashion unrelated to blood flow in the muscle of interest. The aim of this study was to determine the contribution of skin blood flow to the NIRS signal obtained from resting vastus lateralis muscle of the thigh.

  1. Improving left ventricular segmentation in four-dimensional flow MRI using intramodality image registration for cardiac blood flow analysis.

    PubMed

    Gupta, Vikas; Bustamante, Mariana; Fredriksson, Alexandru; Carlhäll, Carl-Johan; Ebbers, Tino

    2018-01-01

    Assessment of blood flow in the left ventricle using four-dimensional flow MRI requires accurate left ventricle segmentation that is often hampered by the low contrast between blood and the myocardium. The purpose of this work is to improve left-ventricular segmentation in four-dimensional flow MRI for reliable blood flow analysis. The left ventricle segmentations are first obtained using morphological cine-MRI with better in-plane resolution and contrast, and then aligned to four-dimensional flow MRI data. This alignment is, however, not trivial due to inter-slice misalignment errors caused by patient motion and respiratory drift during breath-hold based cine-MRI acquisition. A robust image registration based framework is proposed to mitigate such errors automatically. Data from 20 subjects, including healthy volunteers and patients, was used to evaluate its geometric accuracy and impact on blood flow analysis. High spatial correspondence was observed between manually and automatically aligned segmentations, and the improvements in alignment compared to uncorrected segmentations were significant (P < 0.01). Blood flow analysis from manual and automatically corrected segmentations did not differ significantly (P > 0.05). Our results demonstrate the efficacy of the proposed approach in improving left-ventricular segmentation in four-dimensional flow MRI, and its potential for reliable blood flow analysis. Magn Reson Med 79:554-560, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  2. True color blood flow imaging using a high-speed laser photography system

    NASA Astrophysics Data System (ADS)

    Liu, Chien-Sheng; Lin, Cheng-Hsien; Sun, Yung-Nien; Ho, Chung-Liang; Hsu, Chung-Chi

    2012-10-01

    Physiological changes in the retinal vasculature are commonly indicative of such disorders as diabetic retinopathy, glaucoma, and age-related macular degeneration. Thus, various methods have been developed for noninvasive clinical evaluation of ocular hemodynamics. However, to the best of our knowledge, current ophthalmic instruments do not provide a true color blood flow imaging capability. Accordingly, we propose a new method for the true color imaging of blood flow using a high-speed pulsed laser photography system. In the proposed approach, monochromatic images of the blood flow are acquired using a system of three cameras and three color lasers (red, green, and blue). A high-quality true color image of the blood flow is obtained by assembling the monochromatic images by means of image realignment and color calibration processes. The effectiveness of the proposed approach is demonstrated by imaging the flow of mouse blood within a microfluidic channel device. The experimental results confirm the proposed system provides a high-quality true color blood flow imaging capability, and therefore has potential for noninvasive clinical evaluation of ocular hemodynamics.

  3. Photon activation-15O decay studies of tumor blood flow.

    PubMed

    Ten Haken, R K; Nussbaum, G H; Emami, B; Hughes, W L

    1981-01-01

    A direct, noninvasive method for measuring absolute values of specific capillary blood flow in living tissue is described. The method is based on the photon activation, in situ, of tissue elements and the measurement of the subsequent decay of the positron activity induced, employing coincidence detection of the photon pairs produced in positron annihilation. Analysis of the time-dependent coincidence spectrum reveals the contribution to the total signal from the decay of 15O, from which the specific capillary blood flow in the imaged, activated volume is ultimately determined. By virtue of its introduction of the radioisotope of interest (15O) directly and uniformly into the tissue volume under investigation, the method described permits both the nonperfused and well perfused fractions of an activated volume to be estimated and hence, the average specific blood flow within imaged tumor volumes to be computed. The model employed to describe and analyze the data is discussed in detail. Results of application of the technique to measurement of specific blood flow in rhabdomyosarcoma tumors grown in WAG/Rij rats are presented and discussed. The method is shown to be reliable and well suited to studies designed to determined the effects of various agents, such as heat, radiation and drugs, on tumor blood flow.

  4. Myo-inositol metabolism in appropriately grown and growth-restricted fetuses: a proton magnetic resonance spectroscopy study.

    PubMed

    Story, Lisa; Damodaram, Mellisa S; Supramaniam, Veena; Allsop, Joanna M; Mcguinness, Amy; Patel, Abhilasha; Wylezinska, Marzena; Kumar, Sailesh; Rutherford, Mary A

    2013-09-01

    Myo-inositol (Myo-ins) is a marker of neuroglial cells, being present in the astrocytes of brain tissue, but also functions as an osmolyte. Numbers of astrocytes are known to increase following injury to the brain. Growth-restricted fetuses are at increased risk of later neurodevelopmental impairments even in the absence of overt lesions and despite preserved/increased cerebral blood flow. This study aims to investigate brain Myo-ins metabolism in fetuses with intrauterine growth restriction (IUGR) and evidence of cerebral redistribution using magnetic resonance spectroscopy (MRS) at a short echo time. Biometry and Doppler assessment of blood flow was assessed using ultrasound in 28 fetuses with IUGR and 47 appropriately grown control subjects. MRI was used to exclude overt brain injury. Proton magnetic resonance spectroscopy of the fetal brain was then performed at an echo time of 42 ms to examine the Myo-ins:Choline (Cho), Myo-ins:Creatine (Cr) and Cho:Cr ratios. No alterations in brain Myo-ins:Cho, Myo-ins:Cr or Cho:Cr ratios were detected between appropriately grown and growth restricted fetuses. IUGR is not associated with a measureable difference in brain myo-inositol ratios. This may be due to the protective effects of preserved cerebral blood flow in growth restriction and comparable astrocyte numbers when compared to controls. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  5. Regulation of coronary blood flow during exercise.

    PubMed

    Duncker, Dirk J; Bache, Robert J

    2008-07-01

    Exercise is the most important physiological stimulus for increased myocardial oxygen demand. The requirement of exercising muscle for increased blood flow necessitates an increase in cardiac output that results in increases in the three main determinants of myocardial oxygen demand: heart rate, myocardial contractility, and ventricular work. The approximately sixfold increase in oxygen demands of the left ventricle during heavy exercise is met principally by augmenting coronary blood flow (~5-fold), as hemoglobin concentration and oxygen extraction (which is already 70-80% at rest) increase only modestly in most species. In contrast, in the right ventricle, oxygen extraction is lower at rest and increases substantially during exercise, similar to skeletal muscle, suggesting fundamental differences in blood flow regulation between these two cardiac chambers. The increase in heart rate also increases the relative time spent in systole, thereby increasing the net extravascular compressive forces acting on the microvasculature within the wall of the left ventricle, in particular in its subendocardial layers. Hence, appropriate adjustment of coronary vascular resistance is critical for the cardiac response to exercise. Coronary resistance vessel tone results from the culmination of myriad vasodilator and vasoconstrictors influences, including neurohormones and endothelial and myocardial factors. Unraveling of the integrative mechanisms controlling coronary vasodilation in response to exercise has been difficult, in part due to the redundancies in coronary vasomotor control and differences between animal species. Exercise training is associated with adaptations in the coronary microvasculature including increased arteriolar densities and/or diameters, which provide a morphometric basis for the observed increase in peak coronary blood flow rates in exercise-trained animals. In larger animals trained by treadmill exercise, the formation of new capillaries maintains

  6. The Effect of Pulsatile Versus Nonpulsatile Blood Flow on Viscoelasticity and Red Blood Cell Aggregation in Extracorporeal Circulation

    PubMed Central

    Ahn, Chi Bum; Kang, Yang Jun; Kim, Myoung Gon; Yang, Sung; Lim, Choon Hak; Son, Ho Sung; Kim, Ji Sung; Lee, So Young; Son, Kuk Hui; Sun, Kyung

    2016-01-01

    Background Extracorporeal circulation (ECC) can induce alterations in blood viscoelasticity and cause red blood cell (RBC) aggregation. In this study, the authors evaluated the effects of pump flow pulsatility on blood viscoelasticity and RBC aggregation. Methods Mongrel dogs were randomly assigned to two groups: a nonpulsatile pump group (n=6) or a pulsatile pump group (n=6). After ECC was started at a pump flow rate of 80 mL/kg/min, cardiac fibrillation was induced. Blood sampling was performed before and at 1, 2, and 3 hours after ECC commencement. To eliminate bias induced by hematocrit and plasma, all blood samples were adjusted to a hematocrit of 45% using baseline plasma. Blood viscoelasticity, plasma viscosity, hematocrit, arterial blood gas analysis, central venous O2 saturation, and lactate were measured. Results The blood viscosity and aggregation index decreased abruptly 1 hour after ECC and then remained low during ECC in both groups, but blood elasticity did not change during ECC. Blood viscosity, blood elasticity, plasma viscosity, and the aggregation index were not significantly different in the groups at any time. Hematocrit decreased abruptly 1 hour after ECC in both groups due to dilution by the priming solution used. Conclusion After ECC, blood viscoelasticity and RBC aggregation were not different in the pulsatile and nonpulsatile groups in the adult dog model. Furthermore, pulsatile flow did not have a more harmful effect on blood viscoelasticity or RBC aggregation than nonpulsatile flow. PMID:27298790

  7. The Effect of Pulsatile Versus Nonpulsatile Blood Flow on Viscoelasticity and Red Blood Cell Aggregation in Extracorporeal Circulation.

    PubMed

    Ahn, Chi Bum; Kang, Yang Jun; Kim, Myoung Gon; Yang, Sung; Lim, Choon Hak; Son, Ho Sung; Kim, Ji Sung; Lee, So Young; Son, Kuk Hui; Sun, Kyung

    2016-06-01

    Extracorporeal circulation (ECC) can induce alterations in blood viscoelasticity and cause red blood cell (RBC) aggregation. In this study, the authors evaluated the effects of pump flow pulsatility on blood viscoelasticity and RBC aggregation. Mongrel dogs were randomly assigned to two groups: a nonpulsatile pump group (n=6) or a pulsatile pump group (n=6). After ECC was started at a pump flow rate of 80 mL/kg/min, cardiac fibrillation was induced. Blood sampling was performed before and at 1, 2, and 3 hours after ECC commencement. To eliminate bias induced by hematocrit and plasma, all blood samples were adjusted to a hematocrit of 45% using baseline plasma. Blood viscoelasticity, plasma viscosity, hematocrit, arterial blood gas analysis, central venous O2 saturation, and lactate were measured. The blood viscosity and aggregation index decreased abruptly 1 hour after ECC and then remained low during ECC in both groups, but blood elasticity did not change during ECC. Blood viscosity, blood elasticity, plasma viscosity, and the aggregation index were not significantly different in the groups at any time. Hematocrit decreased abruptly 1 hour after ECC in both groups due to dilution by the priming solution used. After ECC, blood viscoelasticity and RBC aggregation were not different in the pulsatile and nonpulsatile groups in the adult dog model. Furthermore, pulsatile flow did not have a more harmful effect on blood viscoelasticity or RBC aggregation than nonpulsatile flow.

  8. Renal blood flow and oxygenation drive nephron progenitor differentiation.

    PubMed

    Rymer, Christopher; Paredes, Jose; Halt, Kimmo; Schaefer, Caitlin; Wiersch, John; Zhang, Guangfeng; Potoka, Douglas; Vainio, Seppo; Gittes, George K; Bates, Carlton M; Sims-Lucas, Sunder

    2014-08-01

    During kidney development, the vasculature develops via both angiogenesis (branching from major vessels) and vasculogenesis (de novo vessel formation). The formation and perfusion of renal blood vessels are vastly understudied. In the present study, we investigated the regulatory role of renal blood flow and O2 concentration on nephron progenitor differentiation during ontogeny. To elucidate the presence of blood flow, ultrasound-guided intracardiac microinjection was performed, and FITC-tagged tomato lectin was perfused through the embryo. Kidneys were costained for the vasculature, ureteric epithelium, nephron progenitors, and nephron structures. We also analyzed nephron differentiation in normoxia compared with hypoxia. At embryonic day 13.5 (E13.5), the major vascular branches were perfused; however, smaller-caliber peripheral vessels remained unperfused. By E15.5, peripheral vessels started to be perfused as well as glomeruli. While the interior kidney vessels were perfused, the peripheral vessels (nephrogenic zone) remained unperfused. Directly adjacent and internal to the nephrogenic zone, we found differentiated nephron structures surrounded and infiltrated by perfused vessels. Furthermore, we determined that at low O2 concentration, little nephron progenitor differentiation was observed; at higher O2 concentrations, more differentiation of the nephron progenitors was induced. The formation of the developing renal vessels occurs before the onset of blood flow. Furthermore, renal blood flow and oxygenation are critical for nephron progenitor differentiation. Copyright © 2014 the American Physiological Society.

  9. Optic nerve head blood flow response to reduced ocular perfusion pressure by alteration of either the blood pressure or intraocular pressure.

    PubMed

    Wang, Lin; Cull, Grant A; Fortune, Brad

    2015-04-01

    To test the hypothesis that blood flow autoregulation in the optic nerve head has less reserve to maintain normal blood flow in the face of blood pressure-induced ocular perfusion pressure decrease than a similar magnitude intraocular pressure-induced ocular perfusion pressure decrease. Twelve normal non-human primates were anesthetized by continuous intravenous infusion of pentobarbital. Optic nerve blood flow was monitored by laser speckle flowgraphy. In the first group of animals (n = 6), the experimental eye intraocular pressure was maintained at 10 mmHg using a saline reservoir connected to the anterior chamber. The blood pressure was gradually reduced by a slow injection of pentobarbital. In the second group (n = 6), the intraocular pressure was slowly increased from 10 mmHg to 50 mmHg by raising the reservoir. In both experimental groups, optic nerve head blood flow was measured continuously. The blood pressure and intraocular pressure were simultaneously recorded in all experiments. The optic nerve head blood flow showed significant difference between the two groups (p = 0.021, repeat measures analysis of variance). It declined significantly more in the blood pressure group compared to the intraocular pressure group when the ocular perfusion pressure was reduced to 35 mmHg (p < 0.045) and below. There was also a significant interaction between blood flow changes and the ocular perfusion pressure treatment (p = 0.004, adjusted Greenhouse & Geisser univariate test), indicating the gradually enlarged blood flow difference between the two groups was due to the ocular perfusion pressure decrease. The results show that optic nerve head blood flow is more susceptible to an ocular perfusion pressure decrease induced by lowering the blood pressure compared with that induced by increasing the intraocular pressure. This blood flow autoregulation capacity vulnerability to low blood pressure may provide experimental evidence related to the

  10. Analysis of Hepatic Blood Flow Using Chaotic Models

    PubMed Central

    Cohen, M. E.; Moazamipour, H.; Hudson, D. L.; Anderson, M. F.

    1990-01-01

    The study of chaos in physical systems is an important new theoretical development in modeling which has emerged in the last fifteen years. It is particularly useful in explaining phenomena which arise in nonlinear dynamic systems, for which previous mathematical models produced results with intractable solutions. Analysis of blood flow is such an application. In the work described here, chaotic models are used to analyze hepatic artery and portal vein blood flow obtained from a pulsed Doppler ultrasonic flowmeter implanted in dogs. ImagesFigure 3

  11. Simulation of blood flow in a small-diameter vascular graft model with a swirl (spiral) flow guider.

    PubMed

    Zhang, ZhiGuo; Fan, YuBo; Deng, XiaoYan; Wang, GuiXue; Zhang, He; Guidoin, Robert

    2008-10-01

    Small-diameter vascular grafts are in large demand for coronary and peripheral bypass procedures, but present products still fail in long-term clinical application. In the present communication, a new type of small-diameter graft with a swirl flow guider was proposed to improve graft patency rate. Flow pattern in the graft was simulated numerically and compared with that in a conventional graft. The numerical results revealed that the swirl flow guider could indeed make the blood flow rotate in the new graft. The swirling flow distal to the flow guider significantly altered the flow pattern in the new graft and the velocity profiles were re-distributed. Due to the swirling flow, the blood velocity near the vessel wall and wall shear rate were greatly enhanced. We believe that the increased blood velocity near the wall and the wall shear rate can impede the occurrence of acute thrombus formation and intimal hyperplasia, hence can improve the graft patency rate for long-term clinical use.

  12. Modeling and Control of Airport Queueing Dynamics under Severe Flow Restrictions

    NASA Technical Reports Server (NTRS)

    Carr, Francis; Evans, Antony; Clarke, John-Paul; Deron, Eric

    2003-01-01

    Based on field observations and interviews with controllers at BOS and EWR, we identify the closure of local departure fixes as the most severe class of airport departure restrictions. A set of simple queueing dynamics and traffic rules are developed to model departure traffic under such restrictions. The validity of the proposed model is tested via Monte Carlo simulation against 10 hours of actual operations data collected during a case-study at EWR on June 29,2000. In general, the model successfully reproduces the aggregate departure congestion. An analysis of the average error over 40 simulation runs indicates that flow-rate restrictions also significantly impact departure traffic; work is underway to capture these effects. Several applications and what-if scenarios are discussed for future evaluation using the calibrated model.

  13. A numerical study of blood flow using mixture theory

    PubMed Central

    Wu, Wei-Tao; Aubry, Nadine; Massoudi, Mehrdad; Kim, Jeongho; Antaki, James F.

    2014-01-01

    In this paper, we consider the two dimensional flow of blood in a rectangular microfluidic channel. We use Mixture Theory to treat this problem as a two-component system: One component is the red blood cells (RBCs) modeled as a generalized Reiner–Rivlin type fluid, which considers the effects of volume fraction (hematocrit) and influence of shear rate upon viscosity. The other component, plasma, is assumed to behave as a linear viscous fluid. A CFD solver based on OpenFOAM® was developed and employed to simulate a specific problem, namely blood flow in a two dimensional micro-channel, is studied. Finally to better understand this two-component flow system and the effects of the different parameters, the equations are made dimensionless and a parametric study is performed. PMID:24791016

  14. A numerical study of blood flow using mixture theory.

    PubMed

    Wu, Wei-Tao; Aubry, Nadine; Massoudi, Mehrdad; Kim, Jeongho; Antaki, James F

    2014-03-01

    In this paper, we consider the two dimensional flow of blood in a rectangular microfluidic channel. We use Mixture Theory to treat this problem as a two-component system: One component is the red blood cells (RBCs) modeled as a generalized Reiner-Rivlin type fluid, which considers the effects of volume fraction (hematocrit) and influence of shear rate upon viscosity. The other component, plasma, is assumed to behave as a linear viscous fluid. A CFD solver based on OpenFOAM ® was developed and employed to simulate a specific problem, namely blood flow in a two dimensional micro-channel, is studied. Finally to better understand this two-component flow system and the effects of the different parameters, the equations are made dimensionless and a parametric study is performed.

  15. [Effect of caffeine on myocardial blood flow during pharmacological vasodilation].

    PubMed

    Wielepp, J P; Fricke, E; Horstkotte, D; Burchert, W

    2005-02-01

    Pharmacologic stress with adenosine is frequently used for noninvasive detection of coronary artery disease. Dietary intake of caffeinated food, beverages or medications might alter adenosine-induced hyperemic blood flow, thereby compromising the diagnostic sensitivity of adenosine stress testing. In this case we report on a male patient with CAD. Myocardial blood flow at rest and during adenosine-induced hyperemia 2 hours after consumption of decaffeinated coffee and again without caffeine intake were quantified by ammonia PET. After caffeine intake there was a clearly diminished increase of myocardial blood flow during adenosine. The average coronary flow reserve in the myocardium was 1.3 after caffeine. In the baseline study without caffeine the coronary flow reserve has been improved to 2.3. Caffeine intake alters the coronary vasodilatory capacity. These findings emphasize the importance of carefully screening patients for intake of caffeinated food prior to adenosine stress testing.

  16. Role of sodium-restricted dietary approaches to control blood pressure in Pakistani hypertensive population.

    PubMed

    Naseem, Sajida; Ghazanfar, Haider; Assad, Salman; Ghazanfar, Ali

    2016-07-01

    To assess the change in systolic and diastolic blood pressure in post-interventional phase through dietary approaches to stop hypertension/salt-restricted diet. This randomised controlled clinical study was conducted from February 2014 to March 2015 at the Armed Forces Institute of Cardiology, Rawalpindi, and Ali Medical Centre, Islamabad, Pakistan, and involved hypertensive patients and matching controls. The control group followed routine diet while the intervention group was given a diet plan containing 1,500mg of sodium providing 2,000 calories. Both groups were advised not to consume sodium-rich foods. Paired sample t-test was applied to determine the change in blood pressure among the groups at two different occasions. Of the 1,492 participants, 710(47.6%) were controls and 782(52.4%) were in the interventional group. Overall, 417(27.9%) participants got their blood pressure checked less than twice in six months, while 409(27.4%) had it done on a regular basis. Moreover, 941(63.1%)) subjects had a family history of high blood pressure and 149(10.0%) participants did not exercise at all. The overall mean age was 53.42±9.302 years. Mean systolic blood pressure and diastolic blood pressure after five weeks was 126.33±3.35 and 84.40±3.04mmHg in the intervention group, and128.41±3.52 and 84.04±2.953mmHg in the control group. Changes in blood pressure between the two groups were minimal but statistically significant (p<0.05). A diet which is restricted in salt, rich in fruits, vegetables, and low-fat dairy foods and reduced saturated and total fat can substantially lower blood pressure. Such a diet offers an additional nutritional approach to the prevention and treatment of hypertension.

  17. Neural Vascular Mechanism for the Cerebral Blood Flow Autoregulation after Hemorrhagic Stroke.

    PubMed

    Xiao, Ming; Li, Qiang; Feng, Hua; Zhang, Le; Chen, Yujie

    2017-01-01

    During the initial stages of hemorrhagic stroke, including intracerebral hemorrhage and subarachnoid hemorrhage, the reflex mechanisms are activated to protect cerebral perfusion, but secondary dysfunction of cerebral flow autoregulation will eventually reduce global cerebral blood flow and the delivery of metabolic substrates, leading to generalized cerebral ischemia, hypoxia, and ultimately, neuronal cell death. Cerebral blood flow is controlled by various regulatory mechanisms, including prevailing arterial pressure, intracranial pressure, arterial blood gases, neural activity, and metabolic demand. Evoked by the concept of vascular neural network, the unveiled neural vascular mechanism gains more and more attentions. Astrocyte, neuron, pericyte, endothelium, and so forth are formed as a communicate network to regulate with each other as well as the cerebral blood flow. However, the signaling molecules responsible for this communication between these new players and blood vessels are yet to be definitively confirmed. Recent evidence suggested the pivotal role of transcriptional mechanism, including but not limited to miRNA, lncRNA, exosome, and so forth, for the cerebral blood flow autoregulation. In the present review, we sought to summarize the hemodynamic changes and underline neural vascular mechanism for cerebral blood flow autoregulation in stroke-prone state and after hemorrhagic stroke and hopefully provide more systematic and innovative research interests for the pathophysiology and therapeutic strategies of hemorrhagic stroke.

  18. Factors associated with respiration induced variability in cerebral blood flow velocity.

    PubMed Central

    Coughtrey, H; Rennie, J M; Evans, D H; Cole, T J

    1993-01-01

    A consecutive cohort of 73 very low birthweight infants was studied to determine the presence or absence of beat to beat variability in the velocity of blood flow in the cerebral circulation and its relation with respiration. One minute epochs of information included recordings of cerebral blood flow velocity estimated with Doppler ultrasound, blood pressure, spontaneous respiratory activity, and ventilator cycling. Fourier transformation was used to resolve the frequencies present within the one minute epochs and to classify the cerebral blood flow velocity as showing the presence or absence of any respiratory associated variability. A total of 249 recordings was made on days 1, 2, 3, and 7. Forty seven infants showed respiratory variability in cerebral blood flow velocity on 97 occasions, usually during the first day of life. The infants with respiratory associated variability were of lower gestational age and when the respiratory associated variability was present they were more likely to be ventilated and receiving higher inspired oxygen; these associations were shown to be independent of gestational age. There was no significant independent association with brain injury, cerebral blood flow velocity (cm/s), or blood pressure (mm Hg). The findings suggest that artificial ventilation may entrain normal respiratory associated variability in the cerebral circulation but do not provide evidence that it is harmful. PMID:8466269

  19. Relationship between preoperative radial artery and postoperative arteriovenous fistula blood flow in hemodialysis patients.

    PubMed

    Sato, Michiko; Io, Hiroaki; Tanimoto, Mitsuo; Shimizu, Yoshio; Fukui, Mitsumine; Hamada, Chieko; Horikoshi, Satoshi; Tomino, Yasuhiko

    2012-01-01

    It is recommended that arteriovenous fistula (AVF) blood flow should be more than 425 ml/min before cannulation. However, the relationship between preoperative radial artery flow (RAF) and postoperative AVF blood flow has still not been examined. Sixty-one patients with end-stage kidney disease (ESKD) were examined. They had an AVF prepared at Juntendo University Hospital from July 2006 through August 2007. Preoperative RAF and postoperative AVF blood flows were measured by ultrasonography. AVF blood flow gradually increased after the operation. AVF blood flow was significantly correlated with preoperative RAF. When preoperative RAF exceeded 21.4 ml/min, AVF blood flow rose to more than 425 ml/min. The postoperative AVF blood flow in the group with RAF of more than 20 ml/min was significantly higher than that in those with less than 20 ml/min. Preoperative RAF of less than 20 ml/min had a significantly high risk of primary AVF failure within 8 months compared with that of more than 20 ml/min. It appears that measurement of RAF by ultrasonography is useful for estimating AVF blood flow postoperatively and can predict the risk of complications in ESKD patients.

  20. Evidence for altered placental blood flow and vascularity in compromised pregnancies

    PubMed Central

    Reynolds, Lawrence P; Caton, Joel S; Redmer, Dale A; Grazul-Bilska, Anna T; Vonnahme, Kimberly A; Borowicz, Pawel P; Luther, Justin S; Wallace, Jacqueline M; Wu, Guoyao; Spencer, Thomas E

    2006-01-01

    The placenta is the organ that transports nutrients, respiratory gases, and wastes between the maternal and fetal systems. Consequently, placental blood flow and vascular development are essential components of normal placental function and are critical to fetal growth and development. Normal fetal growth and development are important to ensure optimum health of offspring throughout their subsequent life course. In numerous sheep models of compromised pregnancy, in which fetal or placental growth, or both, are impaired, utero-placental blood flows are reduced. In the models that have been evaluated, placental vascular development also is altered. Recent studies found that treatments designed to increase placental blood flow can ‘rescue’ fetal growth that was reduced due to low maternal dietary intake. Placental blood flow and vascular development are thus potential therapeutic targets in compromised pregnancies. PMID:16469783

  1. Effects of endothelium-derived nitric oxide on skin and digital blood flow in humans.

    PubMed

    Coffman, J D

    1994-12-01

    The effects of NG-monomethyl-L-arginine (L-NMMA) on total finger and forearm, and dorsal finger and forearm skin, blood flows were studied in the basal state and during reflex sympathetic vasoconstriction in normal subjects. Total flows were measured by venous occlusion plethysmography and skin flows by laser-Doppler flowmetry (LDF). L-NMMA in doses of 2, 4, and 8 microM/min given by constant infusion via a brachial artery catheter significantly decreased finger blood flow, forearm blood flow, and vascular conductances. At 8 microM/min, total finger blood flow decreased 38.4% and forearm blood flow decreased 24.8%. Dorsal finger and forearm skin LDF were also significantly decreased (25 and 37% at 8 microM/min). Body cooling significantly decreased finger blood flow (73.6%), vascular conductance, and finger LDF (59.7%). L-NMMA had no effect on total finger blood flow or dorsal finger LDF during body cooling. Nitric oxide or related compounds contribute to the basal dilator tone of the dorsal finger and forearm skin but not during reflex sympathetic vasoconstriction.

  2. Whole-Body Vibration and Blood Flow and Muscle Oxygenation: A Meta-Analysis

    PubMed Central

    Games, Kenneth E.; Sefton, JoEllen M.; Wilson, Alan E.

    2015-01-01

    Context: The use and popularity of whole-body vibration (WBV) has increased in recent years, but there is a lack of consensus in the literature about the effectiveness of the treatment. Objective: To quantitatively examine the effects of WBV on muscle oxygenation and peripheral blood flow in healthy adults. Data Sources: We searched Web of Science and PubMed databases and reference lists from relevant articles using the key terms whole body vibration, whole-body vibration, WBV, blood flow, peripheral blood flow, oxygenation, muscle oxygenation, circulation, circulatory, near infrared spectroscopy, NIRS, and power Doppler. Key terms were searched using single word and combination searches. No date range was specified. Study Selection: Criteria for inclusion were (1) use of a commercially available WBV device, (2) a human research model, (3) a pre-WBV condition and at least 1 WBV experimental condition, and (4) reporting of unstandardized means and standard deviations of muscle oxygenation or peripheral blood flow. Data Extraction: Means, standard deviations, and sample sizes were extracted from the text, tables, and figures of included studies. A total of 35 and 90 data points were extracted for the muscle-oxygenation and blood-flow meta-analyses, respectively. Data for each meta-analysis were combined and analyzed using meta-analysis software. Weighted, random-effects meta-analyses using the Hedges g metric were completed for muscle oxygenation and blood flow. We then conducted follow-up analyses using the moderator variables of vibration type, vibration time, vibration frequency, measurement location, and sample type. Data Synthesis: We found 18 potential articles. Further examination yielded 10 studies meeting the inclusion criteria. Whole-body vibration was shown to positively influence peripheral blood flow. Additionally, the moderators of vibration type and frequency altered the influence of WBV on blood flow. Overall, WBV did not alter muscle oxygenation

  3. Research Advances: DRPS--Let The Blood Flow!

    ERIC Educational Resources Information Center

    King, Angela G.

    2007-01-01

    A team from the University of Pittsburgh's McGowan Institute for Regenerative Medicine has shown the potential for clinical use of the drag-reducing polymer (DRP) poly(N-vinylformamide), or PNVF. The high molecular weight PNVF is shown to reduce resistance to turbulent flow in a pipe and to enhance blood flow in animal models and it also…

  4. Simultaneous imaging of blood flow dynamics and vascular remodelling during development.

    PubMed

    Ghaffari, Siavash; Leask, Richard L; Jones, Elizabeth A V

    2015-12-01

    Normal vascular development requires blood flow. Time-lapse imaging techniques have revolutionised our understanding of developmental biology, but measuring changes in blood flow dynamics has met with limited success. Ultrasound biomicroscopy and optical coherence tomography can concurrently image vascular structure and blood flow velocity, but these techniques lack the resolution to accurately calculate fluid forces such as shear stress. This is important because hemodynamic forces are biologically active and induce changes in the expression of genes important for vascular development. Regional variations in shear stress, rather than the overall level, control processes such as vessel enlargement and regression during vascular remodelling. We present a technique to concurrently visualise vascular remodelling and blood flow dynamics. We use an avian embryonic model and inject an endothelial-specific dye and fluorescent microspheres. The motion of the microspheres is captured with a high-speed camera and the velocity of the blood flow in and out of the region of interest is quantified by micro-particle image velocitymetry (µPIV). The vessel geometry and flow are used to numerically solve the flow physics with computational fluid dynamics (CFD). Using this technique, we can analyse changes in shear stress, pressure drops and blood flow velocities over a period of 10 to 16 h. We apply this to study the relationship between shear stress and chronic changes in vessel diameter during embryonic development, both in normal development and after TGFβ stimulation. This technique allows us to study the interaction of biomolecular and biomechanical signals during vascular remodelling using an in vivo developmental model. © 2015. Published by The Company of Biologists Ltd.

  5. Transcutaneous measurement of volume blood flow

    NASA Technical Reports Server (NTRS)

    Daigle, R. E.; Mcleod, F. D.; Miller, C. W.; Histand, M. B.; Wells, M. K.

    1974-01-01

    Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated.

  6. Viral infection potentiates the increase in airway blood flow produced by substance P.

    PubMed

    Yamawaki, I; Geppetti, P; Bertrand, C; Chan, B; Massion, P; Piedimonte, G; Nadel, J A

    1995-08-01

    We examined the effect of respiratory tract infection with Sendai virus on the responsiveness of airway blood flow to substance P (SP) in rats. Pathogen-free rats were inoculated with either Sendai virus suspension or sterile viral growth medium into each nostril. Five days later, we measured airway and esophageal blood flows before and immediately after injection of SP or histamine into the left ventricle of rats in both groups using a modification of the reference-sample microsphere technique. Viral infection potentiated the increase in airway blood flow evoked by SP but not by histamine. We also examined the effect of neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) on the SP-induced increase in airway blood flow. Both phosphoramidon (NEP inhibitor) and captopril (ACE inhibitor) potentiated the increase in airway blood flow produced by SP in pathogen-free rats. In the presence of both peptidase inhibitors, a submaximal dose of SP increased blood flow to a similar level in infected and pathogen-free rats. Thus decreased activity of both ACE and NEP may be involved in the exaggerated increase in airway blood flow evoked by SP in virus-infected rats.

  7. A multiple disk centrifugal pump as a blood flow device.

    PubMed

    Miller, G E; Etter, B D; Dorsi, J M

    1990-02-01

    A multiple disk, shear force, valveless centrifugal pump was studied to determine its suitability as a blood flow device. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared to a Harvard Apparatus pulsatile piston pump. Both pumps were connected to an artificial circulatory system. Frequency and systolic duration were varied over a range of physiological conditions for both pumps. The results indicated that the Tesla pump, operating in a pulsatile mode, is capable of producing physiologic pressures and flows similar to the Harvard pump and other pulsatile blood pumps.

  8. A novel method to measure regional muscle blood flow continuously using NIRS kinetics information

    PubMed Central

    Nioka, Shoko; Kime, Ryotaro; Sunar, Ulas; Im, Joohee; Izzetoglu, Meltem; Zhang, Jun; Alacam, Burak; Chance, Britton

    2006-01-01

    Background This article introduces a novel method to continuously monitor regional muscle blood flow by using Near Infrared Spectroscopy (NIRS). We demonstrate the feasibility of the new method in two ways: (1) by applying this new method of determining blood flow to experimental NIRS data during exercise and ischemia; and, (2) by simulating muscle oxygenation and blood flow values using these newly developed equations during recovery from exercise and ischemia. Methods Deoxy (Hb) and oxyhemoglobin (HbO2), located in the blood ofthe skeletal muscle, carry two internal relationships between blood flow and oxygen consumption. One is a mass transfer principle and the other describes a relationship between oxygen consumption and Hb kinetics in a two-compartment model. To monitor blood flow continuously, we transfer these two relationships into two equations and calculate the blood flow with the differential information of HbO2 and Hb. In addition, these equations are used to simulate the relationship between blood flow and reoxygenation kinetics after cuff ischemia and a light exercise. Nine healthy subjects volunteered for the cuff ischemia, light arm exercise and arm exercise with cuff ischemia for the experimental study. Results Analysis of experimental data of both cuff ischemia and light exercise using the new equations show greater blood flow (four to six times more than resting values) during recovery, agreeing with previous findings. Further, the simulation and experimental studies of cuff ischemia and light exercise agree with each other. Conclusion We demonstrate the accuracy of this new method by showing that the blood flow obtained from the method agrees with previous data as well as with simulated data. We conclude that this novel continuous blood flow monitoring method can provide blood flow information non-invasively with NIRS. PMID:16704736

  9. Bone Blood Flow During Simulated Microgravity: Physiological and Molecular Mechanisms

    NASA Technical Reports Server (NTRS)

    Bloomfield, Susan A.

    1999-01-01

    Blood flow to bone has been shown to affect bone mass and presumably bone strength. Preliminary data indicate that blood flow to the rat femur decreases after 14 days of simulated microgravity, using hindlimb suspension (HLS). If adult rats subjected to HLS are given dobutamine, a synthetic catecholamine which can cause peripheral vasodilation and increased blood flow, the loss of cortical bone area usually observed is prevented. Further, mechanisms exist at the molecular level to link changes in bone blood flow to changes in bone cell activity, particularly for vasoactive agents like nitric oxide (NO). The decreases in fluid shear stress created by fluid flow associated with the shifts of plasma volume during microgravity may result in alterations in expression of vasoactive agents such as NO, producing important functional effects on bone cells. The primary aim of this project is to characterize changes in 1) bone blood flow, 2) indices of bone mass, geometry, and strength, and 3) changes in gene expression for modulators of nitric oxide activity (e.g., nitric oxide synthase) and other candidate genes involved in signal transduction of mechanical loading after 3, 7, 14, 21, and 28 days of HLS in the adult rat. Using a rat of at least 5 months of age avoids inadvertently studying effects of simulated microgravity on growing, rather than adult, bone. Utilizing the results of these studies, we will then define how altered blood flow contributes to changes in bone with simulated microgravity by administering a vasodilatory agent (which increases blood flow to tissues) during hindlimb suspension. In all studies, responses in the unloaded hindlimb bones (tibial shaft, femoral neck) will be compared with those in the weightbearing humeral shaft and the non-weightbearing calvarium (skull) from the same animal. Bone volumetric mineral density and geometry will be quantified by peripheral quantitative CT; structural and material properties of the long bones will be

  10. Reduction in unnecessary red blood cell folate testing by restricting computerized physician order entry in the electronic health record.

    PubMed

    MacMillan, Thomas E; Gudgeon, Patrick; Yip, Paul M; Cavalcanti, Rodrigo B

    2018-05-02

    Red blood cell folate is a laboratory test with limited clinical utility. Previous attempts to reduce physician ordering of unnecessary laboratory tests, including folate, have resulted in only modest success. The objective of this study was to assess the effectiveness and impacts of restricting red blood cell folate ordering in the electronic health record. This was a retrospective observational study from January 2010 to December 2016 at a large academic healthcare network in Toronto, Canada. All inpatients and outpatients who underwent at least 1 red blood cell folate or vitamin B12 test during the study period were included. Red blood cell folate ordering was restricted to clincians in gastroenterology and hematology and was removed from other physicians' computerized order entry screen in the electronic health record in June 2013. Red blood cell folate testing decreased by 94.4% during the study, from a mean of 493.0 (SD 48.0) tests/month before intervention to 27.6 (SD 10.3) tests/month after intervention (P<.001). Restricting red blood cell folate ordering in the electronic health record resulted in a large and sustained reduction in red blood cell folate testing. Significant cost savings estimated at over a quarter-million dollars (CAD) over three years were achieved. There was no significant clinical impact of the intervention on the diagnosis of folate deficiency. Copyright © 2018. Published by Elsevier Inc.

  11. Usage of CO2 microbubbles as flow-tracing contrast media in X-ray dynamic imaging of blood flows.

    PubMed

    Lee, Sang Joon; Park, Han Wook; Jung, Sung Yong

    2014-09-01

    X-ray imaging techniques have been employed to visualize various biofluid flow phenomena in a non-destructive manner. X-ray particle image velocimetry (PIV) was developed to measure velocity fields of blood flows to obtain hemodynamic information. A time-resolved X-ray PIV technique that is capable of measuring the velocity fields of blood flows under real physiological conditions was recently developed. However, technical limitations still remained in the measurement of blood flows with high image contrast and sufficient biocapability. In this study, CO2 microbubbles as flow-tracing contrast media for X-ray PIV measurements of biofluid flows was developed. Human serum albumin and CO2 gas were mechanically agitated to fabricate CO2 microbubbles. The optimal fabricating conditions of CO2 microbubbles were found by comparing the size and amount of microbubbles fabricated under various operating conditions. The average size and quantity of CO2 microbubbles were measured by using a synchrotron X-ray imaging technique with a high spatial resolution. The quantity and size of the fabricated microbubbles decrease with increasing speed and operation time of the mechanical agitation. The feasibility of CO2 microbubbles as a flow-tracing contrast media was checked for a 40% hematocrit blood flow. Particle images of the blood flow were consecutively captured by the time-resolved X-ray PIV system to obtain velocity field information of the flow. The experimental results were compared with a theoretically amassed velocity profile. Results show that the CO2 microbubbles can be used as effective flow-tracing contrast media in X-ray PIV experiments.

  12. Acute reductions in blood flow restricted to the dorsomedial medulla induce a pressor response in rats.

    PubMed

    Waki, Hidefumi; Bhuiyan, Mohammad E R; Gouraud, Sabine S; Takagishi, Miwa; Hatada, Atsutoshi; Kohsaka, Akira; Paton, Julian F R; Maeda, Masanobu

    2011-08-01

    The brainstem nucleus of the solitary tract (nucleus tractus solitarii, NTS) is a pivotal region for regulating the set-point of arterial pressure, the mechanisms of which are not fully understood. Based on evidence that the NTS exhibits O2-sensing mechanisms, we examined whether a localized disturbance of blood supply, resulting in hypoxia in the NTS, would lead to an acute increase in arterial pressure. Male Wistar rats were used. Cardiovascular parameters were measured before and after specific branches of superficial dorsal medullary veins were occluded; we assumed these were drainage vessels from the NTS and would produce stagnant hypoxia. Hypoxyprobe-1, a marker for detecting cellular hypoxia in the post-mortem tissue, was used to reveal whether vessel occlusion induced hypoxia within the NTS. Following vessel occlusion, blood flow in the dorsal surface of the medulla oblongata including the NTS region showed an approximately 60% decrease and was associated with hypoxia in neurons located predominantly in the caudal part of the NTS as revealed using hypoxyprobe-1. Arterial pressure increased and this response was pronounced significantly in both magnitude and duration when baroreceptor reflex afferents were sectioned. These results suggest that localized hypoxia in the NTS increases arterial pressure. We suggest this represents a protective mechanism whereby the elevated systemic pressure is a compensatory mechanism to enhance cerebral perfusion. Whether this physiological mechanism has any relevance to neurogenic hypertension is discussed.

  13. Automatic retinal blood flow calculation using spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wehbe, Hassan; Ruggeri, Marco; Jiao, Shuliang; Gregori, Giovanni; Puliafito, Carmen A.

    2008-02-01

    Optical Doppler tomography (ODT) is a branch of optical coherence tomography (OCT) that can measure the speed of a blood flow by measuring the Doppler shift impinged on the probing sample light by the moving blood cells. However, the measured speed of blood flow is a function of the Doppler angle, which needs to be determined in order to calculate the absolute velocity of the blood flow inside a vessel. We developed a technique that can extract the Doppler angle from the 3D data measured with spectral-domain OCT, which needs to extract the lateral and depth coordinates of a vessel in each measured ODT and OCT image. The lateral coordinates and the diameter of a blood vessel were first extracted in each OCT structural image by using the technique of blood vessel shadowgram, a technique first developed by us for enhancing the retinal blood vessel contrast in the en face view of the 3D OCT. The depth coordinate of a vessel was then determined by using a circular averaging filter moving in the depth direction along the axis passing through the vessel center in the ODT image. The Doppler angle was then calculated from the extracted coordinates of the blood vessel. The technique was applied in blood flow measurements in retinal blood vessels, which has potential impact on the study and diagnosis of blinding diseases like glaucoma and diabetic retinopathy.

  14. Low cerebral blood flow is a risk factor for severe intraventricular haemorrhage

    PubMed Central

    Meek, J.; Tyszczuk, L.; Elwell, C.; Wyatt, J

    1999-01-01

    AIMS—To investigate the relation between cerebral blood flow on the first day of postnatal life and the severity of any subsequent germinal matrix haemorrhage-intraventricular haemorrhage (GMH-IVH).
METHODS—Cerebral blood flow was measured in 24 babies during the first 24 hours of life using near infrared spectroscopy. Repeated cerebral ultrasound examination was performed to define the maximum extent of GMH-IVH. Infants were classified as: normal scan, minor periventricular haemorrhage (haemorrhage that resolved), or severe GMH-IVH (haemorrhage distending the ventricles, that progressed to either post haemorrhagic dilatation or porencephalic cyst formation).
RESULTS—Cerebral blood flow was significantly lower in the infants with GMH-IVH (median 7.0 ml/100 g/min) than those without haemorrhage (median 12.2 ml/100 g/min), despite no difference in carbon dioxide tension and a higher mean arterial blood pressure. On subgroup analysis, those infants with severe GMH-IVH had the lowest cerebral blood flow.
CONCLUSION—A low cerebral blood flow on the first day of life is associated with the subsequent development of severe intraventricular haemorrhage.

 PMID:10375356

  15. Interferon-λ restricts West Nile virus neuroinvasion by tightening the blood-brain barrier.

    PubMed

    Lazear, Helen M; Daniels, Brian P; Pinto, Amelia K; Huang, Albert C; Vick, Sarah C; Doyle, Sean E; Gale, Michael; Klein, Robyn S; Diamond, Michael S

    2015-04-22

    Although interferon-λ [also known as type III interferon or interleukin-28 (IL-28)/IL-29] restricts infection by several viruses, its inhibitory mechanism has remained uncertain. We used recombinant interferon-λ and mice lacking the interferon-λ receptor (IFNLR1) to evaluate the effect of interferon-λ on infection with West Nile virus, an encephalitic flavivirus. Cell culture studies in mouse keratinocytes and dendritic cells showed no direct antiviral effect of exogenous interferon-λ, even though expression of interferon-stimulated genes was induced. We observed no differences in West Nile virus burden between wild-type and Ifnlr1(-/-) mice in the draining lymph nodes, spleen, or blood. We detected increased West Nile virus infection in the brain and spinal cord of Ifnlr1(-/-) mice, yet this was not associated with a direct antiviral effect in mouse neurons. Instead, we observed an increase in blood-brain barrier permeability in Ifnlr1(-/-) mice. Treatment of mice with pegylated interferon-λ2 resulted in decreased blood-brain barrier permeability, reduced West Nile virus infection in the brain without affecting viremia, and improved survival against lethal virus challenge. An in vitro model of the blood-brain barrier showed that interferon-λ signaling in mouse brain microvascular endothelial cells increased transendothelial electrical resistance, decreased virus movement across the barrier, and modulated tight junction protein localization in a protein synthesis- and signal transducer and activator of transcription 1 (STAT1)-independent manner. Our data establish an indirect antiviral function of interferon-λ in which noncanonical signaling through IFNLR1 tightens the blood-brain barrier and restricts viral neuroinvasion and pathogenesis. Copyright © 2015, American Association for the Advancement of Science.

  16. Relationship between insulin resistance and tissue blood flow in preeclampsia.

    PubMed

    Anim-Nyame, Nick; Gamble, John; Sooranna, Suren R; Johnson, Mark R; Steer, Philip J

    2015-05-01

    Preeclampsia is characterized by generalized endothelial dysfunction and impaired maternal tissue perfusion, and insulin resistance is a prominent feature of this disease. The aim of this study was to test the hypothesis that insulin resistance in preeclampsia is related to the reduced resting tissue blood flow. We used venous occlusion plethysmography to compare the resting calf muscle blood flow (measured as QaU) in 20 nulliparous women with preeclampsia and 20 normal pregnant controls matched for maternal age, gestational age, parity and BMI during the third trimester. Fasting blood samples were obtained to measure the plasma concentrations of insulin and glucose, and to calculate the fasting insulin resistance index (FIRI), a measure of insulin resistance in both groups of women. Calf blood flow was significantly reduced in the preeclampsia group (1.93 ± 0.86 QaU), compared with normal pregnant controls (3.94 ± 1.1 QaU, P < 0.001). Fasting insulin concentrations and Insulin Resistance Index were significantly higher in preeclampsia compared with normal pregnancy (P < 0.001 for both variables). There were significant inverse correlations between resting calf blood flow and fasting insulin concentrations (r = -0.57, P = 0.008) and FIRI (r = -0.59, P = 0.006) in preeclampsia, but not in normal pregnancy. These findings support our hypothesis and raise the possibility that reduced tissue blood flow may a play a role in the increased insulin resistance seen in preeclampsia.

  17. Correlations between ovarian follicular blood flow and superovulatory responses in ewes.

    PubMed

    Oliveira, Maria E F; Feliciano, Marcus A R; D'Amato, Carla C; Oliveira, Luís G; Bicudo, Sony D; Fonseca, Jeferson F; Vicente, Wilter R R; Visco, Elise; Bartlewski, Pawel M

    2014-01-10

    The primary goal of this study was to employ ultrasonography to examine the ovaries of ewes undergoing superovulatory treatment for correlations between antral follicular blood flow and ovarian responses/embryo yields. Five Santa Inês ewes were subjected to a short- (Days 0-6, Group 1) and five to a long-term progesterone-based protocol (Days 0-12, Group 2) to synchronize estrus and ovulations after the superovulatory treatment. Porcine FSH (pFSH, 200mg) was administered in 8 decreasing doses over 4 days, starting on Days 4 and 10 in Groups 1 and 2, respectively. After CIDR removal, all ewes were bred by a ram and embryos were recovered surgically 7 days later. Transrectal ovarian ultrasonography was performed the day before and on all 4 days of the superovulatory treatment. Both an arbitrary-scale [(0) non-detectable; (1) small; (2) moderate; (3) intense blood flow] and quantitative analysis of the blood flow area were used to assess the follicular blood flow in color Doppler images. There were no significant correlations between the arbitrary blood flow scores and superovulatory responses in the ewes of the present study. However, there was a positive correlation between the quantitative estimates of follicular blood flow on the final day of the superovulatory treatment, and the number (DA: r=0.68, P<0.05; DA/TA×100%: r=0.85, P<0.05) and percentage (DA: r=0.65, P<0.05; DA/TA×100%: r=0.91, P<0.001) of unfertilized eggs (DA: Doppler area, TA: total area of the largest ovarian cross section). This experiment presents a commercially practical tool for predicting superovulatory outcomes in ewes and evidence for the existence of follicular blood flow threshold that may impinge negatively on oocyte quality when surpassed during hormonal ovarian superstimulation. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Study of microvascular non-Newtonian blood flow modulated by electroosmosis.

    PubMed

    Tripathi, Dharmendra; Yadav, Ashu; Anwar Bég, O; Kumar, Rakesh

    2018-05-01

    An analytical study of microvascular non-Newtonian blood flow is conducted incorporating the electro-osmosis phenomenon. Blood is considered as a Bingham rheological aqueous ionic solution. An externally applied static axial electrical field is imposed on the system. The Poisson-Boltzmann equation for electrical potential distribution is implemented to accommodate the electrical double layer in the microvascular regime. With long wavelength, lubrication and Debye-Hückel approximations, the boundary value problem is rendered non-dimensional. Analytical solutions are derived for the axial velocity, volumetric flow rate, pressure gradient, volumetric flow rate, averaged volumetric flow rate along one time period, pressure rise along one wavelength and stream function. A plug swidth is featured in the solutions. Via symbolic software (Mathematica), graphical plots are generated for the influence of Bingham plug flow width parameter, electrical Debye length and Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity) on the key hydrodynamic variables. This study reveals that blood flow rate accelerates with decreasing the plug width (i.e. viscoplastic nature of fluids) and also with increasing the Debye length parameter. Copyright © 2018 Elsevier Inc. All rights reserved.

  19. Elevational speciation in action? Restricted gene flow associated with adaptive divergence across an altitudinal gradient

    USGS Publications Warehouse

    Funk, W. C.; Murphy, M.A.; Hoke, K. L.; Muths, Erin L.; Amburgey, Staci M.; Lemmon, Emily M.; Lemmon, A. R.

    2016-01-01

    Evolutionary theory predicts that divergent selection pressures across elevational gradients could cause adaptive divergence and reproductive isolation in the process of ecological speciation. Although there is substantial evidence for adaptive divergence across elevation, there is less evidence that this restricts gene flow. Previous work in the boreal chorus frog (Pseudacris maculata) has demonstrated adaptive divergence in morphological, life history and physiological traits across an elevational gradient from approximately 1500–3000 m in the Colorado Front Range, USA. We tested whether this adaptive divergence is associated with restricted gene flow across elevation – as would be expected if incipient speciation were occurring – and, if so, whether behavioural isolation contributes to reproductive isolation. Our analysis of 12 microsatellite loci in 797 frogs from 53 populations revealed restricted gene flow across elevation, even after controlling for geographic distance and topography. Calls also varied significantly across elevation in dominant frequency, pulse number and pulse duration, which was partly, but not entirely, due to variation in body size and temperature across elevation. However, call variation did not result in strong behavioural isolation: in phonotaxis experiments, low-elevation females tended to prefer an average low-elevation call over a high-elevation call, and vice versa for high-elevation females, but this trend was not statistically significant. In summary, our results show that adaptive divergence across elevation restricts gene flow in P. maculata, but the mechanisms for this potential incipient speciation remain open.

  20. Effects of hypoxia on cochlear blood flow in mice evaluated using Doppler optical microangiography.

    PubMed

    Dziennis, Suzan; Reif, Roberto; Zhi, Zhongwei; Nuttall, Alfred L; Wang, Ruikang K

    2012-10-01

    Reduced cochlear blood flow (CoBF) is a main contributor to hearing loss. Studying CoBF has remained a challenge due to the lack of available tools. Doppler optical microangiography (DOMAG), a method to quantify single-vessel absolute blood flow, and laser Doppler flowmetry (LDF), a method for measuring the relative blood flow within a large volume of tissue, were used for determining the changes in CoBF due to systemic hypoxia in mice. DOMAG determined the change in blood flow in the apical turn (AT) with single-vessel resolution, while LDF averaged the change in the blood flow within a large volume of the cochlea (hemisphere with ∼1 to 1.5 mm radius). Hypoxia was induced by decreasing the concentration of oxygen-inspired gas, so that the oxygen saturation was reduced from >95% to ∼80%. DOMAG determined that during hypoxia the blood flow in two areas of the AT near and far from the helicotrema were increased and decreased, respectively. The LDF detected a decrease in blood flow within a larger volume of the cochlea (several turns averaged together). Therefore, the use of DOMAG as a tool for studying cochlear blood flow due to its ability to determine absolute flow values with single-vessel resolution was proposed.

  1. Effects of hypoxia on cochlear blood flow in mice evaluated using Doppler optical microangiography

    NASA Astrophysics Data System (ADS)

    Dziennis, Suzan; Reif, Roberto; Zhi, Zhongwei; Nuttall, Alfred L.; Wang, Ruikang K.

    2012-10-01

    Reduced cochlear blood flow (CoBF) is a main contributor to hearing loss. Studying CoBF has remained a challenge due to the lack of available tools. Doppler optical microangiography (DOMAG), a method to quantify single-vessel absolute blood flow, and laser Doppler flowmetry (LDF), a method for measuring the relative blood flow within a large volume of tissue, were used for determining the changes in CoBF due to systemic hypoxia in mice. DOMAG determined the change in blood flow in the apical turn (AT) with single-vessel resolution, while LDF averaged the change in the blood flow within a large volume of the cochlea (hemisphere with ˜1 to 1.5 mm radius). Hypoxia was induced by decreasing the concentration of oxygen-inspired gas, so that the oxygen saturation was reduced from >95% to ˜80%. DOMAG determined that during hypoxia the blood flow in two areas of the AT near and far from the helicotrema were increased and decreased, respectively. The LDF detected a decrease in blood flow within a larger volume of the cochlea (several turns averaged together). Therefore, the use of DOMAG as a tool for studying cochlear blood flow due to its ability to determine absolute flow values with single-vessel resolution was proposed.

  2. Cerebral blood flow autoregulation is impaired in schizophrenia: A pilot study.

    PubMed

    Ku, Hsiao-Lun; Wang, Jiunn-Kae; Lee, Hsin-Chien; Lane, Timothy Joseph; Liu, I-Chao; Chen, Yung-Chan; Lee, Yao-Tung; Lin, I-Cheng; Lin, Chia-Pei; Hu, Chaur-Jong; Chi, Nai-Fang

    2017-10-01

    Patients with schizophrenia have a higher risk of cardiovascular diseases and higher mortality from them than does the general population; however, the underlying mechanism remains unclear. Impaired cerebral autoregulation is associated with cerebrovascular diseases and their mortality. Increased or decreased cerebral blood flow in different brain regions has been reported in patients with schizophrenia, which implies impaired cerebral autoregulation. This study investigated the cerebral autoregulation in 21 patients with schizophrenia and 23 age- and sex-matched healthy controls. None of the participants had a history of cardiovascular diseases, hypertension, or diabetes. All participants underwent 10-min blood pressure and cerebral blood flow recording through finger plethysmography and Doppler ultrasonography, respectively. Cerebral autoregulation was assessed by analyzing two autoregulation indices: the mean blood pressure and cerebral blood flow correlation coefficient (Mx), and the phase shift between the waveforms of blood pressure and cerebral blood flow determined using transfer function analysis. Compared with the controls, the patients had a significantly higher Mx (0.257 vs. 0.399, p=0.036) and lower phase shift (44.3° vs. 38.7° in the 0.07-0.20Hz frequency band, p=0.019), which indicated impaired maintenance of constant cerebral blood flow and a delayed cerebrovascular autoregulatory response. Impaired cerebral autoregulation may be caused by schizophrenia and may not be an artifact of coexisting medical conditions. The mechanism underlying impaired cerebral autoregulation in schizophrenia and its probable role in the development of cerebrovascular diseases require further investigation. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Aortic isthmus and cardiac monitoring of the growth-restricted fetus.

    PubMed

    Acharya, Ganesh; Tronnes, Ashlie; Rasanen, Juha

    2011-03-01

    Aortic isthmus acts as an arterial watershed between the cerebral and placental circulations, connecting 2 parallel fetal ventricular pumps. It plays a crucial role in the fetal circulatory dynamics. Information about aortic isthmus blood flow may improve the management of sick fetuses. However, perceived technical difficulties limit the clinical use of aortic isthmus Doppler for fetal hemodynamic monitoring. Changes in aortic isthmus blood flow pattern seem to reflect fetal cardiovascular status accurately and predict perinatal and long-term neurodevelopmental outcome in intrauterine growth restriction. This review evaluates the available scientific information and discusses the role of aortic isthmus in fetal circulation. Copyright © 2011 Elsevier Inc. All rights reserved.

  4. Dynamics of model blood cells in shear flow

    NASA Astrophysics Data System (ADS)

    Podgorski, Thomas; Callens, Natacha; Minetti, Christophe; Coupier, Gwennou; Dubois, Frank; Misbah, Chaouqi

    The dynamics of a vesicle suspension in shear flow was investigated by digital holographic microscopy [1] in parabolic flights and in the MASER 11 sounding rocket. Vesicles are lipid membranes which mimic the mechanical behaviour of cells, such as red blood cells in flow. In a simple shear flow between parallel walls, a lift force of purely viscous origin pushes vesicles away from walls. Our parabolic flight experiments [2] reveal that the lift velocity in a dilute suspen-sion is well described by theoretical predictions by Olla. As vesicles gather near the center of the flow chamber due to lift forces from both walls, one expects hydrodynamic interactions of pairs of vesicles to result in shear induced diffusion in the suspension. The BIOMICS experi-ment in the MASER 11 sounding rocket revealed a complex spatial structure of a polydisperse vesicle suspension due to the interplay between lift forces from the walls and hydrodynamic interactions. These phenomena have a strong impact on the structure and rheology of blood in small vessels, and a precise knowledge of the dynamics of migration and diffusion of soft particles in flow can lead to alternative ways to separate and sort blood cells. 1. Dubois, F., Schockaert, C., Callens, N., Yourrassowsky, C., "Focus plane detection criteria in digital holography microscopy by amplitude analysis", Opt. Express, Vol. 14, pp 5895-5908, 2006 2. Callens, N., Minetti, C., Coupier, G., Mader, M.-A., Dubois, F., Misbah, C., Podgorski, T., "Hydrodynamics lift of vesicles under shear flow in microgravity", Europhys. Lett., Vol. 83, p. 24002, 2008

  5. Effects of pomegranate extract on blood flow and running time to exhaustion.

    PubMed

    Trexler, Eric T; Smith-Ryan, Abbie E; Melvin, Malia N; Roelofs, Erica J; Wingfield, Hailee L

    2014-09-01

    Recent research has shown that dietary nitrate has favorable effects on blood flow and exercise performance. The purpose of this randomized, double-blind, placebo-controlled crossover study was to investigate the acute effects of pomegranate extract on blood flow, vessel diameter, and exercise performance in active individuals. Nineteen men and women (mean ± SD: age, 22.2 ± 2.2 years; height, 174.8 ± 10.7 cm; body mass, 71.9 ± 13.5 kg) were randomly assigned to a placebo (PL) or pomegranate extract (PE) group. Participants performed a maximal oxygen consumption treadmill test to determine peak velocity (PV). Participants returned after 24-48 h and ingested either PL or PE. Brachial artery blood flow was assessed using ultrasound at baseline and 30 min post-ingestion (30minPI). Three treadmill runs to exhaustion were performed at 90%, 100%, and 110% PV. Blood flow was assessed immediately after each exercise bout and 30 min postexercise (30minPEx). After a 7-10 day washout, participants repeated the same procedures, ingesting the opposite supplement. Separate repeated measures ANOVAs were performed for blood flow, vessel diameter, and time to exhaustion (TTE). Blood flow was significantly augmented (p = 0.033) 30minPI with PE in comparison with PL. Vessel diameter was significantly larger (p = 0.036) 30minPEx with PE. Ingestion of PE was found to significantly augment TTE at 90% (p = 0.009) and 100% PV (p = 0.027). Acute ingestion of PE 30 min before exercise may enhance vessel diameter and blood flow and delay fatigue during exercise. Results of the current study indicate that PE is ergogenic for intermittent running, eliciting beneficial effects on blood flow.

  6. Blood Flow in Stenotic Carotid Bifurcation

    NASA Astrophysics Data System (ADS)

    Rayz, Vitaliy L.; Williamson, Shobha Devi; Berger, Stanley A.; Saloner, David

    2004-11-01

    Mechanical forces induced by blood flow on an arterial wall play an important role in the development and growth of atherosclerotic plaque. To assess vulnerability of a plaque it is important to model the flow in a realistic, patient-specific geometry. Three-dimensional models of stenotic carotid bifurcations were obtained from MR images and grids were generated for the flow domains. The unsteady, incompressible Navier-Stokes equations were solved numerically using physiological boundary conditions. The results obtained by computations were compared with in-vivo ultrasound measurements and flow visualization experiments carried out for the same geometry. The simulations show a high velocity jet forming at the stenotic throat and a strong recirculation zone downstream of the stenosis. The jet grows rapidly during the systolic part of the pulse. During diastole the flow is more stagnant. The flow is highly three-dimensional and unsteady which is clearly demonstrated by the flow streamlines. These unsteady flows cause rapid temporal and spatial changes of the forces acting on the atherosclerotic plaque, which has important effects on its growth and stability.

  7. Microvascular Branching as a Determinant of Blood Flow by Intravital Particle Imaging Velocimetry

    NASA Technical Reports Server (NTRS)

    Parsons-Wingerter, Patricia; McKay, Terri L.; Vickerman, Mary B.; Wernet, Mark P.; Myers, Jerry G.; Radhakrishnan, Krishnan

    2007-01-01

    The effects of microvascular branching on blood flow were investigated in vivo by microscopic particle imaging velocimetry (micro-PIV). We use micro-PIV to measure blood flow by tracking red blood cells (RBC) as the moving particles. Velocity flow fields, including flow pulsatility, were analyzed for the first four branching orders of capillaries, postcapillary venules and small veins of the microvascular network within the developing avian yolksac at embryonic day 5 (E5). Increasing volumetric flowrates were obtained from parabolic laminar flow profiles as a function of increasing vessel diameter and branching order. Maximum flow velocities increased approximately twenty-fold as the function of increasing vessel diameter and branching order compared to flow velocities of 100 - 150 micron/sec in the capillaries. Results from our study will be useful for the increased understanding of blood flow within anastomotic, heterogeneous microvascular networks.

  8. In vivo vascular flow profiling combined with optical tweezers based blood routing

    NASA Astrophysics Data System (ADS)

    Meissner, Robert; Sugden, Wade W.; Siekmann, Arndt F.; Denz, Cornelia

    2017-07-01

    In vivo wall shear rate is quantified during zebrafish development using particle image velocimetry for biomedical diagnosis and modeling of artificial vessels. By using brightfield microscopy based high speed video tracking we can resolve single heart-beat cycles of blood flow in both space and time. Maximum blood flow velocities and wall shear rates are presented for zebrafish at two and three days post fertilization. By applying biocompatible optical tweezers as an Optical rail we present rerouting of red blood cells in vivo. With purely light-driven means we are able to compensate the lack of proper red blood cell blood flow in so far unperfused capillaries.

  9. Myocardial Blood Flow Distribution during Ischemia-Induced Coronary Vasodilation in the Unanesthetized Dog

    PubMed Central

    Bache, Robert J.; Cobb, Frederick R.; Greenfield, Joseph C.

    1974-01-01

    This study was designed to determine whether coronary vasodilation distal to a flow-limiting coronary artery stenosis could result in redistribution of myocardial blood flow to produce subendocardial underperfusion. Studies were performed in 10 awake dogs chronically prepared with electromagnetic flow-meters and hydraulic occluders on the left circumflex coronary artery. Regional myocardial blood flow was measured using radionuclide-labeled microspheres, 7-10 μm in diameter, injected into the left atrium. A 5-s coronary artery occlusion was followed by reactive hyperemia with excess inflow of arterial blood effecting 375±20% repayment of the blood flow debt incurred during occlusion. When, after a 5-s occlusion, the occluder was only partially released to hold arterial inflow to the preocclusion level for 20 s before complete release, the delayed reactive hyperemia was augmented (mean blood flow repayment = 610±45%, P < 0.01). This augmentation of the reactive hyperemia suggested that ischemia was continuing during the interval of coronary vasodilation when coronary inflow was at the preocclusion level. Measurements of regional myocardial blood flow demonstrated that endocardial flow slightly exceeded epicardial flow during control conditions. When arterial inflow was limited to the preocclusion rate during vasodilation after a 5-s total coronary artery occlusion, however, flow to the subepicardial myocardium was increased at the expense of underperfusion of the subendocardial myocardium. Thus, in the presence of a flow-limiting proximal coronary artery stenosis, ischemia-induced coronary vasodilation resulted in redistribution of myocardial blood flow with production of subendocardial ischemia in the presence of a net volume of arterial inflow which, if properly distributed, would have been adequate to prevent myocardial ischemia. Images PMID:4279928

  10. Determinants of pulmonary blood flow distribution.

    PubMed

    Glenny, Robb W; Robertson, H Thomas

    2011-01-01

    The primary function of the pulmonary circulation is to deliver blood to the alveolar capillaries to exchange gases. Distributing blood over a vast surface area facilitates gas exchange, yet the pulmonary vascular tree must be constrained to fit within the thoracic cavity. In addition, pressures must remain low within the circulatory system to protect the thin alveolar capillary membranes that allow efficient gas exchange. The pulmonary circulation is engineered for these unique requirements and in turn these special attributes affect the spatial distribution of blood flow. As the largest organ in the body, the physical characteristics of the lung vary regionally, influencing the spatial distribution on large-, moderate-, and small-scale levels. © 2011 American Physiological Society.

  11. In vivo photoacoustic tomography of total blood flow and Doppler angle

    NASA Astrophysics Data System (ADS)

    Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

    2012-02-01

    As two hallmarks of cancer, angiogenesis and hypermetabolism are closely related to increased blood flow. Volumetric blood flow measurement is important to understanding the tumor microenvironment and developing new means to treat cancer. Current photoacoustic blood flow estimation methods focus on either the axial or transverse component of the flow vector. Here, we propose a method to compute the total flow speed and Doppler angle by combining the axial and transverse flow measurements. Both the components are measured in M-mode. Collating the A-lines side by side yields a 2D matrix. The columns are Hilbert transformed to compare the phases for the computation of the axial flow. The rows are Fourier transformed to quantify the bandwidth for the computation of the transverse flow. From the axial and transverse flow components, the total flow speed and Doppler angle can be derived. The method has been verified by flowing bovine blood in a plastic tube at various speeds from 0 to 7.5 mm/s and at Doppler angles from 30 to 330°. The measurement error for total flow speed was experimentally determined to be less than 0.3 mm/s; for the Doppler angle, it was less than 15°. In addition, the method was tested in vivo on a mouse ear. The advantage of this method is simplicity: No system modification or additional data acquisition is required to use our existing system. We believe that the proposed method has the potential to be used for cancer angiogenesis and hypermetabolism imaging.

  12. Analysis of artery blood flow before and after angioplasty

    NASA Astrophysics Data System (ADS)

    Tomaszewski, Michał; Baranowski, Paweł; Małachowski, Jerzy; Damaziak, Krzysztof; Bukała, Jakub

    2018-01-01

    The study presents a comparison of results obtained from numerical simulations of blood flow in two different arteries. One of them was considered to be narrowed in order to simulate an arteriosclerosis obstructing the blood flow in the vessel, whereas the second simulates the vessel after angioplasty treatment. During the treatment, a biodegradable stent is inserted into the artery, which prevents the vessel walls from collapsing. The treatment was simulated through the use of numerical simulation using the finite element method. The final mesh geometry obtained from the analysis was exported to the dedicated software in order to create geometry in which a flow domain inside the artery with the stent was created. The flow analysis was conducted in ANSYS Fluent software with non-deformable vessel walls.

  13. Narcolepsy: regional cerebral blood flow during sleep and wakefulness

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sakai, F.; Meyer, J.S.; Karacan, I.

    Serial measurements of regional cerebral blood flow were made by the 135Xe inhalation method during the early stages of sleep and wakefulness in eight normal volunteers and 12 patients with narcolepsy. Electroencephalogram, electro-oculogram, and submental electromyogram were recorded simultaneously. In normals, mean hemispheric gray matter blood flow (Fg) during stages I and II sleep was significantly less than waking values. Maximum regional blood flow decreases during sleep occurred in the brainstem-cerebellar, right inferior temporal, and bilateral frontal regions. In patients with narcolepsy, mean hemispheric Fg while awake was 80.5 +- 13 ml per 100 gm brain per minute. During REMmore » sleep, mean hemispheric Fg increased concurrently with large increases in brainstem-cerebellar region flow. During stages I and II sleep without REM, there were significant increases in mean hemispheric Fg and brainstem-cerebellar Fg, just the opposite of changes in normals. In narcolepsy, there appears to be a reversal of normal cerebral deactivation patterns, particularly involving the brainstem, during stages I and II sleep.« less

  14. Correlation of carotid blood flow and corrected carotid flow time with invasive cardiac output measurements.

    PubMed

    Ma, Irene W Y; Caplin, Joshua D; Azad, Aftab; Wilson, Christina; Fifer, Michael A; Bagchi, Aranya; Liteplo, Andrew S; Noble, Vicki E

    2017-12-01

    Non-invasive measures that can accurately estimate cardiac output may help identify volume-responsive patients. This study seeks to compare two non-invasive measures (corrected carotid flow time and carotid blood flow) and their correlations with invasive reference measurements of cardiac output. Consenting adult patients (n = 51) at Massachusetts General Hospital cardiac catheterization laboratory undergoing right heart catheterization between February and April 2016 were included. Carotid ultrasound images were obtained concurrently with cardiac output measurements, obtained by the thermodilution method in the absence of severe tricuspid regurgitation and by the Fick oxygen method otherwise. Corrected carotid flow time was calculated as systole time/√cycle time. Carotid blood flow was calculated as π × (carotid diameter) 2 /4 × velocity time integral × heart rate. Measurements were obtained using a single carotid waveform and an average of three carotid waveforms for both measures. Single waveform measurements of corrected flow time did not correlate with cardiac output (ρ = 0.25, 95% CI -0.03 to 0.49, p = 0.08), but an average of three waveforms correlated significantly, although weakly (ρ = 0.29, 95% CI 0.02-0.53, p = 0.046). Carotid blood flow measurements correlated moderately with cardiac output regardless of if single waveform or an average of three waveforms were used: ρ = 0.44, 95% CI 0.18-0.63, p = 0.004, and ρ = 0.41, 95% CI 0.16-0.62, p = 0.004, respectively. Carotid blood flow may be a better marker of cardiac output and less subject to measurements issues than corrected carotid flow time.

  15. Effect of flow rate and temperature on transmembrane blood pressure drop in an extracorporeal artificial lung.

    PubMed

    Park, M; Costa, E L V; Maciel, A T; Barbosa, E V S; Hirota, A S; Schettino, G de P; Azevedo, L C P

    2014-11-01

    Transmembrane pressure drop reflects the resistance of an artificial lung system to blood transit. Decreased resistance (low transmembrane pressure drop) enhances blood flow through the oxygenator, thereby, enhancing gas exchange efficiency. This study is part of a previous one where we observed the behaviour and the modulation of blood pressure drop during the passage of blood through artificial lung membranes. Before and after the induction of multi-organ dysfunction, the animals were instrumented and analysed for venous-venous extracorporeal membrane oxygenation, using a pre-defined sequence of blood flows. Blood flow and revolutions per minute (RPM) of the centrifugal pump varied in a linear fashion. At a blood flow of 5.5 L/min, pre- and post-pump blood pressures reached -120 and 450 mmHg, respectively. Transmembrane pressures showed a significant spread, particularly at blood flows above 2 L/min; over the entire range of blood flow rates, there was a positive association of pressure drop with blood flow (0.005 mmHg/mL/minute of blood flow) and a negative association of pressure drop with temperature (-4.828 mmHg/(°Celsius). These associations were similar when blood flows of below and above 2000 mL/minute were examined. During its passage through the extracorporeal system, blood is exposed to pressure variations from -120 to 450 mmHg. At high blood flows (above 2 L/min), the drop in transmembrane pressure becomes unpredictable and highly variable. Over the entire range of blood flows investigated (0-5500 mL/min), the drop in transmembrane pressure was positively associated with blood flow and negatively associated with body temperature. © The Author(s) 2014.

  16. Evaluation of extracranial blood flow in Parkinson disease.

    PubMed

    Haktanir, Alpay; Yaman, Mehmet; Acar, Murat; Gecici, Omer; Demirel, Reha; Albayrak, Ramazan; Demirkirkan, Kemal

    2006-01-02

    Decreased cerebral flow velocities in Parkinsonian patients were reported previously. Because of the limited data on vascular changes in Parkinson disease (PD), which may have a vascular etiology, we aimed to disclose any possible cerebral hemodynamic alteration in Parkinsonian patients. We prospectively evaluated 28 non-demented, idiopathic parkinsonian patients and 19 age and sex matched controls with Doppler sonography. Flow volumes, peak systolic flow velocities, and cross-sectional areas of vertebral and internal carotid arteries (ICA) were measured and compared between patients and controls. Correlation of patient age and disease duration with Doppler parameters was observed; and each Doppler parameter of patients within each Hoehn-Yahr scale was compared. There was no significant difference of measured parameters between groups. No correlation was found between disease duration and age with flow volume, cross-sectional area or peak systolic velocity. Hoehn-Yahr scale was not found having significant relation with Doppler parameters. Values of vertebral, internal carotid and cerebral blood flow volumes (CBF), peak systolic velocities, and cross-sectional areas were not significantly different between Parkinsonian patients and age and sex matched controls. Although regional blood flow decreases may be seen as reported previously, Parkinson disease is not associated with a flow volume or velocity alteration of extracranial cerebral arteries.

  17. Multiscale Simulation of Blood Flow in Brain Arteries with an Aneurysm

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leopold Grinberg; Vitali Morozov; Dmitry A. Fedosov

    2013-04-24

    Multi-scale modeling of arterial blood flow can shed light on the interaction between events happening at micro- and meso-scales (i.e., adhesion of red blood cells to the arterial wall, clot formation) and at macro-scales (i.e., change in flow patterns due to the clot). Coupled numerical simulations of such multi-scale flow require state-of-the-art computers and algorithms, along with techniques for multi-scale visualizations.This animation presents results of studies used in the development of a multi-scale visualization methodology. First we use streamlines to show the path the flow is taking as it moves through the system, including the aneurysm. Next we investigate themore » process of thrombus (blood clot) formation, which may be responsible for the rupture of aneurysms, by concentrating on the platelet blood cells, observing as they aggregate on the wall of the aneurysm.« less

  18. Regional cerebral blood flow in childhood headache

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roach, E.S.; Stump, D.A.

    1989-06-01

    Regional cerebral blood flow (rCBF) was measured in 16 cranial regions in 23 children and adolescents with frequent headaches using the non-invasive Xenon-133 inhalation technique. Blood flow response to 5% carbon dioxide (CO2) was also determined in 21 patients, while response to 50% oxygen was measured in the two patients with hemoglobinopathy. Included were 10 patients with a clinical diagnosis of migraine, 4 with musculoskeletal headaches, and 3 with features of both types. Also studied were 2 patients with primary thrombocythemia, 2 patients with hemoglobinopathy and headaches, 1 patient with polycythemia, and 1 with headaches following trauma. With two exceptions,more » rCBF determinations were done during an asymptomatic period. Baseline rCBF values tended to be higher in these young patients than in young adults done in our laboratory. Localized reduction in the expected blood flow surge after CO2 inhalation, most often noted posteriorly, was seen in 8 of the 13 vascular headaches, but in none of the musculoskeletal headache group. Both patients with primary thrombocythemia had normal baseline flow values and altered responsiveness to CO2 similar to that seen in migraineurs; thus, the frequently reported headache and transient neurologic signs with primary thrombocythemia are probably not due to microvascular obstruction as previously suggested. These data support the concept of pediatric migraine as a disorder of vasomotor function and also add to our knowledge of normal rCBF values in younger patients. Demonstration of altered vasomotor reactivity to CO2 could prove helpful in children whose headache is atypical.« less

  19. Cerebral blood flow modulations during cognitive control in major depressive disorder.

    PubMed

    Hoffmann, Alexandra; Montoro, Casandra I; Reyes Del Paso, Gustavo A; Duschek, Stefan

    2018-09-01

    This study investigated cerebral blood flow modulations during proactive and reactive cognitive control in major depressive disorder (MDD). Proactive control refers to preparatory processes during anticipation of a behaviorally relevant event; reactive control is activated after such an event to ensure goal attainment. Using functional transcranial Doppler sonography, blood flow velocities in the middle cerebral arteries of both hemispheres were recorded in 40 MDD patients and 40 healthy controls during a precued Stroop task. The font color of color words, which appeared 5 s after an acoustic warning signal, had to be indicated while ignoring word meaning. Patients, as compared to controls, exhibited smaller bilateral blood flow increases during task preparation and larger increases after color word presentation. Response time was longer in patients irrespective of the match or mismatch between font color and word meaning. The blood flow increase after word presentation correlated positively with response time. Potential effects of psychotropic medication on cognition and cerebral blood flow could not be controlled. The study revealed evidence of reduced cortical activity during proactive and elevated activity that occurs during reactive control in MDD. Deficient implementation of proactive control in MDD may lead to increased reliance on reactive control. The association between the blood flow increase after color word presentation and poorer performance indicates that deficient response preparation cannot be compensated for by reactive strategies. The findings are clinically relevant, as they may contribute to our understanding of the mechanisms relevant to cognitive impairments in MDD. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Characterizing pulmonary blood flow distribution measured using arterial spin labeling.

    PubMed

    Henderson, A Cortney; Prisk, G Kim; Levin, David L; Hopkins, Susan R; Buxton, Richard B

    2009-12-01

    The arterial spin labeling (ASL) method provides images in which, ideally, the signal intensity of each image voxel is proportional to the local perfusion. For studies of pulmonary perfusion, the relative dispersion (RD, standard deviation/mean) of the ASL signal across a lung section is used as a reliable measure of flow heterogeneity. However, the RD of the ASL signals within the lung may systematically differ from the true RD of perfusion because the ASL image also includes signals from larger vessels, which can reflect the blood volume rather than blood flow if the vessels are filled with tagged blood during the imaging time. Theoretical studies suggest that the pulmonary vasculature exhibits a lognormal distribution for blood flow and thus an appropriate measure of heterogeneity is the geometric standard deviation (GSD). To test whether the ASL signal exhibits a lognormal distribution for pulmonary blood flow, determine whether larger vessels play an important role in the distribution, and extract physiologically relevant measures of heterogeneity from the ASL signal, we quantified the ASL signal before and after an intervention (head-down tilt) in six subjects. The distribution of ASL signal was better characterized by a lognormal distribution than a normal distribution, reducing the mean squared error by 72% (p < 0.005). Head-down tilt significantly reduced the lognormal scale parameter (p = 0.01) but not the shape parameter or GSD. The RD increased post-tilt and remained significantly elevated (by 17%, p < 0.05). Test case results and mathematical simulations suggest that RD is more sensitive than the GSD to ASL signal from tagged blood in larger vessels, a probable explanation of the change in RD without a statistically significant change in GSD. This suggests that the GSD is a useful measure of pulmonary blood flow heterogeneity with the advantage of being less affected by the ASL signal from tagged blood in larger vessels.

  1. Estimation of Blood Flow Rates in Large Microvascular Networks

    PubMed Central

    Fry, Brendan C.; Lee, Jack; Smith, Nicolas P.; Secomb, Timothy W.

    2012-01-01

    Objective Recent methods for imaging microvascular structures provide geometrical data on networks containing thousands of segments. Prediction of functional properties, such as solute transport, requires information on blood flow rates also, but experimental measurement of many individual flows is difficult. Here, a method is presented for estimating flow rates in a microvascular network based on incomplete information on the flows in the boundary segments that feed and drain the network. Methods With incomplete boundary data, the equations governing blood flow form an underdetermined linear system. An algorithm was developed that uses independent information about the distribution of wall shear stresses and pressures in microvessels to resolve this indeterminacy, by minimizing the deviation of pressures and wall shear stresses from target values. Results The algorithm was tested using previously obtained experimental flow data from four microvascular networks in the rat mesentery. With two or three prescribed boundary conditions, predicted flows showed relatively small errors in most segments and fewer than 10% incorrect flow directions on average. Conclusions The proposed method can be used to estimate flow rates in microvascular networks, based on incomplete boundary data and provides a basis for deducing functional properties of microvessel networks. PMID:22506980

  2. Quadriceps strengthening with and without blood flow restriction in the treatment of patellofemoral pain: a double-blind randomised trial.

    PubMed

    Giles, Lachlan; Webster, Kate E; McClelland, Jodie; Cook, Jill L

    2017-12-01

    Quadriceps strengthening exercises are part of the treatment of patellofemoral pain (PFP), but the heavy resistance exercises may aggravate knee pain. Blood flow restriction (BFR) training may provide a low-load quadriceps strengthening method to treat PFP. Seventy-nine participants were randomly allocated to a standardised quadriceps strengthening (standard) or low-load BFR. Both groups performed 8 weeks of leg press and leg extension, the standard group at 70% of 1 repetition maximum (1RM) and the BFR group at 30% of 1RM. Interventions were compared using repeated-measures analysis of variance for Kujala Patellofemoral Score, Visual Analogue Scale for 'worst pain' and 'pain with daily activity', isometric knee extensor torque (Newton metre) and quadriceps muscle thickness (cm). Subgroup analyses were performed on those participants with painful resisted knee extension at 60°. Sixty-nine participants (87%) completed the study (standard, n=34; BFR, n=35). The BFR group had a 93% greater reduction in pain with activities of daily living (p=0.02) than the standard group. Participants with painful resisted knee extension (n=39) had greater increases in knee extensor torque with BFR than standard (p<0.01). No between-group differences were found for change in Kujala Patellofemoral Score (p=0.31), worst pain (p=0.24), knee extensor torque (p=0.07) or quadriceps thickness (p=0.2). No difference was found between interventions at 6 months. Compared with standard quadriceps strengthening, low load with BFR produced greater reduction in pain with daily living at 8 weeks in people with PFP. Improvements were similar between groups in worst pain and Kujala score. The subgroup with painful resisted knee extension had larger improvements in quadriceps strength from BFR. 12614001164684. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  3. Does a resistance exercise session with continuous or intermittent blood flow restriction promote muscle damage and increase oxidative stress?

    PubMed

    Neto, Gabriel R; Novaes, Jefferson S; Salerno, Verônica P; Gonçalves, Michel M; Batista, Gilmário R; Cirilo-Sousa, Maria S

    2018-01-01

    The aim of this study was to compare the effect of low-load resistance exercise (LLRE) with continuous and intermittent blood flow restriction (BFR) on the creatine kinase (CK), lactate dehydrogenase (LDH), protein carbonyl (PC), thiobarbituric acid-reactive substance (TBARS) and uric acid (UA) levels in military men. The study included 10 recreationally trained men aged 19 ± 0.82 years who underwent the following experimental protocols in random order on separate days (72-96 h): 4 LLRE sessions at a 20% 1RM (one-repetition maximum [1RM]) with continuous BFR (LLRE + CBFR); 4 LLRE sessions at 20% 1RM with intermittent BFR (LLRE + IBFR) and 4 high-intensity resistance exercise (HIRE) sessions at 80% 1RM. The CK and LDH (markers of muscle damage) levels were measured before exercise (BE), 24 h post-exercise and 48 h post-exercise, and the PC, TBARS and UA (markers of oxidative stress) levels were measured BE and immediately after each exercise session. There was a significant increase in CK in the HIRE 24 post-exercise samples compared with the LLRE + CBFR and LLRE + IBFR (P = 0.035, P = 0.036, respectively), as well as between HIRE 48 post-exercise and LLRE + CBFR (P = 0.049). Additionally, there was a significant increase in CK in the LLRE + CBFR samples BE and immediately after each exercise (Δ = 21.9%) and in the HIRE samples BE and immediately after each exercise, BE and 24 post-exercise, and BE and 48 post-exercise (Δ values of 35%, 177.6%, and 177.6%, respectively). However, there were no significant changes in LDH, PC, TBARS, and UA between the protocols (P > 0.05). Therefore, a physical exercise session with continuous or intermittent BFR did not promote muscle damage; moreover, neither protocol seemed to affect the oxidative stress markers.

  4. Relations of Blood Pressure and Head Injury to Regional Cerebral Blood Flow

    PubMed Central

    Allen, Allyssa J.; Katzel, Leslie I.; Wendell, Carrington R.; Siegel, Eliot L.; Lefkowitz, David; Waldstein, Shari R.

    2016-01-01

    Hypertension confers increased risk for cognitive decline, dementia, and cerebrovascular disease. These associations have been attributed, in part, to cerebral hypoperfusion. Here we posit that relations of higher blood pressure to lower levels of cerebral perfusion may be potentiated by a prior head injury. Participants were 87 community-dwelling older adults -69% men, 90% white, mean age= 66.9 years, 27.6% with a history of mild traumatic brain injury (mTBI) defined as a loss of consciousness blood pressure (SBP, DBP) and single photon emission computed tomography (SPECT). Computerized coding of the SPECT images yielded relative ratios of blood flow in left and right cortical and select subcortical regions. Cerebellum served as the denominator. Sex-stratified multiple regression analyses, adjusted for age, education, race, alcohol consumption, smoking status, and depressive symptomatology, revealed significant interactions of blood pressure and head injury to cerebral blood flow in men only. Specifically, among men with a history of head injury, higher systolic blood pressure was associated with lower levels of perfusion in the left orbital (β=-3.21, p=.024) and left dorsolateral (β=-2.61, p=.042) prefrontal cortex, and left temporal cortex (β=-3.36, p=.014); higher diastolic blood pressure was marginally associated with lower levels of perfusion in the left dorsolateral prefrontal cortex (β=-2.79, p=.051). Results indicate that men with a history of head injury may be particularly vulnerable to the impact of higher blood pressure on cerebral perfusion in left anterior cortical regions, thus potentially enhancing risk for adverse brain and neurocognitive outcomes. PMID:27206865

  5. Blood flow-independent accumulation of cisplatin in the guinea pig cochlea.

    PubMed

    Miettinen, S; Laurell, G; Andersson, A; Johansson, R; Laurikainen, E

    1997-01-01

    Considerable interindividual variability in the ototoxic effect of cisplatin has become the unpredictable dose-limiting factor in its use as curative as well as palliative therapy. The drug accumulates in highly vascular areas in the cochlea, causing dose-related hair cell loss. The purpose of this study was to assess blood flow-dependent aspects of cisplatin absorption in the cochlea in order to better understand factors that may influence cisplatin-induced ototoxicity. The effect of reduced cochlear blood flow on the ototoxic action of cisplatin was studied in guinea pigs. Before cisplatin administration the cochlear vasculature in each animal was unilaterally pre-constricted, by the application of 2% epinephrine to the round window. A 20-30% reduction in cochlear blood flow, assessed by laser Doppler flowmetry, was maintained before and after intravenous infusion of 0.1% cisplatin. Cisplatin infusion affected cochlear blood flow but not vessel conductivity. The cochlear blood flow decrease, maintained by local epinephrine application to the round window during cisplatin infusion, did not alter the cisplatin-induced hearing loss. In addition, the concentration of free cisplatin in scala tympani perilymph did not differ between epinephrine-treated and non-treated ears. Our results indicate that cisplatin transport into the cochlea is not an energy-dependent process in the lateral wall vasculature.

  6. [Effect of hemorheology on ultrasonic doppler blood flow spectrum diagram].

    PubMed

    Zhang, Shenghua; Qin, Renjia

    2014-08-01

    The present research aims to point out the long-existing defect of analyzing the spectrum diagram only from the perspective of haemodynamics instead of haemorheology. In the light of the theories of haemodynamics and haemorheology, the causes of spectrum diagram formation of carotid artery blood at the rapid and slow flow can be clarified completely and accurately. Four conclusions have been drawn in the end. As long as the velocity gradient is large enough, obvious red blood cells concentrate to the shaft even in the big or bigger blood vessels; the spectrum diagram is the powerful proof of the two phase flow model of blood; the spectrum diagram can be completely and accurately analyzed only by combining haemodynamics with haemorheology; and only when the red blood cells concentrate to the shaft, the big or bigger blood vessels can be regarded as haemogeneous fluid.

  7. Absolute quantification of regional renal blood flow in swine by dynamic contrast-enhanced magnetic resonance imaging using a blood pool contrast agent.

    PubMed

    Lüdemann, Lutz; Nafz, Benno; Elsner, Franz; Grosse-Siestrup, Christian; Meissler, Michael; Kaufels, Nicola; Rehbein, Hagen; Persson, Pontus B; Michaely, Henrik J; Lengsfeld, Philipp; Voth, Matthias; Gutberlet, Matthias

    2009-03-01

    To evaluate for the first time in an animal model the possibility of absolute regional quantification of renal medullary and cortical perfusion by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a blood pool contrast agent. A total of 18 adult female pigs (age, 16-22 weeks; body weight, 45-65 kg; no dietary restrictions) were investigated by DCE-MRI. Absolute renal blood flow (RBF) measured by an ultrasound transit time flow probe around the renal vein was used as the standard of reference. An inflatable stainless cuff placed around the renal artery near its origin from the abdominal aorta was used to reduce RBF to 60%, 40%, and 20% of the baseline flow. The last measurement was performed with the cuff fully reopened. Absolute RBF values during these 4 perfusion states were compared with the results of DCE-MRI performed on a 1.5-T scanner with an 8-channel phased-array surface coil. All scans were acquired in breath-hold technique in the coronal plane using a field of view of 460 mm.Each dynamic scan commenced with a set of five 3D T1-weighted gradient echo sequences with different flip angles (alpha = 2 degrees, 5 degrees, 10 degrees, 20 degrees, 30 degrees): TE, 0.88 milliseconds; TR, 2.65 milliseconds; slice thickness, 8.8 mm for 4 slices; acquisition matrix, 128 x 128; and acquisitions, 4. These data served to calculate 3D intrinsic longitudinal relaxation rate maps (R10) and magnetization (M0). Immediately after these images, the dynamic 3D T1-weighted gradient echo images were acquired with the same parameters and a constant alpha = 30 degrees, half Fourier, 1 acquisition, 64 frames, a time interval of 1.65 seconds between each frame, and a total duration of 105.6. Three milliliters of an albumin-binding blood pool contrast agent (0.25 mmol/mL gadofosveset trisodium, Vasovist, Bayer Schering Pharma AG, Berlin, Germany) was injected at a rate of 3 mL/s. Perfusion was calculated using the arterial input function from the aorta, which was

  8. Patient-specific coronary artery blood flow simulation using myocardial volume partitioning

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Hwan; Kang, Dongwoo; Kang, Nahyup; Kim, Ji-Yeon; Lee, Hyong-Euk; Kim, James D. K.

    2013-03-01

    Using computational simulation, we can analyze cardiovascular disease in non-invasive and quantitative manners. More specifically, computational modeling and simulation technology has enabled us to analyze functional aspect such as blood flow, as well as anatomical aspect such as stenosis, from medical images without invasive measurements. Note that the simplest ways to perform blood flow simulation is to apply patient-specific coronary anatomy with other average-valued properties; in this case, however, such conditions cannot fully reflect accurate physiological properties of patients. To resolve this limitation, we present a new patient-specific coronary blood flow simulation method by myocardial volume partitioning considering artery/myocardium structural correspondence. We focus on that blood supply is closely related to the mass of each myocardial segment corresponding to the artery. Therefore, we applied this concept for setting-up simulation conditions in the way to consider many patient-specific features as possible from medical image: First, we segmented coronary arteries and myocardium separately from cardiac CT; then the myocardium is partitioned into multiple regions based on coronary vasculature. The myocardial mass and required blood mass for each artery are estimated by converting myocardial volume fraction. Finally, the required blood mass is used as boundary conditions for each artery outlet, with given average aortic blood flow rate and pressure. To show effectiveness of the proposed method, fractional flow reserve (FFR) by simulation using CT image has been compared with invasive FFR measurement of real patient data, and as a result, 77% of accuracy has been obtained.

  9. Micro-scale dynamic simulation of erythrocyte-platelet interaction in blood flow.

    PubMed

    AlMomani, T; Udaykumar, H S; Marshall, J S; Chandran, K B

    2008-06-01

    Platelet activation, adhesion, and aggregation on the blood vessel and implants result in the formation of mural thrombi. Platelet dynamics in blood flow is influenced by the far more numerous erythrocytes (RBCs). This is particularly the case in the smaller blood vessels (arterioles) and in constricted regions of blood flow (such as in valve leakage and hinge regions) where the dimensions of formed elements of blood become comparable with that of the flow geometry. In such regions, models to predict platelet motion, activation, aggregation and adhesion must account for platelet-RBC interactions. This paper studies platelet-RBC interactions in shear flows by performing simulations of micro-scale dynamics using a computational fluid dynamics (CFD) model. A level-set sharp-interface immersed boundary method is employed in the computations in which RBC and platelet boundaries are tracked on a two-dimensional Cartesian grid. The RBCs are assumed to have an elliptical shape and to deform elastically under fluid forces while the platelets are assumed to behave as rigid particles of circular shape. Forces and torques between colliding blood cells are modeled using an extension of the soft-sphere model for elliptical particles. RBCs and platelets are transported under the forces and torques induced by fluid flow and cell-cell and cell-platelet collisions. The simulations show that platelet migration toward the wall is enhanced with increasing hematocrit, in agreement with past experimental observations. This margination is seen to occur due to hydrodynamic forces rather than collisional forces or volumetric exclusion effects. The effect of fluid shear forces on the platelets increases exponentially as a function of hematocrit for the range of parameters covered in this study. The micro-scale analysis can be potentially employed to obtain a deterministic relationship between fluid forces and platelet activation and aggregation in blood flow past cardiovascular implants.

  10. Real-time blood flow visualization using the graphics processing unit

    NASA Astrophysics Data System (ADS)

    Yang, Owen; Cuccia, David; Choi, Bernard

    2011-01-01

    Laser speckle imaging (LSI) is a technique in which coherent light incident on a surface produces a reflected speckle pattern that is related to the underlying movement of optical scatterers, such as red blood cells, indicating blood flow. Image-processing algorithms can be applied to produce speckle flow index (SFI) maps of relative blood flow. We present a novel algorithm that employs the NVIDIA Compute Unified Device Architecture (CUDA) platform to perform laser speckle image processing on the graphics processing unit. Software written in C was integrated with CUDA and integrated into a LabVIEW Virtual Instrument (VI) that is interfaced with a monochrome CCD camera able to acquire high-resolution raw speckle images at nearly 10 fps. With the CUDA code integrated into the LabVIEW VI, the processing and display of SFI images were performed also at ~10 fps. We present three video examples depicting real-time flow imaging during a reactive hyperemia maneuver, with fluid flow through an in vitro phantom, and a demonstration of real-time LSI during laser surgery of a port wine stain birthmark.

  11. Real-time blood flow visualization using the graphics processing unit

    PubMed Central

    Yang, Owen; Cuccia, David; Choi, Bernard

    2011-01-01

    Laser speckle imaging (LSI) is a technique in which coherent light incident on a surface produces a reflected speckle pattern that is related to the underlying movement of optical scatterers, such as red blood cells, indicating blood flow. Image-processing algorithms can be applied to produce speckle flow index (SFI) maps of relative blood flow. We present a novel algorithm that employs the NVIDIA Compute Unified Device Architecture (CUDA) platform to perform laser speckle image processing on the graphics processing unit. Software written in C was integrated with CUDA and integrated into a LabVIEW Virtual Instrument (VI) that is interfaced with a monochrome CCD camera able to acquire high-resolution raw speckle images at nearly 10 fps. With the CUDA code integrated into the LabVIEW VI, the processing and display of SFI images were performed also at ∼10 fps. We present three video examples depicting real-time flow imaging during a reactive hyperemia maneuver, with fluid flow through an in vitro phantom, and a demonstration of real-time LSI during laser surgery of a port wine stain birthmark. PMID:21280915

  12. [Microcirculatory blood and lymph flow examination in eyelid skin by laser Doppler flowmetry].

    PubMed

    Safonova, T N; Kintyukhina, N P; Sidorov, V V; Gladkova, O V; Reyn, E S

    to study normal blood and lymph microcirculation of the upper and lower eyelids in different age groups. The study included 108 volunteers (216 eyes) aged from 20 to 80 years with no signs of changes in anterior segment structures, who were grouped by age ranges (20-30 years, 31-40 years, 41-50 years, 51-60 years, 61-70 years, and 71-80 years) into 6 groups equal in gender and quantitative composition. In all volunteers, microcirculation of the upper and lower eyelids was examined by laser Doppler flowmetry (LDF) ('LASMA MC-1' peripheral blood and lymph flow analyzer and 'LASMA MC' laser diagnostic complex, LASMA LLC). The average perfusion changes in blood and lymph flow as well as blood and lymph flow oscillations were analyzed. Blood and lymph flow in the microvasculature of the upper and lower eyelids is variable and depends on neither the age, nor gender of the test subject. On LDF-gram, every increase in amplitude of blood flow corresponds to a decrease in that of lymph flow. The non-invasive method of LDF expands our diagnostic capabilities as it enables assessment of not only blood, but also lymph flow. The data obtained can serve as a starting point for exploring microcirculation in different age groups in the presence of different pathological processes.

  13. [Regional blood flow and bone uptake of methylene-diphosphonate-technetium-99m].

    PubMed

    Vattimo, A; Martini, G; Pisani, M

    1983-05-30

    Sudeck's atrophy of the foot is an acute, patchy osteoporosis that, on bone scan, shows an increase in both bone blood flow and local bone uptake of bone-seeking radionuclides. The purpose of this study was to evaluate the relationship between bone uptake of 99mTc-MDP and local bone blood flow. In some patients with Sudeck's atrophy of one foot we measured local bone blood flow and bone uptake of 99mTc-MDP. External counting of radioactivity, with a count-rate of 1 second was performed for 60 minutes after i.v. injection of a known dose of 99mTc-MDP in some patients with Sudeck's atrophy of the foot. The regions of interest (ROI) were selected on the basis of a bone scan performed 24 hours earlier. We assumed that the data recorded during the first seconds (7-10) reflect local blood flow and the data at 60 minutes reflect the bone uptake. The ratio between the local blood flow in the involved and healthy foot was higher than the local bone uptake ratio. The ratio between bone uptake and local bone blood flow was higher in the normal foot than in the affected one. These results suggest that the bone avidity for bone-seeking radionuclides is lower in Sudeck's atrophy than in normal bone.

  14. Renal sympathetic nerve, blood flow, and epithelial transport responses to thermal stress.

    PubMed

    Wilson, Thad E

    2017-05-01

    Thermal stress is a profound sympathetic stress in humans; kidney responses involve altered renal sympathetic nerve activity (RSNA), renal blood flow, and renal epithelial transport. During mild cold stress, RSNA spectral power but not total activity is altered, renal blood flow is maintained or decreased, and epithelial transport is altered consistent with a sympathetic stress coupled with central volume loaded state. Hypothermia decreases RSNA, renal blood flow, and epithelial transport. During mild heat stress, RSNA is increased, renal blood flow is decreased, and epithelial transport is increased consistent with a sympathetic stress coupled with a central volume unloaded state. Hyperthermia extends these directional changes, until heat illness results. Because kidney responses are very difficult to study in humans in vivo, this review describes and qualitatively evaluates an in vivo human skin model of sympathetically regulated epithelial tissue compared to that of the nephron. This model utilizes skin responses to thermal stress, involving 1) increased skin sympathetic nerve activity (SSNA), decreased skin blood flow, and suppressed eccrine epithelial transport during cold stress; and 2) increased SSNA, skin blood flow, and eccrine epithelial transport during heat stress. This model appears to mimic aspects of the renal responses. Investigations of skin responses, which parallel certain renal responses, may aid understanding of epithelial-sympathetic nervous system interactions during cold and heat stress. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Predicting bifurcation angle effect on blood flow in the microvasculature.

    PubMed

    Yang, Jiho; Pak, Y Eugene; Lee, Tae-Rin

    2016-11-01

    Since blood viscosity is a basic parameter for understanding hemodynamics in human physiology, great amount of research has been done in order to accurately predict this highly non-Newtonian flow property. However, previous works lacked in consideration of hemodynamic changes induced by heterogeneous vessel networks. In this paper, the effect of bifurcation on hemodynamics in a microvasculature is quantitatively predicted. The flow resistance in a single bifurcation microvessel was calculated by combining a new simple mathematical model with 3-dimensional flow simulation for varying bifurcation angles under physiological flow conditions. Interestingly, the results indicate that flow resistance induced by vessel bifurcation holds a constant value of approximately 0.44 over the whole single bifurcation model below diameter of 60μm regardless of geometric parameters including bifurcation angle. Flow solutions computed from this new model showed substantial decrement in flow velocity relative to other mathematical models, which do not include vessel bifurcation effects, while pressure remained the same. Furthermore, when applying the bifurcation angle effect to the entire microvascular network, the simulation results gave better agreements with recent in vivo experimental measurements. This finding suggests a new paradigm in microvascular blood flow properties, that vessel bifurcation itself, regardless of its angle, holds considerable influence on blood viscosity, and this phenomenon will help to develop new predictive tools in microvascular research. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Arteriovenous oscillations of the redox potential: Is the redox state influencing blood flow?

    PubMed

    Poznanski, Jaroslaw; Szczesny, Pawel; Pawlinski, Bartosz; Mazurek, Tomasz; Zielenkiewicz, Piotr; Gajewski, Zdzislaw; Paczek, Leszek

    2017-09-01

    Studies on the regulation of human blood flow revealed several modes of oscillations with frequencies ranging from 0.005 to 1 Hz. Several mechanisms were proposed that might influence these oscillations, such as the activity of vascular endothelium, the neurogenic activity of vessel wall, the intrinsic activity of vascular smooth muscle, respiration, and heartbeat. These studies relied typically on non-invasive techniques, for example, laser Doppler flowmetry. Oscillations of biochemical markers were rarely coupled to blood flow. The redox potential difference between the artery and the vein was measured by platinum electrodes placed in the parallel homonymous femoral artery and the femoral vein of ventilated anesthetized pigs. Continuous measurement at 5 Hz sampling rate using a digital nanovoltmeter revealed fluctuating signals with three basic modes of oscillations: ∼ 1, ∼ 0.1 and ∼ 0.01 Hz. These signals clearly overlap with reported modes of oscillations in blood flow, suggesting coupling of the redox potential and blood flow. The amplitude of the oscillations associated with heart action was significantly smaller than for the other two modes, despite the fact that heart action has the greatest influence on blood flow. This finding suggests that redox potential in blood might be not a derivative but either a mediator or an effector of the blood flow control system.

  17. Cell-cell interaction in blood flow in patients with coronary heart disease (in vitro study)

    NASA Astrophysics Data System (ADS)

    Malinova, Lidia I.; Simonenko, Georgy V.; Denisova, Tatyana P.; Tuchin, Valery V.

    2007-02-01

    Blood cell-cell and cell-vessel wall interactions are one of the key patterns in blood and vascular pathophysiology. We have chosen the method of reconstruction of pulsative blood flow in vitro in the experimental set. Blood flow structure was studied by PC integrated video camera with following slide by slide analysis. Studied flow was of constant volumetric blood flow velocity (1 ml/h). Diameter of tube in use was comparable with coronary arteries diameter. Glucose solution and unfractured heparin were used as the nonspecial irritants of studied flow. Erythrocytes space structure in flow differs in all groups of patients in our study (men with stable angina pectoris (SAP), myocardial infarction (MI) and practically healthy men (PHM). Intensity of erythrocytes aggregate formation was maximal in patients with SAP, but time of their "construction/deconstruction" at glucose injection was minimal. Phenomena of primary clotting formation in patients with SAP of high function class was reconstructed under experimental conditions. Heparin injection (10 000 ED) increased linear blood flow velocity both in patients with SAP, MI and PHP but modulated the cell profile in the flow. Received data correspond with results of animal model studies and noninvasive blood flow studies in human. Results of our study reveal differences in blood flow structure in patients with coronary heart disease and PHP under irritating conditions as the possible framework of metabolic model of coronary blood flow destabilization.

  18. Effect of pyrrolidone-pyroglutamic acid composition on blood flow in rat middle cerebral artery.

    PubMed

    Semkina, G A; Matsievskii, D D; Mirzoyan, N R

    2006-01-01

    We compared the effects of a pyrrolidone-pyroglutamic acid composition and nimodipine on blood circulation in the middle cerebral artery in rats. The composition produced a strong effect on blood supply to the brain, stimulated blood flow in the middle cerebral artery (by 60 +/- 9%) and decreased blood pressure (by 25.0 +/- 2.7%). The cerebrovascular effects of this composition differed from those of nimodipine. Nimodipine not only increased middle cerebral artery blood flow, but also decreased cerebral blood flow in the early period after treatment.

  19. Ocular Blood Flow Measured Noninvasively in Zero Gravity

    NASA Technical Reports Server (NTRS)

    Ansari, Rafat R.; Manuel, Francis K.; Geiser, Martial; Moret, Fabrice; Messer, Russell K.; King, James F.; Suh, Kwang I.

    2003-01-01

    In spaceflight or a reduced-gravity environment, bodily fluids shift to the upper extremities of the body. The pressure inside the eye, or intraocular pressure, changes significantly. A significant number of astronauts report changes in visual acuity during orbital flight. To date this remains of unknown etiology. Could choroidal engorgement be the primary mechanism and a change in the curvature or shape of the cornea or lens be the secondary mechanism for this change in visual acuity? Perfused blood flow in the dense meshwork of capillaries of the choroidal tissue (see the preceding illustration) provides necessary nutrients to the outer layers of the retina (photoreceptors) to keep it healthy and maintain good vision. Unlike the vascular system, the choroid has no baroreceptors to autoregulate fluid shifts, so it can remain engorged, pushing the macula forward and causing a hyperopic (farsighted) shift of the eye. Experiments by researchers at the NASA Glenn Research Center could help answer this question and facilitate planning for long-duration missions. We are investigating the effects of zero gravity on the choroidal blood flow of volunteer subjects. This pilot project plans to determine if choroidal blood flow is autoregulated in a reduced-gravity environment.

  20. Changes in scalp and cortical blood flow during hyperventilation measured with diffusing-wave spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Jun; Ninck, Markus; Gisler, Thomas

    2009-07-01

    Changes in scalp and cortical blood flow induced by voluntary hyperventilation are investigated by near-infrared diffusing-wave spectroscopy. The temporal intensity autocorrelation function g(2) (τ) of multiply scattered light is recorded from the forehead of subjects during hyperventilation. Blood flow within the sampled tissue volume is estimated by the mean decay rate of g(2) (τ) . Data measured from six subjects show that the pattern of the hemodynamic response during 50 s hyperventilation is rather complicated: within the first 10 s, in three subjects an initial increase in blood flow is observed; from 10 s to 20 s, the mean blood flow is smaller than its baseline value for all six subjects; for the duration from 20 s to 30 s, the blood flow increases again. However, after 30 s the change is not consistent across subjects. Further study on one of these subjects by using two receivers probing the blood flow in the cortex and in the superficial layers simultaneously, reveals that during hyperventilation, the direction of change in blood flow within the scalp is opposite to the one in the brain. This helps to understand the complicated hemodynamic response observed in our measurements.

  1. En route Spacing Tool: Efficient Conflict-free Spacing to Flow-Restricted Airspace

    NASA Technical Reports Server (NTRS)

    Green, S.

    1999-01-01

    This paper describes the Air Traffic Management (ATM) problem within the U.S. of flow-restricted en route airspace, an assessment of its impact on airspace users, and a set of near-term tools and procedures to resolve the problem. The FAA is committed, over the next few years, to deploy the first generation of modem ATM decision support tool (DST) technology under the Free-Flight Phase-1 (FFp1) program. The associated en route tools include the User Request Evaluation Tool (URET) and the Traffic Management Advisor (TMA). URET is an initial conflict probe (ICP) capability that assists controllers with the detection and resolution of conflicts in en route airspace. TMA orchestrates arrivals transitioning into high-density terminal airspace by providing controllers with scheduled times of arrival (STA) and delay feedback advisories to assist with STA conformance. However, these FFPl capabilities do not mitigate the en route Miles-In-Trail (MIT) restrictions that are dynamically applied to mitigate airspace congestion. National statistics indicate that en route facilities (Centers) apply Miles-In-Trail (MIT) restrictions for approximately 5000 hours per month. Based on results from this study, an estimated 45,000 flights are impacted by these restrictions each month. Current-day practices for implementing these restrictions result in additional controller workload and an economic impact of which the fuel penalty alone may approach several hundred dollars per flight. To mitigate much of the impact of these restrictions on users and controller workload, a DST and procedures are presented. The DST is based on a simple derivative of FFP1 technology that is designed to introduce a set of simple tools for flow-rate (spacing) conformance and integrate them with conflict-probe capabilities. The tool and associated algorithms are described based on a concept prototype implemented within the CTAS baseline in 1995. A traffic scenario is used to illustrate the controller's use of

  2. Relationship between parietal blood flow studies in the left colon and the rectum in dogs. Colonic pressure and blood flow.

    PubMed

    Arhan, P; Bouchoucha, M; Martelli, H; Rimbert, J N; Berdeaux, A; Gallix, P; Héro, M; Barritault, L; Pellerin, D; Devroede, G

    1988-01-01

    An animal model was proposed to clarify the difference in occurrence of enterocolitis in congenital aganglionosis. When gaseous distention of the colon was localized to the rectosigmoid area, enterocolitis never occurred. On the contrary, when it involved the left colon, enterocolitis occurred in 13 of 15 patients. Intestinal blood flow rates were simultaneously measured in the left colon and rectum of six dogs by using labeled microspheres and expressed in function of the intraluminal pressure. Results show that for elevated values of intraluminal pressure, blood flow was significantly lower in the left colon than in the rectum. These results may explain why ischemia and necrosis occurred more frequently in the left colon than in the rectum.

  3. Cardiorespiratory effects of inelastic chest wall restriction.

    PubMed

    Miller, Jordan D; Beck, Kenneth C; Joyner, Michael J; Brice, A Glenn; Johnson, Bruce D

    2002-06-01

    We examined the effects of chest wall restriction (CWR) on cardiorespiratory function at rest and during exercise in healthy subjects in an attempt to approximate the cardiorespiratory interactions observed in clinical conditions that result in restrictive lung and/or chest wall changes and a reduced intrathoracic space. Canvas straps were applied around the thorax and abdomen so that vital capacity was reduced by >35%. Data were acquired at rest and during cycle ergometry at 25 and 45% of peak workloads. CWR elicited significant increases in the flow-resistive work performed on the lung (160%) and the gastric pressure-time integral (>400%) at the higher workload, but it resulted in a decrease in the elastic work performed on the lung (56%) compared with control conditions. With CWR, heart rate increased and stroke volume (SV) fell, resulting in >10% fall in cardiac output at rest and during exercise at matched workloads (P < 0.05). Blood pressure and catecholamines were significantly elevated during CWR exercise conditions (P < 0.05). We conclude that CWR significantly impairs SV during exercise and that a compensatory increase in heart rate does not prevent a significant reduction in cardiac output. O(2) consumption appears to be maintained via increased extraction and a redistribution of blood flow via sympathetic activation.

  4. Decreased poststenotic flow disturbance during drag reduction by polyacrylamide infusion without increased aortic blood flow.

    PubMed

    Hutchison, K J; Campbell, J D; Karpinski, E

    1989-07-01

    The infusion of polyacrylamide in open chest rats has been reported to increase aortic blood flow and the effect has been ascribed to the "drag reduction" properties of these compounds. In six anesthetized dogs the infusion of polyacrylamide to a total dose of 2 mg/kg caused a reduction in midline and separation zone Doppler spectral broadening in the common carotid artery poststenotic velocity field. This apparent reduction in poststenotic turbulence was interpreted as indicating the presence of a drag reducing effect. Despite this demonstration that polyacrylamide was present in the blood in drag reducing concentrations no increase in aortic blood flow was produced.

  5. Flow rate calibration to determine cell-derived microparticles and homogeneity of blood components.

    PubMed

    Noulsri, Egarit; Lerdwana, Surada; Kittisares, Kulvara; Palasuwan, Attakorn; Palasuwan, Duangdao

    2017-08-01

    Cell-derived microparticles (MPs) are currently of great interest to screening transfusion donors and blood components. However, the current approach to counting MPs is not affordable for routine laboratory use due to its high cost. The current study aimed to investigate the potential use of flow-rate calibration for counting MPs in whole blood, packed red blood cells (PRBCs), and platelet concentrates (PCs). The accuracy of flow-rate calibration was investigated by comparing the platelet counts of an automated counter and a flow-rate calibrator. The concentration of MPs and their origins in whole blood (n=100), PRBCs (n=100), and PCs (n=92) were determined using a FACSCalibur. The MPs' fold-changes were calculated to assess the homogeneity of the blood components. Comparing the platelet counts conducted by automated counting and flow-rate calibration showed an r 2 of 0.6 (y=0.69x+97,620). The CVs of the within-run and between-run variations of flow-rate calibration were 8.2% and 12.1%, respectively. The Bland-Altman plot showed a mean bias of -31,142platelets/μl. MP enumeration revealed both the difference in MP levels and their origins in whole blood, PRBCs, and PCs. Screening the blood components demonstrated high heterogeneity of the MP levels in PCs when compared to whole blood and PRBCs. The results of the present study suggest the accuracy and precision of flow-rate calibration for enumerating MPs. This flow-rate approach is affordable for assessing the homogeneity of MPs in blood components in routine laboratory practice. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Influence of type of aortic valve prosthesis on coronary blood flow velocity.

    PubMed

    Jelenc, Matija; Juvan, Katja Ažman; Medvešček, Nadja Tatjana Ružič; Geršak, Borut

    2013-02-01

    Severe aortic valve stenosis is associated with high resting and reduced hyperemic coronary blood flow. Coronary blood flow increases after aortic valve replacement (AVR); however, the increase depends on the type of prosthesis used. The present study investigates the influence of type of aortic valve prosthesis on coronary blood flow velocity. The blood flow velocity in the left anterior descending coronary artery (LAD) and the right coronary artery (RCA) was measured intraoperatively before and after AVR with a stentless bioprosthesis (Sorin Freedom Solo; n = 11) or a bileaflet mechanical prosthesis (St. Jude Medical Regent; n = 11). Measurements were made with an X-Plore epicardial Doppler probe (Medistim, Oslo, Norway) following induction of hyperemia with an adenosine infusion. Preoperative and postoperative echocardiography evaluations were used to assess valvular and ventricular function. Velocity time integrals (VTI) were measured from the Doppler signals and used to calculate the proportion of systolic VTI (SF), diastolic VTI (DF), and normalized systolic coronary blood flow velocities (NSF) and normalized diastolic coronary blood flow velocities (NDF). The systolic proportion of the LAD VTI increased after AVR with the St. Jude Medical Regent prosthesis, which produced higher LAD SF and NSF values than the Sorin Freedom Solo prosthesis (SF, 0.41 ± 0.09 versus 0.29 ± 0.13 [P = .04]; NSF, 0.88 ± 0.24 versus 0.55 ± 0.17 [P = .01]). No significant changes in the LAD velocity profile were noted after valve replacement with the Sorin Freedom Solo, despite a significant reduction in transvalvular gradient and an increase in the effective orifice area. AVR had no effect on the RCA flow velocity profile. The coronary flow velocity profile in the LAD was significantly influenced by the type of aortic valve prosthesis used. The differences in the LAD velocity profile probably reflect differences in valve design and the systolic transvalvular flow pattern.

  7. [A capillary blood flow velocity detection system based on linear array charge-coupled devices].

    PubMed

    Zhou, Houming; Wang, Ruofeng; Dang, Qi; Yang, Li; Wang, Xiang

    2017-12-01

    In order to detect the flow characteristics of blood samples in the capillary, this paper introduces a blood flow velocity measurement system based on field-programmable gate array (FPGA), linear charge-coupled devices (CCD) and personal computer (PC) software structure. Based on the analysis of the TCD1703C and AD9826 device data sheets, Verilog HDL hardware description language was used to design and simulate the driver. Image signal acquisition and the extraction of the real-time edge information of the blood sample were carried out synchronously in the FPGA. Then a series of discrete displacement were performed in a differential operation to scan each of the blood samples displacement, so that the sample flow rate could be obtained. Finally, the feasibility of the blood flow velocity detection system was verified by simulation and debugging. After drawing the flow velocity curve and analyzing the velocity characteristics, the significance of measuring blood flow velocity is analyzed. The results show that the measurement of the system is less time-consuming and less complex than other flow rate monitoring schemes.

  8. Blood pool and tissue phase patient motion effects on 82rubidium PET myocardial blood flow quantification.

    PubMed

    Lee, Benjamin C; Moody, Jonathan B; Poitrasson-Rivière, Alexis; Melvin, Amanda C; Weinberg, Richard L; Corbett, James R; Ficaro, Edward P; Murthy, Venkatesh L

    2018-03-23

    Patient motion can lead to misalignment of left ventricular volumes of interest and subsequently inaccurate quantification of myocardial blood flow (MBF) and flow reserve (MFR) from dynamic PET myocardial perfusion images. We aimed to identify the prevalence of patient motion in both blood and tissue phases and analyze the effects of this motion on MBF and MFR estimates. We selected 225 consecutive patients that underwent dynamic stress/rest rubidium-82 chloride ( 82 Rb) PET imaging. Dynamic image series were iteratively reconstructed with 5- to 10-second frame durations over the first 2 minutes for the blood phase and 10 to 80 seconds for the tissue phase. Motion shifts were assessed by 3 physician readers from the dynamic series and analyzed for frequency, magnitude, time, and direction of motion. The effects of this motion isolated in time, direction, and magnitude on global and regional MBF and MFR estimates were evaluated. Flow estimates derived from the motion corrected images were used as the error references. Mild to moderate motion (5-15 mm) was most prominent in the blood phase in 63% and 44% of the stress and rest studies, respectively. This motion was observed with frequencies of 75% in the septal and inferior directions for stress and 44% in the septal direction for rest. Images with blood phase isolated motion had mean global MBF and MFR errors of 2%-5%. Isolating blood phase motion in the inferior direction resulted in mean MBF and MFR errors of 29%-44% in the RCA territory. Flow errors due to tissue phase isolated motion were within 1%. Patient motion was most prevalent in the blood phase and MBF and MFR errors increased most substantially with motion in the inferior direction. Motion correction focused on these motions is needed to reduce MBF and MFR errors.

  9. Resistance exercise with different volumes: blood pressure response and forearm blood flow in the hypertensive elderly

    PubMed Central

    Brito, Aline de Freitas; de Oliveira, Caio Victor Coutinho; Brasileiro-Santos, Maria do Socorro; Santos, Amilton da Cruz

    2014-01-01

    Background The purpose of this study was to evaluate the effect of two sessions of resistance exercise with different volumes on post-exercise hypotension, forearm blood flow, and forearm vascular resistance in hypertensive elderly subjects. Methods The study was conducted with ten hypertensive elderly (65±3 years, 28.7±3 kg/m2) subjected to three experimental sessions, ie, a control session, exercise with a set (S1), and exercise with three sets (S3). For each session, the subjects were evaluated before and after intervention. In the pre-intervention period, blood pressure, forearm blood flow, and forearm vascular resistance were measured after 10 minutes of rest in the supine position. Thereafter, the subjects were taken to the gym to perform their exercise sessions or remained at rest during the same time period. Both S1 and S3 comprised a set of ten repetitions of ten exercises, with an interval of 90 seconds between exercises. Subsequently, the measurements were again performed at 10, 30, 50, 70, and 90 minutes of recovery (post-intervention) in the supine position. Results Post-exercise hypotension was greater in S3 than in S1 (systolic blood pressure, −26.5±4.2 mmHg versus −17.9±4.7 mmHg; diastolic blood pressure, −13.8±4.9 mmHg versus −7.7±5 mmHg, P<0.05). Similarly, forearm blood flow and forearm vascular resistance changed significantly in both sessions with an increase and decrease, respectively, that was more evident in S3 than in S1 (P<0.05). Conclusion Resistance exercises with higher volume were more effective in causing post-exercise hypotension, being accompanied by an increase in forearm blood flow and a reduction of forearm vascular resistance. PMID:25540580

  10. Automated Blood Pressure Measurement

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The Vital-2 unit pictured is a semi-automatic device that permits highly accurate blood pressure measurement, even by untrained personnel. Developed by Meditron Instrument Corporation, Milford, New Hampshire, it is based in part on NASA technology found in a similar system designed for automatic monitoring of astronauts' blood pressure. Vital-2 is an advancement over the familiar arm cuff, dial and bulb apparatus customarily used for blood pressure checks. In that method, the physician squeezes the bulb to inflate the arm cuff, which restricts the flow of blood through the arteries. As he eases the pressure on the arm, he listens, through a stethoscope, to the sounds of resumed blood flow as the arteries expand and contract. Taking dial readings related to sound changes, he gets the systolic (contracting) and diastolic (expanding) blood pressure measurements. The accuracy of the method depends on the physician's skill in interpreting the sounds. Hospitals sometimes employ a more accurate procedure, but it is "invasive," involving insertion of a catheter in the artery.

  11. Fast blood flow monitoring in deep tissues with real-time software correlators

    PubMed Central

    Wang, Detian; Parthasarathy, Ashwin B.; Baker, Wesley B.; Gannon, Kimberly; Kavuri, Venki; Ko, Tiffany; Schenkel, Steven; Li, Zhe; Li, Zeren; Mullen, Michael T.; Detre, John A.; Yodh, Arjun G.

    2016-01-01

    We introduce, validate and demonstrate a new software correlator for high-speed measurement of blood flow in deep tissues based on diffuse correlation spectroscopy (DCS). The software correlator scheme employs standard PC-based data acquisition boards to measure temporal intensity autocorrelation functions continuously at 50 – 100 Hz, the fastest blood flow measurements reported with DCS to date. The data streams, obtained in vivo for typical source-detector separations of 2.5 cm, easily resolve pulsatile heart-beat fluctuations in blood flow which were previously considered to be noise. We employ the device to separate tissue blood flow from tissue absorption/scattering dynamics and thereby show that the origin of the pulsatile DCS signal is primarily flow, and we monitor cerebral autoregulation dynamics in healthy volunteers more accurately than with traditional instrumentation as a result of increased data acquisition rates. Finally, we characterize measurement signal-to-noise ratio and identify count rate and averaging parameters needed for optimal performance. PMID:27231588

  12. A reconstruction method of intra-ventricular blood flow using color flow ultrasound: a simulation study

    NASA Astrophysics Data System (ADS)

    Jang, Jaeseong; Ahn, Chi Young; Jeon, Kiwan; Choi, Jung-il; Lee, Changhoon; Seo, Jin Keun

    2015-03-01

    A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color Doppler echocardiography measurement. From 3D incompressible Navier- Stokes equation, a 2D incompressible Navier-Stokes equation with a mass source term is derived to utilize the measurable color flow ultrasound data in a plane along with the moving boundary condition. The proposed model reflects out-of-plane blood flows on the imaging plane through the mass source term. For demonstrating a feasibility of the proposed method, we have performed numerical simulations of the forward problem and numerical analysis of the reconstruction method. First, we construct a 3D moving LV region having a specific stroke volume. To obtain synthetic intra-ventricular flows, we performed a numerical simulation of the forward problem of Navier-Stokes equation inside the 3D moving LV, computed 3D intra-ventricular velocity fields as a solution of the forward problem, projected the 3D velocity fields on the imaging plane and took the inner product of the 2D velocity fields on the imaging plane and scanline directional velocity fields for synthetic scanline directional projected velocity at each position. The proposed method utilized the 2D synthetic projected velocity data for reconstructing LV blood flow. By computing the difference between synthetic flow and reconstructed flow fields, we obtained the averaged point-wise errors of 0.06 m/s and 0.02 m/s for u- and v-components, respectively.

  13. Retinal blood flow detection in diabetic patients by Doppler Fourier domain optical coherence tomography◊

    PubMed Central

    Wang, Yimin; Fawzi, Amani; Tan, Ou; Gil-Flamer, John; Huang, David

    2010-01-01

    We present human retinal blood flow investigation for diabetic patients using Doppler Fourier domain optical coherence tomography (FD-OCT). The scanning pattern consisted of two concentric circles around the optic nerve head. The blood flow in one patient with diabetes and no retinpathy and another patient with treated proliferative diabetic retinopathy were measured. The patient without retinopathy showed a total blood flow value at the lower level of the normal range. The flow distribution between superior and inferior retina was balanced. The patient with diabetic retinopathy had a flow value lower than the normal people. Our study shows that Doppler FD-OCT can be used to evaluate the total retinal blood flow in patients with retinal diseases. PMID:19259246

  14. Simulations of blood flow through a stenosed carotid artery

    NASA Astrophysics Data System (ADS)

    Lundin, Staffan; Meder, Samuel; Metcalfe, Ralph

    2000-11-01

    The human carotid artery is often the site of the formation of atherosclerotic lesions that can lead to severe reduction of blood flow to the brain, frequently resulting in a stroke. There is strong evidence that hemodynamic variables such as the wall shear stress and its spatial and temporal derivatives play a role in fostering atherosclerosis. To investigate the potential of these effects, we have performed unsteady, three-dimensional numerical simulations of blood flow through the carotid bifurcation in the presence of stenoses of varying degrees and eccentricities. The simulations indicate that regions of low maximum and minimum shear stress correlate better with lesion prone sites than low average wall shear stress. As the degree of stenosis increases, it is found that the downstream flow changes drastically for stenoses greater than about 25Downstream eddies are generated during systole that create local shear stress peaks on the internal carotid artery wall, resulting in significant reduction in flow rates through the internal carotid artery. Large secondary flows develop, and there are also periods of flow reversal during the systolic/diastolic cycle.

  15. Nutrition Coupled with High-Load Traditional or Low-Load Blood Flow Restricted Exercise During Human Limb Suspension

    NASA Technical Reports Server (NTRS)

    Hackney, K. J.; Everett, M.; Ploutz-Snyder, L. L.

    2011-01-01

    High-load resistance exercise (HRE) and low-load blood flow restricted (BFR) exercise have demonstrated efficacy for attenuating unloading related muscle atrophy and dysfunction. In recreational exercisers, protein consumption immediately before and/or after exercise has been shown to increase the skeletal muscle anabolic response to resistance training. PURPOSE: To compare the skeletal muscle adaptations when chocolate milk intake was coupled with HRE or low-load BFR exercise [3 d/wk] during simulated lower limb weightlessness. METHODS: Eleven subjects were counterbalanced [based on age and gender] to HRE (31 +/- 14 yr, 170 +/- 13 cm, 71 +/- 18 kg, 2M/3W) or low-load BFR exercise (31 +/- 12 yr, 169 +/- 13 cm, 66 +/- 14 kg, 2M/4W) during 30 days of unilateral lower limb suspension (ULLS). Both HRE and BFR completed 3 sets of single leg press and calf raise exercise during ULLS. BFR exercise intensity was 20% of repetition maximum (1RM) with a cuff inflation pressure of 1.3 systolic blood pressure (143 4 mmHg). Cuff pressure was maintained during all 3 sets including rest intervals (90s). HRE intensity was 75% 1RM and was performed without cuff inflation. Immediately (<10 min) before and after exercise 8 fl oz of chocolate milk (150 kcal, 2.5g total fat, 22g total carbohydrate, 8g protein) was consumed to optimize acute exercise responses in favor of muscle anabolism. ULLS analog compliance was assessed from leg skin temperature recordings and plantar accelerometry. Muscle cross-sectional area (CSA) for knee extensor and plantar flexor muscle groups were determined from analysis of magnetic resonance images using ImageJ software. 1RM strength for leg press and calf raise was assessed on the Agaton exercise system. Muscular endurance during leg press and calf raise was evaluated from the maximal number of repetitions performed to volitional fatigue using 40% of pre-ULLS 1RM. RESULTS: Steps detected by plantar acceleometry declined by 98.9% during ULLS relative to an

  16. Artificial blood-flow controlling effects of inhomogeneity of twisted magnetic fields

    NASA Astrophysics Data System (ADS)

    Nakagawa, Hidenori; Ohuchi, Mikio

    2017-06-01

    We developed a blood-flow controlling system using magnetic therapy for some types of nervous diseases. In our research, we utilized overlapped extremely low frequency (ELF) fields for the most effective blood-flow for the system. Results showed the possibility that the inhomogeneous region obtained by overlapping the fields at 50 Hz, namely, a desirably twisted field revealed a significant difference in induced electromotive forces at the insertion points of electrodes. In addition, ELF exposures with a high inhomogeneity of the twisted field at 50 Hz out of phase were more effective in generating an induced electromotive difference by approximately 31%, as contrasted with the difference generated by the exposure in phase. We expect that the increase of the inhomogeneity of the twisted field around a blood vessel can produce the most effective electromotive difference in the blood, and also moderately affect the excitable cells relating to the autonomic nervous system for an outstanding blood-flow control in vivo.

  17. An in vitro test bench reproducing coronary blood flow signals.

    PubMed

    Chodzyński, Kamil Jerzy; Boudjeltia, Karim Zouaoui; Lalmand, Jacques; Aminian, Adel; Vanhamme, Luc; de Sousa, Daniel Ribeiro; Gremmo, Simone; Bricteux, Laurent; Renotte, Christine; Courbebaisse, Guy; Coussement, Grégory

    2015-08-07

    It is a known fact that blood flow pattern and more specifically the pulsatile time variation of shear stress on the vascular wall play a key role in atherogenesis. The paper presents the conception, the building and the control of a new in vitro test bench that mimics the pulsatile flows behavior based on in vivo measurements. An in vitro cardiovascular simulator is alimented with in vivo constraints upstream and provided with further post-processing analysis downstream in order to mimic the pulsatile in vivo blood flow quantities. This real-time controlled system is designed to perform real pulsatile in vivo blood flow signals to study endothelial cells' behavior under near physiological environment. The system is based on an internal model controller and a proportional-integral controller that controls a linear motor with customized piston pump, two proportional-integral controllers that control the mean flow rate and temperature of the medium. This configuration enables to mimic any resulting blood flow rate patterns between 40 and 700 ml/min. In order to feed the system with reliable periodic flow quantities in vivo measurements were performed. Data from five patients (1 female, 4 males; ages 44-63) were filtered and post-processed using the Newtonian Womersley's solution. These resulting flow signals were compared with 2D axisymmetric, numerical simulation using a Carreau non-Newtonian model to validate the approximation of a Newtonian behavior. This in vitro test bench reproduces the measured flow rate time evolution and the complexity of in vivo hemodynamic signals within the accuracy of the relative error below 5%. This post-processing method is compatible with any real complex in vivo signal and demonstrates the heterogeneity of pulsatile patterns in coronary arteries among of different patients. The comparison between analytical and numerical solution demonstrate the fair quality of the Newtonian Womersley's approximation. Therefore, Womersley's solution

  18. The effect of blood cell count on coronary flow in patients with coronary slow flow phenomenon.

    PubMed

    Soylu, Korhan; Gulel, Okan; Yucel, Huriye; Yuksel, Serkan; Aksan, Gokhan; Soylu, Ayşegül İdil; Demircan, Sabri; Yılmaz, Ozcan; Sahin, Mahmut

    2014-09-01

    The coronary slow flow phenomenon (CSFP) is a coronary artery disease with a benign course, but its pathological mechanisms are not yet fully understood.The purpose of this controlled study was to investigate the cellular content of blood in patients diagnosed with CSFP and the relationship of this with coronary flow rates. Selective coronary angiographies of 3368 patients were analyzed to assess Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) values. Seventy eight of them had CSFP, and their demographic and laboratory findings were compared with 61 patients with normal coronary flow. Patients' demographic characteristics were similar in both groups. Mean corrected TFC (cTFC) values were significantly elevated in CSFP patients (p<0.001). Furthermore, hematocrit and hemoglobin values, and eosinophil and basophil counts of the CSFP patients were significantly elevated compared to the values obtained in the control group (p=0.005, p=0.047, p=0.001 and p=0.002, respectively). The increase observed in hematocrit and eosinophil levels showed significant correlations with increased TFC values (r=0.288 and r=0.217, respectively). Significant changes have been observed in the cellular composition of blood in patients diagnosed with CSFP as compared to the patients with normal coronary blood flow. The increases in hematocrit levels and in the eosinophil and basophil counts may have direct or indirect effects on the rate of coronary blood flow.

  19. Nonlinear assessment of cerebral autoregulation from spontaneous blood pressure and cerebral blood flow fluctuations.

    PubMed

    Hu, Kun; Peng, C K; Czosnyka, Marek; Zhao, Peng; Novak, Vera

    2008-03-01

    Cerebral autoregulation (CA) is an most important mechanism responsible for the relatively constant blood flow supply to brain when cerebral perfusion pressure varies. Its assessment in nonacute cases has been relied on the quantification of the relationship between noninvasive beat-to-beat blood pressure (BP) and blood flow velocity (BFV). To overcome the nonstationary nature of physiological signals such as BP and BFV, a computational method called multimodal pressure-flow (MMPF) analysis was recently developed to study the nonlinear BP-BFV relationship during the Valsalva maneuver (VM). The present study aimed to determine (i) whether this method can estimate autoregulation from spontaneous BP and BFV fluctuations during baseline rest conditions; (ii) whether there is any difference between the MMPF measures of autoregulation based on intra-arterial BP (ABP) and based on cerebral perfusion pressure (CPP); and (iii) whether the MMPF method provides reproducible and reliable measure for noninvasive assessment of autoregulation. To achieve these aims, we analyzed data from existing databases including: (i) ABP and BFV of 12 healthy control, 10 hypertensive, and 10 stroke subjects during baseline resting conditions and during the Valsalva maneuver, and (ii) ABP, CPP, and BFV of 30 patients with traumatic brain injury (TBI) who were being paralyzed, sedated, and ventilated. We showed that autoregulation in healthy control subjects can be characterized by specific phase shifts between BP and BFV oscillations during the Valsalva maneuver, and the BP-BFV phase shifts were reduced in hypertensive and stroke subjects (P < 0.01), indicating impaired autoregulation. Similar results were found during baseline condition from spontaneous BP and BFV oscillations. The BP-BFV phase shifts obtained during baseline and during VM were highly correlated (R > 0.8, P < 0.0001), showing no statistical difference (paired-t test P > 0.47). In TBI patients there were strong correlations

  20. Nonlinear Assessment of Cerebral Autoregulation from Spontaneous Blood Pressure and Cerebral Blood Flow Fluctuations

    PubMed Central

    Peng, C. K.; Czosnyka, Marek; Zhao, Peng

    2009-01-01

    Cerebral autoregulation (CA) is an most important mechanism responsible for the relatively constant blood flow supply to brain when cerebral perfusion pressure varies. Its assessment in nonacute cases has been relied on the quantification of the relationship between noninvasive beat-to-beat blood pressure (BP) and blood flow velocity (BFV). To overcome the nonstationary nature of physiological signals such as BP and BFV, a computational method called multimodal pressure-flow (MMPF) analysis was recently developed to study the nonlinear BP–BFV relationship during the Valsalva maneuver (VM). The present study aimed to determine (i) whether this method can estimate autoregulation from spontaneous BP and BFV fluctuations during baseline rest conditions; (ii) whether there is any difference between the MMPF measures of autoregulation based on intra-arterial BP (ABP) and based on cerebral perfusion pressure (CPP); and (iii) whether the MMPF method provides reproducible and reliable measure for noninvasive assessment of autoregulation. To achieve these aims, we analyzed data from existing databases including: (i) ABP and BFV of 12 healthy control, 10 hypertensive, and 10 stroke subjects during baseline resting conditions and during the Valsalva maneuver, and (ii) ABP, CPP, and BFV of 30 patients with traumatic brain injury (TBI) who were being paralyzed, sedated, and ventilated. We showed that autoregulation in healthy control subjects can be characterized by specific phase shifts between BP and BFV oscillations during the Valsalva maneuver, and the BP–BFV phase shifts were reduced in hypertensive and stroke subjects (P < 0.01), indicating impaired autoregulation. Similar results were found during baseline condition from spontaneous BP and BFV oscillations. The BP–BFV phase shifts obtained during baseline and during VM were highly correlated (R > 0.8, P < 0.0001), showing no statistical difference (paired-t test P > 0.47). In TBI patients there were strong

  1. Gastric emptying, postprandial blood pressure, glycaemia and splanchnic flow in Parkinson's disease.

    PubMed

    Trahair, Laurence G; Kimber, Thomas E; Flabouris, Katerina; Horowitz, Michael; Jones, Karen L

    2016-05-28

    To determine gastric emptying, blood pressure, mesenteric artery blood flow, and blood glucose responses to oral glucose in Parkinson's disease. Twenty-one subjects (13 M, 8 F; age 64.2 ± 1.6 years) with mild to moderate Parkinson's disease (Hoehn and Yahr score 1.4 ± 0.1, duration of known disease 6.3 ± 0.9 years) consumed a 75 g glucose drink, labelled with 20 MBq (99m)Tc-calcium phytate. Gastric emptying was quantified with scintigraphy, blood pressure and heart rate with an automated device, superior mesenteric artery blood flow by Doppler ultrasonography and blood glucose by glucometer for 180 min. Autonomic nerve function was evaluated with cardiovascular reflex tests and upper gastrointestinal symptoms by questionnaire. The mean gastric half-emptying time was 106 ± 9.1 min, gastric emptying was abnormally delayed in 3 subjects (14%). Systolic and diastolic blood pressure fell (P < 0.001) and mesenteric blood flow and blood glucose (P < 0.001 for both) increased, following the drink. Three subjects (14%) had definite autonomic neuropathy and 8 (38%) had postprandial hypotension. There were no significant relationships between changes in blood pressure, heart rate or mesenteric artery blood flow with gastric emptying. Gastric emptying was related to the score for autonomic nerve function (R = 0.55, P < 0.01). There was an inverse relationship between the blood glucose at t = 30 min (R = -0.52, P < 0.05), while the blood glucose at t = 180 min was related directly (R = 0.49, P < 0.05), with gastric emptying. In mild to moderate Parkinson's disease, gastric emptying is related to autonomic dysfunction and a determinant of the glycaemic response to oral glucose.

  2. Volumetric blood flow via time-domain correlation: experimental verification.

    PubMed

    Embree, P M; O'Brien, W R

    1990-01-01

    A novel ultrasonic volumetric flow measurement method using time-domain correlation of consecutive pairs of echoes has been developed. An ultrasonic data acquisition system determined the time shift between a pair of range gated echoes by searching for the time shift with the maximum correlation between the RF sampled waveforms. Experiments with a 5-MHz transducer indicate that the standard deviation of the estimate of steady fluid velocity through 6-mm-diameter tubes is less than 10% of the mean. Experimentally, Sephadex (G-50; 20-80 mum dia.) particles in water and fresh porcine blood have been used as ultrasound scattering fluids. Two-dimensional (2-D) flow velocity can be estimated by slowly sweeping the ultrasonic beam across the blood vessel phantom. Volumetric flow through the vessel is estimated by integrating the 2-D flow velocity field and then is compared to hydrodynamic flow measurements to assess the overall experimental accuracy of the time-domain method. Flow rates from 50-500 ml/min have been estimated with an accuracy better than 10% under the idealized characteristics used in this study, which include straight circular thin-walled tubes, laminar axially-symmetric steady flow, and no intervening tissues.

  3. Blood warming, pump heating and haemolysis in low-flow extracorporeal life support; an in vitro study using freshly donated human blood.

    PubMed

    Kusters, R W J; Simons, A P; Lancé, M D; Ganushchak, Y M; Bekers, O; Weerwind, P W

    2017-01-01

    Low-flow extracorporeal life support can be used for cardiopulmonary support of paediatric and neonatal patients and is also emerging as a therapy for patients suffering from exacerbation of chronic obstructive pulmonary disease. However, pump heating and haemolysis have proven to negatively affect the system and outcome. This in vitro study aimed at gaining insight into blood warming, pump heating and haemolysis related to the performance of a new low-flow centrifugal pump. Pump performance in the 400-1,500 ml/min flow range was modulated using small-sized dual-lumen catheters and freshly donated human blood. Measurements included plasma free haemoglobin, blood temperature, pump speed, pump pressure, blood flow and thermographic imaging. Blood warming (ΔT max =0.5°C) had no relationship with pump performance or haemolysis (R 2 max =0.05). Pump performance-related parameters revealed no relevant relationships with haemolysis (R 2 max =0.36). Thermography showed no relevant heat zones in the pump (T max =36°C). Concerning blood warming, pump heating and haemolysis, we deem the centrifugal pump applicable for low-flow extracorporeal circulation.

  4. Lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels

    NASA Astrophysics Data System (ADS)

    Fang, Haiping; Wang, Zuowei; Lin, Zhifang; Liu, Muren

    2002-05-01

    A lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels is presented by introducing a boundary condition for elastic and moving boundaries. The mass conservation for the boundary condition is tested in detail. The viscous flow in elastic vessels is simulated with a pressure-radius relationship similar to that of the pulmonary blood vessels. The numerical results for steady flow agree with the analytical prediction to very high accuracy, and the simulation results for pulsatile flow are comparable with those of the aortic flows observed experimentally. The model is expected to find many applications for studying blood flows in large distensible arteries, especially in those suffering from atherosclerosis, stenosis, aneurysm, etc.

  5. Modelling Cerebral Blood Flow and Temperature Using a Vascular Porous Model

    NASA Astrophysics Data System (ADS)

    Blowers, Stephen; Thrippleton, Michael; Marshall, Ian; Harris, Bridget; Andrews, Peter; Valluri, Prashant

    2016-11-01

    Macro-modelling of cerebral blood flow can assist in determining the impact of temperature intervention to reduce permanent tissue damage during instances of brain trauma. Here we present a 3D two phase fluid-porous model for simulating blood flow through the capillary region linked to intersecting 1D arterial and venous vessel trees. This combined vasculature porous (VaPor) model simulates both flow and energy balances, including heat from metabolism, using a vasculature extracted from MRI data which are expanded upon using a tree generation algorithm. Validation of temperature balance has been achieved using rodent brain data. Direct flow validation is not as straight forward due to the method used in determining regional cerebral blood flow (rCBF). In-vivo measurements are achieved using a tracer, which disagree with direct measurements of simulated flow. However, by modelling a virtual tracer, rCBF values are obtained that agree with those found in literature. Temperature profiles generated with the VaPor model show a reduction in core brain temperature after cooling the scalp not seen previously in other models.

  6. Role of NO in choroidal blood flow regulation during isometric exercise in healthy humans.

    PubMed

    Luksch, Alexandra; Polska, Elzbieta; Imhof, Andrea; Schering, Joanne; Fuchsjäger-Mayrl, Gabriele; Wolzt, Michael; Schmetterer, Leopold

    2003-02-01

    Nitric oxide (NO) is an important regulator of basal choroidal blood flow. Animal experiments indicate that NO is also involved in choroidal blood flow regulation during changes in ocular perfusion pressure and inhibition of NO synthase (NOS) has been reported to shift choroidal pressure-flow curves to the right. The hypothesis for the study was that inhibition of NOS may influence choroidal blood flow during isometric exercise. To test this hypothesis, a randomized, double-masked, placebo-controlled, three-way crossover study was performed in 12 healthy male volunteers. Subjects received on different study days intravenous infusions of N(G)-monomethyl-L-arginine (L-NMMA), phenylephrine, or placebo. During these infusion periods, subjects were asked to squat for 6 minutes. Choroidal blood flow was assessed with laser Doppler flowmetry, and ocular perfusion pressure (OPP) was calculated from mean arterial pressure and intraocular pressure. L-NMMA and phenylephrine increased resting OPP by 10% and 13%, respectively, but only L-NMMA reduced resting choroidal blood flow (-17%, P < 0.001). The relative increase in OPP during isometric exercise was comparable with all drugs administered. Isometric exercise increased choroidal blood flow during administration of placebo and phenylephrine, but not during administration of L-NMMA (P < 0.001 vs. placebo). These data indicate that NO plays an important role in the regulation of choroidal blood flow during isometric exercise.

  7. Computational Biorheology of Human Blood Flow in Health and Disease

    PubMed Central

    Fedosov, Dmitry A.; Dao, Ming; Karniadakis, George Em; Suresh, Subra

    2014-01-01

    Hematologic disorders arising from infectious diseases, hereditary factors and environmental influences can lead to, and can be influenced by, significant changes in the shape, mechanical and physical properties of red blood cells (RBCs), and the biorheology of blood flow. Hence, modeling of hematologic disorders should take into account the multiphase nature of blood flow, especially in arterioles and capillaries. We present here an overview of a general computational framework based on dissipative particle dynamics (DPD) which has broad applicability in cell biophysics with implications for diagnostics, therapeutics and drug efficacy assessments for a wide variety of human diseases. This computational approach, validated by independent experimental results, is capable of modeling the biorheology of whole blood and its individual components during blood flow so as to investigate cell mechanistic processes in health and disease. DPD is a Lagrangian method that can be derived from systematic coarse-graining of molecular dynamics but can scale efficiently up to arterioles and can also be used to model RBCs down to the spectrin level. We start from experimental measurements of a single RBC to extract the relevant biophysical parameters, using single-cell measurements involving such methods as optical tweezers, atomic force microscopy and micropipette aspiration, and cell-population experiments involving microfluidic devices. We then use these validated RBC models to predict the biorheological behavior of whole blood in healthy or pathological states, and compare the simulations with experimental results involving apparent viscosity and other relevant parameters. While the approach discussed here is sufficiently general to address a broad spectrum of hematologic disorders including certain types of cancer, this paper specifically deals with results obtained using this computational framework for blood flow in malaria and sickle cell anemia. PMID:24419829

  8. Lattice Boltzmann Simulation of Blood Flow in Blood Vessels with the Rolling Massage

    NASA Astrophysics Data System (ADS)

    Yi, Hou-Hui; Xu, Shi-Xiong; Qian, Yue-Hong; Fang, Hai-Ping

    2005-12-01

    The rolling massage manipulation is a classic Chinese massage, which is expected to improve the circulation by pushing, pulling and kneading of the muscle. A model for the rolling massage manipulation is proposed and the lattice Boltzmann method is applied to study the blood flow in the blood vessels. The simulation results show that the blood flux is considerably modified by the rolling massage and the explicit value depends on the rolling frequency, the rolling depth, and the diameter of the vessel. The smaller the diameter of the blood vessel, the larger the enhancement of the blood flux by the rolling massage. The model, together with the simulation results, is expected to be helpful to understand the mechanism and further development of rolling massage techniques.

  9. Pulsatile spiral blood flow through arterial stenosis.

    PubMed

    Linge, Fabian; Hye, Md Abdul; Paul, Manosh C

    2014-11-01

    Pulsatile spiral blood flow in a modelled three-dimensional arterial stenosis, with a 75% cross-sectional area reduction, is investigated by using numerical fluid dynamics. Two-equation k-ω model is used for the simulation of the transitional flow with Reynolds numbers 500 and 1000. It is found that the spiral component increases the static pressure in the vessel during the deceleration phase of the flow pulse. In addition, the spiral component reduces the turbulence intensity and wall shear stress found in the post-stenosis region of the vessel in the early stages of the flow pulse. Hence, the findings agree with the results of Stonebridge et al. (2004). In addition, the results of the effects of a spiral component on time-varying flow are presented and discussed along with the relevant pathological issues.

  10. Acute low-intensity cycling with blood-flow restriction has no effect on metabolic signaling in human skeletal muscle compared to traditional exercise.

    PubMed

    Smiles, William J; Conceição, Miguel S; Telles, Guilherme D; Chacon-Mikahil, Mara P T; Cavaglieri, Cláudia R; Vechin, Felipe C; Libardi, Cleiton A; Hawley, John A; Camera, Donny M

    2017-02-01

    Autophagy is an intracellular degradative system sensitive to hypoxia and exercise-induced perturbations to cellular bioenergetics. We determined the effects of low-intensity endurance-based exercise performed with blood-flow restriction (BFR) on cell signaling adaptive responses regulating autophagy and substrate metabolism in human skeletal muscle. In a randomized cross-over design, nine young, healthy but physically inactive males completed three experimental trials separated by 1 week of recovery consisting of either a resistance exercise bout (REX: 4 × 10 leg press repetitions, 70% 1-RM), endurance exercise (END: 30 min cycling, 70% VO 2peak ), or low-intensity cycling with BFR (15 min, 40% VO 2peak ). A resting muscle biopsy was obtained from the vastus lateralis 2 weeks prior to the first exercise trial and 3 h after each exercise bout. END increased ULK1 Ser757 phosphorylation above rest and BFR (~37 to 51%, P < 0.05). Following REX, there were significant elevations compared to rest (~348%) and BFR (~973%) for p38γ MAPK Thr180/Tyr182 phosphorylation (P < 0.05). Parkin content was lower following BFR cycling compared to REX (~20%, P < 0.05). There were no exercise-induced changes in select markers of autophagy following BFR. Genes implicated in substrate metabolism (HK2 and PDK4) were increased above rest (~143 to 338%) and BFR cycling (~212 to 517%) with END (P < 0.001). A single bout of low-intensity cycling with BFR is insufficient to induce intracellular "stress" responses (e.g., high rates of substrate turnover and local hypoxia) necessary to activate skeletal muscle autophagy signaling.

  11. The feasibility of measuring renal blood flow using transesophageal echocardiography in patients undergoing cardiac surgery.

    PubMed

    Yang, Ping-Liang; Wong, David T; Dai, Shuang-Bo; Song, Hai-Bo; Ye, Ling; Liu, Jin; Liu, Bin

    2009-05-01

    There is no reliable method to monitor renal blood flow intraoperatively. In this study, we evaluated the feasibility and reproducibility of left renal blood flow measurements using transesophageal echocardiography during cardiac surgery. In this prospective noninterventional study, left renal blood flow was measured with transesophageal echocardiography during three time points (pre-, intra-, and postcardiopulmonary bypass) in 60 patients undergoing cardiac surgery. Sonograms from 6 subjects were interpreted by 2 blinded independent assessors at the time of acquisition and 6 mo later. Interobserver and intraobserver reproducibility were quantified by calculating variability and intraclass correlation coefficients. Patients with Doppler angles of >30 degrees (20 of 60 subjects) were eliminated from renal blood flow measurements. Left renal blood flow was successfully measured and analyzed in 36 of 60 (60%) subjects. Both interobserver and intraobserver variability were <10%. Interobserver and intraobserver reproducibility in left renal blood flow measurements were good to excellent (intraclass correlation coefficients 0.604-0.999). Left renal arterial luminal diameter for the pre, intra, and postcardiopulmonary bypass phases, ranged from 3.8 to 4.1 mm, renal arterial velocity from 25 to 35 cm/s, and left renal blood flow from 192 to 299 mL/min. In patients undergoing cardiac surgery, it was feasible in 60% of the subjects to measure left renal blood flow using intraoperative transesophageal echocardiography. The interobserver and intraobserver reproducibility of renal blood flow measurements was good to excellent.

  12. Relation of retinal blood flow and retinal oxygen extraction during stimulation with diffuse luminance flicker

    PubMed Central

    Palkovits, Stefan; Lasta, Michael; Told, Reinhard; Schmidl, Doreen; Werkmeister, René; Cherecheanu, Alina Popa; Garhöfer, Gerhard; Schmetterer, Leopold

    2015-01-01

    Cerebral and retinal blood flow are dependent on local neuronal activity. Several studies quantified the increase in cerebral blood flow and oxygen consumption during activity. In the present study we investigated the relation between changes in retinal blood flow and oxygen extraction during stimulation with diffuse luminance flicker and the influence of breathing gas mixtures with different fractions of O2 (FiO2; 100% 15% and 12%). Twenty-four healthy subjects were included. Retinal blood flow was studied by combining measurement of vessel diameters using the Dynamic Vessel Analyser with measurements of blood velocity using laser Doppler velocimetry. Oxygen saturation was measured using spectroscopic reflectometry and oxygen extraction was calculated. Flicker stimulation increased retinal blood flow (57.7 ± 17.8%) and oxygen extraction (34.6 ± 24.1%; p < 0.001 each). During 100% oxygen breathing the response of retinal blood flow and oxygen extraction was increased (p < 0.01 each). By contrast, breathing gas mixtures with 12% and 15% FiO2 did not alter flicker–induced retinal haemodynamic changes. The present study indicates that at a comparable increase in blood flow the increase in oxygen extraction in the retina is larger than in the brain. During systemic hyperoxia the blood flow and oxygen extraction responses to neural stimulation are augmented. The underlying mechanism is unknown. PMID:26672758

  13. Intraocular Pressure, Blood Pressure, and Retinal Blood Flow Autoregulation: A Mathematical Model to Clarify Their Relationship and Clinical Relevance

    PubMed Central

    Guidoboni, Giovanna; Harris, Alon; Cassani, Simone; Arciero, Julia; Siesky, Brent; Amireskandari, Annahita; Tobe, Leslie; Egan, Patrick; Januleviciene, Ingrida; Park, Joshua

    2014-01-01

    Purpose. This study investigates the relationship between intraocular pressure (IOP) and retinal hemodynamics and predicts how arterial blood pressure (BP) and blood flow autoregulation (AR) influence this relationship. Methods. A mathematical model is developed to simulate blood flow in the central retinal vessels and retinal microvasculature as current flowing through a network of resistances and capacitances. Variable resistances describe active and passive diameter changes due to AR and IOP. The model is validated by using clinically measured values of retinal blood flow and velocity. The model simulations for six theoretical patients with high, normal, and low BP (HBP-, NBP-, LBP-) and functional or absent AR (-wAR, -woAR) are compared with clinical data. Results. The model predicts that NBPwAR and HBPwAR patients can regulate retinal blood flow (RBF) as IOP varies between 15 and 23 mm Hg and between 23 and 29 mm Hg, respectively, whereas LBPwAR patients do not adequately regulate blood flow if IOP is 15 mm Hg or higher. Hemodynamic alterations would be noticeable only if IOP changes occur outside of the regulating range, which, most importantly, depend on BP. The model predictions are consistent with clinical data for IOP reduction via surgery and medications and for cases of induced IOP elevation. Conclusions. The theoretical model results suggest that the ability of IOP to induce noticeable changes in retinal hemodynamics depends on the levels of BP and AR of the individual. These predictions might help to explain the inconsistencies found in the clinical literature concerning the relationship between IOP and retinal hemodynamics. PMID:24876284

  14. Pulsatile Flow and Gas Transport of Blood over an Array of Cylinders

    NASA Astrophysics Data System (ADS)

    Chan, Kit Yan

    2005-11-01

    In the artificial lung, blood passes through an array of micro-fibers and the gas transfer is strongly dependent on the flow field. The blood flow is unsteady and pulsatile. We have numerically simulated pulsatile flow and gas transfer of blood (modeled as a Casson fluid) over arrays of cylindrical micro-fibers. Oxygen and carbon dioxide are assumed to be in local equilibrium with hemoglobin in blood; and the carbon dioxide facilitated oxygen transport is incorporated into the model by allowing the coupling of carbon dioxide partial pressure and oxygen saturation. The pulsatile flow inputs considered are the sinusoidal and the cardiac waveforms. The squared and staggered arrays of arrangement of the cylinders are considered in this study. Gas transport can be enhanced by: increasing the oscillation frequency; increasing the Reynolds number; increasing the oscillation amplitude; decreasing the void fraction; the use of the cardiac pulsatile input. The overall gas transport is greatly enhanced by the presence of hemoglobin in blood even though the non-Newtonian effect of blood tends to decrease the size and strength of vortices. The pressure drop is also presented as it is an important design parameter confronting the heart.

  15. Relationship of 133Xe cerebral blood flow to middle cerebral arterial flow velocity in men at rest

    NASA Technical Reports Server (NTRS)

    Clark, J. M.; Skolnick, B. E.; Gelfand, R.; Farber, R. E.; Stierheim, M.; Stevens, W. C.; Beck, G. Jr; Lambertsen, C. J.

    1996-01-01

    Cerebral blood flow (CBF) was measured by 133Xe clearance simultaneously with the velocity of blood flow through the left middle cerebral artery (MCA) over a wide range of arterial PCO2 in eight normal men. Average arterial PCO2, which was varied by giving 4% and 6% CO2 in O2 and by controlled hyperventilation on O2, ranged from 25.3 to 49.9 mm Hg. Corresponding average values of global CBF15 were 27.2 and 65.0 ml 100 g min-1, respectively, whereas MCA blood-flow velocity ranged from 42.8 to 94.2 cm/s. The relationship of CBF to MCA blood-flow velocity over the imposed range of arterial PCO2 was described analytically by a parabola with the equation: CBF = 22.8 - 0.17 x velocity + 0.006 x velocity2 The observed data indicate that MCA blood-flow velocity is a useful index of CBF response to change in arterial PCO2 during O2 breathing at rest. With respect to baseline values measured while breathing 100% O2 spontaneously, percent changes in velocity were significantly smaller than corresponding percent changes in CBF at increased levels of arterial PCO2 and larger than CBF changes at the lower arterial PCO2. These observed relative changes are consistent with MCA vasodilation at the site of measurement during exposure to progressive hypercapnia and also during extreme hyperventilation hypocapnia.

  16. Circadian changes in uterine artery and ovarian stromal blood flow after pituitary down-regulation.

    PubMed

    Chan, Carina C W; Ng, Ernest H Y; Tang, Oi-Shan; Ho, Pak-Chung

    2005-09-01

    To investigate changes in the uterine artery and ovarian stromal blood flow in relation to the time of the day after pituitary down-regulation during in vitro fertilization treatment. Thirteen women were recruited. The uterine artery blood flow was studied using pulsed color Doppler ultrasonography and the ovarian stromal blood flow was measured using three-dimensional power Doppler ultrasonography. Ultrasound scan examinations and blood pressure measurements were performed in the morning and evening. The diastolic and the mean arterial pressures were significantly higher in the evening. An increase in the uterine artery pulsatility index and resistance index in the evening was observed. The ovarian vascularization index, vascularization flow index, and right ovarian flow index were significantly lower in the evening. Despite the small sample size, we have demonstrated the presence of a diurnal change in uterine artery and ovarian stromal blood flow after pituitary down-regulation. Such changes may be related to the systemic change in the sympathetic system and hence vascular resistance. Future study regarding ovarian stromal blood flow should take into account the effect of the time of the day on the readings in order to avoid misleading interpretation of data.

  17. Review: Neuroinflammation in intrauterine growth restriction.

    PubMed

    Wixey, Julie A; Chand, Kirat K; Colditz, Paul B; Bjorkman, S Tracey

    2017-06-01

    Disruption to the maternal environment during pregnancy from events such as hypoxia, stress, toxins, inflammation, and reduced placental blood flow can affect fetal development. Intrauterine growth restriction (IUGR) is commonly caused by chronic placental insufficiency, interrupting supply of oxygen and nutrients to the fetus resulting in abnormal fetal growth. IUGR is a major cause of perinatal morbidity and mortality, occurring in approximately 5-10% of pregnancies. The fetal brain is particularly vulnerable in IUGR and there is an increased risk of long-term neurological disorders including cerebral palsy, epilepsy, learning difficulties, behavioural difficulties and psychiatric diagnoses. Few studies have focused on how growth restriction interferes with normal brain development in the IUGR neonate but recent studies in growth restricted animal models demonstrate increased neuroinflammation. This review describes the role of neuroinflammation in the progression of brain injury in growth restricted neonates. Identifying the mediators responsible for alterations in brain development in the IUGR infant is key to prevention and treatment of brain injury in these infants. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Planning-free cerebral blood flow territory mapping in patients with intracranial arterial stenosis

    PubMed Central

    Arteaga, Daniel F; Strother, Megan K; Davis, L Taylor; Fusco, Matthew R; Faraco, Carlos C; Roach, Brent A; Scott, Allison O

    2016-01-01

    A noninvasive method for quantifying cerebral blood flow and simultaneously visualizing cerebral blood flow territories is vessel-encoded pseudocontinuous arterial spin labeling MRI. However, obstacles to acquiring such information include limited access to the methodology in clinical centers and limited work on how clinically acquired vessel-encoded pseudocontinuous arterial spin labeling data correlate with gold-standard methods. The purpose of this work is to develop and validate a semiautomated pipeline for the online quantification of cerebral blood flow maps and cerebral blood flow territories from planning-free vessel-encoded pseudocontinuous arterial spin labeling MRI with gold-standard digital subtraction angiography. Healthy controls (n = 10) and intracranial atherosclerotic disease patients (n = 34) underwent 3.0 T MRI imaging including vascular (MR angiography) and hemodynamic (cerebral blood flow-weighted arterial spin labeling) MRI. Patients additionally underwent catheter and/or CT angiography. Variations in cross-territorial filling were grouped according to diameters of circle of Willis vessels in controls. In patients, Cohen’s k-statistics were computed to quantify agreement in perfusion patterns between vessel-encoded pseudocontinuous arterial spin labeling and angiography. Cross-territorial filling patterns were consistent with circle of Willis anatomy. The intraobserver Cohen's k-statistics for cerebral blood flow territory and digital subtraction angiography perfusion agreement were 0.730 (95% CI = 0.593–0.867; reader one) and 0.708 (95% CI = 0.561–0.855; reader two). These results support the feasibility of a semiautomated pipeline for evaluating major neurovascular cerebral blood flow territories in patients with intracranial atherosclerotic disease. PMID:27389177

  19. Evaluation of arterial digital blood flow using Doppler ultrasonography in healthy dairy cows.

    PubMed

    Müller, H; Heinrich, M; Mielenz, N; Reese, S; Steiner, A; Starke, A

    2017-06-06

    Local circulatory disturbances have been implicated in the development of foot disorders in cattle. The goals of this study were to evaluate the suitability of the interdigital artery in the pastern region in both hind limbs using pulsed-wave (PW) Doppler ultrasonography and to investigate quantitative arterial blood flow variables at that site in dairy cows. An Esaote MyLabOne ultrasound machine with a 10-MHz linear transducer was used to assess blood flow in the interdigital artery in the pastern region in both hind limbs of 22 healthy German Holstein cows. The cows originated from three commercial farms and were restrained in a standing hoof trimming chute without sedation. A PW Doppler signal suitable for analysis was obtained in 17 of 22 cows. The blood flow profiles were categorised into four curve types, and the following quantitative variables were measured in three uniform cardiac cycles: vessel diameter, pulse rate, maximum systolic velocity, maximum diastolic velocity, end-diastolic velocity, reverse velocity, maximum time-averaged mean velocity, blood flow rate, resistance index and persistence index. The measurements did not differ among cows from the three farms. Maximum systolic velocity, vessel diameter and pulse rate did not differ but other variables differed significantly among blood flow profiles. Differences in weight-bearing are thought to be responsible for the normal variability of blood flow profiles in healthy cows. The scanning technique used in this report for evaluation of blood flow in the interdigital artery appears suitable for further investigations in healthy and in lame cows.

  20. Renal cortical and medullary blood flow responses to altered NO availability in humans.

    PubMed

    Damkjær, Mads; Vafaee, Manoucher; Møller, Michael L; Braad, Poul Erik; Petersen, Henrik; Høilund-Carlsen, Poul Flemming; Bie, Peter

    2010-12-01

    The objective of this study was to quantify regional renal blood flow in humans. In nine young volunteers on a controlled diet, the lower abdomen was CT-scanned, and regional renal blood flow was determined by positron emission tomography (PET) scanning using H(2)(15)O as tracer. Measurements were performed at baseline, during constant intravenous infusion of nitric oxide (NO) donor glyceryl nitrate and after intravenous injection of NO synthase inhibitor N(ω)-monomethyl-L-arginine (L-NMMA). Using the CT image, the kidney pole areas were delineated as volumes of interest (VOI). In the data analysis, tissue layers with a thickness of one voxel were eliminated stepwise from the external surface of the VOI (voxel peeling), and the blood flow subsequently was determined in each new, reduced VOI. Blood flow in the shrinking VOIs decreased as the number of cycles of voxel peeling increased. After 4-5 cycles, blood flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ± 0.17 ml·g tissue(-1)·min(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ± 0.18 ml·g tissue(-1)·min(-1) (P < 0.05) and decreased after L-NMMA injection to 1.57 ± 0.17 ml·g tissue(-1)·min(-1) (P < 0.05). Cortical blood flow was 4.67 ± 0.31 ml·g tissue(-1)·min(-1) during control, unchanged by glyceryl nitrate, and decreased after L-NMMA [3.48 ± 0.23 ml·(g·min)(-1), P < 0.05]. PET/CT scanning allows identification of a renal medullary region in which the measured blood flow is 1) low, 2) independent of reduction in the VOI, and 3) reactive to changes in systemic NO supply. The technique seems to provide indices of renal medullary blood flow in humans.

  1. Radiohalogenated thienylethylamine derivatives for evaluating local cerebral blood flow

    DOEpatents

    Goodman, Mark M.; Knapp, Jr., Furn F.

    1990-01-01

    Radiopharmaceuticals useful in brain imaging comprising radiohalogenated thienylethylamine derivatives. The compounds are 5-halo-thiophene-2-isopropyl amines able to cross the blood-brain barrier and be retained for a sufficient length of time to allow the evaluation or regional blood flow by radioimaging of the brain.

  2. The effect of resting blood flow occlusion on exercise tolerance and W'.

    PubMed

    Broxterman, Ryan M; Craig, Jesse C; Ade, Carl J; Wilcox, Samuel L; Barstow, Thomas J

    2015-09-15

    It has previously been postulated that the anaerobic work capacity (W') may be utilized during resting blood flow occlusion in the absence of mechanical work. We tested the hypothesis that W' would not be utilized during an initial range of time following the onset of resting blood flow occlusion, after which W' would be utilized progressively more. Seven men completed blood flow occlusion constant power severe intensity handgrip exercise to task failure following 0, 300, 600, 900, and 1,200 s of resting blood flow occlusion. The work performed above critical power (CP) was not significantly different between the 0-, 300-, and 600-s conditions and was not significantly different from the total W' available. Significantly less work was performed above CP during the 1,200-s condition than the 900-s condition (P < 0.05), while both conditions were significantly less than the 0-, 300-, and 600-s conditions (P < 0.05). The work performed above CP during these conditions was significantly less than the total W' available (P < 0.05). The utilization of W' during resting blood flow occlusion did not begin until 751 ± 118 s, after which time W' was progressively utilized. The current findings demonstrate that W' is not utilized during the initial ∼751 s of resting blood flow occlusion, but is progressively utilized thereafter, despite no mechanical work being performed. Thus, the utilization of W' is not exclusive to exercise, and a constant amount of work that can be performed above CP is not the determining mechanism of W'. Copyright © 2015 the American Physiological Society.

  3. The effect of blood cell count on coronary flow in patients with coronary slow flow phenomenon

    PubMed Central

    Soylu, Korhan; Gulel, Okan; Yucel, Huriye; Yuksel, Serkan; Aksan, Gokhan; Soylu, Ayşegül İdil; Demircan, Sabri; Yılmaz, Özcan; Sahin, Mahmut

    2014-01-01

    Background and Objective: The coronary slow flow phenomenon (CSFP) is a coronary artery disease with a benign course, but its pathological mechanisms are not yet fully understood.The purpose of this controlled study was to investigate the cellular content of blood in patients diagnosed with CSFP and the relationship of this with coronary flow rates. Methods: Selective coronary angiographies of 3368 patients were analyzed to assess Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) values. Seventy eight of them had CSFP, and their demographic and laboratory findings were compared with 61 patients with normal coronary flow. Results: Patients’ demographic characteristics were similar in both groups. Mean corrected TFC (cTFC) values were significantly elevated in CSFP patients (p<0.001). Furthermore, hematocrit and hemoglobin values, and eosinophil and basophil counts of the CSFP patients were significantly elevated compared to the values obtained in the control group (p=0.005, p=0.047, p=0.001 and p=0.002, respectively). The increase observed in hematocrit and eosinophil levels showed significant correlations with increased TFC values (r=0.288 and r=0.217, respectively). Conclusion: Significant changes have been observed in the cellular composition of blood in patients diagnosed with CSFP as compared to the patients with normal coronary blood flow. The increases in hematocrit levels and in the eosinophil and basophil counts may have direct or indirect effects on the rate of coronary blood flow. PMID:25225502

  4. Phasic changes in human right coronary blood flow before and after repair of aortic insufficiency.

    PubMed

    Folts, J D; Rowe, G G; Kahn, D R; Young, W P

    1979-02-01

    We have shown previously that acute aortic insufficiency in chronically instrumented dogs reverses the normally high ratio of diastolic to systolic coronary blood flow. Phasic blood flow in the dominant right coronary artery was measured directly with an electromagnetic flow meter during surgery in eight patients with severe aortic insufficiency before and after relacement of the aortic valve. Before the insufficiency was eliminated, right coronary flow average 116 +/- 37 ml./minute and the diastolic to systolic flow ratio was 0.88 +/- 17. Mean arterial blood pressure averaged 106 +/- 17 mm. Hg, heart rate 84 +/- 19 beats/minute, and mean diastolic pressure averaged 67 +/- 10 mm. Hg. After the aortic valve was replaced with an average heart rate of 90 +/- 15 and mean blood pressure of 103 +/- 13 mm. Hg, the average right coronary blood flow increased to 180 +/- 40 ml./minute with a D/S ratio of 2.18 +/- 0.8. In all cases the right coronary blood flow increased after the aortic insufficiency was eliminated surgically. Right coronary flow probably increased because of the improved diastolic perfusion pressure and the change from predominantly systolic to diastolic coronary flow.

  5. Multimodal in vivo blood flow sensing combining particle image velocimetry and optical tweezers-based blood steering

    NASA Astrophysics Data System (ADS)

    Meissner, Robert; Sugden, Wade W.; Siekmann, Arndt F.; Denz, Cornelia

    2018-02-01

    All higher developed organisms contain complex hierarchical networks of arteries, veins and capillaries. These constitute the cardiovascular system responsible for supplying nutrients, gas and waste exchange. Diseases related to the cardiovascular system are among the main causes for death worldwide. In order to understand the processes leading to arteriovenous malformation, we studied hereditary hemorrhagic telangiectasia (HHT), which has a prevalence of 1:5000 worldwide and causes internal bleeding. In zebrafish, HHT is induced by mutation of the endoglin gene involved in HHT and observed to reduce red blood cell (RBC) flow to intersegmental vessels (ISVs) in the tail due to malformations of the dorsal aorta (DA) and posterior cardinal vein (PCV). However, these capillaries are still functional. Changes in the blood flow pattern are observed from in vivo data from zebrafish embryos through particle image velocimetry (PIV). Wall shear rates (WSRs) and blood flow velocities are obtained non-invasively with millisecond resolution. We observe significant increases of blood flow velocity in the DA for endoglin-deficient zebrafish embryos (mutants) at 3 days post fertilization. In the PCV, this increase is even more pronounced. We identified an increased similarity between the DA and the PCV of mutant fish compared to siblings, i.e., unaffected fish. To counteract the reduced RBC flow to ISVs we implement optical tweezers (OT). RBCs are steered into previously unperfused ISVs showing a significant increase of RBC count per minute. We discuss limitations with respect to biocompatibility of optical tweezers in vivo and determination of in vivo wall shear stress (WSS) connected to normal and endoglin-deficicent zebrafish embryos.

  6. Influence of cold water immersion on limb and cutaneous blood flow at rest.

    PubMed

    Gregson, Warren; Black, Mark A; Jones, Helen; Milson, Jordon; Morton, James; Dawson, Brian; Atkinson, Greg; Green, Daniel J

    2011-06-01

    Cold water immersion reduces exercise-induced muscle damage. Benefits may partly arise from a decline in limb blood flow; however, no study has comprehensively investigated the influence of different degrees of cooling undertaken via cold water immersion on limb blood flow responses. To determine the influence of cold (8°C) and cool (22°C) water immersion on lower limb and cutaneous blood flow. Controlled laboratory study. Nine men were placed in a semireclined position and lowered into 8°C or 22°C water to the iliac crest for two 5-minute periods interspersed with 2 minutes of nonimmersion. Rectal and thigh skin temperature, deep and superficial muscle temperature, heart rate, mean arterial pressure, thigh cutaneous blood velocity (laser Doppler), and superficial femoral artery blood flow (duplex ultrasound) were measured during immersion and for 30 minutes after immersion. Indices of vascular conductance were calculated (flux and blood flow/mean arterial pressure). Reductions in rectal temperature (8°C, 0.2° ± 0.1°C; 22°C, 0.1° ± 0.1°C) and thigh skin temperature (8°C, 6.2° ± 0.5°C; 22°C, 3.2° ± 0.2°C) were greater in 8°C water than in 22°C (P < .01). Femoral artery conductance was reduced to a similar extent immediately after immersion (~30%) and 30 minutes after immersion (~40%) under both conditions (P < .01). In contrast, there was less thigh cutaneous vasoconstriction during and after immersion in 8°C water compared with 22°C (P = .01). These data suggest that immersion at both temperatures resulted in similar whole limb blood flow but, paradoxically, more blood was distributed to the skin in the colder water. This suggests that colder temperatures may be associated with reduced muscle blood flow, which could provide an explanation for the benefits of cold water immersion in alleviating exercise-induced muscle damage in sports and athletic contexts. Colder water temperatures may be more effective in the treatment of exercise

  7. Skin and muscle components of forearm blood flow in directly heated resting man.

    NASA Technical Reports Server (NTRS)

    Detry, J.-M. R.; Brengelmann, G. L.; Rowell, L. B.; Wyss, C.

    1972-01-01

    Changes in forearm muscle blood flow (FMBF) during direct whole-body heating were measured in 17 normal subjects using three different methods. We conclude that FMBF is not increased by direct whole-body heating. Since renal and splanchnic blood flow fall 30% under these conditions, maximal total skin blood flow in 12 previously studied subjects can be estimated from the rise in cardiac output to be 7.6 L/min (3.0-11.1 L/min).

  8. [Cerebral blood flow assessment of preterm infants during respiratory therapy with the expiratory flow increase technique].

    PubMed

    Bassani, Mariana Almada; Caldas, Jamil Pedro Siqueira; Netto, Abimael Aranha; Marba, Sérgio Tadeu Martins

    2016-06-01

    To assess the impact of respiratory therapy with the expiratory flow increase technique on cerebral hemodynamics of premature newborns. This is an intervention study, which included 40 preterm infants (≤34 weeks) aged 8-15 days of life, clinically stable in ambient air or oxygen catheter use. Children with heart defects, diagnosis of brain lesion and/or those using vasoactive drugs were excluded. Ultrasonographic assessments with transcranial Doppler flowmetry were performed before, during and after the increase in expiratory flow session, which lasted 5minutes. Cerebral blood flow velocity and resistance and pulsatility indices in the pericallosal artery were assessed. Respiratory physical therapy did not significantly alter flow velocity at the systolic peak (p=0.50), the end diastolic flow velocity (p=0.17), the mean flow velocity (p=0.07), the resistance index (p=0.41) and the pulsatility index (p=0.67) over time. The expiratory flow increase technique did not affect cerebral blood flow in clinically-stable preterm infants. Copyright © 2015 Sociedade de Pediatria de São Paulo. Publicado por Elsevier Editora Ltda. All rights reserved.

  9. Comparison of non-invasive MRI measurements of cerebral blood flow in a large multisite cohort.

    PubMed

    Dolui, Sudipto; Wang, Ze; Wang, Danny Jj; Mattay, Raghav; Finkel, Mack; Elliott, Mark; Desiderio, Lisa; Inglis, Ben; Mueller, Bryon; Stafford, Randall B; Launer, Lenore J; Jacobs, David R; Bryan, R Nick; Detre, John A

    2016-07-01

    Arterial spin labeling and phase contrast magnetic resonance imaging provide independent non-invasive methods for measuring cerebral blood flow. We compared global cerebral blood flow measurements obtained using pseudo-continuous arterial spin labeling and phase contrast in 436 middle-aged subjects acquired at two sites in the NHLBI CARDIA multisite study. Cerebral blood flow measured by phase contrast (CBFPC: 55.76 ± 12.05 ml/100 g/min) was systematically higher (p < 0.001) and more variable than cerebral blood flow measured by pseudo-continuous arterial spin labeling (CBFPCASL: 47.70 ± 9.75). The correlation between global cerebral blood flow values obtained from the two modalities was 0.59 (p < 0.001), explaining less than half of the observed variance in cerebral blood flow estimates. Well-established correlations of global cerebral blood flow with age and sex were similarly observed in both CBFPCASL and CBFPC CBFPC also demonstrated statistically significant site differences, whereas no such differences were observed in CBFPCASL No consistent velocity-dependent effects on pseudo-continuous arterial spin labeling were observed, suggesting that pseudo-continuous labeling efficiency does not vary substantially across typical adult carotid and vertebral velocities, as has previously been suggested. Although CBFPCASL and CBFPC values show substantial similarity across the entire cohort, these data do not support calibration of CBFPCASL using CBFPC in individual subjects. The wide-ranging cerebral blood flow values obtained by both methods suggest that cerebral blood flow values are highly variable in the general population. © The Author(s) 2016.

  10. Multi-modal in vivo imaging of brain blood oxygenation, blood flow and neural calcium dynamics during acute seizures

    NASA Astrophysics Data System (ADS)

    Ringuette, Dene; Jeffrey, Melanie A.; Carlen, Peter L.; Levi, Ofer

    2016-03-01

    Dysfunction of the vascular endothelium has been implicated in the development of epilepsy. To better understand the relation between vascular function and seizure and provide a foundation for interpreting results from functional imaging in chronic disease models, we investigate the relationship between intracellular calcium dynamics and local cerebral blood flow and blood oxygen saturation during acute seizure-like events and pharmacological seizure rescue. To probe the relation between the aforementioned physiological markers in an acute model of epilepsy in rats, we integrated three different optical modalities together with electrophysiological recordings: Laser speckle contrast imaging (LSCI) was used to study changes in flow speeds, Intrinsic optical signal imaging (IOSI) was used to monitor changes in oxygenated, de-oxygenated, and total hemoglobin concentration, and Calcium-sensitive dye imaging was used to monitor intracellular calcium dynamics. We designed a dedicated cortical flow chamber to remove superficial blood and dye resulting from the injection procedure, which reduced spurious artifacts. The near infrared light used for IOSI and LSCI was delivered via a light pipe integrated with the flow chamber to minimize the effect of fluid surface movement on illumination stability. Calcium-sensitive dye was injected via a glass electrode used for recording the local field potential. Our system allowed us to observe and correlate increases in intracellular calcium, blood flow and blood volume during seizure-like events and provide a quantitative analysis of neurovascular coupling changes associated with seizure rescue via injection of an anti-convulsive agent.

  11. Microconfined flow behavior of red blood cells.

    PubMed

    Tomaiuolo, Giovanna; Lanotte, Luca; D'Apolito, Rosa; Cassinese, Antonio; Guido, Stefano

    2016-01-01

    Red blood cells (RBCs) perform essential functions in human body, such as gas exchange between blood and tissues, thanks to their ability to deform and flow in the microvascular network. The high RBC deformability is mainly due to the viscoelastic properties of the cell membrane. Since an impaired RBC deformability could be found in some diseases, such as malaria, sickle cell anemia, diabetes and hereditary disorders, there is the need to provide further insight into measurement of RBC deformability in a physiologically relevant flow field. Here, RBCs deformability has been studied in terms of the minimum apparent plasma-layer thickness by using high-speed video microscopy of RBCs flowing in cylindrical glass capillaries. An in vitro systematic microfluidic investigation of RBCs in micro-confined conditions has been performed, resulting in the determination of the RBCs time recovery constant, RBC volume and surface area and RBC membrane shear elastic modulus and surface viscosity. It has been noticed that the deformability of RBCs induces cells aggregation during flow in microcapillaries, allowing the formation of clusters of cells. Overall, our results provide a novel technique to estimate RBC deformability and also RBCs collective behavior, which can be used for the analysis of pathological RBCs, for which reliable quantitative methods are still lacking. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

  12. Effects of three postexercice recovery treatments on femoral artery blood flow kinetics.

    PubMed

    Ménétrier, A; Mourot, L; Degano, B; Bouhaddi, M; Walther, G; Regnard, J; Tordi, N

    2015-04-01

    This study aimed to compare the kinetics of muscle leg blood flow during three recovery treatments following a prolonged exercise: contrast water therapy (CWT), compression stockings (CS) or passive recovery (PR). Fifteen men came to the laboratory three times to perform a 45-min exercise followed 5 min after by a standardized 12-min recovery treatment in upright position, alternating between two vats every 2 min: CWT (cold: ~12 °C to warm: 36 °C), CS (~20 mmHg) or PR. The order of treatments was randomized. Blood flow was measured using Doppler ultrasound during the recovery treatments (i.e., min 3, 5, 7 and 9) in the superficial femoral artery distally to the common bifurcation (~3 cm) (above the water and stocking). Blood flow was significantly higher during CWT (P<0.01; +22.91%) and CS (P<0.05; +15.26%) than during PR. Although no statistical difference between CWT and CS was observed, effect sizes were larger during CWT (large) than during CS (moderate). No changes in blood flow occurred in the femoral artery between hot and cold transitions of CWT. During immediate recovery of a high intensity exercise, CWT and CS trigger higher femoral artery blood flow than PR. Moreover, effect sizes were greater during CWT than during CS.

  13. Modeling of the blood rheology in steady-state shear flows

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Apostolidis, Alex J.; Beris, Antony N., E-mail: beris@udel.edu

    We undertake here a systematic study of the rheology of blood in steady-state shear flows. As blood is a complex fluid, the first question that we try to answer is whether, even in steady-state shear flows, we can model it as a rheologically simple fluid, i.e., we can describe its behavior through a constitutive model that involves only local kinematic quantities. Having answered that question positively, we then probe as to which non-Newtonian model best fits available shear stress vs shear-rate literature data. We show that under physiological conditions blood is typically viscoplastic, i.e., it exhibits a yield stress thatmore » acts as a minimum threshold for flow. We further show that the Casson model emerges naturally as the best approximation, at least for low and moderate shear-rates. We then develop systematically a parametric dependence of the rheological parameters entering the Casson model on key physiological quantities, such as the red blood cell volume fraction (hematocrit). For the yield stress, we base our description on its critical, percolation-originated nature. Thus, we first determine onset conditions, i.e., the critical threshold value that the hematocrit has to have in order for yield stress to appear. It is shown that this is a function of the concentration of a key red blood cell binding protein, fibrinogen. Then, we establish a parametric dependence as a function of the fibrinogen and the square of the difference of the hematocrit from its critical onset value. Similarly, we provide an expression for the Casson viscosity, in terms of the hematocrit and the temperature. A successful validation of the proposed formula is performed against additional experimental literature data. The proposed expression is anticipated to be useful not only for steady-state blood flow modeling but also as providing the starting point for transient shear, or more general flow modeling.« less

  14. Acute Inactivity Impairs Glycemic Control but Not Blood Flow to Glucose Ingestion

    PubMed Central

    Reynolds, Leryn J; Credeur, Daniel P; Holwerda, Seth W; Leidy, Heather J; Fadel, Paul J; Thyfault, John P

    2014-01-01

    Purpose Insulin-stimulated increases in skeletal muscle blood flow play a role in glucose disposal. Indeed, 7 days of aerobic exercise in type 2 diabetes patients increased blood flow responses to an oral glucose tolerance test (OGTT) and improved glucose tolerance. More recent work suggests that reduced daily physical activity impairs glycemic control (GC) in healthy individuals. Herein, we sought to determine if an acute reduction in daily activity (from >10,000 to <5,000 steps/day) for 5 days (RA5) in healthy individuals reduced insulin-stimulated blood flow and GC in parallel and if a 1 day return to activity (RTA1) improved these outcomes. Methods OGTTs were performed as a stimulus to increase insulin in 14 healthy, recreationally active men (24±1.1 yrs) at baseline, RA5, and RTA1. Measures of insulin sensitivity (Matsuda index) and femoral and brachial artery blood flow were made during the OGTT. Free living measures of GC including peak postprandial glucose (peak PPG) were also made via continuous glucose monitoring. Results Femoral and brachial artery blood flow increased during the OGTT but neither was significantly impacted by changes in physical activity (p>0.05). However, insulin sensitivity was decreased by RA5 (11.3±1.5 to 8.0±1.0; p<0.05). Likewise, free living GC measures of peak post prandial blood glucose (113±3 to 123±5 mg/dL; p<0.05) was significantly increased at RA5. Interestingly, insulin sensitivity and GC as assessed by peak PPG were not restored after RTA1 (p>0.05). Conclusions Thus, acute reductions in physical activity impaired GC and insulin sensitivity; however blood flow responses to an OGTT were not affected. Further, a 1 day return to activity was not sufficient to normalize GC following 5 days of reduced daily physical activity. PMID:25207931

  15. Using the developed cross-flow filtration chip for collecting blood plasma under high flow rate condition and applying the immunoglobulin E detection

    NASA Astrophysics Data System (ADS)

    Yeh, Chia-Hsien; Hung, Chia-Wei; Wu, Chun-Han; Lin, Yu-Cheng

    2014-09-01

    This paper presents a cross-flow filtration chip for separating blood cells (white blood cells, red blood cells, and platelets) and obtaining blood plasma from human blood. Our strategy is to flow the sample solution in parallel to the membrane, which can generate a parallel shear stress to remove the clogging microparticles on the membrane, so the pure sample solution is obtained in the reservoir. The cross-flow filtration chip includes a cross-flow layer, a Ni-Pd alloy micro-porous membrane, and a reservoir layer. The three layers are packaged in a polymethylmethacrylate (PMMA) frame to create the cross-flow filtration chip. Various dilutions of the blood sample (original, 2 × , 3 × , 5 × , and 10×), pore sizes with different diameters (1 µm, 2 µm, 4 µm, 7 µm, and 10 µm), and different flow rates (1 mL/min, 3 mL/min, 5 mL/min, 7 mL/min, and 10 mL/min) are tested to determine their effects on filtration percentage. The best filtration percentage is 96.2% when the dilution of the blood sample is 10 × , the diameter of pore size of a Ni-Pd alloy micro-porous membrane is 2 µm, and the flow rate is 10 mL/min. Finally, for the clinical tests of the immunoglobulin E (IgE) concentration, the cross-flow filtration chip is used to filter the blood of the allergy patients to obtain the blood plasma. This filtered blood plasma is compared with that obtained using the conventional centrifugation based on the enzyme-linked immunosorbent assay. The results reveal that these two blood separation methods have similar detection trends. The proposed filtration chip has the advantages of low cost, short filtration time, and easy operation and thus can be applied to the separation of microparticles, cells, bacteria, and blood.

  16. The alpha (α)-glucosidase inhibitor, acarbose, attenuates the blood pressure and splanchnic blood flow responses to intraduodenal sucrose in older adults.

    PubMed

    Gentilcore, Diana; Vanis, Lora; Wishart, Judith M; Rayner, Christopher K; Horowitz, Michael; Jones, Karen L

    2011-08-01

    Postprandial hypotension is an important problem in the elderly and may be triggered by the increase in splanchnic blood flow induced by a meal. Acarbose attenuates the fall in blood pressure (BP) induced by oral sucrose and may be useful in the management of postprandial hypotension. It is not known whether the effect of acarbose on postprandial BP reflects slowing of gastric emptying and/or carbohydrate absorption nor whether acarbose affects splanchnic blood flow. We examined the effects of intraduodenal (ID) acarbose on the BP, heart rate, superior mesenteric artery (SMA) flow, and glycemic and insulin responses to ID sucrose in older participants--this approach excluded any "gastric" effect of acarbose. Eight healthy participants (four male and four female, age 66-77 years) received an ID infusion of sucrose (~6 kcal/min), with or without acarbose (100 mg), over 60 minutes. BP, heart rate, SMA flow, blood glucose, and serum insulin were measured. Acarbose markedly attenuated the falls in systolic (p < .01) and diastolic (p < .05) BP and rises in heart rate (p < .05), SMA flow (p < .05), blood glucose (p < .01), and serum insulin (p < .05). The maximum fall in systolic BP and peak SMA flow was inversely related on the control day (r(2) = -.53, p < .05) but not with acarbose (r(2) = .03, p = .70). We conclude that in healthy older participants receiving ID sucrose, (a) acarbose markedly attenuates the hypotensive response by slowing carbohydrate absorption and attenuating the rise in splanchnic blood flow and (b) the fall in BP is related to the concomitant increase in SMA flow.

  17. Atlas of computerized blood flow analysis in bone disease.

    PubMed

    Gandsman, E J; Deutsch, S D; Tyson, I B

    1983-11-01

    The role of computerized blood flow analysis in routine bone scanning is reviewed. Cases illustrating the technique include proven diagnoses of toxic synovitis, Legg-Perthes disease, arthritis, avascular necrosis of the hip, fractures, benign and malignant tumors, Paget's disease, cellulitis, osteomyelitis, and shin splints. Several examples also show the use of the technique in monitoring treatment. The use of quantitative data from the blood flow, bone uptake phase, and static images suggests specific diagnostic patterns for each of the diseases presented in this atlas. Thus, this technique enables increased accuracy in the interpretation of the radionuclide bone scan.

  18. Intraocular pressure, blood pressure, and retinal blood flow autoregulation: a mathematical model to clarify their relationship and clinical relevance.

    PubMed

    Guidoboni, Giovanna; Harris, Alon; Cassani, Simone; Arciero, Julia; Siesky, Brent; Amireskandari, Annahita; Tobe, Leslie; Egan, Patrick; Januleviciene, Ingrida; Park, Joshua

    2014-05-29

    This study investigates the relationship between intraocular pressure (IOP) and retinal hemodynamics and predicts how arterial blood pressure (BP) and blood flow autoregulation (AR) influence this relationship. A mathematical model is developed to simulate blood flow in the central retinal vessels and retinal microvasculature as current flowing through a network of resistances and capacitances. Variable resistances describe active and passive diameter changes due to AR and IOP. The model is validated by using clinically measured values of retinal blood flow and velocity. The model simulations for six theoretical patients with high, normal, and low BP (HBP-, NBP-, LBP-) and functional or absent AR (-wAR, -woAR) are compared with clinical data. The model predicts that NBPwAR and HBPwAR patients can regulate retinal blood flow (RBF) as IOP varies between 15 and 23 mm Hg and between 23 and 29 mm Hg, respectively, whereas LBPwAR patients do not adequately regulate blood flow if IOP is 15 mm Hg or higher. Hemodynamic alterations would be noticeable only if IOP changes occur outside of the regulating range, which, most importantly, depend on BP. The model predictions are consistent with clinical data for IOP reduction via surgery and medications and for cases of induced IOP elevation. The theoretical model results suggest that the ability of IOP to induce noticeable changes in retinal hemodynamics depends on the levels of BP and AR of the individual. These predictions might help to explain the inconsistencies found in the clinical literature concerning the relationship between IOP and retinal hemodynamics. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  19. Extracellular superoxide dismutase is necessary to maintain renal blood flow during sepsis development.

    PubMed

    Constantino, Larissa; Galant, Letícia Selinger; Vuolo, Francieli; Guarido, Karla Lorena; Kist, Luiza Wilges; de Oliveira, Giovanna Medeiros Tavares; Pasquali, Matheus Augusto de Bittencourt; de Souza, Cláudio Teodoro; da Silva-Santos, José Eduardo; Bogo, Maurício Reis; Moreira, José Cláudio Fonseca; Ritter, Cristiane; Dal-Pizzol, Felipe

    2017-12-01

    Extracellular superoxide dismutase (ECSOD) protects nitric oxide (NO) bioavailability by decreasing superoxide levels and preventing peroxynitrite generation, which is important in maintaining renal blood flow and in preventing acute kidney injury. However, the profile of ECSOD expression after sepsis is not fully understood. Therefore, we intended to evaluate the content and gene expression of superoxide dismutase (SOD) isoforms in the renal artery and their relation to renal blood flow. Sepsis was induced in Wistar rats by caecal ligation and perforation. Several times after sepsis induction, renal blood flow (12, 24 and 48 h); the renal arterial content of SOD isoforms, nitrotyrosine, endothelial and inducible nitric oxide synthase (e-NOS and i-NOS), and phosphorylated vasodilator-stimulated phosphoprotein (pVASP); and SOD activity (3, 6 and 12 h) were measured. The influence of a SOD inhibitor was also evaluated. An increase in ECSOD content was associated with decreased 3-nitrotyrosine levels. These events were associated with an increase in pVASP content and maintenance of renal blood flow. Moreover, previous treatment with a SOD inhibitor increased nitrotyrosine content and reduced renal blood flow. ECSOD appears to have a major role in decreasing peroxynitrite formation in the renal artery during the early stages of sepsis development, and its application can be important in renal blood flow control and maintenance during septic insult.

  20. Resting cerebral blood flow, attention, and aging.

    PubMed

    Bertsch, Katja; Hagemann, Dirk; Hermes, Michael; Walter, Christof; Khan, Robina; Naumann, Ewald

    2009-04-24

    Aging is accompanied by a decline of fluid cognitive functions, e.g., a slowing of information processing, working memory, and division of attention. This is at least partly due to structural and functional changes in the aging brain. Although a decrement of resting cerebral blood flow (CBF) has been positively associated with cognitive functions in patients with brain diseases, studies with healthy participants have revealed inconsistent results. Therefore, we investigated the relation between resting cerebral blood flow and cognitive functions (tonic and phasic alertness, selective and divided attention) in two samples of healthy young and older participants. We found higher resting CBF and better cognitive performances in the young than in the older sample. In addition, resting CBF was inversely correlated with selective attention in the young and with tonic alertness in the elderly participants. This finding is discussed with regard to the neural efficiency hypothesis of human intelligence.

  1. The future of irrigated agriculture under environmental flow requirements restrictions

    NASA Astrophysics Data System (ADS)

    Pastor, Amandine; Palazzo, Amanda; Havlik, Petr; Kabat, Pavel; Obersteiner, Michael; Ludwig, Fulco

    2016-04-01

    Water is not an infinite resource and demand from irrigation, household and industry is constantly increasing. This study focused on including global water availability including environmental flow requirements with water withdrawal from irrigation and other sectors at a monthly time-step in the GLOBIOM model. This model allows re-adjustment of land-use allocation, crop management, consumption and international trade. The GLOBIOM model induces an endogenous change in water price depending on water supply and demand. In this study, the focus was on how the inclusion of water resources affects land-use and, in particular, how global change will influence repartition of irrigated and rainfed lands at global scale. We used the climate change scenario including a radiative forcing of 8.5 W/m2 (RCP8.5), the socio-economic scenario (SSP2: middle-of-road), and the environmental flow method based on monthly flow allocation (the Variable Monthly Flow method) with high and low restrictions. Irrigation withdrawals were adjusted to a monthly time-step to account for biophysical water limitations at finer time resolution. Our results show that irrigated land might decrease up to 40% on average depending on the choice of EFR restrictions. Several areas were identified as future hot-spots of water stress such as the Mediterranean and Middle-East regions. Other countries were identified to be in safe position in terms of water stress such as North-European countries. Re-allocation of rainfed and irrigated land might be useful information for land-use planners and water managers at an international level to decide on appropriate legislations on climate change mitigation/adaptation when exposure and sensitivity to climate change is high and/or on adaptation measures to face increasing water demand. For example, some countries are likely to adopt measures to increase their water use efficiencies (irrigation system, soil and water conservation practices) to face water shortages, while

  2. A novel, microscope based, non invasive Laser Doppler flowmeter for choroidal blood flow assessment

    PubMed Central

    Strohmaier, C; Werkmeister, RM; Bogner, B; Runge, C; Schroedl, F; Brandtner, H; Radner, W; Schmetterer, L; Kiel, JW; Grabnerand, G; Reitsamer, HA

    2015-01-01

    Impaired ocular blood flow is involved in the pathogenesis of numerous ocular diseases like glaucoma or AMD. The purpose of the present study was to introduce and validate a novel, microscope based, non invasive laser Doppler flowmeter (NILDF) for measurement of blood flow in the choroid. The custom made NI-LDF was compared with a commercial fiber optic based laser Doppler flowmeter (Perimed PF4000). Linearity and stability of the NI-LDF were assessed in a silastic tubing model (i.d. 0.3 mm) at different flow rates (range 0.4 – 3 ml/h). In a rabbit model continuous choroidal blood flow measurements were performed with both instruments simultaneously. During blood flow measurements ocular perfusion pressure was changed by manipulations of intraocular pressure via intravitreal saline infusions. The NILDF measurement correlated linearly to intraluminal flow rates in the perfused tubing model (r = 0.99, p<0.05) and remained stable during a 1 hour measurement at a constant flow rate. Rabbit choroidal blood flow measured by the PF4000 and the NI-LDF linearly correlated with each other over the entire measurement range (r = 0.99, y = x* 1,01 – 12,35 P.U., p < 0,001). In conclusion, the NI-LDF provides valid, semi quantitative measurements of capillary blood flow in comparison to an established LDF instrument and is suitable for measurements at the posterior pole of the eye. PMID:21443871

  3. Non-Newtonian effects of blood flow on hemodynamics in distal vascular graft anastomoses.

    PubMed

    Chen, Jie; Lu, Xi-Yun; Wang, Wen

    2006-01-01

    Non-Newtonian fluid flow in a stenosed coronary bypass is investigated numerically using the Carreau-Yasuda model for the shear thinning behavior of the blood. End-to-side coronary bypass anastomosis is considered in a simplified model geometry where the host coronary artery has a 75% severity stenosis. Different locations of the bypass graft to the stenosis and different flow rates in the graft and in the host artery are studied. Particular attention is given to the non-Newtonian effect of the blood on the primary and secondary flow patterns in the host coronary artery and the wall shear stress (WSS) distribution there. Interaction between the jet flow from the stenosed artery and the flow from the graft is simulated by solving the three-dimensional Navier-Stokes equation coupled with the non-Newtonian constitutive model. Results for the non-Newtonian flow, the Newtonian flow and the rescaled Newtonian flow are presented. Significant differences in axial velocity profiles, secondary flow streamlines and WSS between the non-Newtonian and Newtonian fluid flows are revealed. However, reasonable agreement between the non-Newtonian and the rescaled Newtonian flows is found. Results from this study support the view that the residual flow in a partially occluded coronary artery interacts with flow in the bypass graft and may have significant hemodynamic effects in the host vessel downstream of the graft. Non-Newtonian property of the blood alters the flow pattern and WSS distribution and is an important factor to be considered in simulating hemodynamic effects of blood flow in arterial bypass grafts.

  4. Pulpal blood flow recorded from exposed dentine with a laser Doppler flow meter using red or infrared light.

    PubMed

    Kijsamanmith, Kanittha; Vongsavan, Noppakun; Matthews, Bruce

    2018-03-01

    To determine the percentage of the blood flow signal that is derived from dental pulp when recording from exposed dentine in a human premolar. Recordings were made from 7 healthy teeth in 5 subjects (aged 22-33 yr.) with a laser Doppler flow meter (Periflux 4001) using either a red (635 nm) or an infrared (780 nm) laser. After exposing dentine above the buccal pulpal horn (cavity diam. 1.6 mm, depth 3 mm) and isolating the crown with opaque rubber dam, blood flow was recorded alternately with infrared or red light from the exposed dentine under four conditions: before and after injecting local anaesthetic (3% Mepivacaine without vasoconstrictor) (LA) over the apex of the root of the tooth; after exposing the pulp by cutting a buccal, class V cavity in the tooth; and after sectioning the coronal pulp transversely through the exposure. There was no significant change in mean blood flow recorded with either light source when the tooth was anaesthetized or when the pulp was exposed. After the pulp had been sectioned, the blood flow recorded with infrared light fell by 67.8% and with red light, by 68.4%. The difference between these effects was not significant. When recording blood flow from exposed coronal dentine with either infrared or red light in a tooth isolated with opaque rubber dam, about 68% to the signal was contributed by the pulp. The signal:noise ratio was better with infrared than red light, and when recording from dentine than enamel. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Influence of protein ingestion on human splanchnic and whole-body oxygen consumption, blood flow, and blood temperature.

    PubMed

    Brundin, T; Wahren, J

    1994-05-01

    Splanchnic and whole-body oxygen uptake, blood flow, and blood temperature were studied in 10 healthy subjects before and during 2 hours after oral ingestion of 900 kJ of fish protein. Indirect calorimetry and catheter techniques were used, including blood thermometry in arterial, pulmonary arterial, and hepatic venous blood. After the meal, pulmonary oxygen uptake increased from a basal value of 272 +/- 11 to 332 +/- 23 mL/min. During the first postprandial hour, splanchnic oxygen uptake increased from 62 +/- 5 to 93 +/- 9 mL/min (+50%, P < .05), thereby accounting for 62% +/- 17% of the simultaneous increase in whole-body oxygen consumption. During the second postprandial hour, splanchnic oxygen uptake increased no further, whereas in the extrasplanchnic tissues the oxygen consumption increased, now accounting for the entire simultaneous increase in pulmonary oxygen uptake. Cardiac output increased from basal 6.4 +/- 0.4 to 7.5 +/- 0.5 L/min. Splanchnic blood flow changed little while the arteriohepatic venous oxygen difference increased from 46 +/- 3 to 54 +/- 4 mL/L. Arterial and hepatic venous blood temperatures increased by almost 0.3 degrees C, reflecting a considerable accumulation of heat, indicating a conversion into a positive thermal balance. It is concluded that after protein ingestion, (1) oxygen uptake increases mainly in the splanchnic organs during the first hour, and thereafter exclusively in the extrasplanchnic tissues; (2) the blood flow increases mainly in extrasplanchnic tissues; and (3) the blood temperature increases almost linearly, indicating an upward adjustment of the temperature setpoint in the central thermosensors.

  6. Histaminergic H3-Heteroreceptors as a Potential Mediator of Betahistine-Induced Increase in Cochlear Blood Flow.

    PubMed

    Bertlich, Mattis; Ihler, Friedrich; Freytag, Saskia; Weiss, Bernhard G; Strupp, Michael; Canis, Martin

    2015-01-01

    Betahistine is a histamine-like drug that is considered beneficial in Ménière's disease by increasing cochlear blood flow. Acting as an agonist at the histamine H1-receptor and as an inverse agonist at the H3-receptor, these receptors as well as the adrenergic α2-receptor were investigated for betahistine effects on cochlear blood flow. A total of 54 Dunkin-Hartley guinea pigs were randomly assigned to one of nine groups treated with a selection of H1-, H3- or α2-selective agonists and antagonists together with betahistine. Cochlear blood flow and mean arterial pressure were recorded for 3 min before and 15 min after infusion. Blockage of the H3- or α2-receptors caused a suppression of betahistine-mediated typical changes in cochlear blood flow or blood pressure. Activation of H3-receptors caused a drop in cochlear blood flow and blood pressure. H1-receptors showed no involvement in betahistine-mediated changes of cochlear blood flow. Betahistine most likely affects cochlear blood flow through histaminergic H3-heteroreceptors. © 2015 S. Karger AG, Basel.

  7. Skeletal muscle contractions uncoupled from gravitational loading directly increase cortical bone blood flow rates in vivo.

    PubMed

    Caulkins, Carrie; Ebramzadeh, Edward; Winet, Howard

    2009-05-01

    The direct and indirect effects of muscle contraction on bone microcirculation and fluid flow are neither well documented nor explained. However, skeletal muscle contractions may affect the acquisition and maintenance of bone via stimulation of bone circulatory and interstitial fluid flow parameters. The purposes of this study were to assess the effects of transcutaneous electrical neuromuscular stimulation (TENS)-induced muscle contractions on cortical bone blood flow and bone mineral content, and to demonstrate that alterations in blood flow could occur independently of mechanical loading and systemic circulatory mechanisms. Bone chamber implants were used in a rabbit model to observe real-time blood flow rates and TENS-induced muscle contractions. Video recording of fluorescent microspheres injected into the blood circulation was used to calculate changes in cortical blood flow rates. TENS-induced repetitive muscle contractions uncoupled from mechanical loading instantaneously increased cortical microcirculatory flow, directly increased bone blood flow rates by 130%, and significantly increased bone mineral content over 7 weeks. Heart rates and blood pressure did not significantly increase due to TENS treatment. Our findings suggest that muscle contraction therapies have potential clinical applications for improving blood flow to cortical bone in the appendicular skeleton. Copyright 2008 Orthopaedic Research Society

  8. Hemodynamics of physiological blood flow in the aorta with nonlinear anisotropic heart valve

    NASA Astrophysics Data System (ADS)

    Sotiropoulos, Fotis; Gilmanov, Anvar; Stolarski, Henryk

    2016-11-01

    The hemodynamic blood flow in cardiovascular system is one of the most important factor, which causing several vascular diseases. We developed a new Curvilinear Immersed Boundary - Finite Element - Fluid Structure Interaction (CURVIB-FE-FSI) method to analyze hemodynamic of pulsatile blood flow in a real aorta with nonlinear anisotropic aortic valve at physiological conditions. Hyperelastic material model, which is more realistic for describing heart valve have been incorporated in the CURVIB-FE-FSI code to simulate interaction of aortic heart valve with pulsatile blood flow. Comparative studies of hemodynamics for linear and nonlinear models of heart valve show drastic differences in blood flow patterns and hence differences of stresses causing impact at leaflets and aortic wall. This work is supported by the Lillehei Heart Institute at the University of Minnesota.

  9. Thermography-based blood flow imaging in human skin of the hands and feet: a spectral filtering approach.

    PubMed

    Sagaidachnyi, A A; Fomin, A V; Usanov, D A; Skripal, A V

    2017-02-01

    The determination of the relationship between skin blood flow and skin temperature dynamics is the main problem in thermography-based blood flow imaging. Oscillations in skin blood flow are the source of thermal waves propagating from micro-vessels toward the skin's surface, as assumed in this study. This hypothesis allows us to use equations for the attenuation and dispersion of thermal waves for converting the temperature signal into the blood flow signal, and vice versa. We developed a spectral filtering approach (SFA), which is a new technique for thermography-based blood flow imaging. In contrast to other processing techniques, the SFA implies calculations in the spectral domain rather than in the time domain. Therefore, it eliminates the need to solve differential equations. The developed technique was verified within 0.005-0.1 Hz, including the endothelial, neurogenic and myogenic frequency bands of blood flow oscillations. The algorithm for an inverse conversion of the blood flow signal into the skin temperature signal is addressed. The examples of blood flow imaging of hands during cuff occlusion and feet during heating of the back are illustrated. The processing of infrared (IR) thermograms using the SFA allowed us to restore the blood flow signals and achieve correlations of about 0.8 with a waveform of a photoplethysmographic signal. The prospective applications of the thermography-based blood flow imaging technique include non-contact monitoring of the blood supply during engraftment of skin flaps and burns healing, as well the use of contact temperature sensors to monitor low-frequency oscillations of peripheral blood flow.

  10. Modulation of radial blood flow during Braille character discrimination task.

    PubMed

    Murata, Jun; Matsukawa, K; Komine, H; Tsuchimochi, H

    2012-03-01

    Human hands are excellent in performing sensory and motor function. We have hypothesized that blood flow of the hand is dynamically regulated by sympathetic outflow during concentrated finger perception. To identify this hypothesis, we measured radial blood flow (RBF), radial vascular conductance (RVC), heart rate (HR), and arterial blood pressure (AP) during Braille reading performed under the blind condition in nine healthy subjects. The subjects were instructed to read a flat plate with raised letters (Braille reading) for 30 s by the forefinger, and to touch a blank plate as control for the Braille discrimination procedure. HR and AP slightly increased during Braille reading but remained unchanged during the touching of the blank plate. RBF and RVC were reduced during the Braille character discrimination task (decreased by -46% and -49%, respectively). Furthermore, the changes in RBF and RVC were much greater during the Braille character discrimination task than during the touching of the blank plate (decreased by -20% and -20%, respectively). These results have suggested that the distribution of blood flow to the hand is modulated via sympathetic nerve activity during concentrated finger perception.

  11. Detection of Site-Specific Blood Flow Variation in Humans during Running by a Wearable Laser Doppler Flowmeter.

    PubMed

    Iwasaki, Wataru; Nogami, Hirofumi; Takeuchi, Satoshi; Furue, Masutaka; Higurashi, Eiji; Sawada, Renshi

    2015-10-05

    Wearable wireless physiological sensors are helpful for monitoring and maintaining human health. Blood flow contains abundant physiological information but it is hard to measure blood flow during exercise using conventional blood flowmeters because of their size, weight, and use of optic fibers. To resolve these disadvantages, we previously developed a micro integrated laser Doppler blood flowmeter using microelectromechanical systems technology. This micro blood flowmeter is wearable and capable of stable measurement signals even during movement. Therefore, we attempted to measure skin blood flow at the forehead, fingertip, and earlobe of seven young men while running as a pilot experiment to extend the utility of the micro blood flowmeter. We measured blood flow in each subject at velocities of 6, 8, and 10 km/h. We succeeded in obtaining stable measurements of blood flow, with few motion artifacts, using the micro blood flowmeter, and the pulse wave signal and motion artifacts were clearly separated by conducting frequency analysis. Furthermore, the results showed that the extent of the changes in blood flow depended on the intensity of exercise as well as previous work with an ergometer. Thus, we demonstrated the capability of this wearable blood flow sensor for measurement during exercise.

  12. Laser speckle contrast imaging of collateral blood flow during acute ischemic stroke

    PubMed Central

    Armitage, Glenn A; Todd, Kathryn G; Shuaib, Ashfaq; Winship, Ian R

    2010-01-01

    Collateral vasculature may provide an alternative route for blood flow to reach the ischemic tissue and partially maintain oxygen and nutrient support during ischemic stroke. However, much about the dynamics of stroke-induced collateralization remains unknown. In this study, we used laser speckle contrast imaging to map dynamic changes in collateral blood flow after middle cerebral artery occlusion in rats. We identified extensive anastomatic connections between the anterior and middle cerebral arteries that develop after vessel occlusion and persist for 24 hours. Augmenting blood flow through these persistent yet dynamic anastomatic connections may be an important but relatively unexplored avenue in stroke therapy. PMID:20517321

  13. Cerebral blood flow is reduced in patients with sepsis syndrome

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bowton, D.L.; Bertels, N.H.; Prough, D.S.

    The relationship between sepsis-induced CNS dysfunction and changes in brain blood flow remains unknown, and animal studies examining the influence of sepsis on cerebral blood flow (CBF) do not satisfactorily address that relationship. We measured CBF and cerebrovascular reactivity to CO/sub 2/ in nine patients with sepsis syndrome using the /sup 133/Xe clearance technique. Mean CBF was 29.6 +/- 15.8 (SD) ml/100 g.min, significantly lower than the normal age-matched value in this laboratory of 44.9 +/- 6.2 ml/100 g.min (p less than .02). This depression did not correlate with changes in mean arterial pressure. Despite the reduction in CBF, themore » specific reactivity of the cerebral vasculature to changes in CO/sub 2/ was normal, 1.3 +/- 0.9 ml/100 g.min/mm Hg. Brain blood flow is reduced in septic humans; the contribution of this reduction to the metabolic and functional changes observed in sepsis requires further study.« less

  14. Effect of antiorthostatic bed rest on hepatic blood flow in man.

    PubMed

    Putcha, L; Cintron, N M; Vanderploeg, J M; Chen, Y; Habis, J; Adler, J

    1988-04-01

    Physiological changes that occur during exposure to weightlessness may induce alterations in blood flow to the liver. Estimation of hepatic blood flow (HBF) using ground-based weightlessness simulation models may provide insight into functional changes of the liver in crewmembers during flight. In the present study HBF, indirectly estimated by indocyanine green (ICG) clearance, is compared in 10 subjects during the normal ambulatory condition and antiorthostatic (-6 degrees) bed rest. Plasma clearance of ICG was determined following intravenous administration of a 0.5-mg.kg-1 dose of ICG to each subject on two separate occasions, once after being seated for 1 h and once after 24 h of head-down bed rest. After 24 h of head-down bed rest, hepatic blood flow did not change significantly from the respective control value.

  15. Nephron blood flow dynamics measured by laser speckle contrast imaging

    PubMed Central

    Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V.; Pavlov, Alexey N.; Cupples, William A.; Sorensen, Charlotte Mehlin

    2011-01-01

    Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50–100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney. PMID:21048025

  16. Correction for partial volume effect in PET blood flow images

    NASA Astrophysics Data System (ADS)

    Gage, Howard D.; Fahey, Fredrick H.; Santago, Peter, II; Harkness, Beth A.; Keyes, J. W.

    1996-04-01

    Current positron emission tomography techniques for the measurement of cerebral blood flow assume that voxels represent pure material regions. In this work, a method is presented which utilizes anatomical information from a high resolution modality such as MRI in conjunction with a multicompartment extension of the Kety model to obtain intravoxel, tissue specific blood flow values. In order to evaluate the proposed method, noisy time activity curves (TACs) were simulated representing different combinations of gray matter, white matter and CSF, and ratios of gray to white matter blood flow. In all experiments it was assumed that registered MR data supplied the number of materials and the fraction of each present. For each TAC, three experiments were run. In the first it was assumed that the fraction of each material determined by MRI was correct, and, in the second two, that the value was either too high or too low. Using the tree annealing method, material flows were determined which gave the best fit of the model to the simulated TAC data. The results indicate that the accuracy of the method is approximately linearly related to the error in material fraction estimated for a voxel.

  17. Evaluation of Renal Blood Flow and Oxygenation in CKD Using Magnetic Resonance Imaging.

    PubMed

    Khatir, Dinah S; Pedersen, Michael; Jespersen, Bente; Buus, Niels H

    2015-09-01

    Animal studies suggest that progression of chronic kidney disease (CKD) is related to renal hypoxia. With renal blood supply determining oxygen delivery and sodium absorption being the main contributor to oxygen consumption, we describe the relationship between renal oxygenation, renal artery blood flow, and sodium absorption in patients with CKD and healthy controls. Cross-sectional study. 62 stable patients with CKD stages 3 to 4 (mean age, 61±13 [SD] years) and 24 age- and sex-matched controls. CKD versus control status. Renal artery blood flow, tissue oxygenation (relative changes in deoxyhemoglobin concentration of the renal medulla [MR2*] and cortex [CR2*]), and sodium absorption. Renal artery blood flow was determined by phase-contrast magnetic resonance imaging (MRI); MR2* and CR2* were determined by blood oxygen level-dependent MRI. Ultrafiltered and reabsorbed sodium were determined from measured glomerular filtration rate (mGFR) and 24-hour urine collections. mGFR in patients was 37% that of controls (36±15 vs 97±23 mL/min/1.73 m(2); P < 0.001), and reabsorbed sodium was 37% that of controls (6.9 vs 19.1 mol/24 h; P < 0.001). Single-kidney patient renal artery blood flow was 72% that of controls (319 vs 443 mL/min; P < 0.001). Glomerular filtration fraction was 9% in patients and 18% in controls (P < 0.001). Patients and controls had similar CR2* (13.4 vs 13.3 s(-1)) and medullary MR2* (26.4 vs 26.5 s(-1)) values. Linear regression analysis demonstrated no associations between R2* and renal artery blood flow or sodium absorption. Increasing arterial blood oxygen tension by breathing 100% oxygen had very small effects on CR2*, but reduced MR2* in both groups. Only renal artery blood flow was determined and thus regional perfusion could not be related to CR2* or MR2*. In CKD, reductions of mGFR and reabsorbed sodium are more than double that of renal artery blood flow, whereas cortical and medullary oxygenation are within the range of healthy persons

  18. Influence of cold-water immersion on limb blood flow after resistance exercise.

    PubMed

    Mawhinney, Chris; Jones, Helen; Low, David A; Green, Daniel J; Howatson, Glyn; Gregson, Warren

    2017-06-01

    This study determined the influence of cold (8°C) and cool (22°C) water immersion on lower limb and cutaneous blood flow following resistance exercise. Twelve males completed 4 sets of 10-repetition maximum squat exercise and were then immersed, semi-reclined, into 8°C or 22°C water for 10-min, or rested in a seated position (control) in a randomized order on different days. Rectal and thigh skin temperature, muscle temperature, thigh and calf skin blood flow and superficial femoral artery blood flow were measured before and after immersion. Indices of vascular conductance were calculated (flux and blood flow/mean arterial pressure). The colder water reduced thigh skin temperature and deep muscle temperature to the greatest extent (P < .001). Reductions in rectal temperature were similar (0.2-0.4°C) in all three trials (P = .69). Femoral artery conductance was similar after immersion in both cooling conditions, with both conditions significantly lower (55%) than the control post-immersion (P < .01). Similarly, there was greater thigh and calf cutaneous vasoconstriction (40-50%) after immersion in both cooling conditions, relative to the control (P < .01), with no difference between cooling conditions. These findings suggest that cold and cool water similarly reduce femoral artery and cutaneous blood flow responses but not muscle temperature following resistance exercise.

  19. FloWave.US: validated, open-source, and flexible software for ultrasound blood flow analysis.

    PubMed

    Coolbaugh, Crystal L; Bush, Emily C; Caskey, Charles F; Damon, Bruce M; Towse, Theodore F

    2016-10-01

    Automated software improves the accuracy and reliability of blood velocity, vessel diameter, blood flow, and shear rate ultrasound measurements, but existing software offers limited flexibility to customize and validate analyses. We developed FloWave.US-open-source software to automate ultrasound blood flow analysis-and demonstrated the validity of its blood velocity (aggregate relative error, 4.32%) and vessel diameter (0.31%) measures with a skeletal muscle ultrasound flow phantom. Compared with a commercial, manual analysis software program, FloWave.US produced equivalent in vivo cardiac cycle time-averaged mean (TAMean) velocities at rest and following a 10-s muscle contraction (mean bias <1 pixel for both conditions). Automated analysis of ultrasound blood flow data was 9.8 times faster than the manual method. Finally, a case study of a lower extremity muscle contraction experiment highlighted the ability of FloWave.US to measure small fluctuations in TAMean velocity, vessel diameter, and mean blood flow at specific time points in the cardiac cycle. In summary, the collective features of our newly designed software-accuracy, reliability, reduced processing time, cost-effectiveness, and flexibility-offer advantages over existing proprietary options. Further, public distribution of FloWave.US allows researchers to easily access and customize code to adapt ultrasound blood flow analysis to a variety of vascular physiology applications. Copyright © 2016 the American Physiological Society.

  20. Carotid blood flow changes with behavioral states in the late gestation llama fetus in utero.

    PubMed

    Blanco, C E; Giussani, D A; Riquelme, R A; Hanson, M A; Llanos, A J

    1997-12-19

    This study tested the hypothesis that in the llama fetus changes in cerebral blood flow are closely associated with changes in cerebral oxidative metabolism such as occur during transitions between electrocortical states. For the first time reported in any species, instantaneous changes in common carotid blood flow, employed as a continuous index of cerebrovascular perfusion, were related to instantaneous changes in electrocortical activity. Three late gestation fetal llamas were surgically prepared under general anesthesia with vascular catheters, a tracheal and amniotic catheter, and with electrodes implanted to monitor the fetal electrocorticogram (ECoG). In addition, Transonic flow probes were placed around a common carotid artery and a femoral artery. At least 4 days after surgery fetal arterial blood, amniotic and tracheal pressures, carotid and femoral blood flows and the fetal ECoG were recorded continuously. Our results suggest a close association between increases in common carotid blood flow and low voltage ECoG in the llama fetus. Close coupling between instantaneous changes in carotid blood flow and electrocortical states together with the lack of an increase in brain blood flow without increased cerebral oxygen extraction during hypoxemia in the llama fetus supports a fall in cerebral oxidative metabolism in this species during hypoxemic episodes.

  1. Age-Related Vascular Changes Affect Turbulence in Aortic Blood Flow

    PubMed Central

    Ha, Hojin; Ziegler, Magnus; Welander, Martin; Bjarnegård, Niclas; Carlhäll, Carl-Johan; Lindenberger, Marcus; Länne, Toste; Ebbers, Tino; Dyverfeldt, Petter

    2018-01-01

    Turbulent blood flow is implicated in the pathogenesis of several aortic diseases but the extent and degree of turbulent blood flow in the normal aorta is unknown. We aimed to quantify the extent and degree of turbulece in the normal aorta and to assess whether age impacts the degree of turbulence. 22 young normal males (23.7 ± 3.0 y.o.) and 20 old normal males (70.9 ± 3.5 y.o.) were examined using four dimensional flow magnetic resonance imaging (4D Flow MRI) to quantify the turbulent kinetic energy (TKE), a measure of the intensity of turbulence, in the aorta. All healthy subjects developed turbulent flow in the aorta, with total TKE of 3–19 mJ. The overall degree of turbulence in the entire aorta was similar between the groups, although the old subjects had about 73% more total TKE in the ascending aorta compared to the young subjects (young = 3.7 ± 1.8 mJ, old = 6.4 ± 2.4 mJ, p < 0.001). This increase in ascending aorta TKE in old subjects was associated with age-related dilation of the ascending aorta which increases the volume available for turbulence development. Conversely, age-related dilation of the descending and abdominal aorta decreased the average flow velocity and suppressed the development of turbulence. In conclusion, turbulent blood flow develops in the aorta of normal subjects and is impacted by age-related geometric changes. Non-invasive assessment enables the determination of normal levels of turbulent flow in the aorta which is a prerequisite for understanding the role of turbulence in the pathophysiology of cardiovascular disease. PMID:29422871

  2. Quantitative analysis of optical properties of flowing blood using a photon-cell interactive Monte Carlo code: effects of red blood cells' orientation on light scattering.

    PubMed

    Sakota, Daisuke; Takatani, Setsuo

    2012-05-01

    Optical properties of flowing blood were analyzed using a photon-cell interactive Monte Carlo (pciMC) model with the physical properties of the flowing red blood cells (RBCs) such as cell size, shape, refractive index, distribution, and orientation as the parameters. The scattering of light by flowing blood at the He-Ne laser wavelength of 632.8 nm was significantly affected by the shear rate. The light was scattered more in the direction of flow as the flow rate increased. Therefore, the light intensity transmitted forward in the direction perpendicular to flow axis decreased. The pciMC model can duplicate the changes in the photon propagation due to moving RBCs with various orientations. The resulting RBC's orientation that best simulated the experimental results was with their long axis perpendicular to the direction of blood flow. Moreover, the scattering probability was dependent on the orientation of the RBCs. Finally, the pciMC code was used to predict the hematocrit of flowing blood with accuracy of approximately 1.0 HCT%. The photon-cell interactive Monte Carlo (pciMC) model can provide optical properties of flowing blood and will facilitate the development of the non-invasive monitoring of blood in extra corporeal circulatory systems.

  3. Blood flow characteristics in the ascending aorta after TAVI compared to surgical aortic valve replacement.

    PubMed

    Trauzeddel, Ralf Felix; Löbe, Ulrike; Barker, Alex J; Gelsinger, Carmen; Butter, Christian; Markl, Michael; Schulz-Menger, Jeanette; von Knobelsdorff-Brenkenhoff, Florian

    2016-03-01

    Ascending aortic blood flow characteristics are altered after aortic valve surgery, but the effect of transcatheter aortic valve implantation (TAVI) is unknown. Abnormal flow may be associated with aortic and cardiac remodeling. We analyzed blood flow characteristics in the ascending aorta after TAVI in comparison to conventional stented aortic bioprostheses (AVR) and healthy subjects using time-resolved three-dimensional flow-sensitive cardiovascular magnetic resonance imaging (4D-flow MRI). Seventeen patients with TAVI (Edwards Sapien XT), 12 with AVR and 9 healthy controls underwent 4D-flow MRI of the ascending aorta. Target parameters were: severity of vortical and helical flow pattern (semiquantitative grading from 0 = none to 3 = severe) and the local distribution of systolic wall shear stress (WSSsystole). AVR revealed significantly more extensive vortical and helical flow pattern than TAVI (p = 0.042 and p = 0.002) and controls (p < 0.001 and p = 0.001). TAVI showed significantly more extensive vortical flow than controls (p < 0.001). Both TAVI and AVR revealed marked blood flow eccentricity (64.7 and 66.7%, respectively), whereas controls showed central blood flow (88.9%). TAVI and AVR exhibited an asymmetric distribution of WSSsystole in the mid-ascending aorta with local maxima at the right anterior aortic wall and local minima at the left posterior wall. In contrast, controls showed a symmetric distribution of WSSsystole along the aortic circumference. Blood flow was significantly altered in the ascending aorta after TAVI and AVR. Changes were similar regarding WSSsystole distribution, while TAVI resulted in less helical and vortical blood flow.

  4. Regulation of skeletal muscle blood flow during exercise in ageing humans

    PubMed Central

    Hearon, Christopher M.

    2015-01-01

    Abstract The regulation of skeletal muscle blood flow and oxygen delivery to contracting skeletal muscle is complex and involves the mechanical effects of muscle contraction; local metabolic, red blood cell and endothelium‐derived substances; and the sympathetic nervous system (SNS). With advancing age in humans, skeletal muscle blood flow is typically reduced during dynamic exercise and this is due to a lower vascular conductance, which could ultimately contribute to age‐associated reductions in aerobic exercise capacity, a primary predictor of mortality in both healthy and diseased ageing populations. Recent findings have highlighted the contribution of endothelium‐derived substances to blood flow control in contracting muscle of older adults. With advancing age, impaired nitric oxide availability due to scavenging by reactive oxygen species, in conjunction with elevated vasoconstrictor signalling via endothelin‐1, reduces the local vasodilatory response to muscle contraction. Additionally, ageing impairs the ability of contracting skeletal muscle to blunt sympathetic vasoconstriction (i.e. ‘functional sympatholysis’), which is critical for the proper regulation of tissue blood flow distribution and oxygen delivery, and could further reduce skeletal muscle perfusion during high intensity and/or large muscle mass exercise in older adults. We propose that initiation of endothelium‐dependent hyperpolarization is the underlying signalling event necessary to properly modulate sympathetic vasoconstriction in contracting muscle, and that age‐associated impairments in red blood cell adenosine triphosphate release and stimulation of endothelium‐dependent vasodilatation may explain impairments in both local vasodilatation and functional sympatholysis with advancing age in humans. PMID:26332887

  5. Quantitative flow and velocity measurements of pulsatile blood flow with 4D-DSA

    NASA Astrophysics Data System (ADS)

    Shaughnessy, Gabe; Hoffman, Carson; Schafer, Sebastian; Mistretta, Charles A.; Strother, Charles M.

    2017-03-01

    Time resolved 3D angiographic data from 4D DSA provides a unique environment to explore physical properties of blood flow. Utilizing the pulsatility of the contrast waveform, the Fourier components can be used to track the waveform motion through vessels. Areas of strong pulsatility are determined through the FFT power spectrum. Using this method, we find an accuracy from 4D-DSA flow measurements within 7.6% and 6.8% RMSE of ICA PCVIPR and phantom flow probe validation measurements, respectively. The availability of velocity and flow information with fast acquisition could provide a more quantitative approach to treatment planning and evaluation in interventional radiology.

  6. A novel, microscope based, non-invasive laser Doppler flowmeter for choroidal blood flow assessment.

    PubMed

    Strohmaier, C; Werkmeister, R M; Bogner, B; Runge, C; Schroedl, F; Brandtner, H; Radner, W; Schmetterer, L; Kiel, J W; Grabner, G; Reitsamer, H A

    2011-06-01

    Impaired ocular blood flow is involved in the pathogenesis of numerous ocular diseases like glaucoma or AMD. The purpose of the present study was to introduce and validate a novel, microscope based, non-invasive Laser Doppler Flowmeter (NI-LDF) for measurement of blood flow in the choroid. The custom made NI-LDF was compared with a commercial fiber optic based laser Doppler flowmeter (Perimed PF4000). Linearity and stability of the NI-LDF were assessed in a silastic tubing model (i.d. 0.3 mm) at different flow rates (range 0.4-3 ml/h). In a rabbit model continuous choroidal blood flow measurements were performed with both instruments simultaneously. During blood flow measurements ocular perfusion pressure was changed by manipulations of intraocular pressure via intravitreal saline infusions. The NI-LDF measurement correlated linearly to intraluminal flow rates in the perfused tubing model (r = 0.99, p < 0.05) and remained stable during a 1 h measurement at a constant flow rate. Rabbit choroidal blood flow measured by the PF4000 and the NI-LDF linearly correlated with each other over the entire measurement range (r = 0.99, y = x∗1.01-12.35 P.U., p < 0.001). In conclusion, the NI-LDF provides valid, semi quantitative measurements of capillary blood flow in comparison to an established LDF instrument and is suitable for measurements at the posterior pole of the eye. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Evaluating ocular blood flow

    PubMed Central

    Maram, Jyotsna; Srinivas, Sowmya; Sadda, Srinivas R

    2017-01-01

    Studies have shown that vascular impairment plays an important role in the etiology and pathogenesis of various ocular diseases including glaucoma, age-related macular degeneration, diabetic retinopathy, and retinal venous occlusive disease. Thus, qualitative and quantitative assessment of ocular blood flow (BF) is a topic of interest for early disease detection, diagnosis, and management. Owing to the rapid improvement in technology, there are several invasive and noninvasive techniques available for evaluating ocular BF, with each of these techniques having their own limitations and advantages. This article reviews these important techniques, with a particular focus on Doppler Fourier domain optical coherence tomography (OCT) and OCT-angiography. PMID:28573987

  8. Brain blood flow and cardiovascular responses to hot flashes in postmenopausal women

    PubMed Central

    Lucas, Rebekah A. I.; Ganio, Matthew S.; Pearson, James; Crandall, Craig G.

    2012-01-01

    Objective This study tested two related hypotheses: 1) that brain blood flow is reduced during the postmenopausal hot flash; and, 2) the magnitude of this reduction in brain blood flow is greater during hot flashes where blood pressure is reduced. Methods Eleven healthy, normotensive, postmenopausal women rested in a temperature-controlled laboratory (~25°C) for approximately 120 minutes while waiting for a hot flash to occur. The onset of a hot flash was objectively identified by an abrupt increase in sternal sweat rate (capacitance hygrometry). Middle cerebral artery blood velocity (MCAv, transcranial Doppler) and mean arterial pressure (Finometer®) were measured continuously. Each hot flash was divided into 8 equal segments and the segment with the largest reduction in MCAv and mean arterial pressure identified for each hot flash. Results Twenty-five hot flashes occurred during the experimental sessions (lasting 6.2 ± 2.8 min, 3 ± 1 hot flashes per participant). Seventy-six percent of hot flashes were accompanied by a clear reduction (greater than 5%) in brain blood flow. For all hot flashes, the average maximum decrease in MCAv was 12 ± 9% (7 ± 6 cm.s−1). This value did not correlate with corresponding changes in mean arterial pressure (R=0.36). Conclusion These findings demonstrate that hot flashes are often accompanied by clear reductions in brain blood flow that do not correspond with acute reductions in mean arterial blood pressure. PMID:23435027

  9. Evaluation of (/sup 18/F)-4-fluoroantipyrine as a new blood flow tracer for multiradionuclide autoradiography

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sako, K.; Diksic, M.; Kato, A.

    This article reports the evaluation of (/sup 18/F)-4-fluoroantipyrine (FAP) as a quantitative blood flow tracer by comparing blood flow measured with (/sup 18/F)FAP to that determined simultaneously with (/sup 14/C)-4-iodoantipyrine (IAP), a standard blood flow tracer, by means of double-tracer autoradiography. The single-pass extraction value (m), which indicates diffusibility of a tracer, was determined according to the procedure described by Crone. The diffusibility of FAP was essentially the same as that of IAP. The brain-blood partition coefficient for FAP was found to be similar to that for IAP, 0.89 +/- 0.01. Values of local cerebral blood flow obtained with FAPmore » agree with those determined with IAP. From these results, we concluded that FAP is indeed as good a blood flow tracer as IAP. Since /sup 18/F is a positron-emitting radionuclide, it might be a useful tracer for blood flow measurement by positron emission tomography.« less

  10. CFD simulation of blood flow inside the corkscrew collaterals of the Buerger's disease.

    PubMed

    Sharifi, Alireza; Charjouei Moghadam, Mohammad

    2016-01-01

    Buerger's disease is an occlusive arterial disease that occurs mainly in medium and small vessels. This disease is associated with Tobacco usage. The existence of corkscrew collateral is one of the established characteristics of the Buerger's disease. In this study, the computational fluid dynamics (CFD) simulation of blood flow within the corkscrew artery of the Buerger's disease is conducted. The geometry of the artery is constructed based on the actual corkscrew artery of a patient diagnosed with the Buerger's disease. The blood properties are the same as the actual blood properties of the patient. The blood flow rate is taken from the available experimental data in the literature. The local velocity patterns, pressure and kinematic viscosity distributions in different segments of the corkscrew collateral artery was demonstrated and discussed for the first time for this kind of artery. The effects of non-Newtonian consideration for the blood viscosity behavior were investigated in different segments of the artery. Moreover, the variations of the blood flow patterns along the artery were investigated in details for each segment. It was found that the flow patterns were affected by the complex geometry of this artery in such a way that it could lead to the presence of sites that were prone to the accumulation of the flowing particles in blood like nicotine. Furthermore, due to the existence of many successive bends in this artery, the variations of kinematic viscosity along this artery were significant, therefore the non-Newtonian behavior of the blood viscosity must be considered.

  11. Red blood cell transport mechanisms in polyester thread-based blood typing devices.

    PubMed

    Nilghaz, Azadeh; Ballerini, David R; Guan, Liyun; Li, Lizi; Shen, Wei

    2016-02-01

    A recently developed blood typing diagnostic based on a polyester thread substrate has shown great promise for use in medical emergencies and in impoverished regions. The device is easy to use and transport, while also being inexpensive, accurate, and rapid. This study used a fluorescent confocal microscope to delve deeper into how red blood cells were behaving within the polyester thread-based diagnostic at the cellular level, and how plasma separation could be made to visibly occur on the thread, making it possible to identify blood type in a single step. Red blood cells were stained and the plasma phase dyed with fluorescent compounds to enable them to be visualised under the confocal microscope at high magnification. The mechanisms uncovered were in surprising contrast with those found for a similar, paper-based method. Red blood cell aggregates did not flow over each other within the thread substrate as expected, but suffered from a restriction to their flow which resulted in the chromatographic separation of the RBCs from the liquid phase of the blood. It is hoped that these results will lead to the optimisation of the method to enable more accurate and sensitive detection, increasing the range of blood systems that can be detected.

  12. Differential visceral blood flow in the hyperdynamic circulation of patients with liver cirrhosis.

    PubMed

    McAvoy, N C; Semple, S; Richards, J M J; Robson, A J; Patel, D; Jardine, A G M; Leyland, K; Cooper, A S; Newby, D E; Hayes, P C

    2016-05-01

    With advancing liver disease and the development of portal hypertension, there are major alterations in somatic and visceral blood flow. Using phase-contrast magnetic resonance angiography, we characterised alterations in blood flow within the hepatic, splanchnic and extra-splanchnic circulations of patients with established liver cirrhosis. To compare blood flow in splanchnic and extra-splanchnic circulations in patients with varying degrees of cirrhosis and healthy controls. In a single-centre prospective study, 21 healthy volunteers and 19 patients with established liver disease (Child's stage B and C) underwent electrocardiogram-gated phase-contrast-enhanced 3T magnetic resonance angiography of the aorta, hepatic artery, portal vein, superior mesenteric artery, and the renal and common carotid arteries. In comparison to healthy volunteers, resting blood flow in the descending thoracic aorta was increased by 43% in patients with liver disease (4.31 ± 1.47 vs. 3.31 ± 0.80 L/min, P = 0.011). While portal vein flow was similar (0.83 ± 0.38 vs. 0.77 ± 0.35 L/min, P = 0.649), hepatic artery flow doubled (0.50 ± 0.46 vs. 0.25 ± 0.15 L/min, P = 0.021) and consequently total liver blood flow increased by 30% (1.33 ± 0.84 vs. 1.027 ± 0.5 L/min, P = 0.043). In patients with liver disease, superior mesenteric artery flow was threefold higher (0.65 ± 0.35 vs. 0.22 ± 0.13 L/min, P < 0.001), while total renal blood flow was reduced by 40% (0.37 ± 0.14 vs. 0.62 ± 0.22 L/min, P < 0.001) and total carotid blood flow unchanged (0.62 ± 0.20 vs. 0.65 ± 0.13 L/min, P = 0.315). Rather than a generalised systemic hyperdynamic circulation, liver disease is associated with dysregulated splanchnic vasodilatation and portosystemic shunting that, while inducing a high cardiac output, causes compensatory extra-splanchnic vasoconstriction - the 'splanchnic steal' phenomenon. These circulatory disturbances may underlie many of the manifestations of advanced liver disease.

  13. [Assessment of maternal cerebral blood flow in patients with preeclampsia].

    PubMed

    Mandić, Vesna; Miković, Zeljko; Dukić, Milan; Vasiljević, Mladenko; Filimonović, Dejan; Bogavac, Mirjana

    2005-01-01

    Systemic vasoconstriction in preeclamptic patients increases vascular resistance, and is manifested by increased arterial blood flow velocity. The aim of the study is to evaluate if there is a change of Doppler indices in maternal medial cerbral artery (MCA) in severe preeclampsia due to: 1) severity of clinical symptoms, 2) the begining of eclamptic attack and 3) the application of anticonvulsive therapy. A prospective clinical study included 92 pregnant women, gestational age 28-36 weeks. They were divided into three groups: normotensive (n=30), mild preeclampsia (n=33), and severe preeclampsia (n=29). We investigated maternal cerebral circulation by assessing the MCA. We registrated: pulsatility index (Pi), resistance index (Ri), systolic/diastolic ratio (S/D), and the maximum systolic, end diastolic and medium velocity. Patients with severe preeclampsia were divided into two subgroups. subgroup 1 included patients without symptoms of threatening eclampsia (n=18; 62.06%); while subgroup 2 included those with symptoms of preeclampsia (n=11; 37.94%). All patients with severe preeclampsia were treated with magnesium sulfate (MgSO4), and cerebral blood flow was measured before and after the treatment. Statistical analysis was done by oneway ANOVA, Student t-test and t-paired sample test. The difference was considered to be significant if p<0.05. Significantly increased Pi, Ri and all velocities were established in the group of patients with severe preeclampsia compared with the other two groups. In the group with severe preeclamsia we registrated significantly increased values of all velocities (patients with signs of threatening eclampsia). After MgSO4 treatment in patients with severe preeclampsia significantly decreased values of Pi, Ri, S/D ratio and all velocities were registered. In the studied group of patients with severe preclampsia we found increased velocity values, Pi and Ri, especially in patients with signs of threatened eclampsia, suggesting that

  14. Expiratory muscle loading increases intercostal muscle blood flow during leg exercise in healthy humans

    PubMed Central

    Athanasopoulos, Dimitris; Louvaris, Zafeiris; Cherouveim, Evgenia; Andrianopoulos, Vasilis; Roussos, Charis; Zakynthinos, Spyros

    2010-01-01

    We investigated whether expiratory muscle loading induced by the application of expiratory flow limitation (EFL) during exercise in healthy subjects causes a reduction in quadriceps muscle blood flow in favor of the blood flow to the intercostal muscles. We hypothesized that, during exercise with EFL quadriceps muscle blood flow would be reduced, whereas intercostal muscle blood flow would be increased compared with exercise without EFL. We initially performed an incremental exercise test on eight healthy male subjects with a Starling resistor in the expiratory line limiting expiratory flow to ∼ 1 l/s to determine peak EFL exercise workload. On a different day, two constant-load exercise trials were performed in a balanced ordering sequence, during which subjects exercised with or without EFL at peak EFL exercise workload for 6 min. Intercostal (probe over the 7th intercostal space) and vastus lateralis muscle blood flow index (BFI) was calculated by near-infrared spectroscopy using indocyanine green, whereas cardiac output (CO) was measured by an impedance cardiography technique. At exercise termination, CO and stroke volume were not significantly different during exercise, with or without EFL (CO: 16.5 vs. 15.2 l/min, stroke volume: 104 vs. 107 ml/beat). Quadriceps muscle BFI during exercise with EFL (5.4 nM/s) was significantly (P = 0.043) lower compared with exercise without EFL (7.6 nM/s), whereas intercostal muscle BFI during exercise with EFL (3.5 nM/s) was significantly (P = 0.021) greater compared with that recorded during control exercise (0.4 nM/s). In conclusion, increased respiratory muscle loading during exercise in healthy humans causes an increase in blood flow to the intercostal muscles and a concomitant decrease in quadriceps muscle blood flow. PMID:20507965

  15. Laser Speckle Contrast Imaging of Cerebral Blood Flow

    PubMed Central

    Dunn, Andrew K.

    2011-01-01

    Laser speckle contrast imaging (LSCI) has emerged over the past decade as a powerful, yet simple, method for imaging of blood flow dynamics in real time. The rapid adoption of LSCI for physiological studies is due to the relative ease and low cost of building an instrument as well as the ability to quantify blood flow changes with excellent spatial and temporal resolution. Although measurements are limited to superficial tissues with no depth resolution, LSCI has been instrumental in pre-clinical studies of neurological disorders as well as clinical applications including dermatological, neurosurgical and endoscopic studies. Recently a number of technical advances have been developed to improve the quantitative accuracy and temporal resolution of speckle imaging. This article reviews some of these recent advances and describes several applications of speckle imaging. PMID:22109805

  16. Laser Speckle Imaging of Blood Flow Beneath Static Scattering Media

    NASA Astrophysics Data System (ADS)

    Regan, Caitlin Anderson

    Laser speckle imaging (LSI) is a wide-field optical imaging technique that provides information about the movement of scattering particles in biological samples. LSI is used to create maps of relative blood flow and perfusion in samples such as the skin, brain, teeth, gingiva, and other biological tissues. The presence of static, or non-moving, optical scatterers affects the ability of LSI to provide true quantitative and spatially resolved measurements of blood flow. With in vitro experiments using tissue-simulating phantoms, we determined that temporal analysis of raw speckle image sequences improved the quantitative accuracy of LSI to measure flow beneath a static scattering layer. We then applied the temporal algorithm to assess the potential of LSI to monitor oral health. We designed and tested two generations of miniature LSI devices to measure flow in the pulpal chamber of teeth and in the gingiva. Our preliminary clinical pilot data indicated that speckle contrast may correlate with gingival health. To improve visualization of subsurface blood vessels, we developed a technique called photothermal LSI. We applied a short pulse of laser energy to selectively perturb the motion of red blood cells, increasing the signal from vasculature relative to the surroundings. To study the spectral and depth dependence of laser speckle contrast, we developed a Monte Carlo model of light and momentum transport to simulate speckle contrast. With an increase in the thickness of the overlying static-scattering layer, we observed a quadratic decrease in the quantity of dynamically scattered light collected by the detector. We next applied the model to study multi-exposure speckle imaging (MESI), a method that purportedly improves quantitative accuracy of subsurface blood flow measurements. We unexpectedly determined that MESI faced similar depth limitations as conventional LSI, findings that were supported by in vitro experimental data. Finally, we used the model to study the

  17. Infrared Imaging of Nitric Oxide-Mediated Blood Flow in Human Sickle Cell Disease

    PubMed Central

    Gorbach, Alexander M.; Ackerman, Hans C.; Liu, Wei-Min; Meyer, Joseph M.; Littel, Patricia L.; Seamon, Catherine; Footman, Eleni; Chi, Amy; Zorca, Suzana; Krajewski, Megan L.; Cuttica, Michael J.; Machado, Roberto F.; Cannon, Richard O.; Kato, Gregory J.

    2012-01-01

    Vascular dysfunction is an important pathophysiologic manifestation of sickle cell disease (SCD), a condition that increases risk of pulmonary hypertension and stroke. We hypothesized that infrared (IR) imaging would detect changes in cutaneous blood flow reflective of vascular function. We performed IR imaging and conventional strain gauge plethysmography in twenty-five adults with SCD at baseline and during intra-arterial infusions of an endothelium-dependent vasodilator acetylcholine (ACh), an endothelium-independent vasodilator sodium nitroprusside (SNP), and a NOS inhibitor L-NMMA. Skin temperature measured by IR imaging increased in a dose-dependent manner to graded infusions of ACh (+1.1° C, p < 0.0001) and SNP (+0.9° C, p < 0.0001), and correlated with dose-dependent increases in forearm blood flow (ACh: +19.9 mL/min/100mL, p < 0.0001; rs = 0.57, p = 0.003; SNP: +8.6 mL/min/100mL, p < 0.0001; r = 0.70, p = 0.0002). Although IR measurement of skin temperature accurately reflected agonist-induced increases in blood flow, it was less sensitive to decreases in blood flow caused by NOS inhibition. Baseline forearm skin temperature measured by IR imaging correlated significantly with baseline forearm blood flow (31.8±0.2° C, 6.0±0.4 mL/min/100mL; r = 0.58, p = 0.003), and appeared to represent a novel biomarker of vascular function. It predicted a blunted blood flow response to SNP (r = −0.61, p = 0.002), and was independently associated with a marker of pulmonary artery pressure, as well as hemoglobin level, diastolic blood pressure, homocysteine, and cholesterol (R2 = 0.84, p < 0.0001 for the model). IR imaging of agonist-stimulated cutaneous blood flow represents a less cumbersome alternative to plethysmography methodology. Measurement of baseline skin temperature by IR imaging may be a useful new marker of vascular risk in adults with SCD. PMID:22784510

  18. Shy-Drager syndrome. Effect of fludrocortisone and L-threo-3,4-dihydroxyphenylserine on the blood pressure and regional cerebral blood flow.

    PubMed Central

    Matsubara, S; Sawa, Y; Yokoji, H; Takamori, M

    1990-01-01

    In nine cases of Shy-Drager syndrome, the changes in blood pressure and cerebral blood flow on sitting up from a supine position were studied. The influence of fludrocortisone, a synthetic mineralocorticoid, and L-threo-3,4-dihydroxyphenylserine (DOPS), a precursor of norepinephrine, on these changes was examined. On sitting up, the regional cerebral blood flow (rCBF) measured by Xe133 inhalation showed a tendency to decrease. Fludrocortisone reduced the fall of the mean blood pressure significantly. DOPS reduced the fall of both the diastolic blood pressure and rCBF significantly. PMID:2283531

  19. [Impact of low level laser therapy on skin blood flow].

    PubMed

    Podogrodzki, Jacek; Lebiedowski, Michał; Szalecki, Mieczysław; Kępa, Izabela; Syczewska, Małgorzata; Jóźwiak, Sergiusz

    2016-01-01

    The aim of this study was to objectively assess the impact of low level laser therapy on skin blood flow, in terms of two of its components - the flow and trophic and therapeutic effect. Nineteen children aged 3-15 years have been included in the study (seven boys and twelve girls) with a diagnosis of meningomyelocele in the lumbosacral area. In nine of them (47.3%) bedsores were found in the area of paresis location. Studies of skin blood flow were performed using xenon 133 clearance in the Department of Nuclear Medicine of the Children's Memorial Health Institute. Xenon 133 radioisotope in saline with intrinsic activity 74 MBq in 1 ml was used as the marker. Laser application was performed immediately prior to the application of the marker with a tag shower 60 mW probe, emitting 680 nm red light with surface power density of 0.5 J/cm2. Within the tested children the laser application resulted in a significantly increased skin blood flow. Average results in tested group before LLLT are 7.47 ml/100 g/min, after LLLT 11.08 ml/100 g/min. 1. LLLT significantly increases the perfusion of the skin. 2. The effect of the increased perfusion as the result of laserotherapy in the most evident in children with skin trophic abnormalities. 3. Results confirmed by clinical observation indicate, that perfusion increase in relation to LLLT takes place with participation of trophic component of skin blood circulation.

  20. Myocardial blood flow: Roentgen videodensitometry techniques

    NASA Technical Reports Server (NTRS)

    Smith, H. C.; Robb, R. A.; Wood, E. H.

    1975-01-01

    The current status of roentgen videodensitometric techniques that provide an objective assessment of blood flow at selected sites within the coronary circulation were described. Roentgen videodensitometry employs conventional radiopaque indicators, radiological equipment and coronary angiographic techniques. Roentgen videodensitometry techniques developed in the laboratory during the past nine years, and for the past three years were applied to analysis of angiograms in the clinical cardiac catheterization laboratory.

  1. Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans

    PubMed Central

    Ichinose-Kuwahara, Tomoko; Kondo, Narihiko; Nishiyasu, Takeshi

    2015-01-01

    Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity. PMID:26377556

  2. Vaginal blood flow after radical hysterectomy with and without nerve sparing. A preliminary report.

    PubMed

    Pieterse, Q D; Ter Kuile, M M; Deruiter, M C; Trimbos, J B M Z; Kenter, G G; Maas, C P

    2008-01-01

    Radical hysterectomy with pelvic lymphadenectomy (RHL) for cervical cancer causes damage to the autonomic nerves, which are responsible for increased vaginal blood flow during sexual arousal. The aim of the study of which we now report preliminary data was to determine whether a nerve-sparing technique leads to an objectively less disturbed vaginal blood flow response during sexual stimulation. Photoplethysmographic assessment of vaginal pulse amplitude (VPA) during sexual stimulation by erotic films was performed. Subjective sexual arousal was assessed after each stimulus. Thirteen women after conventional RHL, 10 women after nerve-sparing RHL, and 14 healthy premenopausal women participated. Data were collected between January and August 2006. The main outcome measure was the logarithmically transformed mean VPA. To detect statistically significant differences in mean VPA levels between the three groups, a univariate analysis of variance was used. Mean VPA differed between the three groups (P= 0.014). The conventional group had a lower vaginal blood flow response than the control group (P= 0.016), which tended also to be lower than that of the nerve-sparing group (P= 0.097). These differences were critically dependent on baseline vaginal blood flow differences between the groups. The conventional group follows a vaginal blood flow pattern similar to postmenopausal women. Conventional RHL is associated with an overall disturbed vaginal blood flow response compared with healthy controls. Because it is not observed to the same extent after nerve-sparing RHL, it seems that the nerve-sparing technique leads to a better overall vaginal blood flow caused by less denervation of the vagina.

  3. Endoscopical determination of gastric mucosal blood flow by the crossed thermocouple method.

    PubMed

    Hiramatsu, A; Watanabe, T; Okuhira, M; Uchiyama, S; Mizuno, T; Sameshima, Y

    1984-06-01

    A crossed thermocouple method in combination with endoscopy was applied to determine the blood flow rate of the human gastric mucosa. Determination was carried out with 11 healthy control subjects at 8 sites of the stomach. The blood flow rates at all sites in the corpus were found to be higher than those at the antrum. In subjects less than 50 years old the blood flow rate in the corpus was higher than in older subjects. These results were in agreed well with those obtained by the hydrogen gas clearance method, which is widely adopted clinically. The crossed thermocouple method is easily applicable to all sites in the gastric mucosa and the time required for the assay is very short. This method dose not require the inhalation of hydrogen gas which is necessary for the hydrogen gas clearance method and which is possibly harmful to humans. Although the values obtained by the crossed thermocouple method are relative to the value at a certain fixed site, this method will holds great potential for the determination of gastric mucosal blood flow rate.

  4. Direct numerical simulation of cellular-scale blood flow in microvascular networks

    NASA Astrophysics Data System (ADS)

    Balogh, Peter; Bagchi, Prosenjit

    2017-11-01

    A direct numerical simulation method is developed to study cellular-scale blood flow in physiologically realistic microvascular networks that are constructed in silico following published in vivo images and data, and are comprised of bifurcating, merging, and winding vessels. The model resolves large deformation of individual red blood cells (RBC) flowing in such complex networks. The vascular walls and deformable interfaces of the RBCs are modeled using the immersed-boundary methods. Time-averaged hemodynamic quantities obtained from the simulations agree quite well with published in vivo data. Our simulations reveal that in several vessels the flow rates and pressure drops could be negatively correlated. The flow resistance and hematocrit are also found to be negatively correlated in some vessels. These observations suggest a deviation from the classical Poiseuille's law in such vessels. The cells are observed to frequently jam at vascular bifurcations resulting in reductions in hematocrit and flow rate in the daughter and mother vessels. We find that RBC jamming results in several orders of magnitude increase in hemodynamic resistance, and thus provides an additional mechanism of increased in vivo blood viscosity as compared to that determined in vitro. Funded by NSF CBET 1604308.

  5. Retinal blood flow in type 1 diabetic patients with no or mild diabetic retinopathy during euglycemic clamp.

    PubMed

    Pemp, Berthold; Polska, Elzbieta; Garhofer, Gerhard; Bayerle-Eder, Michaela; Kautzky-Willer, Alexandra; Schmetterer, Leopold

    2010-09-01

    To compare total retinal blood flow in diabetic patients with no or mild nonproliferative diabetic retinopathy and healthy control subjects and to investigate in patients whether there is a difference between retinal blood flow before morning insulin and under normoglycemic conditions using a glucose clamp. Twenty patients with type 1 diabetes with no or mild diabetic retinopathy were included in this open parallel-group study, and 20 healthy age- and sex-matched subjects were included as control subjects. Retinal blood flow was assessed by combining velocity measurements using laser Doppler velocimetry and diameter measurements using a commercially available dynamic vessel analyzer. Measurements were performed before and during a euglycemic clamp. Total retinal blood flow was higher in diabetic patients (53 +/- 16 microl/min) than in healthy subjects (43 +/- 16 microl/min; P = 0.034 between groups). When plasma glucose in diabetic patients was reduced from 9.3 +/- 1.7 to 5.3 +/- 0.5 mmol/l (P < 0.001) retinal blood flow decreased to 49 +/- 15 microl/min (P = 0.0003 vs. baseline). Total retinal blood flow during the glucose clamp was not significantly different from blood flow in normal control subjects (P = 0.161). Type 1 diabetic patients with no or only mild diabetic retinopathy have increased retinal blood flow before their morning insulin dosage. Blood flow is reduced toward normal during euglycemic conditions. Retinal blood flow may fluctuate significantly with fluctuating plasma glucose levels, which may contribute to the microvascular changes seen in diabetic retinopathy.

  6. Direct Numerical Simulation of Cellular-Scale Blood Flow in 3D Microvascular Networks.

    PubMed

    Balogh, Peter; Bagchi, Prosenjit

    2017-12-19

    We present, to our knowledge, the first direct numerical simulation of 3D cellular-scale blood flow in physiologically realistic microvascular networks. The vascular networks are designed following in vivo images and data, and are comprised of bifurcating, merging, and winding vessels. Our model resolves the large deformation and dynamics of each individual red blood cell flowing through the networks with high fidelity, while simultaneously retaining the highly complex geometric details of the vascular architecture. To our knowledge, our simulations predict several novel and unexpected phenomena. We show that heterogeneity in hemodynamic quantities, which is a hallmark of microvascular blood flow, appears both in space and time, and that the temporal heterogeneity is more severe than its spatial counterpart. The cells are observed to frequently jam at vascular bifurcations resulting in reductions in hematocrit and flow rate in the daughter and mother vessels. We find that red blood cell jamming at vascular bifurcations results in several orders-of-magnitude increase in hemodynamic resistance, and thus provides an additional mechanism of increased in vivo blood viscosity as compared to that determined in vitro. A striking result from our simulations is negative pressure-flow correlations observed in several vessels, implying a significant deviation from Poiseuille's law. Furthermore, negative correlations between vascular resistance and hematocrit are observed in various vessels, also defying a major principle of particulate suspension flow. To our knowledge, these novel findings are absent in blood flow in straight tubes, and they underscore the importance of considering realistic physiological geometry and resolved cellular interactions in modeling microvascular hemodynamics. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  7. Advanced Recording and Preprocessing of Physiological Signals. [data processing equipment for flow measurement of blood flow by ultrasonics

    NASA Technical Reports Server (NTRS)

    Bentley, P. B.

    1975-01-01

    The measurement of the volume flow-rate of blood in an artery or vein requires both an estimate of the flow velocity and its spatial distribution and the corresponding cross-sectional area. Transcutaneous measurements of these parameters can be performed using ultrasonic techniques that are analogous to the measurement of moving objects by use of a radar. Modern digital data recording and preprocessing methods were applied to the measurement of blood-flow velocity by means of the CW Doppler ultrasonic technique. Only the average flow velocity was measured and no distribution or size information was obtained. Evaluations of current flowmeter design and performance, ultrasonic transducer fabrication methods, and other related items are given. The main thrust was the development of effective data-handling and processing methods by application of modern digital techniques. The evaluation resulted in useful improvements in both the flowmeter instrumentation and the ultrasonic transducers. Effective digital processing algorithms that provided enhanced blood-flow measurement accuracy and sensitivity were developed. Block diagrams illustrative of the equipment setup are included.

  8. Rotating permanent magnet excitation for blood flow measurement.

    PubMed

    Nair, Sarath S; Vinodkumar, V; Sreedevi, V; Nagesh, D S

    2015-11-01

    A compact, portable and improved blood flow measurement system for an extracorporeal circuit having a rotating permanent magnetic excitation scheme is described in this paper. The system consists of a set of permanent magnets rotating near blood or any conductive fluid to create high-intensity alternating magnetic field in it and inducing a sinusoidal varying voltage across the column of fluid. The induced voltage signal is acquired, conditioned and processed to determine its flow rate. Performance analysis shows that a sensitivity of more than 250 mV/lpm can be obtained, which is more than five times higher than conventional flow measurement systems. Choice of rotating permanent magnet instead of an electromagnetic core generates alternate magnetic field of smooth sinusoidal nature which in turn reduces switching and interference noises. These results in reduction in complex electronic circuitry required for processing the signal to a great extent and enable the flow measuring device to be much less costlier, portable and light weight. The signal remains steady even with changes in environmental conditions and has an accuracy of greater than 95%. This paper also describes the construction details of the prototype, the factors affecting sensitivity and detailed performance analysis at various operating conditions.

  9. 1-D blood flow modelling in a running human body.

    PubMed

    Szabó, Viktor; Halász, Gábor

    2017-07-01

    In this paper an attempt was made to simulate blood flow in a mobile human arterial network, specifically, in a running human subject. In order to simulate the effect of motion, a previously published immobile 1-D model was modified by including an inertial force term into the momentum equation. To calculate inertial force, gait analysis was performed at different levels of speed. Our results show that motion has a significant effect on the amplitudes of the blood pressure and flow rate but the average values are not effected significantly.

  10. Relationship between retinal blood flow and arterial oxygen.

    PubMed

    Cheng, Richard W; Yusof, Firdaus; Tsui, Edmund; Jong, Monica; Duffin, James; Flanagan, John G; Fisher, Joseph A; Hudson, Chris

    2016-02-01

    Vascular reactivity, the response of the vessels to a vasoactive stimulus such as hypoxia and hyperoxia, can be used to assess the vascular range of adjustment in which the vessels are able to compensate for changes in PO2. Previous studies in the retina have not accurately quantified retinal vascular responses and precisely targeted multiple PaO2 stimuli at the same time as controlling the level of carbon dioxide, thus precluding them from modelling the relationship between retinal blood flow and oxygen. The present study modelled the relationship between retinal blood flow and PaO2, showing them to be a combined linear and hyperbolic function. This model demonstrates that the resting tonus of the vessels is at the mid-point and that they have great vascular range of adjustment, compensating for decreases in oxygen above a PETCO2 of 32-37 mmHg but being limited below this threshold. Retinal blood flow (RBF) increases in response to a reduction in oxygen (hypoxia) but decreases in response to increased oxygen (hyperoxia). However, the relationship between blood flow and the arterial partial pressure of oxygen has not been quantified and modelled in the retina, particularly in the vascular reserve and resting tonus of the vessels. The present study aimed to determine the limitations of the retinal vasculature by modelling the relationship between RBF and oxygen. Retinal vascular responses were measured in 13 subjects for eight different blood gas conditions, with the end-tidal partial pressure of oxygen (PETCO2) ranging from 40-500 mmHg. Retinal vascular response measurements were repeated twice; using the Canon laser blood flowmeter (Canon Inc., Tokyo, Japan) during the first visit and using Doppler spectral domain optical coherence tomography during the second visit. We determined that the relationship between RBF and PaO2 can be modelled as a combination of hyperbolic and linear functions. We concluded that RBF compensated for decreases in arterial oxygen content

  11. Multimodal Pressure-Flow Analysis: Application of Hilbert Huang Transform in Cerebral Blood Flow Regulation

    NASA Astrophysics Data System (ADS)

    Lo, Men-Tzung; Hu, Kun; Liu, Yanhui; Peng, C.-K.; Novak, Vera

    2008-12-01

    Quantification of nonlinear interactions between two nonstationary signals presents a computational challenge in different research fields, especially for assessments of physiological systems. Traditional approaches that are based on theories of stationary signals cannot resolve nonstationarity-related issues and, thus, cannot reliably assess nonlinear interactions in physiological systems. In this review we discuss a new technique called multimodal pressure flow (MMPF) method that utilizes Hilbert-Huang transformation to quantify interaction between nonstationary cerebral blood flow velocity (BFV) and blood pressure (BP) for the assessment of dynamic cerebral autoregulation (CA). CA is an important mechanism responsible for controlling cerebral blood flow in responses to fluctuations in systemic BP within a few heart-beats. The MMPF analysis decomposes BP and BFV signals into multiple empirical modes adaptively so that the fluctuations caused by a specific physiologic process can be represented in a corresponding empirical mode. Using this technique, we showed that dynamic CA can be characterized by specific phase delays between the decomposed BP and BFV oscillations, and that the phase shifts are significantly reduced in hypertensive, diabetics and stroke subjects with impaired CA. Additionally, the new technique can reliably assess CA using both induced BP/BFV oscillations during clinical tests and spontaneous BP/BFV fluctuations during resting conditions.

  12. Effects of exercise and heat stress on regional blood flow in pregnant sheep.

    PubMed

    Bell, A W; Hales, J R; Fawcett, A A; King, R B

    1986-05-01

    Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues, including those in the pregnant uterus, in late-pregnant ewes at rest and during treadmill exercise (approximately 3-fold increase in metabolic rate for 30 min) in thermoneutral (TN) (dry bulb temperature (Tdb) = 13 degrees C, wet bulb temperature (Twb) = 10 degrees C) and mildly hot (MH) (Tdb = 40 degrees C, Twb = 27 degrees C) environments. Exercise caused major increases in blood flow to respiratory muscles, nonrespiratory limb muscles, and adipose tissue, and flow was decreased to some gastrointestinal tissues, spleen, pancreas, and to placental and nonplacental tissues in the pregnant uterus. Heat exposure had relatively little effect on these exercise-induced changes, except that flow was further increased in the respiratory muscles. Results are compared with those of a similar study on nonpregnant sheep in which changes in muscle, skin, and visceral flows during exercise were attenuated by heat exposure. It is suggested that redistribution of blood flow from the pregnant uterus, which in resting ewes took 22% of cardiac output, is a significant buffer against the potentially deleterious effects of combined exercise and heat stress on blood flow to exercising muscles and thermoregulatory tissues.

  13. Effects of Nitroglycerin on Regional Myocardial Blood Flow in Coronary Artery Disease

    PubMed Central

    Horwitz, Lawrence D.; Gorlin, Richard; Taylor, Warren J.; Kemp, Harvey G.

    1971-01-01

    Regional myocardial blood flow before and after sublingual nitroglycerin was measured in 10 patients with coronary artery disease. During thoracotomy, 133Xe was injected directly into the subepicardium in diseased regions of the anterior left ventricular wall, and washout rates were recorded with a scintillation counter. All disappearance curves were closely approximated by two exponential decays analyzed as two parallel flow systems by the compartmental method. The appearance of a double exponential decay pattern in diseased regions suggests that the slow phase was associated with collateral blood flow, although nonhomogeneous myocardium-to-blood partition coefficients for xenon cannot be excluded. Nitroglycerin increased the rapid phase flow in 9 of 10 patients and the slow flow in 7 of 10 patients. Average flow increased in 9 of the 10 patients (P < 0.01). Mean rapid phase flow in the control state was 110 ml/100 g per min and after nitroglycerin increased to 132 ml/100 g per min (P < 0.01); slow phase flow increased from 12 ml/100 g per min to 15 ml/100 g per min (P < 0.05). It is concluded that, under these conditions, nitroglycerin improves perfusion in regions of diseased myocardium in patients with coronary artery disease. PMID:4999635

  14. [Antegrade diastolic blood flow and classic reflux in varicose dilatation of the intersaphenous vein].

    PubMed

    Shaidakov, E V; Rosukhovsky, D A; Grigoryan, A G; Bulatov, V L; Ilyukhin, E A

    2016-01-01

    In the intersaphenous vein (ISV) there may take place the so-called "antegrade" or "paradoxical" reflux. This type of blood flow is revealed in a series of patients during muscular diastole and is a link of the pathogenesis of varicose disease, but has, as distinct from the "classical" reflux, an antegrade direction. An incompetent saphenopopliteal junction (SPJ) is a source of the antegrade diastolic blood flow (ADBF) through the ISV. Descriptions of possible variants of impaired blood flow through the ISV are fragmentary and their interpretations are controversial. Prevalence and pathogenesis of these disorders impairments have not yet been studied. A cross-sectional study: over 4 years three centres examined a total of 1,413 patients diagnosed with class C2-C6 varicose veins according the CEAP classification. All patients underwent ultrasound duplex scanning of lower limb veins. The ADBF was determined as a unidirectional antegrade blood flow with the duration of not more than 0.5 second, observed after the crus was relived of compression (in the diastole). Of the patients included into the study who had no varicose veins on the contralateral extremity with the ISV being spotted we sequentially selected 40 subjects including them into the Study Group for the analysis of blood flow and the diameter of the ISV in health. Impairments of blood flow in the ISV were revealed in 61 (4.8%) of 1,265 extremities included into the study: the "classical" reflux in 9 (14.8%) limbs, ADBF was revealed in 37 (60.7%) limbs, a combination of the "classical" blood flow and ADBF - in 15 (24.6%) limbs. Hence, the patients were subdivided into three groups. Studying the nature of blood flow through the ISV in the control group on 40 lower limbs revealed no blood flow disorders. The mean ISV diameter amounted to 1.68 mm (ME=1 mm). The ISV diameter was considerably higher in all studied groups as compared with the control one (p<0.0001). The diameter of the ISV in its proximal portion

  15. Estimating mechanical blood trauma in a centrifugal blood pump: laser Doppler anemometer measurements of the mean velocity field.

    PubMed

    Pinotti, M; Paone, N

    1996-06-01

    A laser Doppler anemometer (LDA) was used to obtain the mean velocity and the Reynolds stress fields in the inner channels of a well-known centrifugal vaneless pump (Bio-pump). Effects of the excessive flow resistance against which an occlusive pump operates in some surgical situations, such as cardiopulmonary bypass, are illustrated. The velocity vector field obtained from LDA measurements reveals that the constraint-forced vortex provides pumping action in a restricted area in the core of the pump. In such situations, recirculating zones dominate the flow and consequently increase the damage to blood cells and raise the risk of thrombus formation in the device. Reynolds normal and shear stress fields were obtained in the entry flow for the channel formed by two rotating cones to illustrate the effects of flow disturbances on the potential for blood cell damage.

  16. Localization of Short-Chain Polyphosphate Enhances its Ability to Clot Flowing Blood Plasma

    NASA Astrophysics Data System (ADS)

    Yeon, Ju Hun; Mazinani, Nima; Schlappi, Travis S.; Chan, Karen Y. T.; Baylis, James R.; Smith, Stephanie A.; Donovan, Alexander J.; Kudela, Damien; Stucky, Galen D.; Liu, Ying; Morrissey, James H.; Kastrup, Christian J.

    2017-02-01

    Short-chain polyphosphate (polyP) is released from platelets upon platelet activation, but it is not clear if it contributes to thrombosis. PolyP has increased propensity to clot blood with increased polymer length and when localized onto particles, but it is unknown whether spatial localization of short-chain polyP can accelerate clotting of flowing blood. Here, numerical simulations predicted the effect of localization of polyP on clotting under flow, and this was tested in vitro using microfluidics. Synthetic polyP was more effective at triggering clotting of flowing blood plasma when localized on a surface than when solubilized in solution or when localized as nanoparticles, accelerating clotting at 10-200 fold lower concentrations, particularly at low to sub-physiological shear rates typical of where thrombosis occurs in large veins or valves. Thus, sub-micromolar concentrations of short-chain polyP can accelerate clotting of flowing blood plasma under flow at low to sub-physiological shear rates. However, a physiological mechanism for the localization of polyP to platelet or vascular surfaces remains unknown.

  17. Modelling the Transport of Nanoparticles under Blood Flow using an Agent-based Approach.

    PubMed

    Fullstone, Gavin; Wood, Jonathan; Holcombe, Mike; Battaglia, Giuseppe

    2015-06-10

    Blood-mediated nanoparticle delivery is a new and growing field in the development of therapeutics and diagnostics. Nanoparticle properties such as size, shape and surface chemistry can be controlled to improve their performance in biological systems. This enables modulation of immune system interactions, blood clearance profile and interaction with target cells, thereby aiding effective delivery of cargo within cells or tissues. Their ability to target and enter tissues from the blood is highly dependent on their behaviour under blood flow. Here we have produced an agent-based model of nanoparticle behaviour under blood flow in capillaries. We demonstrate that red blood cells are highly important for effective nanoparticle distribution within capillaries. Furthermore, we use this model to demonstrate how nanoparticle size can selectively target tumour tissue over normal tissue. We demonstrate that the polydispersity of nanoparticle populations is an important consideration in achieving optimal specificity and to avoid off-target effects. In future this model could be used for informing new nanoparticle design and to predict general and specific uptake properties under blood flow.

  18. The effects of non-Newtonian blood flow on curved stenotic coronary artery

    NASA Astrophysics Data System (ADS)

    Li, Shuang; Chin, Cheng; Monty, Jason; Barlis, Peter; Ooi, Andrew

    2017-11-01

    Direct numerical simulations (DNS) are carried out using both Newtonian and non-Newtonian viscosity models under a pulsatile physiological flow condition to study the influences of the non-Newtonian blood property on the flow fields in the idealised curved stenotic artery model. Quemada model is adopted to simulate the non-Newtonian blood in the simulations. Both time-averaged and selected instantaneous velocity, vorticity and pressure data are examined and the differences between the Newtonian and non-Newtonian flows are examined. The non-Newtonian simulations tend to have blunted axial velocity profile compared to the Newtonian cases. In the proximal of post-stenotic region, smaller recirculation bubbles are observed because of the non-Newtonian effects. Decreased secondary flow strengths are observed upstream of stenosis while higher magnitudes of secondary flows are found out downstream of stenosis. The deviation of mean cross-sectionally axial vorticity is minimal except at the peak systole, where an additional vortice appears near the centre of the 90 degrees plane that is more pronounced in the Newtonian case. The influence of blood-analog viscosity increases the mean pressure drops. However, lower instantaneous pressure losses at peak systole are observed in contrast to the Newtonian blood analog fluid.

  19. Feed artery role in blood flow control to rat hindlimb skeletal muscles.

    PubMed Central

    Williams, D A; Segal, S S

    1993-01-01

    1. Vasomotor tone and reactivity were investigated in feed arteries of the extensor digitorum longus and soleus muscles. Feed arteries are located external to the muscle and give rise to the microcirculation within each muscle. Resting diameter was smaller in feed arteries of the soleus muscle. 2. Feed arteries of both muscles dilated to similar peak values with sodium nitroprusside. 3. Micropressure measurements demonstrated resistance to blood flow in the feed arteries supplying both muscles. Feed arteries supplying soleus muscle demonstrated greater resistance to blood flow compared to feed arteries of extensor digitorum longus muscle. 4. Greater resting tone and larger pressure drop for feed arteries of soleus muscle suggest greater range of flow control compared to feed arteries of extensor digitorum longus muscle. 5. In both muscles, feed artery diameter increased with muscle contraction (functional dilatation) and in response to transient ischaemia (reactive dilatation). The magnitude of these responses varied between muscles. 6. Feed arteries are active sites of blood flow control in extensor digitorum longus and soleus muscles of the rat. These muscles differ in fibre type and recruitment properties. Differences in feed artery reactivity may contribute to differences in blood flow between these muscles observed at rest and during exercise. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8246199

  20. Smart catheter flow sensor for real-time continuous regional cerebral blood flow monitoring

    NASA Astrophysics Data System (ADS)

    Li, Chunyan; Wu, Pei-Ming; Hartings, Jed A.; Wu, Zhizhen; Ahn, Chong H.; LeDoux, David; Shutter, Lori A.; Narayan, Raj K.

    2011-12-01

    We present a smart catheter flow sensor for real-time, continuous, and quantitative measurement of regional cerebral blood flow using in situ temperature and thermal conductivity compensation. The flow sensor operates in a constant-temperature mode and employs a periodic heating and cooling technique. This approach ensures zero drift and provides highly reliable data with microelectromechanical system-based thin film sensors. The developed flow sensor has a sensitivity of 0.973 mV/ml/100 g/min in the range from 0 to 160 ml/100 g/min with a linear correlation coefficient of R2 = 0.9953. It achieves a resolution of 0.25 ml/100 g/min and an accuracy better than 5 ml/100 g/min.

  1. Oral Administration of Cilostazol Increases Ocular Blood Flow in Patients with Diabetic Retinopathy.

    PubMed

    Hwang, Duck Jin; Shin, Joo Young; Yu, Hyeong Gon

    2017-04-01

    To investigate the effect of cilostazol on ocular hemodynamics and to determine whether the administration of cilostazol increases the ocular blood flow in patients with diabetic retinopathy. This prospective observational study investigated the effect of orally administered cilostazol on diabetic retinopathy. Before and after administration for 1 week, pulsatile ocular blood flow (POBF) and retrobulbar hemodynamics were measured using a POBF analyzer and transcranial Doppler imaging, respectively. Visual acuity, intraocular pressure, and blood pressure were also evaluated before and after treatment. Twenty-five eyes of 25 patients were included in this study. POBF increased significantly (16.8 ± 4.6 µL/sec vs. 19.6 ± 6.2 µL/sec, p < 0.001) after administration of cilostazol, while no significant change was identified in visual acuity, intraocular pressure, and blood pressure. Mean flow velocity in the ophthalmic artery as measured with transcranial Doppler imaging also increased significantly after medication (23.5 ± 5.6 cm/sec vs. 26.0 ± 6.9 cm/sec, p = 0.001). The change in POBF directly correlated with the change in mean flow velocity (r = 0.419, p = 0.007). Cilostazol was effective in increasing ocular blood flow in patients with diabetic retinopathy, possibly by modulating retrobulbar circulation.

  2. Effects of chewing rate and reactive hyperemia on blood flow in denture-supporting mucosa during simulated chewing.

    PubMed

    Ogino, Takamichi; Ueda, Takayuki; Ogami, Koichiro; Koike, Takashi; Sakurai, Kaoru

    2017-01-01

    We examined how chewing rate and the extent of reactive hyperemia affect the blood flow in denture-supporting mucosa during chewing. The left palatal mucosa was loaded under conditions of simulated chewing or simulated clenching for 30s, and the blood flow during loading was recorded. We compared the relative blood flow during loading under conditions that recreated different chewing rates by combining duration of chewing cycle (DCC) and occlusal time (OT): fast chewing group, typical chewing group, slow chewing group and clenching group. The relationship between relative blood flow during simulated chewing and the extent of reactive hyperemia was also analyzed. When comparing the different chewing rate, the relative blood flow was highest in fast chewing rate, followed by typical chewing rate and slow chewing rate. Accordingly, we suggest that fast chewing increases the blood flow more than typical chewing or slow chewing. There was a significant correlation between the amount of blood flow during simulated chewing and the extent of reactive hyperemia. Within the limitations of this study, we concluded that slow chewing induced less blood flow than typical or fast chewing in denture-supporting mucosa and that people with less reactive hyperemia had less blood flow in denture-supporting mucosa during chewing. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  3. Blood flow velocity measurements in chicken embryo vascular network via PIV approach

    NASA Astrophysics Data System (ADS)

    Kurochkin, Maxim A.; Stiukhina, Elena S.; Fedosov, Ivan V.; Tuchin, Valery V.

    2018-04-01

    A method for measuring of blood velocity in the native vasculature of a chick embryo by the method of micro anemometry from particle images (μPIV) is improved. A method for interrogation regions sorting by the mask of the vasculature is proposed. A method for sorting of the velocity field of capillary blood flow is implemented. The in vitro method was evaluated for accuracy in a glass phantom of a blood vessel with a diameter of 50 μm and in vivo on the bloodstream of a chicken embryo, by comparing the transverse profile of the blood velocity obtained by the PIV method with the theoretical Poiseuille laminar flow profile.

  4. Changes of jugular venous blood temperature associated with measurements of cerebral blood flow using the transcerebral double-indicator dilution technique.

    PubMed

    Mielck, F; Bräuer, A; Radke, O; Hanekop, G; Loesch, S; Friedrich, M; Hilgers, R; Sonntag, H

    2004-04-01

    The transcerebral double-indicator dilution technique is a recently developed method to measure global cerebral blood flow at bedside. It is based on bolus injection of ice-cold indocyanine green dye and simultaneous recording of resulting thermo- and dye-dilution curves in the aorta and the jugular bulb. However, with this method 40 mL of ice-cold solution is administered as a bolus. Therefore, this prospective clinical study was performed to elucidate the effects of repeated administration of indicator on absolute blood temperature and on cerebral blood flow and metabolism. The investigation was performed in nine male patients scheduled for elective coronary artery bypass grafting. Absolute blood temperature was measured in the jugular bulb and in the aorta before and after repeated measurements using the transcerebral double-indicator dilution technique. During the investigated time course, the blood temperature in the jugular bulb, compared to the aorta, was significantly higher with a mean difference of 0.21 degrees C. The administration of an ice-cold bolus reduced the mean blood temperature by 0.06 degrees C in the jugular bulb as well as in the aorta. After the transcerebral double-indicator dilution measurements a temperature recovery to baseline conditions was not observed during the investigated time period. Cerebral blood flow and cerebral metabolism did not change during the investigated time period. Repeated measurements with the transcerebral double-indicator dilution technique do not affect absolute jugular bulb blood temperatures negatively. Global cerebral blood flow and metabolism measurements remain unaltered. However, accuracy and resolution of this technique is not high enough to detect the effect of minor changes of physiological variables.

  5. Genetic structure of eelgrass Zostera marina meadows in an embayment with restricted water flow

    USGS Publications Warehouse

    Munoz-Salazar, R.; Talbot, S.L.; Sage, G.K.; Ward, D.H.; Cabello-Pasini, Alejandro

    2006-01-01

    Genetic structure of the seagrass Zostera marina in a coastal lagoon with restricted water flow, and with heterogeneous water residence times and oceanographic characteristics, was assessed using 8 polymorphic microsatellite loci. Analyses of genetic differentiation (??) and Bayesian clustering suggested that the Z. marina population in San Quintin Bay (SQB) is genetically substructured, with at least 4 genetically different groups: (1) West Head, (2) Mouth, (3) East Arm, and (4) East Head. The greatest ?? value was observed between the most distant sites (?? = 0.095). The lowest values were found among sites closest to the mouth of the coastal lagoon (?? = 0.000 to 0.009). The maximum likelihood approach showed that the sites at the mouth have a mixed pattern of gene flow without a unidirectional pattern. In contrast, there was a clear pattern of asymmetrical gene flow from the mouth towards the West Head. These results suggested that the restriction of water flow at the heads, current pattern, and the distance between sites can reduce genetic flow and promote genetic differences within Z. marina meadows in small water embayments such as SQB. Though the population is genetically substructured and a 14 % decline in cover has been detected, this study did not show evidence of a recent genetic bottleneck. In contrast, mouth sites have experienced a recent expansion in their population size, and also perhaps a recent influx of rare alleles from genetically distinct immigrants. ?? Inter-Research 2006.

  6. Blood flow measurement of human skeletal muscle during various exercise intensity using diffuse correlation spectroscopy (DCS)

    NASA Astrophysics Data System (ADS)

    Murakami, Yuya; Ono, Yumie; Ichinose, Masashi

    2017-02-01

    We studied blood flow dynamics of active skeletal muscle using diffuse correlation spectroscopy (DCS), an emerging optical modality that is suitable for noninvasive quantification of microcirculation level in deep tissue. Seven healthy subjects conducted 0.5 Hz dynamic handgrip exercise for 3 minutes at intensities of 10, 20, 30, and 50 % of maximal voluntary contraction (MVC). DCS could detect the time-dependent increase of the blood flow response of the forearm muscle for continuous exercises, and the increase ratios of the mean blood flow through the exercise periods showed good correlation with the exercise intensities. We also compared blood flow responses detected from DCS with two different photon sampling rates and found that an appropriate photon sampling rates should be selected to follow the wide-ranged increase in the muscle blood flow with dynamic exercise. Our results demonstrate the possibility for utilizing DCS in a field of sports medicine to noninvasively evaluate the dynamics of blood flow in the active muscles.

  7. Simulation of Local Blood Flow in Human Brain under Altered Gravity

    NASA Technical Reports Server (NTRS)

    Kim, Chang Sung; Kiris, Cetin; Kwak, Dochan

    2003-01-01

    In addition to the altered gravitational forces, specific shapes and connections of arteries in the brain vary in the human population (Cebral et al., 2000; Ferrandez et al., 2002). Considering the geometric variations, pulsatile unsteadiness, and moving walls, computational approach in analyzing altered blood circulation will offer an economical alternative to experiments. This paper presents a computational approach for modeling the local blood flow through the human brain under altered gravity. This computational approach has been verified through steady and unsteady experimental measurements and then applied to the unsteady blood flows through a carotid bifurcation model and an idealized Circle of Willis (COW) configuration under altered gravity conditions.

  8. Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans.

    PubMed

    Ichinose, Masashi; Ichinose-Kuwahara, Tomoko; Kondo, Narihiko; Nishiyasu, Takeshi

    2015-11-15

    Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity. Copyright © 2015 the American Physiological Society.

  9. Ergot alkaloids decrease rumen epithelial blood flow

    USDA-ARS?s Scientific Manuscript database

    Two experiments were conducted to determine if ergot alkaloids affect blood flow to the absorptive surface of the rumen of steers. Steers (n=8 total) were pair-fed alfalfa cubes at 1.5× NEM and received ground endophyte-infected tall fescue seed (E+) or endophyte-free tall fescue seed (E-) via rumen...

  10. Effect of aminophylline on hindlimb blood flow autoregulation during increased metabolism in dogs.

    PubMed

    Metting, P J; Weldy, D L; Ronau, T F; Britton, S L

    1986-06-01

    The contribution of adenosine to hindlimb blood flow autoregulation during treadmill exercise or the administration of 2,4-dinitrophenol (DNP) was evaluated in 9 conscious dogs by determining hindlimb vascular bed pressure-flow relationships in the presence and absence of the adenosine receptor site antagonist, aminophylline. Hindlimb pressure-flow relationships were obtained by measuring blood flow during stepwise reductions in perfusion pressure produced with an occlusion cuff located distal to a flow probe on the external iliac artery. The efficiency of autoregulation was quantitated by calculating the closed-loop gain of flow regulation (Gc) at each pressure decrement utilizing the equation Gc = 1 - (% delta flow/% delta pressure). A Gc of one represents perfect autoregulation of flow, and a Gc of zero is indicative of a rigid system. During exercise, Gc averaged 0.44 +/- 0.07. Aminophylline reduced the Gc during exercise to -0.07 +/- 0.06 (P less than 0.05). During DNP administration, Gc averaged 0.54 +/- 0.09 and declined to -0.09 +/- 0.10 in the presence of aminophylline (P less than 0.05). These results support the hypothesis that adenosine is a primary mediator of hindlimb blood flow autoregulation during conditions that increase hindlimb metabolism.

  11. Functional morphology and patterns of blood flow in the heart of Python regius.

    PubMed

    Starck, J Matthias

    2009-06-01

    Brightness-modulated ultrasonography, continuous-wave Doppler, and pulsed-wave Doppler-echocardiography were used to analyze the functional morphology of the undisturbed heart of ball pythons. In particular, the action of the muscular ridge and the atrio-ventricular valves are key features to understand how patterns of blood flow emerge from structures directing blood into the various chambers of the heart. A step-by-step image analysis of echocardiographs shows that during ventricular diastole, the atrio-ventricular valves block the interventricular canals so that blood from the right atrium first fills the cavum venosum, and blood from the left atrium fills the cavum arteriosum. During diastole, blood from the cavum venosum crosses the muscular ridge into the cavum pulmonale. During middle to late systole the muscular ridge closes, thus prohibiting further blood flow into the cavum pulmonale. At the same time, the atrio-ventricular valves open the interventricular canal and allow blood from the cavum arteriosum to flow into the cavum venosum. In the late phase of ventricular systole, all blood from the cavum pulmonale is pressed into the pulmonary trunk; all blood from the cavum venosum is pressed into both aortas. Quantitative measures of blood flow volume showed that resting snakes bypass the pulmonary circulation and shunt about twice the blood volume into the systemic circulation as into the pulmonary circulation. When digesting, the oxygen demand of snakes increased tremendously. This is associated with shunting more blood into the pulmonary circulation. The results of this study allow the presentation of a detailed functional model of the python heart. They are also the basis for a functional hypothesis of how shunting is achieved. Further, it was shown that shunting is an active regulation process in response to changing demands of the organism (here, oxygen demand). Finally, the results of this study support earlier reports about a dual pressure

  12. Mechanical performance comparison between RotaFlow and CentriMag centrifugal blood pumps in an adult ECLS model.

    PubMed

    Yulong Guan; Xiaowei Su; McCoach, Robert; Kunselman, Allen; El-Banayosy, Aly; Undar, Akif

    2010-03-01

    Centrifugal blood pumps have been widely adopted in conventional adult cardiopulmonary bypass and circulatory assist procedures. Different brands of centrifugal blood pumps incorporate distinct designs which affect pump performance. In this adult extracorporeal life support (ECLS) model, the performances of two brands of centrifugal blood pump (RotaFlow blood pump and CentriMag blood pump) were compared. The simulated adult ECLS circuit used in this study included a centrifugal blood pump, Quadrox D membrane oxygenator and Sorin adult ECLS tubing package. A Sorin Cardiovascular(R) VVR(R) 4000i venous reservoir (Sorin S.p.A., Milan, Italy) with a Hoffman clamp served as a pseudo-patient. The circuit was primed with 900ml heparinized human packed red blood cells and 300ml lactated Ringer's solution (total volume 1200 ml, corrected hematocrit 40%). Trials were conducted at normothermia (36 degrees C). Performance, including circuit pressure and flow rate, was measured for every setting analyzed. The shut-off pressure of the RotaFlow was higher than the CentriMag at all measurement points given the same rotation speed (p < 0.0001). The shut-off pressure differential between the two centrifugal blood pumps was significant and increased given higher rotation speeds (p < 0.0001). The RotaFlow blood pump has higher maximal flow rate (9.08 +/- 0.01L/min) compared with the CentriMag blood pump (8.37 +/- 0.02L/min) (p < 0.0001). The blood flow rate differential between the two pumps when measured at the same revolutions per minute (RPM) ranged from 1.64L/min to 1.73L/min. The results obtained in this experiment demonstrate that the RotaFlow has a higher shut-off pressure (less retrograde flow) and maximal blood flow rate than the CentriMag blood pump. Findings support the conclusion that the RotaFlow disposable pump head has a better mechanical performance than the CentriMag. In addition, the RotaFlow disposable pump is 20-30 times less expensive than the CentriMag.

  13. Simulated Microgravity Increases Cutaneous Blood Flow in the Head and Leg of Humans

    NASA Technical Reports Server (NTRS)

    Stout, M. Shannon; Watenpaugh, Donald E.; Breit, Gregory A.; Hargens, Alan R.

    1995-01-01

    The cutaneous micro-circulation vasodilates during acute 6 deg. head-down tilt (HDT, simulated microgravity) relative to upright conditions, more in the lower body than in the upper body. We expected that relative magnitudes of and differences between upper and lower body cutaneous blood flow elevation would be sustained during initial acclimation to simulated microgravity. We measured cutaneous micro-vascular blood flow with laser-Doppler flowmetry at the leg (over the distal tibia) and cheek (over the zygomatic arch) of eight healthy men before, during, and after 24 h of HDT. Results were calculated as a percentage of baseline value (100% measured during pre-tilt upright sitting). Cutaneous blood flow in the cheek increased significantly to 165 +/- 37% (mean + SE, p less than 0.05) at 9-12 h HDT, then returned to near baseline values by 24 h HDT (114 +/- 29%, NSD), despite increased local arterial pressure. Microvascular flow in the leg remained significantly elevated above baseline throughout 24 h HDT (427 +/- 85% at 3 h HDT and 215 +/- 142% at 24 h HDT, p less than 0.05). During the 6-h upright sitting recovery period, cheek and leg blood flow levels returned to near pre-tilt baseline values. Because hydrostatic effects of HDT increase local arterial pressure at the carotid sinus, baroreflex-mediated withdrawal of sympathetic tone probably contributed to increased microvascular flows at the head and leg during HDT. In the leg, baroreflex effects combined with minimal stimulation of local veno-arteriolar and myogenic autoregulatory vasoconstriction to elicit relatively larger and more sustained increases in cutaneous flow during HDT. In the cheek, delayed myogenic vasoconstriction and/or humoral effects apparently compensated for flow elevation by 24 h of HDT. Therefore, localized vascular adaptations to gravity probably explain differences in acclimation of lower and upper body blood flow to HDT and actual microgravity.

  14. Numerical Simulations of Blood Flows in the Left Atrium

    NASA Astrophysics Data System (ADS)

    Zhang, Lucy

    2008-11-01

    A novel numerical technique of solving complex fluid-structure interactions for biomedical applications is introduced. The method is validated through rigorous convergence and accuracy tests. In this study, the technique is specifically used to study blood flows in the left atrium, one of the four chambers in the heart. Stable solutions are obtained at physiologic Reynolds numbers by applying pulmonary venous inflow, mitral valve outflow and appropriate constitutive equations to closely mimic the behaviors of biomaterials. Atrial contraction is also implemented as a time-dependent boundary condition to realistically describe the atrial wall muscle movements, thus producing accurate interactions with the surrounding blood. From our study, the transmitral velocity, filling/emptying velocity ratio, durations and strengths of vortices are captured numerically for sinus rhythms (healthy heart beat) and they compare quite well with reported clinical studies. The solution technique can be further used to study heart diseases such as the atrial fibrillation, thrombus formation in the chamber and their corresponding effects in blood flows.

  15. Blood flow quantification using 1D CFD parameter identification

    NASA Astrophysics Data System (ADS)

    Brosig, Richard; Kowarschik, Markus; Maday, Peter; Katouzian, Amin; Demirci, Stefanie; Navab, Nassir

    2014-03-01

    Patient-specific measurements of cerebral blood flow provide valuable diagnostic information concerning cerebrovascular diseases rather than visually driven qualitative evaluation. In this paper, we present a quantitative method to estimate blood flow parameters with high temporal resolution from digital subtraction angiography (DSA) image sequences. Using a 3D DSA dataset and a 2D+t DSA sequence, the proposed algorithm employs a 1D Computational Fluid Dynamics (CFD) model for estimation of time-dependent flow values along a cerebral vessel, combined with an additional Advection Diffusion Equation (ADE) for contrast agent propagation. The CFD system, followed by the ADE, is solved with a finite volume approximation, which ensures the conservation of mass. Instead of defining a new imaging protocol to obtain relevant data, our cost function optimizes the bolus arrival time (BAT) of the contrast agent in 2D+t DSA sequences. The visual determination of BAT is common clinical practice and can be easily derived from and be compared to values, generated by a 1D-CFD simulation. Using this strategy, we ensure that our proposed method fits best to clinical practice and does not require any changes to the medical work flow. Synthetic experiments show that the recovered flow estimates match the ground truth values with less than 12% error in the mean flow rates.

  16. [The value of the thermocouple in the measurement of the gastric mucosal blood-flow. The influence of the occlusion of the celiac artery and prostaglandin E1 on the gastric mucosal blood flow. An experimental study in animals (author's transl)].

    PubMed

    Koch, H; Demling, L

    1976-02-27

    The study has been carried out to ensure the positive evidence of the measurement of the gastric mucosal blood-flow with the aid of the thermocouple (heat-clearance technique). The experiments have shown that the suction pressure of 600 mm mercury column which was used to fix the Thermocouple to the mucosa was indispensable in order to assess the blood-flow in the entire depth of the mucosa. Changes in the mucosal blood-flow are measuured at the same rate in all quadrants of the gastric corpus. The measuring of the blood-flow of a well circumscribed area of the mucosa is therefore representative for the entire corpus. Vasopressin led to a significant reduction of the gastric mucosal blood-flow measured with heat-clearance as well aminopyrine-clearance. There was a linear correlation between the results of both methods. Vasopressin selectively reduces the blood-flow of the gastric mucosa but not of the submucosa, the muscular layer and the serosa. Therefore it seems to be probable that changes in mucosal blood-flow selectively can be measured with the aid of the thermocouple. After previous stimulation with pentagastrin neither mucosal blood-flow nor acid secretion of the stomach were influenced by the occlusion of the celiac artery by 25 %. The occlusion of the celiac artery by 50 % reduced significantly the pentagastrin-stimulated gastric mucosal blood-flow whereas the acid secretion was not influenced. Prostaglandin E1 at a dose rate of 2 mug/kg-h increased significantly arterial and mucosal blood-flow as well as acid secretion of the stomach. In comparison PGE1 administered at a dose rate of 4 mug/kg-h reduced significantly gastric mucosal blood-flow and gastric secretion. PGE1 at a dose rate of 8 mug/kg-h did not produce any significant changes in blood-flow and secretion. The results suggested that the changes of gastric secretion observed with PGE1 were the consequence of primary changes in the gastric mucosal blood-flow.

  17. Effect of stratified inequality of blood flow on gas exchange in liquid-filled lungs.

    NASA Technical Reports Server (NTRS)

    West, J. B.; Maloney, J. E.; Castle, B. L.

    1972-01-01

    This investigation set out to answer two questions: (1) are the distal alveoli in the terminal lung units less well perfused than the proximal alveoli, i.e., is there stratification of blood flow; and (2) if so, does this enhance gas exchange in the presence of stratified inequality of ventilation. Excised dog lungs were ventilated with saline and perfused with blood. Following single inspirations of xenon 133 in saline and various periods of breath holding, the expired xenon concentration against volume was measured and it confirmed marked stratified inequality of ventilation under these conditions. By measuring the rate of depletion of xenon from alveoli during a period of blood flow, we showed that the alveoli which emptied at the end of expiration had 16% less blood flow than those exhaling earlier. However, by measuring the xenon concentration in pulmonary venous blood, we found that about 10% less tracer was transferred from the alveoli into the blood when the inspired xenon was stratified within the respiratory zone. Thus while stratification of blood flow was confirmed, it was shown to impair rather than enhance the efficiency of gas transfer.

  18. A modeling study on the influence of blood flow regulation on skin temperature pulsations

    NASA Astrophysics Data System (ADS)

    Tang, Yanliang; Mizeva, Irina; He, Ying

    2017-04-01

    Nowadays together with known optic techniques of microcirculation blood flow monitoring, skin temperature measurements are developed as well. In this paper, a simple one-dimensional bioheat transfer model was developed to analyse the heat wave transport in biological tissue, where an arteriole vessel with pulsatile blood is located. The simulated results show that the skin temperature oscillation amplitudes attenuate with the increase of blood flow oscillation frequency which gives the same tendency as that in the experiments. The parameter analyses further show that the amplitude of oscillation is also influenced by oscillation amplitude of blood and effective thermal conductivity. When oscillation amplitude of blood flow and effective thermal conductivity increase, the amplitude of skin temperature oscillation increases nonlinearly. Variation of effective thermal convective influence to the time delay of the thermal wave on the skin surface and distort it. Combination of two measurement techniques: one for estimation blood flow oscillations in the microvessels and other to the skin temperature measurement can produce additional information about the skin properties.

  19. Effect of gravitational and inertial forces on vertical distribution of pulmonary blood flow

    NASA Technical Reports Server (NTRS)

    Chevalier, P. A.; Reed, J. H., Jr.; Vandenberg, R. A.; Wood, E. H.

    1978-01-01

    Vertical distribution of pulmonary blood flow (VDPBF) was studied, using radioactive microsphere emboli, in dogs without thoracotomy in the right decubitus position during exposure to lateral accelerations of 1, 2, 4, and 6 G. At all levels of force environment studied, an inverse linear relationship was observed between vertical height in the thorax and pulmonary blood flow (ml/min/ml lung tissue) with a decrease in flow to the most dependent region of the lung despite large increases in intravascular pressures at this site. Changes in blood flow were smallest at the mid-lung level, the hydrostatic 'balance point' for vascular and pleural pressures. These force environment-dependent changes in VDPBF are not readily explainable by the Starling resistor analog. Gravity-dependent regional differences in pleural and associated interstitial pressures, plus possible changes in vascular tone resulting from inadequate aeration of blood in the most dependent regions of the lung, probably also affect VDPBF.

  20. Blood filling and flow in lungs during change in body position in space

    NASA Technical Reports Server (NTRS)

    Pogodin, A. S.; Mazhbich, B. I.

    1980-01-01

    In the horizontal position (supine and lateral), in the upright position (head up and head down) and during change of the cat body position in space, quantitative responses of regional blood volume and blood flow in the lungs (ml/100 cu cm) revealed presence of the gradient in the gravitation direction. Blood volume and blood flow of different lung portions changed qualitatively and quantitatively in different ways. These changes occurred only in the direction producing the equality of regional hydrostatical and hemodynamic loads in the lungs at either horizontal level.

  1. Dynamics of the blood flow in the curved artery with the rolling massage

    NASA Astrophysics Data System (ADS)

    Yi, H. H.; Wu, X. H.; Yao, Y. L.

    2011-10-01

    Arterial wall shear stress and flow velocity are important factors in the development of some arterial diseases. Here, we aim to investigate the dynamic effect of the rolling massage on the property of the blood flow in the curved artery. The distributions of flow velocity and shear stress for the blood flow are computed by the lattice Boltzmann method, and the dynamic factors under different rolling techniques are studied numerically. The study is helpful to understand the mechanism of the massage and develop the massage techniques.

  2. Assessing potential errors of MRI-based measurements of pulmonary blood flow using a detailed network flow model

    PubMed Central

    Buxton, R. B.; Prisk, G. K.

    2012-01-01

    MRI images of pulmonary blood flow using arterial spin labeling (ASL) measure the delivery of magnetically tagged blood to an image plane during one systolic ejection period. However, the method potentially suffers from two problems, each of which may depend on the imaging plane location: 1) the inversion plane is thicker than the imaging plane, resulting in a gap that blood must cross to be detected in the image; and 2) ASL includes signal contributions from tagged blood in conduit vessels (arterial and venous). By using an in silico model of the pulmonary circulation we found the gap reduced the ASL signal to 64–74% of that in the absence of a gap in the sagittal plane and 53–84% in the coronal. The contribution of the conduit vessels varied markedly as a function of image plane ranging from ∼90% of the overall signal in image planes that encompass the central hilar vessels to <20% in peripheral image planes. A threshold cutoff removing voxels with intensities >35% of maximum reduced the conduit vessel contribution to the total ASL signal to ∼20% on average; however, planes with large contributions from conduit vessels underestimate acinar flow due to a high proportion of in-plane flow, making ASL measurements of perfusion impractical. In other image planes, perfusion dominated the resulting ASL images with good agreement between ASL and acinar flow. Similarly, heterogeneity of the ASL signal as measured by relative dispersion is a reliable measure of heterogeneity of the acinar flow distribution in the same image planes. PMID:22539167

  3. Assessing potential errors of MRI-based measurements of pulmonary blood flow using a detailed network flow model.

    PubMed

    Burrowes, K S; Buxton, R B; Prisk, G K

    2012-07-01

    MRI images of pulmonary blood flow using arterial spin labeling (ASL) measure the delivery of magnetically tagged blood to an image plane during one systolic ejection period. However, the method potentially suffers from two problems, each of which may depend on the imaging plane location: 1) the inversion plane is thicker than the imaging plane, resulting in a gap that blood must cross to be detected in the image; and 2) ASL includes signal contributions from tagged blood in conduit vessels (arterial and venous). By using an in silico model of the pulmonary circulation we found the gap reduced the ASL signal to 64-74% of that in the absence of a gap in the sagittal plane and 53-84% in the coronal. The contribution of the conduit vessels varied markedly as a function of image plane ranging from ∼90% of the overall signal in image planes that encompass the central hilar vessels to <20% in peripheral image planes. A threshold cutoff removing voxels with intensities >35% of maximum reduced the conduit vessel contribution to the total ASL signal to ∼20% on average; however, planes with large contributions from conduit vessels underestimate acinar flow due to a high proportion of in-plane flow, making ASL measurements of perfusion impractical. In other image planes, perfusion dominated the resulting ASL images with good agreement between ASL and acinar flow. Similarly, heterogeneity of the ASL signal as measured by relative dispersion is a reliable measure of heterogeneity of the acinar flow distribution in the same image planes.

  4. Unsteady Blood Flow with Nanoparticles Through Stenosed Arteries in the Presence of Periodic Body Acceleration

    NASA Astrophysics Data System (ADS)

    Fatin Jamil, Dzuliana; Roslan, Rozaini; Abdulhameed, Mohammed; Che-Him, Norziha; Sufahani, Suliadi; Mohamad, Mahathir; Ghazali Kamardan, Muhamad

    2018-04-01

    The effects of nanoparticles such as Fe 3O4,TiO2, and Cu on blood flow inside a stenosed artery are studied. In this study, blood was modelled as non-Newtonian Bingham plastic fluid subjected to periodic body acceleration and slip velocity. The flow governing equations were solved analytically by using the perturbation method. By using the numerical approaches, the physiological parameters were analyzed, and the blood flow velocity distributions were generated graphically and discussed. From the flow results, the flow speed increases as slip velocity increases and decreases as the values of yield stress increases.

  5. Evaluation of blood flow in human exercising muscle by diffuse correlation spectroscopy: a phantom model study

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Mikie; Ono, Yumie; Ichinose, Masashi

    2018-02-01

    Diffuse correlation spectroscopy (DCS) has a potential to noninvasively and quantitatively measure the blood flow in the exercising muscle that could contribute to the fields of sports physiology and medicine. However, the blood flow index (BFI) measured from skin surface by DCS reflects hemodynamic signals from both superficial tissue and muscle layer. Thus, an appropriate calibration technology is required to quantify the absolute blood flow in the muscle layer. We therefore fabricated a realistic two-layer phantom model consisted of a static silicon layer imitating superficial tissue and a dynamic flow layer imitating the muscle blood flow and investigated the relationship between the simulated blood flow rate in the muscle layer and the BFI measured from the surface of the phantom. The absorption coefficient and the reduced scattering coefficient of the forearm were measured from 25 healthy young adults using a time-resolved nearinfrared spectroscopy. The depths of the superficial and muscle layers of forearm were also determined by ultrasound tomography images from 25 healthy young adults. The phantoms were fabricated to satisfy these optical coefficients and anatomical constraints. The simulated blood flow rate were set from 0 mL/ min to 68.7 mL/ min in ten steps, which is considered to cover a physiological range of mean blood flow of the forearm between per 100g of muscle tissue at rest to heavy dynamic handgrip exercise. We found a proportional relationship between the flow rates and BFIs with significant correlation coefficient of R = 0.986. Our results suggest that the absolute exercising muscle blood flow could be estimated by DCS with optimal calibration using phantom models.

  6. Predicting dynamics and rheology of blood flow: A comparative study of multiscale and low-dimensional models of red blood cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pan, Wenxiao; Fedosov, Dmitry A.; Caswell, Bruce

    In this work we compare the predictive capability of two mathematical models for red blood cells (RBCs) focusing on blood flow in capillaries and arterioles. Both RBC models as well as their corresponding blood flows are based on the dissipative particle dynamics (DPD) method, a coarse-grained molecular dynamics approach. The first model employs a multiscale description of the RBC (MS-RBC), with its membrane represented by hundreds or even thousands of DPD-particles connected by springs into a triangular network in combination with out-of-plane elastic bending resistance. Extra dissipation within the network accounts for membrane viscosity, while the characteristic biconcave RBC shapemore » is achieved by imposition of constraints for constant membrane area and constant cell volume. The second model is based on a low-dimensional description (LD-RBC) constructed as a closed torus-like ring of only 10 large DPD colloidal particles. They are connected into a ring by worm-like chain (WLC) springs combined with bending resistance. The LD-RBC model can be fitted to represent the entire range of nonlinear elastic deformations as measured by optical-tweezers for healthy and for infected RBCs in malaria. MS-RBCs suspensions model the dynamics and rheology of blood flow accurately for any size vessel but this approach is computationally expensive above 100 microns. Surprisingly, the much more economical suspensions of LD-RBCs also capture the blood flow dynamics and rheology accurately except for vessels with sizes comparable to RBC diameter. In particular, the LD-RBC suspensions are shown to properly capture the experimental data for the apparent viscosity of blood and its cell-free layer (CFL) in tube flow. Taken together, these findings suggest a hierarchical approach in modeling blood flow in the arterial tree, whereby the MS-RBC model should be employed for capillaries and arterioles below 100 microns, the LD-RBC model for arterioles, and the continuum description for

  7. A Novel Method of Combining Blood Oxygenation and Blood Flow Sensitive Magnetic Resonance Imaging Techniques to Measure the Cerebral Blood Flow and Oxygen Metabolism Responses to an Unknown Neural Stimulus

    PubMed Central

    Simon, Aaron B.; Griffeth, Valerie E. M.; Wong, Eric C.; Buxton, Richard B.

    2013-01-01

    Simultaneous implementation of magnetic resonance imaging methods for Arterial Spin Labeling (ASL) and Blood Oxygenation Level Dependent (BOLD) imaging makes it possible to quantitatively measure the changes in cerebral blood flow (CBF) and cerebral oxygen metabolism (CMRO2) that occur in response to neural stimuli. To date, however, the range of neural stimuli amenable to quantitative analysis is limited to those that may be presented in a simple block or event related design such that measurements may be repeated and averaged to improve precision. Here we examined the feasibility of using the relationship between cerebral blood flow and the BOLD signal to improve dynamic estimates of blood flow fluctuations as well as to estimate metabolic-hemodynamic coupling under conditions where a stimulus pattern is unknown. We found that by combining the information contained in simultaneously acquired BOLD and ASL signals through a method we term BOLD Constrained Perfusion (BCP) estimation, we could significantly improve the precision of our estimates of the hemodynamic response to a visual stimulus and, under the conditions of a calibrated BOLD experiment, accurately determine the ratio of the oxygen metabolic response to the hemodynamic response. Importantly we were able to accomplish this without utilizing a priori knowledge of the temporal nature of the neural stimulus, suggesting that BOLD Constrained Perfusion estimation may make it feasible to quantitatively study the cerebral metabolic and hemodynamic responses to more natural stimuli that cannot be easily repeated or averaged. PMID:23382977

  8. Microvascular Blood Flow Improvement in Hyperglycemic Obese Adult Patients by Hypocaloric Diet.

    PubMed

    Mastantuono, T; Di Maro, M; Chiurazzi, M; Battiloro, L; Starita, N; Nasti, G; Lapi, D; Iuppariello, L; Cesarelli, M; D'Addio, G; Colantuoni, A

    2016-11-01

    The present study was aimed to assess the changes in skin microvascular blood flow (SBF) in newly diagnosed hyperglycemic obese subjects, administered with hypocaloric diet. Adult patients were recruited and divided in three groups: NW group (n=54), NG (n=54) and HG (n=54) groups were constituted by normal weight, normoglycemic and hyperglycemic obese subjects, respectively. SBF was measured by laser Doppler perfusion monitoring technique and oscillations in blood flow were analyzed by spectral methods under baseline conditions, at 3 and 6 months of dietary treatment. Under resting conditions, SBF was lower in HG group than in NG and NW ones. Moreover, all subjects showed blood flow oscillations with several frequency components. In particular, hyperglycemic obese patients revealed lower spectral density in myogenic-related component than normoglycemic obese and normal weight ones. Moreover, post-occlusive reactive hyperemia (PORH) was impaired in hyperglycemic obese compared to normoglycemic and normal weigh subjects. After hypocaloric diet, in hyperglycemic obese patients there was an improvement in SBF accompanied by recovery in myogenic-related oscillations and arteriolar responses during PORH. In conclusion, hyperglycemia markedly affected peripheral microvascular function; hypocaloric diet ameliorated tissue blood flow.

  9. Microvascular Blood Flow Improvement in Hyperglycemic Obese Adult Patients by Hypocaloric Diet

    PubMed Central

    Mastantuono, T; Di Maro, M.; Chiurazzi, M.; Battiloro, L.; Starita, N.; Nasti, G.; Lapi, D.; Iuppariello, L.; Cesarelli, M.; D’Addio, G.; Colantuoni, A.

    2016-01-01

    The present study was aimed to assess the changes in skin microvascular blood flow (SBF) in newly diagnosed hyperglycemic obese subjects, administered with hypocaloric diet. Adult patients were recruited and divided in three groups: NW group (n=54), NG (n=54) and HG (n=54) groups were constituted by normal weight, normoglycemic and hyperglycemic obese subjects, respectively. SBF was measured by laser Doppler perfusion monitoring technique and oscillations in blood flow were analyzed by spectral methods under baseline conditions, at 3 and 6 months of dietary treatment. Under resting conditions, SBF was lower in HG group than in NG and NW ones. Moreover, all subjects showed blood flow oscillations with several frequency components. In particular, hyperglycemic obese patients revealed lower spectral density in myogenic-related component than normoglycemic obese and normal weight ones. Moreover, post-occlusive reactive hyperemia (PORH) was impaired in hyperglycemic obese compared to normoglycemic and normal weigh subjects. After hypocaloric diet, in hyperglycemic obese patients there was an improvement in SBF accompanied by recovery in myogenic-related oscillations and arteriolar responses during PORH. In conclusion, hyperglycemia markedly affected peripheral microvascular function; hypocaloric diet ameliorated tissue blood flow. PMID:27896221

  10. Relationship between vertebral artery blood flow in different head positions and vertigo.

    PubMed

    Araz Server, Ela; Edizer, Deniz Tuna; Yiğit, Özgür; Yasak, Ahmet Görkem; Erdim, Çağrı

    2018-01-01

    To identify the vertebral artery blood flow in different head positions in patients with positional vertigo with no specific diagnosis. Patients with history of vestibular symptoms associated with changes in head position were enrolled into the study. Healthy volunteers were evaluated as control group. Doppler ultrasonography examination of the cervical segment of the vertebral arteries was performed under three different head positions: (i) supine position, (ii) head hyperextended and rotated to the right side and (iii) head hyperextended and rotated to the left side. In the study group, right and left vertebral artery blood flow was significantly lower in the ipsilateral hyperextended position compared to standard supine position (respectively p = .014; p = .001), but did not differ significantly when compared between the standard supine and contralateral hyperextended positions (respectively = .959; p = .669). In the control group, left and right vertebral artery blood flow did not differ significantly when the head was hyperextended to the right or left sides compared to standard supine position (p > .05). Our data demonstrated that the etiology of vestibular complaints in patients with undiagnosed positional vertigo might be related to impairment in vertebral artery blood flow according to head positions.

  11. Retinal Blood Flow in Type 1 Diabetic Patients With No or Mild Diabetic Retinopathy During Euglycemic Clamp

    PubMed Central

    Pemp, Berthold; Polska, Elżbieta; Garhofer, Gerhard; Bayerle-Eder, Michaela; Kautzky-Willer, Alexandra; Schmetterer, Leopold

    2010-01-01

    OBJECTIVE To compare total retinal blood flow in diabetic patients with no or mild nonproliferative diabetic retinopathy and healthy control subjects and to investigate in patients whether there is a difference between retinal blood flow before morning insulin and under normoglycemic conditions using a glucose clamp. RESEARCH DESIGN AND METHODS Twenty patients with type 1 diabetes with no or mild diabetic retinopathy were included in this open parallel-group study, and 20 healthy age- and sex-matched subjects were included as control subjects. Retinal blood flow was assessed by combining velocity measurements using laser Doppler velocimetry and diameter measurements using a commercially available dynamic vessel analyzer. Measurements were performed before and during a euglycemic clamp. RESULTS Total retinal blood flow was higher in diabetic patients (53 ± 16 μl/min) than in healthy subjects (43 ± 16 μl/min; P = 0.034 between groups). When plasma glucose in diabetic patients was reduced from 9.3 ± 1.7 to 5.3 ± 0.5 mmol/l (P < 0.001) retinal blood flow decreased to 49 ± 15 μl/min (P = 0.0003 vs. baseline). Total retinal blood flow during the glucose clamp was not significantly different from blood flow in normal control subjects (P = 0.161). CONCLUSIONS Type 1 diabetic patients with no or only mild diabetic retinopathy have increased retinal blood flow before their morning insulin dosage. Blood flow is reduced toward normal during euglycemic conditions. Retinal blood flow may fluctuate significantly with fluctuating plasma glucose levels, which may contribute to the microvascular changes seen in diabetic retinopathy. PMID:20585003

  12. Influence of magnetic field on chemically reactive blood flow through stenosed bifurcated arteries

    NASA Astrophysics Data System (ADS)

    Hossain, Khan Enaet; Haque, Md. Mohidul

    2017-06-01

    Dynamic response of mass transfer in chemically reactive blood flow through bifurcated arteries under the stenotic condition is numerically studied in the present of a uniform magnetic field. The blood flowing through the artery is assumed an incompressible, fully developed and Newtonian. The nonlinear unsteady flow phenomena are governed by the Navier-Stokes and concentration equations. All these equations together with the appropriate boundary conditions describing the present biomechanical problem are transformed by using a radial transformation and the numerical results are obtained using a finite difference technique. Effects of stenosed bifurcation and externally applied magnetic field on the blood flow with chemical reaction are discussed with the help of graph. All the flow characteristics are found to be affected by the presence of chemical reaction and exposure of magnetic field of different intensities. Finally some important findings of the problem are concluded in this work.

  13. Functional dilatation and medial remodeling of the renal artery in response to chronic increased blood flow.

    PubMed

    Roan, Jun-Neng; Yeh, Chin-Yi; Chiu, Wen-Cheng; Lee, Chou-Hwei; Chang, Shih-Wei; Jiangshieh, Ya-Fen; Tsai, Yu-Chuan; Lam, Chen-Fuh

    2011-01-01

    Renal blood flow (RBF) is tightly regulated by several intrinsic pathways in maintaining optimal kidney blood supply. Using a rat model of aortocaval (AC) fistula, we investigated remodeling of the renal artery following prolonged increased blood flow. An AC fistula was created in the infrarenal aorta of anesthetized rats, and changes of blood flow in the renal artery were assessed using an ultrasonic flow probe. Morphological changes and expression of endothelial nitric oxide synthase and matrix metalloproteinase-2 in the remodeled renal artery were analyzed. Blood flow in the renal artery increased immediately after creation of AC fistula, but normal RBF was restored 8 weeks later. The renal artery dilated significantly 8 weeks after operation. Expression of endothelial nitric oxide synthase and matrix metalloproteinase-2 was upregulated shortly after blood flow increase, and returned to baseline levels after 3 weeks. Histological sections showed luminal dilatation with medial thickening and endothelial cell-to-smooth muscle cell attachments in the remodeled renal artery. Increased RBF was accommodated by functional dilatation and remodeling in the medial layer of the renal artery in order to restore normal blood flow. Our results provide important mechanistic insight into the intrinsic regulation of the renal artery in response to increased RBF. Copyright © 2011 S. Karger AG, Basel.

  14. Nitric oxide in the nucleus raphe magnus modulates cutaneous blood flow in rats during hypothermia.

    PubMed

    Arami, Masoumeh Kourosh; Zade, Javad Mirnajafi; Komaki, Alireza; Amiri, Mahmood; Mehrpooya, Sara; Jahanshahi, Ali; Jamei, Behnam

    2015-10-01

    Nucleus Raphe Magnus (NRM) that is involved in the regulation of body temperature contains nitric oxide (NO) synthase. Considering the effect of NO on skin blood flow control, in this study, we assessed its thermoregulatory role within the raphe magnus. To this end, tail blood flow of male Wistar rats was measured by laser doppler following the induction of hypothermia. Intra-NRM injection of SNP (exogenous NO donor, 0.1- 0.2 μl, 0.2 nM) increased the blood flow. Similarly, unilateral microinjection of glutamate (0.1- 0.2 μl, 2.3 nM) into the nucleus increased the blood flow. This effect of L-glutamate was reduced by prior intra NRM administration of NO synthase inhibitor N(G)-methyl-L-arginine or N(G)-nitro-L-arginine methyl ester (L-NAME, 0.1 µl, 100 nM). It is concluded that NO modulates the thermoregulatory response of NRM to hypothermia and may interact with excitatory amino acids in central skin blood flow regulation.

  15. Blood flow/pump rotation ratio as an artificial lung performance monitoring tool during extracorporeal respiratory support using centrifugal pumps

    PubMed Central

    Park, Marcelo; Mendes, Pedro Vitale; Hirota, Adriana Sayuri; dos Santos, Edzangela Vasconcelos; Costa, Eduardo Leite Vieira; Azevedo, Luciano Cesar Pontes

    2015-01-01

    Objective To analyze the correlations of the blood flow/pump rotation ratio and the transmembrane pressure, CO2 and O2 transfer during the extracorporeal respiratory support. Methods Five animals were instrumented and submitted to extracorporeal membrane oxygenation in a five-step protocol, including abdominal sepsis and lung injury. Results This study showed that blood flow/pump rotations ratio variations are dependent on extracorporeal membrane oxygenation blood flow in a positive logarithmic fashion. Blood flow/pump rotation ratio variations are negatively associated with transmembrane pressure (R2 = 0.5 for blood flow = 1500mL/minute and R2 = 0.4 for blood flow = 3500mL/minute, both with p < 0.001) and positively associated with CO2 transfer variations (R2 = 0.2 for sweep gas flow ≤ 6L/minute, p < 0.001, and R2 = 0.1 for sweep gas flow > 6L/minute, p = 0.006), and the blood flow/pump rotation ratio is not associated with O2 transfer variations (R2 = 0.01 for blood flow = 1500mL/minute, p = 0.19, and R2 = - 0.01 for blood flow = 3500 mL/minute, p = 0.46). Conclusion Blood flow/pump rotation ratio variation is negatively associated with transmembrane pressure and positively associated with CO2 transfer in this animal model. According to the clinical situation, a decrease in the blood flow/pump rotation ratio can indicate artificial lung dysfunction without the occurrence of hypoxemia. PMID:26340159

  16. Blood flow/pump rotation ratio as an artificial lung performance monitoring tool during extracorporeal respiratory support using centrifugal pumps.

    PubMed

    Park, Marcelo; Mendes, Pedro Vitale; Hirota, Adriana Sayuri; dos Santos, Edzangela Vasconcelos; Costa, Eduardo Leite Vieira; Azevedo, Luciano Cesar Pontes

    2015-01-01

    To analyze the correlations of the blood flow/pump rotation ratio and the transmembrane pressure, CO2 and O2 transfer during the extracorporeal respiratory support. Five animals were instrumented and submitted to extracorporeal membrane oxygenation in a five-step protocol, including abdominal sepsis and lung injury. This study showed that blood flow/pump rotations ratio variations are dependent on extracorporeal membrane oxygenation blood flow in a positive logarithmic fashion. Blood flow/pump rotation ratio variations are negatively associated with transmembrane pressure (R2 = 0.5 for blood flow = 1500mL/minute and R2 = 0.4 for blood flow = 3500mL/minute, both with p < 0.001) and positively associated with CO2 transfer variations (R2 = 0.2 for sweep gas flow ≤ 6L/minute, p < 0.001, and R2 = 0.1 for sweep gas flow > 6L/minute, p = 0.006), and the blood flow/pump rotation ratio is not associated with O2 transfer variations (R2 = 0.01 for blood flow = 1500mL/minute, p = 0.19, and R2 = - 0.01 for blood flow = 3500 mL/minute, p = 0.46). Blood flow/pump rotation ratio variation is negatively associated with transmembrane pressure and positively associated with CO2 transfer in this animal model. According to the clinical situation, a decrease in the blood flow/pump rotation ratio can indicate artificial lung dysfunction without the occurrence of hypoxemia.

  17. Cerebral blood flow response to changes in arterial carbon dioxide tension during hypothermic cardiopulmonary bypass in children

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kern, F.H.; Ungerleider, R.M.; Quill, T.J.

    1991-04-01

    We examined the relationship of changes in partial pressure of carbon dioxide on cerebral blood flow responsiveness in 20 pediatric patients undergoing hypothermic cardiopulmonary bypass. Cerebral blood flow was measured during steady-state hypothermic cardiopulmonary bypass with the use of xenon 133 clearance methodology at two different arterial carbon dioxide tensions. During these measurements there was no significant change in mean arterial pressure, nasopharyngeal temperature, pump flow rate, or hematocrit value. Cerebral blood flow was found to be significantly greater at higher arterial carbon dioxide tensions (p less than 0.01), so that for every millimeter of mercury rise in arterial carbonmore » dioxide tension there was a 1.2 ml.100 gm-1.min-1 increase in cerebral blood flow. Two factors, deep hypothermia (18 degrees to 22 degrees C) and reduced age (less than 1 year), diminished the effect carbon dioxide had on cerebral blood flow responsiveness but did not eliminate it. We conclude that cerebral blood flow remains responsive to changes in arterial carbon dioxide tension during hypothermic cardiopulmonary bypass in infants and children; that is, increasing arterial carbon dioxide tension will independently increase cerebral blood flow.« less

  18. Correlation of volumetric flow rate and skin blood flow with cold intolerance in digital replantation

    PubMed Central

    Zhao, Gang; Mi, Jingyi; Rui, Yongjun; Pan, Xiaoyun; Yao, Qun; Qiu, Yang

    2017-01-01

    Abstract Cold intolerance is a common complication of digital replantation. The exact etiology is unclear, but it is considered to be multifactorial, including nonsurgical characteristics, vascular, and neurologic conditions. Blood flow may play a significant role in cold intolerance. This study was designed to evaluate the correlation of digital blood flow, including volumetric flow rate (VFR) and skin blood flow (SkBF), with cold intolerance in replanted fingers. A retrospective study was conducted among patients who underwent digital replantation between 2010 and 2013. Patients were selected into study cohort based on the inclusion criteria. Surgical data was collected on each patient, including age, sex, injury mechanism, amputation level, ischemia time, number of arteries repaired, and whether or not vascular crisis occurred. Patients were included as study cohort with both nerves repaired and without chronic disease. Cold intolerance was defined as a Cold Intolerance Symptom Severity (CISS) score over 30. The arterial flow velocity and caliber were measured by Color Doppler Ultrasound and the digital VFR was calculated. The SkBF was measured by Laser Speckle Imager. Both VFR and SkBF were calculated as a percentage of the contralateral fingers. Comparative study of surgical data and blood flow was performed between the patient with and without cold intolerance. Correlation between VFR and SkBF was also analyzed. A total of 93 patients met inclusion criteria for the study. Approximately, 42 patients were identified as having cold intolerance. Fingers that survived vascular crisis had a higher incidence of cold intolerance with a lower VFR and SkBF. The VFR was higher in 2-artery replantation, but the SkBF and incidence of cold intolerance did not differ significantly. No differences were found in age, sex, injury mechanism, amputation level, or ischemia time. Furthermore, no correlation was found between VFR and SkBF. Cold intolerance of digital replantation

  19. Sleep restriction impairs blood-brain barrier function.

    PubMed

    He, Junyun; Hsuchou, Hung; He, Yi; Kastin, Abba J; Wang, Yuping; Pan, Weihong

    2014-10-29

    The blood-brain barrier (BBB) is a large regulatory and exchange interface between the brain and peripheral circulation. We propose that changes of the BBB contribute to many pathophysiological processes in the brain of subjects with chronic sleep restriction (CSR). To achieve CSR that mimics a common pattern of human sleep loss, we quantified a new procedure of sleep disruption in mice by a week of consecutive sleep recording. We then tested the hypothesis that CSR compromises microvascular function. CSR not only diminished endothelial and inducible nitric oxide synthase, endothelin1, and glucose transporter expression in cerebral microvessels of the BBB, but it also decreased 2-deoxy-glucose uptake by the brain. The expression of several tight junction proteins also was decreased, whereas the level of cyclooxygenase-2 increased. This coincided with an increase of paracellular permeability of the BBB to the small tracers sodium fluorescein and biotin. CSR for 6 d was sufficient to impair BBB structure and function, although the increase of paracellular permeability returned to baseline after 24 h of recovery sleep. This merits attention not only in neuroscience research but also in public health policy and clinical practice. Copyright © 2014 the authors 0270-6474/14/3414697-10$15.00/0.

  20. Modern Diagnostic Techniques for the Assessment of Ocular Blood Flow in Myopia: Current State of Knowledge.

    PubMed

    Grudzińska, Ewa; Modrzejewska, Monika

    2018-01-01

    Myopia is the most common refractive error and the subject of interest of various studies assessing ocular blood flow. Increasing refractive error and axial elongation of the eye result in the stretching and thinning of the scleral, choroid, and retinal tissues and the decrease in retinal vessel diameter, disturbing ocular blood flow. Local and systemic factors known to change ocular blood flow include glaucoma, medications and fluctuations in intraocular pressure, and metabolic parameters. Techniques and tools assessing ocular blood flow include, among others, laser Doppler flowmetry (LDF), retinal function imager (RFI), laser speckle contrast imaging (LSCI), magnetic resonance imaging (MRI), optical coherence tomography angiography (OCTA), pulsatile ocular blood flowmeter (POBF), fundus pulsation amplitude (FPA), colour Doppler imaging (CDI), and Doppler optical coherence tomography (DOCT). Many researchers consistently reported lower blood flow parameters in myopic eyes regardless of the used diagnostic method. It is unclear whether this is a primary change that causes secondary thinning of ocular tissues or quite the opposite; that is, the mechanical stretching of the eye wall reduces its thickness and causes a secondary lower demand of tissues for oxygen. This paper presents a review of studies assessing ocular blood flow in myopes.

  1. Quantitative blood flow measurements in the small animal cardiopulmonary system using digital subtraction angiography

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin Mingde; Marshall, Craig T.; Qi, Yi

    Purpose: The use of preclinical rodent models of disease continues to grow because these models help elucidate pathogenic mechanisms and provide robust test beds for drug development. Among the major anatomic and physiologic indicators of disease progression and genetic or drug modification of responses are measurements of blood vessel caliber and flow. Moreover, cardiopulmonary blood flow is a critical indicator of gas exchange. Current methods of measuring cardiopulmonary blood flow suffer from some or all of the following limitations--they produce relative values, are limited to global measurements, do not provide vasculature visualization, are not able to measure acute changes, aremore » invasive, or require euthanasia. Methods: In this study, high-spatial and high-temporal resolution x-ray digital subtraction angiography (DSA) was used to obtain vasculature visualization, quantitative blood flow in absolute metrics (ml/min instead of arbitrary units or velocity), and relative blood volume dynamics from discrete regions of interest on a pixel-by-pixel basis (100x100 {mu}m{sup 2}). Results: A series of calibrations linked the DSA flow measurements to standard physiological measurement using thermodilution and Fick's method for cardiac output (CO), which in eight anesthetized Fischer-344 rats was found to be 37.0{+-}5.1 ml/min. Phantom experiments were conducted to calibrate the radiographic density to vessel thickness, allowing a link of DSA cardiac output measurements to cardiopulmonary blood flow measurements in discrete regions of interest. The scaling factor linking relative DSA cardiac output measurements to the Fick's absolute measurements was found to be 18.90xCO{sub DSA}=CO{sub Fick}. Conclusions: This calibrated DSA approach allows repeated simultaneous visualization of vasculature and measurement of blood flow dynamics on a regional level in the living rat.« less

  2. Effect of nicergoline on cerebral blood flow

    PubMed Central

    Iliff, L. D.; Boulay, G. H. Du; Marshall, John; Russell, R. W. Ross; Symon, Lindsay

    1977-01-01

    Cerebral blood flow (CBF) was measured before and after intravenous injection of the cerebral vasodilator nicergoline in 13 patients with cerebrovascular disease. CBF increased in seven. The possibility that the effect of the drug in the remainder may have been masked by a fall of CBF which occurs during sequential measurement of patients at rest is discussed. PMID:925694

  3. Betahistine metabolites, aminoethylpyridine, and hydroxyethylpyridine increase cochlear blood flow in guinea pigs in vivo.

    PubMed

    Bertlich, Mattis; Ihler, Fritz; Sharaf, Kariem; Weiss, Bernhard G; Strupp, Michael; Canis, Martin

    2014-10-01

    Betahistine is a histamine-like drug that is used in the treatment of Ménière's disease. It is commonly believed that betahistine increases cochlear blood flow and thus decreases the endolymphatic hydrops that is the cause of Ménière's. Despite common clinical use, there is little understanding of the kinetics or effects of its metabolites. This study investigated the effect of the betahistine metabolites aminoethylpyridine, hydroxyethylpyridine, and pyridylacetic acid on cochlear microcirculation. Guinea pigs were randomly assigned to one of the groups: placebo, betahistine, or equimolar amounts of aminoethylpyridine, hydroxyethylpyridine, or pyridylacetic acid. Cochlear blood flow and mean arterial pressure were recorded for three minutes before and 15 minutes after treatment. Thirty Dunkin-Hartley guinea pigs assigned to one of five groups with six guinea pigs per group. Betahistine, aminoethylpyridine, and hydroxyethylpyridine caused a significant increase in cochlear blood flow in comparison to placebo. The effect seen under aminoethylpyridin was greatest. The group treated with pyridylacetic acid showed no significant effect on cochlear blood flow. Aminoethylpyridine and hydroxyethylpyridine are, like betahistine, able to increase cochlear blood flow significantly. The effect of aminoethylpyridine was greatest. Pyridylacetic acid had no effect on cochlear microcirculation.

  4. Carbon dioxide water-bath treatment augments peripheral blood flow through the development of angiogenesis.

    PubMed

    Xu, Yan-Jun; Elimban, Vijayan; Dhalla, Naranjan S

    2017-08-01

    In this study, we investigated the effects of CO 2 water-bath therapy on blood flow and angiogenesis in the ischemic hind limb, as well as some plasma angiogenic factors in peripheral ischemic model. The hind limb ischemia was induced by occluding the femoral artery for 2 weeks in rats and treated with or without CO 2 water-bath therapy at 37 °C for 4 weeks (20 min treatment every day for 5 days per week). The peak blood flow and minimal and mean blood flow in the ischemic skeletal muscle were markedly increased by the CO 2 water-bath therapy. This increase in blood flow was associated with development of angiogenesis in the muscle, as well as reduction in the ischemia-induced increase in plasma malondialdehyde levels. Although plasma vascular endothelial growth factor and nitric oxide levels were increased in animals with peripheral ischemia, the changes in these biomarkers were not affected by CO 2 water-bath therapy. These results suggest that augmentation of blood flow in the ischemic hind limb by CO 2 water-bath therapy may be due to the development of angiogenesis and reduction in oxidative stress.

  5. Doppler ultrasonography and single-fiber laser Doppler flowmetry for measurement of hind limb blood flow in anesthetized horses.

    PubMed

    Raisis, A L; Young, L E; Taylor, P M; Walsh, K P; Lekeux, P

    2000-03-01

    To use Doppler ultrasonography and single-fiber laser Doppler flowmetry (LDF) to evaluate blood flow in the dependent and nondependent hind limbs of anesthetized horses and to evaluate changes in femoral arterial blood flow and microvascular skeletal muscle perfusion in response to administration of phenylephrine hydrochloride or dobutamine hydrochloride. 6 healthy adult horses. Horses were anesthetized and positioned in left lateral recumbency. Doppler ultrasonography was used to measure velocity and volumetric flow in the femoral vessels. Single-fiber LDF was used to measure relative microvascular perfusion at a single site in the semimembranosus muscles. Phenylephrine or dobutamine was then administered to decrease or increase femoral arterial blood flow, and changes in blood flow and microvascular perfusion were recorded. Administration of phenylephrine resulted in significant decreases in femoral arterial and venous blood flows and cardiac output and significant increases in mean aortic blood pressure, systemic vascular resistance, and PCV. Administration of dobutamine resulted in significant increases in femoral arterial blood flow, mean aortic blood pressure, and PCV. Significant changes in microvascular perfusion were not detected. Results suggest that Doppler ultrasonography and single-fiber LDF can be used to study blood flows in the hind limbs of anesthetized horses. However, further studies are required to determine why changes in femoral arterial blood flows were not associated with changes in microvascular perfusion.

  6. Effects of Wrist Posture and Fingertip Force on Median Nerve Blood Flow Velocity

    PubMed Central

    Wilson, Katherine E.; Tat, Jimmy

    2017-01-01

    Purpose. The purpose of this study was to assess nerve hypervascularization using high resolution ultrasonography to determine the effects of wrist posture and fingertip force on median nerve blood flow at the wrist in healthy participants and those experiencing carpal tunnel syndrome (CTS) symptoms. Methods. The median nerves of nine healthy participants and nine participants experiencing symptoms of CTS were evaluated using optimized ultrasonography in five wrist postures with and without a middle digit fingertip press (0, 6 N). Results. Both wrist posture and fingertip force had significant main effects on mean peak blood flow velocity. Blood flow velocity with a neutral wrist (2.87 cm/s) was significantly lower than flexed 30° (3.37 cm/s), flexed 15° (3.27 cm/s), and extended 30° (3.29 cm/s). Similarly, median nerve blood flow velocity was lower without force (2.81 cm/s) than with force (3.56 cm/s). A significant difference was not found between groups. Discussion. Vascular changes associated with CTS may be acutely induced by nonneutral wrist postures and fingertip force. This study represents an early evaluation of intraneural blood flow as a measure of nerve hypervascularization in response to occupational risk factors and advances our understanding of the vascular phenomena associated with peripheral nerve compression. PMID:28286771

  7. Metabolic and Cardiovascular Responses to Upright Cycle Exercise with Leg Blood Flow Reduction

    PubMed Central

    Ozaki, Hayao; Brechue, William F.; Sakamaki, Mikako; Yasuda, Tomohiro; Nishikawa, Masato; Aoki, Norikazu; Ogita, Futoshi; Abe, Takashi

    2010-01-01

    The purpose of this study was to examine the metabolic and cardiovascular response to exercise without (CON) or with (BFR) restricted blood flow to the muscles. Ten young men performed upright cycle exercise at 20, 40, and 60% of maximal oxygen uptake, VO2max in both conditions while metabolic and cardiovascular parameters were determined. Pre-exercise VO2 was not different between CON and BFR. Cardiac output (Q) was similar between the two conditions as a 25% reduction in stroke volume (SV) observed in BFR was associated with a 23% higher heart rate (HR) in BFR compared to CON. As a result rate-pressure product (RPP) was higher in the BFR but there was no difference in mean arterial pressure (MAP) or total peripheral resistance (TPR). During exercise, VO2 tended to increase with BFR (~10%) at each workload. Q increased in proportion to exercise intensity and there were no differences between conditions. The increase in SV with exercise was impaired during BFR; being ~20% lower in BFR at each workload. Both HR and RPP were significantly greater at each workload with BFR. MAP and TPR were greater with BFR at 40 and 60% VO2max. In conclusion, the BFR employed impairs exercise SV but central cardiovascular function is maintained by an increased HR. BFR appears to result in a greater energy demand during continuous exercise between 20 and 60% of control VO2max; probably indicated by a higher energy supply and RPP. When incorporating BFR, HR and RPP may not be valid or reliable indicators of exercise intensity. Key points Blood flow reduction (BFR) employed impairs stroke volume (SV) during exercise, but central cardiovascular function is maintained by an increased heart rate (HR). BFR appears to result in a greater energy demand during continuous exercise between 20 and 60% of control VO2max; Probably indicated by a higher energy supply (VO2) and rate-pressure product (HR x systolic blood pressure). PMID:24149689

  8. Hypopnea consequent to reduced pulmonary blood flow in the dog.

    PubMed

    Stremel, R W; Whipp, B J; Casaburi, R; Huntsman, D J; Wasserman, K

    1979-06-01

    The ventilatory responses to diminished pulmonary blood flow (Qc), as a result of partial cardiopulmonary bypass (PCB), were studied in chloralose-urethan-anesthetized dogs. Qc was reduced by diverting vena caval blood through a membrane gas exchanger and returning it to the ascending aorta. PCB flows of 400--1,600 ml/min were utilized for durations of 2--3 min. Decreasing Qc, while maintaining systemic arterial blood gases and perfusion, results in a significant (P less than 0.05) decrease in expiratory ventilation (VE) (15.9%) and alveolar ventilation (VA) (31.0%). The ventilatory decreases demonstrated for this intact group persist after bilateral cervical vagotomy (Vx), carotid body and carotid sinus denervation (Cx), and combined Vx and Cx. The changes in VE and VA were significantly (P less than 0.001) correlated with VCO2 changes, r = 0.80 and r = 0.93, respectively. These ventilatory changes were associated with an overall average decrease in left ventricular PCO2 of 2.1 Torr; this decrease was significant (P less than 0.05) only in the intact and Cx groups. Decreasing pulmonary blood flow results in a decrease in ventilation that may be CO2 related; however, the exact mechanism remains obscure but must have a component that is independent of vagally mediated cardiac and pulmonary afferents and peripheral baroreceptor and chemoreceptor afferents.

  9. Relationship between retinal blood flow and arterial oxygen

    PubMed Central

    Cheng, Richard W.; Yusof, Firdaus; Tsui, Edmund; Jong, Monica; Duffin, James; Flanagan, John G.; Fisher, Joseph A.

    2016-01-01

    Key points Vascular reactivity, the response of the vessels to a vasoactive stimulus such as hypoxia and hyperoxia, can be used to assess the vascular range of adjustment in which the vessels are able to compensate for changes in PO2.Previous studies in the retina have not accurately quantified retinal vascular responses and precisely targeted multiple PaO2 stimuli at the same time as controlling the level of carbon dioxide, thus precluding them from modelling the relationship between retinal blood flow and oxygen.The present study modelled the relationship between retinal blood flow and PaO2, showing them to be a combined linear and hyperbolic function.This model demonstrates that the resting tonus of the vessels is at the mid‐point and that they have great vascular range of adjustment, compensating for decreases in oxygen above a P ETC O2 of 32–37 mmHg but being limited below this threshold. Abstract Retinal blood flow (RBF) increases in response to a reduction in oxygen (hypoxia) but decreases in response to increased oxygen (hyperoxia). However, the relationship between blood flow and the arterial partial pressure of oxygen has not been quantified and modelled in the retina, particularly in the vascular reserve and resting tonus of the vessels. The present study aimed to determine the limitations of the retinal vasculature by modelling the relationship between RBF and oxygen. Retinal vascular responses were measured in 13 subjects for eight different blood gas conditions, with the end‐tidal partial pressure of oxygen (P ETC O2) ranging from 40–500 mmHg. Retinal vascular response measurements were repeated twice; using the Canon laser blood flowmeter (Canon Inc., Tokyo, Japan) during the first visit and using Doppler spectral domain optical coherence tomography during the second visit. We determined that the relationship between RBF and PaO2 can be modelled as a combination of hyperbolic and linear functions. We concluded that RBF compensated for

  10. CFD simulation of blood flow inside the corkscrew collaterals of the Buerger’s disease

    PubMed Central

    Sharifi, Alireza; Charjouei Moghadam, Mohammad

    2016-01-01

    Introduction: Buerger’s disease is an occlusive arterial disease that occurs mainly in medium and small vessels. This disease is associated with Tobacco usage. The existence of corkscrew collateral is one of the established characteristics of the Buerger’s disease. Methods: In this study, the computational fluid dynamics (CFD) simulation of blood flow within the corkscrew artery of the Buerger’s disease is conducted. The geometry of the artery is constructed based on the actual corkscrew artery of a patient diagnosed with the Buerger’s disease. The blood properties are the same as the actual blood properties of the patient. The blood flow rate is taken from the available experimental data in the literature. Results: The local velocity patterns, pressure and kinematic viscosity distributions in different segments of the corkscrew collateral artery was demonstrated and discussed for the first time for this kind of artery. The effects of non-Newtonian consideration for the blood viscosity behavior were investigated in different segments of the artery. Moreover, the variations of the blood flow patterns along the artery were investigated in details for each segment. Conclusion: It was found that the flow patterns were affected by the complex geometry of this artery in such a way that it could lead to the presence of sites that were prone to the accumulation of the flowing particles in blood like nicotine. Furthermore, due to the existence of many successive bends in this artery, the variations of kinematic viscosity along this artery were significant, therefore the non-Newtonian behavior of the blood viscosity must be considered. PMID:27340623

  11. Estimating Mechanical Blood Trauma in a Centrifugal Blood Pump: Laser Doppler Anemometer Measurements of the Mean Velocity Field.

    PubMed

    Pinotti, Marcos; Paone, Nicola

    1996-05-01

    A laser Doppler anemometer (LDA) was used to obtain the mean velocity and the Reynolds stress fields in the inner channels of a well-known centrifugal vaneless pump (Bio-pump). Effects of the excessive flow resistance against which an occlusive pump operates in some surgical situations, such as cardiopulmonary bypass, are illustrated. The velocity vector field obtained from LDA measurements reveals that the constraint-forced vortex provides pumping action in a restricted area in the core of the pump. In such situations, recirculating zones dominate the flow and consequently increase the damage to blood cells and raise the risk of thrombus formation in the device. Reynolds normal and shear stress fields were obtained in the entry flow for the channel formed by two rotating cones to illustrate the effects of flow disturbances on the potential for blood cell damage. © 1996 International Society for Artificial Organs.

  12. Can transmyocardial CO2 laser channels supply nutritive blood flow into adjacent myocardium?

    NASA Astrophysics Data System (ADS)

    Kohmoto, Takushi; Fisher, Peter E.; DeRosa, Carolyn; Smith, Craig R.; Burkhoff, Daniel

    1996-05-01

    Clinical reports of transmyocardial laser revascularization (TMLR) suggest that this procedure is effective in relieving angina. However, experimental evidence of nutritive blood flow through the TMLR channels is not available. The purpose of this study was to test whether blood could flow through the TMLR channels created with the carbon-dioxide laser.

  13. Numerical investigations of the unsteady blood flow in the end-to-side arteriovenous fistula for hemodialysis.

    PubMed

    Jodko, Daniel; Obidowski, Damian; Reorowicz, Piotr; Jóźwik, Krzysztof

    2016-01-01

    The aim of this study was to investigate the blood flow in the end-to-side arteriovenous (a-v) fistula, taking into account its pulsating nature and the patient-specific geometry of blood vessels. Computational Fluid Dynamics (CFD) methods were used for this analysis. DICOM images of the fistula, obtained from the angio-computed tomography, were a source of the data applied to develop a 3D geometrical model of the fistula. The model was meshed, then the ANSYS CFX v. 15.0 code was used to perform simulations of the flow in the vessels under analysis. Mesh independence tests were conducted. The non-Newtonian rheological model of blood and the Shear Stress Transport model of turbulence were employed. Blood vessel walls were assumed to be rigid. Flow patterns, velocity fields, the volume flow rate, the wall shear stress (WSS) propagation on particular blood vessel walls were shown versus time. The maximal value of the blood velocity was identified in the anastomosis - the place where the artery is connected to the vein. The flow rate was calculated for all veins receiving blood. The blood flow in the geometrically complicated a-v fistula was simulated. The values and oscillations of the WSS are the largest in the anastomosis, much lower in the artery and the lowest in the cephalic vein. A strong influence of the mesh on the results concerning the maximal and area-averaged WSS was shown. The relation between simulations of the pulsating and stationary flow under time-averaged flow conditions was presented.

  14. Blood Pump Development Using Rocket Engine Flow Simulation Technology

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin C.; Kwak, Dochan

    2002-01-01

    This viewgraph presentation provides information on the transfer of rocket engine flow simulation technology to work involving the development of blood pumps. Details are offered regarding the design and requirements of mechanical heart assist devices, or VADs (ventricular assist device). There are various computational fluid dynamics issues involved in the visualization of flow in such devices, and these are highlighted and compared to those of rocket turbopumps.

  15. Augmented uterine artery blood flow and oxygen delivery protect Andeans from altitude-associated reductions in fetal growth

    PubMed Central

    Julian, Colleen Glyde; Wilson, Megan J.; Lopez, Miriam; Yamashiro, Henry; Tellez, Wilma; Rodriguez, Armando; Bigham, Abigail W.; Shriver, Mark D.; Rodriguez, Carmelo; Vargas, Enrique; Moore, Lorna G.

    2009-01-01

    The effect of high altitude on reducing birth weight is markedly less in populations of high- (e.g., Andeans) relative to low-altitude origin (e.g., Europeans). Uterine artery (UA) blood flow is greater during pregnancy in Andeans than Europeans at high altitude; however, it is not clear whether such blood flow differences play a causal role in ancestry-associated variations in fetal growth. We tested the hypothesis that greater UA blood flow contributes to the protection of fetal growth afforded by Andean ancestry by comparing UA blood flow and fetal growth throughout pregnancy in 137 Andean or European residents of low (400 m; European n = 28, Andean n = 23) or high (3,100–4,100 m; European n = 51, Andean n = 35) altitude in Bolivia. Blood flow and fetal biometry were assessed by Doppler ultrasound, and maternal ancestry was confirmed, using a panel of 100 ancestry-informative genetic markers (AIMs). At low altitude, there were no ancestry-related differences in the pregnancy-associated rise in UA blood flow, fetal biometry, or birth weight. At high altitude, Andean infants weighed 253 g more than European infants after controlling for gestational age and other known influences. UA blood flow and O2 delivery were twofold greater at 20 wk in Andean than European women at high altitude, and were paralleled by greater fetal size. Moreover, variation in the proportion of Indigenous American ancestry among individual women was positively associated with UA diameter, blood flow, O2 delivery, and fetal head circumference. We concluded that greater UA blood flow protects against hypoxia-associated reductions in fetal growth, consistent with the hypothesis that genetic factors enabled Andeans to achieve a greater pregnancy-associated rise in UA blood flow and O2 delivery than European women at high altitude. PMID:19244584

  16. Pulpal blood flow recorded from human premolar teeth with a laser Doppler flow meter using either red or infrared light.

    PubMed

    Kijsamanmith, Kanittha; Timpawat, Siriporn; Vongsavan, Noppakun; Matthews, Bruce

    2011-07-01

    To compare red (635 nm) and infrared (780 nm) light for recording pulpal blood flow from human premolar teeth. Recordings were made from 11 healthy teeth in 9 subjects (aged 16-30 years) using a laser Doppler flow meter (Periflux 4001) equipped with both red and infrared lasers. Average blood flow signals were obtained with both light sources alternately from each tooth under five conditions: intact tooth without opaque rubber dam, intact tooth with dam, after injecting local anaesthetic (3% Mepivacaine) (LA) over the apex of the tooth and cavity preparation to almost expose the pulp, after removal and replacement of the pulp, and with the root canal empty. With infrared light, the dam significantly decreased the mean blood flow by 80%. Injecting LA and cavity preparation had no significant effect. Removal and replacement of the pulp reduced the mean blood flow by 58%. There was no further change when the pulp was removed. With red light, the dam reduced the signal from intact teeth by 60%. Injecting LA and cavity preparation had no significant effect. The signal fell by 67% after pulp removal and replacement and did not change significantly when the pulp was removed. Opaque rubber dam minimises the contribution of non-pulpal tissues to the laser Doppler signal recorded from premolars. Using dam, the pulp contributed about 60% to the blood flow signal with both red and infrared light. The difference between them in this respect was not significant. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Laser Doppler flowmetry for measurement of laminar capillary blood flow in the horse

    NASA Astrophysics Data System (ADS)

    Adair, Henry S., III

    1998-07-01

    Current methods for in vivo evaluation of digital hemodynamics in the horse include angiography, scintigraphy, Doppler ultrasound, electromagnetic flow and isolated extracorporeal pump perfused digit preparations. These techniques are either non-quantifiable, do not allow for continuous measurement, require destruction of the horse orare invasive, inducing non- physiologic variables. In vitro techniques have also been reported for the evaluation of the effects of vasoactive agents on the digital vessels. The in vitro techniques are non-physiologic and have evaluated the vasculature proximal to the coronary band. Lastly, many of these techniques require general anesthesia or euthanasia of the animal. Laser Doppler flowmetry is a non-invasive, continuous measure of capillary blood flow. Laser Doppler flowmetry has been used to measure capillary blood flow in many tissues. The principle of this method is to measure the Doppler shift, that is, the frequency change that light undergoes when reflected by moving objects, such as red blood cells. Laser Doppler flowmetry records a continuous measurement of the red cell motion in the outer layer of the tissue under study, with little or no influence on physiologic blood flow. This output value constitutes the flux of red cells and is reported as capillary perfusion units. No direct information concerning oxygen, nutrient or waste metabolite exchange in the surrounding tissue is obtained. The relationship between the flowmeter output signal and the flux of red blood cells is linear. The principles of laser Doppler flowmetry will be discussed and the technique for laminar capillary blood flow measurements will be presented.

  18. Proteins and antibodies in serum, plasma, and whole blood-size characterization using asymmetrical flow field-flow fractionation (AF4).

    PubMed

    Leeman, Mats; Choi, Jaeyeong; Hansson, Sebastian; Storm, Matilda Ulmius; Nilsson, Lars

    2018-05-29

    The analysis of aggregates of therapeutic proteins is crucial in order to ensure efficacy and patient safety. Typically, the analysis is performed in the finished formulation to ensure that aggregates are not present. An important question is, however, what happens to therapeutic proteins, with regard to oligomerization and aggregation, after they have been administrated (i.e., in the blood). In this paper, the separation of whole blood, plasma, and serum is shown using asymmetric flow field-flow fractionation (AF4) with a minimum of sample pre-treatment. Furthermore, the analysis and size characterization of a fluorescent antibody in blood plasma using AF4 are demonstrated. The results show the suitability and strength of AF4 for blood analysis and open new important routes for the analysis and characterization of therapeutic proteins in the blood.

  19. Activation of somatosensory afferents elicit changes in vaginal blood flow and the urethrogenital reflex via autonomic efferents.

    PubMed

    Cai, R S; Alexander, M Sipski; Marson, L

    2008-09-01

    We examined the effects of pudendal sensory nerve stimulation and urethral distention on vaginal blood flow and the urethrogenital reflex, and the relationship between somatic and autonomic pathways regulating sexual responses. Distention of the urethra and stimulation of the pudendal sensory nerve were used to evoke changes in vaginal blood flow (laser Doppler perfusion monitoring) and pudendal motor nerve activity in anesthetized, spinally transected female rats. Bilateral cuts of either the pelvic or hypogastric nerve or both autonomic nerves were made, and blood flow and pudendal nerve responses were reexamined. Stimulation of the pudendal sensory nerve or urethral distention elicited consistent increases in vaginal blood flow and rhythmic firing of the pudendal motor nerve. Bilateral cuts of the pelvic plus hypogastric nerves significantly reduced vaginal blood flow responses without altering pudendal motor nerve responses. Pelvic nerve cuts also significantly reduced vaginal blood flow responses. In contrast, hypogastric nerve cuts did not significantly change vaginal blood flow. Bilateral cuts of the pudendal sensory nerve blocked pudendal motor nerve responses but stimulation of the central end evoked vaginal blood flow and pudendal motor nerve responses. Stimulation of the sensory branch of the pudendal nerve elicits vasodilatation of the vagina. The likely mechanism is via activation of spinal pathways that in turn activate pelvic nerve efferents to produced changes in vaginal blood flow. Climatic-like responses (firing of the pudendal motor nerve) occur in response to stimulation of the pudendal sensory nerve and do not require intact pelvic or hypogastric nerves.

  20. Effects of hyperbaric oxygen on intracranial pressure and cerebral blood flow in experimental cerebral oedema1

    PubMed Central

    Miller, J. D.; Ledingham, I. McA.; Jennett, W. B.

    1970-01-01

    Increased intracranial pressure was induced in anaesthetized dogs by application of liquid nitrogen to the dura mater. Intracranial pressure and cerebral blood flow were measured, together with arterial blood pressure and arterial and cerebral venous blood gases. Carbon dioxide was administered intermittently to test the responsiveness of the cerebral circulation, and hyperbaric oxygen was delivered at intervals in a walk-in hyperbaric chamber, pressurized to two atmospheres absolute. Hyperbaric oxygen caused a 30% reduction of intracranial pressure and a 19% reduction of cerebral blood flow in the absence of changes in arterial PCO2 or blood pressure, but only as long as administration of carbon dioxide caused an increase in both intracranial pressure and cerebral blood flow. When carbon dioxide failed to influence intracranial pressure or cerebral blood flow then hyperbaric oxygen had no effect. This unresponsive state was reached at high levels of intracranial pressure. Images PMID:5497875