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  1. Intraperitoneal Resuscitation Improves Intestinal Blood Flow Following Hemorrhagic Shock

    PubMed Central

    Zakaria, El Rasheid; Garrison, R. Neal; Spain, David A.; Matheson, Paul J.; Harris, Patrick D.; Richardson, J. David

    2003-01-01

    Objective To study the effects of peritoneal resuscitation from hemorrhagic shock. Summary Background Data Methods for conventional resuscitation (CR) from hemorrhagic shock (HS) often fail to restore adequate intestinal blood flow, and intestinal ischemia has been implicated in the activation of the inflammatory response. There is clinical evidence that intestinal hypoperfusion is a major factor in progressive organ failure following HS. This study presents a novel technique of peritoneal resuscitation (PR) that improves visceral perfusion. Methods Male Sprague-Dawley rats were bled to 50% of baseline mean arterial pressure (MAP) and resuscitated with shed blood plus 2 equal volumes of saline (CR). Groups were 1) sham, 2) HS + CR, and 3) HS + CR + PR with a hyperosmolar dextrose-based solution (Delflex 2.5%). Groups 1 and 2 had normal saline PR. In vivo videomicroscopy and Doppler velocimetry were used to assess terminal ileal microvascular blood flow. Endothelial cell function was assessed by the endothelium-dependent vasodilator acetylcholine. Results Despite restored heart rate and MAP to baseline values, CR animals developed a progressive intestinal vasoconstriction and tissue hypoperfusion compared to baseline flow. PR induced an immediate and sustained vasodilation compared to baseline and a marked increase in average intestinal blood flow during the entire 2-hour post-resuscitation period. Endothelial-dependent dilator function was preserved with PR. Conclusions Despite the restoration of MAP with blood and saline infusions, progressive vasoconstriction and compromised intestinal blood flow occurs following HS/CR. Hyperosmolar PR during CR maintains intestinal blood flow and endothelial function. This is thought to be a direct effect of hyperosmolar solutions on the visceral microvessels. The addition of PR to a CR protocol prevents the splanchnic ischemia that initiates systemic inflammation. PMID:12724637

  2. Improvement in Myocardial Function and Coronary Blood Flow in Ischemic Myocardium after Mannitol

    PubMed Central

    Willerson, James T.; Powell, Wm. John; Guiney, Timothy E.; Stark, James J.; Sanders, Charles A.; Leaf, Alexander

    1972-01-01

    The purpose of this study was to evaluate the effect of hyperosmolality on the performance of, and the collateral blood flow to, ischemic myocardium. The myocardial response to mannitol, a hyperosmolar agent which remains extracellular, was evaluated in anesthetized dogs. Mannitol was infused into the aortic roots of 31 isovolumic hearts and of 15 dogs on right heart bypass, before and during ischemia. Myocardial ischemia was produced by temporary ligation of either the proximal or mid-left anterior descending coronary artery. Mannitol significantly improved the depressed ventricular function curves which occurred with left anterior descending coronary artery occlusion. Mannitol also significantly lessened the S-T segment elevation (epicardial electrocardiogram) occurring during myocardial ischemia in the isovolumic hearts and this reduction was associated with significant increases in total coronary blood flow (P < 0.005) and with increased collateral coronary blood flow to the ischemia area (P < 0.005). Thus, increases in serum osmolality produced by mannitol result in the following beneficial changes during myocardial ischemia: (a) improved myocardial function, (b) reduced S-T segment elevation, (c) increased total coronary blood flow, and (d) increased collateral coronary blood flow. PMID:4640943

  3. Blood flow

    MedlinePlus Videos and Cool Tools

    As the heart pumps, the arteries carry oxygen-rich blood (shown in red) away from the heart and toward the body’s tissues and ... returns to the heart from the lungs, which pumps it throughout the body.

  4. Blood flow

    MedlinePlus Videos and Cool Tools

    As the heart pumps, the arteries carry oxygen-rich blood (shown in red) away from the heart and toward the body's tissues and vital organs. ... brain, liver, kidneys, stomach, and muscles, including the heart muscle itself. At the same time, the veins ...

  5. Effects of terlipressin on patients with sepsis via improving tissue blood flow.

    PubMed

    Xiao, Xudong; Zhang, Jie; Wang, Yaoli; Zhou, Jian; Zhu, Yu; Jiang, Dongpo; Liu, Liangming; Li, Tao

    2016-01-01

    Terlipressin (TP), an analog of arginine vasopressin, was reported beneficial in sepsis patients when combined use with norepinephrine (NE), but the undetermined action, mechanism, and safety limited it to become the first-line vasopressor for sepsis patients. With 32 septic shock patients, we investigated the effects of a small dose of TP (1.3 μg/kg/h) on hemodynamic, tissue blood flow, vital organ function, acid-base balance, and coagulation function to systemically know the beneficial effect and side effects of TP on septic shock. The results showed that as compared with the single use of NE group (17 patients), a small dose of TP (1.3 μg/kg/h) in combination with NE continuous infusion, except for decreasing the mortality and NE requirement, could better improve and stabilize the hemodynamics, improve the tissue blood flow, increase the blood oxygen saturation and urine volume, and decrease the lactate level and complication rate (47% versus 82.3% in NE group). Meanwhile, TP + NE did not induce blood bilirubin increase and platelet count decrease and hyponatremia that vasopressin has. The results show that low dose of TP continuous infusion can help NE achieve the good resuscitation effect by improving tissue blood flow, stabilizing hemodynamics, and protecting organ function in septic shock patients while did not induce the side effects that high dose or bonus of TP or vasopressin induced. Low dose of TP may be recommended as the first-line vasopressor for refractory hypotension after severe sepsis or septic shock. PMID:26253455

  6. Perilla oil improves blood flow through inhibition of platelet aggregation and thrombus formation

    PubMed Central

    Jang, Ja-Young; Kim, Tae-Su; Cai, Jingmei; Kim, Jihyun; Kim, Youngeun; Shin, Kyungha; Kim, Kwang-Sei; Lee, Sung-Pyo; Kang, Myung-Hwa; Choi, Ehn-Kyoung

    2014-01-01

    The inhibitory effects of perilla oil on the platelet aggregation in vitro and thrombosis in vivo were investigated in comparison with aspirin, a well-known blood flow enhancer. Rabbit platelet-rich plasma was incubated with perilla oil and aggregation inducers collagen or thrombin, and the platelet aggregation rate was analyzed. Perilla oil significantly inhibited both the collagen- and thrombin-induced platelet aggregations, in which the thromboxane B2 formation from collagen-activated platelets were reduced in a concentration-dependent manner. Rats were administered once daily by gavage with perilla oil for 1 week, carotid arterial thrombosis was induced by applying 35% FeCl3-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Perilla oil delayed the FeCl3-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 0.5 mL/kg. In addition, a high dose (2 mL/kg) of perilla oil greatly prevented the occlusion, comparable to the effect of aspirin (30 mg/kg). The results indicate that perilla oil inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is proposed that perilla oil could be a good candidate without adverse effects for the improvement of blood flow. PMID:24707301

  7. CD4+ LYMPHOCYTES IMPROVE VENOUS BLOOD FLOW IN EXPERIMENTAL ARTERIOVENOUS FISTULAE

    PubMed Central

    Duque, Juan C.; Martinez, Laisel; Mesa, Annia; Wei, Yuntao; Tabbara, Marwan; Salman, Loay H.; Vazquez-Padron, Roberto I.

    2015-01-01

    Background The role of immune cells in arteriovenous fistulae (AVF) maturation is poorly understood and has received, until quite recently, little attention. This study examines the role of T lymphocytes in AVF vascular remodeling. Methods Experimental fistulae were created in athymic rnu nude rats lacking mature T lymphocytes and euthymic control animals by anastomosing the left superior epigastric vein to the nearby femoral artery. Blood flow rates, wall morphology and histological changes were assessed in AVF 21 days after creation. The effect of CD4+ lymphocytes on AVF maturation in athymic animals was analyzed by adoptive transfer of cells after fistula creation. Results The absence of T lymphocytes compromised blood flow in experimental fistulae. Histopathological inspection of AVF from athymic rats revealed that T cell immunodeficiency negatively affected venous vascular remodeling, as evidenced by a reduced lumen, a thick muscular layer and a low number of inflammatory cells compared to control animals. Adoptive transfer of CD4+ lymphocytes from euthymic rats into athymic animals before and after fistula creation improved blood flow and reduced intima-media thickness. Conclusion These results point at the protective role of CD4+ lymphocytes in the remodeling of the AVF vascular wall. PMID:25999254

  8. Enhanced Efficacy of Doxorubicin by microRNA-499-Mediated Improvement of Tumor Blood Flow

    PubMed Central

    Okamoto, Ayaka; Asai, Tomohiro; Ryu, Sho; Ando, Hidenori; Maeda, Noriyuki; Dewa, Takehisa; Oku, Naoto

    2016-01-01

    Genetic therapy using microRNA-499 (miR-499) was combined with chemotherapy for the advanced treatment of cancer. Our previous study showed that miR-499 suppressed tumor growth through the inhibition of vascular endothelial growth factor (VEGF) production and subsequent angiogenesis. In the present study, we focused on blood flow in tumors treated with miR499, since some angiogenic vessels are known to lack blood flow. Tetraethylenepentamine-based polycation liposomes (TEPA-PCL) were prepared and modified with Ala-Pro-Arg-Pro-Gly peptide (APRPG) for targeted delivery of miR-499 (APRPG-miR-499) to angiogenic vessels and tumor cells. The tumor blood flow was significantly improved, so-called normalized, after systemic administration of APRPG-miR-499 to Colon 26 NL-17 carcinoma–bearing mice. In addition, the accumulation of doxorubicin (DOX) in the tumors was increased by pre-treatment with APRPG-miR-499. Moreover, the combination therapy of APRPG-miR-499 and DOX resulted in significant suppression of the tumors. Taken together, our present data indicate that miR-499 delivered with APRPG-modified-TEPA-PCL normalized tumor vessels, resulting in enhancement of intratumoral accumulation of DOX. Our findings suggest that APRPG-miR-499 may be a therapeutic, or a combination therapeutic, candidate for cancer treatment. PMID:26797645

  9. Enhanced Efficacy of Doxorubicin by microRNA-499-Mediated Improvement of Tumor Blood Flow.

    PubMed

    Okamoto, Ayaka; Asai, Tomohiro; Ryu, Sho; Ando, Hidenori; Maeda, Noriyuki; Dewa, Takehisa; Oku, Naoto

    2016-01-01

    Genetic therapy using microRNA-499 (miR-499) was combined with chemotherapy for the advanced treatment of cancer. Our previous study showed that miR-499 suppressed tumor growth through the inhibition of vascular endothelial growth factor (VEGF) production and subsequent angiogenesis. In the present study, we focused on blood flow in tumors treated with miR499, since some angiogenic vessels are known to lack blood flow. Tetraethylenepentamine-based polycation liposomes (TEPA-PCL) were prepared and modified with Ala-Pro-Arg-Pro-Gly peptide (APRPG) for targeted delivery of miR-499 (APRPG-miR-499) to angiogenic vessels and tumor cells. The tumor blood flow was significantly improved, so-called normalized, after systemic administration of APRPG-miR-499 to Colon 26 NL-17 carcinoma-bearing mice. In addition, the accumulation of doxorubicin (DOX) in the tumors was increased by pre-treatment with APRPG-miR-499. Moreover, the combination therapy of APRPG-miR-499 and DOX resulted in significant suppression of the tumors. Taken together, our present data indicate that miR-499 delivered with APRPG-modified-TEPA-PCL normalized tumor vessels, resulting in enhancement of intratumoral accumulation of DOX. Our findings suggest that APRPG-miR-499 may be a therapeutic, or a combination therapeutic, candidate for cancer treatment. PMID:26797645

  10. Improved instrumentation for blood flow velocity measurements in the microcirculation of small animals

    NASA Astrophysics Data System (ADS)

    de Mesquita, Jayme Alves; Bouskela, Eliete; Wajnberg, Eliane; de Melo, Pedro Lopes

    2007-02-01

    Microcirculation is the generic name of vessels with internal diameter less than 100μm of the circulatory system, whose main functions are tissue nutrition and oxygen supply. In microcirculatory studies, it is important to know the amount of oxyhemoglobin present in the blood and how fast it is moving. The present work describes improvements introduced in a classical hardware-based instrument that has usually been used to monitor blood flow velocity in the microcirculation of small animals. It consists of a virtual instrument that can be easily incorporated into existing hardware-based systems, contributing to reduce operator related biases and allowing digital processing and storage. The design and calibration of the modified instrument are described as well as in vitro and in vivo results obtained with electrical models and small animals, respectively. Results obtained in in vivo studies showed that this new system is able to detect a small reduction in blood flow velocity comparing arteries and arterioles (p<0.002) and a further reduction in capillaries (p<0.0001). A significant increase in velocity comparing capillaries and venules (p<0.001) and venules and veins (p<0.001) was also observed. These results are in close agreement with biophysical principles. Moreover, the improvements introduced in the device allowed us to clearly observe changes in blood flow introduced by a pharmacological intervention, suggesting that the system has enough temporal resolution to track these microcirculatory events. These results were also in close conformity to physiology, confirming the high scientific potential of the modified system and indicating that this instrument can also be useful for pharmacological evaluations.

  11. Improved instrumentation for blood flow velocity measurements in the microcirculation of small animals

    SciTech Connect

    Mesquita, Jayme Alves Jr. de; Bouskela, Eliete; Wajnberg, Eliane; Lopes de Melo, Pedro

    2007-02-15

    Microcirculation is the generic name of vessels with internal diameter less than 100 {mu}m of the circulatory system, whose main functions are tissue nutrition and oxygen supply. In microcirculatory studies, it is important to know the amount of oxyhemoglobin present in the blood and how fast it is moving. The present work describes improvements introduced in a classical hardware-based instrument that has usually been used to monitor blood flow velocity in the microcirculation of small animals. It consists of a virtual instrument that can be easily incorporated into existing hardware-based systems, contributing to reduce operator related biases and allowing digital processing and storage. The design and calibration of the modified instrument are described as well as in vitro and in vivo results obtained with electrical models and small animals, respectively. Results obtained in in vivo studies showed that this new system is able to detect a small reduction in blood flow velocity comparing arteries and arterioles (p<0.002) and a further reduction in capillaries (p<0.0001). A significant increase in velocity comparing capillaries and venules (p<0.001) and venules and veins (p<0.001) was also observed. These results are in close agreement with biophysical principles. Moreover, the improvements introduced in the device allowed us to clearly observe changes in blood flow introduced by a pharmacological intervention, suggesting that the system has enough temporal resolution to track these microcirculatory events. These results were also in close conformity to physiology, confirming the high scientific potential of the modified system and indicating that this instrument can also be useful for pharmacological evaluations.

  12. Single Limb Exercise Induces Femoral Artery Remodeling and Improves Blood Flow in the Hemiparetic Leg Post-Stroke

    PubMed Central

    Billinger, Sandra A.; Gajewski, Byron J.; Guo, Lisa X.; Kluding, Patricia M.

    2009-01-01

    Background and Purpose After stroke, individuals have decreased mobility of the hemiparetic leg, which demands less muscle oxygen consumption; thus, blood flow decreases. The purpose of this study was to determine the effect of single limb exercise (SLE) on femoral artery blood flow, diameter and peak flow velocity in the hemiparetic leg after stroke. Methods Twelve individuals (60.6 ± 14.5 years of age; 5 male) with chronic stroke (69.1 ± 82.2 months; 5 with right-side hemiparesis) participated in the study. The intervention consisted of a SLE knee extension/flexion protocol three times per week for 4 weeks. Using Doppler ultrasound, bilateral femoral artery blood flow, diameter and peak flow velocity was assessed at baseline, after 2 weeks and after 4 weeks of SLE. Results Using repeated measures ANOVA, femoral artery blood flow, arterial diameter, and blood flow velocity in the hemiparetic limb were significantly improved (p < 0.0001) after the SLE. No significant changes occurred in the non-trained limb for any outcome measures. Conclusions These data suggest that a 4-week SLE training program that increases muscular activity in the hemiparetic limb improves femoral artery blood flow, diameter, and peak velocity. SLE may be an important training strategy in stroke rehabilitation to minimize the vascular changes that occur post-stroke due to decreased activity of the hemiparetic limb. PMID:19520990

  13. Nattokinase improves blood flow by inhibiting platelet aggregation and thrombus formation.

    PubMed

    Jang, Ja-Young; Kim, Tae-Su; Cai, Jingmei; Kim, Jihyun; Kim, Youngeun; Shin, Kyungha; Kim, Kwang Sei; Park, Sung Kyeong; Lee, Sung-Pyo; Choi, Ehn-Kyoung; Rhee, Man Hee; Kim, Yun-Bae

    2013-12-01

    The effects of nattokinase on the in vitro platelet aggregation and in vivo thrombosis were investigated in comparison with aspirin. Rabbit platelet-rich plasma was incubated with nattokinase and aggregation inducers collagen and thrombin, and the platelet aggregation rate was analyzed. Nattokinase significantly inhibited both the collagen- and thrombin-induced platelet aggregations. Nattokinase also reduced thromboxane B2 formation from collagen-activated platelets in a concentration-dependent manner. Rats were orally administered with nattokinase for 1 week, and their carotid arteries were exposed. Arterial thrombosis was induced by applying 35% FeCl3-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Nattokinase delayed the FeCl3-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 160 mg/kg. In addition, a high dose (500 mg/kg) of nattokinase fully prevented the occlusion, as achieved with aspirin (30 mg/kg). The results indicate that nattokinase extracted from fermented soybean inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is suggested that nattokinase could be a good candidate without adverse effects for the improvement of blood flow. PMID:24396387

  14. Nattokinase improves blood flow by inhibiting platelet aggregation and thrombus formation

    PubMed Central

    Jang, Ja-Young; Kim, Tae-Su; Cai, Jingmei; Kim, Jihyun; Kim, Youngeun; Shin, Kyungha; Kim, Kwang Sei; Park, Sung Kyeong; Lee, Sung-Pyo; Choi, Ehn-Kyoung

    2013-01-01

    The effects of nattokinase on the in vitro platelet aggregation and in vivo thrombosis were investigated in comparison with aspirin. Rabbit platelet-rich plasma was incubated with nattokinase and aggregation inducers collagen and thrombin, and the platelet aggregation rate was analyzed. Nattokinase significantly inhibited both the collagen- and thrombin-induced platelet aggregations. Nattokinase also reduced thromboxane B2 formation from collagen-activated platelets in a concentration-dependent manner. Rats were orally administered with nattokinase for 1 week, and their carotid arteries were exposed. Arterial thrombosis was induced by applying 35% FeCl3-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Nattokinase delayed the FeCl3-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 160 mg/kg. In addition, a high dose (500 mg/kg) of nattokinase fully prevented the occlusion, as achieved with aspirin (30 mg/kg). The results indicate that nattokinase extracted from fermented soybean inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is suggested that nattokinase could be a good candidate without adverse effects for the improvement of blood flow. PMID:24396387

  15. Blood flow dynamic improvement with aneurysm repair detected by a patient-specific model of multiple aortic aneurysms.

    PubMed

    Sughimoto, Koichi; Takahara, Yoshiharu; Mogi, Kenji; Yamazaki, Kenji; Tsubota, Ken'ichi; Liang, Fuyou; Liu, Hao

    2014-05-01

    Aortic aneurysms may cause the turbulence of blood flow and result in the energy loss of the blood flow, while grafting of the dilated aorta may ameliorate these hemodynamic disturbances, contributing to the alleviation of the energy efficiency of blood flow delivery. However, evaluating of the energy efficiency of blood flow in an aortic aneurysm has been technically difficult to estimate and not comprehensively understood yet. We devised a multiscale computational biomechanical model, introducing novel flow indices, to investigate a single male patient with multiple aortic aneurysms. Preoperative levels of wall shear stress and oscillatory shear index (OSI) were elevated but declined after staged grafting procedures: OSI decreased from 0.280 to 0.257 (first operation) and 0.221 (second operation). Graftings may strategically counter the loss of efficient blood delivery to improve hemodynamics of the aorta. The energy efficiency of blood flow also improved postoperatively. Novel indices of pulsatile pressure index (PPI) and pulsatile energy loss index (PELI) were evaluated to characterize and quantify energy loss of pulsatile blood flow. Mean PPI decreased from 0.445 to 0.423 (first operation) and 0.359 (second operation), respectively; while the preoperative PELI of 0.986 dropped to 0.820 and 0.831. Graftings contributed not only to ameliorate wall shear stress or oscillatory shear index but also to improve efficient blood flow. This patient-specific modeling will help in analyzing the mechanism of aortic aneurysm formation and may play an important role in quantifying the energy efficiency or loss in blood delivery. PMID:23852404

  16. Oral antioxidants improve leg blood flow during exercise in patients with chronic obstructive pulmonary disease.

    PubMed

    Rossman, Matthew J; Trinity, Joel D; Garten, Ryan S; Ives, Stephen J; Conklin, Jamie D; Barrett-O'Keefe, Zachary; Witman, Melissa A H; Bledsoe, Amber D; Morgan, David E; Runnels, Sean; Reese, Van R; Zhao, Jia; Amann, Markus; Wray, D Walter; Richardson, Russell S

    2015-09-01

    The consequence of elevated oxidative stress on exercising skeletal muscle blood flow as well as the transport and utilization of O2 in patients with chronic obstructive pulmonary disease (COPD) is not well understood. The present study examined the impact of an oral antioxidant cocktail (AOC) on leg blood flow (LBF) and O2 consumption during dynamic exercise in 16 patients with COPD and 16 healthy subjects. Subjects performed submaximal (3, 6, and 9 W) single-leg knee extensor exercise while LBF (Doppler ultrasound), mean arterial blood pressure, leg vascular conductance, arterial O2 saturation, leg arterial-venous O2 difference, and leg O2 consumption (direct Fick) were evaluated under control conditions and after AOC administration. AOC administration increased LBF (3 W: 1,604 ± 100 vs. 1,798 ± 128 ml/min, 6 W: 1,832 ± 109 vs. 1,992 ± 120 ml/min, and 9W: 2,035 ± 114 vs. 2,187 ± 136 ml/min, P < 0.05, control vs. AOC, respectively), leg vascular conductance, and leg O2 consumption (3 W: 173 ± 12 vs. 210 ± 15 ml O2/min, 6 W: 217 ± 14 vs. 237 ± 15 ml O2/min, and 9 W: 244 ± 16 vs 260 ± 18 ml O2/min, P < 0.05, control vs. AOC, respectively) during exercise in COPD, whereas no effect was observed in healthy subjects. In addition, the AOC afforded a small, but significant, improvement in arterial O2 saturation only in patients with COPD. Thus, these data demonstrate a novel beneficial role of AOC administration on exercising LBF, O2 consumption, and arterial O2 saturation in patients with COPD, implicating oxidative stress as a potential therapeutic target for impaired exercise capacity in this population. PMID:26188020

  17. Improvement of the accuracy of continuous hematocrit measurement under various blood flow conditions

    NASA Astrophysics Data System (ADS)

    Kim, Myounggon; Yang, Sung

    2014-04-01

    We propose an accurate method for continuous hematocrit (HCT) measurement of flowing blood under varying plasma conditions of electrical conductivity, osmolality, and flow rate. Two parameters, namely the hematocrit estimation parameter (HEP) and normalized difference, are proposed to reduce the HCT measurement error. HEP was demonstrated in a previous work. The results of multiple linear regression analysis showed that the two parameters were strongly correlated with the reference HCT measured by microcentrifugation. The measurement error was less than 9% despite significant simultaneous variations in the plasma properties and shear rate.

  18. Patient-specific blood flow simulation to improve intracranial aneurysm diagnosis

    NASA Astrophysics Data System (ADS)

    Fenz, Wolfgang; Dirnberger, Johannes

    2011-03-01

    We present a novel simulation system of blood flow through intracranial aneurysms including the interaction between blood lumen and vessel tissue. It provides the means to estimate rupture risks by calculating the distribution of pressure and shear stresses in the aneurysm, in order to support the planning of clinical interventions. So far, this has only been possible with commercial simulation packages originally targeted at industrial applications, whereas our implementation focuses on the intuitive integration into clinical workflow. Due to the time-critical nature of the application, we exploit most efficient state-of-the-art numerical methods and technologies together with high performance computing infrastructures (Austrian Grid). Our system builds a three-dimensional virtual replica of the patient's cerebrovascular system from X-ray angiography, CT or MR images. The physician can then select a region of interest which is automatically transformed into a tetrahedral mesh. The differential equations for the blood flow and the wall elasticity are discretized via the finite element method (FEM), and the resulting linear equation systems are handled by an algebraic multigrid (AMG) solver. The wall displacement caused by the blood pressure is calculated using an iterative fluid-structure interaction (FSI) algorithm, and the fluid mesh is deformed accordingly. First simulation results on measured patient geometries show good medical relevance for diagnostic decision support.

  19. Mechanics of blood flow.

    PubMed

    Skalak, R; Keller, S R; Secomb, T W

    1981-05-01

    The historical development of the mechanics of blood flow can be traced from ancient times, to Leonardo da Vinci and Leonhard Euler and up to the present times with increasing biological knowledge and mathematical analysis. In the last two decades, quantitative and numerical methods have steadily given more complete and precise understanding. In the arterial system wave propagation computations based on nonlinear one-dimensional modeling have given the best representation of pulse wave propagation. In the veins, the theory of unsteady flow in collapsible tubes has recently been extensively developed. In the last decade, progress has been made in describing the blood flow at junctions, through stenoses, in bends and in capillary blood vessels. The rheological behavior of individual red blood cells has been explored. A working model consists of an elastic membrane filled with viscous fluid. This model forms a basis for understanding the viscous and viscoelastic behavior of blood. PMID:7024641

  20. Delayed Treatment with Sodium Hydrosulfide Improves Regional Blood Flow and Alleviates Cecal Ligation and Puncture (CLP)-Induced Septic Shock.

    PubMed

    Ahmad, Akbar; Druzhyna, Nadiya; Szabo, Csaba

    2016-08-01

    oxidative stress) in heart as well as in liver and myeloperoxidase levels (an index of neutrophil infiltration) in heart and lung. Plasma levels of IL-1β, IL-5, IL-6, TNF-α, and HMGB1 were attenuated by NaHS. Treatment of NaHS at 3 mg/kg i.p. (but not 1 mg/kg or 6 mg/kg), starting 24 h post-CLP, with dosing repeated every 6 h, improved the survival rate in CLP animals. In summary, treatment with 3 mg/kg H2S-when started in a delayed manner, when CLP-induced organ injury, inflammation and blood flow redistribution have already ensued-improves blood flow to several organs, protects against multiple organ failure, and reduces the plasma levels of multiple pro-inflammatory mediators. These findings support the view that H2S donation may have therapeutic potential in sepsis. PMID:26863032

  1. Quantification of myocardial blood flow using PET to improve the management of patients with stable ischemic coronary artery disease.

    PubMed

    Ohira, Hiroshi; Dowsley, Taylor; Dwivedi, Girish; deKemp, Robert A; Chow, Benjamin J; Ruddy, Terrence D; Davies, Ross A; DaSilva, Jean; Beanlands, Rob S B; Hessian, Renee

    2014-09-01

    Cardiac PET has been evolving over the past 30 years. Today, it is accepted as a valuable imaging modality for the noninvasive assessment of coronary artery disease. PET has demonstrated superior diagnostic accuracy for the detection of coronary artery disease compared with single-photon emission computed tomography, and also has a well-established prognostic value. The routine addition of absolute quantification of myocardial blood flow increases the diagnostic accuracy for three-vessel disease and provides incremental functional and prognostic information. Moreover, the characterization of the vasodilator capacity of the coronary circulation may guide proper decision-making and monitor the effects of lifestyle changes, exercise training, risk factor modification or medical therapy for improving regional and global myocardial blood flow. This type of image-guided approach to individualized patient therapy is now attainable with the routine use of cardiac PET flow reserve imaging. PMID:25354033

  2. Tissue blood flow mapping

    NASA Astrophysics Data System (ADS)

    Nilsson, G. E.

    1997-01-01

    The operating principles of Laser Doppler Perfusion Imaging (LDPI) for visualization of the tissue blood perfusion are explained. Using this emerging technology skin perfusion has been investigated in healthy volunteers and in patients with various conditions that affect skin blood flow. LDPI is anticipated to be particularly useful in evaluation of peripheral circulation in diabetics, as an objective tool in irritancy patch testing, assessment of burnt skin and visualization of spot-wise hyperperfusion in breast skin in association with carcinoma.

  3. Salvianolic Acids Attenuate Rat Hippocampal Injury after Acute CO Poisoning by Improving Blood Flow Properties

    PubMed Central

    Guan, Li; Zhang, Yan-Lin; Li, Zong-Yang; Zhu, Ming-Xia; Yao, Wei-Juan; Zhao, Jin-Yuan

    2015-01-01

    Carbon monoxide (CO) poisoning causes the major injury and death due to poisoning worldwide. The most severe damage via CO poisoning is brain injury and mortality. Delayed encephalopathy after acute CO poisoning (DEACMP) occurs in forty percent of the survivors of acute CO exposure. But the pathological cause for DEACMP is not well understood. And the corresponding therapy is not well developed. In order to investigate the effects of salvianolic acid (SA) on brain injury caused by CO exposure from the view point of hemorheology, we employed a rat model and studied the dynamic of blood changes in the hemorheological and coagulative properties over acute CO exposure. Compared with the groups of CO and 20% mannitol + CO treatments, the severe hippocampal injury caused by acute CO exposure was prevented by SA treatment. These protective effects were associated with the retaining level of hematocrit (Hct), plasma viscosity, fibrinogen, whole blood viscosities and malondialdehyde (MDA) levels in red blood cells (RBCs). These results indicated that SA treatment could significantly improve the deformation of erythrocytes and prevent the damage caused by CO poisoning. Meanwhile, hemorheological indexes are good indicators for monitoring the pathological dynamic after acute CO poisoning. PMID:25705671

  4. Intravenous Infusion of Magnesium Chloride Improves Epicenter Blood Flow during the Acute Stage of Contusive Spinal Cord Injury in Rats

    PubMed Central

    Muradov, Johongir M.

    2013-01-01

    Abstract Vasospasm, hemorrhage, and loss of microvessels at the site of contusive or compressive spinal cord injury lead to infarction and initiate secondary degeneration. Here, we used intravenous injection of endothelial-binding lectin followed by histology to show that the number of perfused microvessels at the injury site is decreased by 80–90% as early as 20 min following a moderate T9 contusion in adult female rats. Hemorrhage within the spinal cord also was maximal at 20 min, consistent with its vasoconstrictive actions in the central nervous system (CNS). Microvascular blood flow recovered to up to 50% of normal volume in the injury penumbra by 6 h, but not at the epicenter. A comparison with an endothelial cell marker suggested that many microvessels fail to be reperfused up to 48 h post-injury. The ischemia was probably caused by vasospasm of vessels penetrating the parenchyma, because repeated Doppler measurements over the spinal cord showed a doubling of total blood flow over the first 12 h. Moreover, intravenous infusion of magnesium chloride, used clinically to treat CNS vasospasm, greatly improved the number of perfused microvessels at 24 and 48 h. The magnesium treatment seemed safe as it did not increase hemorrhage, despite the improved parenchymal blood flow. However, the treatment did not reduce acute microvessel, motor neuron or oligodendrocyte loss, and when infused for 7 days did not affect functional recovery or spared epicenter white matter over a 4 week period. These data suggest that microvascular blood flow can be restored with a clinically relevant treatment following spinal cord injury. PMID:23302047

  5. Modeling blood flow heterogeneity.

    PubMed

    King, R B; Raymond, G M; Bassingthwaighte, J B

    1996-01-01

    It has been known for some time that regional blood flows within an organ are not uniform. Useful measures of heterogeneity of regional blood flows are the standard deviation and coefficient of variation or relative dispersion of the probability density function (PDF) of regional flows obtained from the regional concentrations of tracers that are deposited in proportion to blood flow. When a mathematical model is used to analyze dilution curves after tracer solute administration, for many solutes it is important to account for flow heterogeneity and the wide range of transit times through multiple pathways in parallel. Failure to do so leads to bias in the estimates of volumes of distribution and membrane conductances. Since in practice the number of paths used should be relatively small, the analysis is sensitive to the choice of the individual elements used to approximate the distribution of flows or transit times. Presented here is a method for modeling heterogeneous flow through an organ using a scheme that covers both the high flow and long transit time extremes of the flow distribution. With this method, numerical experiments are performed to determine the errors made in estimating parameters when flow heterogeneity is ignored, in both the absence and presence of noise. The magnitude of the errors in the estimates depends upon the system parameters, the amount of flow heterogeneity present, and whether the shape of the input function is known. In some cases, some parameters may be estimated to within 10% when heterogeneity is ignored (homogeneous model), but errors of 15-20% may result, even when the level of heterogeneity is modest. In repeated trials in the presence of 5% noise, the mean of the estimates was always closer to the true value with the heterogeneous model than when heterogeneity was ignored, but the distributions of the estimates from the homogeneous and heterogeneous models overlapped for some parameters when outflow dilution curves were

  6. Improving placental blood flow in pre-eclampsia with prostaglandin A1.

    PubMed

    Toppozada, M; Medhat, I; Sallam, H; Ismail, A A; el-Badawy, E S; Abd Rabbo, S

    1992-01-01

    Prostaglandin A1 is a potent hypotensive, peripheral vasodilator, a weak oxytocic, antiplatelet aggregator. It improves the renal hemodynamics. Its effect on placental circulation was evaluated (expressed as systolic/diastolic ratio and umbilical artery resistance index) in 20 women with severe pre-eclampsia and 10 normotensive pregnant women, by using the Doppler technique. Moreover, another 10 women with severe pre-eclampsia received dextrose 5% as a placebo for comparative purposes. Significant improvements in both parameters studied were observed in the women with severe pre-eclampsia. The beneficial changes differed significantly from the recorded values when using dextrose in pre-eclampsia or prostaglandin A1 in normotensive subjects. Such promising data add another important perspective to prostaglandin A1 in severe pre-eclampsia and may open up new avenues for its use in other situations with compromised placental flow. PMID:1315092

  7. 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. PMID:26369387

  8. Clinical utility of far-infrared therapy for improvement of vascular access blood flow and pain control in hemodialysis patients

    PubMed Central

    Choi, Soo Jeong; Cho, Eun Hee; Jo, Hye Min; Min, Changwook; Ji, Young Sok; Park, Moo Yong; Kim, Jin Kuk; Hwang, Seung Duk

    2015-01-01

    Background Maintenance of a well-functioning vascular access and minimal needling pain are important goals for achieving adequate dialysis and improving the quality of life in hemodialysis (HD) patients. Far-infrared (FIR) therapy may improve endothelial function and increase access blood flow (Qa) and patency in HD patients. The aim of this study was to evaluate effects of FIR therapy on Qa and patency, and needling pain in HD patients. Methods This prospective clinical trial enrolled 25 outpatients who maintained HD with arteriovenous fistula. The other 25 patients were matched as control with age, sex, and diabetes. FIR therapy was administered for 40 minutes during HD 3 times/wk and continued for 12 months. The Qa was measured by the ultrasound dilution method, whereas pain was measured by a numeric rating scale at baseline, then once per month. Results One patient was transferred to another facility, and 7 patients stopped FIR therapy because of an increased body temperature and discomfort. FIR therapy improved the needling pain score from 4 to 2 after 1 year. FIR therapy increased the Qa by 3 months and maintained this change until 1 year, whereas control patients showed the decrease in Qa. The 1-year unassisted patency with FIR therapy was not significantly different from control. Conclusion FIR therapy improved needling pain. Although FIR therapy improved Qa, the unassisted patency was not different compared with the control. A larger and multicenter study is needed to evaluate the effect of FIR therapy. PMID:27069856

  9. Salutary effect of adjunctive intracoronary nicorandil administration on restoration of myocardial blood flow and functional improvement in patients with acute myocardial infarction.

    PubMed

    Sakata, Y; Kodama, K; Komamura, K; Lim, Y J; Ishikura, F; Hirayama, A; Kitakaze, M; Masuyama, T; Hori, M

    1997-06-01

    Salutary effect of nicorandil, a K+ adenosine triphosphate channel opener, on restoration of myocardial blood flow and functional improvement after coronary revascularization was investigated in 20 patients with first anterior acute myocardial infarction. Ten patients received intracoronary administration of nicorandil (2 mg) after coronary revascularization; the other 10 patients received coronary revascularization only and served as control subjects. Myocardial contrast echocardiography and two-dimensional echocardiography were performed to assess microvascular integrity and regional function in the infarcted area. Nicorandil improved peak contrast intensity ratio (p < 0.001), calculated as the ratio of peak contrast intensity in the infarcted and noninfarcted areas, indicating the restoration of myocardial blood flow to the infarcted myocardium. Regional wall motion improved more significantly in 1 month in patients who received nicorandil (p < 0.01). Thus our results suggested the usefulness of intracoronary nicorandil administration after coronary revascularization for restoring blood flow and functional improvement in patients with acute myocardial infarction. PMID:9200388

  10. 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…

  11. Neuroprotective effects of compound FLZ in an ischemic model mediated by improving cerebral blood flow and enhancing Hsp27 expression.

    PubMed

    Ma, Bo; Li, Min; Ma, Tao; Liu, Geng-Tao; Zhang, Jianjun

    2016-08-01

    Compound FLZ is a synthetic novel derivate of natural squamosamide, which has potent neuroprotective effects based on our previous study. We are now aiming to investigate the effects of FLZ on cerebral blood flow (CBF), infarct volume, neurological function, heat shock protein 70 (Hsp70), and Hsp27 expression in transient focal ischemia. For this goal, an animal model of middle cerebral artery occlusion (MCAO) for 2h followed by reperfusion was used, and animals received low or high doses of FLZ (150 or 300mg/kg), orally 10min after MCAO onset. The results show that the infarct volume was 32.7% for the vehicle control group, and reduced to 17.6 and 12.8% for the low and high dose FLZ-treated groups, respectively. FLZ treatment also significantly improved the neurobehavioral score from 2.6 in the vehicle control group to 1.0 and 0.9 in the low and high dose groups, respectively. Further, FLZ significantly induced Hsp27 over-expression and reduced over-expression of HSP70, a sensitive marker of acute ischemia, in ipsilateral cortex by a dose-dependent manner. In addition, CBF was quantified using laser-Doppler flowmetry. During ischemia, regional CBF (rCBF) was improved from approximately 30% to over 50% of the baseline and the reperfusion-induced hyperemia was reduced in both FLZ dosage groups. Particularly, high dose FLZ reduced rCBF during hyperemia by 30%. In conclusion, FLZ (150 and 300mg/kg) can significantly reduce the infarct volume and improve neurobehavioral deficits in a rat MCAO model, most likely through improving CBF in the penumbra and enhancing Hsp27 expression. PMID:24675028

  12. [Blood flow changes in the optic nerve head of albino rabbits following intravenous administration of brovincamine fumarate, an improver of cerebral circulation and metabolism].

    PubMed

    Nirei, M

    1996-02-01

    The blood flow changes in the optic nerve head in adult albino rabbits following intravenous administration of brovincamine fumarate, an improver of cerebral circulation and metabolism, were investigated employing the hydrogen clearance method. In the brovincamine fumarate (0.1 mg/kg)-administered group, the blood flow in the optic nerve head increased soon after injection and reached the maximal value of 124.2 +/- 7.3% against the value before injection, at 20 minutes after injection, followed by a gradual decrease in the blood flow. Statistical analysis showed a significant increase (p < 0.05) in the blood flow at 10 to 40 minutes after injection, compared with the value before injection in the brovincamine fumarate (0.1 mg/kg)-administered group, but no significant increases in the blood flow were observed in either the brovincamine fumarate (0.5 mg/kg)-administered group or the control group given no brovincamine fumarate throughout the course. No significant changes in the mean values of the blood pressure in the femoral artery, pulse rate, respiratory rate or rectal temperature were observed in any group through the experiment. To learn the mechanism of the different efficacy of the two doses, further studies are needed in light of the cyclic adenosine monophosphate (cyclic AMP) changes induced by brovincamine fumarate administration or in light of the receptor responsiveness to the drug concentration. PMID:8851150

  13. A Dietary Treatment Improves Cerebral Blood Flow and Brain Connectivity in Aging apoE4 Mice.

    PubMed

    Wiesmann, Maximilian; Zerbi, Valerio; Jansen, Diane; Haast, Roy; Lütjohann, Dieter; Broersen, Laus M; Heerschap, Arend; Kiliaan, Amanda J

    2016-01-01

    APOE ε4 (apoE4) polymorphism is the main genetic determinant of sporadic Alzheimer's disease (AD). A dietary approach (Fortasyn) including docosahexaenoic acid, eicosapentaenoic acid, uridine, choline, phospholipids, folic acid, vitamins B12, B6, C, and E, and selenium has been proposed for dietary management of AD. We hypothesize that the diet could inhibit AD-like pathologies in apoE4 mice, specifically cerebrovascular and connectivity impairment. Moreover, we evaluated the diet effect on cerebral blood flow (CBF), functional connectivity (FC), gray/white matter integrity, and postsynaptic density in aging apoE4 mice. At 10-12 months, apoE4 mice did not display prominent pathological differences compared to wild-type (WT) mice. However, 16-18-month-old apoE4 mice revealed reduced CBF and accelerated synaptic loss. The diet increased cortical CBF and amount of synapses and improved white matter integrity and FC in both aging apoE4 and WT mice. We demonstrated that protective mechanisms on vascular and synapse health are enhanced by Fortasyn, independent of apoE genotype. We further showed the efficacy of a multimodal translational approach, including advanced MR neuroimaging, to study dietary intervention on brain structure and function in aging. PMID:27034849

  14. A Dietary Treatment Improves Cerebral Blood Flow and Brain Connectivity in Aging apoE4 Mice

    PubMed Central

    Wiesmann, Maximilian; Zerbi, Valerio; Jansen, Diane; Haast, Roy; Lütjohann, Dieter; Broersen, Laus M.; Heerschap, Arend

    2016-01-01

    APOE ε4 (apoE4) polymorphism is the main genetic determinant of sporadic Alzheimer's disease (AD). A dietary approach (Fortasyn) including docosahexaenoic acid, eicosapentaenoic acid, uridine, choline, phospholipids, folic acid, vitamins B12, B6, C, and E, and selenium has been proposed for dietary management of AD. We hypothesize that the diet could inhibit AD-like pathologies in apoE4 mice, specifically cerebrovascular and connectivity impairment. Moreover, we evaluated the diet effect on cerebral blood flow (CBF), functional connectivity (FC), gray/white matter integrity, and postsynaptic density in aging apoE4 mice. At 10–12 months, apoE4 mice did not display prominent pathological differences compared to wild-type (WT) mice. However, 16–18-month-old apoE4 mice revealed reduced CBF and accelerated synaptic loss. The diet increased cortical CBF and amount of synapses and improved white matter integrity and FC in both aging apoE4 and WT mice. We demonstrated that protective mechanisms on vascular and synapse health are enhanced by Fortasyn, independent of apoE genotype. We further showed the efficacy of a multimodal translational approach, including advanced MR neuroimaging, to study dietary intervention on brain structure and function in aging. PMID:27034849

  15. 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.

  16. Brain Function and Blood Flow

    ERIC Educational Resources Information Center

    Lassen, Niels A.; And Others

    1978-01-01

    Discusses the use of radioactive isotopes to graphically represent changes in the amount of blood flowing in areas of the human cerebral cortex, reflecting changes in the activity of those areas. Numerous illustrations are included. (Author/MA)

  17. Facilitating Mitochondrial Calcium Uptake Improves Activation-Induced Cerebral Blood Flow and Behavior after mTBI

    PubMed Central

    Murugan, Madhuvika; Santhakumar, Vijayalakshmi; Kannurpatti, Sridhar S.

    2016-01-01

    Mild to moderate traumatic brain injury (mTBI) leads to secondary neuronal loss via excitotoxic mechanisms, including mitochondrial Ca2+ overload. However, in the surviving cellular population, mitochondrial Ca2+ influx, and oxidative metabolism are diminished leading to suboptimal neuronal circuit activity and poor prognosis. Hence we tested the impact of boosting neuronal electrical activity and oxidative metabolism by facilitating mitochondrial Ca2+ uptake in a rat model of mTBI. In developing rats (P25-P26) sustaining an mTBI, we demonstrate post-traumatic changes in cerebral blood flow (CBF) in the sensorimotor cortex in response to whisker stimulation compared to sham using functional Laser Doppler Imaging (fLDI) at adulthood (P67-P73). Compared to sham, whisker stimulation-evoked positive CBF responses decreased while negative CBF responses increased in the mTBI animals. The spatiotemporal CBF changes representing underlying neuronal activity suggested profound changes to neurovascular activity after mTBI. Behavioral assessment of the same cohort of animals prior to fLDI showed that mTBI resulted in persistent contralateral sensorimotor behavioral deficit along with ipsilateral neuronal loss compared to sham. Treating mTBI rats with Kaempferol, a dietary flavonol compound that enhanced mitochondrial Ca2+ uptake, eliminated the inter-hemispheric asymmetry in the whisker stimulation-induced positive CBF responses and the ipsilateral negative CBF responses otherwise observed in the untreated and vehicle-treated mTBI animals in adulthood. Kaempferol also improved somatosensory behavioral measures compared to untreated and vehicle treated mTBI animals without augmenting post-injury neuronal loss. The results indicate that reduced mitochondrial Ca2+ uptake in the surviving populations affect post-traumatic neural activation leading to persistent behavioral deficits. Improvement in sensorimotor behavior and spatiotemporal neurovascular activity following kaempferol

  18. Chaotic advection in blood flow.

    PubMed

    Schelin, A B; Károlyi, Gy; de Moura, A P S; Booth, N A; Grebogi, C

    2009-07-01

    In this paper we argue that the effects of irregular chaotic motion of particles transported by blood can play a major role in the development of serious circulatory diseases. Vessel wall irregularities modify the flow field, changing in a nontrivial way the transport and activation of biochemically active particles. We argue that blood particle transport is often chaotic in realistic physiological conditions. We also argue that this chaotic behavior of the flow has crucial consequences for the dynamics of important processes in the blood, such as the activation of platelets which are involved in the thrombus formation. PMID:19658798

  19. Improvements in tissue blood flow and lumbopelvic stability after lumbopelvic core stabilization training in patients with chronic non-specific low back pain.

    PubMed

    Paungmali, Aatit; Henry, Leonard Joseph; Sitilertpisan, Patraporn; Pirunsan, Ubon; Uthaikhup, Sureeporn

    2016-01-01

    [Purpose] This study investigated the effects of lumbopelvic stabilization training on tissue blood flow changes in the lumbopelvic region and lumbopelvic stability compared to placebo treatment and controlled intervention among patients with chronic non-specific low back pain. [Subjects and Methods] A total of 25 participants (7 males, 18 females; mean age, 33.3 ± 14.4 years) participated in this within-subject, repeated-measures, double-blind, placebo-controlled comparison trial. The participants randomly underwent three types of interventions that included lumbopelvic stabilization training, placebo treatment, and controlled intervention with 48 hours between sessions. Lumbopelvic stability and tissue blood flow were measured using a pressure biofeedback device and a laser Doppler flow meter before and after the interventions. [Results] The repeated-measures analysis of variance results demonstrated a significant increase in tissue blood flow over the lumbopelvic region tissues for post- versus pre-lumbopelvic stabilization training and compared to placebo and control interventions. A significant increase in lumbopelvic stability before and after lumbopelvic stabilization training was noted, as well as upon comparison to placebo and control interventions. [Conclusion] The current study supports an increase in tissue blood flow in the lumbopelvic region and improved lumbopelvic stability after core training among patients with chronic non-specific low back pain. PMID:27064327

  20. Improvements in tissue blood flow and lumbopelvic stability after lumbopelvic core stabilization training in patients with chronic non-specific low back pain

    PubMed Central

    Paungmali, Aatit; Henry, Leonard Joseph; Sitilertpisan, Patraporn; Pirunsan, Ubon; Uthaikhup, Sureeporn

    2016-01-01

    [Purpose] This study investigated the effects of lumbopelvic stabilization training on tissue blood flow changes in the lumbopelvic region and lumbopelvic stability compared to placebo treatment and controlled intervention among patients with chronic non-specific low back pain. [Subjects and Methods] A total of 25 participants (7 males, 18 females; mean age, 33.3 ± 14.4 years) participated in this within-subject, repeated-measures, double-blind, placebo-controlled comparison trial. The participants randomly underwent three types of interventions that included lumbopelvic stabilization training, placebo treatment, and controlled intervention with 48 hours between sessions. Lumbopelvic stability and tissue blood flow were measured using a pressure biofeedback device and a laser Doppler flow meter before and after the interventions. [Results] The repeated-measures analysis of variance results demonstrated a significant increase in tissue blood flow over the lumbopelvic region tissues for post- versus pre-lumbopelvic stabilization training and compared to placebo and control interventions. A significant increase in lumbopelvic stability before and after lumbopelvic stabilization training was noted, as well as upon comparison to placebo and control interventions. [Conclusion] The current study supports an increase in tissue blood flow in the lumbopelvic region and improved lumbopelvic stability after core training among patients with chronic non-specific low back pain. PMID:27064327

  1. Vildagliptin in addition to metformin improves retinal blood flow and erythrocyte deformability in patients with type 2 diabetes mellitus – results from an exploratory study

    PubMed Central

    2013-01-01

    Numerous rheological and microvascular alterations characterize the vascular pathology in patients with type 2 diabetes mellitus (T2DM). This study investigated effects of vildagliptin in comparison to glimepiride on retinal microvascular blood flow and erythrocyte deformability in T2DM. Fourty-four patients with T2DM on metformin monotherapy were included in this randomized, exploratory study over 24 weeks. Patients were randomized to receive either vildagliptin (50 mg twice daily) or glimepiride individually titrated up to 4 mg in addition to ongoing metformin treatment. Retinal microvascular blood flow (RBF) and the arteriolar wall to lumen ratio (WLR) were assessed using a laser doppler scanner. In addition, the erythrocyte elongation index (EI) was measured at different shear stresses using laserdiffractoscopy. Both treatments improved glycaemic control (p < 0.05 vs. baseline; respectively). While only slight changes in RBF and the WLR could be observed during treatment with glimepiride, vildagliptin significantly increased retinal blood flow and decreased the arterial WLR (p < 0.05 vs. baseline respectively). The EI increased during both treatments over a wide range of applied shear stresses (p < 0.05 vs. baseline). An inverse correlation could be observed between improved glycaemic control (HbA1c) and EI (r = −0.524; p < 0.0001) but not with the changes in retinal microvascular measurements. Our results suggest that vildagliptin might exert beneficial effects on retinal microvascular blood flow beyond glucose control. In contrast, the improvement in erythrocyte deformability observed in both treatment groups, seems to be a correlate of improved glycaemic control. PMID:23565740

  2. Regulation of pulpal blood flow

    SciTech Connect

    Kim, S.

    1985-04-01

    The regulation of blood flow of the dental pulp was investigated in dogs and rats anesthetized with sodium pentobarbital. Pulpal blood flow was altered by variations of local and systemic hemodynamics. Macrocirculatory blood flow (ml/min/100 g) in the dental pulp was measured with both the /sup 133/Xe washout and the 15-microns radioisotope-labeled microsphere injection methods on the canine teeth of dogs, to provide a comparison of the two methods in the same tooth. Microcirculatory studies were conducted in the rat incisor tooth with microscopic determination of the vascular pattern, RBC velocity, and intravascular volumetric flow distribution. Pulpal resistance vessels have alpha- and beta-adrenergic receptors. Activation of alpha-receptors by intra-arterial injection of norepinephrine (NE) caused both a reduction in macrocirculatory Qp in dogs and decreases in arteriolar and venular diameters and intravascular volumetric flow (Qi) in rats. These responses were blocked by the alpha-antagonist PBZ. Activation of beta-receptors by intra-arterial injection of isoproterenal (ISO) caused a paradoxical reduction of Qp in dogs. In rats, ISO caused a transient increase in arteriolar Qi followed by a flow reduction; arteriolar dilation was accompanied by venular constriction. These macrocirculatory and microcirculatory responses to ISO were blocked by the alpha-antagonist propranolol.

  3. Soluble epoxide hydrolase gene deletion improves blood flow and reduces infarct size after cerebral ischemia in reproductively senescent female mice

    PubMed Central

    Zuloaga, Kristen L.; Zhang, Wenri; Roese, Natalie E.; Alkayed, Nabil J.

    2015-01-01

    Soluble epoxide hydrolase (sEH), a key enzyme in the metabolism of vasodilatory epoxyeicosatrienoic acids (EETs), is sexually dimorphic, suppressed by estrogen, and contributes to underlying sex differences in cerebral blood flow and injury after cerebral ischemia. We tested the hypothesis that sEH inhibition or gene deletion in reproductively senescent (RS) female mice would increase cerebral perfusion and decrease infarct size following stroke. RS (15–18 month old) and young (3–4 month old) female sEH knockout (sEHKO) mice and wild type (WT) mice were subjected to 45 min middle cerebral artery occlusion (MCAO) with laser Doppler perfusion monitoring. WT mice were treated with vehicle or a sEH inhibitor t-AUCB at the time of reperfusion and every 24 h thereafter for 3 days. Differences in regional cerebral blood flow were measured in vivo using optical microangiography (OMAG). Infarct size was measured 3 days after reperfusion. Infarct size and cerebral perfusion 24 h after MCAO were not altered by age. Both sEH gene deletion and sEH inhibition increased cortical perfusion 24 h after MCAO. Neither sEH gene deletion nor sEH inhibition reduced infarct size in young mice. However, sEH gene deletion, but not sEH inhibition of the hydrolase domain of the enzyme, decreased infarct size in RS mice. Results of these studies show that sEH gene deletion and sEH inhibition enhance cortical perfusion following MCAO and sEH gene deletion reduces damage after ischemia in RS female mice; however this neuroprotection in absent is young mice. PMID:25642188

  4. Combined vector velocity and spectral Doppler imaging for improved imaging of complex blood flow in the carotid arteries.

    PubMed

    Ekroll, Ingvild Kinn; Dahl, Torbjørn; Torp, Hans; Løvstakken, Lasse

    2014-07-01

    Color flow imaging and pulsed wave (PW) Doppler are important diagnostic tools in the examination of patients with carotid artery disease. However, measurement of the true peak systolic velocity is dependent on sample volume placement and the operator's ability to provide an educated guess of the flow direction. Using plane wave transmissions and a duplex imaging scheme, we present an all-in-one modality that provides both vector velocity and spectral Doppler imaging from one acquisition, in addition to separate B-mode images of sufficient quality. The vector Doppler information was used to provide automatically calibrated (angle-corrected) PW Doppler spectra at every image point. It was demonstrated that the combined information can be used to generate spatial maps of the peak systolic velocity, highlighting regions of high velocity and the extent of the stenotic region, which could be used to automate work flow as well as improve the accuracy of measurement of true peak systolic velocity. The modality was tested in a small group (N = 12) of patients with carotid artery disease. PW Doppler, vector velocity and B-mode images could successfully be obtained from a single recording for all patients with a body mass index ranging from 21 to 31 and a carotid depth ranging from 16 to 28 mm. PMID:24785436

  5. Estrogens are needed for the improvement in endothelium-mediated dilation induced by a chronic increase in blood flow in rat mesenteric arteries.

    PubMed

    Tarhouni, K; Guihot, A L; Vessieres, E; Procaccio, V; Grimaud, L; Abraham, P; Lenfant, F; Arnal, J F; Favre, J; Loufrani, L; Henrion, D

    2016-05-01

    Resistance arteries play a key role in the control of local blood flow. They undergo outward remodeling in response to a chronic increase in blood flow as seen in collateral artery growth in ischemic disorders. We have previously shown that mesenteric artery outward remodeling depends on the endothelial estrogen receptor alpha. As outward arterial remodeling is associated with improved endothelium-dependent dilation, we hypothesized that estrogens might also play a role in flow-mediated improvement of endothelium-dependent dilation. Local increase in blood flow in first order mesenteric arteries was obtained after ligation of adjacent arteries in three-month old ovariectomized female rats treated with 17-beta-estradiol (OVX+E2) or vehicle (OVX). After 2 weeks, diameter was equivalent in high flow (HF) than in normal flow (NF) arteries with a greater wall to lumen ratio in HF vessels in OVX rats. Acetylcholine-mediated relaxation was lower in HF than in NF vessels. eNOS and caveolin-1 expression level was equivalent in HF and NF arteries. By contrast, arterial diameter was 30% greater in HF than in NF arteries and the wall to lumen ratio was not changed in OVX+E2 rats. Acetylcholine-mediated relaxation was higher in HF than in NF arteries. The expression level of eNOS was higher and that of caveolin-1 was lower in HF than in NF arteries. Acetylcholine (NO-dependent)-mediated relaxation was partly inhibited by the NO-synthesis blocker L-NAME in OVX rats whereas L-NAME blocked totally the relaxation in OVX+E2 rats. Endothelium-independent relaxation (sodium nitroprusside) was equivalent in OXV and OVX+E2 rats. Similarly, serotonin- and phenylephrine-mediated contractions were higher in HF than in NF arteries in both OVX and OVX+E2 rats in association with high ratio of phosphorylated ERK1/2 to ERK1/2. Thus, we demonstrated the essential role of endogenous E2 in flow-mediated improvement of endothelium (NO)-mediated dilatation in rat mesenteric arteries. PMID:26471832

  6. Ocular Blood Flow Autoregulation Mechanisms and Methods

    PubMed Central

    Luo, Xue; Shen, Yu-meng; Jiang, Meng-nan; Lou, Xiang-feng; Shen, Yin

    2015-01-01

    The main function of ocular blood flow is to supply sufficient oxygen and nutrients to the eye. Local blood vessels resistance regulates overall blood distribution to the eye and can vary rapidly over time depending on ocular need. Under normal conditions, the relation between blood flow and perfusion pressure in the eye is autoregulated. Basically, autoregulation is a capacity to maintain a relatively constant level of blood flow in the presence of changes in ocular perfusion pressure and varied metabolic demand. In addition, ocular blood flow dysregulation has been demonstrated as an independent risk factor to many ocular diseases. For instance, ocular perfusion pressure plays key role in the progression of retinopathy such as glaucoma and diabetic retinopathy. In this review, different direct and indirect techniques to measure ocular blood flow and the effect of myogenic and neurogenic mechanisms on ocular blood flow are discussed. Moreover, ocular blood flow regulation in ocular disease will be described. PMID:26576295

  7. Hypercapnia-induced increases in cerebral blood flow do not improve lower body negative pressure tolerance during hyperthermia

    PubMed Central

    Lucas, Rebekah A. I.; Pearson, James; Schlader, Zachary J.

    2013-01-01

    Heat-related decreases in cerebral perfusion are partly the result of ventilatory-related reductions in arterial CO2 tension. Cerebral perfusion likely contributes to an individual's tolerance to a challenge like lower body negative pressure (LBNP). Thus increasing cerebral perfusion may prolong LBNP tolerance. This study tested the hypothesis that a hypercapnia-induced increase in cerebral perfusion improves LBNP tolerance in hyperthermic individuals. Eleven individuals (31 ± 7 yr; 75 ± 12 kg) underwent passive heat stress (increased intestinal temperature ∼1.3°C) followed by a progressive LBNP challenge to tolerance on two separate days (randomized). From 30 mmHg LBNP, subjects inhaled either (blinded) a hypercapnic gas mixture (5% CO2, 21% oxygen, balanced nitrogen) or room air (SHAM). LBNP tolerance was quantified via the cumulative stress index (CSI). Mean middle cerebral artery blood velocity (MCAvmean,) and end-tidal CO2 (PetCO2) were also measured. CO2 inhalation of 5% increased PetCO2 at ∼40 mmHg LBNP (by 16 ± 4 mmHg) and at LBNP tolerance (by 18 ± 5 mmHg) compared with SHAM (P < 0.01). Subsequently, MCAvmean was higher in the 5% CO2 trial during ∼40 mmHg LBNP (by 21 ± 12 cm/s, ∼31%) and at LBNP tolerance (by 18 ± 10 cm/s, ∼25%) relative to the SHAM (P < 0.01). However, hypercapnia-induced increases in MCAvmean did not alter LBNP tolerance (5% CO2 CSI: 339 ± 155 mmHg × min; SHAM CSI: 273 ± 158 mmHg × min; P = 0.26). These data indicate that inhaling a hypercapnic gas mixture increases cerebral perfusion during LBNP but does not improve LBNP tolerance when hyperthermic. PMID:23864641

  8. 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.

  9. Fisetin-Rich Extracts of Rhus verniciflua Stokes Improve Blood Flow Rates in Mice Fed Both Normal and High-Fat Diets.

    PubMed

    Im, Won Kyun; Park, Hyun Jung; Lee, Kwang Soo; Lee, Jung Hoon; Kim, Young Dong; Kim, Kyeong-Hee; Park, Sang-Jae; Hong, Seokmann; Jeon, Sung Ho

    2016-02-01

    Although it has been previously reported that Rhus verniciflua Stokes (RVS) possesses in vitro anti-inflammatory activity, the precise in vivo mechanisms of RVS extracts and a main active component called fisetin have not been well elucidated. In this study, using newly developed protocols, we prepared urushiol-free but fisetin-enriched RVS extracts and investigated their effects on the vascular immune system. We found that the water-soluble fractions of detoxified RVS with the flavonoid fisetin can inhibit lipopolysaccharide-induced production of nitric oxide (NO) and prostaglandin E2 (PGE2). Furthermore, RVS can reduce inducible nitric oxide synthase and COX2 gene expression levels, which are responsible for NO and PGE2 production, respectively, in RAW264.7 macrophage cells. Because inflammation is linked to the activation of the coagulation system, we hypothesized that RVS and its active component fisetin possess anticoagulatory activities. As expected, we found that both RVS and fisetin could inhibit the coagulation of human peripheral blood cells. Moreover, in vivo RVS treatment could return the retarded blood flow elicited by a high-fat diet (HFD) back to the normal level in mice. In addition, RVS treatment has significantly reduced body weight gained by HFD in mice. Taken together, the fisetin-rich RVS extracts have potential antiplatelet and antiobesity activities and could be used as a functional food ingredient to improve blood circulation. PMID:26741654

  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. Cutaneous blood flow in psoriasis

    SciTech Connect

    Klemp, P.; Staberg, B.

    1983-12-01

    The disappearance rate of /sup 133/Xe was studied in 20 patients with psoriasis vulgaris, using an epicutaneous labeling technique in involved skin lesions or normal-appearing skin of the proximal extensor site of the forearm. Control experiments were performed in 10 normal subjects. Calculations of the cutaneous blood flow (CBF) in psoriatic skin lesions were performed using a tissue-to-blood partition coefficient for /sup 133/Xe, lambda c,pso, of 1.2 ml/100 g/min. lambda c,pso was estimated after the relative content of water, lipids, and proteins had been analyzed in psoriatic skin biopsies of 6 patients with untreated psoriasis. The mean relative content of water was markedly reduced to 23.5 +/- 1.5% (SEM), and lipids and proteins were markedly increased to 2.5 +/- 0.7% and 74.0 +/- 2.2, respectively, compared to previously published data for normal skin (water 72.5%, lipids 1%, proteins 26.5%). Mean CBF in untreated psoriatic skin was 63.5 +/- 9.0 ml/100 g/min. This was significantly higher than the mean CBF in 10 normal subjects, 6.3 +/- 0.5 ml/100 g/min (p much less than 0.0001). Mean CBF in normal-appearing skin in patients with psoriasis was 11.0 +/- 1.3 ml/100 g/min. This was significantly higher than CBF in normal subjects (p less than 0.0002).

  12. Regional cerebral blood flow in schizophrenia

    SciTech Connect

    Mathew, R.J.; Duncan, G.C.; Weinman, M.L.; Barr, D.L.

    1982-10-01

    Regional cerebral blood flow (rCBF) was measured via xenon133 inhalation technique in 23 patients with schizophrenia and 18 age- and sex-matched controls. The mean blood flow to both hemispheres was found to be lower for the patients. The patients and their controls did not differ on interhemispheric differences in blood flow. There were no differences in rCBF between medicated and unmedicated, subchronic and chronic, and paranoid and nonparanoid patients. Hallucinations were associated with reduced blood flow to several postcentral regions.

  13. 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.

  14. Orbital decompression surgery and horse chestnut seed extract improved superior orbital vein blood flow in patients with thyroid-associated ophthalmopathy

    PubMed Central

    Wu, Yu-Jie; Wei, Xin; Xiao, Man-Yi; Xiong, Wei

    2016-01-01

    AIM To evaluate the efficacy and safety of orbital decomposition (OD) surgery in combination with horse chestnut seed extract (HCSE), as compared to OD alone, in patients with thyroid-associated ophthalmopathy (TAO). METHODS Sixty-two orbits from 62 TAO patients were randomly assigned to OD or OD+HCSE at 1:1 ratio (31 received OD alone, 31 received OD+HCSE). Forty-two orbits from 21 healthy subjects were used as controls. Complete ophthalmic examination and color Doppler flow imaging (CDFI) were performed before surgery and 3mo post-surgery on all 62 orbits from the TAO patients. CDFI were also performed on the 42 control orbits. The effect of OD+HCSE and OD alone on TAO orbits was compared on several endpoints, including superior ophthalmic vein blood flow (SOVBF) parameters, subjective assessment, soft tissue involvement, lid retraction, diplopia, eye movement restriction, degree of exophthalmos, and intraocular pressure. The control orbits were used as reference for the SOVBF parameters. RESULTS OD surgery with or without HCSE improved SOVBF, symptoms and soft tissue involvement, decreased degree of exophthalmos and intraocular pressure in orbits of TAO patients. The OD+HCSE combination led to significantly better improvement of SOVBF than OD alone. The differences between the reductions of SOVBF in the two groups are 1.26 cm/s in max-volecity and 0.52 cm/s in min-volecity (P<0.0001). CONCLUSION SOVBF is significantly reduced in the orbits affected with TAO, indicating that congestion may be an important factor contributing to TAO pathogenesis. OD surgery improves the SOVBF, and combination of HCSE medication and OD surgery further improved venous return than OD surgery alone. PMID:27366690

  15. 21 CFR 870.2120 - Extravascular blood flow probe.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 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...

  16. 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.

  17. 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.

  18. Pancreatic islet blood flow and its measurement.

    PubMed

    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

    2016-05-01

    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

  19. 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

  20. Impact of Endothelium Roughness on Blood Flow

    PubMed Central

    Park, Sangwoo; Intaglietta, Marcos; Tartakovsky, Daniel M.

    2012-01-01

    Cell free layer (CFL), a plasma layer bounded by the red blood cell (RBC) core and the endothelium, plays an important physiological role. Its width affects the effective blood viscosity as well as the scavenging and production of nitric oxide (NO). Measurements of the CFL and its spatio-temporal variability are highly uncertain, exhibiting random fluctuations. Yet traditional models of blood flow and NO scavenging treat the CFL’s bounding surfaces as deterministic and smooth. We investigate the effects of the endothelium roughness and uncertain (random) spatial variability on blood flow and estimates of effective blood viscosity. PMID:22300799

  1. Subcutaneous blood flow in psoriasis

    SciTech Connect

    Klemp, P.

    1985-03-01

    The simultaneously recorded disappearance rates of /sup 133/xe from subcutaneous adipose tissue in the crus were studied in 10 patients with psoriasis vulgaris using atraumatic labeling of the tissue in lesional skin (LS) areas and symmetrical, nonlesional skin (NLS) areas. Control experiments were performed bilaterally in 10 younger, healthy subjects. The subcutaneous washout rate constant was significantly higher in LS, 0.79 +/- 0.05 min-1 x 10(2) compared to the washout rate constant of NLS, 0.56 +/- 0.07 min-1. 10(2), or the washout rate constant in the normal subjects, 0.46 +/- 0.17 min-1 x 10(2). The mean washout rate constant in NLS was 25% higher than the mean washout rate constant in the normal subjects. The difference was, however, not statistically significant. Differences in the washout rate constants might be due to abnormal subcutaneous tissue-to-blood partition (lambda) in the LS--and therefore not reflecting the real differences in the subcutaneous blood flow (SBF). The lambda for /sup 133/Xe was therefore measured--using a double isotope washout method (/sup 133/Xe and (/sup 131/I)antipyrine)--in symmetrical sites of the lateral crus in LS and NLS of 10 patients with psoriasis vulgaris and in 10 legs of normal subjects. In LS the lambda was 4.52 +/- 1.67 ml/g, which was not statistically different from that of NLS, 5.25 +/- 2.19 ml/g, nor from that of normal subcutaneous tissue, 4.98 +/- 1.04 ml/g. Calculations of the SBF using the obtained lambda values gave a significantly higher SBF in LS, 3.57 +/- 0.23 ml/100 g/min, compared to SBF in the NLS, 2.94 +/- 0.37 ml/100 g/min. There was no statistically significant difference between SBF in NLS and SBF in the normal subjects. The increased SBF in LS of psoriatics might be a secondary phenomenon to an increased heat loss in the lesional skin.

  2. A mechanical chest compressor closed-loop controller with an effective trade-off between blood flow improvement and ribs fracture reduction.

    PubMed

    Zhang, Guang; Wu, Taihu; Song, Zhenxing; Wang, Haitao; Lu, Hengzhi; Wang, Yalin; Wang, Dan; Chen, Feng

    2015-06-01

    Chest compression (CC) is a significant emergency medical procedure for maintaining circulation during cardiac arrest. Although CC produces the necessary blood flow for patients with heart arrest, improperly deep CC will contribute significantly to the risk of chest injury. In this paper, an optimal CC closed-loop controller for a mechanical chest compressor (OCC-MCC) was developed to provide an effective trade-off between the benefit of improved blood perfusion and the risk of ribs fracture. The trade-off performance of the OCC-MCC during real automatic mechanical CCs was evaluated by comparing the OCC-MCC and the traditional mechanical CC method (TMCM) with a human circulation hardware model based on hardware simulations. A benefit factor (BF), risk factor (RF) and benefit versus risk index (BRI) were introduced in this paper for the comprehensive evaluation of risk and benefit. The OCC-MCC was developed using the LabVIEW control platform and the mechanical chest compressor (MCC) controller. PID control is also employed by MCC for effective compression depth regulation. In addition, the physiological parameters model for MCC was built based on a digital signal processor for hardware simulations. A comparison between the OCC-MCC and TMCM was then performed based on the simulation test platform which is composed of the MCC, LabVIEW control platform, physiological parameters model for MCC and the manikin. Compared with the TMCM, the OCC-MCC obtained a better trade-off and a higher BRI in seven out of a total of nine cases. With a higher mean value of cardiac output (1.35 L/min) and partial pressure of end-tidal CO2 (15.7 mmHg), the OCC-MCC obtained a larger blood flow and higher BF than TMCM (5.19 vs. 3.41) in six out of a total of nine cases. Although it is relatively difficult to maintain a stable CC depth when the chest is stiff, the OCC-MCC is still superior to the TMCM for performing safe and effective CC during CPR. The OCC-MCC is superior to the TMCM in

  3. Improvements in the Quantitative Assessment of Cerebral Blood Volume and Flow with the Removal of Vessel Voxels from MR Perfusion Images

    PubMed Central

    Teng, Michael Mu Huo; Cho, I-Chieh; Kao, Yi-Hsuan; Chuang, Chi-Shuo; Chiu, Fang-Ying; Chang, Feng-Chi

    2013-01-01

    Objective. To improve the quantitative assessment of cerebral blood volume (CBV) and flow (CBF) in the brain voxels from MR perfusion images. Materials and Methods. Normal brain parenchyma was automatically segmented with the time-to-peak criteria after cerebrospinal fluid removal and preliminary vessel voxel removal. Two scaling factors were calculated by comparing the relative CBV and CBF of the segmented normal brain parenchyma with the absolute values in the literature. Using the scaling factors, the relative values were converted to the absolute CBV and CBF. Voxels with either CBV > 8 mL/100 g or CBF > 100 mL/100 g/min were characterized as vessel voxels and were excluded from the quantitative measurements. Results. The segmented brain parenchyma with normal perfusion was consistent with the angiographic findings for each patient. We confirmed the necessity of dual thresholds including CBF and CBV for proper removal of vessel voxels. The scaling factors were 0.208 ± 0.041 for CBV, and 0.168 ± 0.037, 0.172 ± 0.037 for CBF calculated using standard and circulant singular value decomposition techniques, respectively. Conclusion. The automatic scaling and vessel removal techniques provide an alternative method for obtaining improved quantitative assessment of CBV and CBF in patients with thromboembolic cerebral arterial disease. PMID:23586033

  4. 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.

  5. Radioisotopic flow scanning for portal blood flow and portal hypertension

    SciTech Connect

    Hesdorffer, C.S.; Bezwoda, W.R.; Danilewitz, M.D.; Esser, J.D.; Tobias, M.

    1987-08-01

    The use of a simple, noninvasive, isotope scanning technique for the determination of relative portal blood flow and detection of portal hypertension is described. Using this technique the presence of portal hypertension was demonstrated in seven of nine patients known to have elevated portal venous pressure. By contrast, esophageal varices were demonstrated in only five of these patients, illustrating the potential value of the method. Furthermore, this technique has been adapted to the study of portal blood flow in patients with myeloproliferative disorders with splenomegaly but without disturbances in hepatic architecture. Results demonstrate that the high relative splenic flow resulting from the presence of splenomegaly may in turn be associated with elevated relative portal blood flow and portal hypertension. The theoretic reasons for the development of flow-related portal hypertension and its relationship to splenic blood flow are discussed.

  6. Hemodilution increases cerebral blood flow in acute ischemic stroke

    SciTech Connect

    Vorstrup, S.; Andersen, A.; Juhler, M.; Brun, B.; Boysen, G.

    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 of 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.

  7. Polyethylene glygol conjugated superoxide dismutase (PEG-SOD) improves recovery of hypercapnia cerebral blood flow (CBF) reactivity following transient global ischemia in piglets

    SciTech Connect

    Traystman, R.J.; Kirsch, J.R.; Helfaer, M.A.; Haun, S.E. )

    1991-03-15

    This study tested the hypothesis that alteration in hypercapnic cerebral blood flow (CBF) reactivity is due to oxygen-derived free radical mediated vascular damage and therefore could be inhibited by treatment with PEG-SOD. Pentobarbital anesthetized piglets were mechanically ventilated and hemodynamically monitored. CBF was measured at PaCO{sub 2} of approximately 25, 40 and 55 mmHg. Reactivity was tested in all piglets prior to and 2 hours following reperfusion from global ischemia. Control piglets received PEG prior to ischemia and at reperfusion. Experimental piglets received either PEG-SOD prior to ischemia and PEG at reperfusion or PEG prior to ischemia and PEG-SOD at reperfusion. During reperfusion cerebral perfusion pressure was maintained constant between groups by intravenous infusion of epinephrine. Pre-ischemic hypercapnic reactivity was not different between groups. At 2 hr reperfusion hypercapnic CBF reactivity in control piglets was diminished to forebrain and brainstem but hypercapnic reactivity was not different than preischemic values in either group receiving PEG-SOD. The authors conclude that administration of PEG-SOD, either prior to or following transient global ischemia, improves recovery of post-ischemic hypercapnic reactivity in piglets. This implicates oxygen-derived free radicals as important mediators of reperfusion injury in brain.

  8. Exercise Training Could Improve Age-Related Changes in Cerebral Blood Flow and Capillary Vascularity through the Upregulation of VEGF and eNOS

    PubMed Central

    Viboolvorakul, Sheepsumon; Patumraj, Suthiluk

    2014-01-01

    This study aimed to investigate the effect of exercise training on age-induced microvascular alterations in the brain. Additionally, the association with the protein levels of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) was also assessed. Male Wistar rats were divided into four groups: sedentary-young (SE-Young, n = 5), sedentary aged (SE-Aged, n = 8), immersed-aged (IM-Aged, n = 5), and exercise trained-aged (ET-Aged, 60 minutes/day and 5 days/week for 8 weeks, n = 8) rats. The MAPs of all aged groups, SE-Aged, IM-Aged, and ET-Aged, were significantly higher than that of the SE-Young group. The regional cerebral blood flow (rCBF) in the SE-Aged and IM-Aged was significantly decreased as compared to SE-Young groups. However, rCBF of ET-Aged group was significantly higher than that in the IM-Aged group (P < 0.05). Moreover, the percentage of capillary vascularity (%CV) and the levels of VEGF and eNOS in the ET-Aged group were significantly increased compared to the IM-Aged group (P < 0.05). These results imply that exercise training could improve age-induced microvascular changes and hypoperfusion closely associated with the upregulation of VEGF and eNOS. PMID:24822184

  9. Inhibition of Mas G-protein signaling improves coronary blood flow, reduces myocardial infarct size, and provides long-term cardioprotection.

    PubMed

    Zhang, Tong; Li, Zhuangjie; Dang, Huong; Chen, Ruoping; Liaw, Chen; Tran, Thuy-Anh; Boatman, P Douglas; Connolly, Daniel T; Adams, John W

    2012-01-01

    The Mas receptor is a class I G-protein-coupled receptor that is expressed in brain, testis, heart, and kidney. The intracellular signaling pathways activated downstream of Mas are still largely unknown. In the present study, we examined the expression pattern and signaling of Mas in the heart and assessed the participation of Mas in cardiac ischemia-reperfusion injury. Mas mRNA and protein were present in all chambers of human hearts, with cardiomyocytes and coronary arteries being sites of enriched expression. Expression of Mas in either HEK293 cells or cardiac myocytes resulted in constitutive coupling to the G(q) protein, which in turn activated phospholipase C and caused inositol phosphate accumulation. To generate chemical tools for use in probing the function of Mas, we performed a library screen and chemistry optimization program to identify potent and selective nonpeptide agonists and inverse agonists. Mas agonists activated G(q) signaling in a dose-dependent manner and reduced coronary blood flow in isolated mouse and rat hearts. Conversely, treatment of isolated rat hearts with Mas inverse agonists improved coronary flow, reduced arrhythmias, and provided cardioprotection from ischemia-reperfusion injury, an effect that was due, at least in part, to decreased cardiomyocyte apoptosis. Participation of Mas in ischemia-reperfusion injury was confirmed in Mas knockout mice, which had reduced infarct size relative to mice with normal Mas expression. These results suggest that activation of Mas during myocardial infarction contributes to ischemia-reperfusion injury and further suggest that inhibition of Mas-G(q) signaling may provide a new therapeutic strategy directed at cardioprotection. PMID:22003054

  10. 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.

  11. CARBOXYHEMOGLOBIN AND BRAIN BLOOD FLOW IN HUMANS

    EPA Science Inventory

    It has been shown that with increased carboxyhemoglobin (COHb) and associated decrease in blood oxygen-carrying capacity, a compensatory increase in brain-blood flow (BBF) develops. he BBF response in humans has been shown to be quite variable. wo experiments were conducted in wh...

  12. Nutrient and nonnutrient renal blood flow

    SciTech Connect

    Young, J.S.; Passmore, J.C.; Hartupee, D.A.; Baker, C.H. )

    1990-06-01

    The role of prostaglandins in the distribution of total renal blood flow (TRBF) between nutrient and nonnutrient compartments was investigated in anesthetized mongrel dogs. Renal blood flow distribution was assessed by the xenon 133 freeze-dissection technique and by rubidium 86 extraction after ibuprofen treatment. Ibuprofen (13 mg/kg) significantly decreased TRBF by 16.3% +/- 1.2% (mean +/- SEM electromagnetic flow probe; p less than 0.005), but did not alter blood flows to the outer cortex (3.7 vs 4.3 ml/min per gram), the inner cortex (2.6 vs 2.7 ml/min per gram), and the other medulla (1.5 vs 1.5 ml/min per gram), which suggests a decrease in nonnutrient flow. In a separate group of animals the effect of reduced blood flow on the nutrient and nonnutrient components was determined by mechanically reducing renal arterial blood flow by 48%. Unlike the ibuprofen group, nutrient blood flows were proportionally reduced with the mechanical decrease in TRBF in the outer cortex (1.9 ml/min per gram, p less than 0.05), the inner cortex (1.4 ml/min per gram, p less than 0.05), and the outer medulla (0.8 ml/min per gram, p less than 0.01). These results indicate no shift between nutrient and nonnutrient compartments. Nutrient and nonnutrient renal blood flows of the left kidney were also determined by 86Rb extraction. After ibuprofen treatment, nonextracted 86Rb decreased to 12.1% from the control value of 15.6% (p less than 0.05). Mechanical reduction of TRBF did not significantly decrease the proportion of unextracted 86Rb (18.7%).

  13. Pancreatic blood flow in experimental acute pancreatitis

    SciTech Connect

    Berry, A.R.; Millar, A.M.; Taylor, T.V.

    1982-05-01

    The etiology and pathogenesis of acute necrotizing hemorrhagic pancreatitis remain controversial. Recent work has suggested that an early fall in pancreatic blood flow, causing ischemia, may be the initiating factor. Using an established rat model of hemorrhagic pancreatitis and the fractional indicator distribution technique with /sup 86/RbCl, pancreatic blood flow and tissue perfusion have been measured at various times in the condition. Six groups of ten rats were studied: control sham operation and pancreatitis groups were sacrificed at 1, 6, and 24 hr. Pancreatic blood flow (% of cardiac output) and perfusion (blood flow/g tissue) were measured. Blood flow was increased by a maximum of 53% at 1 hr (P less than 0.001) and remained elevated for 24 hr, and perfusion was increased by a maximum of 70% (P less than 0.001) at 1 hr and remained elevated at 6 hr. Pancreatic perfusion declines after 6 hr due to increasing gland edema. The results demonstrate a significant increase in pancreatic blood flow and perfusion in experimentally induced acute pancreatitis, suggesting a primary inflammatory response, and refute the ischemic etiological theory.

  14. 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. PMID:26876648

  15. Raynaud's disease: reduced hand blood flows with normal blood viscosity.

    PubMed

    McGrath, M A; Peek, R; Penny, R

    1978-04-01

    Hand blood flows and the blood and plasma viscosities were measured in patients with Raynaud's disease in an attempt to identify the mechanism of the episodic vascular insufficiency. Using venous occlusion plethysmography the following observations were made: (1) the hand blood flows were significantly less than in normals at 32 degrees, 27 degrees and 20 degrees C; (2) the percentage decrease in flow with cooling was greater in normals and (3) cooling of one hand from 32 degrees to 27 degrees C caused an abnormal decrease in flow through the contralateral hand. Using a rotational viscometer the blood and plasma viscosities were found to be normal at both high and low shear rates. The percentage increase in the blood viscosity with cooling from 35 degrees to 25 degrees was also normal. These studies demonstrate an increased constrictive response of the cutaneous vasculature of the hand to both local and reflex stimulation, and exclude a rheological abnormality, under conditions similar to those of the present study. PMID:277163

  16. Laser Speckle Imaging of Cerebral Blood Flow

    NASA Astrophysics Data System (ADS)

    Luo, Qingming; Jiang, Chao; Li, Pengcheng; Cheng, Haiying; Wang, Zhen; Wang, Zheng; Tuchin, Valery V.

    Monitoring the spatio-temporal characteristics of cerebral blood flow (CBF) is crucial for studying the normal and pathophysiologic conditions of brain metabolism. By illuminating the cortex with laser light and imaging the resulting speckle pattern, relative CBF images with tens of microns spatial and millisecond temporal resolution can be obtained. In this chapter, a laser speckle imaging (LSI) method for monitoring dynamic, high-resolution CBF is introduced. To improve the spatial resolution of current LSI, a modified LSI method is proposed. To accelerate the speed of data processing, three LSI data processing frameworks based on graphics processing unit (GPU), digital signal processor (DSP), and field-programmable gate array (FPGA) are also presented. Applications for detecting the changes in local CBF induced by sensory stimulation and thermal stimulation, the influence of a chemical agent on CBF, and the influence of acute hyperglycemia following cortical spreading depression on CBF are given.

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. Improved Whole-Blood-Staining Device

    NASA Technical Reports Server (NTRS)

    Sams, Clarence F.; Crucian, Brian; Paul, Bonnie; Melton, Shannon; Guess, Terry

    2012-01-01

    Dramatic improvements have been made in NASA s Whole Blood Staining Device (WBSD) since it was last described in "Whole-Blood-Staining Device," NASA Tech Briefs, Vol. 23, No. 10 (October 1999), page 64. The new system has a longer shelf life, a simpler and more effective operational procedure, improved interface with instrumentation, and shorter processing time. More specifically, the improvements have targeted bag and locking clip materials, sampling ports, and air pocket prevention. The WBSD stains whole blood collected during spaceflight for subsequent flow cytometric analysis. In short, the main device stains white blood cells by use of monoclonal antibodies conjugated to various fluorochromes, followed by lysing and fixing of the cells by use of a commercial reagent that has been diluted according to NASA safety standards. This system is compact, robust, and does not require electric power, precise mixing, or precise incubation times. Figure 1 depicts the present improved version for staining applications, which is a poly(tetrafluoroethylene) bag with a Luer-lock port and plastic locking clips. An InterLink (or equivalent) intravenous- injection port screws into the Luer-lock port. The inflatable/collapsible nature of the bag facilitates loading and helps to minimize the amount of air trapped in the fully loaded bag. Some additional uses have been identified for the device beyond whole blood staining. The WBSD has been configured for functional assays that require culture of live cells by housing sterile culture media, mitogens, and fixatives prior to use [Figure 2(a)]. Simple injection of whole blood allows cell-stimulation culture to be performed in reduced gravity conditions, and product stabilization prior to storage, while protecting astronauts from liquid biohazardous materials. Also, the improved WBSD has reconstituted powdered injectable antibiotics by mixing them with diluent liquids [Figure 2(b)]. Although such mixing can readily be performed on

  2. Effect of trabeculectomy on ocular blood flow

    PubMed Central

    Berisha, F; Schmetterer, K; Vass, C; Dallinger, S; Rainer, G; Findl, O; Kiss, B; Schmetterer, L

    2005-01-01

    Background/aim: Current evidence suggests that vascular insufficiencies in the optic nerve head play an important part in the pathogenesis of glaucomatous optic neuropathy. Trabeculectomy is the most common operative procedure for the treatment of medically uncontrolled glaucoma. This study was conducted to investigate whether trabeculectomy may improve ocular haemodynamics. Methods: 30 patients with primary open angle glaucoma about to undergo trabeculectomy were included in the study. Patients were evaluated before surgery and at 2 and 10 weeks after trabeculectomy. Optic nerve head blood flow (OnhBF) was assessed with scanning laser Doppler flowmetry. Fundus pulsation amplitude (FPA) measurements were obtained with laser interferometry. Results: Because of the decrease in intraocular pressure there was a significant increase in ocular perfusion pressure (OPP) following trabeculectomy (18.5% (SD 12.0%) and 19.0% (17.1%) at 2 and 10 weeks postoperatively; p <0.001). A significant increase in OnhBF was observed after trabeculectomy (11.6% (16.4%) and 16.2% (20.2%) for each postoperative visit, respectively; p <0.001). FPA was also significantly higher compared with baseline values (17.2% (17.3%) and 17.4% (16.3%), respectively; p <0.001). A significant association between the increase in OPP and the increase in OnhBF and FPA was observed 10 weeks after surgery (r = 0.47; p = 0.009, and r = 0.50; p = 0.005, respectively). Conclusion: The results of this study suggest that trabeculectomy improves ocular blood flow in patients with chronic open angle glaucoma. PMID:15665350

  3. 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.…

  4. Angiogenesis and Improved Cerebral Blood Flow in the Ischemic Boundary Area Detected by MRI after Administration of Sildenafil to Rats with Embolic Stroke

    PubMed Central

    Li, Lian; Jiang, Quan; Zhang, Li; Ding, Guangliang; Zhang, Zheng Gang; Li, Qingjiang; Ewing, James R.; Lu, Mei; Panda, Swayamprava; Ledbetter, Karyn A.; Whitton, Polly A.; Chopp, Michael

    2007-01-01

    To dynamically investigate the long-term response of an ischemic lesion in rat brain to the administration of sildenafil, male Wistar rats subjected to embolic stroke were treated with sildenafil (n=11) or saline (n=10) at a dose of 10mg/Kg administered subcutaneously 24-hours after stroke and daily for an additional 6-days. Magnetic resonance images were acquired and functional performance was measured in all animals at 1-day, 2-days and weekly for 6-weeks post-stroke. All rats were sacrificed 6-weeks after stroke and endothelial barrier antigen immunostaining was employed for morphological analysis and quantification of cerebral vessels. Map-ISODATA was computed from T1, T2 and T1sat maps. ISODATA derived tissue signatures characterize the degree of ischemic injury. Based on the map-ISODATA calculated at 6-weeks, the ischemic lesion for each animal was divided into two specific regions, the ischemic boundary and ischemic core. The temporal profiles of cerebral blood flow (CBF) and tissue signature were retrospectively tracked in these two regions and were compared with histological evaluation and functional outcome. After 1-week of sildenafil treatment, the ischemic lesion exhibited two significantly different regions, with higher CBF level and correspondingly, lower tissue signature value in the boundary region than in the core region. Sildenafil treatment did not significantly reduce the lesion size, but did enhance angiogenesis. Functional performance was significantly increased after sildenafil treatment compared with the control group. Administration of sildenafil to rats with embolic stroke enhances angiogenesis and selectively increases the CBF level in the ischemic boundary, and improves neurological functional recovery compared to saline-treated rats. PMID:17188664

  5. Acupuncture affects regional blood flow in various organs.

    PubMed

    Uchida, Sae; Hotta, Harumi

    2008-06-01

    In this review, our recent studies using anesthetized animals concerning the neural mechanisms of vasodilative effect of acupuncture-like stimulation in various organs are briefly summarized. Responses of cortical cerebral blood flow and uterine blood flow are characterized as non-segmental and segmental reflexes. Among acupuncture-like stimuli delivered to five different segmental areas of the body; afferent inputs to the brain stem (face) and to the spinal cord at the cervical (forepaw), thoracic (chest or abdomen), lumbar (hindpaw) and sacral (perineum) levels, cortical cerebral blood flow was increased by stimuli to face, forepaw and hindpaw. The afferent pathway of the responses is composed of somatic groups III and IV afferent nerves and whose efferent nerve pathway includes intrinsic cholinergic vasodilators originating in the basal forebrain. Uterine blood flow was increased by cutaneous stimulation of the hindpaw and perineal area, with perineal predominance. The afferent pathway of the response is composed of somatic group II, III and IV afferent nerves and the efferent nerve pathway includes the pelvic parasympathetic cholinergic vasodilator nerves. Furthermore, we briefly summarize vasodilative regulation of skeletal muscle blood flow via a calcitonin gene-related peptide (CGRP) induced by antidromic activation of group IV somatic afferent nerves. These findings in healthy but anesthetized animals may be applicable to understanding the neural mechanisms improving blood flow in various organs following clinical acupuncture. PMID:18604254

  6. Mesoscale simulation of blood flow in microvessels

    NASA Astrophysics Data System (ADS)

    Bagchi, Prosenjit

    2006-11-01

    Computational modeling of blood flow in microvessels (20--500 micron) is a major challenge. Blood in such vessels behaves as a multiphase suspension of deformable particles. Individual red blood cell (RBC), which is highly deformable, must be considered in the model. Multiple cells, often a few thousands in number, must also be considered. We present two dimensional computational simulation of blood flow in 20--300 micron vessels at discharge hematocrit of 10--60 percent 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 of up to 2500 cells is 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 are presented. Also presented are the plug flow velocity profile of blood, the apparent viscosity, and the Fahraeus-Lindqvist effect. The computational results are in good agreement with the experimental results of Bishop et al (2001, 2002) and Pries et al (1992).

  7. Blood flow structure related to red cell flow: determinant of blood fluidity in narrow microvessels.

    PubMed

    McHedlishvili, G; Maeda, N

    2001-02-01

    The review article deals with phenomena of the blood flow structure (structuring) in narrow microvessels-capillaries and the adjacent arterioles and venules. It is particularly focused on the flow behavior of red blood cells (RBCs), namely, on their specific arrangements of mutual interaction while forming definite patterns of self-organized microvascular flow. The principal features of the blood flow structure in microvessels, including capillaries, include axial RBC flow and parietal plasma layer, velocity profile in larger microvessels, plug (or bolus) flow in narrow capillaries, and deformation and specific behavior of the RBCs in the flow. The actual blood flow structuring in microvessels seems to be a most significant factor in the development of pathological conditions, including arterial hypertension, brain and cardiac infarctions, inflammation, and many others. The blood flow structuring might become a basic concept in determining the blood rheological properties and disorders in the narrow microvessels. No solid theoretical (biorheological) basis of the blood flow structuring in microvessel has been found, but in the future it might become a foundation for a better understanding of the mechanisms of these properties under normal and pathological conditions in the narrowest microvessels 5 to 25 microm large. It is also a topic for further biorheological research directed to find the background of actual physiopathological phenomena in the microcirculation. PMID:11281993

  8. 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.

  9. Blood flow distribution in cerebral arteries

    PubMed Central

    Zarrinkoob, Laleh; Ambarki, Khalid; Wåhlin, Anders; Birgander, Richard; Eklund, Anders; Malm, Jan

    2015-01-01

    High-resolution phase–contrast magnetic resonance imaging can now assess flow in proximal and distal cerebral arteries. The aim of this study was to describe how total cerebral blood flow (tCBF) is distributed into the vascular tree with regard to age, sex and anatomic variations. Forty-nine healthy young (mean 25 years) and 45 elderly (mean 71 years) individuals were included. Blood flow rate (BFR) in 21 intra- and extracerebral arteries was measured. Total cerebral blood flow was defined as BFR in the internal carotid plus vertebral arteries and mean cerebral perfusion as tCBF/brain volume. Carotid/vertebral distribution was 72%/28% and was not related to age, sex, or brain volume. Total cerebral blood flow (717±123 mL/min) was distributed to each side as follows: middle cerebral artery (MCA), 21% distal MCA, 6% anterior cerebral artery (ACA), 12%, distal ACA, 4% ophthalmic artery, 2% posterior cerebral artery (PCA), 8% and 20% to basilar artery. Deviating distributions were observed in subjects with ‘fetal' PCA. Blood flow rate in cerebral arteries decreased with increasing age (P<0.05) but not in extracerebral arteries. Mean cerebral perfusion was higher in women (women: 61±8; men: 55±6 mL/min/100 mL, P<0.001). The study describes a new method to outline the flow profile of the cerebral vascular tree, including reference values, and should be used for grading the collateral flow system. PMID:25564234

  10. 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…

  11. 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.

  12. 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.

  13. Blood flow dynamics in the snake spectacle.

    PubMed

    van Doorn, Kevin; Sivak, Jacob G

    2013-11-15

    The eyes of snakes are shielded beneath a layer of transparent integument referred to as the 'reptilian spectacle'. Well adapted to vision by virtue of its optical transparency, it nevertheless retains one characteristic of the integument that would otherwise prove detrimental to vision: its vascularity. Given the potential consequence of spectacle blood vessels on visual clarity, one might expect adaptations to have evolved that mitigate their negative impact. Earlier research demonstrated an adaptation to their spatial layout in only one species to reduce the vessels' density in the region serving the foveal and binocular visual fields. Here, we present a study of spectacle blood flow dynamics and provide evidence of a mechanism to mitigate the spectacle blood vessels' deleterious effect on vision by regulation of blood flow through them. It was found that when snakes are at rest and undisturbed, spectacle vessels undergo cycles of dilation and constriction, such that the majority of the time the vessels are fully constricted, effectively removing them from the visual field. When snakes are presented with a visual threat, spectacle vessels constrict and remain constricted for longer periods than occur during the resting cycles, thus guaranteeing the best possible visual capabilities in times of need. Finally, during the snakes' renewal phase when they are generating a new stratum corneum, the resting cycle is abolished, spectacle vessels remain dilated and blood flow remains strong and continuous. The significance of these findings in terms of the visual capabilities and physiology of snakes is discussed. PMID:24172887

  14. Effects of flow geometry on blood viscoelasticity.

    PubMed

    Thurston, George B; Henderson, Nancy M

    2006-01-01

    The viscoelastic properties of blood are dominated by microstructures formed by red cells. The microstructures are of several types such as irregular aggregates, rouleaux, and layers of aligned cells. The dynamic deformability of the red cells, aggregation tendency, cell concentration, size of confining vessel and rate of flow are determining factors in the microstructure. Viscoelastic properties, viscosity and elasticity, relate to energy loss and storage in flowing blood while relaxation time and Weissenberg number play a role in assessing the importance of the elasticity relative to the viscosity. These effects are shown herein for flow in a large straight cylindrical tube, a small tube, and a porous medium. These cases approximate the geometries of the arterial system: large vessels, small vessels and vessels with many branches and bifurcations. In each case the viscosity, elasticity, relaxation time and Weissenberg number for normal human blood as well as blood with enhanced cell aggregation tendency and diminished cell deformability are given. In the smaller spaces of the microtubes and porous media, the diminished viscosity shows the possible influence of the Fåhraeus-Lindqvist effect and at high shear rates, the viscoelasticity of blood shows dilatancy. This is true for normal, aggregation enhanced and hardened cells. PMID:17148856

  15. Ergot alkaloids decrease rumen epithelial blood flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  16. Hypovolemic shock, pancreatic blood flow, and pancreatitis.

    PubMed

    Robert, J H; Toledano, A E; Toth, L S; Premus, G; Dreiling, D A

    1988-05-01

    Electromagnetic blood flow determinations were carried out on the superior pancreatic duodena (SPDA), the splenic (SA) and the superior mesenteric (SMA) arteries and compared to cardiac output (CO, thermodilution technique) in 12 anesthetized dogs submitted to hypovolemic shock of various duration: 5 dogs underwent a one-hour and 7 a three-hour period of shock. A 50 mm Hg level of mean arterial blood pressure (MABP) was maintained throughout hypovolemia. Dogs were then reinfused. Control preshock values were 4.12 l/min for CO, 38.0 ml/min for SPDA, 405.9 ml/min for SA, and 963.6 ml/min for SMA. SPDA, SA and SMA flows expressed as % of CO amounted to 0.9, 9.8 and 23.4% respectively. No significant changes in SPDA and SMA flows were noted within the first hour of shock. However, from the end of the second hour on, both flows differed significantly (P less than 0.01), SMA increasing from -75.6% of its control value at the end of bleeding to -61.0%, and SPDA decreasing from -75.6 to -86.9%. Similar observations were made when respective flows were considered as % of CO. The SA behaved somewhat in an intermediate fashion. This relative spoliation in pancreatic blood supply as hypovolemia proceeds supports an ischemic etiology of acute pancreatitis (AP), which could account for some of the so-called idiopathic cases of AP. PMID:3385221

  17. Local aggregation characteristics of microscale blood flows

    NASA Astrophysics Data System (ADS)

    Kaliviotis, Efstathios; Sherwood, Joseph M.; Dusting, Jonathan; Balabani, Stavroula

    2015-11-01

    Erythrocyte aggregation (EA) is an important aspect of microvascular flows affecting blood flow and viscosity. Microscale blood flows have been studied extensively in recent years using computational and microfluidic based approaches. However, the relationship between the local structural characteristics of blood and the velocity field has not been quantified. We report simultaneous measurements of the local velocity, aggregation and haematocrit distributions of human erythrocytes flowing in a microchannel. EA was induced using Dextran and flows were imaged using brightfield microscopy. Local aggregation characteristics were investigated using statistical and edge-detection image processing techniques while velocity profiles were obtained using PIV algorithms. Aggregation intensity was found to strongly correlate with local variations in velocity in both the central and wall regions of the channel. The edge detection method showed that near the side wall large aggregates are associated with high local velocities and low local shear rates. In the central region large aggregates occurred in regions of low velocity and high erythrocyte concentration. The results demonstrate the combined effect of haematocrit and velocity distributions on local aggregation characteristics.

  18. Modeling of blood flow in arterial trees.

    PubMed

    Anor, Tomer; Grinberg, Leopold; Baek, Hyoungsu; Madsen, Joseph R; Jayaraman, Mahesh V; Karniadakis, George E

    2010-01-01

    Advances in computational methods and medical imaging techniques have enabled accurate simulations of subject-specific blood flows at the level of individual blood cell and in complex arterial networks. While in the past, we were limited to simulations with one arterial bifurcation, the current state-of-the-art is simulations of arterial networks consisting of hundreds of arteries. In this paper, we review the advances in methods for vascular flow simulations in large arterial trees. We discuss alternative approaches and validity of various assumptions often made to simplify the modeling. To highlight the similarities and discrepancies of data computed with different models, computationally intensive three-dimensional (3D) and inexpensive one-dimensional (1D) flow simulations in very large arterial networks are employed. Finally, we discuss the possibilities, challenges, and limitations of the computational methods for predicting outcomes of therapeutic interventions for individual patients. PMID:20836052

  19. [Blood regulation in Brazil: contextualization for improvement].

    PubMed

    Silva Júnior, João Batista; Costa, Christiane da Silva; Baccara, João Paulo de Araújo

    2015-10-01

    The use of blood products as essential medicines and the recognition of the high risk associated with blood transfusions require governments to take regulatory action with a focus on quality and safety. In this scenario, regulatory agencies play an essential role in socially advancing the guarantee that blood components will be produced according to current operating rules. Thus, in the effort to manage sanitary risks involved in the processing and use of blood, the Brazilian regulatory model, based on the construction of a national blood policy overseen by the State, has undergone conceptual improvement and review of the tools employed to achieve its goals. With the inclusion of good manufacturing practices as part of the Brazilian norms, as recommended by the World Health Organization, the country has moved forward in its view of blood facilities as manufacturing centers producing blood-derived biologics for therapeutic applications. It has also strengthened the need to develop safety mechanisms for blood donors and recipients. The development of a State-coordinated national blood policy and the institution of a national surveillance system with legitimate power of inspection are essential elements used in Brazil to guarantee the amount, quality, safety, and timeliness of blood supply to the population. The present article aims to discuss the present context of the blood regulatory model in Brazil so as to identify the challenges for improvement of this model. PMID:26758225

  20. Ocular Blood Flow and Normal Tension Glaucoma

    PubMed Central

    Fan, Ning; Wang, Pei; Tang, Li; Liu, Xuyang

    2015-01-01

    Normal tension glaucoma (NTG) is known as a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and glaucomatous visual field loss, even though the intraocular pressure (IOP) does not exceed the normal range. The pathophysiology of NTG remains largely undetermined. It is hypothesized that the abnormal ocular blood flow is involved in the pathogenesis of this disease. A number of evidences suggested that the vascular factors played a significant role in the development of NTG. In recent years, the new imaging techniques, fluorescein angiography, color Doppler imaging (CDI), magnetic resonance imaging (MRI), and laser speckle flowgraphy (LSFG), have been used to evaluate the ocular blood flow and blood vessels, and the impaired vascular autoregulation was found in patients with NTG. Previous studies showed that NTG was associated with a variety of systemic diseases, including migraine, Alzheimer's disease, primary vascular dysregulation, and Flammer syndrome. The vascular factors were involved in these diseases. The mechanisms underlying the abnormal ocular blood flow in NTG are still not clear, but the risk factors for glaucomatous optic neuropathy likely included oxidative stress, vasospasm, and endothelial dysfunction. PMID:26558263

  1. Dexmedetomidine decreases the oral mucosal blood flow.

    PubMed

    Kawaai, Hiroyoshi; Yoshida, Kenji; Tanaka, Eri; Togami, Kohei; Tada, Hitoshi; Ganzberg, Steven; Yamazaki, Shinya

    2013-12-01

    There is an abundance of blood vessels in the oral cavity, and intraoperative bleeding can disrupt operations. There have been some interesting reports about constriction of vessels in the oral cavity, one of which reported that gingival blood flow in cats is controlled by sympathetic α-adrenergic fibres that are involved with vasoconstriction. Dexmedetomidine is a sedative and analgesic agent that acts through the α-2 adrenoceptor, and is expected to have a vasoconstrictive action in the oral cavity. We have focused on the relation between the effects of α-adrenoceptors by dexmedetomidine and vasoconstriction in oral tissues, and assessed the oral mucosal blood flow during sedation with dexmedetomidine. The subjects comprised 13 healthy male volunteers, sedated with dexmedetomidine in a loading dose of 6 μg/kg/h for 10 min and a continuous infusion of 0.7 μg/kg/h for 32 min. The mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), systemic vascular resistance (SVR), and palatal mucosal blood flow (PMBF) were measured at 0, 5, 10, 12, 22, and 32 min after the start of the infusion. The HR, CO, and PBMF decreased significantly during the infusion even though there were no differences in the SV. The SVR increased significantly but the PMBF decreased significantly. In conclusion, PMBF was reduced by the mediating effect of dexmedetomidine on α-2 adrenoceptors. PMID:23958351

  2. Ocular Blood Flow and Normal Tension Glaucoma.

    PubMed

    Fan, Ning; Wang, Pei; Tang, Li; Liu, Xuyang

    2015-01-01

    Normal tension glaucoma (NTG) is known as a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and glaucomatous visual field loss, even though the intraocular pressure (IOP) does not exceed the normal range. The pathophysiology of NTG remains largely undetermined. It is hypothesized that the abnormal ocular blood flow is involved in the pathogenesis of this disease. A number of evidences suggested that the vascular factors played a significant role in the development of NTG. In recent years, the new imaging techniques, fluorescein angiography, color Doppler imaging (CDI), magnetic resonance imaging (MRI), and laser speckle flowgraphy (LSFG), have been used to evaluate the ocular blood flow and blood vessels, and the impaired vascular autoregulation was found in patients with NTG. Previous studies showed that NTG was associated with a variety of systemic diseases, including migraine, Alzheimer's disease, primary vascular dysregulation, and Flammer syndrome. The vascular factors were involved in these diseases. The mechanisms underlying the abnormal ocular blood flow in NTG are still not clear, but the risk factors for glaucomatous optic neuropathy likely included oxidative stress, vasospasm, and endothelial dysfunction. PMID:26558263

  3. Measurement of Liver Blood Flow: A Review

    PubMed Central

    Stansby, G. P.; Hobbs, K. E. F.; Hawkes, D. J.; Colchester, A. C. F.

    1991-01-01

    The study of hepatic haemodynamics is of importance in understanding both hepatic physiology and disease processes as well as assessing the effects of portosystemic shunting and liver transplantation. The liver has the most complicated circulation of any organ and many physiological and pathological processes can affect it1,2. This review surveys the methods available for assessing liver blood flow, examines the different parameters being measured and outlines problems of applicability and interpretation for each technique. The classification of these techniques is to some extent arbitrary and several so called “different” methods may share certain common principles. The methods reviewed have been classified into two groups (Table 1): those primarily reflecting flow through discrete vessels or to the whole organ and those used to assess local microcirculatory blood flow. All techniques have their advantages and disadvantages and in some situations a combination may provide the most information. In addition, because of the many factors affecting liver blood flow and sinusoidal perfusion, readings in a single subject may vary depending on positioning, recent food intake, anxiety, anaesthesia and drug therapy. This must be borne in mind if different studies are to be meaningfully compared. PMID:1931785

  4. Global impairment of coronary blood flow in the setting of acute coronary syndromes (a RESTORE substudy). Randomized Efficacy Study of Tirofiban for Outcomes and Restenosis.

    PubMed

    Gibson, C M; Goel, M; Murphy, S A; Dotani, I; Marble, S J; Deckelbaum, L I; Dodge, J T; King, S B

    2000-12-15

    Acute coronary syndromes result in a global impairment of coronary blood flow with nonculprit artery blood flow being associated with culprit artery flow and vice versa. Improvements in nonculprit artery flow are related to improvements in culprit artery flow after percutaneous intervention; nonculprit arteries with abnormal flow sustain greater improvements in their flow after culprit artery intervention. PMID:11113417

  5. X-ray PIV measurements of blood flows without tracer particles

    NASA Astrophysics Data System (ADS)

    Kim, Guk Bae; Lee, Sang Joon

    2006-08-01

    We analyzed the non-Newtonian flow characteristics of blood moving in a circular tube flow using an X-ray PIV method and compared the experimental results with hemodynamic models. The X-ray PIV method was improved for measuring quantitative velocity fields of blood flows using a coherent synchrotron X-ray. Without using any contrast media, this method can visualize flow pattern of blood by enhancing the phase-contrast and interference characteristics of blood cells. The enhanced X-ray images were achieved by optimizing the sample-to-scintillator distance, the sample thickness, and hematocrit in detail. The quantitative velocity fields of blood flows inside opaque conduits were obtained by applying a two-frame PIV algorithm to the X-ray images of the blood flows. The measured velocity data show typical features of blood flow such as the yield stress and shear-thinning effects.

  6. Caffeine reduces myocardial blood flow during exercise.

    PubMed

    Higgins, John P; Babu, Kavita M

    2013-08-01

    Caffeine consumption has been receiving increased interest from both the medical and lay press, especially given the increased amounts now available in energy products. Acute ingestion of caffeine usually increases cardiac work; however, caffeine impairs the expected proportional increase in myocardial blood flow to match this increased work of the heart, most notably during exercise. This appears to be mainly due to caffeine's effect on blocking adenosine-induced vasodilatation in the coronary arteries in normal healthy subjects. This review summarizes the available medical literature specifically relating to pure caffeine tablet ingestion and reduced exercise coronary blood flow, and suggests possible mechanisms. Further studies are needed to evaluate this effect for other common caffeine-delivery systems, including coffee, energy beverages, and energy gels, which are often used for exercise performance enhancement, especially in teenagers and young athletes. PMID:23764265

  7. Deterministic Aperiodic Sickle Cell Blood Flows

    NASA Astrophysics Data System (ADS)

    Atsaves, Louis; Harris, Wesley

    2013-11-01

    In this paper sickle cell blood flow in the capillaries is modeled as a hydrodynamical system. The hydrodynamical system consists of the axisymmetric unsteady, incompressible Navier-Stokes equations and a set of constitutive equations for oxygen transport. Blood cell deformation is not considered in this paper. The hydrodynamical system is reduced to a system of non-linear partial differential equations that are then transformed into a system of three autonomous non-linear ordinary differential equations and a set of algebraic equations. We examine the hydrodynamical system to discern stable/unstable, periodic/nonperiodic, reversible/irreversible properties of the system. The properties of the solutions are driven in large part by the coefficients of the governing system of equations. These coefficients depend on the physiological properties of the sickle cell blood. The chaotic nature of the onset of crisis in sickle cell patients is identified. Research Assistant.

  8. 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.

  9. Gender Differences in Ocular Blood Flow

    PubMed Central

    Schmidl, Doreen; Garhöfer, Gerhard; Popa-Cherecheanu, Alina

    2015-01-01

    Gender medicine has been a major focus of research in recent years. The present review focuses on gender differences in the epidemiology of the most frequent ocular diseases that have been found to be associated with impaired ocular blood flow, such as age-related macular degeneration, glaucoma and diabetic retinopathy. Data have accumulated indicating that hormones have an important role in these diseases, since there are major differences in the prevalence and incidence between men and pre- and post-menopausal women. Whether this is related to vascular factors is, however, not entirely clear. Interestingly, the current knowledge about differences in ocular vascular parameters between men and women is sparse. Although little data is available, estrogen, progesterone and testosterone are most likely important regulators of blood flow in the retina and choroid, because they are key regulators of vascular tone in other organs. Estrogen seems to play a protective role since it decreases vascular resistance in large ocular vessels. Some studies indicate that hormone therapy is beneficial for ocular vascular disease in post-menopausal women. This evidence is, however, not sufficient to give any recommendation. Generally, remarkably few data are available on the role of sex hormones on ocular blood flow regulation, a topic that requires more attention in the future. PMID:24892919

  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. Red blood cell in simple shear flow

    NASA Astrophysics Data System (ADS)

    Chien, Wei; Hew, Yayu; Chen, Yeng-Long

    2013-03-01

    The dynamics of red blood cells (RBC) in blood flow is critical for oxygen transport, and it also influences inflammation (white blood cells), thrombosis (platelets), and circulatory tumor migration. The physical properties of a RBC can be captured by modeling RBC as lipid membrane linked to a cytoskeletal spectrin network that encapsulates cytoplasm rich in hemoglobin, with bi-concave equilibrium shape. Depending on the shear force, RBC elasticity, membrane viscosity, and cytoplasm viscosity, RBC can undergo tumbling, tank-treading, or oscillatory motion. We investigate the dynamic state diagram of RBC in shear and pressure-driven flow using a combined immersed boundary-lattice Boltzmann method with a multi-scale RBC model that accurately captures the experimentally established RBC force-deformation relation. It is found that the tumbling (TU) to tank-treading (TT) transition occurs as shear rate increases for cytoplasm/outer fluid viscosity ratio smaller than 0.67. The TU frequency is found to be half of the TT frequency, in agreement with experiment observations. Larger viscosity ratios lead to the disappearance of stable TT phase and unstable complex dynamics, including the oscillation of the symmetry axis of the bi-concave shape perpendicular to the flow direction. The dependence on RBC bending rigidity, shear modulus, the order of membrane spectrin network and fluid field in the unstable region will also be discussed.

  12. 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.

  13. Operative blood transfusion quality improvement audit

    PubMed Central

    Al Sohaibani, Mazen; Al Malki, Assaf; Pogaku, Venumadhav; Al Dossary, Saad; Al Bernawi, Hanan

    2014-01-01

    Context: To determine how current anesthesia team handless the identification of surgical anaesthetized patient (right patient). And the check of blood unit before collecting and immediately before blood administration (right blood) in operating rooms where nurses have minimal duties and responsibility to handle blood for transfusion in anaesthetized patients. Aims: To elicit the degree of anesthesia staff compliance with new policies and procedures for anaesthetized surgical patient the blood transfusion administration. Settings and Design: Setting: A large tertiary care reference and teaching hospital. Design: A prospective quality improvement. Elaboration on steps for administration of transfusion from policies and procedures to anaesthetized patients; and analysis of the audit forms for conducted transfusions. Subjects and Methods: An audit form was used to get key performance indicators (KPIs) observed in all procedures involve blood transfusion and was ticked as item was met, partially met, not met or not applicable. Statistical Analysis Used: Descriptive statistics as number and percentage Microsoft excel 2003. Central quality improvement committee presented the results in number percentage and graphs. Results: The degree of compliance in performing the phases of blood transfusion by anesthesia staff reached high percentage which let us feel certain that the quality is assured that the internal policy and procedures (IPP) are followed in the great majority of all types of red cells and other blood products transfusion from the start of requesting the blood or blood product to the prescript of checking the patient in the immediate post-transfusion period. Conclusions: Specific problem area of giving blood transfusion to anaesthetized patient was checking KPI concerning the phases of blood transfusion was audited and assured the investigators of high quality performance in procedures of transfusion. PMID:25886107

  14. Restoring Blood Flow Beats Exercise for Poor Leg Circulation

    MedlinePlus

    ... news/fullstory_158683.html Restoring Blood Flow Beats Exercise for Poor Leg Circulation Opening vessels could prevent ... restore blood flow may have greater benefits than exercise, preliminary research suggests. People with peripheral artery disease ( ...

  15. 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. PMID:26071649

  16. Gender differences in regional cerebral blood flow

    SciTech Connect

    Gur, R.E.; Gur, R.C. )

    1990-01-01

    Gender differences have been noted in neurobehavioral studies. The 133xenon inhalation method for measuring regional cerebral blood flow (rCBF) can contribute to the understanding of the neural basis of gender differences in brain function. Few studies have examined gender differences in rCBF. In studies of normal subjects, women have higher rates of CBF than men, and this is related to age. Usually by the sixth decade men and women have similar flow rates. Fewer studies on rCBF in schizophrenia have examined sex differences. The pattern of higher flows for females maintains, but its correlates with gender differences in clinical as well as other parameters of brain function remain to be examined.

  17. Foetal placental blood flow in the lamb

    PubMed Central

    Faber, J. Job; Green, Thomas J.

    1972-01-01

    1. Fifteen sheep foetuses of 1·5-5·2 kg body weight were prepared with indwelling arterial and venous catheters for experimentation one to six days later. 2. Unanaesthetized foetuses were found to have mean arterial and central venous blood pressures of 40 ± 1·5 (S.E. of mean) and 2·0 ± 0·3 (S.E. of mean) mm Hg respectively, compared to intra-uterine pressure. Intra-uterine pressure was 16 ± 0·8 (S.E. of mean) mm Hg with respect to atmospheric pressure at mid-uterine level. 3. Mean placental blood flow of the foetuses was 199 ± 20 (S.E. of mean) ml./(min.kg body wt.). Mean cardiac output in eleven of the foetuses was 658 ± 102 (S.E. of mean) ml./(min.kg). 4. Mean foetal and maternal colloid osmotic pressures were 17·5 ± 0·7 (S.E. of mean) and 20·5 ± 0·6 (S.E. of mean) mm Hg respectively at 38° C. 5. Intravenous infusions into six ewes of 1·8 mole of mannitol and 0·4 mole of NaCl resulted in significant increases in foetal plasma osmolarity, sodium, potassium, and haemoglobin concentrations, without detectable transfer of mannitol to the foetal circulation. 6. In the sheep placenta there is osmotic and hydrostatic equilibration of water. As a consequence, there should be an interaction between foetal placental blood flow and foetal water exchange with the maternal circulation. It was concluded that this interaction tends to stabilize foetal placental blood flow. PMID:5039279

  18. Unsteady Flow in Stenotic Blood Vessels

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

    Recent studies show that many heart attacks and strokes occur from sudden rupture of partially occluding atherosclerotic plaque rather than total vessel occlusion. Our goal is to understand how the mechanical forces induced by blood flow on specific plaque deposits makes them vulnerable to rupture. Models of severely stenotic carotid bifurcations are created from MR images and grids generated for the flow domains. The three-dimensional, unsteady, incompressible Navier-Stokes equations in finite-volume form are solved numerically using physiological boundary conditions. During systole a high velocity jet forms at the stenotic throat in one of the branches, and a long recirculation zone is observed downstream of the plaque. During diastole the flow is more stagnant. The flow is highly three-dimensional and unsteady with chaotic streamlines. Whereas flow in healthy arteries is laminar, irregular geometries and sharp changes in vessel diameter of a severely stenotic artery significantly disrupt the flow, with consequences for shear and normal wall stresses at the wall, and important implications for plaque stability. Supported by NIH Grant HL61823

  19. Regional cerebral blood flow in childhood headache

    SciTech Connect

    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, 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.

  20. Myocardial Ischemia: Lack of Coronary Blood Flow or Myocardial Oxygen Supply/Demand Imbalance?

    PubMed

    Heusch, Gerd

    2016-07-01

    Regional myocardial blood flow and contractile function in ischemic myocardium are well matched, and there is no evidence for an oxygen supply/demand imbalance. Thus, myocardial ischemia is lack of coronary blood flow with electric, functional, metabolic, and structural consequences for the myocardium. All therapeutic interventions must aim to improve blood flow to ischemic myocardium as much and as quickly as possible. PMID:27390331

  1. Renal pericytes: regulators of medullary blood flow

    PubMed Central

    Kennedy-Lydon, T M; Crawford, C; Wildman, S S P; Peppiatt-Wildman, C M

    2013-01-01

    Regulation of medullary blood flow (MBF) is essential in maintaining normal kidney function. Blood flow to the medulla is supplied by the descending vasa recta (DVR), which arise from the efferent arterioles of juxtamedullary glomeruli. DVR are composed of a continuous endothelium, intercalated with smooth muscle-like cells called pericytes. Pericytes have been shown to alter the diameter of isolated and in situ DVR in response to vasoactive stimuli that are transmitted via a network of autocrine and paracrine signalling pathways. Vasoactive stimuli can be released by neighbouring tubular epithelial, endothelial, red blood cells and neuronal cells in response to changes in NaCl transport and oxygen tension. The experimentally described sensitivity of pericytes to these stimuli strongly suggests their leading role in the phenomenon of MBF autoregulation. Because the debate on autoregulation of MBF fervently continues, we discuss the evidence favouring a physiological role for pericytes in the regulation of MBF and describe their potential role in tubulo-vascular cross-talk in this region of the kidney. Our review also considers current methods used to explore pericyte activity and function in the renal medulla. PMID:23126245

  2. Integrative regulation of human brain blood flow

    PubMed Central

    Willie, Christopher K; Tzeng, Yu-Chieh; Fisher, Joseph A; Ainslie, Philip N

    2014-01-01

    Herein, we review mechanisms regulating cerebral blood flow (CBF), with specific focus on humans. We revisit important concepts from the older literature and describe the interaction of various mechanisms of cerebrovascular control. We amalgamate this broad scope of information into a brief review, rather than detailing any one mechanism or area of research. The relationship between regulatory mechanisms is emphasized, but the following three broad categories of control are explicated: (1) the effect of blood gases and neuronal metabolism on CBF; (2) buffering of CBF with changes in blood pressure, termed cerebral autoregulation; and (3) the role of the autonomic nervous system in CBF regulation. With respect to these control mechanisms, we provide evidence against several canonized paradigms of CBF control. Specifically, we corroborate the following four key theses: (1) that cerebral autoregulation does not maintain constant perfusion through a mean arterial pressure range of 60–150 mmHg; (2) that there is important stimulatory synergism and regulatory interdependence of arterial blood gases and blood pressure on CBF regulation; (3) that cerebral autoregulation and cerebrovascular sensitivity to changes in arterial blood gases are not modulated solely at the pial arterioles; and (4) that neurogenic control of the cerebral vasculature is an important player in autoregulatory function and, crucially, acts to buffer surges in perfusion pressure. Finally, we summarize the state of our knowledge with respect to these areas, outline important gaps in the literature and suggest avenues for future research. PMID:24396059

  3. Integrative regulation of human brain blood flow.

    PubMed

    Willie, Christopher K; Tzeng, Yu-Chieh; Fisher, Joseph A; Ainslie, Philip N

    2014-03-01

    Herein, we review mechanisms regulating cerebral blood flow (CBF), with specific focus on humans. We revisit important concepts from the older literature and describe the interaction of various mechanisms of cerebrovascular control. We amalgamate this broad scope of information into a brief review, rather than detailing any one mechanism or area of research. The relationship between regulatory mechanisms is emphasized, but the following three broad categories of control are explicated: (1) the effect of blood gases and neuronal metabolism on CBF; (2) buffering of CBF with changes in blood pressure, termed cerebral autoregulation; and (3) the role of the autonomic nervous system in CBF regulation. With respect to these control mechanisms, we provide evidence against several canonized paradigms of CBF control. Specifically, we corroborate the following four key theses: (1) that cerebral autoregulation does not maintain constant perfusion through a mean arterial pressure range of 60-150 mmHg; (2) that there is important stimulatory synergism and regulatory interdependence of arterial blood gases and blood pressure on CBF regulation; (3) that cerebral autoregulation and cerebrovascular sensitivity to changes in arterial blood gases are not modulated solely at the pial arterioles; and (4) that neurogenic control of the cerebral vasculature is an important player in autoregulatory function and, crucially, acts to buffer surges in perfusion pressure. Finally, we summarize the state of our knowledge with respect to these areas, outline important gaps in the literature and suggest avenues for future research. PMID:24396059

  4. Numerical analysis of blood flow in the clearance regions of a continuous flow artificial heart pump.

    PubMed

    Anderson, J; Wood, H G; Allaire, P E; Olsen, D B

    2000-06-01

    The CFVAD3 is the third prototype of a continuous flow ventricular assist device being developed for implantation in humans. The pump consists of a fully shrouded 4-blade impeller supported by magnetic bearings. On either side of this suspended rotating impeller is a small clearance region through which the blood flows. The spacing and geometry of these clearance regions are very important to the successful operation of this blood pump. Computational fluid dynamics (CFD) solutions for this flow were obtained using TascFlow, a software package available from AEA Technology, U.K. Flow in these clearance regions was studied parametrically by varying the size of the clearance, the blood flow rate into the pump, and the rotational speed of the pump. The numerical solutions yield the direction and magnitude of the flow and the dynamic pressure. Experimentally measured pump flow rates are compared to the numerical study. The results of the study provide guidance for improving pump efficiency. It is determined that current clearances can be significantly reduced to improve pump efficiency without negative impacts. PMID:10886072

  5. Integration and Modulation of Intercellular Signaling Underlying Blood Flow Control

    PubMed Central

    Segal, Steven S.

    2015-01-01

    Vascular resistance networks control tissue blood flow in concert with regulating arterial perfusion pressure. In response to increased metabolic demand, vasodilation arising in arteriolar networks ascends to encompass proximal feed arteries. By reducing resistance upstream, ascending vasodilation (AVD) increases blood flow into the microcirculation. Once initiated [e.g., through local activation of K+ channels in endothelial cells (ECs)], hyperpolarization is conducted through gap junctions along the endothelium. Via EC projections through the internal elastic lamina, hyperpolarization spreads into the surrounding smooth muscle cells (SMCs) through myoendothelial gap junctions (MEGJs) to promote their relaxation. Intercellular signaling through electrical signal transmission (i.e., cell-to-cell conduction) can thereby coordinate vasodilation along and among the branches of microvascular resistance networks. Perivascular sympathetic nerve fibers course through the adventitia and release norepinephrine to stimulate SMCs via α-adrenoreceptors to produce contraction. In turn, SMCs can signal ECs through MEGJs to activate K+ channels and attenuate sympathetic vasoconstriction. Activation of K+ channels along the endothelium will dissipate electrical signal transmission and inhibit AVD, thereby restricting blood flow into the microcirculation while maintaining peripheral resistance and perfusion pressure. This review explores the origins and nature of intercellular signaling governing blood flow control in skeletal muscle with respect to the interplay between AVD and sympathetic innervation. Whereas these interactions are integral to physical daily activity and athletic performance, resolving the interplay between respective signaling events provides insight into how selective interventions can improve tissue perfusion and oxygen delivery during vascular disease. PMID:26368324

  6. Quantitative Assessment of Myocardial Blood Flow with SPECT.

    PubMed

    Petretta, Mario; Storto, Giovanni; Pellegrino, Teresa; Bonaduce, Domenico; Cuocolo, Alberto

    2015-01-01

    The quantitative assessment of myocardial blood flow (MBF) and coronary flow reserve (CFR) may be useful for the functional evaluation of coronary artery disease, allowing judgment of its severity, tracking of disease progression, and evaluation of the anti-ischemic efficacy of therapeutic strategies. Quantitative estimates of myocardial perfusion and CFR can be derived from single-photon emission computed tomography (SPECT) myocardial perfusion images by use of equipment, tracers, and techniques that are available in most nuclear cardiology laboratories. However, this method underestimates CFR, particularly at high flow rates. The recent introduction of cardiac-dedicated gamma cameras with solid-state detectors provides very fast perfusion imaging with improved resolution, allowing fast acquisition of serial dynamic images during the first pass of a flow agent. This new technology holds great promise for MBF and CFR quantification with dynamic SPECT. Future studies will clarify the effectiveness of dynamic SPECT flow imaging. PMID:25560327

  7. Optical coherence Doppler tomography for quantitative cerebral blood flow imaging

    PubMed Central

    You, Jiang; Du, Congwu; Volkow, Nora D.; Pan, Yingtian

    2014-01-01

    Optical coherence Doppler tomography (ODT) is a promising neurotechnique that permits 3D imaging of the cerebral blood flow (CBF) network; however, quantitative CBF velocity (CBFv) imaging remains challenging. Here we present a simple phase summation method to enhance slow capillary flow detection sensitivity without sacrificing dynamic range for fast flow and vessel tracking to improve angle correction for absolute CBFv quantification. Flow phantom validation indicated that the CBFv quantification accuracy increased from 15% to 91% and the coefficient of variation (CV) decreased 9.3-fold; in vivo mouse brain validation showed that CV decreased 4.4-/10.8- fold for venular/arteriolar flows. ODT was able to identify cocaine-elicited microischemia and quantify CBFv disruption in branch vessels and capillaries that otherwise would have not been possible. PMID:25401033

  8. Radiohalogenated thienylethylamine derivatives for evaluating local cerebral blood flow

    SciTech Connect

    Goodman, M.M.; Knapp, F.F. Jr.

    1988-12-22

    An improved method of chemical synthesis of radiohalogenated thienylethylamine derivatives useful in brain imaging is described. These 5-halo-thiophene-2-isopropyl amines readily cross the blood- brain barrier and are retained in the brain for a sufficient length of time to allow evaluation of regional blood flow in the cerebrum. The advantages of the invention include a simpler synthesis route and a final compound which is less diluted with nonradioactive halogen. Use of this invention will allow clearer radioimaging or lower radiation doses to the patient, depending on the objective. 2 figs., 1 tab. (MHB)

  9. A Reconstruction Method of Blood Flow Velocity in Left Ventricle Using Color Flow Ultrasound

    PubMed Central

    Jang, Jaeseong; Ahn, Chi Young; Jeon, Kiwan; Heo, Jung; Lee, DongHak; Choi, Jung-il

    2015-01-01

    Vortex flow imaging is a relatively new medical imaging method for the dynamic visualization of intracardiac blood flow, a potentially useful index of cardiac dysfunction. A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color flow images compiled from ultrasound measurements. In this paper, a 2D incompressible Navier-Stokes equation with a mass source term is proposed 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. The boundary conditions to solve the system of equations are derived from the dimensions of the ventricle extracted from 2D echocardiography data. The performance of the proposed method is evaluated numerically using synthetic flow data acquired from simulating left ventricle flows. The numerical simulations show the feasibility and potential usefulness of the proposed method of reconstructing the intracardiac flow fields. Of particular note is the finding that the mass source term in the proposed model improves the reconstruction performance. PMID:26078773

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

    SciTech Connect

    Cohan, S.L.; Mun, S.K.; Petite, J.; Correia, J.; Tavelra Da Silva, A.T.; Waldhorn, R.E.

    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 may indicate the onset of irreversible brain damage.

  11. Thermoregulatory control of finger blood flow

    NASA Technical Reports Server (NTRS)

    Wenger, C. B.; Roberts, M. F.; Nadel, E. R.; Stolwijk, J. A. J.

    1975-01-01

    In the present experiment, exercise was used to vary internal temperature and ambient air heat control was used to vary skin temperature. Finger temperature was fixed at about 35.7 C. Esophageal temperature was measured with a thermocouple at the level of the left atrium, and mean skin temperature was calculated from a weighted mean of thermocouple temperatures at different skin sites. Finger blood flow was measured by electrocapacitance plethysmography. An equation in these quantities is given which accounts for the data garnered.

  12. Dynamic radioisotope bone imaging as a noninvasive indicator of canine tibial blood flow

    SciTech Connect

    Nutton, R.W.; Fitzgerald, R.H. Jr.; Brown, M.L.; Kelly, P.J.

    1984-01-01

    The relative values of dynamic and static bone imaging with hydroxymethylenediphosphonate technetium /sup 99m/ (/sup 99m/Tc HDP) as an indicator of bone blood flow was investigated in the tibia of mature dogs. The dynamic bone scan consisted of 60 1-s images formed after the intravenous injection of /sup 99m/Tc HDP, and the static bone scan was a 45-min uptake image. Blood flow to the tibia was determined by using radioactively labeled microspheres. Studies were carried out in control dogs, in dogs in which blood flow was increased in one leg with ATP, and in dogs in which blood flow was decreased in one leg with norepinephrine. A significant linear relationship between the dynamic scan values and bone blood flow was found at a wide range of blood flow rates. When blood flow increased by more than 50%, the effects of diffusion limitation were seen in the static scans: increase in tracer uptake was disproportionately small for a significant increase in blood flow. There is no method currently available for estimating bone blood flow by a noninvasive technique. The method described here may be useful for providing a semiquantitative measure of bone blood flow. This improved versatility of bone imaging may have a role in the management of osteomyelitis or complicated fractures, or in assessing the viability of vascularized bone grafts.

  13. Effects of vasoactive stimuli on blood flow to choroid plexus

    SciTech Connect

    Faraci, F.M.; Mayhan, W.G.; Williams, J.K.; Heistad, D.D. )

    1988-02-01

    The goal of this study was to examine effects of vasoactive stimuli on blood flow to choroid plexus. The authors used microspheres to measure blood flow to choroid plexus and cerebrum in anesthetized dogs and rabbits. A critical assumption of the microsphere method is that microspheres do not pass through arteriovenous shunts. Blood flow values obtained with simultaneous injection of 15- and 50-{mu}m microspheres were similar, which suggest that shunting of 15-{mu}m microspheres was minimal. Blood flow to choroid plexus under control conditions was 287 {plus minus} 26 (means {plus minus} SE) ml {center dot} min{sup {minus}1} {center dot} 100 g{sup {minus}1} in dogs and 385 {plus minus} 73 ml {center dot} min{sup {minus}1} 100 g{sup {minus}1} in rabbits. Consecutive measurements under control conditions indicated that values for blood flow are reproducible. Adenosine did not alter blood flow to cerebrum but increased blood flow to choroid plexus two- to threefold in dogs and rabbits. Norepinephrine and phenylephrine did not affect blood flow to choroid plexus and cerebrum but decreased blood flow to choroid plexus by {approx} 50%. The authors suggest that (1) the microsphere method provides reproducible valid measurements of blood flow to the choroid plexus in dogs and rabbits and (2) vasoactive stimuli may have profoundly different effects on blood flow to choroid plexus and cerebrum.

  14. Mechanical axial flow blood pump to support cavopulmonary circulation.

    PubMed

    Throckmorton, A L; Kapadia, J; Madduri, D

    2008-11-01

    We are developing a collapsible, percutaneously inserted, axial flow blood pump to support the cavopulmonary circulation in infants with a failing single ventricle physiology. An initial design of the impeller for this axial flow blood pump was performed using computational fluid dynamics analysis, including pressure-flow characteristics, scalar stress estimations, blood damage indices, and fluid force predictions. A plastic prototype was constructed for hydraulic performance testing, and these experimental results were compared with the numerical predictions. The numerical predictions and experimental findings of the pump performance demonstrated a pressure generation of 2-16 mm Hg for 50-750 ml/min over 5,500-7,500 RPM with deviation found at lower rotational speeds. The axial fluid forces remained below 0.1 N, and the radial fluid forces were determined to be virtually zero due to the centered impeller case. The scalar stress levels remained below 250 Pa for all operating conditions. Blood damage analysis yielded a mean residence time of the released particles, which was found to be less than 0.4 seconds for both flow rates that were examined, and a maximum residence time was determined to be less than 0.8 seconds. We are in the process of designing a cage with hydrodynamically shaped filament blades to act as a diffuser and optimizing the impeller blade shape to reduce the flow vorticity at the pump outlet. This blood pump will improve the clinical treatment of patients with failing Fontan physiology and provide a unique catheter-based therapeutic approach as a bridge to recovery or transplantation. PMID:19089799

  15. Heat transfer analysis for peripheral blood flow measurement system

    NASA Astrophysics Data System (ADS)

    Nagata, Koji; Hattori, Hideharu; Sato, Nobuhiko; Ichige, Yukiko; Kiguchi, Masashi

    2009-06-01

    Some disorders such as circulatory disease and metabolic abnormality cause many problems to peripheral blood flow condition. Therefore, frequent measurement of the blood flow condition is bound to contribute to precaution against those disorders and to control of conditions of the diseases. We propose a convenient means of blood flow volume measurement at peripheral part, such as fingertips. Principle of this measurement is based on heat transfer characteristics of peripheral part containing the blood flow. Transition response analysis of skin surface temperature has provided measurement model of the peripheral blood flow volume. We developed the blood flow measurement system based on that model and evaluated it by using artificial finger under various temperature conditions of ambience and internal fluid. The evaluation results indicated that proposed method could estimate the volume of the fluid regardless of temperature condition of them. Finally we applied our system to real finger testing and have obtained results correlated well with laser Doppler blood flow meter values.

  16. Blood-Flow Magnetic Resonance Imaging of Retinal Degeneration

    PubMed Central

    Li, Yingxia; Cheng, Haiying; Shen, Qiang; Kim, Moon; Thule, Peter M; Olson, Darin E; Pardue, Machelle T; Duong, Timothy Q

    2009-01-01

    Purpose To investigate quantitative basal blood flow, hypercapnia- and hyperoxia-induced blood-flow changes in the retinas of the Royal-College-of-Surgeons (RCS) rats with spontaneous retinal degeneration and to compare with those of normal rat retinas. Methods Experiments were performed on male RCS rats at post-natal day P90 (n=4), P220 (n=5) and age-matched controls at P90 (n=7) and P220 (n=6). Hyperoxic (100% O2) and hypercapnic (5% CO2, 21% O2, balance N2) challenges were used to modulate blood flow. Quantitative baseline blood flow, hypercapnia- and hyperoxia-induced blood-flow changes in the retinas were imaged using continuous arterial-spin-labeling magnetic resonance imaging at 90×90×1500 μm. Results In the normal rat retinas, basal blood flow was 5.5ml/gram/min, significantly higher than those reported in the brain (∼1ml/gram/min). Hyperoxia decreased blood flow due to vasoconstriction and hypercapnia increased blood flow due to vasodilation in the normal retinas. In the RCS rat retinas, basal blood flow was diminished significantly (P<0.05). Interestingly, absolute hyperoxia- and hypercapnia-induced blood-flow changes in the RCS retinas were not statistically different from those in the normal retinas (P>0.05). However, percent changes in blood-flow were significantly larger than in normal retinas due to lower basal blood flow. Conclusion Retinal degeneration markedly reduces basal blood-flow but does not appear to impair vascular reactivity. These data also suggest caution when interpreting the relative stimulus-evoked functional MRI changes in diseased states where basal parameters are significantly perturbed. Quantitative blood-flow MRI may serve as a valuable tool to study the retina without depth limitation. PMID:18952917

  17. Cerebral blood flow tomography with xenon-133

    SciTech Connect

    Lassen, N.A.

    1985-10-01

    Cerebral blood flow (CBF) can be measured tomographically by inhalation of Xenon-/sup 133/. The calculation is based on taking a sequence of tomograms during the wash-in and wash-out phase of the tracer. Due to the dynamic nature of the process, a highly sensitive and fast moving single photon emission computed tomograph (SPECT) is required. Two brain-dedicated SPECT systems designed for this purpose are mentioned, and the method is described with special reference to the limitations inherent in the soft energy of the 133Xe primary photons. CBF tomography can be used for a multitude of clinical and investigative purposes. This article discusses in particular its use for the selection of patients with carotid occlusion for extracranial/intracranial bypass surgery, for detection of severe arterial spasm after aneurysm bleeding, and for detection of low flow areas during severe migraine attacks. The use of other tracers for CBF tomography using SPECT is summarized with emphasis on the /sup 99m/Tc chelates that freely pass the intact blood-brain barrier. The highly sensitive brain-dedicated SPECT systems described are a prerequisite for achieving high resolution tomograms with such tracers.

  18. Ozone Therapy on Cerebral Blood Flow: A Preliminary Report

    PubMed Central

    2004-01-01

    Ozone therapy is currently being used in the treatment of ischemic disorders, but the underlying mechanisms that result in successful treatment are not well known. This study assesses the effect of ozone therapy on the blood flow in the middle cerebral and common carotid arteries. Seven subjects were recruited for the therapy that was performed by transfusing ozone-enriched autologous blood on 3 alternate days over 1 week. Blood flow quantification in the common carotid artery (n = 14) was performed using color Doppler. Systolic and diastolic velocities in the middle cerebral artery (n = 14) were estimated using transcranial Doppler. Ultrasound assessments were conducted at the following three time points: 1) basal (before ozone therapy), 2) after session #3 and 3) 1 week after session #3. The common carotid blood flow had increased by 75% in relation to the baseline after session #3 (P < 0.001) and by 29% 1 week later (P = 0.039). In the middle cerebral artery, the systolic velocity had increased by 22% after session #3 (P = 0.001) and by 15% 1 week later (P = 0.035), whereas the diastolic velocity had increased by 33% after session #3 (P < 0.001) and by 18% 1 week later (P = 0.023). This preliminary Doppler study supports the clinical experience of achieving improvement by using ozone therapy in peripheral ischemic syndromes. Its potential use as a complementary treatment in cerebral low perfusion syndromes merits further clinical evaluation. PMID:15841265

  19. 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

  20. 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. PMID:25426330

  1. 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

  2. Improving cord blood transplantation in children.

    PubMed

    Locatelli, Franco

    2009-10-01

    Umbilical cord blood transplantation (UCBT) is widely used to treat children affected by many disorders. In comparison to bone marrow transplantation, the advantages of UCBT are represented by lower incidence and severity of graft-versus-host disease, easier procurement and prompter availability of cord blood cells, and by the possibility of using donors showing human leucocyte antigen disparities with the recipient. Despite these advantages, the large experience gained over the last decade has clearly demonstrated that UCBT patients may be exposed to an increased risk of early fatal complications, due to the lower engraftment rate of donor haematopoiesis, delayed kinetics of neutrophil recovery and lack of adoptive transfer of pathogen-specific memory T-cells. An inverse correlation between the number of nucleated cord blood cells infused per kilogramme recipient body weight and the risk of dying from transplantation-related causes exists. Thus, it is not surprising that strategies aimed at increasing the number of cord blood progenitors, favouring stem cell homing, and transferring pathogen-specific lymphocytes, have been recently investigated. In particular, selection of the richest cord blood units, infusion of 2 units in the same recipient, intrabone injection of cord blood cells, and transplantation of ex-vivo expanded progenitors can contribute to improve the results of UCBT. PMID:19796271

  3. Volumetric liquid flow measurement through thermography to simulate blood flow in an artery

    NASA Astrophysics Data System (ADS)

    Villaseñor-Mora, Carlos; Rabell-Montiel, Adela; González-Vega, Arturo; Gutierrez-Juarez, Gerardo

    2015-09-01

    Encouraged to improve the procedure to measure the blood flow in cases with peripheral artery disease using thermography, that allows to evaluate several arteries simultaneously, it was developed an alternative to measure the volumetric flow through a conduit, it was studied the variation of the thermal energy computed from thermal images due to changes in flow at different temperatures, and it was observed that the measurement is not strongly influenced by the emissivity of the conduit, the ambient temperature and humidity, but that is necessary to establish an adequate calibration of the camera to can use it as measurement instrument.

  4. Measurement of Retinal Blood Flow Using Fluorescently Labeled Red Blood Cells1,2,3

    PubMed Central

    Kornfield, Tess E.

    2015-01-01

    Abstract Blood flow is a useful indicator of the metabolic state of the retina. However, accurate measurement of retinal blood flow is difficult to achieve in practice. Most existing optical techniques used for measuring blood flow require complex assumptions and calculations. We describe here a simple and direct method for calculating absolute blood flow in vessels of all sizes in the rat retina. The method relies on ultrafast confocal line scans to track the passage of fluorescently labeled red blood cells (fRBCs). The accuracy of the blood flow measurements was verified by (1) comparing blood flow calculated independently using either flux or velocity combined with diameter measurements, (2) measuring total retinal blood flow in arterioles and venules, (3) measuring blood flow at vessel branch points, and (4) measuring changes in blood flow in response to hyperoxic and hypercapnic challenge. Confocal line scans oriented parallel and diagonal to vessels were used to compute fRBC velocity and to examine velocity profiles across the width of vessels. We demonstrate that these methods provide accurate measures of absolute blood flow and velocity in retinal vessels of all sizes. PMID:26082942

  5. Cerebral blood flow in normal pressure hydrocephalus

    SciTech Connect

    Mamo, H.L.; Meric, P.C.; Ponsin, J.C.; Rey, A.C.; Luft, A.G.; Seylaz, J.A.

    1987-11-01

    A xenon-133 method was used to measure cerebral blood flow (CBF) before and after cerebrospinal fluid (CSF) removal in patients with normal pressure hydrocephalus (NPH). Preliminary results suggested that shunting should be performed on patients whose CBF increased after CSF removal. There was a significant increase in CBF in patients with NPH, which was confirmed by the favorable outcome of 88% of patients shunted. The majority of patients with senile and presenile dementia showed a decrease or no change in CBF after CSF removal. It is suggested that although changes in CBF and clinical symptoms of NPH may have the same cause, i.e., changes in the cerebral intraparenchymal pressure, there is no simple direct relation between these two events. The mechanism underlying the loss of autoregulation observed in NPH is also discussed.

  6. Intraoperative cerebral blood flow imaging of rodents

    NASA Astrophysics Data System (ADS)

    Li, Hangdao; Li, Yao; Yuan, Lu; Wu, Caihong; Lu, Hongyang; Tong, Shanbao

    2014-09-01

    Intraoperative monitoring of cerebral blood flow (CBF) is of interest to neuroscience researchers, which offers the assessment of hemodynamic responses throughout the process of neurosurgery and provides an early biomarker for surgical guidance. However, intraoperative CBF imaging has been challenging due to animal's motion and position change during the surgery. In this paper, we presented a design of an operation bench integrated with laser speckle contrast imager which enables monitoring of the CBF intraoperatively. With a specially designed stereotaxic frame and imager, we were able to monitor the CBF changes in both hemispheres during the rodent surgery. The rotatable design of the operation plate and implementation of online image registration allow the technician to move the animal without disturbing the CBF imaging during surgery. The performance of the system was tested by middle cerebral artery occlusion model of rats.

  7. Cerebral blood flow variations in CNS lupus

    SciTech Connect

    Kushner, M.J.; Tobin, M.; Fazekas, F.; Chawluk, J.; Jamieson, D.; Freundlich, B.; Grenell, S.; Freemen, L.; Reivich, M. )

    1990-01-01

    We studied the patterns of cerebral blood flow (CBF), over time, in patients with systemic lupus erythematosus and varying neurologic manifestations including headache, stroke, psychosis, and encephalopathy. For 20 paired xenon-133 CBF measurements, CBF was normal during CNS remissions, regardless of the symptoms. CBF was significantly depressed during CNS exacerbations. The magnitude of change in CBF varied with the neurologic syndrome. CBF was least affected in patients with nonspecific symptoms such as headache or malaise, whereas patients with encephalopathy or psychosis exhibited the greatest reductions in CBF. In 1 patient with affective psychosis, without clinical or CT evidence of cerebral ischemia, serial SPECT studies showed resolution of multifocal cerebral perfusion defects which paralleled clinical recovery.

  8. Topical menthol increases cutaneous blood flow.

    PubMed

    Craighead, Daniel H; Alexander, Lacy M

    2016-09-01

    Menthol, the active ingredient in several topically applied analgesics, activates transient receptor potential melastatin 8 (TRPM8) receptors on sensory nerves and on the vasculature inducing a cooling sensation on the skin. Ilex paraguariensis is also a common ingredient in topical analgesics that has potential vasoactive properties and may alter the mechanisms of action of menthol. We sought to characterize the microvascular effects of topical menthol and ilex application and to determine the mechanism(s) through which these compounds may independently and combined alter cutaneous blood flow. We hypothesized that menthol would induce vasoconstriction and that ilex would not alter skin blood flow (SkBF). Three separate protocols were conducted to examine menthol and ilex-mediated changes in SkBF. In protocol 1, placebo, 4% menthol, 0.7% ilex, and combination menthol+ilex gels were applied separately to the skin and red cell flux was continuously measured utilizing laser speckle contrast imaging (LSCI). In protocol 2, seven concentrations of menthol gel (0.04%, 0.4%, 1%, 2%, 4%, 7%, 8%) were applied to the skin to model the dose-response curve. In protocol 3, placebo, menthol, ilex, and menthol+ilex gels were applied to skin under local thermal control (34°C) both with and without sensory nerve blockage (topical lidocaine 4%). Post-occlusive reactive hyperemia (PORH) and local heating (42°C) protocols were conducted to determine the relative contribution of endothelium derived hyperpolarizing factors (EDHFs)/sensory nerves and nitric oxide (NO), respectively. Red cell flux was normalized to mean arterial pressure expressed as cutaneous vascular conductance (CVC: flux·mmHg(-1)) in all protocols. Topical menthol application increased SkBF compared to placebo (3.41±0.33 vs 1.1±0.19CVC: p<0.001). During the dose-response, SkBF increased with increasing doses of menthol (main effect, p<0.05) with an ED50 of 1.0%. Similarly, SkBF was increased after menthol

  9. Mapping blood flow directionality in the human brain.

    PubMed

    Park, Sung-Hong; Do, Won-Joon; Choi, Seung Hong; Zhao, Tiejun; Bae, Kyongtae Ty

    2016-07-01

    Diffusion properties of tissue are often expressed on the basis of directional variance, i.e., diffusion tensor imaging. In comparison, common perfusion-weighted imaging such as arterial spin labeling yields perfusion in a scalar quantity. The purpose of this study was to test the feasibility of mapping cerebral blood flow directionality using alternate ascending/descending directional navigation (ALADDIN), a recently-developed arterial spin labeling technique with sensitivity to blood flow directions. ALADDIN was applied along 3 orthogonal directions to assess directional blood flow in a vector form and also along 6 equally-spaced directions to extract blood flow tensor matrix (P) based on a blood flow ellipsoid model. Tensor elements (eigenvalues, eigenvectors, etc) were calculated to investigate characteristics of the blood flow tensor, in comparison with time-of-flight MR angiogram. While the directions of the main eigenvectors were heterogeneous throughout the brain, regional clusters of blood flow directionality were reproducible across subjects. The technique could show heterogeneous blood flow directionality within and around brain tumor, which was different from that of the contralateral normal side. The proposed method is deemed to provide information of blood flow directionality, which has not been demonstrated before. The results warrant further studies to assess changes in the directionality map as a function of scan parameters, to understand the signal sources, to investigate the possibility of mapping local blood perfusion directionality, and to evaluate its usefulness for clinical diagnosis. PMID:26968145

  10. Pulp blood flow assessment in human teeth by laser Doppler flowmetry

    NASA Astrophysics Data System (ADS)

    Pettersson, Hans; Oberg, P. Ake

    1991-05-01

    A laser Doppler instrument has been designed for blood flow measurements in the human pulp. By using infrared laser light from a laser diode the penetration into the tooth is considerably improved in comparison with earlier He-Ne measurements. A hand-held, pen-shaped probe facilitates the clinical use of the instrument. Restricted blood flow conditions in trauma patients, as well as the heart-rate synchronous pulsating nature of pulp blood in normal subjects, have been investigated.

  11. Quantitative Estimation of Tissue Blood Flow Rate.

    PubMed

    Tozer, Gillian M; Prise, Vivien E; Cunningham, Vincent J

    2016-01-01

    The rate of blood flow through a tissue (F) is a critical parameter for assessing the functional efficiency of a blood vessel network following angiogenesis. This chapter aims to provide the principles behind the estimation of F, how F relates to other commonly used measures of tissue perfusion, and a practical approach for estimating F in laboratory animals, using small readily diffusible and metabolically inert radio-tracers. The methods described require relatively nonspecialized equipment. However, the analytical descriptions apply equally to complementary techniques involving more sophisticated noninvasive imaging.Two techniques are described for the quantitative estimation of F based on measuring the rate of tissue uptake following intravenous administration of radioactive iodo-antipyrine (or other suitable tracer). The Tissue Equilibration Technique is the classical approach and the Indicator Fractionation Technique, which is simpler to perform, is a practical alternative in many cases. The experimental procedures and analytical methods for both techniques are given, as well as guidelines for choosing the most appropriate method. PMID:27172960

  12. Blood flow in microvascular networks: A study in nonlinear biology

    PubMed Central

    Geddes, John B.; Carr, Russell T.; Wu, Fan; Lao, Yingyi; Maher, Meaghan

    2010-01-01

    Plasma skimming and the Fahraeus–Lindqvist effect are well-known phenomena in blood rheology. By combining these peculiarities of blood flow in the microcirculation with simple topological models of microvascular networks, we have uncovered interesting nonlinear behavior regarding blood flow in networks. Nonlinearity manifests itself in the existence of multiple steady states. This is due to the nonlinear dependence of viscosity on blood cell concentration. Nonlinearity also appears in the form of spontaneous oscillations in limit cycles. These limit cycles arise from the fact that the physics of blood flow can be modeled in terms of state dependent delay equations with multiple interacting delay times. In this paper we extend our previous work on blood flow in a simple two node network and begin to explore how topological complexity influences the dynamics of network blood flow. In addition we present initial evidence that the nonlinear phenomena predicted by our model are observed experimentally. PMID:21198135

  13. 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.

  14. Transport of platelets in flowing blood.

    PubMed

    Eckstein, E C; Bilsker, D L; Waters, C M; Kippenhan, J S; Tilles, A W

    1987-01-01

    Distribution and transport of platelets in flowing blood were studied experimentally using suspensions of washed red cells and fluorescent latex beads as platelet analogues. Distributions of the platelet analogues were obtained from stroboscopic epifluorescence photomicrographs of flow in 50-micron channels and from images of the cut cross sections of cryogenically frozen thin-walled 200-micron tubes. Concentration profiles of platelet analogues had a substantial near-wall excess for situations with a substantial hematocrit (greater than 10%) and a substantial wall shear rate (greater than 400 s-1). The viscosity of the suspending fluid was found to affect the size of the near-wall excess and its shear-dependent onset. Additionally, the shear-rate dependence of the near-wall excess did not occur with suspensions of hardened red cells. The excess extended a substantial distance from the wall in the 200-micron tubes and a portion of the profile could be fitted to an exponential curve. The random walk model that is used to describe enhanced platelet diffusion is envisioned as a walk (lateral platelet motion) caused by shear-induced collisions with red cells. A more comprehensive random walk model that includes biased collisions produces an effective lateral motion of convective nature in addition to a diffusional motion; it is used to explain the observed nonuniform distributions of platelet analogues. PMID:3439741

  15. Noninvasive method of estimating human newborn regional cerebral blood flow

    SciTech Connect

    Younkin, D.P.; Reivich, M.; Jaggi, J.; Obrist, W.; Delivoria-Papadopoulos, M.

    1982-12-01

    A noninvasive method of estimating regional cerebral blood flow (rCBF) in premature and full-term babies has been developed. Based on a modification of the /sup 133/Xe inhalation rCBF technique, this method uses eight extracranial NaI scintillation detectors and an i.v. bolus injection of /sup 133/Xe (approximately 0.5 mCi/kg). Arterial xenon concentration was estimated with an external chest detector. Cerebral blood flow was measured in 15 healthy, neurologically normal premature infants. Using Obrist's method of two-compartment analysis, normal values were calculated for flow in both compartments, relative weight and fractional flow in the first compartment (gray matter), initial slope of gray matter blood flow, mean cerebral blood flow, and initial slope index of mean cerebral blood flow. The application of this technique to newborns, its relative advantages, and its potential uses are discussed.

  16. Bone blood flow after spinal paralysis in the rat

    SciTech Connect

    Takahashi, H.; Yamamuro, T.; Okumura, H.; Kasai, R.; Tada, K. )

    1990-05-01

    The goal of this study was to investigate the acute and chronic effects of paralysis induced by spinal cord section or sciatic neurotomy on bone blood flow in the rat. Regional bone blood flow was measured in the early stage with the hydrogen washout technique and the change of whole bone blood flow was measured in the early and the late stages with the radioactive microsphere technique. Four to 6 h after cordotomy at the level of the 13th thoracic vertebra, the regional bone blood flow in the denervated tibia increased significantly (p less than 0.01). After hemicordotomy with rhizotomy at the same level, the regional bone blood flow in the denervated tibia increased significantly (p less than 0.05) 6 h postoperatively. The whole bone blood flow in the denervated tibia had also increased significantly (p less than 0.05) at 6 h and at 4 and 12 weeks postoperatively. After sciatic neurotomy, the regional and the whole bone blood flow in the paralytic tibia did not change significantly. The present study demonstrated that monoplegic paralysis caused an increase in bone blood flow in the denervated hind limb from a very early stage. It was suggested that the spinal nervous system contributed to the control of bone blood flow.

  17. A Discussion on the Regulation of Blood Flow and Pressure.

    PubMed

    Wolff, Christopher B; Collier, David J; Shah, Mussadiq; Saxena, Manish; Brier, Timothy J; Kapil, Vikas; Green, David; Lobo, Melvin

    2016-01-01

    This paper discusses two kinds of regulation essential to the circulatory system: namely the regulation of blood flow and that of (systemic) arterial blood pressure. It is pointed out that blood flow requirements sub-serve the nutritional needs of the tissues, adequately catered for by keeping blood flow sufficient for the individual oxygen needs. Individual tissue oxygen requirements vary between tissue types, while highly specific for a given individual tissue. Hence, blood flows are distributed between multiple tissues, each with a specific optimum relationship between the rate of oxygen delivery (DO2) and oxygen consumption (VO2). Previous work has illustrated that the individual tissue blood flows are adjusted proportionately, where there are variations in metabolic rate and where arterial oxygen content (CaO2) varies. While arterial blood pressure is essential for the provision of a sufficient pressure gradient to drive blood flow, it is applicable throughout the arterial system at any one time. Furthermore, It is regulated independently of the input resistance to individual tissues (local arterioles), since they are regulated locally, that being the means by which the highly specific adequate local requirement for DO2 is ensured. Since total blood flow is the summation of all the individually regulated tissue blood flows cardiac inflow (venous return) amounts to total tissue blood flow and as the heart puts out what it receives cardiac output is therefore determined at the tissues. Hence, regulation of arterial blood pressure is independent of the distributed independent regulation of individual tissues. It is proposed here that mechanical features of arterial blood pressure regulation will depend rather on the balance between blood volume and venous wall tension, determinants of venous pressure. The potential for this explanation is treated in some detail. PMID:26782204

  18. Prediction of Anomalous Blood Viscosity in Confined Shear Flow

    NASA Astrophysics Data System (ADS)

    Thiébaud, Marine; Shen, Zaiyi; Harting, Jens; Misbah, Chaouqi

    2014-06-01

    Red blood cells play a major role in body metabolism by supplying oxygen from the microvasculature to different organs and tissues. Understanding blood flow properties in microcirculation is an essential step towards elucidating fundamental and practical issues. Numerical simulations of a blood model under a confined linear shear flow reveal that confinement markedly modifies the properties of blood flow. A nontrivial spatiotemporal organization of blood elements is shown to trigger hitherto unrevealed flow properties regarding the viscosity η, namely ample oscillations of its normalized value [η]=(η-η0)/(η0ϕ) as a function of hematocrit ϕ (η0=solvent viscosity). A scaling law for the viscosity as a function of hematocrit and confinement is proposed. This finding can contribute to the conception of new strategies to efficiently detect blood disorders, via in vitro diagnosis based on confined blood rheology. It also constitutes a contribution for a fundamental understanding of rheology of confined complex fluids.

  19. Blood flow distribution in submerged and surface-swimming ducks.

    PubMed

    Stephenson, R; Jones, D R

    1992-05-01

    Observations that the response of the avian heart rate to submergence varies under different circumstances have led to speculation about variability of blood flow distribution during voluntary dives. We used a radiological imaging technique to examine the patterns of circulating blood flow in captive redhead ducks (Aythya americana) during rest, swimming, escape dives, forced dives and trapped escape dives and have shown that blood flow distribution in escape dives was the same as that in ducks swimming at the water surface. The response during trapped escape dives, however, was highly variable. Blood pressure was unchanged from the resting value during all activities. Predictions made about blood flow distribution during unrestrained dives on the basis of heart rate and other indirect data were confirmed in this study. However, the trapped escape dive responses indicated that heart rate alone is not always a reliable indicator of tissue blood flow in exercising ducks. PMID:1602277

  20. Quantification of Blood Flow and Topology in Developing Vascular Networks

    PubMed Central

    Kloosterman, Astrid; Hierck, Beerend; Westerweel, Jerry; Poelma, Christian

    2014-01-01

    Since fluid dynamics plays a critical role in vascular remodeling, quantification of the hemodynamics is crucial to gain more insight into this complex process. Better understanding of vascular development can improve prediction of the process, and may eventually even be used to influence the vascular structure. In this study, a methodology to quantify hemodynamics and network structure of developing vascular networks is described. The hemodynamic parameters and topology are derived from detailed local blood flow velocities, obtained by in vivo micro-PIV measurements. The use of such detailed flow measurements is shown to be essential, as blood vessels with a similar diameter can have a large variation in flow rate. Measurements are performed in the yolk sacs of seven chicken embryos at two developmental stages between HH 13+ and 17+. A large range of flow velocities (1 µm/s to 1 mm/s) is measured in blood vessels with diameters in the range of 25–500 µm. The quality of the data sets is investigated by verifying the flow balances in the branching points. This shows that the quality of the data sets of the seven embryos is comparable for all stages observed, and the data is suitable for further analysis with known accuracy. When comparing two subsequently characterized networks of the same embryo, vascular remodeling is observed in all seven networks. However, the character of remodeling in the seven embryos differs and can be non-intuitive, which confirms the necessity of quantification. To illustrate the potential of the data, we present a preliminary quantitative study of key network topology parameters and we compare these with theoretical design rules. PMID:24823933

  1. 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.

  2. Blood flow augmentation by intrinsic venular contraction in vivo.

    PubMed

    Dongaonkar, Ranjeet M; Quick, Christopher M; Vo, Jonathan C; Meisner, Joshua K; Laine, Glen A; Davis, Michael J; Stewart, Randolph H

    2012-06-15

    Venomotion, spontaneous cyclic contractions of venules, was first observed in the bat wing 160 years ago. Of all the functional roles proposed since then, propulsion of blood by venomotion remains the most controversial. Common animal models that require anesthesia and surgery have failed to provide evidence for venular pumping of blood. To determine whether venomotion actively pumps blood in a minimally invasive, unanesthetized animal model, we reintroduced the batwing model. We evaluated the temporal and functional relationship between the venous contraction cycle and blood flow and luminal pressure. Furthermore, we determined the effect of inhibiting venomotion on blood flow. We found that the active venous contractions produced an increase in the blood flow and exhibited temporal vessel diameter-blood velocity and pressure relationships characteristic of a peristaltic pump. The presence of valves, a characteristic of reciprocating pumps, enhances the efficiency of the venular peristaltic pump by preventing retrograde flow. Instead of increasing blood flow by decreasing passive resistance, venular dilation with locally applied sodium nitroprusside decreased blood flow. Taken together, these observations provide evidence for active venular pumping of blood. Although strong venomotion may be unique to bats, venomotion has also been inferred from venous pressure oscillations in other animal models. The conventional paradigm of microvascular pressure and flow regulation assumes venules only act as passive resistors, a proposition that must be reevaluated in the presence of significant venomotion. PMID:22513742

  3. Measuring tissue blood flow using ultrasound modulated diffused light

    NASA Astrophysics Data System (ADS)

    Ron, A.; Racheli, N.; Breskin, I.; Metzger, Y.; Silman, Z.; Kamar, M.; Nini, A.; Shechter, R.; Balberg, M.

    2012-02-01

    We demonstrate the ability of a novel device employing ultrasound modulation of near infrared light (referred as "Ultrasound tagged light" or UTL) to perform non-invasive monitoring of blood flow in the microvascular level in tissue. Monitoring microcirculatory blood flow is critical in clinical situations affecting flow to different organs, such as the brain or the limbs. . However, currently there are no non-invasive devices that measure microcirculatory blood flow in deep tissue continuously. Our prototype device (Ornim Medical, Israel) was used to monitor tissue blood flow on anesthetized swine during controlled manipulations of increased and decreased blood flow. Measurements were done on the calf muscle and forehead of the animal and compared with Laser Doppler (LD). ROC analysis of the sensitivity and specificity for detecting an increase in blood flow on the calf muscle, demonstrated AUC = 0.951 for 23 systemic manipulations of cardiac output by Epinephrine injection, which is comparable to AUC = 0.943 using laser Doppler. Some examples of cerebral blood flow monitoring are presented, along with their individual ROC curves. UTL flowmetry is shown to be effective in detecting changes in cerebral and muscle blood flow in swine, and has merit in clinical applications.

  4. Regional blood flow during cardiopulmonary resuscitation in dogs.

    PubMed

    Luce, J M; Rizk, N A; Niskanen, R A

    1984-10-01

    We studied regional blood flow (QR) using radiolabeled microspheres in 12 anesthetized dogs during cardiopulmonary resuscitation (CPR). A circumferential vest and abdominal binder were used with a mechanical ventilator to deliver 30 simultaneous chest compressions and ventilations per minute. When this device was modified to increase aortic pressure (Pao) during compression and the aortic-to-right atrial pressure gradient (Pao-Pra) during relaxation, cerebral and myocardial QR increased significantly. These findings suggest that QR during CPR can be improved by augmenting perfusion-pressure gradients across the cerebral and coronary circulations. PMID:6488828

  5. The use of vasoconstrictors to improve the tumor to non-tumor blood flow ratio (T/NT) in intraarterial chemotherapy (IAC) of head and neck cancer (H and N CA)

    SciTech Connect

    Ziessman, H.A.; Forastiere, A.A.; Wheeler, R.H.; Wahl, R.L.; Ackerman, R.J.; Juni, J.E.

    1984-01-01

    IAC of H and N CA can result in increased drug concentration to the tumor with decreased systemic toxicity. However, the reported response rate has not been significantly improved from conventional IV chemotherapy. Tumor vessels lack the smooth muscle of precapillary arterioles, therefore vasoconstrictors have the potential of shunting blood from normal tissue to tumor, improving the T/NT. The purpose of this study is to evaluate the effect of vasoconstrictors on regional blood flow, systemic shunting and the T/NT. In 5 studies, patients received increasing doses of norepiniphrine (NE) ranging from 0.1 to 15 gm/ml/min. IA TcMAA was infused prior to NE and after each NE infusion. Static images were acquired on computer, ROI's flagged for tumor and selected normal tissue. Images were obtained for each dose of NE using subtraction techniques. In all pts the perfusion pattern changed with increasing doses of NE. In 2 pts with significantly improved T/NT ratios, SPECT was performed with and without NE. Quantitation was done by drawing ROIs for tumor in each reconstructed transaxial slice. The T/NT ratio was calculated after summing all slices through the H and N with and without NE. In 1 pt the T/NT increased by 35% and the % A-V shunting to the lungs decreased from 31% to 26%. The other pt had a definite change in perfusion pattern but inconsistent with the planar study. This work in progress study suggests that infusion of vasoconstrictors may be useful in improving the T/NT but TcMAA perfusion studies are necessary to help determine the appropriate dosage. SPECT can help quantitate the change.

  6. Computational flow study of the continuous flow ventricular assist device, prototype number 3 blood pump.

    PubMed

    Anderson, J B; Wood, H G; Allaire, P E; Bearnson, G; Khanwilkar, P

    2000-05-01

    A computational fluid dynamics study of blood flow in the continuous flow ventricular assist device, Prototype No. 3 (CFVAD3), which consists of a 4 blade shrouded impeller fully supported in magnetic bearings, was performed. This study focused on the regions within the pump where return flow occurs to the pump inlet, and where potentially damaging shear stresses and flow stagnation might occur: the impeller blade passages and the narrow gap clearance regions between the impeller-rotor and pump housing. Two separate geometry models define the spacing between the pump housing and the impeller's hub and shroud, and a third geometry model defines the pump's impeller and curved blades. The flow fields in these regions were calculated for various operating conditions of the pump. Pump performance curves were calculated, which compare well with experimentally obtained data. For all pump operating conditions, the flow rates within the gap regions were predicted to be toward the inlet of the pump, thus recirculating a portion of the impeller flow. Two smaller gap clearance regions were numerically examined to reduce the recirculation and to improve pump efficiency. The computational and geometry models will be used in future studies of a smaller pump to determine increased pump efficiency and the risk of hemolysis due to shear stress, and to insure the washing of blood through the clearance regions to prevent thrombosis. PMID:10848679

  7. Design and optimization of a widely tunable semiconductor laser for blood oxygenation and blood flow measurements

    NASA Astrophysics Data System (ADS)

    Feng, Yafei; Deng, Haoyu; Song, Guangyi; He, Jian-Jun

    2014-11-01

    A method for measuring blood oxygenation and blood flow rate using a single widely tunable semiconductor laser is proposed and investigated. It is shown that a 700-nm-band tunable laser gives the highest sensitivity for blood oxygen measurement. The corresponding tunable laser is designed using the V-coupled cavity structure. The wavelength tuning range can reach 8 nm, which is sufficient for the blood oxygenation measurement in the 700-nm-band by using the Beer- Lambert law. In contrast to conventional blood oxygenation measurement method based on two LEDs, the laser can be used at the same time to measure the blood flow rate based on the Doppler principle.

  8. Blood flow-restricted exercise in space

    PubMed Central

    2012-01-01

    Prolonged exposure to microgravity results in chronic physiological adaptations including skeletal muscle atrophy, cardiovascular deconditioning, and bone demineralization. To attenuate the negative consequences of weightlessness during spaceflight missions, crewmembers perform moderate- to high-load resistance exercise in conjunction with aerobic (cycle and treadmill) exercise. Recent evidence from ground-based studies suggests that low-load blood flow-restricted (BFR) resistance exercise training can increase skeletal muscle size, strength, and endurance when performed in a variety of ambulatory populations. This training methodology couples a remarkably low exercise training load (approximately 20%–50% one repetition maximum (1RM)) with an inflated external cuff (width, ranging between approximately 30–90 mm; pressure, ranging between approximately 100–250 mmHg) that is placed around the exercising limb. BFR aerobic (walking and cycling) exercise training methods have also recently emerged in an attempt to enhance cardiovascular endurance and functional task performance while incorporating minimal exercise intensity. Although both forms of BFR exercise training have direct implications for individuals with sarcopenia and dynapenia, the application of BFR exercise training during exposure to microgravity to prevent deconditioning remains controversial. The aim of this review is to present an overview of BFR exercise training and discuss the potential usefulness of this method as an adjunct exercise countermeasure during prolonged spaceflight. The work will specifically emphasize ambulatory BFR exercise training adaptations, mechanisms, and safety and will provide directions for future research. PMID:23849078

  9. Synthetic Capillaries to Control Microscopic Blood Flow

    PubMed Central

    Sarveswaran, K.; Kurz, V.; Dong, Z.; Tanaka, T.; Penny, S.; Timp, G.

    2016-01-01

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using “live cell lithography”(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision—no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100–1000 cells, organized hierarchically to express a predictable function. PMID:26905751

  10. Synthetic Capillaries to Control Microscopic Blood Flow

    NASA Astrophysics Data System (ADS)

    Sarveswaran, K.; Kurz, V.; Dong, Z.; Tanaka, T.; Penny, S.; Timp, G.

    2016-02-01

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using “live cell lithography”(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision—no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100-1000 cells, organized hierarchically to express a predictable function.

  11. Synthetic Capillaries to Control Microscopic Blood Flow.

    PubMed

    Sarveswaran, K; Kurz, V; Dong, Z; Tanaka, T; Penny, S; Timp, G

    2016-01-01

    Capillaries pervade human physiology. The mean intercapillary distance is only about 100 μm in human tissue, which indicates the extent of nutrient diffusion. In engineered tissue the lack of capillaries, along with the associated perfusion, is problematic because it leads to hypoxic stress and necrosis. However, a capillary is not easy to engineer due to its complex cytoarchitecture. Here, it is shown that it is possible to create in vitro, in about 30 min, a tubular microenvironment with an elastic modulus and porosity consistent with human tissue that functionally mimicks a bona fide capillary using "live cell lithography"(LCL) to control the type and position of cells on a composite hydrogel scaffold. Furthermore, it is established that these constructs support the forces associated with blood flow, and produce nutrient gradients similar to those measured in vivo. With LCL, capillaries can be constructed with single cell precision-no other method for tissue engineering offers such precision. Since the time required for assembly scales with the number of cells, this method is likely to be adapted first to create minimal functional units of human tissue that constitute organs, consisting of a heterogeneous population of 100-1000 cells, organized hierarchically to express a predictable function. PMID:26905751

  12. Pulsatile blood flow in Abdominal Aortic Aneurysms

    NASA Astrophysics Data System (ADS)

    Salsac, Anne-Virginie; Lasheras, Juan C.; Singel, Soeren; Varga, Chris

    2001-11-01

    We discuss the results of combined in-vitro laboratory measurements and clinical observations aimed at determining the effect that the unsteady wall shear stresses and the pressure may have on the growth and eventual rupturing of an Abdominal Aortic Aneurysm (AAA), a permanent bulging-like dilatation occurring near the aortic bifurcation. In recent years, new non-invasive techniques, such as stenting, have been used to treat these AAAs. However, the development of these implants, aimed at stopping the growth of the aneurysm, has been hampered by the lack of understanding of the effect that the hemodynamic forces have on the growth mechanism. Since current in-vivo measuring techniques lack the precision and the necessary resolution, we have performed measurements of the pressure and shear stresses in laboratory models. The models of the AAA were obtained from high resolution three-dimensional CAT/SCANS performed in patients at early stages of the disease. Preliminary DPIV measurements show that the pulsatile blood flow discharging into the cavity of the aneurysm leads to large spikes of pressure and wall shear stresses near and around its distal end, indicating a possible correlation between the regions of high wall shear stresses and the observed location of the growth of the aneurysm.

  13. A mechanistic approach to blood flow occlusion.

    PubMed

    Loenneke, J P; Wilson, G J; Wilson, J M

    2010-01-01

    Low-Intensity occlusion training provides a unique beneficial training mode for promoting muscle hypertrophy. Training at intensities as low as 20% 1RM with moderate vascular occlusion results in muscle hypertrophy in as little as three weeks. The primary mechanisms by which occlusion training is thought to stimulate growth include, metabolic accumulation, which stimulates a subsequent increase in anabolic growth factors, fast-twitch fiber recruitment (FT), and increased protein synthesis through the mammalian target of rapamycin (mTOR) pathway. Heat shock proteins, Nitric oxide synthase-1 (NOS-1) and Myostatin have also been shown to be affected by an occlusion stimulus. In conclusion, low-intensity occlusion training appears to work through a variety of mechanisms. The research behind these mechanisms is incomplete thus far, and requires further examination, primarily to identify the actual metabolite responsible for the increase in GH with occlusion, and determine which mechanisms are associated to a greater degree with the hypertrophic/anti-catabolic changes seen with blood flow restriction. PMID:19885776

  14. Tissue Blood Flow During Remifentanil Infusion With Carbon Dioxide Loading.

    PubMed

    Kanbe, Hiroaki; Matsuura, Nobuyuki; Kasahara, Masataka; Ichinohe, Tatsuya

    2015-01-01

    The aim of this study was to investigate the effect of changes in end-tidal carbon dioxide tension (ETCO2) during remifentanil (Remi) infusion on oral tissue blood flow in rabbits. Eight male tracheotomized Japan White rabbits were anesthetized with sevoflurane under mechanical ventilation. The infusion rate of Remi was 0.4 μg/kg/min. Carbon dioxide was added to the inspired gas to change the inspired CO2 tension to prevent changes in the ventilating condition. Observed variables were systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), common carotid artery blood flow (CCBF), tongue mucosal blood flow (TBF), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), upper alveolar tissue blood flow (UBF), and lower alveolar tissue blood flow (LBF). The CCBF, TBF, BBF, UBF, and LBF values were increased, while MBF was decreased, under hypercapnia, and vice versa. The BBF, UBF, and LBF values were increased, while the MBF value was decreased, under hypercapnia during Remi infusion, and vice versa. The BBF, MBF, UBF, and LBF values, but not the CCBF and TBF values, changed along with ETCO2 changes during Remi infusion. PMID:26061573

  15. 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.

  16. Statistical variations of ultrasound signals backscattered from flowing blood.

    PubMed

    Huang, Chih-Chung; Wang, Shyh-Hau

    2007-12-01

    The statistical distributions of ultrasonic signals backscattered from blood have recently been used to characterize hemodynamic properties, such as red blood cell (RBC) aggregation and blood coagulation. However, a thorough understanding of the relationship between blood properties and the statistical behavior of signals backscattered from flowing blood is still lacking. This prompted us to use the statistical parameter to characterize signals backscattered from both whole blood and RBC suspensions at different flow velocities (from 10 to 60 cm/s) and hematocrits (from 20% to 50%) under a steady laminar flow condition. The Nakagami parameter, scaling parameter, backscatter amplitude profile and flow velocity profile across a flow tube were acquired using a 10 MHz focused ultrasonic transducer. The backscattered signal peaked approximately at the centerline of the flow tube due to the effects of RBC aggregation, with the peak value increasing as the flow velocity of whole blood decreased. The Nakagami parameter increased from 0.45 to 0.78 as the flow velocity increased from 10 to 60 cm/s. The probability density function (PDF) of signals backscattered from flowing whole blood conformed with a pre-Rayleigh distribution. The Nakagami parameter was close to 1 for signals backscattered from RBC suspensions at all the flow velocities and hematocrits tested, for which the PDF was Rayleigh distributed. These differences in the statistical distributions of backscattered signals between whole blood and RBC suspensions suggest that variations in the size of dynamic scatterers in the flow affect the shape of the backscattered signal envelope, which should be considered in future statistical models used to characterize blood properties. PMID:17673357

  17. Muscle metaboreflex and cerebral blood flow regulation in humans: implications for exercise with blood flow restriction.

    PubMed

    Prodel, Eliza; Balanos, George M; Braz, Igor D; Nobrega, Antonio C L; Vianna, Lauro C; Fisher, James P

    2016-05-01

    We investigated the effect of activating metabolically sensitive skeletal muscle afferents (muscle metaboreflex) on cerebral blood flow and the potentially confounding influence of concomitant changes in the partial pressure of arterial carbon dioxide. Eleven healthy males (25 ± 4 yr) performed submaximal leg cycling exercise on a semirecumbent cycle ergometer (heart rate: ∼120 beats/min), and assessments were made of the partial pressure of end-tidal carbon dioxide (PetCO2 ), internal carotid artery blood flow (ICAQ) and conductance (ICACVC), and middle cerebral artery mean blood velocity (MCAvm) and conductance index (MCACVCi).The muscle metaboreflex was activated during cycling with leg blood flow restriction (BFR) or isolated with postexercise ischemia (PEI). In separate trials, PetCO2 was either permitted to fluctuate spontaneously (control trial) or was clamped at 1 mmHg above resting levels (PetCO2 clamp trial). In the control trial, leg cycling with BFR decreased PetCO2 (Δ-4.8 ± 0.9 mmHg vs. leg cycling exercise) secondary to hyperventilation, while ICAQ, ICACVC, and MCAvm were unchanged and MCACVCi decreased. However, in the PetCO2 clamp trial, leg cycling with BFR increased both MCAvm (Δ5.9 ± 1.4 cm/s) and ICAQ (Δ20.0 ± 7.8 ml/min) and attenuated the decrease in MCACVCi, while ICACVC was unchanged. In the control trial, PEI decreased PetCO2 (Δ-7.0 ± 1.3 mmHg vs. rest), MCAvm and MCACVCi, whereas ICAQ and ICACVC were unchanged. In contrast, in the PetCO2 clamp trial both ICAQ (Δ18.5 ± 11.9 ml/min) and MCAvm (Δ8.8 ± 2.0 cm/s) were elevated, while ICACVC and MCACVCi were unchanged. In conclusion, when hyperventilation-related decreases in PetCO2 are prevented the activation of metabolically sensitive skeletal muscle afferent fibers increases cerebral blood flow. PMID:26873971

  18. Effects of Red Blood Cell Aggregation on the Apparent Viscosity of Blood Flow in Tubes.

    NASA Astrophysics Data System (ADS)

    Hitt, Darren L.; Lowe, Mary L.

    1996-11-01

    In arterioles and venules (20-200μ diameter), the low shear rates enable red blood cells to form aggregate structures of varying sizes and morphology. The size and distribution of the aggregates affect the flow impedance within a microvascular network; this effect may be characterized by an "apparent viscosity". In this study, we measure the apparent viscosity of blood flow in 50μ glass tubes as a function of shear rate and red blood cell volume fraction (hematocrit); for a fixed tube geometry and an imposed flow rate, the viscosity is determined by measuring the pressure drop across the tube. To correlate the apparent viscosity with the size and spatial distribution of the aggregates in the flow, video images of the flow are recorded and analyzed using power spectral techniques. Pig blood and sheep blood are used as the models for aggregating and non-aggregating blood, respectively. Supported by NSF PFF Award CTS-9253633

  19. Mammary blood flow regulation in the nursing rabbit

    SciTech Connect

    Katz, M.; Creasy, R.K.

    1984-11-01

    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 blood flow in the nursing rabbit.

  20. Regional cerebral blood flow changes associated with ethanol intoxication

    SciTech Connect

    Mathew, R.J.; Wilson, W.H.

    1986-11-01

    Regional cerebral blood flow (CBF) was measured via the 133Xenon inhalation technique in 26 healthy volunteers before and 60 minutes after the oral administration of ethyl alcohol or placebo on a double-blind basis. The cerebral blood flow values, corrected for test-retest differences in carbon dioxide showed a significant bilateral increase after ethanol administration. Blood levels of ethanol, estimated with a breath analyser, did not correlate with the CBF changes.

  1. Blood flow changes in arteriovenous malformation during behavioral activation.

    PubMed

    Deutsch, G

    1983-01-01

    Striking task-dependent fluctuations were observed in the cerebral blood flow pattern of a patient with a left posterior hemispheric arteriovenous malformation (AVM). Two-dimensional measures of regional cerebral flow in the resting state, using the xenon 133 inhalation technique, revealed a region of high flow coincident with the AVM seen on the patient's arteriograms. In subsequent studies, the AVM stood out as a region of high blood flow during a relaxed state, while it approached normal levels of flow when there was attentional demand. These observations suggest that focal regulatory mechanisms exist at the AVM or else that very substantial redistributions of blood flow are taking place which the flow rate in the AVM reflects only passively. Patients considered for embolic treatment of an AVM would benefit from an assessment of behavioral influences on flow in the AVM. PMID:6830163

  2. Measurement of microvesicle levels in human blood using flow cytometry.

    PubMed

    Chandler, Wayne L

    2016-07-01

    Microvesicles are fragments of cells released when the cells are activated, injured, or apoptotic. Analysis of microvesicle levels in blood has the potential to shed new light on the pathophysiology of many diseases. Flow cytometry is currently the only method that can simultaneously separate true lipid microvesicles from other microparticles in blood, determine the cell of origin and other microvesicle characteristics, and handle large numbers of clinical samples with a reasonable effort, but expanded use of flow cytometric measurement of microvesicle levels as a clinical and research tool requires improved, standardized assays. The goal of this review is to aid investigators in applying current best practices to microvesicle measurements. First pre-analytical factors are evaluated and data summarized for anticoagulant effects, sample transport and centrifugation. Next flow cytometer optimization is reviewed including interference from background in buffers and reagents, accurate microvesicle counting, swarm interference, and other types of coincidence errors, size calibration, and detection limits using light scattering, impedance and fluorescence. Finally current progress on method standardization is discussed and a summary of current best practices provided. © 2016 Clinical Cytometry Society. PMID:26606416

  3. Fluid dynamics aspects of miniaturized axial-flow blood pump.

    PubMed

    Kang, Can; Huang, Qifeng; Li, Yunxiao

    2014-01-01

    Rotary blood pump (RBP) is a kind of crucial ventricular assist device (VAD) and its advantages have been evidenced and acknowledged in recent years. Among the factors that influence the operation performance and the durability of various rotary blood pumps, medium property and the flow features in pump's flow passages are conceivably significant. The major concern in this paper is the fluid dynamics aspects of such a kind of miniaturized pump. More specifically, the structural features of axial-flow blood pump and corresponding flow features are analyzed in detail. The narrow flow passage between blade tips and pump casing and the rotor-stator interaction (RSI) zone may exert a negative effect on the shear stress distribution in the blood flow. Numerical techniques are briefly introduced in view of their contribution to facilitating the optimal design of blood pump and the visualization of shear stress distribution and multiphase flow analysis. Additionally, with the development of flow measurement techniques, the high-resolution, effective and non-intrusive flow measurement techniques catering to the measurement of the flows inside rotary blood pumps are highly anticipated. PMID:24211957

  4. Retinal blood flow measurement by using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Makita, Shuichi; Fabritius, Tapio; Miura, Masahiro; Yatagai, Toyohiko; Yasuno, Yoshiaki

    2008-02-01

    Quantification of the three-dimensional (3D) retinal vessel structure and blood flow is demonstrated. 3D blood flow distribution is obtained by Doppler optical coherence angiography (D-OCA). Vessel parameters, i.e. diameter, orientation, and position, are determined in an en face vessel image. The Doppler angle is estimated as the angle between the retinal vessel and the incident probing beam in representative cross-sectional flow image which extracted from the 3D flow distribution according to the vessel parameters. Blood flow velocity and volume rate can be quantified with these vessel parameters. The retinal blood flow velocity and volume rate are measured in the retinal vessels around the optic nerve head.

  5. Outflow Boundary Conditions for Blood Flow in Arterial Trees

    PubMed Central

    Du, Tao; Hu, Dan; Cai, David

    2015-01-01

    In the modeling of the pulse wave in the systemic arterial tree, it is necessary to truncate small arterial crowns representing the networks of small arteries and arterioles. Appropriate boundary conditions at the truncation points are required to represent wave reflection effects of the truncated arterial crowns. In this work, we provide a systematic method to extract parameters of the three-element Windkessel model from the impedance of a truncated arterial tree or from experimental measurements of the blood pressure and flow rate at the inlet of the truncated arterial crown. In addition, we propose an improved three-element Windkessel model with a complex capacitance to accurately capture the fundamental-frequency time lag of the reflection wave with respect to the incident wave. Through our numerical simulations of blood flow in a single artery and in a large arterial tree, together with the analysis of the modeling error of the pulse wave in large arteries, we show that both a small truncation radius and the complex capacitance in the improved Windkessel model play an important role in reducing the modeling error, defined as the difference in dynamics induced by the structured tree model and the Windkessel models. PMID:26000782

  6. Cerebral blood flow at high altitude.

    PubMed

    Ainslie, Philip N; Subudhi, Andrew W

    2014-06-01

    This brief review traces the last 50 years of research related to cerebral blood flow (CBF) in humans exposed to high altitude. The increase in CBF within the first 12 hours at high altitude and its return to near sea level values after 3-5 days of acclimatization was first documented with use of the Kety-Schmidt technique in 1964. The degree of change in CBF at high altitude is influenced by many variables, including arterial oxygen and carbon dioxide tensions, oxygen content, cerebral spinal fluid pH, and hematocrit, but can be collectively summarized in terms of the relative strengths of four key integrated reflexes: 1) hypoxic cerebral vasodilatation; 2) hypocapnic cerebral vasoconstriction; 3) hypoxic ventilatory response; and 4) hypercapnic ventilatory response. Understanding the mechanisms underlying these reflexes and their interactions with one another is critical to advance our understanding of global and regional CBF regulation. Whether high altitude populations exhibit cerebrovascular adaptations to chronic levels of hypoxia or if changes in CBF are related to the development of acute mountain sickness are currently unknown; yet overall, the integrated CBF response to high altitude appears to be sufficient to meet the brain's large and consistent demand for oxygen. This short review is organized as follows: An historical overview of the earliest CBF measurements collected at high altitude introduces a summary of reported CBF changes at altitude over the last 50 years in both lowlanders and high-altitude natives. The most tenable candidate mechanism(s) regulating CBF at altitude are summarized with a focus on available data in humans, and a role for these mechanisms in the pathophysiology of AMS is considered. Finally, suggestions for future directions are provided. PMID:24971767

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

    PubMed

    Javadzadegan, Ashkan; Simmons, Anne; Barber, Tracie

    2016-07-01

    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. PMID:26414530

  8. On the Role of the Blood Vessel Endothelial Microvilli in the Blood Flow in Small Capillaries

    PubMed Central

    Makarov, Vladimir; Zueva, Lidia; Sanabria, Priscila; Wessinger, William Dave; Golubeva, Tatiana; Khmelinskii, Igor; Inyushin, Mikhail

    2015-01-01

    Endothelial microvilli that protrude into the capillary lumen, although invisible in the optical microscopy, may play an important role in the blood flow control in the capillaries. Because of the plug effects, the width of the gap between the capillary wall and the blood cell is especially critical for the blood flow dynamics in capillaries, while microvilli located on the capillary wall can easily control the velocity of the blood flow. We report that microvilli in the capillaries of different vertebrate species have similar characteristics and density, suggesting similarities between the respective regulation mechanisms. A simplified physical model of the capillary effective diameter control by the microvilli is presented. PMID:26604921

  9. Carreau model for oscillatory blood flow in a tube

    NASA Astrophysics Data System (ADS)

    Tabakova, S.; Nikolova, E.; Radev, St.

    2014-11-01

    The analysis of the blood flow dynamics (hemodynamics) in tubes is crucial when investigating the rupture of different types of aneurysms. The blood viscosity nonlinear dependence on the flow shear rate creates complicated manifestations of the blood pulsations. Although a great number of studies exists, experimental and numerical, this phenomenon is still not very well understood. The aim of the present work is to propose a numerical model of the oscillatory blood flow in a tube on the basis of the Carreau model of the blood viscosity (nonlinear model with respect to the shear rate). The obtained results for the flow velocity and tangential stress on the tube wall are compared well with other authors' results.

  10. The importance of splenic blood flow in clearing pneumococcal organisms.

    PubMed Central

    Horton, J; Ogden, M E; Williams, S; Coln, D

    1982-01-01

    Overwhelming infection from encapsulated bacteria occurs after splenectomy. Decreases in IgM, tufsin, and serum opsonin are known to occur in animals and humans after splenectomy. A substantial immunologic advantage exists if some splenic tissue remains, but this may not offer sufficient protection from encapsulated bacteria if splenic arterial blood flow is reduced. This experiment was designed to examine the rate of pneumococcal clearance by the spleen and to determine the relationship between splenic blood flow and splenic tissue mass in bacterial clearance from the blood. Pneumococcal clearance, splenic blood flow, and residual splenic weight were measured in 171 rabbits with normal spleens, ligated splenic arteries, splenic autotransplants, hemisplenectomies, and splenectomies. Interruption of the splenic artery results in delayed pneumococcal clearance that is due to reduced blood flow and not to a decrease in splenic tissue mass. Splenic artery ligation to preserve an injured spleen cannot be assumed to give protection from sepsis. PMID:7055394

  11. Laser speckle technique for monitoring of blood and lymph flow

    NASA Astrophysics Data System (ADS)

    Fedosov, Ivan V.; Tuchin, Valery V.

    2004-07-01

    Laser speckle technique developed for monitoring of micro scale blood and lymph flows is described and discussed. It is based on the space-time correlation properties of dynamic speckle field formed by coherent light scattered by capillary flow of blood or lymph. As it was proved experimentally, the estimating of cross-correlation of speckle-field intensity fluctuations recorded in two different point allows for measurement of flow velocity and flow direction discrimination. Developed technique was applied for investigation of push-pull dynamics of lymph flow in rat mesentery. The results of experiments with models of bioflows and in vivo measurements are presented.

  12. Nasal mucosal blood flow after intranasal allergen challenge

    SciTech Connect

    Holmberg, K.; Bake, B.; Pipkorn, U.

    1988-03-01

    The nasal mucosal blood flow in patients with allergic rhinitis was determined at nasal allergen challenges with the /sup 133/Xenon washout method. Determinations were made in 12 subjects before and 15 minutes after challenge with diluent and increasing doses of allergen. The time course was followed in eight subjects by means of repeated measurements during 1 hour after a single allergen dose. Finally, the blood flow was measured after unilateral allergen challenge in the contralateral nasal cavity. A dose-dependent decrease in blood flow was found after nasal challenge with increasing doses of allergens, whereas challenge with diluent alone did not induce any changes. The highest allergen dose, which also induced pronounced nasal symptoms, resulted in a decrease in blood flow of 25% (p less than 0.001). The time-course study demonstrated a maximum decrease in blood flow 10 to 20 minutes after challenge and then a gradual return to baseline. Unilateral allergen challenge resulted in a decrease in blood flow in the contralateral, unchallenged nasal cavity, suggesting that part of the allergen-induced changes in blood flow were reflex mediated.

  13. Acute cocaine administration alters posttraumatic blood pressure and cerebral blood flow in rats.

    PubMed

    Muir, J K; Ellis, E F

    1995-01-01

    Cocaine abuse is widespread, and it is possible that its two main pharmacological actions, sympathomimetic and local anesthetic, could influence the blood pressure and cerebral blood flow response to brain injury, which occurs with increased frequency in drug abusers. We tested this hypothesis in ventilated barbiturate-anesthetized rats. Brain injury was induced using the fluid-percussion method, and cortical blood flow was measured using laser-Doppler flowmetry. Saline, cocaine, methamphetamine, or lidocaine was administered 10 min before injury. Upon injury, both cocaine- and saline-pretreated rats showed a similar acute hypertensive phase, which was followed by a period of more pronounced hypotension in the cocaine group (68 +/- 4 vs. 100 +/- 6 mmHg). Cortical blood flow increased dramatically 3-15 s following injury-induced hypertension in both the cocaine and saline groups (approximately 230-260%), but then fell below preinjury values within minutes. At 1 h postinjury, the blood flow in the saline group was 53 +/- 6% of the preinjury value, while in the cocaine group, flow was 74 +/- 7% of preinjury baseline. Similar to the cocaine-treated animals, methamphetamine also caused a more pronounced hypotensive event, but blood flow was not significantly different from saline controls. Lidocaine did not alter posttraumatic blood pressure but did significantly elevate blood flow throughout the 1-h postinjury period. At 60 min posttrauma, blood flow in the lidocaine group was 80 +/- 10% of the preinjury value. The mechanism by which cocaine alters blood pressure and blood flow after injury is not entirely certain.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7840303

  14. Effects of non Newtonian spiral blood flow through arterial stenosis

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Mahmudul; Maruf, Mahbub Alam; Ali, Mohammad

    2016-07-01

    The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system. A numerical investigation is carried out to analyze the effect of spiral blood flow through an axisymmetric three dimensional artery having 75% stenosis at the center. Blood is assumed as a Non-Newtonian fluid. Standard k-ω model is used for the simulation with the Reynolds number of 1000. A parabolic velocity profile with spiral flow is used as inlet boundary condition. The peak values of all velocity components are found just after stenosis. But total pressure gradually decreases at downstream. Spiral flow of blood has significant effects on tangential component of velocity. However, the effect is mild for radial and axial velocity components. The peak value of wall shear stress is at the stenosis zone and decreases rapidly in downstream. The effect of spiral flow is significant for turbulent kinetic energy. Detailed investigation and relevant pathological issues are delineated throughout the paper.

  15. Anharmonic analysis of arterial blood pressure and flow pulses.

    PubMed

    Voltairas, P A; Fotiadis, D I; Massalas, C V; Michalis, L K

    2005-07-01

    Fourier analysis is usually employed for the computation of blood flow in arteries. Although the orthogonality of Fourier eigenfunctions guarantees the accurate mathematical modeling of the blood pressure and flow waveforms, the physics behind this objective function is frequently missing. We propose a new method to account for the blood pressure and flow, single-cycle (systole-diastole) waveforms. It is based on the one dimensional hydrodynamic mass and momentum conservation equations for viscous flow. The similarity of the linear problem, under discussion, with related transmission line theory in electromagnetic wave propagation, permits expansion in anharmonic, non-separable eigenfunctions. In some cases one term in the expansion is adequate to fit the main peak of the observed waveforms. Analytical formulas are derived for the dependence of the pressure and flow main peaks on whole blood viscosity and distance from the heart, which interpret observations related to hypertension. PMID:15922753

  16. 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

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

    PubMed

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

    2015-03-01

    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

  18. Effect of swirling blood flow on vortex formation at post-stenosis.

    PubMed

    Ha, Hojin; Choi, Woorak; Park, Hanwook; Lee, Sang Joon

    2015-02-01

    Various clinical observations reported that swirling blood flow is a normal physiological flow pattern in various vasculatures. The swirling flow has beneficial effects on blood circulation through the blood vessels. It enhances oxygen transfer and reduces low-density lipoprotein concentration in the blood vessel by enhancing cross-plane mixing of the blood. However, the fluid-dynamic roles of the swirling flow are not yet fully understood. In this study, inhibition of material deposition at the post-stenosis region by the swirling flow was observed. To reveal the underlying fluid-dynamic characteristics, pathline flow visualization and time-resolved particle image velocimetry measurements were conducted. Results showed that the swirling inlet flow increased the development of vortices at near wall region of the post-stenosis, which can suppress further development of stenosis by enhancing transport and mixing of the blood flow. The fluid-dynamic characteristics obtained in this study would be useful for improving hemodynamic characteristics of vascular grafts and stents in which the stenosis frequently occurred. Moreover, the time-resolved particle image velocimetry measurement technique and vortex identification method employed in this study would be useful for investigating the fluid-dynamic effects of the swirling flow on various vascular environments. PMID:25767153

  19. 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.

  20. 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. PMID:24110631

  1. 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.

  2. A Porous Media Model for Blood Flow within Reticulated Foam

    PubMed Central

    Ortega, J.M.

    2013-01-01

    A porous media model is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10−8 to 10. This empirical model effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the model adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. PMID:24031095

  3. Abnormal Myocardial Blood Flow Reserve Observed in Cardiac Amyloidosis

    PubMed Central

    Nel, Karen; Senior, Roxy; Greaves, Kim

    2016-01-01

    We performed real-time myocardial contrast echocardiography on a patient with cardiac amyloidosis and previous normal coronary angiography presenting with atypical chest pain to assess myocardial blood flow reserve (MBFR). Myocardial contrast echocardiography was performed and flash microbubble destruction and replenishment analysis was used to calculate myocardial blood flow. Dipyridamole was used to achieve hyperemia. MBFR was derived from the ratio of peak myocardial blood flow at hyperemia and rest. The results show a marked reduction in MBFR in our patient. Previous reports of luminal obstruction of intramyocardial rather than epicardial vessels by amyloid deposition may be causing microvascular dysfunction. PMID:27081447

  4. Numerical Simulation of Cellular Blood Flow through a Rigid Artery

    NASA Astrophysics Data System (ADS)

    Reasor, Daniel; Clausen, Jonathan; Aidun, Cyrus

    2009-11-01

    In blood flow, red blood cells (RBCs), the most numerous constituent of blood, influence continuum-level measures by altering the suspension at microscopic scales. The presence of RBCs alters the stress and diffusion individual cells experience, which can influence cardiovascular diseases by affecting other cells present in blood like platelets and white blood cells. Simulations of blood at a cellular level provide a tool that allows exploration of both the rheology and the stress and diffusion of individual suspended cells. In this work, a hybrid lattice-Boltzmann/finite element method is used to simulate suspension flows characteristic of blood with deformable RBCs at realistic hematocrit values. We have shown the ability to simulate thousands deformable suspensions capturing non-Newtonian flow characteristics such as shear thinning, and the results agree well with experimental observations. Simulations through rigid arteries have been deformed with as many as 2500 RBCs. This work outlines results obtained for pressure-gradient driven blood flow through a rigid artery with 20%, 30%, 40%, and 50% hematocrit values. Results include the effect these deformable RBCs have on mean velocity, flow rate, radial variation of RBC concentration, and the effective viscosity for simulations at moderate to low cell capillary numbers, Ca <=0.08.

  5. Capillary pericytes regulate cerebral blood flow in health and disease

    PubMed Central

    Sutherland, Brad A.; O’Farrell, Fergus M.; Buchan, Alastair M.; Lauritzen, Martin; Attwell, David

    2014-01-01

    Brain blood flow increases, evoked by neuronal activity, power neural computation and are the basis of BOLD functional imaging. It is controversial whether blood flow is controlled solely by arteriole smooth muscle, or also by capillary pericytes. We demonstrate that neuronal activity and the neurotransmitter glutamate evoke the release of messengers that dilate capillaries by actively relaxing pericytes. Dilation is mediated by prostaglandin E2, but requires nitric oxide release to suppress vasoconstricting 20-HETE synthesis. In vivo, when sensory input increases blood flow, capillaries dilate before arterioles and are estimated to produce 84% of the blood flow increase. In pathology, ischaemia evokes capillary constriction by pericytes. We show that this is followed by pericyte death in rigor, which may irreversibly constrict capillaries and damage the blood-brain barrier. Thus, pericytes are major regulators of cerebral blood flow and initiators of functional imaging signals. Prevention of pericyte constriction and death may reduce the long-lasting blood flow decrease which damages neurons after stroke. PMID:24670647

  6. Blood flow estimation in gastroscopic true-color images

    NASA Astrophysics Data System (ADS)

    Jacoby, Raffael S.; Herpers, Rainer; Zwiebel, Franz M.; Englmeier, Karl-Hans

    1995-05-01

    The assessment of blood flow in the gastrointestinal mucosa might be an important factor for the diagnosis and treatment of several diseases such as ulcers, gastritis, colitis, or early cancer. The quantity of blood flow is roughly estimated by computing the spatial hemoglobin distribution in the mucosa. The presented method enables a practical realization by calculating approximately the hemoglobin concentration based on a spectrophotometric analysis of endoscopic true-color images, which are recorded during routine examinations. A system model based on the reflectance spectroscopic law of Kubelka-Munk is derived which enables an estimation of the hemoglobin concentration by means of the color values of the images. Additionally, a transformation of the color values is developed in order to improve the luminance independence. Applying this transformation and estimating the hemoglobin concentration for each pixel of interest, the hemoglobin distribution can be computed. The obtained results are mostly independent of luminance. An initial validation of the presented method is performed by a quantitative estimation of the reproducibility.

  7. Coronary blood flow in the anesthetized American alligator (Alligator mississippiensis).

    PubMed

    Jensen, Bjarke; Elfwing, Magnus; Elsey, Ruth M; Wang, Tobias; Crossley, Dane A

    2016-01-01

    Coronary circulation of the heart evolved early within ectothermic vertebrates and became of vital importance to cardiac performance in some teleost fish, mammals and birds. In contrast, the role and function of the coronary circulation in ectothermic reptiles remains largely unknown. Here, we investigated the systemic and coronary arterial responses of five anesthetized juvenile American alligators (Alligator mississippiensis) to hypoxia, acetylcholine, adenosine, sodium nitroprusside, isoproterenol, and phenylephrine. We recorded electrocardiograms, monitored systemic blood pressure, blood flows in both aortae, and blood flow in a major coronary artery supplying most of the right ventricle. Coronary arterial blood flow was generally forward, but there was a brief retrograde flow during a ventricular contraction. Blood pressure was significantly changed in all conditions. Acetylcholine decreased coronary forward flow, but this response was confounded by the concomitant lowered work of the ventricles due to decreased heart rate and blood pressure. Coronary forward flow was poorly correlated with heart rate and mean arterial pressure across treatments. Overall changes in coronary forward flow, significant and not significant, were generally in the same direction as mean arterial pressure and ventricular power, approximated as the product of systemic cardiac output and mean arterial pressure. PMID:26436857

  8. Relationship between beta-adrenoceptors and coronary blood flow heterogeneity

    SciTech Connect

    Upsher, M.E.; Weiss, H.R.

    1989-01-01

    The purpose of this study was to investigate the hypothesis that the heterogeneous distribution of ..beta.. adrenoceptors contributes to the control of flow heterogeneity in the canine myocardium. ..beta.. adrenoceptor density and affinity were measured simultaneously with coronary blood flow in multiple sections of the left ventricle of 14 anesthetized open chest dogs. Radioactive microspheres were used for the measurement of blood flow. Receptor density (Bmax) and dissociation constant (Kd) were measured using (/sup 125/I)- iodopindolol. The average control myocardial blood flow (MBF) was 86/+-/15 ml/min/100 g. Isoproterenol increased MBF by 82%, whereas propranolol reduced MBF by 13%. The mean value of Bmax was unaltered by either treatment. Under control conditions, a significant positive positive correlation was observed between Bmax and blood flow. In the isoproterenol treatment group, this correlation was enhanced. Beta adrenoceptor blockade led to a negative correlation. Kd showed no overall correlation with blood flow. Kd but not Bmax was significantly higher in the EPI than in the ENDO and in the base compared to the apex. There appears to be a direct linear relationship between the distribution of beta adrenoceptors and MBF distribution which is enhanced under conditions of high beta adrenergic activity. There is a correlation between beta adrenoceptor activity and blood flow distribution in the canine myocardium.

  9. Optic Nerve Head Blood Flow Autoregulation during Changes in Arterial Blood Pressure in Healthy Young Subjects

    PubMed Central

    Boltz, Agnes; Told, Reinhard; Napora, Katarzyna J.; Palkovits, Stefan; Werkmeister, René M.; Schmidl, Doreen; Popa-Cherecheanu, Alina; Garhöfer, Gerhard; Schmetterer, Leopold

    2013-01-01

    Aim In the present study the response of optic nerve head blood flow to an increase in ocular perfusion pressure during isometric exercise was studied. Based on our previous studies we hypothesized that subjects with an abnormal blood flow response, defined as a decrease in blood flow of more than 10% during or after isometric exercise, could be identified. Methods A total of 40 healthy subjects were included in this study. Three periods of isometric exercise were scheduled, each consisting of 2 minutes of handgripping. Optic nerve head blood flow was measured continuously before, during and after handgripping using laser Doppler flowmetry. Blood pressure was measured non-invasively in one-minute intervals. Intraocular pressure was measured at the beginning and the end of the measurements and ocular perfusion pressure was calculated as 2/3*mean arterial pressure –intraocular pressure. Results Isometric exercise was associated with an increase in ocular perfusion pressure during all handgripping periods (p < 0.001). By contrast no change in optic nerve head blood flow was seen. However, in a subgroup of three subjects blood flow showed a consistent decrease of more than 10% during isometric exercise although their blood pressure values increased. In addition, three other subjects showed a consistent decline of blood flow of more than 10% during the recovery periods. Conclusion Our data confirm previous results indicating that optic nerve head blood flow is autoregulated during an increase in perfusion pressure. In addition, we observed a subgroup of 6 subjects (15%) that showed an abnormal response, which is in keeping with our previous data. The mechanisms underlying this abnormal response remain to be shown. PMID:24324774

  10. Skeletal Blood Flow in Bone Repair and Maintenance

    PubMed Central

    Tomlinson, Ryan E.; Silva, Matthew J.

    2013-01-01

    Bone is a highly vascularized tissue, although this aspect of bone is often overlooked. In this article, the importance of blood flow in bone repair and regeneration will be reviewed. First, the skeletal vascular anatomy, with an emphasis on long bones, the distinct mechanisms for vascularizing bone tissue, and methods for remodeling existing vasculature are discussed. Next, techniques for quantifying bone blood flow are briefly summarized. Finally, the body of experimental work that demonstrates the role of bone blood flow in fracture healing, distraction osteogenesis, osteoporosis, disuse osteopenia, and bone grafting is examined. These results illustrate that adequate bone blood flow is an important clinical consideration, particularly during bone regeneration and in at-risk patient groups. PMID:26273509

  11. Aging, regional cerebral blood flow, and neuropsychological functioning

    SciTech Connect

    MacInnes, W.D.; Golden, C.J.; Gillen, R.W.; Sawicki, R.F.; Quaife, M.; Uhl, H.S.; Greenhouse, A.J.

    1984-10-01

    Previous studies found changes in regional cerebral blood flow (rCBF) patterns related to both age and various cognitive tasks. However, no study has yet demonstrated a relationship between rCBF and performance on the Luria-Nebraska Neuropsychological Battery (LNNB) in an elderly group. Seventy-nine elderly volunteers (56-88 years old), both healthy and demented, underwent the /sup 133/xenon inhalation rCBF procedure and were given the LNNB. The decrements in the gray-matter blood flow paralleled decrements in performance on the LNNB. Using partial correlations, a significant proportion of shared variance was observed between gray-matter blood flow and the LNNB scales. However, there was much less of a relationship between white-matter blood flow and performance on the LNNB. This study suggests that even within a restricted age sample rCBF is related in a global way to neuropsychological functioning.

  12. Regional blood flow during continuous low-dose endotoxin infusion

    SciTech Connect

    Fish, R.E.; Lang, C.H.; Spitzer, J.A.

    1986-01-01

    Escherichia coli endotoxin (ET) was administered to adult rats by continuous IV infusion from a subcutaneously implanted osmotic pump (Alzet). Cardiac output and regional blood flow were determined by the radiolabeled microsphere method after 6 and 30 hr of ET or saline infusion. Cardiac output (CO) of ET rats was not different from time-matched controls, whereas arterial pressure was 13% lower after 30 hr of infusion. After both 6 and 30 hr of ET, pancreatic blood flow and percentage of cardiac output were lower than in controls. Estimated portal venous flow was decreased at each time point, and an increased hepatic arterial flow (significant after 30 hr) resulted in an unchanged total hepatic blood flow. Blood flow to most other tissues, including epididymal fat, muscle, kidneys, adrenals, and gastrointestinal tract, was similar between treatments. Maintenance of blood flow to metabolically important tissues indicates that the previously reported alterations in in vitro cellular metabolism are not due to tissue hypoperfusion. Earlier observations of in vitro myocardial dysfunction, coexistent with the significant impairment in pancreatic flow, raise the possibility that release of a myocardial depressant factor occurs not only in profound shock but also under less severe conditions of sepsis and endotoxemia.

  13. APPLICATION OF THE THEORY OF INTERACTING CONTINUA TO BLOOD FLOW

    SciTech Connect

    Massoudi, Mehrdad; Kim, Jeongho; Hund, Samuel J.; Antaki, James F.

    2011-01-01

    Micro-scale investigations of the flow and deformation of blood and its formed elements have been studied for many years. Early in vitro investigations in the rotational viscometers or small glass tubes revealed important rheological properties such as the reduced blood apparent viscosity, Fahraeus effect and Fahraeus-Lindqvist effect [1], exhibiting the nonhomogeneous property of blood in microcirculation. We have applied Mixture Theory, also known as Theory of Interacting Continua, to study and model this property of blood [2, 3]. This approach holds great promise for predicting the trafficking of RBCs in micro-scale flows (such as the depletion layer near the wall), and other unique hemorheological phenomena relevant to blood trauma. The blood is assumed to be composed of an RBC component modeled as a nonlinear fluid, suspended in plasma, modeled as a linearly viscous fluid.

  14. Experimental comparison of mammalian and avian blood flow in microchannels

    NASA Astrophysics Data System (ADS)

    Fink, Kathryn; Liepmann, Dorian

    2015-11-01

    The non-Newtonian, shear rate dependent behavior of blood in microchannel fluid dynamics has been studied for nearly a century, with a significant focus on the characteristics of human blood. However, for over 200 years biologists have noted significant differences in red blood cell characteristics across vertebrate species, with particularly drastic differences in cell size and shape between mammals and non-mammalian classes. We present an experimental analysis of flow in long microchannels for several varieties of mammalian and avian blood, across a range of hematocrits, channel diameters, and flow rates. Correlation of shear rate and viscosity is compared to existing constitutive equations for human blood to further quantify the importance of red blood cell characteristics. Ongoing experimental results are made available in an online database for reference or collaboration. K.F. acknowledges funding from the ARCS Foundation and an NSF Graduate Research Fellowship through NSF Grant DGE 1106400.

  15. Microvascular blood flow resistance: Role of red blood cell migration and dispersion.

    PubMed

    Katanov, Dinar; Gompper, Gerhard; Fedosov, Dmitry A

    2015-05-01

    Microvascular blood flow resistance has a strong impact on cardiovascular function and tissue perfusion. The flow resistance in microcirculation is governed by flow behavior of blood through a complex network of vessels, where the distribution of red blood cells across vessel cross-sections may be significantly distorted at vessel bifurcations and junctions. In this paper, the development of blood flow and its resistance starting from a dispersed configuration of red blood cells is investigated in simulations for different hematocrit levels, flow rates, vessel diameters, and aggregation interactions between red blood cells. Initially dispersed red blood cells migrate toward the vessel center leading to the formation of a cell-free layer near the wall and to a decrease of the flow resistance. The development of cell-free layer appears to be nearly universal when scaled with a characteristic shear rate of the flow. The universality allows an estimation of the length of a vessel required for full flow development, lc ≲ 25D, for vessel diameters in the range 10 μm < D < 100 μm. Thus, the potential effect of red blood cell dispersion at vessel bifurcations and junctions on the flow resistance may be significant in vessels which are shorter or comparable to the length lc. Aggregation interactions between red blood cells generally lead to a reduction of blood flow resistance. The simulations are performed using the same viscosity for both external and internal fluids and the RBC membrane viscosity is not considered; however, we discuss how the viscosity contrast may affect the results. Finally, we develop a simple theoretical model which is able to describe the converged cell-free-layer thickness at steady-state flow with respect to flow rate. The model is based on the balance between a lift force on red blood cells due to cell-wall hydrodynamic interactions and shear-induced effective pressure due to cell-cell interactions in flow. We expect that these results can

  16. Effect of pulsatile swirling flow on stenosed arterial blood flow.

    PubMed

    Ha, Hojin; Lee, Sang Joon

    2014-09-01

    The existence of swirling flow phenomena is frequently observed in arterial vessels, but information on the fluid-dynamic roles of swirling flow is still lacking. In this study, the effects of pulsatile swirling inlet flows with various swirling intensities on the flow field in a stenosis model are experimentally investigated using a particle image velocimetry velocity field measurement technique. A pulsatile pump provides cyclic pulsating inlet flow and spiral inserts with two different helical pitches (10D and 10/3D) induce swirling flow in the stenosed channel. Results show that the pulsatile swirling flow has various beneficial effects by reducing the negative wall shear stress, the oscillatory shear index, and the flow reverse coefficient at the post-stenosis channel. Temporal variations of vorticity fields show that the short propagation length of the jet flow and the early breakout of turbulent flow are initiated as the swirling flow disturbs the symmetric development of the shear layer. In addition, the overall energy dissipation rate of the flow is suppressed by the swirling component of the flow. The results will be helpful for elucidating the hemodynamic characteristics of atherosclerosis and discovering better diagnostic procedures and clinical treatments. PMID:24984589

  17. Effect of tropicamide on ocular blood flow in the rabbit

    SciTech Connect

    Delgado, D.; Michel, P.; Jaanus, S.D.

    1982-05-01

    Intracardiac injection of 15 microspheres labeled with /sup 85/Sr (strontium) and /sup 141/Ce (cerium) were used to determine ocular blood flow in seven rabbits before and 25 min after bilateral application of tropicamide to the cornea. By using two different isotopes distinguishable under gammaspectrometry, each animal served as its own control. After administration of two drops of 1% tropicamide, no significant difference in blood flow between treated and untreated eyes was observed.

  18. Blood-flow measurement in muscle with Xe-133

    SciTech Connect

    Chung, S.Y.; Kim, I.; Ryo, U.Y.; Maskin, C.; Pinsky, S.

    1987-11-01

    An alternative method to the conventional miniature probe system for the measurement of blood flow in muscle has been developed. Xenon-133 was injected into the quadriceps muscles of ten subjects. A gamma camera and an online computer were then used to measure the half-clearance time of the Xe-133 while the subject was both at rest and exercising on an upright bicycle ergometer. The blood flow in the muscle was then calculated from the acquired data.

  19. 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.

  20. Radiohalogenated thienylethylamine derivatives for evaluating local cerebral blood flow

    SciTech Connect

    Goodman, M.M.; Knapp, F.F. Jr.

    1990-02-13

    This patent describes radiopharmaceuticals useful in brain imaging. They comprise 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.

  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. Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia.

    PubMed

    Coverdale, Nicole S; Gati, Joseph S; Opalevych, Oksana; Perrotta, Amanda; Shoemaker, J Kevin

    2014-11-15

    To establish the accuracy of transcranial Doppler ultrasound (TCD) measures of middle cerebral artery (MCA) cerebral blood flow velocity (CBFV) as a surrogate of cerebral blood flow (CBF) during hypercapnia (HC) and hypocapnia (HO), we examined whether the cross-sectional area (CSA) of the MCA changed during HC or HO and whether TCD-based estimates of CBFV were equivalent to estimates from phase contrast (PC) magnetic resonance imaging. MCA CSA was measured from 3T magnetic resonance images during baseline, HO (hyperventilation at 30 breaths/min), and HC (6% carbon dioxide). PC and TCD measures of CBFV were measured during these protocols on separate days. CSA and TCD CBFV were used to calculate CBF. During HC, CSA increased from 5.6 ± 0.8 to 6.5 ± 1.0 mm(2) (P < 0.001, n = 13), while end-tidal carbon dioxide partial pressure (PETCO2) increased from 37 ± 3 to 46 ± 5 Torr (P < 0.001). During HO, CSA decreased from 5.8 ± 0.9 to 5.3 ± 0.9 mm(2) (P < 0.001, n = 15), while PetCO2 decreased from 36 ± 4 to 23 ± 3 Torr (P < 0.001). CBFVs during baseline, HO, and HC were compared between PC and TCD, and the intraclass correlation coefficient was 0.83 (P < 0.001). The relative increase from baseline was 18 ± 8% greater (P < 0.001) for CBF than TCD CBFV during HC, and the relative decrease of CBF during HO was 7 ± 4% greater than the change in TCD CBFV (P < 0.001). These findings challenge the assumption that the CSA of the MCA does not change over modest changes in PETCO2. PMID:25012027

  3. 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.

  4. 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.

  5. 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. PMID:27335889

  6. Measuring bovine mammary gland blood flow using a transit time ultrasonic flow probe.

    PubMed

    Gorewit, R C; Aromando, M C; Bristol, D G

    1989-07-01

    Lactating cattle were used to validate a transit time ultrasonic blood flow metering system for measuring mammary gland arterial blood flow. Blood flow probes were surgically placed around the right external pudic artery. An electromagnetic flow probe was implanted in tandem with the ultrasonic probe in two cows for comparative measurements. The absolute accuracy of the implanted flow probes was assessed in vivo by mechanical means on anesthetized cows after 2 to 3 wk of implantation. The zero offset of the ultrasonic probes ranged from -12 to 8 ml/min. When the ultrasonic probe was properly implanted, the slopes of the calibration curves were linear and ranged from .92 to .95, tracking absolute flow to within 8%. The transit time instrument's performance was examined under a variety of physiological conditions. These included milking and hormone injections. The transit time ultrasonic flow meter accurately measured physiological changes in mammary arterial blood flow in chronically prepared conscious cattle. Blood flow increased 29% during milking. Epinephrine decreased mammary blood flow by 90 to 95%. Oxytocin doses increased mammary blood flow by 15 to 24%. PMID:2674232

  7. Cerebral aneurysms treated with flow-diverting stents: Computational models using intravascular blood flow measurements

    PubMed Central

    Levitt, Michael R; McGah, Patrick M; Aliseda, Alberto; Mourad, Pierre D; Nerva, John D; Vaidya, Sandeep S; Morton, Ryan P; Ghodke, Basavaraj V; Kim, Louis J

    2013-01-01

    Background and Purpose Computational fluid dynamics modeling is useful in the study of the hemodynamic environment of cerebral aneurysms, but patient-specific measurements of boundary conditions, such as blood flow velocity and pressure, have not been previously applied to the study of flow-diverting stents. We integrated patient-specific intravascular blood flow velocity and pressure measurements into computational models of aneurysms before and after treatment with flow-diverting stents to determine stent effects on aneurysm hemodynamics. Methods Blood flow velocity and pressure were measured in peri-aneurysmal locations using an intravascular dual-sensor pressure and Doppler velocity guidewire before and after flow-diverting stent treatment of four unruptured cerebral aneurysms. These measurements defined inflow and outflow boundary conditions for computational models. Intra-aneurysmal flow rates, wall shear stress and wall shear stress gradient were calculated. Results Measurements of inflow velocity and outflow pressure were successful in all four patients. Computational models incorporating these measurements demonstrated significant reductions in intra-aneurysmal wall shear stress and wall shear stress gradient, and a trend in reduced intra-aneurysmal blood flow. Conclusions Integration of intravascular dual-sensor guidewire measurements of blood flow velocity and blood pressure provided patient-specific computational models of cerebral aneurysms. Aneurysm treatment with flow-diverting stents reduces blood flow and hemodynamic shear stress in the aneurysm dome. PMID:23868162

  8. Measurement of normal portal venous blood flow by Doppler ultrasound.

    PubMed

    Brown, H S; Halliwell, M; Qamar, M; Read, A E; Evans, J M; Wells, P N

    1989-04-01

    The volume flow rate of blood in the portal vein was measured using a duplex ultrasound system. The many errors inherent in the duplex method were assessed with particular reference to the portal vein and appropriate correction factors were obtained by in vitro calibration. The effect of posture on flow was investigated by examining 45 healthy volunteers in three different positions; standing, supine and tilted head down at 20 degrees from the horizontal. The mean volume blood flow in the supine position was 864 (188)ml/min (mean 1SD). When standing, the mean volume blood flow was significantly reduced by 26% to 662 (169)ml/min. There was, however, no significant difference between flow when supine and when tilted head down at 20 degrees from the horizontal. PMID:2653973

  9. Blood flow and arterial endothelial dysfunction: Mechanisms and implications

    NASA Astrophysics Data System (ADS)

    Barakat, Abdul I.

    2013-06-01

    The arterial endothelium exquisitely regulates vascular function, and endothelial dysfunction plays a critical role in the development of atherosclerosis. Atherosclerotic lesions develop preferentially at arterial branches and bifurcations where the blood flow is disturbed. Understanding the basis for this observation requires elucidating the effects of blood flow on the endothelial cell (EC) function. The goal of this review is: (1) to describe our current understanding of the relationships between arterial blood flow and atherosclerosis, (2) to present the wide array of flow-induced biological responses in ECs, and (3) to discuss the mechanisms by which ECs sense, transmit, and transduce flow-derived mechanical forces. We conclude by presenting some future perspectives in the highly interdisciplinary field of EC mechanotransduction.

  10. Aerobic fitness is associated with greater hippocampal cerebral blood flow in children.

    PubMed

    Chaddock-Heyman, Laura; Erickson, Kirk I; Chappell, Michael A; Johnson, Curtis L; Kienzler, Caitlin; Knecht, Anya; Drollette, Eric S; Raine, Lauren B; Scudder, Mark R; Kao, Shih-Chun; Hillman, Charles H; Kramer, Arthur F

    2016-08-01

    The present study is the first to investigate whether cerebral blood flow in the hippocampus relates to aerobic fitness in children. In particular, we used arterial spin labeling (ASL) perfusion MRI to provide a quantitative measure of blood flow in the hippocampus in 73 7- to 9-year-old preadolescent children. Indeed, aerobic fitness was found to relate to greater perfusion in the hippocampus, independent of age, sex, and hippocampal volume. Such results suggest improved microcirculation and cerebral vasculature in preadolescent children with higher levels of aerobic fitness. Further, aerobic fitness may influence how the brain regulates its metabolic demands via blood flow in a region of the brain important for learning and memory. To add specificity to the relationship of fitness to the hippocampus, we demonstrate no significant association between aerobic fitness and cerebral blood flow in the brainstem. Our results reinforce the importance of aerobic fitness during a critical period of child development. PMID:27419884

  11. Validation studies for brain blood flow assessment by radioxenon tomography

    SciTech Connect

    Rezai, K.; Kirchner, P.T.; Armstrong, C.; Ehrhardt, J.C.; Heistad, D.

    1988-03-01

    A tomographic technique has been used recently for cerebral blood flow measurements with inhaled radioxenon. Based on experiments in a specially developed dynamic phantom and on studies in primates in vivo, we have analyzed the validity of this method for measurements of both regional and total blood flow in the brain. We have also examined the errors introduced into flow computations as a function of changes in such parameters as: rate of xenon input, size of region of interest, magnitude of regional flow rates, and inter-regional flow differences. Our findings indicate a reasonable degree of accuracy for flow measurements in gray matter regions that are 3 cm in diameter or larger, while white matter blood flow is generally overestimated. The accuracy for regional flow assessments degrades as a function of: diminishing region size, increasing inter-regional flow differences, and flow rates in excess of 100 ml/100 g/min. Measurements for brain regions 2 cm or smaller in diameter can be in error by 25-50% as a result of partial volume averaging. Although the technique is not ideal for accurate flow measurements in small regions of the brain, it nevertheless provides a convenient means of assessing perfusion in major vascular territories of the brain in routine clinical applications.

  12. Measurement of directed blood flow by laser speckle

    NASA Astrophysics Data System (ADS)

    Hirst, Evan R.; Thompson, Oliver B.; Andrews, Michael K.

    2011-03-01

    Recent success in reconciling laser Doppler and speckle measurements of dermal perfusion by the use of multi-exposure speckle has prompted an investigation of speckle effects arising from directed blood flow which might be expected in the small blood vessels of the eye. Unlike dermal scatter, the blood in retinal vessels is surrounded by few small and stationary scatterers able to assist the return of light energy by large-angle scatter. Returning light is expected to come from multiple small angle scatter from the large red blood cells which dominate the fluid. This work compares speckle measurements on highly scattering skin, with measurements on flow in a retinal phantom consisting of a glass capillary which is itself immersed in an index matching fluid to provide a flat air-phantom interface. Brownian motion dominated measurements when small easily levitated scatters were used, and flow was undetectable. With whole-blood, Brownian motion was small and directed flows in the expected region of tens of mm/s were detectable. The nominal flow speed relates to the known pump rate; within the capillary the flow will have a profile reducing toward the walls. The pulsatile effects on laser speckle contrast in the retina are discussed with preliminary multi-exposure measurements on retinal vessels using a fundus camera. Differences between the multiple exposure curves and power spectra of perfused tissue and ordered flow are discussed.

  13. Highly accurate thermal flow microsensor for continuous and quantitative measurement of cerebral blood flow.

    PubMed

    Li, Chunyan; Wu, Pei-ming; Wu, Zhizhen; Limnuson, Kanokwan; Mehan, Neal; Mozayan, Cameron; Golanov, Eugene V; Ahn, Chong H; Hartings, Jed A; Narayan, Raj K

    2015-10-01

    Cerebral blood flow (CBF) plays a critical role in the exchange of nutrients and metabolites at the capillary level and is tightly regulated to meet the metabolic demands of the brain. After major brain injuries, CBF normally decreases and supporting the injured brain with adequate CBF is a mainstay of therapy after traumatic brain injury. Quantitative and localized measurement of CBF is therefore critically important for evaluation of treatment efficacy and also for understanding of cerebral pathophysiology. We present here an improved thermal flow microsensor and its operation which provides higher accuracy compared to existing devices. The flow microsensor consists of three components, two stacked-up thin film resistive elements serving as composite heater/temperature sensor and one remote resistive element for environmental temperature compensation. It operates in constant-temperature mode (~2 °C above the medium temperature) providing 20 ms temporal resolution. Compared to previous thermal flow microsensor based on self-heating and self-sensing design, the sensor presented provides at least two-fold improvement in accuracy in the range from 0 to 200 ml/100 g/min. This is mainly achieved by using the stacked-up structure, where the heating and sensing are separated to improve the temperature measurement accuracy by minimization of errors introduced by self-heating. PMID:26256480

  14. Luteal blood flow in patients undergoing GnRH agonist long protocol

    PubMed Central

    2011-01-01

    Background Blood flow in the corpus luteum (CL) is closely related to luteal function. It is unclear how luteal blood flow is regulated. Standardized ovarian-stimulation protocol with a gonadotropin-releasing hormone agonist (GnRHa long protocol) causes luteal phase defect because it drastically suppresses serum LH levels. Examining luteal blood flow in the patient undergoing GnRHa long protocol may be useful to know whether luteal blood flow is regulated by LH. Methods Twenty-four infertile women undergoing GnRHa long protocol were divided into 3 groups dependent on luteal supports; 9 women were given ethinylestradiol plus norgestrel (Planovar) orally throughout the luteal phase (control group); 8 women were given HCG 2,000 IU on days 2 and 4 day after ovulation induction in addition to Planovar (HCG group); 7 women were given vitamin E (600 mg/day) orally throughout the luteal phase in addition to Planovar (vitamin E group). Blood flow impedance was measured in each CL during the mid-luteal phase by transvaginal color-pulsed-Doppler-ultrasonography and was expressed as a CL-resistance index (CL-RI). Results Serum LH levels were remarkably suppressed in all the groups. CL-RI in the control group was more than the cutoff value (0.51), and only 2 out of 9 women had CL-RI values < 0.51. Treatments with HCG or vitamin E significantly improved the CL-RI to less than 0.51. Seven of the 8 women in the HCG group and all of the women in the vitamin E group had CL-RI < 0.51. Conclusion Patients undergoing GnRHa long protocol had high luteal blood flow impedance with very low serum LH levels. HCG administration improved luteal blood flow impedance. This suggests that luteal blood flow is regulated by LH. PMID:21219663

  15. Nonlinear dynamics of the blood flow studied by Lyapunov exponents.

    PubMed

    Bracic, M; Stefanovska, A

    1998-05-01

    In order to gain an insight into the dynamics of the cardiovascular system throughout which the blood circulates, the signals measured from peripheral blood flow in humans were analyzed by calculating the Lyapunov exponents. Over a wide range of algorithm parameters, paired values of both the global and the local Lyapunov exponents were obtained, and at least one exponent equaled zero within the calculation error. This may be an indication of the deterministic nature and finite number of degrees of freedom of the cardiovascular system governing the blood-flow dynamics on a time scale of minutes. A difference was observed in the Lyapunov dimension of controls and athletes. PMID:9608852

  16. 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

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

    SciTech Connect

    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 blood 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.

  18. 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.

  19. 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…

  20. Cerebral blood flow measured by NMR indicator dilution in cats

    SciTech Connect

    Ewing, J.R.; Branch, C.A.; Helpern, J.A.; Smith, M.B.; Butt, S.M.; Welch, K.M.

    1989-02-01

    We developed techniques to assess the utility of a nuclear magnetic resonance (NMR) indicator for cerebral blood flow studies in cats, using Freon-22 for the first candidate. A PIN-diode-switched NMR experiment allowed the acquisition of an arterial as well as a cerebral fluorine-19 signal proportional to concentration vs. time in a 1.89 T magnet. Mean +/- SD blood:brain partition coefficients for Freon-22 were estimated at 0.93 +/- 0.08 for gray matter and 0.77 +/- 0.12 for white matter. Using maximum-likelihood curve fitting, estimates of mean +/- SD resting cerebral blood flow were 50 +/- 19 ml/100 g-min for gray matter and 5.0 +/- 2.0 ml/100 g-min for white matter. Hypercapnia produced the expected increases in gray and white matter blood flow. The physiologic effects of Freon-22, including an increase in cerebral blood flow itself with administration of 40% by volume, may limit its use as an indicator. Nevertheless, the NMR techniques described demonstrate the feasibility of fluorine-19-labeled compounds as cerebral blood flow indicators and the promise for their use in humans.

  1. 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) PMID:2704596

  2. The effect of ventricular assist devices on cerebral blood flow and blood pressure fractality.

    PubMed

    Bellapart, Judith; Chan, Gregory S H; Tzeng, Yu-Chieh; Ainslie, Philip N; Dunster, Kimble R; Barnett, Adrian G; Boots, Rob; Fraser, John F

    2011-09-01

    Biological signals often exhibit self-similar or fractal scaling characteristics which may reflect intrinsic adaptability to their underlying physiological system. This study analysed fractal dynamics of cerebral blood flow in patients supported with ventricular assist devices (VAD) to ascertain if sustained modifications of blood pressure waveform affect cerebral blood flow fractality. Simultaneous recordings of arterial blood pressure and cerebral blood flow velocity using transcranial Doppler were obtained from five cardiogenic shock patients supported by VAD, five matched control patients and five healthy subjects. Computation of a fractal scaling exponent (α) at the low-frequency time scale by detrended fluctuation analysis showed that cerebral blood flow velocity exhibited 1/f fractal scaling in both patient groups (α = 0.95 ± 0.09 and 0.97 ± 0.12, respectively) as well as in the healthy subjects (α = 0.86 ± 0.07). In contrast, fluctuation in blood pressure was similar to non-fractal white noise in both patient groups (α = 0.53 ± 0.11 and 0.52 ± 0.09, respectively) but exhibited 1/f scaling in the healthy subjects (α = 0.87 ± 0.04, P < 0.05 compared with the patient groups). The preservation of fractality in cerebral blood flow of VAD patients suggests that normal cardiac pulsation and central perfusion pressure changes are not the integral sources of cerebral blood flow fractality and that intrinsic vascular properties such as cerebral autoregulation may be involved. However, there is a clear difference in the fractal scaling properties of arterial blood pressure between the cardiogenic shock patients and the healthy subjects. PMID:21775798

  3. Detecting Blood Flow Response to Stimulation of the Human Eye

    PubMed Central

    Pechauer, Alex D.; Huang, David; Jia, Yali

    2015-01-01

    Retinal blood supply is tightly regulated under a variety of hemodynamic considerations in order to satisfy a high metabolic need and maintain both vessel structure and function. Simulation of the human eye can induce hemodynamics alterations, and attempt to assess the vascular reactivity response has been well documented in the scientific literature. Advancements in noninvasive imaging technologies have led to the characterization of magnitude and time course in retinal blood flow response to stimuli. This allowed for a better understanding of the mechanism in which blood flow is regulated, as well as identifying functional impairments in the diseased eye. Clinically, the ability to detect retinal blood flow reactivity during stimulation of the eye offers potential for the detection, differentiation, and diagnosis of diseases. PMID:26504775

  4. 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. PMID:2312140

  5. Use of laser speckle flowgraphy in ocular blood flow research.

    PubMed

    Sugiyama, Tetsuya; Araie, Makoto; Riva, Charles E; Schmetterer, Leopold; Orgul, Selim

    2010-11-01

    Laser speckle flowgraphy (LSFG) allows for the quantitative estimation of blood flow in the optic nerve head, choroid, retina and iris in vivo. It was developed to facilitate the non-contact analysis of ocular blood flow in living eyes, utilizing the laser speckle phenomenon. The technique uses a fundus camera, a diode laser, an image sensor, an infrared charge-coupled device (CCD) camera and a high-resolution digital CCD camera. Normalized blur (NB), an approximate reciprocal of speckle contrast, represents an index of blood velocity, and shows a good correlation with tissue blood flow rates determined with the microsphere method in the retina, choroid or iris, as well as blood flow rates determined with the hydrogen gas clearance method in the optic nerve head. The square blur ratio (SBR), another index for quantitative estimation of blood velocity, is proportional to the square of the NB. The SBR is theoretically a more exact measurement which is proportional to velocity, whereas the NB is an approximation. Normalized blur was calculated in earlier versions of LSFG because of technical limitations; the SBR is used in current versions of the LSFG instrument. As these values are in arbitrary units, they should not be used to make comparisons between different eyes or different sites in an eye. Clinical protocols, calibration, evaluation procedures and possible limitations of the LSFG technique are described and the results of ocular blood flow studies using LSFG are briefly summarized. The LSFG method is suitable for monitoring the time-course of change in the tissue circulation at the same site in the same eye at various intervals, ranging from seconds to months. Unresolved issues concern the effect of pupil size on measurement results, the effects of various stimulations, and how to measure choroidal and retinal blood flow velocity separately without using the blue-component of argon laser. PMID:19725814

  6. Appearance of rapidly flowing blood on magnetic resonance images

    SciTech Connect

    Bradley, W.G. Jr.; Waluch, V.; Lai, K.S.; Fernandez, E.J.; Spalter, C.

    1984-12-01

    The appearance of rapidly flowing blood on imaging (MRI) was evaluated using flow phantoms and dye infusion experiments. Laminar flow can be maintained at high velocities in small-diameter vessels. Under such conditions, flow-related enhancement may be observed several slices into a multislice imaging volume. As the velocity increases, turbulence occurs. The increased random motion of the protons causes loss of intensity on the first-echo image, although rephasing with increased intensity can be noted on the second-echo image. The flow pattern of a simple intraluminal obstruction is demonstrated by MRI and dye infusion experiments. Clinical examples of the phantom findings are shown and applications are discussed.

  7. Quantitative OCT angiography of optic nerve head blood flow

    PubMed Central

    Jia, Yali; Morrison, John C.; Tokayer, Jason; Tan, Ou; Lombardi, Lorinna; Baumann, Bernhard; Lu, Chen D.; Choi, WooJhon; Fujimoto, James G.; Huang, David

    2012-01-01

    Optic nerve head (ONH) blood flow may be associated with glaucoma development. A reliable method to quantify ONH blood flow could provide insight into the vascular component of glaucoma pathophysiology. Using ultrahigh-speed optical coherence tomography (OCT), we developed a new 3D angiography algorithm called split-spectrum amplitude-decorrelation angiography (SSADA) for imaging ONH microcirculation. In this study, a method to quantify SSADA results was developed and used to detect ONH perfusion changes in early glaucoma. En face maximum projection was used to obtain 2D disc angiograms, from which the average decorrelation values (flow index) and the percentage area occupied by vessels (vessel density) were computed from the optic disc and a selected region within it. Preperimetric glaucoma patients had significant reductions of ONH perfusion compared to normals. This pilot study indicates OCT angiography can detect the abnormalities of ONH perfusion and has the potential to reveal the ONH blood flow mechanism related to glaucoma. PMID:23243564

  8. Regional myocardial blood flow in man during dipyridamole coronary vasodilation

    SciTech Connect

    Sorensen, S.G.; Groves, B.M.; Horwitz, L.D.; Chaudhuri, T.K.

    1985-06-01

    Regional myocardial blood flow before and after intravenous dipyridamole (0.56 mg/kg) was measured during cardiac catheterization in 11 patients using the /sup 133/Xe washout technique. Significant increases in heart rate and decreases in systolic blood pressure were observed with dipyridamole infusion. However, double product and cardiac output did not differ before or after drug infusion. Regional myocardial blood flow increased from 67 to 117 ml/100 mg/min in myocardial segments supplied by nonobstructed coronary arteries. In stenotic coronary arteries, flow increased from 57 to 79 ml/100 mg/min with dipyridamole. We conclude that dipyridamole infusion results in flow differences which discriminate stenotic from nonstenotic coronary arteries.

  9. Quantifying the glycocalyx effects in blood flow in capillaries

    NASA Astrophysics Data System (ADS)

    Deng, Mingge; Lei, Huan; Caswell, Bruce; Karniadakis, George

    2011-11-01

    We employ Dissipative Particle Dynamics (DPD) to simulate blood flow in small capillaries with the glycocalyx attached to the endothelial surface. The effects of the glycocalyx on hematocrit and resistance to blood flow are analyzed by comparing with and without glycocalyx attached to the surface. Of particular interest is the quantification of the slip boundary condition at the edge of glycocalyx and also of the glycocalyx deformation at different grafting densities, stiffness and height of the glycocalyx. In addition to the physical insight gained for this important but relatively unexplored bio-flow, simple models for the slip velocity will be proposed that can be used in continuum simulations of blood flow in micro-vessels.

  10. A numerical analysis of the aortic blood flow pattern during pulsed cardiopulmonary bypass.

    PubMed

    Gramigna, V; Caruso, M V; Rossi, M; Serraino, G F; Renzulli, A; Fragomeni, G

    2015-01-01

    In the modern era, stroke remains a main cause of morbidity after cardiac surgery despite continuing improvements in the cardiopulmonary bypass (CPB) techniques. The aim of the current work was to numerically investigate the blood flow in aorta and epiaortic vessels during standard and pulsed CPB, obtained with the intra-aortic balloon pump (IABP). A multi-scale model, realized coupling a 3D computational fluid dynamics study with a 0D model, was developed and validated with in vivo data. The presence of IABP improved the flow pattern directed towards the epiaortic vessels with a mean flow increase of 6.3% and reduced flow vorticity. PMID:24962383

  11. Dissipative particle dynamics modeling of blood flow in arterial bifurcations

    NASA Astrophysics Data System (ADS)

    Li, Xuejin; Lykov, Kirill; Pivkin, Igor V.; Karniadakis, George Em

    2013-11-01

    The motion of a suspension of red blood cells (RBCs) flowing in bifurcations is investigated using both low-dimensional RBC (LD-RBC) and multiscale RBC (MS-RBC) models based on dissipative particle dynamics (DPD). The blood flow is first simulated in a symmetric geometry between the diverging and converging channels to satisfy the periodic flow assumption along the flow direction. The results show that the flowrate ratio of the daughter channels and the feed hematocrit level has considerable influence on blood-plasma separation. We also propose a new method to model the inflow and outflow boundaries for the blood flow simulations: the inflow at the inlet is duplicated from a fully developed flow generated by DPD fluid with periodic boundary conditions; the outflow in two adjacent regions near the outlet is controlled by adaptive forces to keep the flowrate and velocity gradient equal, while the particles leaving the microfluidic channel at the outlet at each time step are removed from the system. The simulation results of the developing flow match analytical solutions from continuum theory. Plasma skimming and the all-or-nothing phenomenon of RBCs in bifurcation have been investigated in the simulations. The simulation results are consistent with previous experimental results and theoretical predictions. This work is supported by the NIH Grant R01HL094270.

  12. Ultrasonic Enrichment of Flowing Blood Cells in Capillars: Influence of the Flow Rate

    NASA Astrophysics Data System (ADS)

    Carreras, Pilar; Gonzalez, Itziar; Ahumada, Oscar

    Red blood cells subjected to standing waves collect at the pressure nodes during their flow motion. Blood is a non-newtonian fluid whose density and other properties are defined by its flow velocity. Their drift motion is governed by the radiation force together with hydrodynamic conditions. This work presents a study of the blood cell enrichment performed in a rectangular capillar at f=1 MHz as a function of their flow motion. The cells collect along the central axis of the capillary in very few seconds, with a clearance in other lateral areas. Optimal flow rates below 100uL/min were found in the experiments.

  13. An experimental study on drugs for improving blood circulation and removing blood stasis in treating mild chronic hepatic damage.

    PubMed

    Xie, F; Li, X; Sun, K; Chu, Y; Cao, H; Chen, N; Wang, W; Liu, M; Liu, W; Mao, D

    2001-09-01

    Large and small doses of drugs for improving blood circulation and removing blood stasis were used in model rats to treat mild chronic hepatic damage induced by carbon tetrachloride (CCl4). The results show that large dose of Dang Gui ([symbol: see text] Radix Angelicae Sinensis) and Dan Shen ([symbol: see text] Radix Salviae Miltiorrhizae) (drugs for regulating blood flow) and small dose of Yu Jin ([symbol: see text] Radix Curcumae) and Niu Xi ([symbol: see text] Radix Achyranthis Bidentatae) (drugs for activating blood flow) can significantly elevate the activity of SOD (P < 0.05) and/or lower the T/K ratio, markedly reduce the MDA content (P < 0.05 or P < 0.01) and significantly decrease the activities of ALT and AST (P < 0.05 or P < 0.01), demonstrating that these drugs are effective in combating oxygen free radicals (OFR) in chronic liver damage. On the contrary, large dose of Tu Bie Chong ([symbol: see text] Eupolyphaga seu Steleophaga) and E Zhu ([symbol: see text] Rhizoma Curcumae) (drugs for removing blood stasis) tend to increase the ALT and AST (P < 0.05) activities. The results suggest that the synergism of elevation of the SOD activity and reduction of T/K ratio contributes to the action of drugs for improving blood circulation and removing blood stasis in combating the liver damage induced by CCl4. PMID:11789334

  14. 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.

  15. Effects of graded doses of epinephrine on regional myocardial blood flow during cardiopulmonary resuscitation in swine

    SciTech Connect

    Brown, C.G.; Werman, H.A.; Davis, E.A.; Hobson, J.; Hamlin, R.L.

    1987-02-01

    Although epinephrine has been shown to improve myocardial blood flow during cardiopulmonary resuscitation (CPR), the effects of standard as well as larger doses of epinephrine on regional myocardial blood flow have not been examined. In this study we compared the effects of various doses of epinephrine on regional myocardial blood flow after a 10 min arrest in a swine preparation. Fifteen swine weighing greater than 15 kg each were instrumented for regional myocardial blood flow measurements with tracer microspheres. Regional blood flow was measured during normal sinus rhythm. After 10 min of ventricular fibrillation, CPR was begun and regional myocardial blood flow was determined. Animals were then randomly assigned to receive 0.02, 0.2, or 2.0 mg/kg epinephrine by peripheral injection. One minute after drug administration, regional myocardial blood flow measurements were repeated. The adjusted regional myocardial blood flows (ml/min/100 g) for animals given 0.02, 0.2, and 2.0 mg/kg epinephrine, respectively, were as follows: left atrium, 0.9, 67.4, and 58.8; right atrium, 0.3, 46.2, and 38.5; right ventricle, 0.7, 82.3, and 66.9; right interventricular septum, 1.7, 125.5, and 99.1; left interventricular septum, 2.8, 182.8, 109.5; mesointerventricular septum, 16.8, 142.2, and 79.2; left ventricular epicardium, 19.2, 98.5 and 108.7; left ventricular mesocardium, 22.8, 135.0, and 115.8; and left ventricular endocardium, 2.5, 176.1, and 132.9). All comparisons between the groups receiving 0.02 and 0.2 mg/kg epinephrine were statistically significant (p less than .05).

  16. Reproducibility of measurements of regional resting and hyperemic myocardial blood flow assessed with PET

    SciTech Connect

    Nagamachi, S.; Czernin, J.; Kim, A.S.

    1996-10-01

    PET with {sup 13}N-ammonia permits the noninvasive quantification of myocardial blood flow (MBF) in humans. The present study was done to assess the reproducibility of quantitative blood flow measurements at rest and during pharmacologically induced hyperemia in healthy individuals. Thirty healthy volunteers (26 men, 4 women) were studied. Paired measurements of MBF at rest (n = 21), during adenosine (n = 15) and during dipyridamole (n = 7) were performed using a two-compartment model for {sup 13}N-ammonia PET. The mean difference between baseline and follow-up blood flow (% difference) was calculated to assess reproducibility. No significant difference was observed between resting blood flow at baseline or follow-up (15.8% {plus_minus} 15.8%; p = ns). Baseline and follow-up resting blood flow were linearly correlated (r = 0.63, p < 0.005). Normalization of resting blood flow to the rate pressure product improved the reproducibility significantly (15.8% {plus_minus} 15.8% versus 10.1% {plus_minus} 10.5%, p < 0.05). Baseline and follow-up hyperemic myocardial blood flow did not differ (11.8% {plus_minus} 9.4%; p = ns) and were linearly correlated (r = 0.69, p < 0.0005). MBF at rest can be measured reproducibly with {sup 13}N-ammonia PET. The individual response to pharmacologic stress appears to be relatively consistent. Thus, serial blood flow measurements with {sup 13}N-ammonia PET can be used to quantify the effect of various interventions on MBF and vasodilatory reserve. 41 refs., 3 figs., 4 tabs.

  17. 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.

  18. Regional neurohypophysial and hypothalamic blood flow in rats during hypercapnia

    SciTech Connect

    Bryan, R.M. Jr.; Myers, C.L.; Page, R.B.

    1988-08-01

    Regional cerebral blood flow (rCBF) was measured in the neurohypophysis and hypothalamus in normocapnic and hypercapnic rats using (/sup 14/C)isopropyliodoamphetamine. Rats were surgically prepared using nitrous oxide and halothane and placed in plaster restraining casts. Hypercapnia was produced by increasing the fractional concentration of inspired CO/sub 2/ (FICO/sub 2/). rCBF in normocapnic rats was higher in the paraventricular nucleus, supraoptic nucleus, median eminence, and neural lobe than rates previously measured by use of diffusible tracers. During hypercapnia blood flow increased linearly with arterial PCO/sub 2/ (PACO/sub 2/) in all regions except the median eminence and neural lobe, which were not affected by hypercapnia. When rats were pretreated with phentolamine (1 mg/kg) to block the alpha-adrenergic receptors, blood flow in the median eminence and neural lobe increased significantly during hypercapnia. We conclude that blood flow in the cell bodies of the paraventricular nucleus and supraoptic nucleus is regulated differently during hypercapnia than blood flow in the nerve terminals in the median eminence and neural lobe. Furthermore, vasodilation produced by increased CO/sub 2/ is offset by alpha-receptor stimulation in the median eminence and neural lobe.

  19. Development of miniaturized mass flow meter for an axial flow blood pump.

    PubMed

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

    2007-05-01

    To grasp the conditions of patients and implantable artificial hearts, it is essential to monitor the blood flow rate continuously and noninvasively. However, it is difficult to monitor the pump flow rate in an implantable artificial heart, because the conventional flow meter is too large to implant into the human body, and the flow estimation method is influenced by changes in the blood characteristics and the pump performance. In particular, the power consumption has neither linearity nor uniqueness with respect to the pump flow rate in an axial flow blood pump. In this research, we develop a prototype miniaturized mass flow meter that uses centrifugal force F(c) for discharged patients with an axial flow blood pump. This flow meter measures the F(c) corresponding to the mass flow rate, and implements compensation for static pressure. Because the strain gauges are attached outside of the curved tube, this mass flow meter has no blood contact point, resulting in a compact design. To evaluate the measurement accuracy and the tracking performance, the mass flow meter was compared with the conventional ultrasonic flow meter in a mock-up circulation study. As a result, the measurement error ranging from 0.5 to 5.0 L/min was less than +/-10% with respect to the maximum flow rate. The tracking performance of pulsation flow was approximately equivalent to that of the conventional flow meter. These experiments demonstrated that the prototype miniaturized mass flow meter using F(c) could accurately measure the mass flow rate continuously and noninvasively. PMID:17470214

  20. Hall effect in electrolyte flow measurements: introduction to blood flow measurements.

    PubMed

    Szwast, Maciej; Piatkiewicz, Wojciech

    2012-06-01

    The Hall effect has been applied to electrolyte flow measurement. It has been proven that Hall voltage does not depend on electrolyte concentration; however, there is a linear relationship between Hall voltage and flow velocity. Obtained results for electrolyte allow us to suppose that Hall effect can be used to determine blood flow. Research on blood will be conducted as the next step. PMID:22145845

  1. Pentobarbital changes compartmental contribution to cerebral blood flow

    SciTech Connect

    Laurent, J.P.; Lawner, P.; Simeone, F.A.; Fink, E.

    1982-04-01

    Barbiturates were administered to normal dogs, establishing an isoelectric electrocorticogram. Cortical cerebral blood flows (CBF) and deeper CBF's were respectively measured by krypton-85 (85Kr) and xenon-133 (133 Xe). Following barbiturate administration, the two methods of measuring CBF showed a poor coefficient of variation (r.0.12, p less than 0.05). The cortical flows decreased less than the fast compartment flows. A shifting of percentage contribution of flow to the slow compartment (60% increase, p less than 0.001) was observed after barbiturate infusion. A selective shunting of blood flow to the slower areas may explain the lowering of intracranial pressure and protection of the deep white matter observed by many authors who use barbiturates in clinical an experimental situations.

  2. 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. PMID:18204314

  3. 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

  4. Verapamil buffering effect on the abrupt elevation in blood pressure, linkage with microcirculatory blood flow.

    PubMed

    Gmitrov, J

    2008-01-01

    1 We studied the effects of verapamil on sudden elevation in blood pressure, microcirculation and arterial baroreflex sensitivity (BRS). 2 Thirty experiments (10 controls and 20 with verapamil) were performed in rabbits sedated using pentobarbital infusion (5 mg kg(-1) h(-1)). 3 BRS, mean femoral artery blood pressure (MAP), heart rate (HR) and ear lobe skin microcirculatory blood flow, estimated using microphotoelectric plethysmography (MPPG), were simultaneously measured during 30 min of verapamil infusion (20 mug kg(-1) min(-1)). BRS was assessed from HR and MAP responses to intravenous phenylephrine (Ph) and by power spectral analysis using transfer function (TF) from MAP to the HR (BRS(Ph,TF)). 4 Verapamil significantly increased microcirculatory blood flow, and decreased BRS(Ph,TF) and phenylephrine-induced abrupt elevation in MAP (MAP(AE)). 5 A significant inverse correlation was found between verapamil-induced changes in MAP(AE), BRS and in microcirculatory blood flow, measured before phenylephrine blood pressure ramps (DeltaMAP(AE) with DeltaBRS(TF), r = -0.47, P < 0.036; DeltaMAP(AE) with DeltaMPPG, r = -0.49, P < 0.025). 6 These results suggest involvement of the arterial baroreflex and vascular blood pressure-buffering mechanisms, their enhancement by verapamil, and thus a potential benefit of verapamil in cardiovascular conditions where patients present with abrupt high elevations in blood pressure. PMID:18598288

  5. Rinse trough with improved flow

    DOEpatents

    O`Hern, T.J.; Grasser, T.W.

    1998-08-11

    Novel rinse troughs accomplish thorough uniform rinsing. The troughs are suitable for one or more essentially planar objects having substantially the same shape. The troughs ensure that each surface is rinsed uniformly. The new troughs provide uniform rinse fluid flow over the objects` surfaces to accomplish a more thorough rinse than prior art troughs. 5 figs.

  6. Rinse trough with improved flow

    DOEpatents

    O'Hern, Timothy J.; Grasser, Thomas W.

    1998-01-01

    Novel rinse troughs accomplish thorough uniform rinsing. The troughs are suitable for one or more essentially planar objects having substantially the same shape. The troughs ensure that each surface is rinsed uniformly. The new troughs provide uniform rinse fluid flow over the objects' surfaces to accomplish a more thorough rinse than prior art troughs.

  7. Intravital video microscopy measurements of retinal blood flow in mice.

    PubMed

    Harris, Norman R; Watts, Megan N; Leskova, Wendy

    2013-01-01

    Alterations in retinal blood flow can contribute to, or be a consequence of, ocular disease and visual dysfunction. Therefore, quantitation of altered perfusion can aid research into the mechanisms of retinal pathologies. Intravital video microscopy of fluorescent tracers can be used to measure vascular diameters and bloodstream velocities of the retinal vasculature, specifically the arterioles branching from the central retinal artery and of the venules leading into the central retinal vein. Blood flow rates can be calculated from the diameters and velocities, with the summation of arteriolar flow, and separately venular flow, providing values of total retinal blood flow. This paper and associated video describe the methods for applying this technique to mice, which includes 1) the preparation of the eye for intravital microscopy of the anesthetized animal, 2) the intravenous infusion of fluorescent microspheres to measure bloodstream velocity, 3) the intravenous infusion of a high molecular weight fluorescent dextran, to aid the microscopic visualization of the retinal microvasculature, 4) the use of a digital microscope camera to obtain videos of the perfused retina, and 5) the use of image processing software to analyze the video. The same techniques can be used for measuring retinal blood flow rates in rats. PMID:24429840

  8. Blood flow and wall motion in an idealized left ventricle

    NASA Astrophysics Data System (ADS)

    Tavoularis, Stavros; Doyle, Matthew; Bourgault, Yves

    2006-11-01

    During diastole of the heart, the left ventricle (LV) expands as a result of both incoming blood flow and wall material relaxation. In this work, we simulate both of these effects, along with the fluid-structure interaction between the blood and the heart wall. As a first step leading to more realistic studies, we approximate the LV by a prolate ellipsoid and the valves by cylindrical tubes. The mitral valve is open, allowing blood to enter the LV, whereas the aortic valve is closed. To account for the effects of muscle fibers in the heart wall, we model the wall as a multi-layered orthotropic linear elastic material with different material properties in the fiber, sheet, and sheet-normal directions within each layer. Results will be presented for this idealized configuration, while simulations of blood flow in realistic canine left and right ventricles are currently underway.

  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. 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

  11. 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. PMID:24791016

  12. Association of Meteorological Variables and Coronary Blood Flow.

    PubMed

    Yildiz, Ali; Sezen, Yusuf; Gunebakmaz, Ozgur; Kaya, Zekeriya; Altiparmak, Ibrahim Halil; Erkus, Emre; Demirbag, Recep; Yilmaz, Remzi

    2015-09-01

    We aimed to assess the impact of meteorological variables on coronary blood flow (CBF). Coronary blood flow was evaluated using the thrombolysis in myocardial infarction frame count (TFC). The association of CBF with meteorological parameters such as temperature, relative humidity, total solar radiation, atmospheric pressure, wind velocity, and total sunshine duration were investigated as well as demographic, clinical, and laboratory characteristics. Assessment of 1206 patients (median age = 53 years, 723 females) revealed the presence of slow coronary flow (SCF) in 196 patients. Daily maximum temperature [odds ratio = 0.951, 95% confidence interval = 0.916-0.986, P = .007] was the only independent predictor of the presence of SCF, whereas systolic blood pressure (β = -0.139, P = .026), hematocrit level (β = 0.128, P = .044), and daily maximum temperature (β = -1.479, P = .049) were independent predictors of log10 (mean TFC). Findings of the present study suggest a role of meteorological parameters in CBF regulation. PMID:25313313

  13. A Porous Media Model for Blood Flow within Reticulated Foam

    NASA Astrophysics Data System (ADS)

    Ortega, Jason

    2013-11-01

    A porous media model is developed for non-Newtonian blood flow through reticulated foam at Reynolds numbers ranging from 10-8 to 10. This empirical model effectively divides the pressure gradient versus flow speed curve into three regimes, in which either the non-Newtonian viscous forces, the Newtonian viscous forces, or the inertial fluid forces are most prevalent. When compared to simulation data of blood flow through two reticulated foam geometries, the model adequately captures the pressure gradient within all three regimes, especially that within the Newtonian regime where blood transitions from a power-law to a constant viscosity fluid. This work was supported by the National Institutes of Health/National Institute of Biomedical Imaging and Bioengineering Grant R01EB000462 and partially performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. Unsteady non-Newtonian blood flow through a tapered overlapping stenosed catheterized vessel.

    PubMed

    Ali, N; Zaman, A; Sajid, M; Nieto, J J; Torres, A

    2015-11-01

    The unsteady flow characteristics of blood in a catheterized overlapping stenosed artery are analyzed in presence of body acceleration and magnetic field. The stenosed arterial segment is modeled as a rigid constricted tube. An improved shape of stenosis in the realm of the formulation of the arterial narrowing caused by atheroma is integrated in the present study. The catheter inside the artery is approximated by a thin rigid tube of small radius while the streaming blood in the artery is characterized by the Carreau model. Employing mild stenosis condition, the governing equation of the flow is derived which is then solving numerically using finite difference scheme. The variation of axial velocity, flow rate, resistance impendence and wall shear stress is shown graphically for various parameters of interest. The flow patterns illustrating the global behavior of blood are also presented. PMID:26361287

  15. Shear stress related blood damage in laminar couette flow.

    PubMed

    Paul, Reinhard; Apel, Jörn; Klaus, Sebastian; Schügner, Frank; Schwindke, Peter; Reul, Helmut

    2003-06-01

    Artificial organs within the blood stream are generally associated with flow-induced blood damage, particularly hemolysis of red blood cells. These damaging effects are known to be dependent on shear forces and exposure times. The determination of a correlation between these flow-dependent properties and actual hemolysis is the subject of this study. For this purpose, a Couette device has been developed. A fluid seal based on fluorocarbon is used to separate blood from secondary external damage effects. The shear rate within the gap is controlled by the rotational speed of the inner cylinder, and the exposure time by the amount of blood that is axially pumped through the device per given time. Blood damage is quantified by the index of hemolysis (IH), which is calculated from photometric plasma hemoglobin measurements. Experiments are conducted at exposure times from texp=25 - 1250 ms and shear rates ranging from tau=30 up to 450 Pa ensuring Taylor-vortex free flow characteristics. Blood damage is remarkably low over a broad range of shear rates and exposure times. However, a significant increase in blood damage can be observed for shear stresses of tau>or= 425 Pa and exposure times of texp>or= 620 ms. Maximum hemolysis within the investigated range is IH=3.5%. The results indicate generally lower blood damage than reported in earlier studies with comparable devices, and the measurements clearly indicate a rather abrupt (i.e., critical levels of shear stresses and exposure times) than gradual increase in hemolysis, at least for the investigated range of shear rates and exposure times. PMID:12780506

  16. Heart blood flow simulation: a perspective review.

    PubMed

    Doost, Siamak N; Ghista, Dhanjoo; Su, Boyang; Zhong, Liang; Morsi, Yosry S

    2016-01-01

    Cardiovascular disease (CVD), the leading cause of death today, incorporates a wide range of cardiovascular system malfunctions that affect heart functionality. It is believed that the hemodynamic loads exerted on the cardiovascular system, the left ventricle (LV) in particular, are the leading cause of CVD initiation and propagation. Moreover, it is believed that the diagnosis and prognosis of CVD at an early stage could reduce its high mortality and morbidity rate. Therefore, a set of robust clinical cardiovascular assessment tools has been introduced to compute the cardiovascular hemodynamics in order to provide useful insights to physicians to recognize indicators leading to CVD and also to aid the diagnosis of CVD. Recently, a combination of computational fluid dynamics (CFD) and different medical imaging tools, image-based CFD (IB-CFD), has been widely employed for cardiovascular functional assessment by providing reliable hemodynamic parameters. Even though the capability of CFD to provide reliable flow dynamics in general fluid mechanics problems has been widely demonstrated for many years, up to now, the clinical implications of the IB-CFD patient-specific LVs have not been applicable due to its limitations and complications. In this paper, we review investigations conducted to numerically simulate patient-specific human LV over the past 15 years using IB-CFD methods. Firstly, we divide different studies according to the different LV types (physiological and different pathological conditions) that have been chosen to reconstruct the geometry, and then discuss their contributions, methodologies, limitations, and findings. In this regard, we have studied CFD simulations of intraventricular flows and related cardiology insights, for (i) Physiological patient-specific LV models, (ii) Pathological heart patient-specific models, including myocardial infarction, dilated cardiomyopathy, hypertrophic cardiomyopathy and hypoplastic left heart syndrome. Finally, we

  17. Coronary blood flow during cardiopulmonary resuscitation in swine

    SciTech Connect

    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: 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.

  18. 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. PMID:24920757

  19. Renal blood flow and oxygenation drive nephron progenitor differentiation

    PubMed Central

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

    2014-01-01

    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. PMID:24920757

  20. 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.

  1. Flow of Red Blood Cells in Stenosed Microvessels.

    PubMed

    Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

    2016-01-01

    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. PMID:27319318

  2. Flow of Red Blood Cells in Stenosed Microvessels

    PubMed Central

    Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

    2016-01-01

    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. PMID:27319318

  3. High speed optical holography of retinal blood flow

    NASA Astrophysics Data System (ADS)

    Pellizzari, M.; Simonutti, M.; Degardin, J.; Sahel, J.-A.; Fink, M.; Paques, M.; Atlan, M.

    2016-08-01

    We performed non-invasive video imaging of retinal blood flow in a pigmented rat by holographic interferometry of near-infrared laser light backscattered by retinal tissue, beating against an off-axis reference beam sampled at a frame rate of 39 kHz with a high throughput camera. Local Doppler contrasts emerged from the envelopes of short-time Fourier transforms and the phase of autocorrelation functions of holograms rendered by Fresnel transformation. This approach permitted imaging of blood flow in large retinal vessels (30 microns diameter) over 400 by 400 pixels with a spatial resolution of 8 microns and a temporal resolution of 6.5 ms.

  4. Esophageal blood flow in the cat. Normal distribution and effects of acid perfusion

    SciTech Connect

    Hollwarth, M.E.; Smith, M.; Kvietys, P.R.; Granger, D.N.

    1986-03-01

    The radioactive microsphere technique was used to estimate blood flow to different regions of the esophagus and to adjacent regions of the stomach before and after perfusion of the esophagus with hydrochloric acid (pH 1.5) for 5 min. Under resting conditions total blood flow, as well as blood flow to the mucosal-submucosal layer and the muscular layer, to both sphincters was significantly higher than to the esophageal body. Blood flow to the adjacent regions of the stomach was significantly higher than esophageal blood flow. Acid perfusion resulted in a large increase in total blood flow in both sphincters and the lower esophageal body. Gastric blood flow was not altered by acid perfusion. The esophageal hyperemia resulted primarily from an increase in blood flow to the muscular layer; mucosal-submucosal blood flow was increased only in the lower esophageal sphincter. The present study indicates that short periods (5 min) of gastroesophageal reflux may increase esophageal blood flow.

  5. Computational biorheology of human blood flow in health and disease.

    PubMed

    Fedosov, Dmitry A; Dao, Ming; Karniadakis, George Em; Suresh, Subra

    2014-02-01

    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

  6. An Electromagnetic Catheter Blood Flow Meter of Minimal Lateral Dimensions*

    PubMed Central

    Kolin, Alexander

    1970-01-01

    A method is described to reduce the lateral dimensions of an electromagnetic catheter blood flow meter to the maximum possible extent. To achieve this, the magnetic field is generated by a magnet placed outside the subject. Thus, only the electrodes and a minimal supporting structure have to be introduced into the blood vessel to pick up the electromotive force induced in the blood streaming at right angles to the magnetic field. To suppress induction of a transformer electromotive force in the electrode leads, the latter form a co-axial lead system of small gauge. One electrode is at the tip of the insulated external tube of this lead system (a gauge no. 28 hypodermic tube) and is insulated from it. The other electrode is a bare section of the external tube about 2 cm from its tip. The tube is bent at an angle of about 30° just below the second electrode. Thus, this bent section places the two electrodes near two diametrically opposite wall sections of the blood vessels after insertion of the fine catheter via a hollow catheter through a branch blood vessel into the main vessel. The catheter is rotated until the plane containing the bent section is perpendicular to the magnetic field. The potential difference between the two electrodes measures the volume rate of flow through the blood vessel. This principle can be used to monitor the flow in the major blood vessels as well as in their branches. Catheter flow meters down to about 0.5 mm in external diameter have thus been made and much smaller ones can be made without excessive difficulty. Images PMID:5273901

  7. 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.

  8. Vortex method for blood flow through heart valves

    SciTech Connect

    McCracken, M.F.; Peskin, C.S.

    1980-04-01

    A combination vortex-grid method for solving the two-dimensional, incompressible Navier--Stokes equations in regions with complicated internal, elastic boundaries is presented. The authors believe the method to be applicable to the case of at least moderately high Reynolds number flow. The method is applied to the study of blood flow through the mammalian mitral valve. Previous work of Peskin is extended and the conjecture that the behavior of mammalian heart valves is independent of Reynolds number is supported.

  9. Cerebral Blood Flow Autoregulation and Dysautoregulation.

    PubMed

    Armstead, William M

    2016-09-01

    This article provides a review of cerebral autoregulation, particularly as it relates to the clinician scientist experienced in neuroscience in anesthesia and critical care. Topics covered are biological mechanisms; methods used for assessment of autoregulation; effects of anesthetics; role in control of cerebral hemodynamics in health and disease; and emerging areas, such as role of age and sex in contribution to dysautoregulation. Emphasis is placed on bidirectional translational research wherein the clinical informs the study design of basic science studies, which, in turn, informs the clinical to result in development of improved therapies for treatment of central nervous system conditions. PMID:27521192

  10. Recovery of testicular blood flow following ligation of testicular vessels

    SciTech Connect

    Pascual, J.A.; Villanueva-Meyer, J.; Salido, E.; Ehrlich, R.M.; Mena, I.; Rajfer, J.

    1989-08-01

    To determine whether initial ligation of the testicular vessels of the high undescended testis followed by a delayed secondary orchiopexy is a viable alternative to the classical Fowler-Stephens procedure, a series of preliminary experiments were conducted in the rat in which testicular blood flow was measured by the 133-xenon washout technique before, and 1 hour and 30 days after ligation of the vessels. In addition, testicular histology, and testis and sex-accessory tissue weights were measured in 6 control, 6 sham operated and 6 testicular vessel ligated rats 54 days after vessel ligation. The data demonstrate that ligation and division of the testicular blood vessels produce an 80 per cent decrease in testicular blood flow 1 hour after ligation of the vessels. However, 30 days later testis blood flow returns to the control and pre-treatment value. There were no significant changes in testis or sex-accessory tissue weights 54 days after vessel ligation. Histologically, 4 of the surgically operated testes demonstrated necrosis of less than 25 per cent of the seminiferous tubules while 1 testis demonstrated more than 75 per cent necrosis. The rest of the tubules in all 6 testes demonstrated normal spermatogenesis. From this study we conclude that initial testicular vessel ligation produces an immediate decrease in testicular blood flow but with time the collateral vessels are able to compensate and return the testis blood flow to its normal pre-treatment value. These preliminary observations lend support for the concept that initial ligation of the testicular vessels followed by a delayed secondary orchiopexy in patients with a high undescended testis may be a possible alternative to the classical Fowler-Stephens approach.

  11. Plethysmography without venous occlusion for measuring forearm blood flow: comparison with venous occlusive method.

    PubMed

    Chuah, Seong S; Woolfson, Peter I; Pullan, Brian R; Lewis, Philip S

    2004-09-01

    Limb blood flow is widely used as an indicator of the human vascular properties. There are only few non-invasive methods for its measurement such as venous occlusion plethysmography. However, several authors have questioned its validity. The problems appear to be related to the process of venous occlusion. We developed two methods to measure forearm blood flow by plethysmography without venous occlusion in combination with Doppler velocimetry (without imaging). Method 1: the gradient of a tangent drawn on the latter part of the down stroke of the plethysmographic volume pulse is an approximation of venous blood flow in the absence of diastolic blood flow. At equilibrium, it equals the average arterial flow in a cardiac cycle. The Doppler velocity waveform recorded simultaneously allows improvement of this approximation when there is diastolic blood flow. Method 2: the volume pulse detected by a plethysmograph calibrated in absolute volume is used to calibrate the velocity waveform recorded simultaneously to produce an approximation of arterial volumetric flow waveform. Bland-Altman analysis shows both methods have good correlation and agreement with venous occlusion plethysmography at rest. Method 1: mean difference (blood flow measured by venous occlusion minus calculated flow) = 0.10 ml/pulse (+/-0.18), limits of agreement = -0.41 and 0.61 ml/pulse. Method 2: mean difference = -0.041 ml/pulse (+/-0.15), limits of agreement = -0.45 and 0.37 ml/pulse. During hyperaemia, venous occlusion plethysmography grossly underestimated relative to the new methods. The new methods are not dependent on venous occlusion and produce consistent results with or without hyperaemia. PMID:15383087

  12. Effect of blood flow parameters on flow patterns at arterial bifurcations--studies in models.

    PubMed

    Liepsch, D W

    1990-01-01

    Atherosclerotic lesions are found primarily at arterial bends and bifurcations. Flow disturbances at these anatomic sites play a major role in atherogenesis. How hemodynamic factors such as vessel geometry, the pulsatile nature of blood flow, vessel wall elasticity and the non-Newtonian flow behavior of blood influence the flow field at these sites must be clarified. We have performed fundamental studies using a birefringent solution in a simplified rigid 90 degree T-bifurcation and pulsatile flow. The velocity distribution was measured with a laser Doppler anemometer. Flow in an elastic abdominal aorta model has been visualized using magnetic resonance imaging. In both flow studies, zones with negative velocity were found. These model measurements demonstrate that no flow parameter can be neglected. Further detailed studies are necessary to examine the interaction between fluid dynamic and cellular surface properties. PMID:2404201

  13. 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

  14. 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.

  15. Age and gender related differences in aortic blood flow

    NASA Astrophysics Data System (ADS)

    Enevoldsen, Marie Sand; Pedersen, Mads Møller; Hemmsen, Martin Christian; Lönn, Lars; Henneberg, Kaj-Åge; Jensen, Jørgen Arendt

    2012-03-01

    The abdominal aorta (AA) is predisposed to development of abdominal aneurysms (AAA), a focal dilatation with fatal consequences if left untreated. The blood flow patterns is thought to play an important role in the development of AAA. The purpose of this work is to investigate the blood flow patterns within a group of healthy volunteers (six females, eight males) aged 23 to 76 years to identify changes and differences related to age and gender. The healthy volunteers were categorized by gender (male/female) and age (below/above 35 years). Subject-specific flow and geometry data were acquired using the research interface on a Profocus ultrasound scanner (B-K Medical, Herlev, Denmark; segmentation of 3D magnetic resonance angiography (Magnetom Trio, Siemens Healthcare, Erlangen, Germany). The largest average diameter was among the elderly males (19.7 (+/- 1.33) mm) and smallest among the young females (12.4 (+/- 0.605) mm). The highest peak systolic velocity was in the young female group (1.02 (+/- 0.336) m/s) and lowest in the elderly male group (0.836 (+/- 0.127) m/s). A geometrical change with age was observed as the AA becomes more bended with age. This also affects the blood flow velocity patterns, which are markedly different from young to elderly. Thus, changes in blood flow patterns in the AA related to age and gender are observed. Further investigations are needed to determine the relation between changes in blood flow patterns and AAA development.

  16. Enhancement of topical delivery of drugs via direct penetration by reducing blood flow rate in skin.

    PubMed

    Higaki, K; Nakayama, K; Suyama, T; Amnuaikit, Chomchan; Ogawara, K; Kimura, T

    2005-01-20

    decreasing tendency. In conclusion, direct penetration of drugs applied topically is enhanced by reducing the local blood flow in the skin, which would be a possible approach to improve the local delivery of drugs applied topically. PMID:15620862

  17. Design optimization of flow channel and performance analysis for a new-type centrifugal blood pump

    NASA Astrophysics Data System (ADS)

    Ji, J. J.; Luo, X. W.; Y Wu, Q.

    2013-12-01

    In this paper, a new-type centrifugal blood pump, whose impeller is suspended inside a pump chamber with hydraulic bearings, is presented. In order to improve the hydraulic performance of the pump, an internal flow simulation is conducted to compare the effects of different geometrical parameters of pump flow passage. Based on the numerical results, the pumps can satisfy the operation parameters and be free of hemolysis. It is noted that for the pump with a column-type supporter at its inlet, the pump head and hydraulic efficiency decreases compared to the pump with a step-type support structure. The performance drop is caused by the disturbed flow upstream impeller inlet. Further, the unfavorable flow features such as reverse flow and low velocity in the pump may increases the possibility of thrombus. It is also confirmed that the casing shape can little influence pump performance. Those results are helpful for design optimization in blood pump development.

  18. Cerebral blood flow links insulin resistance and baroreflex sensitivity.

    PubMed

    Ryan, John P; Sheu, Lei K; Verstynen, Timothy D; Onyewuenyi, Ikechukwu C; Gianaros, Peter J

    2013-01-01

    Insulin resistance confers risk for diabetes mellitus and associates with a reduced capacity of the arterial baroreflex to regulate blood pressure. Importantly, several brain regions that comprise the central autonomic network, which controls the baroreflex, are also sensitive to the neuromodulatory effects of insulin. However, it is unknown whether peripheral insulin resistance relates to activity within central autonomic network regions, which may in turn relate to reduced baroreflex regulation. Accordingly, we tested whether resting cerebral blood flow within central autonomic regions statistically mediated the relationship between insulin resistance and an indirect indicator of baroreflex regulation; namely, baroreflex sensitivity. Subjects were 92 community-dwelling adults free of confounding medical illnesses (48 men, 30-50 years old) who completed protocols to assess fasting insulin and glucose levels, resting baroreflex sensitivity, and resting cerebral blood flow. Baroreflex sensitivity was quantified by measuring the magnitude of spontaneous and sequential associations between beat-by-beat systolic blood pressure and heart rate changes. Individuals with greater insulin resistance, as measured by the homeostatic model assessment, exhibited reduced baroreflex sensitivity (b = -0.16, p < .05). Moreover, the relationship between insulin resistance and baroreflex sensitivity was statistically mediated by cerebral blood flow in central autonomic regions, including the insula and cingulate cortex (mediation coefficients < -0.06, p-values < .01). Activity within the central autonomic network may link insulin resistance to reduced baroreflex sensitivity. Our observations may help to characterize the neural pathways by which insulin resistance, and possibly diabetes mellitus, relates to adverse cardiovascular outcomes. PMID:24358272

  19. 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.

  20. Improved Ultrasonic Transducer For Measuring Cryogenic Flow

    NASA Technical Reports Server (NTRS)

    Barkhoudarian, Sarkis

    1991-01-01

    Improved ultrasonic transducer used to measure flow of cryogenic fluid. Includes wedge made nonintrusive by machining it out of bulk material of duct carrying fluid. Skewed surfaces of wedge suppress standing waves, thus reducing ringing and increasing signal-to-noise ratio. Increases accuracy of measurements of times of arrival of ultrasonic pulses, from which times flow inferred.

  1. Ascending aortic blood flow dynamics following intense exercise.

    PubMed

    Kilgour, R D; Sellers, W R

    1990-10-01

    The purpose of this study was to compare and contrast aortic blood flow kinetics during recovery from intense aerobic (maximal oxygen uptake test) and anaerobic (Wingate anaerobic power test) exercise. Fifteen healthy male subjects (VO2max = 56.1 +/- 5.8 mk/kg/min) participated in this study. Beat-to-beat peak aortic blood flow velocity (pkV) and acceleration (pkA) measurements were obtained by placing a 3.0 MHz continuous-wave ultrasonic transducer on the suprasternal notch at rest and during recovery (immediately post-exercise, 2.5 min, and 5.0 min) following the two exercise conditions. Peak velocity and acceleration significantly increased (p less than 0.01) from rest to immediately post-exercise and remained elevated throughout the 5-min recovery period. No differences were observed between the aerobic and anaerobic tests. Stroke distance significantly declined (p less than 0.01) immediately following exercise and progressively rose during the 5-min recovery period. The results indicate that: 1) aortic blood flow kinetics remained elevated during short-term recovery, and 2) intense aerobic and anaerobic exercise exhibit similar post-exercise aortic blood flow kinetics. PMID:2262232

  2. Control of cutaneous blood flow by central nervous system.

    PubMed

    Ootsuka, Youichirou; Tanaka, Mutsumi

    2015-01-01

    Hairless skin acts as a heat exchanger between body and environment, and thus greatly contributes to body temperature regulation by changing blood flow to the skin (cutaneous) vascular bed during physiological responses such as cold- or warm-defense and fever. Cutaneous blood flow is also affected by alerting state; we 'go pale with fright'. The rabbit ear pinna and the rat tail have hairless skin, and thus provide animal models for investigating central pathway regulating blood flow to cutaneous vascular beds. Cutaneous blood flow is controlled by the centrally regulated sympathetic nervous system. Sympathetic premotor neurons in the medullary raphé in the lower brain stem are labeled at early stage after injection of trans-synaptic viral tracer into skin wall of the rat tail. Inactivation of these neurons abolishes cutaneous vasomotor changes evoked as part of thermoregulatory, febrile or psychological responses, indicating that the medullary raphé is a common final pathway to cutaneous sympathetic outflow, receiving neural inputs from upstream nuclei such as the preoptic area, hypothalamic nuclei and the midbrain. Summarizing evidences from rats and rabbits studies in the last 2 decades, we will review our current understanding of the central pathways mediating cutaneous vasomotor control. PMID:27227053

  3. Longitudinal Cerebral Blood Flow Changes during Speech in Hereditary Ataxia

    ERIC Educational Resources Information Center

    Sidtis, John J.; Strother, Stephen C.; Naoum, Ansam; Rottenberg, David A.; Gomez, Christopher

    2010-01-01

    The hereditary ataxias constitute a group of degenerative diseases that progress over years or decades. With principal pathology involving the cerebellum, dysarthria is an early feature of many of the ataxias. Positron emission tomography was used to study regional cerebral blood flow changes during speech production over a 21 month period in a…

  4. Control of cutaneous blood flow by central nervous system

    PubMed Central

    Ootsuka, Youichirou; Tanaka, Mutsumi

    2015-01-01

    Hairless skin acts as a heat exchanger between body and environment, and thus greatly contributes to body temperature regulation by changing blood flow to the skin (cutaneous) vascular bed during physiological responses such as cold- or warm-defense and fever. Cutaneous blood flow is also affected by alerting state; we ‘go pale with fright’. The rabbit ear pinna and the rat tail have hairless skin, and thus provide animal models for investigating central pathway regulating blood flow to cutaneous vascular beds. Cutaneous blood flow is controlled by the centrally regulated sympathetic nervous system. Sympathetic premotor neurons in the medullary raphé in the lower brain stem are labeled at early stage after injection of trans-synaptic viral tracer into skin wall of the rat tail. Inactivation of these neurons abolishes cutaneous vasomotor changes evoked as part of thermoregulatory, febrile or psychological responses, indicating that the medullary raphé is a common final pathway to cutaneous sympathetic outflow, receiving neural inputs from upstream nuclei such as the preoptic area, hypothalamic nuclei and the midbrain. Summarizing evidences from rats and rabbits studies in the last 2 decades, we will review our current understanding of the central pathways mediating cutaneous vasomotor control. PMID:27227053

  5. Optically measured microvascular blood flow contrast of malignant breast tumors.

    PubMed

    Choe, Regine; Putt, Mary E; Carlile, Peter M; Durduran, Turgut; Giammarco, Joseph M; Busch, David R; Jung, Ki Won; Czerniecki, Brian J; Tchou, Julia; Feldman, Michael D; Mies, Carolyn; Rosen, Mark A; Schnall, Mitchell D; DeMichele, Angela; Yodh, Arjun G

    2014-01-01

    Microvascular blood flow contrast is an important hemodynamic and metabolic parameter with potential to enhance in vivo breast cancer detection and therapy monitoring. Here we report on non-invasive line-scan measurements of malignant breast tumors with a hand-held optical probe in the remission geometry. The probe employs diffuse correlation spectroscopy (DCS), a near-infrared optical method that quantifies deep tissue microvascular blood flow. Tumor-to-normal perfusion ratios are derived from thirty-two human subjects. Mean (95% confidence interval) tumor-to-normal ratio using surrounding normal tissue was 2.25 (1.92-2.63); tumor-to-normal ratio using normal tissues at the corresponding tumor location in the contralateral breast was 2.27 (1.94-2.66), and using normal tissue in the contralateral breast was 2.27 (1.90-2.70). Thus, the mean tumor-to-normal ratios were significantly different from unity irrespective of the normal tissue chosen, implying that tumors have significantly higher blood flow than normal tissues. Therefore, the study demonstrates existence of breast cancer contrast in blood flow measured by DCS. The new, optically accessible cancer contrast holds potential for cancer detection and therapy monitoring applications, and it is likely to be especially useful when combined with diffuse optical spectroscopy/tomography. PMID:24967878

  6. [Changes of cerebral blood flow during diving reactions in humans].

    PubMed

    Baranova, T I; Berlov, D N; Ianvareva, I N

    2014-05-01

    The characteristics of human cerebral blood flow were estimated during the implementation of the diving response, simulated by complex cold-hypoxic-hypercapnic exposure (CHHE), and under the influence of separate cold, hypercapnic and hypoxic stimuli. Was studied 18 people aged 18-22 years who had no special training. Cerebral blood flow was recorded by transcranial Doppler. It is shown that in the CHHE with the respect initial state to observe a marked increase in cerebral blood flow linear velocity (BFV) to 82.3 ± 15.2%, as well as reducing characterizing the tone of resistance vessels of the brain pulsatility index (PI) to 77.2 ± 13.1%. During cold and tactile stimulation of facial skin BFV and PI did not change significantly, with a single breath hold (Genchi test) BFV increased by 52.3 ± 12.5%, PI at 64.5 ± 15%. The latent period of cerebral blood flow (14-43) allow suppose metabolic (chemical) nature of regulatory influences, which provide changes of considered indicators. PMID:25669101

  7. Naloxone increases blood flow in the human hand.

    PubMed Central

    Archer, A G; Benroubi, M; Pyke, D A; Wiles, P G

    1985-01-01

    Intravenous injection of 2 mg naloxone produced a rapid and pronounced rise of blood flow (6.3 +/- 5.0 to 67.0 +/- 15.1 ml min-1 100 ml-1) and skin temperature (28.3 +/- 3.0 to 32.4 +/- 1.2 degrees C) in the finger and hand of seven of ten normal volunteers. In the other three there was only a small response. Skin temperature did not change in either the face or the foot. Three responding subjects who were retested with 0.4 mg naloxone showed a smaller and briefer response. To exclude a local effect of naloxone on skin blood flow due to release of histamine, responders and non-responders were tested with naloxone and morphine pricked into the skin of the hand and forearm. All showed a weal and flare reaction to morphine which was not abolished by mixture with naloxone; none showed any reaction to naloxone alone. These results suggest that, in some subjects at least, skin blood flow in the hand may be under endogenous opioid control and they raise the possibility that opioid antagonists might have value in the treatment of disorders of skin blood flow such as Raynaud's disease. PMID:4020703

  8. 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.

  9. Dynamic deformability of sickle red blood cells in microphysiological flow

    PubMed Central

    Alapan, Y.; Matsuyama, Y.; Little, J. A.; Gurkan, U. A.

    2016-01-01

    In sickle cell disease (SCD), hemoglobin molecules polymerize intracellularly and lead to a cascade of events resulting in decreased deformability and increased adhesion of red blood cells (RBCs). Decreased deformability and increased adhesion of sickle RBCs lead to blood vessel occlusion (vaso-occlusion) in SCD patients. Here, we present a microfluidic approach integrated with a cell dimensioning algorithm to analyze dynamic deformability of adhered RBC at the single-cell level in controlled microphysiological flow. We measured and compared dynamic deformability and adhesion of healthy hemoglobin A (HbA) and homozygous sickle hemoglobin (HbS) containing RBCs in blood samples obtained from 24 subjects. We introduce a new parameter to assess deformability of RBCs: the dynamic deformability index (DDI), which is defined as the time-dependent change of the cell’s aspect ratio in response to fluid flow shear stress. Our results show that DDI of HbS-containing RBCs were significantly lower compared to that of HbA-containing RBCs. Moreover, we observed subpopulations of HbS containing RBCs in terms of their dynamic deformability characteristics: deformable and non-deformable RBCs. Then, we tested blood samples from SCD patients and analyzed RBC adhesion and deformability at physiological and above physiological flow shear stresses. We observed significantly greater number of adhered non-deformable sickle RBCs than deformable sickle RBCs at flow shear stresses well above the physiological range, suggesting an interplay between dynamic deformability and increased adhesion of RBCs in vaso-occlusive events. PMID:27437432

  10. Red blood cells radial dispersion in blood flowing through microchannels: The role of temperature.

    PubMed

    Pinho, Diana; Rodrigues, Raquel O; Faustino, Vera; Yaginuma, Tomoko; Exposto, José; Lima, Rui

    2016-07-26

    The behavior of suspensions of individual blood cells, such as red blood cells (RBCs), flowing through microvessels and microfluidic systems depend strongly on the hematocrit (Hct), microvessel topology and cell properties. Although it is well known that blood rheological properties are temperature dependent, to the best of our knowledge no work has studied the role of the temperature on the RBCs dispersion. A powerful way to investigate this latter effect is through a high-speed video microscopy system, which provides detailed flow measurements of each individual RBC. Hence, the effect of temperature on the RBCs dispersion flowing through a 100μm glass capillary was examined by means of a confocal micro-PTV system. Hundreds of labeled RBCs were tracked at moderate Hct (12%) and at four different temperatures, i.e., 25°C, 32°C, 37°C and 42°C. The results yielded an enhancement of the RBCs diffusion as the temperature increases. Hence, our findings show that RBCs radial dispersion is temperature dependent and as a result the temperature should not be ignored in future blood flow studies. We believe that this finding is important for a better understanding of blood mass transport mechanisms under both physiological and pathological conditions. PMID:26671221

  11. Heart rate in the pathophysiology of coronary blood flow and myocardial ischaemia: benefit from selective bradycardic agents

    PubMed Central

    Heusch, G

    2008-01-01

    Starting out from a brief description of the determinants of coronary blood flow (perfusion, pressure, extravascular compression, autoregulation, metabolic regulation, endothelium-mediated regulation and neurohumoral regulation) the present review highlights the overwhelming importance of metabolic regulation such that coronary blood flow is increased at increased heart rate under physiological circumstances and the overwhelming importance of extravascular compression such that coronary blood flow is decreased at increased heart rate through reduction of diastolic duration in the presence of severe coronary stenoses. The review goes on to characterize the role of heart rate in the redistribution of regional myocardial blood flow between a normal coronary vascular tree with preserved autoregulation and a poststenotic vasculature with exhausted coronary reserve. When flow is normalized by heart rate, there is a consistent close relationship of regional myocardial blood flow and contractile function for each single cardiac cycle no matter whether or not there is a coronary stenosis and what the actual blood flow is. β-Blockade improves both flow and function along this relationship. When the heart rate reduction associated with β-blockade is prevented by pacing, α-adrenergic coronary vasoconstriction is unmasked and both flow and function are deteriorated. Selective heart rate reduction, however, improves both flow and function without any residual negative effect such as unmasked α-adrenergic coronary vasoconstriction or negative inotropic action. PMID:18223669

  12. Effects of midazolam on cerebral blood flow in human volunteers

    SciTech Connect

    Forster, A.; Juge, O.; Morel, D.

    1982-06-01

    The effects of intravenously administered midazolam on cerebral blood flow were evaluated in eight healthy volunteers using the /sup 133/Xe inhalation technique. Six minutes after an intravenous dose of 0.15 mg/kg midazolam, the cerebral blood flow decreased significantly (P less than 0.001) from a value of 40.6 +/- 3.3 to a value of 27.0 +/- 5.0 ml . 100 g-1 . min-1. Cerebrovascular resistance (CVR) increased from 2.8 +/- 0.2 to 3.9 to 0.6 mmHg/(ml . 100 g-1 . min-1)(P less than 0.001). Mean arterial blood pressure decreased significantly (P less than 0.05) from 117 +/- 8 to 109 +/- 9 mmHg and arterial carbon dioxide tension increased from 33.9 +/- 2.3 to 38.6 +/- 3.2 mmHg (P less than 0.05). Arterial oxygen tension remained stable throughout the study, 484 +/- 95 mmHg before the administration of midazolam and 453 +/- 76 mmHg after. All the subjects slept after the injection of the drug and had anterograde amnesia of 24.5 +/- 5 min. The decrease in mean arterial blood pressure was probably not important since it remained in the physiologic range for cerebral blood flow autoregulation. The increase in arterial carbon dioxide tension observed after the midazolam injection may have partially counteracted the effect of this new benzodiazepine on cerebral blood flow. Our data suggest that midazolam might be a safe agent to use for the induction of anethesia in neurosurgical patients with intracranial hypertension.

  13. Diurnal variations in blood flow at optic nerve head and choroid in healthy eyes: diurnal variations in blood flow.

    PubMed

    Iwase, Takeshi; Yamamoto, Kentaro; Ra, Eimei; Murotani, Kenta; Matsui, Shigeyuki; Terasaki, Hiroko

    2015-02-01

    To investigate the diurnal variations of the ocular blood flow in healthy eyes using laser speckle flowgraphy (LSFG), and to determine the relationship of the diurnal variations between the ocular blood flow and other ocular parameters.This prospective cross-sectional study was conducted at Nagoya University Hospital. We studied 13 healthy volunteers whose mean age was 33.5 ± 7.6 years. The mean blur rate (MBR), expressing the relative blood flow, on the optic nerve head (ONH) and choroidal blood flow was determined by LSFG (LSFG-NAVI) every 3 hours from 6:00 to 24:00 hours. The intraocular pressure (IOP), choroidal thickness measured by enhanced depth imaging optical coherence tomography, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) in the brachial artery were also recorded. We evaluated the diurnal variations of the parameters and compared the MBR to the other parameters using a linear mixed model.The diurnal variations of the MBR on the ONH varied significantly with a trough at 9:00 hours and a peak at 24:00 hours (P < 0.001, linear mixed model). The MBR of choroid also had significant diurnal variations with a trough at 15:00 hours and a peak at 18:00 hours (P = 0.001). The IOP (P < 0.001), choroidal thickness (P < 0.001), SBP (P = 0.005), DBP (P = 0.001), and HR (P < 0.001) also had significant diurnal variations. Although the diurnal variation of the MBR on the ONH was different from the other parameters, that on the choroid was significantly and positively correlated with the DBP (P = 0.002), mean arterial pressure (P = 0.023), and mean ocular perfusion pressure (P = 0.047).We found significant diurnal variations in the ONH and choroidal blood flow. Although the ONH blood flow had its own diurnal variation because of strong autoregulation, the choroidal blood flow was more likely affected by systemic circulatory factors because of poor autoregulation. PMID:25674750

  14. Choroidal Blood Flow Change in Eyes with High Myopia

    PubMed Central

    Yang, Young Seong

    2015-01-01

    Purpose To evaluate choroidal blood flow changes in eyes with high myopia according to the pulsatile components of ocular blood flow analysis. Methods A total of 104 subjects (52 males and 52 females) were included in this study. One eye of each participant was randomly selected and assigned to one of four refractive groups, designated as, hyperopes (n = 20; refractive error, ≥+1.00 diopter [D]), emmetropes (n = 28; refractive error, ±0.75 D), lower myopes (n = 33; refractive error, -1.00 to -4.75 D), and high myopes (n = 23; refractive error, ≤-5.00 D). Components of pulse amplitude (OBFa), pulse volume (OBFv), pulse rate (OBFr), and pulsatile ocular blood flow (POBF) were analyzed using a blood flow analyzer. Intraocular pressure and axial length were measured. Results Pulsatile components of OBFa, OBFv, and POBF showed positive correlations with refractive error and showed negative correlations with axial length (r = 0.729, r = 0.772, r = 0.781, respectively, all p < 0.001; r = -0.727, r = -0.762, r = -0.771, respectively, all p < 0.001). The correlations of refractive error and axial length with OBFr were irrelevant (r = -0.157, p = 0.113; r = 0.123, p = 0.213). High myopes showed significantly lower OBFa, OBFv, and POBF than the other groups (all p < 0.001). Conclusions Axial length changes in high myopes potentially influence choroidal blood flow, assuming the changes are caused by narrowing of the choroidal vessel diameter and increasing rigidity of the choroidal vessel wall. These finding explains the influence of axial length on OBFa, OBFv, and POBF, but not on OBFr. Thus, changes in axial length and the possible influence of these changes on the physical properties of choroidal vessels is the mechanism believed to be responsible for putting high myopes at risk for ocular vascular diseases. PMID:26457036

  15. Determination of renal blood flow by thermodilution method.

    PubMed

    Leivestad, T; Brodwall, E K; Simonsen, S

    1978-09-01

    The single bolus thermodilution method for measurement of renal vein blood flow was tested. In model experiments the thermodilution method was compared with graduated cylinder measurements over a flow range from 50 to 1050 ml/min. There was a good correlation between the two methods (r = 0.98) with a mean of differences of 5.2%. In eighteen patients measurements were performed in duplicate in thirty-one renal veins. Comparison was made between the first (x) and second (u) measurement--performed within 3 min. The correlation between the two was very good (r = 0.99; y = 1.03x - 11.48). In twelve patients bilateral renal vein blood flow measurements were performed simultaneous to blood flow measurement by PAH clearance. The correlation between total flow measured by thermodilution (y) and by the clearance method (x) was good (r = 0.98; y = 0.79x + 221). It is concluded that the thermodilution method requires catheterization of the renal veins, but is otherwise simple to perform, is inexpensive and gives reliable results. It is particularly advantageous when repeated measurements in the study of acute changes in renal haemodynamics is desirable. PMID:705231

  16. Modelling the Transport of Nanoparticles under Blood Flow using an Agent-based Approach

    PubMed Central

    Fullstone, Gavin; Wood, Jonathan; Holcombe, Mike; Battaglia, Giuseppe

    2015-01-01

    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. PMID:26058969

  17. Quantitative blood flow velocity imaging using laser speckle flowmetry.

    PubMed

    Nadort, Annemarie; Kalkman, Koen; van Leeuwen, Ton G; Faber, Dirk J

    2016-01-01

    Laser speckle flowmetry suffers from a debated quantification of the inverse relation between decorrelation time (τc) and blood flow velocity (V), i.e. 1/τc = αV. Using a modified microcirculation imager (integrated sidestream dark field - laser speckle contrast imaging [SDF-LSCI]), we experimentally investigate on the influence of the optical properties of scatterers on α in vitro and in vivo. We found a good agreement to theoretical predictions within certain limits for scatterer size and multiple scattering. We present a practical model-based scaling factor to correct for multiple scattering in microcirculatory vessels. Our results show that SDF-LSCI offers a quantitative measure of flow velocity in addition to vessel morphology, enabling the quantification of the clinically relevant blood flow, velocity and tissue perfusion. PMID:27126250

  18. Quantitative blood flow velocity imaging using laser speckle flowmetry

    NASA Astrophysics Data System (ADS)

    Nadort, Annemarie; Kalkman, Koen; van Leeuwen, Ton G.; Faber, Dirk J.

    2016-04-01

    Laser speckle flowmetry suffers from a debated quantification of the inverse relation between decorrelation time (τc) and blood flow velocity (V), i.e. 1/τc = αV. Using a modified microcirculation imager (integrated sidestream dark field - laser speckle contrast imaging [SDF-LSCI]), we experimentally investigate on the influence of the optical properties of scatterers on α in vitro and in vivo. We found a good agreement to theoretical predictions within certain limits for scatterer size and multiple scattering. We present a practical model-based scaling factor to correct for multiple scattering in microcirculatory vessels. Our results show that SDF-LSCI offers a quantitative measure of flow velocity in addition to vessel morphology, enabling the quantification of the clinically relevant blood flow, velocity and tissue perfusion.

  19. SPECT study of regional cerebral blood flow in Alzheimer disease

    SciTech Connect

    Bonte, F.J.; Ross, E.D.; Chehabi, H.H.; Devous, M.D. Sr.

    1986-07-01

    A common cause of dementia in late midlife and old age is Alzheimer disease (AD), which affects more than one in 20 individuals over the age of 65. Past studies of regional cerebral blood flow (rCBF) in patients with AD here suggested blood flow abnormalities, but findings have differed. We have studied 37 patients diagnosed as having AD with inhalation and washout of /sup 133/Xe and single-photon emission computed tomography (SPECT), obtaining evidence of abnormal rCBF patterns in 19. Flow reductions were most common in the temporoparietal regions and were occasionally found in the frontal areas. Investigators using positron-emission tomography (PET) have identified similar findings with respect to rCBF and regional oxygen, glucose, and protein metabolism. The SPECT determination of rCBF, which gives information similar to that provided by PET, may assume importance in the diagnosis of AD and in the differential diagnosis of the dementias.

  20. Quantitative blood flow velocity imaging using laser speckle flowmetry

    PubMed Central

    Nadort, Annemarie; Kalkman, Koen; van Leeuwen, Ton G.; Faber, Dirk J.

    2016-01-01

    Laser speckle flowmetry suffers from a debated quantification of the inverse relation between decorrelation time (τc) and blood flow velocity (V), i.e. 1/τc = αV. Using a modified microcirculation imager (integrated sidestream dark field - laser speckle contrast imaging [SDF-LSCI]), we experimentally investigate on the influence of the optical properties of scatterers on α in vitro and in vivo. We found a good agreement to theoretical predictions within certain limits for scatterer size and multiple scattering. We present a practical model-based scaling factor to correct for multiple scattering in microcirculatory vessels. Our results show that SDF-LSCI offers a quantitative measure of flow velocity in addition to vessel morphology, enabling the quantification of the clinically relevant blood flow, velocity and tissue perfusion. PMID:27126250

  1. Moderate exercise training promotes adaptations in coronary blood flow and adenosine production in normotensive rats

    PubMed Central

    Roque, Fernanda R.; Soci, Ursula Paula Renó; De Angelis, Katia; Coelho, Marcele A.; Furstenau, Cristina R.; Vassallo, Dalton V.; Irigoyen, Maria Claudia; Oliveira, Edilamar M.

    2011-01-01

    OBJECTIVES: Aerobic exercise training prevents cardiovascular risks. Regular exercise promotes functional and structural adaptations that are associated with several cardiovascular benefits. The aim of this study is to investigate the effects of swimming training on coronary blood flow, adenosine production and cardiac capillaries in normotensive rats. METHODS: Wistar rats were randomly divided into two groups: control (C) and trained (T). An exercise protocol was performed for 10 weeks and 60 min/day with a tail overload of 5% bodyweight. Coronary blood flow was quantified with a color microsphere technique, and cardiac capillaries were quantified using light microscopy. Adenine nucleotide hydrolysis was evaluated by enzymatic activity, and protein expression was evaluated by western blot. The results are presented as the means ± SEMs (p<0.05). RESULTS: Exercise training increased the coronary blood flow and the myocardial capillary-to-fiber ratio. Moreover, the circulating and cardiac extracellular adenine nucleotide hydrolysis was higher in the trained rats than in the sedentary rats due to the increased activity and protein expression of enzymes, such as E-NTPDase and 5′-nucleotidase. CONCLUSIONS: Swimming training increases coronary blood flow, number of cardiac capillaries, and adenine nucleotide hydrolysis. Increased adenosine production may be an important contributor to the enhanced coronary blood flow and angiogenesis that were observed in the exercise-trained rats; collectively, these results suggest improved myocardial perfusion. PMID:22189737

  2. Dynamic properties of blood flow and leukocyte mobilization in infected flaps

    SciTech Connect

    Feng, L.J.; Price, D.C.; Mathes, S.J.; Hohn, D. )

    1990-11-01

    Two aspects of the inflammatory response to infection--blood flow alteration and leukocyte mobilization--are investigated in the canine model. The elevation of paired musculocutaneous (MC) and random pattern (RP) flaps allowed comparison of healing flaps with significant differences in blood flow (lower in random pattern flaps) and resistance to infection (greater in musculocutaneous flaps). Blood flow changes as determined by radioactive xenon washout were compared in normal skin and distal flap skin both after elevation and following bacterial inoculation. Simultaneous use of In-111 labeled leukocytes allowed determination of leukocyte mobilization and subsequent localization in response to flap infection. Blood flow significantly improved in the musculocutaneous flap in response to infection. Although total leukocyte mobilization in the random pattern flap was greater, the leukocytes in the musculocutaneous flap were localized around the site of bacterial inoculation within the dermis. Differences in the dynamic blood flow and leukocyte mobilization may, in part, explain the greater reliability of musculocutaneous flaps when transposed in the presence of infection.

  3. In vivo cerebral blood flow autoregulation studies using rheoencephalography

    NASA Astrophysics Data System (ADS)

    Bodo, M.; Pearce, F.; Garcia, A.; Van Albert, S.; Settle, T.; Szebeni, J.; Baranyi, L.; Hartings, J.; Armonda, R.

    2010-04-01

    Acute management of patients with traumatic brain/blast injury is a challenge. To minimize secondary injury and improve outcome, it is critical to detect neurological deterioration early, when it is potentially reversible. One potential monitoring method is cerebral electrical impedance (rheoencephalography-REG) because of its non-invasiveness and good time resolution. Reported here are the results of cerebral blood flow (CBF) manipulations comparing electroencephalogram (EEG) with REG (both intra-cerebral) and measuring with surface and skull REG electrodes. Our hypothesis was that REG would reflect spreading depression and CBF autoregulation. Animal experiments were performed using one rat (four trials with intracerebral electrodes), monkeys (n=8, with surface electrodes) and pigs (n = 24 pigs with skull electrodes; 57 trials, 19 types of liposomes). Challenges included intracranial pressure (ICP) elevation, liposome infusion, and hemorrhage. Data were stored on a PC and evaluated off line. CBF autoregulation was evaluated both by visual inspection and by a Matlab script. These studies confirmed that REG reflects CBF autoregulation and that REG is useful for detecting spreading depression (SD), vasospasm and the lower limit of CBF autoregulation. These findings have clinical relevance for use in noninvasive neuro-monitoring in the neurosurgery intensive care and during transportation of patients with brain injury.

  4. In vitro validation of volumetric blood flow measurement using Doppler flow wire.

    PubMed

    Jenni, R; Kaufmann, P A; Jiang, Z; Attenhofer, C; Linka, A; Mandinov, L

    2000-10-01

    Determination of any volumetric blood flow requires assessment of mean blood flow velocity and vessel cross-sectional area. For evaluation of coronary blood flow and flow reserve, however, assessment of average peak velocity alone is widely used, but changes in velocity profile and vessel area are not taken into account. We studied the feasibility of a new method for calculation of volumetric blood flow by Doppler power using a Doppler flow wire. An in vitro model with serially connected silicone tubes of known lumen diameters (1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mm) and pulsatile blood flow ranging from 10 to 200 mL/min was used. A Doppler flow wire was connected to a commercially available Doppler system (FloMap(R), Cardiometrics) for online calculation of the zeroth (M(0)) and the first (M(1)) Doppler moment, as well as mean flow velocity (V(m)). Two different groups of sample volumes (at different gate depths) were used: 1. two proximal sample volumes lying completely within the vessel were required to evaluate the effect of scattering and attenuation on Doppler power, and 2. distal sample volumes intersecting completely the vessel lumen to assess the vessel cross-sectional area. Area (using M(0)) and V(m) (using M(1)/M(0)) obtained from the distal gates were corrected for scattering and attenuation by the data obtained from the proximal gates, allowing calculation of absolute volumetric flow. These results were compared to the respective time collected flow. Correlation between time collected and Doppler-derived flow measurements was 0.98 (p < 0.0001), with a regression line close to the line of equality indicating an excellent agreement of the two measurements in each individual tube. The mean paired flow difference between the two techniques was 1.5 +/- 9.0 mL/min (ns). Direct volumetric blood flow measurement from received Doppler power using a Doppler flow wire system is feasible. This technique may potentially be of great clinical value because it allows an

  5. Ocular Blood Flow and Influencing Factors for Glaucoma.

    PubMed

    Nakazawa, Toru

    2016-01-01

    Open-angle glaucoma (OAG) is characterized by optic nerve fiber atrophy and deterioration of the visual field, corresponding to damage to the optic nerve head. Intraocular pressure (IOP) is currently the only evidence-based, treatable risk factor for OAG. However, normal-tension glaucoma, the most common type of OAG in Asia, is a type of glaucoma with an unclear pathogenesis. Glaucoma is suspected to be a multifactorial disease with IOP-dependent and IOP-independent risk factors, including decreased ocular blood flow (OBF), oxidative stress, decreased axoplasmic flow, and genetic background. A number of epidemiological studies have generated strong evidence that OBF may be an especially important risk factor for the progression of glaucoma. Recent innovations in laser speckle flowgraphy and optical coherence tomography-based angiography have allowed us to noninvasively monitor changes in the microcirculation of the optic nerve head with high reproducibility. Laser speckle flowgraphy-derived measurement parameters include mean blur rate and pulse wave form parameters, whereas the main optical coherence tomography angiography-derived parameter is the vessel index. Decreases in these parameters are associated with the severity of glaucomatous damage, and changes are detectible even in the earliest, preperimetric stage of glaucoma. In the future, OBF analysis may improve significantly because of continuing progress in the development of the relevant instruments. This review will summarize possible connections between systemic and OBF abnormalities and OAG, describe the scientific rationale for these connections, and discuss their potential implications. Thus, this review will summarize the role of OBF in glaucoma pathogenesis and discuss the wide range of IOP-independent risk factors. PMID:26886118

  6. [Synchonization of the blood flow rate in arterial with the changing rate of space of blood pressure with time].

    PubMed

    Zhang, Shenghua; Qin, Renjia

    2012-10-01

    In physiology-related books, there are many relationship curves about blood flow rate in arteries and blood pressure changes with time, but there are not much explanation about such relationship. This is the very the question that the present article tries to answer. We clarified the relations between blood flow rate and blood pressure gradient using the experimental curves as the basis, using Poiseuille Law and relative knowledge of phisics and mathematics, and using analysis and reasoning. Based on the study, it can be concluded that in every course of cardiac cycle, the blood flow rate of any section in artery blood vessel is roughly synchronized with changing rate of space and time of the blood pressure, but blood flow rate is not synchronized with blood pressure. PMID:23198422

  7. Regional brain blood flow in man during acute changes in arterial blood gases

    PubMed Central

    Willie, C K; Macleod, D B; Shaw, A D; Smith, K J; Tzeng, Y C; Eves, N D; Ikeda, K; Graham, J; Lewis, N C; Day, T A; Ainslie, P N

    2012-01-01

    Despite the importance of blood flow on brainstem control of respiratory and autonomic function, little is known about regional cerebral blood flow (CBF) during changes in arterial blood gases. We quantified: (1) anterior and posterior CBF and reactivity through a wide range of steady-state changes in the partial pressures of CO2 () and O2 () in arterial blood, and (2) determined if the internal carotid artery (ICA) and vertebral artery (VA) change diameter through the same range. We used near-concurrent vascular ultrasound measures of flow through the ICA and VA, and blood velocity in their downstream arteries (the middle (MCA) and posterior (PCA) cerebral arteries). Part A (n= 16) examined iso-oxic changes in , consisting of three hypocapnic stages (=∼15, ∼20 and ∼30 mmHg) and four hypercapnic stages (=∼50, ∼55, ∼60 and ∼65 mmHg). In Part B (n= 10), during isocapnia, was decreased to ∼60, ∼44, and ∼35 mmHg and increased to ∼320 mmHg and ∼430 mmHg. Stages lasted ∼15 min. Intra-arterial pressure was measured continuously; arterial blood gases were sampled at the end of each stage. There were three principal findings. (1) Regional reactivity: the VA reactivity to hypocapnia was larger than the ICA, MCA and PCA; hypercapnic reactivity was similar. With profound hypoxia (35 mmHg) the relative increase in VA flow was 50% greater than the other vessels. (2) Neck vessel diameters: changes in diameter (∼25%) of the ICA was positively related to changes in (R2, 0.63 ± 0.26; P < 0.05); VA diameter was unaltered in response to changed but yielded a diameter increase of +9% with severe hypoxia. (3) Intra- vs. extra-cerebral measures: MCA and PCA blood velocities yielded smaller reactivities and estimates of flow than VA and ICA flow. The findings respectively indicate: (1) disparate blood flow regulation to the brainstem and cortex; (2) cerebrovascular resistance is not solely modulated at the level of the arteriolar pial vessels; and (3

  8. Skeletal muscle blood flow and flow heterogeneity during dynamic and isometric exercise in humans.

    PubMed

    Laaksonen, Marko S; Kalliokoski, Kari K; Kyröläinen, Heikki; Kemppainen, Jukka; Teräs, Mika; Sipilä, Hannu; Nuutila, Pirjo; Knuuti, Juhani

    2003-03-01

    The effects of dynamic and intermittent isometric knee extension exercises on skeletal muscle blood flow and flow heterogeneity were studied in seven healthy endurance-trained men. Regional muscle blood flow was measured using positron emission tomography (PET) and an [(15)O]H(2)O tracer, and electromyographic (EMG) activity was recorded in the quadriceps femoris (QF) muscle during submaximal intermittent isometric and dynamic exercises. QF blood flow was 61% (P = 0.002) higher during dynamic exercise. Interestingly, flow heterogeneity was 13% (P = 0.024) lower during dynamic compared with intermittent isometric exercise. EMG activity was significantly higher (P < 0.001) during dynamic exercise, and the change in EMG activity from isometric to dynamic exercise was tightly related to the change in blood flow in the vastus lateralis muscle (r = 0.98, P < 0.001) but not in the rectus femoris muscle (r = -0.09, P = 0.942). In conclusion, dynamic exercise causes higher and less heterogeneous blood flow than intermittent isometric exercise at the same exercise intensity. These responses are, at least partly, related to the increased EMG activity. PMID:12446282

  9. Skeletal blood flow, iliac histomorphometry, and strontium kinetics in osteoporosis: a relationship between blood flow and corrected apposition rate

    SciTech Connect

    Reeve, J.; Arlot, M.; Wootton, R.; Edouard, C.; Tellez, M.; Hesp, R.; Green, J.R.; Meunier, P.J.

    1988-06-01

    In 20 untreated patients with idiopathic or postmenopausal osteoporosis, kinetic studies of skeletal blood flow (using /sup 18/F) and bone turnover (using /sup 85/Sr) were combined with dynamic histomorphometry performed on transiliac biopsies taken within 6 weeks of each other. In 8 patients the combined studies were repeated after treatment. A further 5 patients were studied only while receiving treatment. As expected, skeletal blood flow measured by /sup 18/F correlated with an index of /sup 85/Sr uptake into the exchangeable pools of bone. Additionally and independently, skeletal blood flow correlated with an index of the work rate of the osteoblasts in each multicellular unit of bone (the corrected apposition rate of Parfitt). These correlations were statistically significant in both the untreated patients (P less than 0.05) and the whole group (P less than 0.001). Further indices related to bone turnover at the level of the skeleton as a whole were significantly associated with skeletal blood flow only in the combined group.

  10. External Counterpulsation Reduces Beat-to-Beat Blood Pressure Variability When Augmenting Blood Pressure and Cerebral Blood Flow in Ischemic Stroke

    PubMed Central

    Tian, Ge; Xiong, Li; Lin, Wenhua; Han, Jinghao; Chen, Xiangyan; Leung, Thomas Wai Hong; Soo, Yannie Oi Yan

    2016-01-01

    Background and Purpose External counterpulsation (ECP) is a noninvasive method used to enhance cerebral perfusion by elevating the blood pressure in ischemic stroke. However, the response of the beat-to-beat blood pressure variability (BPV) in ischemic stroke patients during ECP remains unknown. Methods We enrolled recent ischemic stroke patients and healthy controls. Changes in the blood flow velocities in bilateral middle cerebral arteries and the continuous beat-to-beat blood pressure before, during, and after ECP were monitored. Power spectral analysis revealed that the BPV included oscillations at very low frequency (VLF; <0.04 Hz), low frequency (LF; 0.04–0.15 Hz), and high frequency (HF; 0.15–0.40 Hz), and the total power spectral density (TP; <0.40 Hz) and LF/HF ratio were calculated. Results We found that ECP significantly increased the systolic and diastolic blood pressures in both stroke patients and controls. ECP decreased markedly the systolic and diastolic BPVs at VLF and LF and the TP, and the diastolic BPV at HF when compared with baseline. The decreases in diastolic and systolic BPV reached 37.56% and 23.20%, respectively, at VLF, 21.15% and 12.19% at LF, 8.76% and 16.59% at HF, and 31.92% and 23.62% for the total TP in stroke patients, which did not differ from those in healthy controls. The change in flow velocity on the contralateral side was positively correlated with the total TP systolic BPV change induced by ECP (r=0.312, p=0.035). Conclusions ECP reduces the beat-to-beat BPV when increasing the blood pressure and cerebral blood flow velocity in ischemic stroke patients. ECP might be able to improve the clinical outcome by decreasing the beat-to-beat BPV in stroke patients, and this should be explored further in future studies. PMID:27095525

  11. Characterization of Blood Flow in Capillaries by Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Wang, Tong; Xing, Zhongwen

    2011-03-01

    We presents a numerical investigation of the axisymmetric, pressure driven motion of single file erythrocyte (i.e., red blood cell) suspensions flowing in capillaries of diameter 8- 11 μ m. The governing Navier-Stokes equations are discretized using the operator splitting technique and solved by the finite element method. The study takes consideration the particulate nature of the blood. The red blood cell (RBC) is modeled as a closed membrane filled with a Newtonian fluid which has the same viscosity as the surrounding plasma. The cell membrane is described by a spring model so that the deformability of the cells can be considered. An immersed boundary method is also developed for dealing with the cell/fluid interaction in the flow. Our study successfully recreates several important in vivo hemodynamic and hemorheological properties of microscopic blood flow, such as parachute shape of the cells, blunt velocity profile, and the Fahraeus effect, and they have been shown to have strong dependence on cell deformability, hematocrit and vessel size.

  12. Precision and accuracy of clinical quantification of myocardial blood flow by dynamic PET: A technical perspective.

    PubMed

    Moody, Jonathan B; Lee, Benjamin C; Corbett, James R; Ficaro, Edward P; Murthy, Venkatesh L

    2015-10-01

    A number of exciting advances in PET/CT technology and improvements in methodology have recently converged to enhance the feasibility of routine clinical quantification of myocardial blood flow and flow reserve. Recent promising clinical results are pointing toward an important role for myocardial blood flow in the care of patients. Absolute blood flow quantification can be a powerful clinical tool, but its utility will depend on maintaining precision and accuracy in the face of numerous potential sources of methodological errors. Here we review recent data and highlight the impact of PET instrumentation, image reconstruction, and quantification methods, and we emphasize (82)Rb cardiac PET which currently has the widest clinical application. It will be apparent that more data are needed, particularly in relation to newer PET technologies, as well as clinical standardization of PET protocols and methods. We provide recommendations for the methodological factors considered here. At present, myocardial flow reserve appears to be remarkably robust to various methodological errors; however, with greater attention to and more detailed understanding of these sources of error, the clinical benefits of stress-only blood flow measurement may eventually be more fully realized. PMID:25868451

  13. Nanoparticle transport and binding dynamics in blood flow

    NASA Astrophysics Data System (ADS)

    Liu, Yaling; Tan, Jifu; Thomas, Antony

    2012-02-01

    Nanoparticulate systems have been widely used in diagnostic imaging and targeted therapeutic applications in recent years. Most current studies on nanoparticle drug delivery considered a Newtonian fluid with suspending spherical nanoparticles. However, blood is a complex biological fluid composed of deformable cells, proteins, platelets, and plasma. For blood flow in capillary, arterioles and venules, the particulate nature of the blood need to be considered in the delivery process. Non-Newtonian effects such as the cell-free-layer and nanoparticle-cell interaction will largely influence both the dispersion and binding rates, thus impact targeted delivery efficacy. A 3D multiscale particle-cell hybrid model is developed to model nanoparticle transport, dispersion, and adhesion dynamics in blood suspension. The motion and deformation of red blood cell is captured through Immersed Finite Element method. The motions and bindings of individual nanoparticles of various shapes are tracked through Brownian adhesion dynamics and molecular ligand-receptor binding kinetics. Nanoparticle dispersion and binding coefficients are derived from the developed model under various rheology conditions. The influences of vascular flow rate, geometry, nanoparticle size on nanoparticle distribution and delivery efficacy are characterized. A non-uniform nanoparticle distribution profile with higher particle concentration near the vessel wall is observed. Such distribution leads to 50% higher particle binding rate compared to the case without RBC considered. The tumbling motion of RBCs in the core region of the capillary is found to enhance nanoparticle dispersion. The modeled binding results are validated through designed experiments in microfluidic devices.

  14. PIV measurements of flow in a centrifugal blood pump: steady flow.

    PubMed

    Day, Steven W; McDaniel, James C

    2005-04-01

    Magnetically suspended left ventricular assist devices have only one moving part, the impeller. The impeller has absolutely no contact with any of the fixed parts, thus greatly reducing the regions of stagnant or high shear stress that surround a mechanical or fluid bearing. Measurements of the mean flow patterns as well as viscous and turbulent stresses were made in a shaft-driven prototype of a magnetically suspended centrifugal blood pump at several constant flow rates (3-9 L/min) using particle image velocimetry (PIV). The chosen range of flow rates is representative of the range over which the pump may operate while implanted. Measurements on a three-dimensional measurement grid within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser are reported. The measurements are used to identify regions of potential blood damage due to high shear stress and/or stagnation of the blood, both of which have been associated with blood damage within artificial heart valves and diaphragm-type pumps. Levels of turbulence intensity and Reynolds stresses that are comparable to those in artificial heart valves are reported. At the design flow rate (6 L/min), the flow is generally well behaved (no recirculation or stagnant flow) and stress levels are below levels that would be expected to contribute to hemolysis or thrombosis. The flow at both high (9 L/min) and low (3 L/min) flow rates introduces anomalies into the flow, such as recirculation, stagnation, and high stress regions. Levels of viscous and Reynolds shear stresses everywhere within the pump are below reported threshold values for damage to red cells over the entire range of flow rates investigated; however, at both high and low flow rate conditions, the flow field may promote activation of the clotting cascade due to regions of elevated shear stress adjacent to separated or stagnant flow. PMID:15971702

  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. Uterine blood flow indices, antinuclear autoantibodies and unexplained recurrent miscarriage

    PubMed Central

    Pietropolli, A.; Capogna, M. V.; Bernardini, S.; Piccione, E.; Ticconi, C.

    2015-01-01

    Objective To study the correlation between 2D and 3D uterine flow indexes and the presence or the absence of antinuclear antibodies (ANA) in women with unexplained recurrent miscarriage (uRM). Methods Fifty-two subjects (26 uRM and 26 control women) underwent 2D Doppler measurement of pulsatility index and resistance index of the uterine arteries in both the follicular and midluteal phase of the cycle. Additionally, 3D ultrasonography determination of vascularisation index, flow index, and vascularisation flow index was carried out with the aid of the VOCAL technique. Serum assay for the presence of ANA was performed in all women. Results Pulsatility index of ANA+ uRM women was higher than that of ANA- uRM women and control ANA+ and ANAwomen, both in the follicular and in the midluteal phase of the cycle. Vascularisation index in ANA- uRM women was significantly higher than that in ANA+ control women. Flow index in uRM ANA+ women was significantly lower than that of each of the other groups. Conclusion ANA might be involved in uRM by determining an impairment in uterine blood flow hemodynamic, particularly in uterine blood flow intensity and uterine artery impedance. PMID:26623408

  17. Volumetric lattice Boltzmann simulation for blood flow in aorta arteries

    NASA Astrophysics Data System (ADS)

    Deep, Debanjan; Yu, Huidan (Whitney); Teague, Shawn

    2012-11-01

    Complicated moving boundaries pose a major challenge in computational fluid dynamics for complex flows, especially in the biomechanics of both blood flow in the cardiovascular system and air flow in the respiratory system where the compliant nature of the vessels can have significant effects on the flow rate and wall shear stress. We develop a computation approach to treat arbitrarily moving boundaries using a volumetric representation of lattice Boltzmann method, which distributes fluid particles inside lattice cells. A volumetric bounce-back procedure is applied in the streaming step while momentum exchange between the fluid and moving solid boundary are accounted for in the collision sub-step. Additional boundary-induced migration is introduced to conserve fluid mass as the boundary moves across fluid cells. The volumetric LBM (VLBM) is used to simulate blood flow in both normal and dilated aorta arteries. We first compare flow structure and pressure distribution in steady state with results from Navier-Stokes based solver and good agreements are achieved. Then we focus on wall stress within the aorta for different heart pumping condition and present quantitative measurement of wall shear and normal stress.

  18. Spatial Temporal Image Correlation Spectroscopy (STICS) for Flow Analysis with Application for Blood Flow Mapping

    SciTech Connect

    Rossow, Molly; Gratton, Enrico; Mantulin, William M.

    2009-04-19

    It is important for surgeons to be able to measure blood flow in exposed arterioles during surgery. We report our progress in the development of an optical technique that will measure blood flow in surgically exposed blood vessels and enable previously difficult measurements. By monitoring optical fluctuations, the optical technique, based on Spatial Temporal Image Correlation (STICS), will directly measure the velocity of micron-scale particles--such as red blood cells. It will complement existing technology and provide qualitative measurements that were not previously possible. It relies on the concept that blood, when viewed on a small enough scale, is an inhomogeneous substance. Individual blood cells passing between a near-infrared light source and a detector will cause fluctuations in the transmitted optical signal. The speed, direction, and flow pattern of blood cells can be determined from these optical fluctuations. We present a series of computer simulations and experiments on phantom and animal systems to test this technique's ability to map complex flow patterns.

  19. Spatial Temporal Image Correlation Spectroscopy (STICS) for Flow Analysis with Application for Blood Flow Mapping (abstract)

    NASA Astrophysics Data System (ADS)

    Rossow, Molly; Mantulin, William M.; Gratton, Enrico

    2009-04-01

    It is important for surgeons to be able to measure blood flow in exposed arterioles during surgery. We report our progress in the development of an optical technique that will measure blood flow in surgically exposed blood vessels and enable previously difficult measurements. By monitoring optical fluctuations, the optical technique, based on Spatial Temporal Image Correlation (STICS), will directly measure the velocity of micron-scale particles-such as red blood cells. It will complement existing technology and provide qualitative measurements that were not previously possible. It relies on the concept that blood, when viewed on a small enough scale, is an inhomogeneous substance. Individual blood cells passing between a near-infrared light source and a detector will cause fluctuations in the transmitted optical signal. The speed, direction, and flow pattern of blood cells can be determined from these optical fluctuations. We present a series of computer simulations and experiments on phantom and animal systems to test this technique's ability to map complex flow patterns.

  20. Regional atrial blood flow in dogs. Effect of hypertrophy on coronary flow reserve.

    PubMed Central

    Bauman, R P; Rembert, J C; Greenfield, J C

    1989-01-01

    Little is known regarding regional atrial blood flow responses during varying hemodynamic states in both the normal and hypertrophied atria. This study was undertaken to develop a canine model of chronic atrial hypertrophy and to define in both this group and in normal dogs the regional blood flow response to acute atrial fibrillation and to measure coronary flow reserve. In the 12 dogs with atrial but not ventricular hypertrophy the mean left and right atrial weights were 75 and 47% respectively greater than in the normal group. Blood flow in the normal dogs was less in the appendage than in the non-appendage region for both atria and increased significantly during atrial fibrillation. Similar findings were noted in the hypertrophy group except that during control conditions the left atrial appendage flow was similar to the nonappendage flow. Minimal vascular resistance for the hypertrophy group, 39 +/- 3 was significantly (P less than 0.05) greater when compared to the normal group 28 +/- 2 mmHg/cm3 per min per g. Thus, significant regional blood flow differences occur in both the normal and hypertrophied atria. In addition, atrial hypertrophy does not alter the autoregulatory capacity to the hemodynamic stress of atrial fibrillation but does reduce coronary flow reserve. Images PMID:2523414

  1. Blood Flow: Multi-scale Modeling and Visualization

    SciTech Connect

    2010-01-01

    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 developing methods for multi-scale computations, techniques for multi-scale visualizations must be designed. This animation presents early results of joint efforts of teams from Brown University and Argonne National Laboratory to develop a multi-scale visualization methodology. It illustrates a flow of healthy (red) and diseased (blue) blood cells with a Dissipative Particle Dynamics (DPD) method. Each blood cell is represented by a mesh made of 500 DPD-particles, and small spheres show a sub-set of the DPD particles representing the blood plasma, while instantaneous streamlines and slices represent the ensemble average velocity. Credits: Science: Leopold Grinberg and George Karniadakis, Brown University Visualization: Joseph A. Insley and Michael E. Papka, Argonne National Laboratory This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357. This research was supported in part by the National Science Foundation through the PetaApps program and used TeraGrid resources provided by National Institute for Computational Sciences.

  2. Theoretical analysis of magnetic field interactions with aortic blood flow

    SciTech Connect

    Kinouchi, Y.; Yamaguchi, H.; Tenforde, T.S.

    1996-04-01

    The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.

  3. Effect of photodynamic therapy with verteporfin on tumor blood flow

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Pogue, Brian W.; Goodwin, Isak A.; O'Hara, Julia A.; Wilmot, Carmen M.; Hutchins, John E.; Hoopes, P. J.; Hasan, Tayyaba

    2003-06-01

    The success of photodynamic therapy with verteporfin is partially determined by the pharmacokinetic distribution of the sensitizer at the time of treatment. In this study tumor blood flow changes in the RIF-1 murine tumor model and tumor resopnse using the regrowth assay were measured, comparing two different intervals between drug and light administration. Blood flow measurements were taken with a laser Doppler system monitoring continuously over 1 hour and periodically up to 6 hours after treatment. Treatment after the longer interval caused significantly less flow decrease, to only 50% of the initial flow in 6 h. Hoechst staining of functional tumor vasculature confirmed the primary vascular damage and the decrease in tumor perfusion. The regrowth rate of tumors after the longer time interval, the regrowth rate was not signifincalty different from that of the control, indicating that only the 15-min interval group caused serious damage to the vascular bed of the tumor. These studies support the hypothesis that temporal pharmacokinetic changes in the photosensitizer distribution between the tumor parenchyma and blood vessels can significantly alter the mechanism of tumor targeting during therapy.

  4. Nuclear magnetic resonance and transcutaneous electromagnetic blood flow measurement.

    PubMed

    Battocletti, J H; Halbach, R E; Salles-Cunha, S X; Sances, A

    1983-09-01

    Static and alternating magnetic fields are employed in blood flowmeters using nuclear magnetic resonance (NMR) principles and electromagnetic induction by a moving conductor (TEM). Both techniques require high steady magnetic fields, obtained either from permanent magnets or from electromagnets. A relatively homogeneous magnetic field is needed for NMR, but, though important for calibration, homogeneity is not critical for TEM. NMR is more complex than TEM since it requires radio-frequency and audio-frequency magnetic fields. However, the TEM method requires surface electrodes in contact with the skin, or needle electrodes placed subcutaneously, whereas NMR is contactless. The NMR flowmeter can be calibrated directly, but appropriate and approximate models must be assumed and then solved by computer to quantify blood flow by the TEM flowmeter. Flow in individual vessels is measured a priori in the TEM flowmeter by virtue of the assumed models. To measure flow in individual vessels by NMR, a scanning or ranging method is required, which logically leads to blood flow imaging. The levels of steady, radio-frequency, and audio-frequency magnetic fields used in the two types of flowmeters are low enough so as not to cause any apparent stimulus to human volunteers and patients tested. PMID:6228667

  5. Thermoregulatory influences on common carotid blood flow in the dog.

    PubMed

    Baker, M A; Hawkins, M J; Rader, R D

    1982-05-01

    Common carotid blood flow (CCBF) and respiratory water loss (RWL) were measured in dogs resting at ambient temperatures between 25 and 50 degrees C, during hypothalamic heating, and during light and heavy exercise at ambient temperatures of 25 and 35 degrees C. In resting dogs, CCBF varied with the level of RWL. Elevations in CCBF and RWL occurred within seconds of each other during bursts of panting. Mean unilateral CCBF increased from 6.2 ml . min-1 . kg-1 at 25 degrees C to 16.8 ml . min-1 . kg-1 at 45 degrees C, in parallel with increasing RWL. Hypothalamic heating elicited simultaneous elevations in CCBF and RWL, and the level of CCBF was strongly correlated with the hypothalamic temperature. Both CCBF and RWL increased rapidly at the onset of exercise and continued to rise during a 15-min run. Highest rates of blood flow and evaporation occurred during heavy exercise at 35 degrees C. It is concluded that the rate of blood flow through the common carotid arteries in the dog is related to the thermoregulatory needs of the animal, and most of the increased flow occurring during heat stress is destined for evaporative surfaces of the nose, mouth, and tongue. PMID:7096136

  6. Blood Flow Imaging in Maternal and Fetal Arteries and Veins

    NASA Astrophysics Data System (ADS)

    Ricci, S.; Urban, G.; Vergani, P.; Paidas, M. J.; Tortoli, P.

    Maternal and fetal blood circulation has been investigated for nearly a decade through ultrasound (US) techniques. Evaluation of the spectrogram related to a single sample volume has been proven valuable for the assessment of fetal well-being and for prediction of pregnancy complications. In this work, an alternative technique, called Multigate Spectral Doppler Analysis (MSDA), is proposed. In this approach, 128 sample volumes aligned along the same scan line are simultaneously investigated to detect the blood velocity profile with high resolution. Profiles obtained through MSDA reveal features not detectable with the standard US technique, thus representing a more accurate flow signature. Some preliminary illustrative results are reported here.

  7. Margination of leukocytes in blood flow through small tubes.

    PubMed

    Goldsmith, H L; Spain, S

    1984-03-01

    Leukocyte margination in the vessels of the microcirculation has been attributed to a flow-dependent interaction with red cells. To determine the extent of this effect, experiments with human blood were done in 100- to 180-micron tubes to detect changes in cell distribution as a function of hematocrit and flow rate. Using a flow visualization technique, the leukocyte concentration distribution was determined in 45% ghost cell suspensions. Migration of cells toward the wall was observed at centerline velocities greater than 1 mm sec-1 and increased with increasing flow rate. The effect was probably due to a more rapid inward migration of ghosts than leukocytes because of fluid inertia and cell density differences. Experiments were therefore carried out in whole blood at hematocrits from 20 to 60%, measuring the number concentration of leukocytes and erythrocytes within the tube, nt, and comparing it to that in the infusing reservoir, no, (Fahraeus effect). At mean tube shear rates G less than 100 sec-1, nt/no less than 1 for both leukocytes and erythrocytes showing net migration of cells away from the wall, although at nearly all hematocrits there was an enrichment of leukocytes relative to erythrocytes in the tubes. At G less than 50 sec-1, nt/no remained less than 1 for erythrocytes but increased to greater than 1 for leukocytes showing migration toward the wall, the increase being greatest at 20% hematocrit in the 100-micron tubes. The nature of the effect was revealed by cine films which showed that, as the flow rate decreased, erythrocytes formed rouleaux which migrated inward creating a core and displacing leukocytes to the periphery. In control experiments using washed blood cells in phosphate buffer-albumin, nt/no less than 1 for both leukocytes and erythrocytes at all G and hematocrits, and leukocytes were now distributed. Cine films of washed blood confirmed that, in the absence of rouleaux, no significant inward migration of erythrocytes occurred. PMID

  8. Perturbation of red blood cell flow in small tubes by white blood cells.

    PubMed

    Thompson, T N; La Celle, P L; Cokelet, G R

    1989-02-01

    The flow of blood in the microcirculation is facilitated by the dynamic reduction in viscosity (Fahraeus-Lindquist effect) resulting from the axial flow of deforming erythrocytes (RBCs) and from the decrease in the ratio of cell to vessel diameter. RBC velocity exceeds that of average fluid velocity; however the slower moving white blood cells (WBC) perturb flow velocity and the ratio of cell to vessel diameter by obstructing red cell flow through formation of "trains" of red cells collecting behind the white cell. This effect of white cells was studied quantitatively in a model in vitro tubes less than 10 microns in diameter with the demonstration that flow resistance increases linearly with white cell numbers up to 1,000 WBC/mm3 at tube hematocrit of 17.7%. The increase in resistance exceeds the flow resistance of WBC and appears to relate directly to train formation. A mechanical model of train formation developed to predict WBC influence in flow resistance over the range of WBC studied reasonably fits observed WBC effects. PMID:2928089

  9. Effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants

    SciTech Connect

    Younkin, D.P.; Reivich, M.; Jaggi, J.L.; Obrist, W.D.; Delivoria-Papadopoulos, M.

    1987-06-01

    The effects of hematocrit and systolic blood pressure on cerebral blood flow were measured in 15 stable, low birth weight babies. CBF was measured with a modification of the xenon-133 (/sup 133/Xe) clearance technique, which uses an intravenous bolus of /sup 133/Xe, an external chest detector to estimate arterial /sup 133/Xe concentration, eight external cranial detectors to measure cephalic /sup 133/Xe clearance curves, and a two-compartmental analysis of the cephalic /sup 133/Xe clearance curves to estimate CBF. There was a significant inverse correlation between hematocrit and CBF, presumably due to alterations in arterial oxygen content and blood viscosity. Newborn CBF varied independently of systolic blood pressure between 60 and 84 mm Hg, suggesting an intact cerebrovascular autoregulatory mechanism. These results indicate that at least two of the factors that affect newborn animal CBF are operational in human newborns and may have important clinical implications.

  10. Endothelial-dependent vasodilators preferentially increase subendocardial blood flow

    SciTech Connect

    Pelc, L.R.; Gross, G.J.; Warltier, D.C.

    1986-03-05

    Interference with arachidonic acid metabolism on the effect of acetylcholine (Ach) or arachidonic acid (AA) to preferentially increase subendocardial perfusion was investigated in anesthetized dogs. Hemodynamics, regional myocardial blood flow (MBF (ml/min/g):radioactive microspheres) and the left ventricular transmural distribution of flow (endo/epi) were measured. Intracoronary infusion of Ach (10 ..mu..g/min) and AA (585 ..mu..g/min) significantly (P < .05*) increased myocardial perfusion and selectively redistributed flow to the subendocardium (increased endo/epi) without changes in systemic hemodynamics. Inhibition of phospholipase A/sub 2/ by quinacrine (Q; 600 ..mu..g/min, ic) attenuated the increase in myocardial perfusion produced by Ach but not by AA and inhibited the redistribution of flow to the subendocardium. The present results suggest that endothelium-dependent vasodilators produce a preferential increase in subendocardial perfusion via a product of AA metabolism.

  11. Quantitative cerebral blood flow with Optical Coherence Tomography

    PubMed Central

    Srinivasan, Vivek J.; Sakadžić, Sava; Gorczynska, Iwona; Ruvinskaya, Svetlana; Wu, Weicheng; Fujimoto, James G.; Boas, David A.

    2010-01-01

    Absolute measurements of cerebral blood flow (CBF) are an important endpoint in studies of cerebral pathophysiology. Currently no accepted method exists for in vivo longitudinal monitoring of CBF with high resolution in rats and mice. Using three-dimensional Doppler Optical Coherence Tomography and cranial window preparations, we present methods and algorithms for regional CBF measurements in the rat cortex. Towards this end, we develop and validate a quantitative statistical model to describe the effect of static tissue on velocity sensitivity. This model is used to design scanning protocols and algorithms for sensitive 3D flow measurements and angiography of the cortex. We also introduce a method of absolute flow calculation that does not require explicit knowledge of vessel angles. We show that OCT estimates of absolute CBF values in rats agree with prior measures by autoradiography, suggesting that Doppler OCT can perform absolute flow measurements in animal models. PMID:20174075

  12. Relations of blood pressure and head injury to regional cerebral blood flow.

    PubMed

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

    2016-06-15

    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=66.9years, 27.6% with a history of mild traumatic brain injury (mTBI) defined as a loss of consciousness ≤30min resulting from an injury to the head, and free of major medical (other than hypertension), neurological or psychiatric comorbidities. All engaged in clinical assessment of systolic and diastolic 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=0.024) and left dorsolateral (β=-2.61, p=0.042) prefrontal cortex, and left temporal cortex (β=-3.36, p=0.014); higher diastolic blood pressure was marginally associated with lower levels of perfusion in the left dorsolateral prefrontal cortex (β=-2.79, p=0.051). 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

  13. 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

  14. Modeling to link regional myocardial work, metabolism and blood flows

    PubMed Central

    Bassingthwaighte, James B.; Beard, Daniel A; Carlson, Brian E.; Dash, Ranjan K.; Vinnakota, Kalyan

    2012-01-01

    Given the mono-functional, highly coordinated processes of cardiac excitation and contraction, the observations that regional myocardial blood flows, rMBF, are broadly heterogeneous has provoked much attention, but a clear explanation has not emerged. In isolated and in vivo heart studies the total coronary flow is found to be proportional to the rate-pressure product (systolic mean blood pressure times heart rate), a measure of external cardiac work. The same relationship might be expected on a local basis: more work requires more flow. The validity of this expectation has never been demonstrated experimentally. In this article we review the concepts linking cellular excitation and contractile work to cellular energetics and ATP demand, substrate utilization, oxygen demand, vasoregulation, and local blood flow. Mathematical models of these processes are now rather well developed. We propose that the construction of an integrated model encompassing the biophysics, biochemistry and physiology of cardiomyocyte contraction, then combined with a detailed three-dimensional structuring of the fiber bundle and sheet arrangements of the heart as a whole will frame an hypothesis that can be quantitatively evaluated to settle the prime issue: Does local work drive local flow in a predictable fashion that explains the heterogeneity? While in one sense one can feel content that work drives flow is irrefutable, there are no cardiac contractile models that demonstrate the required heterogeneity in local strain-stress-work; quite the contrary, cardiac contraction models have tended toward trying to show that work should be uniform. The object of this review is to argue that uniformity of work does not occur, and is impossible in any case, and that further experimentation and analysis are necessary to test the hypothesis. PMID:22915334

  15. Impact of COPD exacerbation on cerebral blood flow.

    PubMed

    Yildiz, Sema; Kaya, Ihsan; Cece, Hasan; Gencer, Mehmet; Ziylan, Zeki; Yalcin, Funda; Turksoy, Ozlem

    2012-01-01

    We aimed to investigate the impact of chronic obstructive pulmonary disease (COPD) exacerbation on cerebral blood flow (CBF). In 21 COPD patients - in both exacerbation and stable phases -Doppler ultrasonographies of internal carotid artery (ICA) and vertebral artery (VA) were performed. There were significant differences in total, anterior and posterior CBF, ICA and VA flow volumes in exacerbated COPD compared to stable COPD. Total CBF was correlated with cross-sectional areas of left and right ICA, whereas independent predictor of total CBF was cross-sectional area of right ICA. Increased CBF might indicate cerebral autoregulation-mediated vasodilatation to overcome COPD exacerbation induced hypoxia. PMID:22542376

  16. 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.

  17. Subcutaneous blood flow in early male pattern baldness

    SciTech Connect

    Klemp, P.; Peters, K.; Hansted, B.

    1989-05-01

    The subcutaneous blood flow (SBF) was measured by the /sup 133/Xe washout method in the scalp of 14 patients with early male pattern baldness. Control experiments were performed in 14 normal haired men matched for age. The SBF in the scalp of the normal individuals was about 10 times higher than previously reported SBF values in other anatomical regions. In patients with early male pattern baldness, SBF was 2.6 times lower than the values found in the normal individuals (13.7 +/- 9.6 vs 35.7 +/- 10.5 ml/100 g/min-1). This difference was statistically significant (p much less than 0.001). A reduced nutritive blood flow to the hair follicles might be a significant event in the pathogenesis of early male pattern baldness.

  18. High speed optical holography of retinal blood flow.

    PubMed

    Pellizzari, M; Simonutti, M; Degardin, J; Sahel, J-A; Fink, M; Paques, M; Atlan, M

    2016-08-01

    We performed noninvasive video imaging of retinal blood flow in a pigmented rat by holographic interferometry of near-infrared laser light backscattered by retinal tissue, beating against an off-axis reference beam sampled at a frame rate of 39 kHz with a high throughput camera. Local Doppler contrasts emerged from the envelopes of short-time Fourier transforms and the phase of autocorrelation functions of holograms rendered by Fresnel transformation. This approach permitted imaging of blood flow in large retinal vessels (∼30 microns diameter) over 400×400  pixels with a spatial resolution of ∼8 microns and a temporal resolution of ∼6.5  ms. PMID:27472604

  19. Frontiers in optical imaging of cerebral blood flow and metabolism

    PubMed Central

    Devor, Anna; Sakadžić, Sava; Srinivasan, Vivek J; Yaseen, Mohammad A; Nizar, Krystal; Saisan, Payam A; Tian, Peifang; Dale, Anders M; Vinogradov, Sergei A; Franceschini, Maria Angela; Boas, David A

    2012-01-01

    In vivo optical imaging of cerebral blood flow (CBF) and metabolism did not exist 50 years ago. While point optical fluorescence and absorption measurements of cellular metabolism and hemoglobin concentrations had already been introduced by then, point blood flow measurements appeared only 40 years ago. The advent of digital cameras has significantly advanced two-dimensional optical imaging of neuronal, metabolic, vascular, and hemodynamic signals. More recently, advanced laser sources have enabled a variety of novel three-dimensional high-spatial-resolution imaging approaches. Combined, as we discuss here, these methods are permitting a multifaceted investigation of the local regulation of CBF and metabolism with unprecedented spatial and temporal resolution. Through multimodal combination of these optical techniques with genetic methods of encoding optical reporter and actuator proteins, the future is bright for solving the mysteries of neurometabolic and neurovascular coupling and translating them to clinical utility. PMID:22252238

  20. Strongly Accelerated Margination of Active Particles in Blood Flow.

    PubMed

    Gekle, Stephan

    2016-01-19

    Synthetic nanoparticles and other stiff objects injected into a blood vessel filled with red blood cells are known to marginate toward the vessel walls. By means of hydrodynamic lattice-Boltzmann simulations, we show that active particles can strongly accelerate their margination by moving against the flow direction: particles located initially in the channel center migrate much faster to their final position near the wall than in the nonactive case. We explain our findings by an enhanced rate of collisions between the stiff particles and the deformable red blood cells. Our results imply that a significantly faster margination can be achieved either technically by the application of an external magnetic field (if the particles are magnetic) or biologically by self-propulsion (if the particles are, e.g., swimming bacteria). PMID:26789773

  1. Generating new blood flow: integrating developmental biology and tissue engineering.

    PubMed

    Krenning, Guido; Moonen, Jan-Renier A J; van Luyn, Marja J A; Harmsen, Martin C

    2008-11-01

    Vascular tissue engineering aims to restore blood flow by seeding artificial tubular scaffolds with endothelial and smooth muscle cells, thus creating bioartificial blood vessels. Herein, the progenitors of smooth muscle and endothelial cells hold great promise because they efficiently differentiate and harbor longevity. In this review, we describe a novel tissue engineering approach that uses current insights from developmental biology, that is, progenitor cell plasticity, and the latest advances in biomaterial design. We focus specifically on developmental processes that regulate progenitor cell (trans)differentiation and offer a platform for the integration of these molecular clues into biomaterial design. We propose a novel engineering paradigm for the creation of a small-diameter blood vessel wherein progenitor cell differentiation and tissue organization are instructed by the biomaterial solely. With this review, we emphasize the power of integrating developmental biology and material science for vascular tissue engineering. PMID:19345319

  2. Blood viscosity in tube flow: dependence on diameter and hematocrit.

    PubMed

    Pries, A R; Neuhaus, D; Gaehtgens, P

    1992-12-01

    Since the original publications by Martini et al. (Dtsch. Arch. Klin. Med. 169: 212-222, 1930) and Fahraeus and Lindqvist (Am. J. Physiol. 96: 562-568, 1931), it has been known that the relative apparent viscosity of blood in tube flow depends on tube diameter. Quantitative descriptions of this effect and of the dependence of blood viscosity on hematocrit in the different diameter tubes are required for the development of hydrodynamic models of blood flow through the microcirculation. The present study provides a comprehensive data base for the description of relative apparent blood viscosity as a function of tube diameter and hematocrit. Data available from the literature are compiled, and new experimental data obtained in a capillary viscometer are presented. The combined data base comprises measurements at high shear rates (u > or = 50 s-1) in tubes with diameters ranging from 3.3 to 1,978 microns at hematocrits of up to 0.9. If corrected for differences in suspending medium viscosity and temperature, the data show remarkable agreement. Empirical fitting equations predicting relative apparent blood viscosity from tube diameter and hematocrit are presented. A pronounced change in the hematocrit dependence of relative viscosity is observed in a range of tube diameters in which viscosity is minimal. While a linear hematocrit-viscosity relationship is found in tubes of < or = 6 microns, an overproportional increase of viscosity with hematocrit prevails in tubes of > or = 9 microns. This is interpreted to reflect the hematocrit-dependent transition from single- to multifile arrangement of cells in flow. PMID:1481902

  3. Ultrasonic Doppler measurement of renal artery blood flow

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    An extensive evaluation of the practical and theoretical limitations encountered in the use of totally implantable CW Doppler flowmeters is provided. Theoretical analyses, computer models, in-vitro and in-vivo calibration studies describe the sources and magnitudes of potential errors in the measurement of blood flow through the renal artery, as well as larger vessels in the circulatory system. The evaluation of new flowmeter/transducer systems and their use in physiological investigations is reported.

  4. 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).

  5. Multiple medullary venous malformations decreasing cerebral blood flow: Case report

    SciTech Connect

    Tomura, N.; Inugami, A.; Uemura, K.; Hadeishi, H.; Yasui, N. )

    1991-02-01

    A rare case of multiple medullary venous malformations in the right cerebral hemisphere is reported. The literature review yielded only one case of multiple medullary venous malformations. Computed tomography scan showed multiple calcified lesions with linear contrast enhancement representing abnormal dilated vessels and mild atrophic change of the right cerebral hemisphere. Single-photon emission computed tomography using N-isopropyl-p-({sup 123}I) iodoamphetamine demonstrated decreased cerebral blood flow in the right cerebral hemisphere.

  6. Influence of prostatic blood flow on laser prostatectomy

    NASA Astrophysics Data System (ADS)

    van Swol, Christiaan F. P.; Verdaasdonck, Rudolf M.; Mooibroek, Jaap; Boon, Tom A.

    1994-05-01

    Normally, a laser prostatectomy to treat Benign Prostatic Hyperplasia is performed using a fixed dosimetry. Differences in, e.g., blood flow, optical properties and geometry, are not taken into account, although most of these differences may be distinguished when performing a cystoscopy, e.g., the color of the prostate. These characteristics show their influence in the final tissue effect. We developed a model to predict the permanent damage to the tissue.

  7. Feasibility of patient specific aortic blood flow CFD simulation.

    PubMed

    Svensson, Johan; Gårdhagen, Roland; Heiberg, Einar; Ebbers, Tino; Loyd, Dan; Länne, Toste; Karlsson, Matts

    2006-01-01

    Patient specific modelling of the blood flow through the human aorta is performed using computational fluid dynamics (CFD) and magnetic resonance imaging (MRI). Velocity patterns are compared between computer simulations and measurements. The workflow includes several steps: MRI measurement to obtain both geometry and velocity, an automatic levelset segmentation followed by meshing of the geometrical model and CFD setup to perform the simulations follwed by the actual simulations. The computational results agree well with the measured data. PMID:17354898

  8. Modeling study of terminal transients of blood flow

    NASA Astrophysics Data System (ADS)

    Stiukhina, Elena S.; Postnov, Dmitry E.

    2016-04-01

    In spite of growing body of experimental and theoretical results on blood flow (BF) patterns under the continuously sustained circulation, much less is known about BF dynamics under the exceptional, but still important cases of venous or arterial occlusion used in medical probes. Since these conditions finally lead to complete or nearly complete stop of red blood cells (RBC) motion, we term it as TTBF, being the Terminal Transients of Blood Flow. An extreme case of such transients is the ultimate extinction of BF after the stopping of heart contractions, during which it is governed by gravitation, some vascular-originated propulsion mechanisms, and, possibly, by RBC aggregation. Quite little is known about this process, while reports the detectable post-mortal motion of mice RBC during at least 2 hours. In our work we present the modeling study of TTBF patterns due to gravitational forces. We present the minimalistic model configuration of vasculature in order to simulate what happens immediately after the pumping of blood has been stopped. Our main findings are concerned to reversal of arterial BF, as well as to duration and non-monotonicity of transients.

  9. Transient Aortic Occlusion Augments Collateral Blood Flow and Reduces Mortality During Severe Ischemia due to Proximal Middle Cerebral Artery Occlusion.

    PubMed

    Ramakrishnan, Gomathi; Dong, Bin; Todd, Kathryn G; Shuaib, Ashfaq; Winship, Ian R

    2016-04-01

    Cerebral collateral circulation provides alternative vascular routes for blood to reach ischemic tissues during stroke. Collateral therapeutics attempt to augment flow through these collateral channels to reduce ischemia and brain damage during acute ischemic stroke. Transient aortic occlusion (TAO) has pre-clinical data suggesting that it can augment collateral blood flow and clinical data suggesting a benefit for patients with moderate cortical strokes. By diverting blood from the periphery towards the cerebral circulation, TAO has the potential to augment primary collateral flow at the circle of Willis and thereby improve outcome even during large, hemispheric strokes. Using proximal middle and anterior cerebral artery occlusion in rats, we demonstrate that TAO reduces mortality and improves collateral blood flow in severely ischemic animals. As such, TAO may be an effective therapy to reduce early mortality during severe ischemia associated with proximal occlusions. PMID:26706246

  10. Cerebral blood flow is reduced in patients with sepsis syndrome

    SciTech Connect

    Bowton, D.L.; Bertels, N.H.; Prough, D.S.; Stump, D.A.

    1989-05-01

    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, the 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.

  11. 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.

  12. Role of phorbol esters in regional cerebral blood flow regulation

    SciTech Connect

    Hanley, D.F.; Uhl, G.R.; Miyabe, M.; Traystman, R.J.

    1986-03-05

    Phorbol esters are known to activate protein kinase C, an intracellular enzyme capable of phosphorylating membrane associated receptors. By using phorbol-12-13-dibutyrate (PDBU), they investigated the presence and function of protein kinase C on canine cerebral vessels. In vitro tissue autoradiographic studies performed on 8 ..mu.. sections of canine cerebral vessels with H/sup 3/-PDBU revealed a 3 to 1 ratio of specific to nonspecific binding. Competitive displacement was demonstrated for 3 physiologically active phorbol esters but could not be demonstrated for 3 physiologically inactive phorbol derivatives. The effect of PDBU on regional cerebral blood flow (rCBF) was then studied in vivo using radiolabelled microspheres in 6 dogs. Measurements were made during control ventriculocisternal CSF infusions and 5,10,15,20 and 25 minutes after infusion of .1 nM/min PDBU. For grey matter regions in contact with the perfusate, caudate nucleus, cortical watershed and cerebellum, blood flow increased from 33 +/- 6 to 45 +/- 7, 20 +/- 2 to 27 +/- 2, and 31 +/- 2 to 42 +/- 5 ml/min/100 gm, respectively. rCBF was unchanged for brainstem, temporal lobe or white matter regions. They conclude (1) PDBU has high affinity binding to canine cerebral vascular smooth muscle, and (2) PDBU produces an increase in rCBF when delivered intraventricularly. These data suggest a possible role for protein kinase C in the regulation of cerebral blood flow.

  13. Blood flow distribution with adrenergic and histaminergic antagonists

    SciTech Connect

    Baker, C.H.; Davis, D.L.; Sutton, E.T.

    1989-03-01

    Superficial fibular nerve stimulation (SFNS) causes increased pre- and post-capillary resistances as well as increased capillary permeability in the dog hind paw. These responses indicate possible adrenergic and histaminergic interactions. The distribution of blood flow between capillaries and arteriovenous anastomoses (AVA) may depend on the relative effects of these neural inputs. Right hind paws of anesthetized heparinized dogs were vascularly and neurally isolated and perfused with controlled pressure. Blood flow distribution was calculated from the venous recovery of 85Sr-labeled microspheres (15 microns). The mean transit times of 131I-albumin and 85Sr-labeled microspheres were calculated. The effects of adrenergic and histaminergic antagonists with and without SFNS were determined. Phentolamine blocked the entire response to SFNS. Prazosin attenuated increases in total and AVA resistance. Yohimbine prevented increased total resistance, attenuated the AVA resistance increase, and revealed a decrease in capillary circuit resistance. Pyrilamine attenuated total resistance increase while SFNS increased capillary and AVA resistances. Metiamide had no effect on blood flow distribution with SFNS. The increase in AVA resistance with SFNS apparently resulted from a combination of alpha 1 and alpha 2 receptor stimulation but not histaminergic effects.

  14. Neoterminal ileal blood flow after ileocolonic resection for Crohn's disease.

    PubMed Central

    Angerson, W J; Allison, M C; Baxter, J N; Russell, R I

    1993-01-01

    Endoscopic laser Doppler flowmetry was used to measure neoterminal ileal blood flow in 16 patients who had undergone ileocolonic resection for Crohn's disease and had since remained clinically and biochemically free of disease, and eight control patients who had undergone similar surgery for colonic carcinoma. Four patients with clinically active Crohn's disease of the terminal ileum were also studied. Neoterminal ileal recurrence in those with inactive Crohn's disease was graded endoscopically. The median and minimum of five local blood flow measurements performed in each patient were inversely correlated with the endoscopic recurrence grade (r = -0.52, p = 0.04 and r = -0.63, p = 0.01 respectively). Relative to the control group, median blood flow was non-significantly lower in the inactive Crohn's disease group as a whole (p > 0.05) but was significantly reduced in patients with active disease (p = 0.02). A progressive reduction in tissue perfusion may accompany recurrence of Crohn's disease while at a subclinical stage. PMID:8244138

  15. Improvement in blood fluidity by Kaempferia parviflora rhizome.

    PubMed

    Murata, Kazuya; Deguchi, Takahiro; Fujita, Takanori; Matsuda, Hideaki

    2013-10-01

    Improvement in blood fluidity leads to the prevention of various lifestyle-related diseases. A raw material for improving blood fluidity has been long desired in the research area of functional and supplemental foods. We successfully showed an improvement in blood fluidity by the Zingiberaceae plant, Kaempferia parviflora. The rhizome of the plant reduced the blood passage time through a micro slit using a disseminated intravascular coagulation model. The mechanism was attributed to the activation of fibrinolysis, as demonstrated by elongation of the euglobulin lysis time and an in-vitro fibrinolysis assay. The active principles were determined to be methoxyflavones. The results show that the rhizome of K. parviflora is a promising candidate preventive agent for treating lifestyle-related diseases. PMID:23212284

  16. [A multichannel telemetry system for autonomic neural signals, blood flow velocity, blood pressure, and ECG measurements].

    PubMed

    Yonezawa, Y; Takenoshita, M; Ninomiya, I

    1992-01-01

    A radio multichannel telemetry system has been developed for use with chronically instrumented, unrestrained, small animals. The system can simultaneously record autonomic neural signals, blood flow velocity, blood pressure, and ECG. The system is time-multiplexed and pulse width modulation (PWM)/FM device, which employs two sampling frequencies. The system is designed with 10 standard low power integrated circuits, a 3 terminal voltage regulator, and a transistor. The size is 53 x 42 x 20 mm, and the weight, including two batteries is 40 grams. The system is powered by two lithium cells, which provide 60 hours of continuous operation. PMID:1494988

  17. Synchrotron microimaging technique for measuring the velocity fields of real blood flows

    SciTech Connect

    Lee, Sang-Joon; Kim, Guk Bae

    2005-03-15

    Angiography and Doppler methods used for diagnosing vascular diseases give information on the shape of blood vessels and pointwise blood speed but do not provide detailed information on the flow fields inside the blood vessels. In this study, we developed a method for visualizing blood flow by using coherent synchrotron x rays. This method, which does not require the addition of any contrast agent or tracer particles, visualizes the flow pattern of blood by enhancing the diffraction and interference characteristics of the blood cells. This was achieved by optimizing the sample- (blood) to-detector (charge-coupled device camera) distance and the sample thickness. The proposed method was used to extract quantitative velocity field information from blood flowing inside an opaque microchannel by applying a two-frame particle image velocimetry algorithm to enhanced x-ray images of the blood flow. The measured velocity field data showed a flow structure typical of flow in a macrochannel.

  18. Improving Ecological Response Monitoring of Environmental Flows

    NASA Astrophysics Data System (ADS)

    King, Alison J.; Gawne, Ben; Beesley, Leah; Koehn, John D.; Nielsen, Daryl L.; Price, Amina

    2015-05-01

    Environmental flows are now an important restoration technique in flow-degraded rivers, and with the increasing public scrutiny of their effectiveness and value, the importance of undertaking scientifically robust monitoring is now even more critical. Many existing environmental flow monitoring programs have poorly defined objectives, nonjustified indicator choices, weak experimental designs, poor statistical strength, and often focus on outcomes from a single event. These negative attributes make them difficult to learn from. We provide practical recommendations that aim to improve the performance, scientific robustness, and defensibility of environmental flow monitoring programs. We draw on the literature and knowledge gained from working with stakeholders and managers to design, implement, and monitor a range of environmental flow types. We recommend that (1) environmental flow monitoring programs should be implemented within an adaptive management framework; (2) objectives of environmental flow programs should be well defined, attainable, and based on an agreed conceptual understanding of the system; (3) program and intervention targets should be attainable, measurable, and inform program objectives; (4) intervention monitoring programs should improve our understanding of flow-ecological responses and related conceptual models; (5) indicator selection should be based on conceptual models, objectives, and prioritization approaches; (6) appropriate monitoring designs and statistical tools should be used to measure and determine ecological response; (7) responses should be measured within timeframes that are relevant to the indicator(s); (8) watering events should be treated as replicates of a larger experiment; (9) environmental flow outcomes should be reported using a standard suite of metadata. Incorporating these attributes into future monitoring programs should ensure their outcomes are transferable and measured with high scientific credibility.

  19. Pediatric Sports-Related Concussion Produces Cerebral Blood Flow Alterations

    PubMed Central

    Farley, Chad; Altaye, Mekibib; Leach, James; Cecil, Kim M.

    2012-01-01

    Objectives: The pathophysiology of sports-related concussion (SRC) is incompletely understood. Human adult and experimental animal investigations have revealed structural axonal injuries, decreases in the neuronal metabolite N-acetyl aspartate, and reduced cerebral blood flow (CBF) after SRC and minor traumatic brain injury. The authors of this investigation explore these possibilities after pediatric SRC. Patients And Methods: Twelve children, ages 11 to 15 years, who experienced SRC were evaluated by ImPACT neurocognitive testing, T1 and susceptibility weighted MRI, diffusion tensor imaging, proton magnetic resonance spectroscopy, and phase contrast angiography at <72 hours, 14 days, and 30 days or greater after concussion. A similar number of age- and gender-matched controls were evaluated at a single time point. Results: ImPACT results confirmed statistically significant differences in initial total symptom score and reaction time between the SRC and control groups, resolving by 14 days for total symptom score and 30 days for reaction time. No evidence of structural injury was found on qualitative review of MRI. No decreases in neuronal metabolite N-acetyl aspartate or elevation of lactic acid were detected by proton magnetic resonance spectroscopy. Statistically significant alterations in CBF were documented in the SRC group, with reduction in CBF predominating (38 vs 48 mL/100 g per minute; P = .027). Improvement toward control values occurred in only 27% of the participants at 14 days and 64% at >30 days after SRC. Conclusions: Pediatric SRC is primarily a physiologic injury, affecting CBF significantly without evidence of measurable structural, metabolic neuronal or axonal injury. Further study of CBF mechanisms is needed to explain patterns of recovery. PMID:22129537

  20. The Impact of Increased Bladder Blood Flow on Storage Symptoms after Holmium Laser Enucleation of the Prostate.

    PubMed

    Saito, Keisuke; Hisasue, Shin-ichi; Ide, Hisamitsu; Aoki, Hiroaki; Muto, Satoru; Yamaguchi, Raizo; Tsujimura, Akira; Horie, Shigeo

    2015-01-01

    In order to investigate how holmium laser enucleation of the prostate (HoLEP) improves urinary storage symptoms, we assessed blood flow in the urinary bladder mucosa of patients with benign prostatic hyperplasia (BPH) before and after laser surgery. Seventy-four consecutive patients with BPH (median age 69 years, range; 53-88) underwent HoLEP at our institution and are included in this study. We prospectively assessed the International Prostate Symptom Score (IPSS), IPSS-QOL Score, the Overactive Bladder Symptom Score (OABSS), uroflowmetry, and blood flow in the urinary bladder, before and after surgery. Blood flow in the bladder mucosa was measured using the OMEGA FLOW (OMEGAWAVE, Tokyo, Japan) laser Doppler flowmeter. The median volume of the enucleated adenomas was 45.0 g (range: 25.0 to 83.2). The median IPSS improved significantly from 20 (range: 6-35) to 3 (0-22) (p < 0.001; Wilcoxon signed-rank test), as did the storage symptoms score, which decreased from 13 (2-20) to 3 (1-8) (p < 0.001). Median bladder blood flow increased at the trigone from 9.57 ± 0.83 ml/sec to 17.60 ± 1.08 ml/sec. Multiple regression analysis for the improved storage symptom score eliminated all explanatory variables except increased bladder perfusion. The data suggest that HoLEP improves blood flow in the bladder mucosa, which independently leads to the improvement of storage symptoms. PMID:26090819

  1. The Impact of Increased Bladder Blood Flow on Storage Symptoms after Holmium Laser Enucleation of the Prostate

    PubMed Central

    Ide, Hisamitsu; Aoki, Hiroaki; Muto, Satoru; Yamaguchi, Raizo; Tsujimura, Akira; Horie, Shigeo

    2015-01-01

    In order to investigate how holmium laser enucleation of the prostate (HoLEP) improves urinary storage symptoms, we assessed blood flow in the urinary bladder mucosa of patients with benign prostatic hyperplasia (BPH) before and after laser surgery. Seventy-four consecutive patients with BPH (median age 69 years, range; 53–88) underwent HoLEP at our institution and are included in this study. We prospectively assessed the International Prostate Symptom Score (IPSS), IPSS-QOL Score, the Overactive Bladder Symptom Score (OABSS), uroflowmetry, and blood flow in the urinary bladder, before and after surgery. Blood flow in the bladder mucosa was measured using the OMEGA FLOW (OMEGAWAVE, Tokyo, Japan) laser Doppler flowmeter. The median volume of the enucleated adenomas was 45.0 g (range: 25.0 to 83.2). The median IPSS improved significantly from 20 (range: 6–35) to 3 (0–22) (p<0.001; Wilcoxon signed-rank test), as did the storage symptoms score, which decreased from 13 (2–20) to 3 (1–8) (p<0.001). Median bladder blood flow increased at the trigone from 9.57±0.83 ml/sec to 17.60±1.08 ml/sec. Multiple regression analysis for the improved storage symptom score eliminated all explanatory variables except increased bladder perfusion. The data suggest that HoLEP improves blood flow in the bladder mucosa, which independently leads to the improvement of storage symptoms. PMID:26090819

  2. PIV measurements of flow in a centrifugal blood pump: time-varying flow.

    PubMed

    Day, Steven W; McDaniel, James C

    2005-04-01

    Measurements of the time-varying flow in a centrifugal blood pump operating as a left ventricular assist device (LVAD) are presented. This includes changes in both the pump flow rate as a function of the left ventricle contraction and the interaction of the rotating impeller and fixed exit volute. When operating with a pulsing ventricle, the flow rate through the LVAD varies from 0-11 L/min during each cycle of the heartbeat. Phase-averaged measurements of mean velocity and some turbulence statistics within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser, are reported at 20 phases of the cardiac cycle. The transient flow fields are compared to the constant flow rate condition that was reported previously in order to investigate the transient effects within the pump. It is shown that the quasi-steady assumption is a fair treatment of the time varying flow field in all regions of this representative pump, which greatly simplifies the comprehension and modeling of this flow field. The measurements are further interpreted to identify the effects that the transient nature of the flow field will have on blood damage. Although regions of recirculation and stagnant flow exist at some phases of the cardiac cycle, there is no location where flow is stagnant during the entire heartbeat. PMID:15971703

  3. Intercostal muscle blood flow limitation in athletes during maximal exercise

    PubMed Central

    Vogiatzis, Ioannis; Athanasopoulos, Dimitris; Habazettl, Helmut; Kuebler, Wolfgang M; Wagner, Harrieth; Roussos, Charis; Wagner, Peter D; Zakynthinos, Spyros

    2009-01-01

    We investigated whether, during maximal exercise, intercostal muscle blood flow is as high as during resting hyperpnoea at the same work of breathing. We hypothesized that during exercise, intercostal muscle blood flow would be limited by competition from the locomotor muscles. Intercostal (probe over the 7th intercostal space) and vastus lateralis muscle perfusion were measured simultaneously in ten trained cyclists by near-infrared spectroscopy using indocyanine green dye. Measurements were made at several exercise intensities up to maximal (WRmax) and subsequently during resting isocapnic hyperpnoea at minute ventilation levels up to those at WRmax. During resting hyperpnoea, intercostal muscle blood flow increased linearly with the work of breathing (R2= 0.94) to 73.0 ± 8.8 ml min−1 (100 g)−1 at the ventilation seen at WRmax (work of breathing ∼550–600 J min−1), but during exercise it peaked at 80% WRmax (53.4 ± 10.3 ml min−1 (100 g)−1), significantly falling to 24.7 ± 5.3 ml min−1 (100 g)−1 at WRmax. At maximal ventilation intercostal muscle vascular conductance was significantly lower during exercise (0.22 ± 0.05 ml min−1 (100 g)−1 mmHg−1) compared to isocapnic hyperpnoea (0.77 ± 0.13 ml min−1 (100 g)−1 mmHg−1). During exercise, both cardiac output and vastus lateralis muscle blood flow also plateaued at about 80% WRmax (the latter at 95.4 ± 11.8 ml min−1 (100 g)−1). In conclusion, during exercise above 80% WRmax in trained subjects, intercostal muscle blood flow and vascular conductance are less than during resting hyperpnoea at the same minute ventilation. This suggests that the circulatory system is unable to meet the demands of both locomotor and intercostal muscles during heavy exercise, requiring greater O2 extraction and likely contributing to respiratory muscle fatigue. PMID:19451206

  4. Reduced blood flow to contracting skeletal muscle in ageing humans: is it all an effect of sand through the hourglass?

    PubMed

    Nyberg, Michael; Hellsten, Ylva

    2016-04-15

    The ability to sustain a given absolute submaximal workload declines with advancing age, likely to be due to a lower level of blood flow and O2 delivery to the exercising muscles. Given that physical inactivity mimics many of the physiological changes associated with ageing, separating the physiological consequences of ageing and physical inactivity can be challenging; yet, observations from cross-sectional and longitudinal studies on the effects of physical activity have provided some insight. Physical activity has the potential to offset the age-related decline in blood flow to contracting skeletal muscle during exercise where systemic blood flow is not limited by cardiac output, thereby improving O2 delivery and allowing for an enhanced energy production from oxidative metabolism. The mechanisms underlying the increase in blood flow with regular physical activity include improved endothelial function and the ability for functional sympatholysis - an attenuation of the vasoconstrictor effect of sympathetic nervous activity. These vascular adaptations with physical activity are likely to be an effect of improved nitric oxide and ATP signalling. Collectively, precise matching of blood flow and O2 delivery to meet the O2 demand of the active skeletal muscle of aged individuals during conditions where systemic blood flow is not limited by cardiac output seems to a large extent to be related to the level of physical activity. PMID:26095873

  5. Improved modeling techniques for turbomachinery flow fields

    SciTech Connect

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-12-31

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbomachinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. This will be accomplished in a cooperative program by Penn State University and the Allison Engine Company. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tenor.

  6. CEOs say patient deposits improve cash flow.

    PubMed

    Anderson, H J

    1991-02-20

    CEOs say it makes good business sense to require patients to make cash deposits toward their bills prior to admission, because improved cash flow is vital to financially strapped hospitals. But hospitals that require cash deposits should also be aware of the sensitive public relations issues involved, experts caution. PMID:1993531

  7. Pulsed Doppler: determination of diameter, blood flow velocity, and volumic flow of brachial artery in man.

    PubMed

    Levenson, J A; Peronneau, P A; Simon, A; Safar, M E

    1981-03-01

    A pulsed Doppler velocimeter suitable for the determination of blood flow velocity and volumic flow in peripheral arteries is described. The apparatus has two main characteristics: an adjustable range-gated time system and a double transducer probe. The error in the determination of the angle between the ultrasound beam and flow of blood with this apparatus was less than 2%, and overestimation of the arterial diameter due to the sample volume size did not exceed 0.035 +/- 0.015 cm. The apparatus was used to determine diameter, blood flow velocity and volumic flow of the brachial artery of 22 healthy men. The values were respectively 0.440 +/- 0.010 cm, 9.15 +/- 1.01 cm.s-1 and 85 +/- 10 cm3.min-1. Administration of intravenous nitroglycerin significantly increased the arterial diameter (p less than 0.001) without any significant change in volumic flow. The described pulsed Doppler velocimeter provides an accurate noninvasive method for determining volumic flow in peripheral arteries in clinical investigation and cardiovascular pharmacology. PMID:6455197

  8. 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

  9. 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

  10. 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.

  11. Experimental Arrest of Cerebral Blood Flow in Human Subjects

    PubMed Central

    Smith, Brian A.; Clayton, Ellen Wright; Robertson, David

    2013-01-01

    Loss of consciousness in pilots during rapid ascent after bombing missions was a major problem in World War II, and experiments were undertaken to study the cause of this phenomenon. Postulating impaired cerebral blood flow as a likely mechanism, the investigators developed a neck device, the KRA Cuff, which when inflated could shut off blood supply to the brain. With cessation of blood flow for up to 100 seconds, the investigators observed a sequence of responses, including unconsciousness, followed by dilated pupils, tonic/clonic movements, loss of bladder and eventually bowel control, and appearance of pathological reflexes. This study, carried out in prisoners and patients with schizophrenia in 1941–42, largely disappeared from public discourse for a number of years. It has received occasional attention subsequently and been considered controversial. Recently discovered records, including extensive written and photographic data from the studies, shed new light on the methods and motives of the research team. We describe here this new information and its implications for the scientific and ethical assessment of the study. PMID:21532128

  12. Ion channel networks in the control of cerebral blood flow.

    PubMed

    Longden, Thomas A; Hill-Eubanks, David C; Nelson, Mark T

    2016-03-01

    One hundred and twenty five years ago, Roy and Sherrington made the seminal observation that neuronal stimulation evokes an increase in cerebral blood flow.(1) Since this discovery, researchers have attempted to uncover how the cells of the neurovascular unit-neurons, astrocytes, vascular smooth muscle cells, vascular endothelial cells and pericytes-coordinate their activity to control this phenomenon. Recent work has revealed that ionic fluxes through a diverse array of ion channel species allow the cells of the neurovascular unit to engage in multicellular signaling processes that dictate local hemodynamics.In this review we center our discussion on two major themes: (1) the roles of ion channels in the dynamic modulation of parenchymal arteriole smooth muscle membrane potential, which is central to the control of arteriolar diameter and therefore must be harnessed to permit changes in downstream cerebral blood flow, and (2) the striking similarities in the ion channel complements employed in astrocytic endfeet and endothelial cells, enabling dual control of smooth muscle from either side of the blood-brain barrier. We conclude with a discussion of the emerging roles of pericyte and capillary endothelial cell ion channels in neurovascular coupling, which will provide fertile ground for future breakthroughs in the field. PMID:26661232

  13. Structured Tree Outflow Condition for Blood Flow in Arteries

    NASA Astrophysics Data System (ADS)

    Olufsen, Mette

    1998-11-01

    Modeling blood flow and especially propagation of the pulse wave in the systemic arteries is of interests to the medical society because of the significance of the dicrotic wave. The pulse wave propagating along the larger arteries is reflected because of tapering and branching of the vessels, as well as the peripheral resistance, which is mainly stemming from the smaller arteries and arterioles. In order to avoid artificial reflections it is important to determine a boundary condition, representing the smaller arteries and arterioles, which is physiologically correct. In this work we have proposed a boundary condition based on a structured tree model. The result will be compared both with other modeling approaches as well as with results from measurements of flow and pressure at a number of locations along the larger arteries. The model for the larger arteries is based on the axisymmetrical Navier Stokes equations where the blood is assumed Newtonian and incompressible and the vessels are tapering. In the structured tree the model is based on a linearization of the axisymmetrical Navier-Stokes equations. The reason for setting up a structured tree is that the smaller arteries consist of an almost binary tree. Furthermore, the role of the smaller arteries is to allow blood perfusion of specific tissues. This is done in a structured and optimal way such that the smaller arteries cover the tissue evenly using a minimization principle.

  14. Epinephrine-induced changes in human cochlear blood flow.

    PubMed

    Miller, J M; Laurikainen, E A; Grénman, R A; Suonpää; Bredberg, G

    1994-05-01

    Cochlear blood flow (CBF) was monitored over the basal turn stria vascularis using laser Doppler flowmetry in five human subjects during middle ear surgery. The effects of systemically administered epinephrine (0.3 microgram/kg) and topically applied epinephrine (1:10,000) on the round window membrane (RWM) were examined. Topical epinephrine caused a mean reduction of 60 percent in CBF (maximum peak reduction 65-85% across subjects), which slowly recovered ( > 10 min) toward baseline following epinephrine removal from the RWM. The changes in CBF are similar to those found in animal studies, but are much larger, indicating a relatively more pronounced role of adrenergic agents in CBF control in humans. Systemic epinephrine caused a 40 percent decrease in skin blood flow, a 90 percent increase in blood pressure (BP), above a resting hypotensive mean level of 65 mmHg, and a 50 percent increase in CBF. The CBF change followed the change in BP, but recovered toward baseline more slowly. The dramatic and somewhat prolonged decreases in CBF with RWM application of epinephrine may compromise sensory function and could account for the occasional unexplained sensorineural hearing loss or tinnitus associated with middle ear procedures that use topical epinephrine. The semipermeability of the RWM may, on the other hand, offer a route for therapeutic increases in CBF with vasodilative agents and provide an appropriate treatment for some cases of sensorineural hearing loss. PMID:8579132

  15. Tracking flow of leukocytes in blood for drug analysis

    NASA Astrophysics Data System (ADS)

    Basharat, Arslan; Turner, Wesley; Stephens, Gillian; Badillo, Benjamin; Lumpkin, Rick; Andre, Patrick; Perera, Amitha

    2011-03-01

    Modern microscopy techniques allow imaging of circulating blood components under vascular flow conditions. The resulting video sequences provide unique insights into the behavior of blood cells within the vasculature and can be used as a method to monitor and quantitate the recruitment of inflammatory cells at sites of vascular injury/ inflammation and potentially serve as a pharmacodynamic biomarker, helping screen new therapies and individualize dose and combinations of drugs. However, manual analysis of these video sequences is intractable, requiring hours per 400 second video clip. In this paper, we present an automated technique to analyze the behavior and recruitment of human leukocytes in whole blood under physiological conditions of shear through a simple multi-channel fluorescence microscope in real-time. This technique detects and tracks the recruitment of leukocytes to a bioactive surface coated on a flow chamber. Rolling cells (cells which partially bind to the bioactive matrix) are detected counted, and have their velocity measured and graphed. The challenges here include: high cell density, appearance similarity, and low (1Hz) frame rate. Our approach performs frame differencing based motion segmentation, track initialization and online tracking of individual leukocytes.

  16. 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. PMID:26677831

  17. Validation of an optical flow algorithm to measure blood flow waveforms in arteries using dynamic digital x-ray images

    NASA Astrophysics Data System (ADS)

    Rhode, Kawal; Lambrou, Tryphon; Hawkes, David J.; Hamilton, George; Seifalian, Alexander M.

    2000-06-01

    We have developed a weighted optical flow algorithm for the extraction of instantaneous blood velocity from dynamic digital x-ray images of blood vessels. We have carried out in- vitro validation of this technique. A pulsatile physiological blood flow circuit was constructed using sections of silicone tubing to simulate blood vessels with whole blood as the fluid. Instantaneous recording of flow from an electromagnetic flow meter (EMF) provided the gold standard measurement. Biplanar dynamic digital x-ray images of the blood vessel with injection of contrast medium were acquired at 25 fps using a PC frame capture card. Imaging of a Perspex calibration cube allowed 3D reconstruction of the vessel and determination of true dimensions. Blood flow waveforms were calculated off-line on a Sun workstation using the new algorithm. The correlation coefficient between instantaneous blood flow values obtained from the EMF and the x-ray method was r equals 0.871, n equals 1184, p less than 0.0001. The correlation coefficient for average blood flow was r equals 0.898, n equals 16, p less than 0.001. We have successfully demonstrated that our new algorithm can measure pulsatile blood flow in a vessel phantom. We aim to use this algorithm to measure blood flow clinically in patients undergoing vascular interventional procedures.

  18. Aminoguanidine effects on nerve blood flow, vascular permeability, electrophysiology, and oxygen free radicals

    SciTech Connect

    Kihara, Mikihiro; Schmelzer, J.D.; Poduslo, J.F.; Curran, G.L.; Nickander, K.K.; Low, P.A. )

    1991-07-15

    Since advanced glycosylation end products have been suggested to mediate hyperglycemia-induced microvascular atherogenesis and because aminoguanidine (AG) prevents their generation, the authors examined whether AG could prevent or ameliorate the physiologic and biochemical indices of streptozotocin (STZ)-induced experimental diabetic neuropathy. Four groups of adult Sprague-Dawley rats were studied: group I received STZ plus AG, group II received STZ plus AG, group III received STZ alone, and group IV was a control. They monitored conduction and action potential amplitudes serially in sciatic-tibial and caudal nerves, nerve blood flow, oxygen free radical activity (conjugated dienes and hydroperoxides), and the product of the permeability coefficient and surface area to {sup 125}I-labeled albumin. STZ-induced diabetes (group III) caused a 57% reduction in nerve blood flow and in abnormal nerve conduction and amplitudes and a 60% increase in conjugated dienes. Nerve blood flow was normalized by 8 weeks with AG (groups I and II) and conduction was significantly improved, in a dose-dependent manner, by 16 and 24 weeks in sciatic-tibial and caudal nerves, respectively. The permeability coefficient was not impaired, suggesting a normal blood-nerve barrier function for albumin, and the oxygen free-radical indices were not ameliorated by AG. They suggest that AG reverses nerve ischemia and more gradually improves their electrophysiology by an action on nerve microvessels. AG may have potential in the treatment of diabetic neuropathy.

  19. Blood flow changes after unilateral carotid artery ligation monitored by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Ma, Yushu; Liang, Chengbo; Suo, Yanyan; Zhao, Yuqian; Wang, Yi; Xu, Tao; Wang, Ruikang; Ma, Zhenhe

    2016-03-01

    Unilateral carotid artery ligation which could induce adaptive improvement is a classic model that has been widely used to study pathology of ischemic disease. In those studies, blood flow is an important parameter to characterize the ischemia. Optical coherence tomography (OCT) is a powerful imaging modality which can provide depth resolved images in biological tissue with high spatial and temporal resolution. SPF rats was anesthetized with isoflurane and divided into two groups. In first group, bilateral carotid artery was surgically exposed, and then left carotid artery was ligated. Blood flow changes of the contralateral carotid artery was monitored using high speed spectral domain optical coherence tomography, including the absolute flow velocity and the flow volume. In the other group, skull window was opened at the ipsilateral cerebral cortex of ligation and blood supply of small artery was measured before and after the ligation. The measured results demonstrate the blood supply compensation process after unilateral carotid artery ligation. With the superiority of high resolution, OCT is an effective technology in monitoring results of carotid artery after ligation.

  20. The endothelial glycocalyx promotes homogenous blood flow distribution within the microvasculature.

    PubMed

    McClatchey, P Mason; Schafer, Michal; Hunter, Kendall S; Reusch, Jane E B

    2016-07-01

    Many common diseases involve impaired tissue perfusion, and heterogeneous distribution of blood flow in the microvasculature contributes to this pathology. The physiological mechanisms regulating homogeneity/heterogeneity of microvascular perfusion are presently unknown. Using established empirical formulations for blood viscosity modeling in vivo (blood vessels) and in vitro (glass tubes), we showed that the in vivo formulation predicts more homogenous perfusion of microvascular networks at the arteriolar and capillary levels. Next, we showed that the more homogeneous blood flow under simulated in vivo conditions can be explained by changes in red blood cell interactions with the vessel wall. Finally, we demonstrated that the presence of a space-filling, semipermeable layer (such as the endothelial glycocalyx) at the vessel wall can account for the changes of red blood cell interactions with the vessel wall that promote homogenous microvascular perfusion. Collectively, our results indicate that the mechanical properties of the endothelial glycocalyx promote homogeneous microvascular perfusion. Preservation or restoration of normal glycocalyx properties may be a viable strategy for improving tissue perfusion in a variety of diseases. PMID:27199117

  1. Longitudinal myocardial blood flow gradient and CAD detection.

    PubMed

    Valenta, Ines; Wahl, Richard L; Schindler, Thomas H

    2015-01-01

    Conventional myocardial perfusion scintigraphy with SPECT/CT or with PET/CT has been established as pivotal clinical imaging modality for the identification of hemodynamically obstructive coronary artery disease (CAD) and risk stratification of patients with suspected or known CAD. While the assessment of the relative distribution of radiotracer uptake in the left-ventricular (LV) myocardium during vasomotor stress identifies the "culprit" or most severe CAD lesion in multivessel disease, flow-limiting effects of remaining but less severe epicardial lesions may be missed. This limitation principally may be overcome by the possibility of PET/CT with radiotracer-kinetic modeling to concurrently assess left-ventricular (LV) myocardial blood flow (MBF) in ml/g/min at rest and during vasomotor stress and the resulting myocardial flow reserve (MFR). While a stress-induced regional reduction in radiotracer uptake or perfusion identifies the most advanced epicardial lesion, flow-limiting effects of the other epicardial lesions may principally be identified by regional reductions in MFR. Conversely, reductions in MFR in CAD may be appreciated as suboptimal as they reflect not only the consequences of flow-limiting effects of epicardial stenosis but also of microvascular dysfunction. The relatively low specificity of a reduced therefore MFR may hamper a clear identification of the downstream hemodynamic effects of an epicardial lesion on hyperemic coronary flow increases. In this scenario, there is increasing evidence that the PET assessment of an abnormal decrease in MBF from the base to the apex of the LV during hyperemic flows, a so-called longitudinal flow gradient, is primarily related to fluid dynamic consequences of CAD-induced diffuse luminal and/or focal narrowing of the epicardial artery. The combined evaluation of the MFR and corresponding longitudinal MBF gradient could emerge as new a novel analytic concept to further optimize the identification and

  2. In vivo measurement of blood flow in the vitelline network

    NASA Astrophysics Data System (ADS)

    Poelma, Christian; Vennemann, Peter; Lindken, Ralph; Westerweel, Jerry

    2007-11-01

    The growth and adaptation of blood vessels is studied in vivo in the so-called vitelline network of a chick embryo. The vitelline network, a system of extra-embryonic blood vessels that transports nutrients from the yolk sac to the chick embryo, is an easily accessible model system for the study of human cardiovascular development and functioning. We present measurements obtained by means of scanning microscopic Particle Image Velocimetry. Using phase-locking, we can reconstruct the full three-dimensional flow as a function of the cardiac cycle. Typical reconstructed volumes are 0.4x0.5x0.2 mm^3 with a spatial resolution (i.e. vector spacing) of 6 μm. These hemodynamic measurements allow a study of the coupling between form and functioning of the blood vessels. Special attention is given to the local wall shear stress (WSS), an important physiological parameter that is thought to determine - to great extent - the adaptation of the vessels to changing conditions. The WSS can be estimated directly from the velocity gradient at the wall or from a fit to the blood velocity profile. The former method slightly underestimates the WSS (most likely due to lack of resolution) but is significantly easier to apply in the complex geometries under consideration.

  3. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging

    NASA Astrophysics Data System (ADS)

    Werkmeister, René M.; Vietauer, Martin; Knopf, Corinna; Fürnsinn, Clemens; Leitgeb, Rainer A.; Reitsamer, Herbert; Gröschl, Martin; Garhöfer, Gerhard; Vilser, Walthard; Schmetterer, Leopold

    2014-10-01

    A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%;. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.

  4. Measurement of retinal blood flow in the rat by combining Doppler Fourier-domain optical coherence tomography with fundus imaging.

    PubMed

    Werkmeister, René M; Vietauer, Martin; Knopf, Corinna; Fürnsinn, Clemens; Leitgeb, Rainer A; Reitsamer, Herbert; Gröschl, Martin; Garhöfer, Gerhard; Vilser, Walthard; Schmetterer, Leopold

    2014-01-01

    A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats. PMID:25321400

  5. Does topical phenylephrine, tropicamide, or proparacaine affect macular blood flow?

    PubMed

    Robinson, F; Petrig, B L; Sinclair, S H; Riva, C E; Grunwald, J E

    1985-08-01

    The acute effect of topical phenylephrine HCl 10%, tropicamide 1% and proparacaine HCl 0.5% on macular capillary blood flow was studied in six healthy human volunteers using the blue field simulation technique. This technique provides a method for quantifying the velocity of leukocytes flowing in one's own retinal macular capillaries. Patients adjusted the velocity of computer simulated leukocytes moving on a CRT screen to match that of their own entoptically perceived leukocytes before instillation of each of the tested preparations and for 35 minutes immediately thereafter A 5% NaCl solution was used as a control. We found no significant difference in leukocyte velocity between the control drop and any of the tested drugs. With the six subjects tested, the calculated average minimum percentage change in leukocyte velocity detectable with this technique (P less than 0.05, paired t-test) was 9%. None of the tested drugs affected macular leukocyte velocity, and presumably blood flow, by more than this amount. PMID:4047607

  6. A time-invariant visco-elastic windkessel model relating blood flow and blood volume.

    PubMed

    Zheng, Ying; Mayhew, John

    2009-10-01

    The difference between the rate of change of cerebral blood volume (CBV) and cerebral blood flow (CBF) following stimulation is thought to be due to circumferential stress relaxation in veins (Mandeville, J.B., Marota, J.J.A., Ayata, C., Zaharchuk, G., Moskowitz, M.A., Rosen, B.R., Weisskoff, R.M., 1999. Evidence of a cerebrovascular postarteriole windkessel with delayed compliance. J. Cereb. Blood Flow Metab. 19, 679-689). In this paper we explore the visco-elastic properties of blood vessels, and present a dynamic model relating changes in CBF to changes in CBV. We refer to this model as the visco-elastic windkessel (VW) model. A novel feature of this model is that the parameter characterising the pressure-volume relationship of blood vessels is treated as a state variable dependent on the rate of change of CBV, producing hysteresis in the pressure-volume space during vessel dilation and contraction. The VW model is nonlinear time-invariant, and is able to predict the observed differences between the time series of CBV and that of CBF measurements following changes in neural activity. Like the windkessel model derived by Mandeville, J.B., Marota, J.J.A., Ayata, C., Zaharchuk, G., Moskowitz, M.A., Rosen, B.R., Weisskoff, R.M., 1999. Evidence of a cerebrovascular postarteriole windkessel with delayed compliance. J. Cereb. Blood Flow Metab. 19, 679-689, the VW model is primarily a model of haemodynamic changes in the venous compartment. The VW model is demonstrated to have the following characteristics typical of visco-elastic materials: (1) hysteresis, (2) creep, and (3) stress relaxation, hence it provides a unified model of the visco-elastic properties of the vasculature. The model will not only contribute to the interpretation of the Blood Oxygen Level Dependent (BOLD) signals from functional Magnetic Resonance Imaging (fMRI) experiments, but also find applications in the study and modelling of the brain vasculature and the haemodynamics of circulatory and

  7. Cerebral blood flow assessment of preterm infants during respiratory therapy with the expiratory flow increase technique

    PubMed Central

    Bassani, Mariana Almada; Caldas, Jamil Pedro Siqueira; Netto, Abimael Aranha; Marba, Sérgio Tadeu Martins

    2016-01-01

    Abstract Objective: To assess the impact of respiratory therapy with the expiratory flow increase technique on cerebral hemodynamics of premature newborns. Methods: 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 5min. Cerebral blood flow velocity and resistance and pulsatility indices in the pericallosal artery were assessed. Results: 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. Conclusions: The expiratory flow increase technique did not affect cerebral blood flow in clinically-stable preterm infants. PMID:26611888

  8. Decreased blood flow rate disrupts endothelial repair in vivo.

    PubMed Central

    Vyalov, S.; Langille, B. L.; Gotlieb, A. I.

    1996-01-01

    Both local hemodynamics and endothelial injury have been implicated in vascular disorders including bypass graft failure and atherogenesis, but little is known about the effect of local blood flow conditions on repair of endothelial injury. We decreased blood flow rates and shear stresses in common carotid arteries of rabbits by ligating the ipsilateral external carotid artery. After 24 hours, endothelial cells were less elongated, contained fewer central microfilament bundles, and showed less polarity of the centrosome toward the heart than endothelial cells in unmanipulated carotid arteries. To examine wound repair, we made narrow longitudinal intimal wounds at the time of flow reduction using a nylon monofilament device. In arteries with normal blood flows, endothelial cells at the edge of the wound initially spread and elongated in the direction of the wound. The dense peripheral band of actin was attenuated and central microfilaments became more prominent. Endothelial cells remained in close contact with their neighbors in the monolayer. The centrosome of cells adjacent to the wound was redistributed toward the wound side of the nucleus at 6 and 12 hours. Complete closure occurred by 24 hours, at which time the elongated endothelial cells covering the wound were organized in a herringbone pattern with their downstream ends at the center of the wound. With decreased flow and shear stress, the cells at the wound edge spread less than those in normal vessels at 12 hours after wounding and were randomly oriented and polygonal in shape. Also, re-endothelialization proceeded more slowly and there was a marked reduction of central microfilaments in cells at the wound edge. At 24 hours, the wounds were still open, the endothelial cells covering the central portion of the wound did not maintain intimate contact with their neighbors, and orientation of the centrosome toward the wound was reduced. We hypothesize that loss of cell-cell contact during repair at low flow

  9. Interactive retinal blood flow analysis of the macular region.

    PubMed

    Tian, Jing; Somfai, Gábor Márk; Campagnoli, Thalmon R; Smiddy, William E; Debuc, Delia Cabrera

    2016-03-01

    The study of retinal hemodynamics plays an important role to understand the onset and progression of diabetic retinopathy. In this work, we developed an interactive retinal analysis tool to quantitatively measure the blood flow velocity (BFV) and blood flow rate (BFR) in the macular region using the Retinal Function Imager (RFI). By employing a high definition stroboscopic fundus camera, the RFI device is able to assess retinal blood flow characteristics in vivo. However, the measurements of BFV using a user-guided vessel segmentation tool may induce significant inter-observer differences and BFR is not provided in the built-in software. In this work, we have developed an interactive tool to assess the retinal BFV and BFR in the macular region. Optical coherence tomography data was registered with the RFI image to locate the fovea accurately. The boundaries of the vessels were delineated on a motion contrast enhanced image and BFV was computed by maximizing the cross-correlation of pixel intensities in a ratio video. Furthermore, we were able to calculate the BFR in absolute values (μl/s). Experiments were conducted on 122 vessels from 5 healthy and 5 mild non-proliferative diabetic retinopathy (NPDR) subjects. The Pearson's correlation of the vessel diameter measurements between our method and manual labeling on 40 vessels was 0.984. The intraclass correlation (ICC) of BFV between our proposed method and built-in software was 0.924 and 0.830 for vessels from healthy and NPDR subjects, respectively. The coefficient of variation between repeated sessions was reduced significantly from 22.5% to 15.9% in our proposed method (p<0.001). PMID:26569349

  10. Deoxygenation Reduces Sickle Cell Blood Flow at Arterial Oxygen Tension.

    PubMed

    Lu, Xinran; Wood, David K; Higgins, John M

    2016-06-21

    The majority of morbidity and mortality in sickle cell disease is caused by vaso-occlusion: circulatory obstruction leading to tissue ischemia and infarction. The consequences of vaso-occlusion are seen clinically throughout the vascular tree, from the relatively high-oxygen and high-velocity cerebral arteries to the relatively low-oxygen and low-velocity postcapillary venules. Prevailing models of vaso-occlusion propose mechanisms that are relevant only to regions of low oxygen and low velocity, leaving a wide gap in our understanding of the most important pathologic process in sickle cell disease. Progress toward understanding vaso-occlusion is further challenged by the complexity of the multiple processes thought to be involved, including, but not limited to 1) deoxygenation-dependent hemoglobin polymerization leading to impaired rheology, 2) endothelial and leukocyte activation, and 3) altered cellular adhesion. Here, we chose to focus exclusively on deoxygenation-dependent rheologic processes in an effort to quantify their contribution independent of the other processes that are likely involved in vivo. We take advantage of an experimental system that, to our knowledge, uniquely enables the study of pressure-driven blood flow in physiologic-sized tubes at physiologic hematocrit under controlled oxygenation conditions, while excluding the effects of endothelium, leukocyte activation, adhesion, inflammation, and coagulation. We find that deoxygenation-dependent rheologic processes are sufficient to increase apparent viscosity significantly, slowing blood flow velocity at arterial oxygen tension even without additional contributions from inflammation, adhesion, and endothelial and leukocyte activation. We quantify the changes in apparent viscosity and define a set of functional regimes of sickle cell blood flow personalized for each patient that may be important in further dissecting mechanisms of in vivo vaso-occlusion as well as in assessing risk of patient

  11. Multimodal flow visualization and optimization of pneumatic blood pump for sorbent hemodialysis system.

    PubMed

    Shu, Fangjun; Parks, Robert; Maholtz, John; Ash, Steven; Antaki, James F

    2009-04-01

    Renal Solutions Allient Sorbent Hemodialysis System utilizes a two-chambered pneumatic pump (Pulsar Blood Pump, Renal Solutions, Inc., Warrendale, PA, USA) to avoid limitations associated with peristaltic pumping systems. Single-needle access is enabled by counter-pulsing the two pump chambers, thereby obviating compliance chambers or blood reservoirs. Each chamber propels 20 cc per pulse of 3 s (dual access) or 6 s (single access) duration, corresponding to a peak Reynolds number of approximately 8000 (based on inlet velocity and chamber diameter). A multimodal series of flow visualization studies (tracer particle, dye washout, and dye erosion) was conducted on a sequence of pump designs with varying port locations and diaphragms to improve the geometry with respect to risk of thrombogenesis. Experiments were conducted in a simplified flow loop using occluders to simulate flow resistance induced by tubing and dialyzer. Tracer visualization revealed flow patterns and qualitatively indicated turbulence intensity. Dye washout identified dwell volume and areas of flow stagnation for each design. Dye erosion results indicated the effectiveness and homogeneity of surface washing. Compared to a centered inlet which resulted in a fluid jet that produced two counter-rotating vortices, a tangential inlet introduced a single vortex, and kept the flow laminar. It also provided better surface washing on the pump inner surface. However, a tangential outlet did not present as much benefit as expected. On the contrary, it created a sharp defection to the flow when transiting from filling to ejection. PMID:19335410

  12. Quantifying Blood Flow in the DIEP Flap: An Ultrasonographic Study

    PubMed Central

    Pennington, David G.

    2014-01-01

    Background: The maximum weight of tissue that a single perforator can perfuse remains an important question in reconstructive microsurgery. An empirically based equation, known as the flap viability index (FVI), has been established to determine what weight of tissue will survive on one or more perforators. The equation is FVI = Sum d(n)^4/W, where d is the internal diameter of each perforator and W is the final weight of the flap. It has been shown that if FVI exceeds 10, total flap survival is likely, but if under 10, partial flap necrosis is probable. The aim of this study was to measure absolute flow rates in deep inferior epigastric perforator (DIEP) flap pedicles and assess correlation with the determinants of the FVI, perforator diameter and flap weight. Methods: Color Doppler ultrasound was used to quantify arterial flow in 10 consecutive DIEP flap pedicles 24 hours after anastomosis. Results: In single-perforator DIEP flaps, flow rate was highly correlated with perforator diameter (r = 0.82, P = 0.01). Mean arterial flow rate was significantly reduced in DIEP flaps with 2 or more perforators (6 vs 38 cm3/min; P < 0.05). Conclusions: This study confirms that perforator size is a critical factor in optimizing blood flow in perforator-based free tissue transfer. Further research is required to understand the flow dynamics of perforator flaps based on multiple perforators. However, surgeons should be cognizant that a single large perforator may have substantially higher flow rates than multiple small perforators. Routine FVI calculation is recommended to ensure complete flap survival. PMID:25426345

  13. Testing of models of flow-induced hemolysis in blood flow through hypodermic needles.

    PubMed

    Chen, Yangsheng; Kent, Timothy L; Sharp, M Keith

    2013-03-01

    Hemolysis caused by flow in hypodermic needles interferes with a number of tests on blood samples drawn by venipuncture, including assays for metabolites, electrolytes, and enzymes, causes discomfort during dialysis sessions, and limits transfusion flow rates. To evaluate design modifications to address this problem, as well as hemolysis issues in other cardiovascular devices, computational fluid dynamics (CFD)-based prediction of hemolysis has potential for reducing the time and expense for testing of prototypes. In this project, three CFD-integrated blood damage models were applied to flow-induced hemolysis in 16-G needles and compared with experimental results, which demonstrated that a modified needle with chamfered entrance increased hemolysis, while a rounded entrance decreased hemolysis, compared with a standard needle with sharp entrance. After CFD simulation of the steady-state velocity field, the time histories of scalar stress along a grid of streamlines were calculated. A strain-based cell membrane failure model and two empirical power-law blood damage models were used to predict hemolysis on each streamline. Total hemolysis was calculated by weighting the predicted hemolysis along each streamline by the flow rate along each streamline. The results showed that only the strain-based blood damage model correctly predicted increased hemolysis in the beveled needle and decreased hemolysis in the rounded needle, while the power-law models predicted the opposite trends. PMID:23419169

  14. Splanchnic blood flow and plus or minus Gx acceleration.

    NASA Technical Reports Server (NTRS)

    Stone, H. L.; Erickson, H.; Sandler, H.

    1972-01-01

    Experimental data show that there is a neurogenic response to acceleration stress in the front to back direction and that this response is intensified during higher accelerative forces. The afferent limb of this response is unknown but possibilities are suggested. The integrated response at high acceleration levels might serve to conserve oxygen during the stress time. The effector limb is the constriction of less critical vascular beds to preserve blood flow to the heart and brain. The concomitant increase in vagal activity causes a slowing down of the heart.

  15. Cerebral blood flow and autoregulation during hypothermic cardiopulmonary bypass

    SciTech Connect

    Johnsson, P.; Messeter, K.; Ryding, E.; Nordstroem, L.S.; Stahl, E.

    1987-04-01

    Mean hemispheric cerebral blood flow (CBF) was studied following intravenous or intraarterial administration of xenon-133, in 10 men admitted for coronary artery bypass grafting. Repeated CBF measurements were performed to evaluate autoregulation before, during, and after cardiopulmonary bypass (CPB). During CPB mean CBF remained unchanged compared with the pre-CPB level, without evidence of cerebral hyperemia or impairment of autoregulation. A marked increase in CBF occurred after CPB and was followed by a time-dependent reduction toward the pre-CPB level. The data support the alpha-stat regulation theory but cannot explain the cerebral vasodilation observed after CPB.

  16. Improved blood velocity measurements with a hybrid image filtering and iterative Radon transform algorithm

    PubMed Central

    Chhatbar, Pratik Y.; Kara, Prakash

    2013-01-01

    Neural activity leads to hemodynamic changes which can be detected by functional magnetic resonance imaging (fMRI). The determination of blood flow changes in individual vessels is an important aspect of understanding these hemodynamic signals. Blood flow can be calculated from the measurements of vessel diameter and blood velocity. When using line-scan imaging, the movement of blood in the vessel leads to streaks in space-time images, where streak angle is a function of the blood velocity. A variety of methods have been proposed to determine blood velocity from such space-time image sequences. Of these, the Radon transform is relatively easy to implement and has fast data processing. However, the precision of the velocity measurements is dependent on the number of Radon transforms performed, which creates a trade-off between the processing speed and measurement precision. In addition, factors like image contrast, imaging depth, image acquisition speed, and movement artifacts especially in large mammals, can potentially lead to data acquisition that results in erroneous velocity measurements. Here we show that pre-processing the data with a Sobel filter and iterative application of Radon transforms address these issues and provide more accurate blood velocity measurements. Improved signal quality of the image as a result of Sobel filtering increases the accuracy and the iterative Radon transform offers both increased precision and an order of magnitude faster implementation of velocity measurements. This algorithm does not use a priori knowledge of angle information and therefore is sensitive to sudden changes in blood flow. It can be applied on any set of space-time images with red blood cell (RBC) streaks, commonly acquired through line-scan imaging or reconstructed from full-frame, time-lapse images of the vasculature. PMID:23807877

  17. MRI of cerebral blood flow under hyperbaric conditions in rats.

    PubMed

    Cardenas, Damon P; Muir, Eric R; Duong, Timothy Q

    2016-07-01

    Hyperbaric oxygen (HBO) therapy has a number of clinical applications. However, the effects of acute HBO on basal cerebral blood flow (CBF) and neurovascular coupling are not well understood. This study explored the use of arterial spin labeling MRI to evaluate changes in baseline and forepaw stimulus-evoked CBF responses in rats (n = 8) during normobaric air (NB), normobaric oxygen (NBO) (100% O2 ), 3 atm absolute (ATA) hyperbaric air (HB) and 3 ATA HBO conditions. T1 was also measured, and the effects of changes in T1 caused by increasing oxygen on the CBF calculation were investigated. The major findings were as follows: (i) increased inhaled oxygen concentrations led to a reduced respiration rate; (ii) increased dissolved paramagnetic oxygen had significant effects on blood and tissue T1 , which affected the CBF calculation using the arterial spin labeling method; (iii) the differences in blood T1 had a larger effect than the differences in tissue T1 on CBF calculation; (iv) if oxygen-induced changes in blood and tissue T1 were not taken into account, CBF was underestimated by 33% at 3 ATA HBO, 10% at NBO and <5% at HB; (v) with correction, CBF values under HBO, HB and NBO were similar (p > 0.05) and all were higher than CBF under NB by ~40% (p < 0.05), indicating that hypercapnia from the reduced respiration rate masks oxygen-induced vasoconstriction, although blood gas was not measured; and (vi) substantial stimulus-evoked CBF increases were detected under HBO, similar to NB, supporting the notion that activation-induced CBF regulation in the brain does not operate through an oxygen-sensing mechanism. CBF MRI provides valuable insights into the effects of oxygen on basal CBF and neurovascular coupling under hyperbaric conditions. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27192391

  18. Improved modeling techniques for turbomachinery flow fields

    SciTech Connect

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-10-01

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbo-machinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tensor. Penn State will lead the effort to make direct measurements of the momentum and thermal mixing stress tensors in high-speed multistage compressor flow field in the turbomachinery laboratory at Penn State. They will also process the data by both conventional and conditional spectrum analysis to derive momentum and thermal mixing stress tensors due to blade-to-blade periodic and aperiodic components, revolution periodic and aperiodic components arising from various blade rows and non-deterministic (which includes random components) correlations. The modeling results from this program will be publicly available and generally applicable to steady-state Navier-Stokes solvers used for turbomachinery component (compressor or turbine) flow field predictions. These models will lead to improved methodology, including loss and efficiency prediction, for the design of high-efficiency turbomachinery and drastically reduce the time required for the design and development cycle of turbomachinery.

  19. Red blood cell clustering in Poiseuille microcapillary flow

    NASA Astrophysics Data System (ADS)

    Tomaiuolo, Giovanna; Lanotte, Luca; Ghigliotti, Giovanni; Misbah, Chaouqi; Guido, Stefano

    2012-05-01

    Red blood cells (RBC) flowing in microcapillaries tend to associate into clusters, i.e., small trains of cells separated from each other by a distance comparable to cell size. This process is usually attributed to slower RBCs acting to create a sequence of trailing cells. Here, based on the first systematic investigation of collective RBC flow behavior in microcapillaries in vitro by high-speed video microscopy and numerical simulations, we show that RBC size polydispersity within the physiological range does not affect cluster stability. Lower applied pressure drops and longer residence times favor larger RBC clusters. A limiting cluster length, depending on the number of cells in a cluster, is found by increasing the applied pressure drop. The insight on the mechanism of RBC clustering provided by this work can be applied to further our understanding of RBC aggregability, which is a key parameter implicated in clotting and thrombus formation.

  20. The Development of a Wireless Implantable Blood Flow Monitor.

    PubMed

    Unadkat, Jignesh V; Rothfuss, Michael; Mickle, Marlin H; Sejdic, Ervin; Gimbel, Michael L

    2015-07-01

    Microvascular anastomotic failure remains an uncommon but devastating problem. Although the implantable Doppler probe is helpful in flap monitoring, the devices are cumbersome, easily dislodged, and plagued by false-positive results. The authors have developed an implantable wireless Doppler monitor prototype from off-the-shelf components and tested it in a swine model. The wireless probe successfully distinguished between femoral vein flow, occlusion, and reflow, and wirelessly reported the different signals reliably. This is the first description of a wireless implantable blood flow sensor for flap monitoring. Future iterations will incorporate an integrated microchip-based Doppler system that will decrease the size to 1 mm, small enough to fit onto an anastomotic coupler. PMID:26111323

  1. Quality Improvement Methodologies Increase Autologous Blood Product Administration

    PubMed Central

    Hodge, Ashley B.; Preston, Thomas J.; Fitch, Jill A.; Harrison, Sheilah K.; Hersey, Diane K.; Nicol, Kathleen K.; Naguib, Aymen N.; McConnell, Patrick I.; Galantowicz, Mark

    2014-01-01

    Abstract: Whole blood from the heart–lung (bypass) machine may be processed through a cell salvaging device (i.e., cell saver [CS]) and subsequently administered to the patient during cardiac surgery. It was determined at our institution that CS volume was being discarded. A multidisciplinary team consisting of anesthesiologists, perfusionists, intensive care physicians, quality improvement (QI) professionals, and bedside nurses met to determine the challenges surrounding autologous blood delivery in its entirety. A review of cardiac surgery patients’ charts (n = 21) was conducted for analysis of CS waste. After identification of practices that were leading to CS waste, interventions were designed and implemented. Fishbone diagram, key driver diagram, Plan–Do–Study–Act (PDSA) cycles, and data collection forms were used throughout this QI process to track and guide progress regarding CS waste. Of patients under 6 kg (n = 5), 80% had wasted CS blood before interventions, whereas those patients larger than 36 kg (n = 8) had 25% wasted CS before interventions. Seventy-five percent of patients under 6 kg who had wasted CS blood received packed red blood cell transfusions in the cardiothoracic intensive care unit within 24 hours of their operation. After data collection and didactic education sessions (PDSA Cycle I), CS blood volume waste was reduced to 5% in all patients. Identification and analysis of the root cause followed by implementation of education, training, and management of change (PDSA Cycle II) resulted in successful use of 100% of all CS blood volume. PMID:24783313

  2. Contribution of flow-dependent vasomotor mechanisms to the autoregulation of cerebral blood flow.

    PubMed

    Koller, Akos; Toth, Peter

    2012-01-01

    Regulation of cerebral blood flow (CBF) is the result of multilevel mechanisms to maintain the appropriate blood supply to the brain while having to comply with the limited space available in the cranium. The latter requirement is ensured by the autoregulation of CBF, in which the pressure-sensitive myogenic response is known to play a pivotal role. However, in vivo increases in pressure are accompanied by increases in flow; yet the effects of flow on the vasomotor tone of cerebral vessels are less known. Earlier studies showed flow-sensitive dilation and/or constriction or both, but no clear picture emerged. Recently, the important role of flow-sensitive mechanism(s) eliciting the constriction of cerebral vessels has been demonstrated. This review focuses on the effect of hemodynamic forces (especially intraluminal flow) on the vasomotor tone of cerebral vessels and the underlying cellular and molecular mechanisms. A novel concept of autoregulation of CBF is proposed, suggesting that (in certain areas of the cerebrovascular tree) pressure- and flow-induced constrictions together maintain an effective autoregulation, and that alterations in these mechanisms may contribute to the development of cerebrovascular disorders. Future studies are warranted to explore the signals, the details of signaling processes and the in vivo importance of these mechanisms. PMID:22739136

  3. Effect of fluorocarbon-for-blood exchange on regional blood flow in rats

    SciTech Connect

    Lee, P.A.; Sylvia, A.L.; Piantadosi, C.A. )

    1988-04-01

    Cerebrocirculatory responses to total perfluorocarbon (FC-43)-for-blood replacement were studied in anesthetized, ventilated rats breathing 100% O{sub 2}. Changes in total and regional cerebral blood flow (CBF) were measured using the radiolabeled-microsphere technique. The data were compared with two control groups of hemoglobin-circulated animals; one group was exposed to arterial hypoxia and the other to isovolemic hemodilution with Krebs-Henseleit-albumin (KHA) solution. Exchange transfusion with FC-43 doubled total and regional CBF, causing preferential flow increases to the cortex and cerebellum. Estimated cerebrovascular resistance fell to 50% of the preexchange value. Both hemodilution and hypoxia control experiments produced CBF responses similar to those obtained in FC-43 animals. Although calculated arterial O{sub 2} contents in all three groups of animals were similar, blood viscosity was normal in hypoxic rats and reduced in KHA and FC-43 animals. Since arterial and cerebrovenous Po{sub 2}s were both high in fluorocarbon-circulated rats, over results suggest that decreased O{sub 2} content and perhaps lower viscosity of the circulating fluorocarbon were responsible for increases in CBF required to maintain sufficient delivery of O{sub 2} to the brain.

  4. Effects of aging and exercise training on skeletal muscle blood flow and resistance artery morphology

    PubMed Central

    Ramsey, Michael W.; Stabley, John N.; Dominguez, James M.; Davis, Robert T.; McCullough, Danielle J.; Muller-Delp, Judy M.; Delp, Michael D.

    2012-01-01

    With old age, blood flow to the high-oxidative red skeletal muscle is reduced and blood flow to the low-oxidative white muscle is elevated during exercise. Changes in the number of feed arteries perforating the muscle are thought to contribute to this altered hyperemic response during exercise. We tested the hypothesis that exercise training would ameliorate age-related differences in blood flow during exercise and feed artery structure in skeletal muscle. Young (6–7 mo old, n = 36) and old (24 mo old, n = 25) male Fischer 344 rats were divided into young sedentary (Sed), old Sed, young exercise-trained (ET), and old ET groups, where training consisted of 10–12 wk of treadmill exercise. In Sed and ET rats, blood flow to the red and white portions of the gastrocnemius muscle (GastRed and GastWhite) and the number and luminal cross-sectional area (CSA) of all feed arteries perforating the muscle were measured at rest and during exercise. In the old ET group, blood flow was greater to GastRed (264 ± 13 and 195 ± 9 ml·min−1·100 g−1 in old ET and old Sed, respectively) and lower to GastWhite (78 ± 5 and 120 ± 6 ml·min−1·100 g−1 in old ET and old Sed, respectively) than in the old Sed group. There was no difference in the number of feed arteries between the old ET and old Sed group, although the CSA of feed arteries from old ET rats was larger. In young ET rats, there was an increase in the number of feed arteries perforating the muscle. Exercise training mitigated old age-associated differences in blood flow during exercise within gastrocnemius muscle. However, training-induced adaptations in resistance artery morphology differed between young (increase in feed artery number) and old (increase in artery CSA) animals. The altered blood flow pattern induced by exercise training with old age would improve the local matching of O2 delivery to consumption within the skeletal muscle. PMID:23042906

  5. Investigation of retinal blood flow in glaucoma patients by Doppler Fourier-domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Yimin; Zhang, Xinbo; Tan, Ou; Huang, David

    2011-03-01

    The measurement of ocular blood flow is important in studying the pathophysiology and treatment of several leading causes of blindness. A pilot study was performed to evaluate the total retinal blood flow in glaucoma patient using Fourier domain optical coherence tomography. For normal people, the measured total retinal flow was between 40.8 and 60.2 μl/minute. We found that eyes with glaucoma had decreased retinal blood flow and average flow veocity, while the venous cross sectional areas were essentially the same as normal. The decrease in blood flow was highly correlated with the severity of visual field loss.

  6. The acute effect of smoking on intervillous blood flow of the placenta.

    PubMed

    Lehtovirta, P; Forss, M

    1978-10-01

    Smoking a standard cigarette caused an acute decrease in intervillous placental blood flow. This change normalized within 15 minutes. At the time intervillous blood flow was depressed, heart rate and blood pressure were elevated and remained so throughout the study period. Repeated decreases in the intervillous blood flow could explain growth retardation of the fetus and some other complications of pregnancy in women who smoke. PMID:708655

  7. Influence of cerebrovascular resistance on the dynamic relationship between blood pressure and cerebral blood flow in humans.

    PubMed

    Smirl, J D; Tzeng, Y C; Monteleone, B J; Ainslie, P N

    2014-06-15

    We examined the hypothesis that changes in the cerebrovascular resistance index (CVRi), independent of blood pressure (BP), will influence the dynamic relationship between BP and cerebral blood flow in humans. We altered CVRi with (via controlled hyperventilation) and without [via indomethacin (INDO, 1.2 mg/kg)] changes in PaCO2. Sixteen subjects (12 men, 27 ± 7 yr) were tested on two occasions (INDO and hypocapnia) separated by >48 h. Each test incorporated seated rest (5 min), followed by squat-stand maneuvers to increase BP variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis (TFA). Beat-to-beat BP, middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv), and end-tidal Pco2 were monitored. Dynamic pressure-flow relations were quantified using TFA between BP and MCAv/PCAv in the very low and low frequencies through the driven squat-stand maneuvers at 0.05 and 0.10 Hz. MCAv and PCAv reductions by INDO and hypocapnia were well matched, and CVRi was comparably elevated (P < 0.001). During the squat-stand maneuvers (0.05 and 0.10 Hz), the point estimates of absolute gain were universally reduced, and phase was increased under both conditions. In addition to an absence of regional differences, our findings indicate that alterations in CVRi independent of PaCO2 can alter cerebral pressure-flow dynamics. These findings are consistent with the concept of CVRi being a key factor that should be considered in the correct interpretation of cerebral pressure-flow dynamics as indexed using TFA metrics. PMID:24744385

  8. Doppler color flow imaging: a new technique for visualization and characterization of the blood flow jet in mitral stenosis.

    PubMed

    Khandheria, B K; Tajik, A J; Reeder, G S; Callahan, M J; Nishimura, R A; Miller, F A; Seward, J B

    1986-08-01

    We used Doppler color flow imaging, a new noninvasive technique for mapping of intracardiac blood flow, to visualize and characterize the blood flow jet in 42 patients with mitral stenosis. Color flow imaging provides information about the direction of blood flow, its velocity, and the presence of turbulence. Although we found various jet configurations, most frequently the jet was centrally and apically directed and had a "candle flame" appearance (a central blue zone surrounded by hues of yellow and orange). The blood flow jet can be used to guide the positioning of the continuous-wave Doppler beam parallel to the blood flow; thus, the accuracy of the Doppler data can be enhanced. This new technology has promising potential for other clinical applications in cardiology. PMID:3724241

  9. Anxiety, pCO2 and cerebral blood flow.

    PubMed

    Van den Bergh, Omer; Zaman, Jonas; Bresseleers, Johan; Verhamme, Peter; Van Diest, Ilse

    2013-07-01

    This study examined the effect of anxiety on cerebral blood flow at different levels of pCO2 in healthy participants (N=29). Three types of breathing were used to manipulate pCO2 in a within-subject threat-of-shock paradigm: spontaneous breathing, CO2-inhalation and hyperventilation resulting in normo-, hyper- and hypocapnia. Transcranial Doppler ultrasonography was used to measure CBF velocity (CBFv) in the right middle cerebral artery, while breathing behavior and end-tidal pCO2 were monitored. During normocapnia, elevated anxiety was clearly associated with increased CBFv. Consistent with the cerebral vasoconstrictive and vasodilating effects of, respectively, hypo- and hypercapnia, we observed a positive linear association between CBFv and pCO2. The slope of this association became steeper with increasing anxiety, indicating that anxiety enhances the sensitivity of CBFv to changes in pCO2. The findings may elucidate conflicting findings in the literature and are relevant for brain imaging relying on regional cerebral blood flow. PMID:23727628

  10. Virtual Interventions for Image-based Blood Flow Computation

    PubMed Central

    Xiong, Guanglei; Choi, Gilwoo; Taylor, Charles A.

    2011-01-01

    Image-based blood flow computation provides great promise for evaluation of vascular devices and assessment of surgical procedures. However, many previous studies employ idealized arterial and device models or only patient-specific models from the image data after device deployment, since the tools for model construction are unavailable or limited and tedious to use. Moreover, in contrast to retrospective studies from existing data, there is a pressing need for prospective analysis with the goal of surgical planning. Therefore, it is necessary to construct models with deployed devices in a fast, virtual and interactive fashion. The goal of this paper is to develop new geometric methods to deploy stents or stent grafts virtually to patient-specific geometric models constructed from a 3D segmentation of medical images. A triangular surface representing the vessel lumen boundary is extracted from the segmentation. The diseased portion is either clipped and replaced by the surface of a deployed device or rerouted in the case of a bypass graft. For diseased arteries close to bifurcations, bifurcated device models are generated. A method to map a 2D strut pattern on the surface of a device is also presented. We demonstrate three applications of our methods in personalized surgical planning for aortic aneurysms, aortic coarctation, and coronary artery stenosis using blood flow computation. Our approach enables prospective model construction and may help to expand the throughput required by routine clinical uses in the future. PMID:22121255

  11. Multiscale modeling and simulation of brain blood flow

    NASA Astrophysics Data System (ADS)

    Perdikaris, Paris; Grinberg, Leopold; Karniadakis, George Em

    2016-02-01

    The aim of this work is to present an overview of recent advances in multi-scale modeling of brain blood flow. In particular, we present some approaches that enable the in silico study of multi-scale and multi-physics phenomena in the cerebral vasculature. We discuss the formulation of continuum and atomistic modeling approaches, present a consistent framework for their concurrent coupling, and list some of the challenges that one needs to overcome in achieving a seamless and scalable integration of heterogeneous numerical solvers. The effectiveness of the proposed framework is demonstrated in a realistic case involving modeling the thrombus formation process taking place on the wall of a patient-specific cerebral aneurysm. This highlights the ability of multi-scale algorithms to resolve important biophysical processes that span several spatial and temporal scales, potentially yielding new insight into the key aspects of brain blood flow in health and disease. Finally, we discuss open questions in multi-scale modeling and emerging topics of future research.

  12. Regional cerebral blood flow abnormalities in Alzheimer's Disease

    SciTech Connect

    Rezai, K.; Damasio, H.; Graff-Radford, N.; Eslinger, P.; Kirchner, P.

    1985-05-01

    In 37 patients (ages 58-81) with senile dementia of Alzheimer type (SDAT), regional cerebral blood flow (rCBF) was studied utilizing a dedicated SPECT system (Tomomatic-64) that produces rCBF images from 4-minute clearance of Xenon-133 in the brain. The authors have modified the device to acquire 5 continuous tomographic slices simultaneously. A consistent pattern of diminished blood flow was seen in 33 patients in the posterior-temporal and lower-parietal brain regions. Computer programs were developed to quantitate the size of the affected brain tissue in the posterolateral brain areas (confined to the posterior 40% and the lateral 25% of the major and minor brain axes respectively). They have previously reported normal rCBF in 25 volunteers to be greater than 45 ml/min/100g with less than 10% regional variation. Hence, an area was considered abnormal if rCBF measured less than 40 ml/min/100g or was less than 70% of the mean rCBF value in the anterior temporal-frontal regions.

  13. Assessment of hand blood flow: A modified technique

    SciTech Connect

    Kirsh, J.C.; Tepperman, P.S.

    1985-05-01

    Radionuclide blood flow studies are frequently used in conjunction with static bone imaging of the hands to obtain valuable information regarding relative vascularity. This study was undertaken to demonstrate; a significant blood flow artefact with the conventional bolus injection technique (Tc-99m MDP) used in dynamic hand imaging, and a modified technique which virtually eliminates this artefact. The artefact is presumably due to reactive hyperemia induced by the tourniquet used to occlude venous return prior to injection. A modified technique was developed using intermittent injections of saline via a butterfly needle to maintain venous patency. This allows time for the reflex hyperemia to return to the basal state before injecting the radiopharmaceutical. Only 1 of 23 additional subject (4%) demonstrated significant artefactual asymmetry with the modified technique. A highly significant different (rho < .001) was observed between the two techniques. Additionally, there was no significant difference (rho = .50) between the observed pattern with the modified technique and the expected normal symmetrical pattern. Therefore, use of this technique will eliminate a potentially seriously misleading artefact.

  14. Altered Cerebral Blood Flow Covariance Network in Schizophrenia

    PubMed Central

    Liu, Feng; Zhuo, Chuanjun; Yu, Chunshui

    2016-01-01

    Many studies have shown abnormal cerebral blood flow (CBF) in schizophrenia; however, it remains unclear how topological properties of CBF network are altered in this disorder. Here, arterial spin labeling (ASL) MRI was employed to measure resting-state CBF in 96 schizophrenia patients and 91 healthy controls. CBF covariance network of each group was constructed by calculating across-subject CBF covariance between 90 brain regions. Graph theory was used to compare intergroup differences in global and nodal topological measures of the network. Both schizophrenia patients and healthy controls had small-world topology in CBF covariance networks, implying an optimal balance between functional segregation and integration. Compared with healthy controls, schizophrenia patients showed reduced small-worldness, normalized clustering coefficient and local efficiency of the network, suggesting a shift toward randomized network topology in schizophrenia. Furthermore, schizophrenia patients exhibited altered nodal centrality in the perceptual-, affective-, language-, and spatial-related regions, indicating functional disturbance of these systems in schizophrenia. This study demonstrated for the first time that schizophrenia patients have disrupted topological properties in CBF covariance network, which provides a new perspective (efficiency of blood flow distribution between brain regions) for understanding neural mechanisms of schizophrenia. PMID:27445677

  15. Altered Cerebral Blood Flow Covariance Network in Schizophrenia.

    PubMed

    Liu, Feng; Zhuo, Chuanjun; Yu, Chunshui

    2016-01-01

    Many studies have shown abnormal cerebral blood flow (CBF) in schizophrenia; however, it remains unclear how topological properties of CBF network are altered in this disorder. Here, arterial spin labeling (ASL) MRI was employed to measure resting-state CBF in 96 schizophrenia patients and 91 healthy controls. CBF covariance network of each group was constructed by calculating across-subject CBF covariance between 90 brain regions. Graph theory was used to compare intergroup differences in global and nodal topological measures of the network. Both schizophrenia patients and healthy controls had small-world topology in CBF covariance networks, implying an optimal balance between functional segregation and integration. Compared with healthy controls, schizophrenia patients showed reduced small-worldness, normalized clustering coefficient and local efficiency of the network, suggesting a shift toward randomized network topology in schizophrenia. Furthermore, schizophrenia patients exhibited altered nodal centrality in the perceptual-, affective-, language-, and spatial-related regions, indicating functional disturbance of these systems in schizophrenia. This study demonstrated for the first time that schizophrenia patients have disrupted topological properties in CBF covariance network, which provides a new perspective (efficiency of blood flow distribution between brain regions) for understanding neural mechanisms of schizophrenia. PMID:27445677

  16. Laser Doppler flowmetry: reproducibility, reliability, and diurnal blood flow variations.

    PubMed

    Roeykens, Herman J J; Deschepper, Ellen; De Moor, Roeland J G

    2016-08-01

    The aim of this investigation was (1) to evaluate the reliability of laser Doppler flowmetry (LDF) taking into consideration the use of a silicone splint and the inclination of the probe towards the buccal surface of a human tooth and (2) to determine whether diurnal variations of pulpal blood flow can be registered by means of LDF. Forty-one splints were made by one and the same principal investigator for the registration of pulpal blood flow in vivo in a maxillary right central incisor. Thirty dentists, without experience in LDF recording, were then asked to drill a right-angled shaft in a pre-manufactured splint with a referral point at 2 mm from the enamel-cement border central on the buccal surface of the right central upper incisor. The remaining 11 splints were handled by the principal investigator. The shafts in the 30 splints were analysed using Cone Beam CT imaging of the axial and sagittal angles and compared these to the 11 shafts prepared by the trained principal investigator. LDF was recorded for 90 s in each splint and statistically analysed. LDF values without the use of a splint were statistically significantly different (p < 0.05) and the variance was greater, indicating the superiority of splint use. Significant diurnal variations on LDF values were observed, indicating that special attention should be paid to registration during the day, especially when multiple measurements are to be compared. PMID:27184153

  17. Microfluidic blood plasma separation via bulk electrohydrodynamic flows

    PubMed Central

    Arifin, Dian R.; Yeo, Leslie Y.; Friend, James R.

    2007-01-01

    An effective mechanism for rapid and efficient microfluidic particle trapping and concentration is proposed without requiring any mechanically moving parts. When a voltage beyond the threshold atmospheric ionization value is applied on a sharp electrode tip mounted at an angle above a microfluidic liquid chamber, the bulk electrohydrodynamic air thrust that is generated results in interfacial shear and, hence, primary azimuthal liquid surface recirculation. This discharge driven vortex mechanism, in turn, causes a secondary bulk meridional liquid recirculation, which produces an inward radial force near the bottom of the chamber. Particles suspended in the liquid are then rapidly convected by the bulk recirculation toward the bottom, where the inward radial force causes them to spiral in a helical swirl-like fashion toward a stagnation point. In particular, we show that these flows, similar to Batchelor flows occurring in a cylindrical liquid column between a stationary and rotating disk, can be used for the separation of red blood cells from blood plasma in a miniaturized device. PMID:19693352

  18. Cerebral blood flow autoregulation during intracranial hypertension in hypoxic lambs

    SciTech Connect

    Borel, C.O.; Backofen, J.E.; Koehler, R.C.; Jones, M.D. Jr.; Traystman, R.J. )

    1987-12-01

    The authors tested the hypothesis that hypoxic hypoxia interferes with cerebral blood flow (CBF) autoregulation when intracranial pressure (ICP) is elevated in pentobarbital-anesthetized lambs (3 to 9 days old). Cerebral perfusion pressure (CPP) was lowered stepwise from 73 to 23 mmHg in eight normoxic lambs and from 65 to 31 mmHg in eight other hypoxic lambs by ventricular infusion of artificial cerebrospinal fluid. In normoxic lambs, CBF measured by microspheres labeled with six different radioisotopes was not significantly changed over this range of CPP. In animals made hypoxic, base-line CBF was twice that of normoxic lambs. CBF was unchanged as CPP was reduced to 31 mmHg. Lower levels of CPP were not attained because a pressor response occurred with further elevations of ICP. No regional decrements in blood flow to cortical arterial watershed areas or to more caudal regions, such as cerebellum, brain stem, or thalamus, were detected with elevated ICP. Cerebral O{sub 2} uptake was similar in both groups and did not decrease when CPP was reduced. These results demonstrate that normoxic lambs have a considerable capacity for effective autoregulation of CBF when ICP is elevated. Moreover, cerebral vasodilation in response to a level of hypoxia approximating that normally seen prenatally does not abolish CBF autoregulation when ICP is elevated during the first postnatal week.

  19. Gossypol effects on endothelial cells and tumor blood flow

    SciTech Connect

    Benz, C.C.; Iyer, S.B.; Asgari, H.S.; Matlin, S.A.; Aronson, F.R. ); Barchowsky, A. )

    1991-01-01

    Isomers (-,+) of the antitumor agent gossypol (G) were studied for their ability to reduce tumor ATP and blood flow in rats bearing subcutaneously implanted pancreatic tumors. A 50% reduction in tumor ATP/Pi within 1h of a single injection of -G was associated with a 60% decline in tumor blood flow. To determine if these changes in tumor physiology could be due to a direct drug effect on tumor endothelium, G isomers were compared for their ability to alter protein ({sup 125}1-BSA) permeability and metabolic ({sup 32}P) labelling of cultured endothelial cells. Treatments for 1h produced no endothelial cell leakage, but 24h exposures to either -G or +G produced complete permeability of the monolayers to {sup 125}1-BSA. In contrast, 0.5-1.0h exposures to -G or +G produced 2 to 3-fold increases in phosphorylated 27kDa heat-shock protein, hsp-27. Hsp-27 phosphoprotein isoforms were differentially labelled following -G and +G exposures with the phosphorylation profile of -G appearing most similar to that of oxyradical producing agents known to induce hsp-27 and injure endothelial cells. The authors postulate that the tumor ischemic effects of -G are mediated by endothelial response to oxyradical production in a mechanism similar to that of tissue ischemia-reperfusion injury.

  20. Regional cerebral blood flow abnormalities in chronic solvent abusers.

    PubMed

    Okada, S; Yamanouchi, N; Kodama, K; Uchida, Y; Hirai, S; Sakamoto, T; Noda, S; Komatsu, N; Sato, T

    1999-06-01

    This study aimed to reveal regional abnormalities of cerebral blood flow (CBF) and their relation to amotivational syndrome which causes poor social prognosis in solvent abusers Sixteen chronic solvent abusers (12 males and four females) along with five normal subjects underwent single photon emission computed tomography with N-isopropyl-p[123I]iodoamphetamine. The patients received a clinical evaluation with the Scale for the Assessment of Negative Symptoms. Using a semiquantitative method (normalized by the parietal cortex count), patients showed a statistically significant decrease in regional cerebral blood flow (rCBF) in the bilateral prefrontal cortices (P<0.01). In addition, the severity of hypoperfusion in the bilateral prefrontal cortices was related to the degree of severity of the avolition-apathy scale on SANS (left; P<0.05, right; P<0.01) even after excluding the effect of antipsychotics. These results suggest that rCBF abnormalities, especially in the prefrontal cortex, develop in chronic solvent abusers, and that this frontal hypoperfusion may be a biological basis of amotivational syndrome. PMID:10459736

  1. Adipose tissue and skeletal muscle blood flow during mental stress

    SciTech Connect

    Linde, B.; Hjemdahl, P.; Freyschuss, U.; Juhlin-Dannfelt, A.

    1989-01-01

    Mental stress (a modified Stroop color word conflict test (CWT)) increased adipose tissue blood flow (ATBF; 133Xe clearance) by 70% and reduced adipose tissue vascular resistance (ATR) by 25% in healthy male volunteers. The vasculatures of adipose tissue (abdomen as well as thigh), skeletal muscle of the calf (133Xe clearance), and the entire calf (venous occlusion plethysmography) responded similarly. Arterial epinephrine (Epi) and glycerol levels were approximately doubled by stress. Beta-Blockade by metoprolol (beta 1-selective) or propranolol (nonselective) attenuated CWT-induced tachycardia similarly. Metoprolol attenuated stress-induced vasodilation in the calf and tended to do so in adipose tissue. Propranolol abolished vasodilation in the calf and resulted in vasoconstriction during CWT in adipose tissue. Decreases in ATR, but not in skeletal muscle or calf vascular resistances, were correlated to increases in arterial plasma glycerol (r = -0.42, P less than 0.05), whereas decreases in skeletal muscle and calf vascular resistances, but not in ATR, were correlated to increases in arterial Epi levels (r = -0.69, P less than 0.01; and r = -0.43, P less than 0.05, respectively). The results suggest that mental stress increases nutritive blood flow in adipose tissue and skeletal muscle considerably, both through the elevation of perfusion pressure and via vasodilatation. Withdrawal of vasoconstrictor nerve activity, vascular beta 2-adrenoceptor stimulation by circulating Epi, and metabolic mechanisms (in adipose tissue) may contribute to the vasodilatation.

  2. Attenuated skin blood flow response to hyperthermia in paraplegic men.

    PubMed

    Freund, P R; Brengelmann, G L; Rowell, L B; Halar, E

    1984-04-01

    To clarify how skin and internal temperatures interact in control of skin blood flow, five male paraplegic subjects (lesions at the level of thoracic vertebrae 1-11) (29-47 yr old) were heated in water-perfused suits to elevate oral temperature (To) 1-1.5 degrees C. In part I only the insensate skin was heated; sensate skin was kept at 32-34 degrees C. No appreciable elevation of forearm blood flow (FBF) or sweating occurred, even with To at 38 degrees C. In part II the suit was applied to the whole body so that skin temperature was 40 degrees C, except for one arm that remained at 32-34 degrees C for FBF measurement. Sweating was noted above the lesion in all but one subject. FBF increased in all subjects but was far below levels previously reported for hyperthermic normal men; also, thresholds appeared elevated. To the extent that effector connections are intact, attenuated FBF response implies that either 1) some vasoconstrictor bias associated with cardiovascular regulation is active or 2) thermoregulatory effector outflow is diminished. If the latter is true, it follows that the effector outflow reduction relates to diminished afferent input. But the component of the effector outflow contributed by peripheral thermoreception is small; thus these findings may indicate that what is lacking in the afferent input is central thermoreception from below the lesion, possibly from the spinal cord itself. PMID:6725058

  3. 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.

  4. Transient finite element analysis of thermal methods used to estimate SAR and blood flow in homogeneously and nonhomogeneously perfused tumour models.

    PubMed

    Wong, T Z; Mechling, J A; Jones, E L; Strohbehn, J W

    1988-01-01

    A two-dimensional time-dependent finite element model was developed to evaluate thermal techniques for estimating blood flow and specific absorption rate (SAR). In these computer simulations, homogeneously and nonhomogeneously perfused tumour models were heated by a 915 MHz interstitial microwave antenna array. Representative blood flow values were assigned within the tumour, and the applied SAR distribution was based on a previously developed antenna theory. SAR values were estimated from the power-on transient temperatures, and blood flow values were estimated from thermal clearance data after power was discontinued. These estimated parameters were then compared to the known 'true' blood flow and SAR values throughout the treatment region. SAR values could be predicted with reasonable accuracy throughout most of the heated region independent of local blood flow. For a homogeneous model, thermal clearance was found to yield reasonably accurate blood flow estimates at high perfusion rates and less accurate estimates at lower perfusion rates. However, for the inhomogeneous model, the blood perfusion estimates were generally poor, and an average blood flow value for the tumour was obtained with little ability to resolve the differences in perfusion between regions. Using temperatures observed early in the cool-down curve resulted in improved spatial resolution, but increased the contribution of thermal conduction to the blood flow estimates. A single time-constant exponential thermal decay curve was found to be a necessary but not sufficient condition for reliable blood flow estimates using this technique. PMID:3171254

  5. Modifying shale oil to improve flow characteristics

    SciTech Connect

    Seitzer, W.H.; Lovell, P.F.

    1982-05-01

    Shale oil, which forms a viscous, wax slurry below 25 C, was treated in several different ways to try to improve its flow characteristics as measured in a concentric cylinder viscometer. Removing the wax does not greatly improve the pumpability of the oil. Hydrotreatment of the whole oil to take out nitrogen, sulfur, and oxygen can lower the viscosity by a factor of five or more, even though the pour point is not greatly affected. Apparently hydrogenolysis of the nitrogen, sulfur, and oxygen lowers the molecular weight of the oil without much modification of the paraffinic wax. The pour point of the shale oil can be decreased with various commercial pour improvers. Sometimes an accompanying drop in viscosity is observed, but most of this decrease is not stable to shear in the viscometer.

  6. Determinants of resting cerebral blood flow in sickle cell disease.

    PubMed

    Bush, Adam M; Borzage, Matthew T; Choi, Soyoung; Václavů, Lena; Tamrazi, Benita; Nederveen, Aart J; Coates, Thomas D; Wood, John C

    2016-09-01

    Stroke is common in children with sickle cell disease and results from an imbalance in oxygen supply and demand. Cerebral blood flow (CBF) is increased in patients with sickle cell disease to compensate for their anemia, but adequacy of their oxygen delivery has not been systematically demonstrated. This study examined the physiological determinants of CBF in 37 patients with sickle cell disease, 38 ethnicity matched control subjects and 16 patients with anemia of non-sickle origin. Cerebral blood flow was measured using phase contrast MRI of the carotid and vertebral arteries. CBF increased inversely to oxygen content (r(2)  = 0.69, P < 0.0001). Brain oxygen delivery, the product of CBF and oxygen content, was normal in all groups. Brain composition, specifically the relative amounts of grey and white matter, was the next strongest CBF predictor, presumably by influencing cerebral metabolic rate. Grey matter/white matter ratio and CBF declined monotonically until the age of 25 in all subjects, consistent with known maturational changes in brain composition. Further CBF reductions were observed with age in subjects older than 35 years of age, likely reflecting microvascular aging. On multivariate regression, CBF was independent of disease state, hemoglobin S, hemoglobin F, reticulocyte count and cell free hemoglobin, suggesting that it is regulated similarly in patients and control subjects. In conclusion, sickle cell disease patients had sufficient oxygen delivery at rest, but accomplish this only by marked increases in their resting CBF, potentially limiting their ability to further augment flow in response to stress. Am. J. Hematol. 91:912-917, 2016. © 2016 Wiley Periodicals, Inc. PMID:27263497

  7. Autoregulation of cerebral blood flow in orthostatic hypotension

    NASA Technical Reports Server (NTRS)

    Novak, V.; Novak, P.; Spies, J. M.; Low, P. A.

    1998-01-01

    BACKGROUND AND PURPOSE: We sought to evaluate cerebral autoregulation in patients with orthostatic hypotension (OH). METHODS: We studied 21 patients (aged 52 to 78 years) with neurogenic OH during 80 degrees head-up tilt. Blood flow velocities (BFV) from the middle cerebral artery were continuously monitored with transcranial Doppler sonography, as were heart rate, blood pressure (BP), cardiac output, stroke volume, CO2, total peripheral resistance, and cerebrovascular resistance. RESULTS: All OH patients had lower BP (P<.0001), BFV_diastolic (P<.05), CVR (P<.007), and TPR (P<.02) during head-up tilt than control subjects. In control subjects, no correlations between BFV and BP were found during head-up tilt, suggesting normal autoregulation. OH patients could be separated into those with normal or expanded autoregulation (OH_NA; n=16) and those with autoregulatory failure (OH_AF; n=5). The OH_NA group showed either no correlation between BFV and BP (n=8) or had a positive BFV/BP correlation (R2>.75) but with a flat slope. An expansion of the "autoregulated" range was seen in some patients. The OH_AF group was characterized by a profound fall in BFV in response to a small reduction in BP (mean deltaBP <40 mm Hg; R2>.75). CONCLUSIONS: The most common patterns of cerebral response to OH are autoregulatory failure with a flat flow-pressure relationship or intact autoregulation with an expanded autoregulated range. The least common pattern is autoregulatory failure with a steep flow-pressure relationship. Patients with patterns 1 and 2 have an enhanced capacity to cope with OH, while those with pattern 3 have reduced capacity.

  8. Novel laser Doppler flowmeter for pulpal blood flow measurements

    NASA Astrophysics Data System (ADS)

    Zang, De Yu; Millerd, James E.; Wilder-Smith, Petra B. B.; Arrastia-Jitosho, Anna-Marie A.

    1996-04-01

    We have proposed and experimentally demonstrated a new configuration of laser Doppler flowmetry for dental pulpal blood flow measurements. To date, the vitality of a tooth can be determined only by subjective thermal or electric tests, which are of questionable reliability and may induced pain in patient. Non-invasive techniques for determining pulpal vascular reactions to injury, treatment, and medication are in great demand. The laser Doppler flowmetry technique is non-invasive; however, clinical studies have shown that when used to measure pulpal blood flow the conventional back-scattering Doppler method suffers from low signal-to-noise ratio (SNR) and unreliable flux readings rendering it impossible to calibrate. A simplified theoretical model indicates that by using a forward scattered geometry the detected signal has a much higher SNR and can be calibrated. The forward scattered signal is readily detectable due to the fact that teeth are relatively thin organs with moderate optical loss. A preliminary experiment comparing forward scattered detection with conventional back- scattered detection was carried out using an extracted human molar. The results validated the findings of the simple theoretical model and clearly showed the utility of the forward scattering geometry. The back-scattering method had readings that fluctuated by as much as 187% in response to small changes in sensor position relative to the tooth. The forward scattered method had consistent readings (within 10%) that were independent of the sensor position, a signal-to-noise ratio that was at least 5.6 times higher than the back-scattering method, and a linear response to flow rate.

  9. An intraventricular axial flow blood pump integrated with a bearing purge system.

    PubMed

    Yamazaki, K; Kormos, R; Mori, T; Umezu, M; Kameneva, M; Antaki, J; Outa, E; Litwak, P; Kerrigan, J; Tomczak, J

    1995-01-01

    The future development of implantable axial flow blood pumps must address two major issues: mechanically induced hemolysis and shaft seal reliability. The recent revisions to our miniature intraventricular axial flow left ventricular assist device (LVAD) were aimed particularly at addressing these concerns. To improve hemocompatibility, a new impeller has been designed according to the following criteria: 1) gradual pressure rise along the blade chord; 2) minimized local fluid acceleration to prevent cavitation; 3) minimum surface roughness; and 4) radius edges. Subsequent in vitro hemolysis tests conducted with bovine and ovine blood have demonstrated very low hemolysis (normalized index of hemolysis = 0.0051 +/- 0.0047 g/100 L) with this new impeller design. To address the need for a reliable seal, we have developed a purged seal system consisting of a miniature lip seal and ceramic pressure groove journal bearing that also acts as a purge pump. Several spiral grooves formed on the bearing surface provide viscous pumping of the purge fluid, generating more than 3,000 mmHg at 10,000 rpm. This purge flow flushes the lip seal and prevents blood backflow into the bearing. We have found this purge pump to offer several advantages because it is simple, compact, durable, does not require separate actuation, and offers a wide range of flow, depending upon the groove design. In vivo animal tests demonstrated the potential of the purged seal system. PMID:8573818

  10. Improved in Vitro Blood Compatibility of Polycaprolactone Nanowire Surfaces

    PubMed Central

    2015-01-01

    There are a multitude of polymeric materials currently utilized to prepare a variety of blood-contacting implantable medical devices. These devices include tissue grafts, coronary artery and vascular stents, and orthopedic implants. The thrombogenic nature of such materials can cause serious complications in patients, and ultimately lead to functional failure. To date, there is no truly hemocompatible biomaterial surface. Nanostructured surfaces improve cellular interactions but there is a limited amount of information regarding their blood compatibility. In this study, the in vitro blood compatibility of four different surfaces (control, PCL; nanowire, NW; collagen immobilized control, cPCL; collagen immobilized nanowire, cNW) were investigated for their use as interfaces for blood-contacting implants. The results presented here indicate enhanced in vitro blood compatibility of nanowire surfaces compared control surfaces. Although there were no significant differences in leukocyte adhesion, there was a decrease in platelet adhesion on NW surfaces. Scanning electron microscopy images showed a decrease in platelet/leukocyte complexes on cNW surfaces and no apparent complexes were formed on NW surfaces compared to PCL and cPCL surfaces. The increase in these complexes likely contributed to a higher expression of specific markers for platelet and leukocyte activation on PCL and cPCL surfaces. No significant differences were found in contact and complement activation on any surface. Further, thrombin antithrombin complexes were significantly reduced on NW surfaces. A significant increase in hemolysis and fibrinogen adsorption was identified on PCL surfaces likely caused by its hydrophobic surface. This work shows the improved blood-compatibility of nanostructured surfaces, identifying this specific nanoarchitecture as a potential interface for promoting the long-term success of blood-contacting biomaterials. PMID:25184556

  11. Role of hypotension in decreasing cerebral blood flow in porcine endotoxemia

    SciTech Connect

    Miller, C.F.; Breslow, M.J.; Shapiro, R.M.; Traystman, R.J. )

    1987-10-01

    The role of reduced arterial blood pressure (MAP) in decreasing cerebral blood flow (CBF) during endotoxemia was studied in pentobarbital-anesthetized pigs. Microspheres were used to measure regional CBF changes during MAP manipulations in animals with and without endotoxin. Endotoxin decreased MAP to 50 mmHg and decreased blood flow to the cortex and cerebellum without affecting cerebral cortical oxygen consumption (CMRo{sub 2}). Elevating MAP from 50 to 70 mmHg during endotoxemia with norepinephrine did not change cortical blood flow or CMRo{sub 2} but increased cerebellar blood flow. Brain stem blood flow was not affected by endotoxin or norepinephrine. When MAP was decreased to 50 mmHg by hemorrhage without endotoxin, no change in blood flow to cortex, cerebellum, or brain stem was observed from base-line levels. These results suggest that decreased MAP below a lower limit for cerebral autoregulation does not account for the decreased CBF observed after endotoxin.

  12. Observation of tumor microvessels that are controlled by blood flow in breast cancer

    NASA Astrophysics Data System (ADS)

    Ishida, H.; Andoh, T.; Akiguchi, S.; Kyoden, T.; Hachiga, T.

    2015-04-01

    We attempted to perform non-invasive breast cancer imaging using a reflection-type multipoint laser Doppler velocimeter to monitor blood flow. On day six, after transplantation of cancer cells into mouse breast, we found that blood flow velocity in a blood vessel that extended into the tumor was increased compared to that in normal skin. The effect of carcinogenesis on blood flow over such a short period was shown using blood flow velocity imaging. Although such imaging has not yet been adapted for use in humans, this study is an important step in reaching the ultimate goal, which is early detection of breast cancer.

  13. Light therapy modulates serotonin levels and blood flow in women with headache. A preliminary study.

    PubMed

    Tomaz de Magalhães, Miriam; Núñez, Silvia Cristina; Kato, Ilka Tiemy; Ribeiro, Martha Simões

    2016-01-01

    In this study, we looked at the possible effects of low-level laser therapy (LLLT) on blood flow velocity, and serotonin (5-HT) and cholinesterase levels in patients with chronic headache associated with temporomandibular disorders (TMD). LLLT has been clinically applied over the past years with positive results in analgesia and without the report of any side effects. The understanding of biological mechanisms of action may improve clinical results and facilitate its indication. Ten patients presenting headache associated with TMD completed the study. An 830-nm infrared diode laser with power of 100 mW, exposure time of 34 s, and energy of 3.4 J was applied on the tender points of masseter and temporal muscle. Blood flow velocity was determined via ultrasound Doppler velocimetry before and after laser irradiation. The whole blood 5-HT and cholinesterase levels were evaluated three days before, immediately, and three days after laser irradiation. Pain score after treatment decreased to a score of 5.8 corresponding to 64% of pain reduction (P < 0.05). LLLT promoted a decrease in the blood flow velocity (P < 0.05). In addition, the 5-HT levels were significantly increased three days after LLLT (P < 0.05). The cholinesterase levels remained unchanged at the analyzed time points (P > 0.05). Our findings indicated that LLLT regulates blood flow in the temporal artery after irradiation and might control 5-HT levels in patients suffering with tension-type headache associated to TMD contributing to pain relief. PMID:26202374

  14. Magnetic resonance temperature imaging-based quantification of blood flow-related energy losses.

    PubMed

    Dillon, Christopher; Roemer, Robert; Payne, Allison

    2015-07-01

    This study presents a new approach for evaluating bioheat transfer equation (BHTE) models used in treatment planning, control and evaluation of all thermal therapies. First, 3D magnetic resonance temperature imaging (MRTI) data are used to quantify blood flow-related energy losses, including the effects of perfusion and convection. Second, this information is used to calculate parameters of a BHTE model: in this paper the widely used Pennes BHTE. As a self-consistency check, the BHTE parameters are utilized to predict the temperatures from which they were initially derived. The approach is evaluated with finite-difference simulations and implemented experimentally with focused ultrasound heating of an ex vivo porcine kidney perfused at 0, 20 and 40 ml/min (n = 4 each). The simulation results demonstrate accurate quantification of blood flow-related energy losses, except in regions of sharp blood flow discontinuities, where the transitions are spatially smoothed. The smoothed transitions propagate into estimates of the Pennes perfusion parameter but have limited effect on the accuracy of temperature predictions using these estimates. Longer acquisition time periods mitigate the effects of MRTI noise, but worsen the effect of flow discontinuities. For the no-flow kidney experiments the estimates of a uniform, constant Pennes perfusion parameter are approximately zero, and at 20 and 40 ml/min the average estimates increase with flow rate to 3.0 and 4.2 kg/m(3) /s, respectively. When Pennes perfusion parameter values are allowed to vary spatially, but remain temporally constant, BHTE temperature predictions are more accurate than when using spatially uniform, constant Pennes perfusion values, with reductions in RMSE values of up to 79%. Locations with large estimated perfusion values correspond to high flow regions of the kidney observed in T1 -weighted MR images. This novel, MRTI-based technique holds promise for improving understanding of thermal therapy biophysics

  15. Numerical simulations of blood flow in arterial bifurcation models

    NASA Astrophysics Data System (ADS)

    Seo, Taewon

    2013-08-01

    In the study, two different arterial bifurcation model geometries were used in the flow simulation. The model 1 is assumed the internal carotid artery (ICA) and the external carotid artery (ECA) branches of the bifurcation aligned in parallel to each other, while the model 2 is the typical carotid geometry. In the computation the Non-Newtonian behavior of blood was described using Carreau model. Generally, in the comparison between Newtonian and Non-Newtonian results good agreement was observed in the velocity profiles, while some discrepancies were found in the temporal wall shear stress (WSS) distributions as well as pressure profiles due to the shear thinning behavior. The temporal evolution of WSS periodically increases and decreases closely that of the inlet velocity waveform. It was also observed that the reversed flow region in the ICA of model 2 is 2.5 times larger than that of model 1. As a result, the variation of the flow characteristics can be dependent on the geometry as well as the arterial bifurcation geometry plays an important role in the development of atherosclerosis.

  16. Estimation of error limits for cerebral blood flow values obtained from xenon-133 clearance curves

    SciTech Connect

    Ryding, E.

    1989-02-01

    I provide the theoretical basis for an error calculus for measurements of cerebral blood flow using a freely diffusible tracer substance such as xenon-133. The use of the error calculus is exemplified by a study of the effect on the error margins in measurements of gray matter blood flow from flow level, relative weight of the gray matter compartment, and use of the earliest parts of the clearance curves. The clinical value of the error calculus is illustrated by its ability to separate different sources of measurement error. As a consequence, it is possible to optimize the method for blood flow calculation from the clearance curves, depending on the type of cerebral blood flow measurement. I show that if a true picture of the regional gray matter blood flow distribution is sought, the earliest part of the clearance curves should be used. This does, however, increase the error in the estimate of the average cerebral blood flow value.

  17. Theory to Predict Shear Stress on Cells in Turbulent Blood Flow

    PubMed Central

    Morshed, Khandakar Niaz; Bark Jr., David; Forleo, Marcio; Dasi, Lakshmi Prasad

    2014-01-01

    Shear stress on blood cells and platelets transported in a turbulent flow dictates the fate and biological activity of these cells. We present a theoretical link between energy dissipation in turbulent flows to the shear stress that cells experience and show that for the case of physiological turbulent blood flow: (a) the Newtonian assumption is valid, (b) turbulent eddies are universal for the most complex of blood flow problems, and (c) shear stress distribution on turbulent blood flows is possibly universal. Further we resolve a long standing inconsistency in hemolysis between laminar and turbulent flow using the theoretical framework. This work demonstrates that energy dissipation as opposed to bulk shear stress in laminar or turbulent blood flow dictates local mechanical environment of blood cells and platelets universally. PMID:25171175

  18. Renal blood flow distribution during E. coli endotoxin shock in dog.

    PubMed

    Kirkebø, A; Tyssebotn, I

    1980-04-01

    The effect of endotoxin on renal blood flow distribution was studied in anesthetized dogs. Renal blood flow was measured as hydrogen clearance by platinum electrodes placed in outer and in inner halves of cortex and by electromagnetic flowmeter. Intravenous injection of E. coli endotoxin, 3-5 mg/kg b. wt., promptly reduced arterial blood pressure (AP) and renal blood flow. After a transient increase for 45 min AP and renal blood flow declined to about 50% of the control 2 1/2-3 h after injection. The reduction in outer cortical blood flow (OCF) was not significantly different from the reduction in inner cortical blood flow (ICF). The hematocrit (Hct) increased from 40.1 +/- 3.8% to 54.6 +/- 8%, but mean renal vascular resistance did not change. Total plasma protein concentration was not significantly elevated. A marked local flow variability was observed in some periods during the phase of shock with declining AP and total renal blood flow at high Hct. Thus renal blood flow showed phasic changes, but the OCF/ICF ratio was not changed during endotoxin shock. Local blood flow instability was observed periodically at high Hct. PMID:6998257

  19. Improved engineering models for turbulent wall flows

    NASA Astrophysics Data System (ADS)

    She, Zhen-Su; Chen, Xi; Zou, Hong-Yue; Hussain, Fazle

    2015-11-01

    We propose a new approach, called structural ensemble dynamics (SED), involving new concepts to describe the mean quantities in wall-bounded flows, and its application to improving the existing engineering turbulence models, as well as its physical interpretation. First, a revised k - ω model for pipe flows is obtained, which accurately predicts, for the first time, both mean velocity and (streamwise) kinetic energy for a wide range of the Reynolds number (Re), validated by Princeton experimental data. In particular, a multiplicative factor is introduced in the dissipation term to model an anomaly in the energy cascade in a meso-layer, predicting the outer peak of agreeing with data. Secondly, a new one-equation model is obtained for compressible turbulent boundary layers (CTBL), building on a multi-layer formula of the stress length function and a generalized temperature-velocity relation. The former refines the multi-layer description - viscous sublayer, buffer layer, logarithmic layer and a newly defined bulk zone - while the latter characterizes a parabolic relation between the mean velocity and temperature. DNS data show our predictions to have a 99% accuracy for several Mach numbers Ma = 2.25, 4.5, improving, up to 10%, a previous similar one-equation model (Baldwin & Lomax, 1978). Our results promise notable improvements in engineering models.

  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. Face cooling with mist water increases cerebral blood flow during exercise: effect of changes in facial skin blood flow.

    PubMed

    Miyazawa, Taiki; Horiuchi, Masahiro; Ichikawa, Daisuke; Subudhi, Andrew W; Sugawara, Jun; Ogoh, Shigehiko

    2012-01-01

    Facial cooling (FC) increases cerebral blood flow (CBF) at rest and during exercise; however, the mechanism of this response remains unclear. The purpose of the present study was to test our hypothesis that FC causes facial vasoconstriction that diverts skin blood flow (SkBF(face)) toward the middle cerebral artery (MCA V(mean)) at rest and to a greater extent during exercise. Nine healthy young subjects (20 ± 2 years) underwent 3 min of FC by fanning and spraying the face with a mist of cold water (~4°C) at rest and during steady-state exercise [heart rate (HR) of 120 bpm]. We focused on the difference between the averaged data acquired from 1 min immediately before FC and last 1 min of FC. SkBF(face), MCA V(mean), and mean arterial blood pressure (MAP) were higher during exercise than at rest. As hypothesized, FC decreased SkBF(face) at rest (-32 ± 4%) and to a greater extent during exercise (-64 ± 10%, P = 0.012). Although MCA V(mean) was increased by FC (Rest, +1.4 ± 0.5 cm/s; Exercise, +1.4 ± 0.6 cm/s), the amount of the FC-evoked changes in MCA V(mean) at rest and during exercise differed among subjects. In addition, changes in MCA V(mean) with FC did not correlate with concomitant changes in SkBF(face) (r = 0.095, P = 0.709). MAP was also increased by FC (Rest, +6.2 ± 1.4 mmHg; Exercise, +4.2 ± 1.2 mmHg). These findings suggest that the FC-induced increase in CBF during exercise could not be explained only by change in SkBF(face). PMID:22934059

  2. 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.

  3. 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.

  4. A comparison of the Doppler spectra from human blood and artificial blood used in a flow phantom.

    PubMed

    Hoskins, P R; Loupas, T; McDicken, W N

    1990-01-01

    A comparison between the Doppler signals from human blood and artificial blood used in a flow phantom is described. The artificial blood used was a suspension of Sephadex particles in a glycerol solution. The Doppler power was measured as a function of Sephadex concentration and found to peak at a concentration of about 40% by volume. The power from blood was less by a factor of 150-250 than the power from Sephadex of a similar concentration. The first and second order statistics of the Doppler spectra from Sephadex were independent of particle concentration, and were very similar to those of spectra from blood. PMID:1691560

  5. A fluid dynamic analysis of a rotary blood pump for design improvement.

    PubMed

    Treichler, J; Rosenow, S E; Damm, G; Naito, K; Ohara, Y; Mizuguchi, K; Makinouchi, K; Takatani, S; Nosé, Y

    1993-09-01

    The proper design of a left ventricular assist device (LVAD) requires an understanding of the pump's fluid dynamic and biocompatible properties. A hydraulically efficient system minimizes the power required for pumping. Biocompatibility refers to the ability to pump blood with minimal hemolysis and thrombus formation. Typically, shear stresses below a threshold level will not damage blood significantly. A fluid dynamic analysis of a prototype centrifugal pump designed for use as an LVAD was performed to establish flow characteristics. A flow visualization technique using Amberlite particles suspended in a glycerin/water blood analogue was used. The system was illuminated with a 1 mm planar beam strobed helium-neon laser, and the results were recorded photographically. An analysis of photographs revealed laminar and turbulent flows with vortices within an illuminated plane in both the inlet and outlet port areas. From these data, velocity and shear stress profiles were generated that showed possible areas of improvement. It was concluded that the outlet port design could be improved by changing its angle and the continuity of its expansion. The inlet port could also be improved by smoothing the transition area between the inlet tube and the pump body to allow for gradual acceleration of the entering fluid. PMID:8240074

  6. CEREBRAL BLOOD FLOW AND METABOLISM IN ANXIETY AND ANXIETY DISORDERS

    PubMed Central

    Mathew, Roy J.

    1994-01-01

    Anxiety disorders are some of the commonest psychiatric disorders and anxiety commonly co-exists with other psychiatric conditions. Anxiety can also be a normal emotion. Thus, study of the neurobiological effects of anxiety is of considerable significance. In the normal brain, cerebral blood flow (CBF) and metabolism (CMR) serve as indices of brain function. CBF/CMR research is expected to provide new insight into alterations in brain function in anxiety disorders and other psychiatric disorders. Possible associations between stress I anxiety I panic and cerebral ischemia I stroke give additional significance to the effects of anxiety on CBF. With the advent of non-invasive techniques, study of CBF/CMR in anxiety disorders became easier. A large numbers of research reports are available on the effects of stress, anxiety and panic on CBF/CMR in normals and anxiety disorder patients. This article reviews the available human research on this topic. PMID:21743685

  7. Ultrasonic Doppler measurement of renal artery blood flow

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Implantable pulsed Doppler ultrasonic flowmeter development has resulted in designs for application to the aortas of dogs and humans, and to human renal and coronary arteries. A figure of merit was derived for each design, indicating the degree of its precision. An H-array design for transcutaneous observation of blood flow was developed and tested in vitro. Two other simplified designs for the same purpose obviate the need to determine vessel orientation. One of these will be developed in the next time period. Techniques for intraoperative use and for implantation have had mixed success. While satisfactory on large vessels, higher ultrasonic frequencies and alteration of transducer design are required for satisfactory operation of pulsed Doppler flowmeters with small vessels.

  8. Portable real time analysis system for regional cerebral blood flow

    SciTech Connect

    Tiernan, T.; Entine, G.; Stump, D.A.; Prough, D.S.

    1988-02-01

    A very portable, regional cerebral blood flow (rCBF) analysis instrument system suitable for use in the operating theater during surgery is under development. Cadmium telluride (CdTe) solid state radiation detectors, an 8086 based data acquisition and communications module and a DEC Microvax computer are used so that the instrument is very compact, yet has the computational power to provide real time data analysis in the clinical environment. The instrument is currently being used at Bowman Gray School of Medicine to study rCBF during cardiopulmonary bypass surgery (CPB). Preliminary studies indicate that monitoring rCBF during this surgical procedure may provide insights into the mechanism that causes a significant fraction of these patients to suffer post operative neuropsychological deficit.

  9. Effect of anxiety on cortical cerebral blood flow and metabolism

    SciTech Connect

    Gur, R.C.; Gur, R.E.; Resnick, S.M.; Skolnick, B.E.; Alavi, A.; Reivich, M.

    1987-04-01

    The relation between anxiety and cortical activity was compared in two samples of normal volunteers. One group was studied with the noninvasive xenon-133 inhalation technique for measuring cerebral blood flow (CBF) and the other with positron emission tomography (PET) using /sup 18/Flurodeoxyglucose (/sup 18/FDG) for measuring cerebral metabolic rates (CMR) for glucose. The inhalation technique produced less anxiety than the PET procedure, and for low anxiety subjects, there was a linear increase in CBF with anxiety. For higher anxiety subjects, however, there was a linear decrease in CBF with increased anxiety. The PET group manifested a linear decrease in CMR with increased anxiety. The results indicate that anxiety can have systematic effects on cortical activity, and this should be taken into consideration when comparing data from different procedures. They also suggest a physiologic explanation of a fundamental behavioral law that stipulates a curvilinear, inverted-U relationship between anxiety and performance.

  10. Cerebral blood flow in normal and abnormal sleep and dreaming

    SciTech Connect

    Meyer, J.S.; Ishikawa, Y.; Hata, T.; Karacan, I.

    1987-07-01

    Measurements of regional or local cerebral blood flow (CBF) by the xenon-133 inhalation method and stable xenon computerized tomography CBF (CTCBF) method were made during relaxed wakefulness and different stages of REM and non-REM sleep in normal age-matched volunteers, narcoleptics, and sleep apneics. In the awake state, CBF values were reduced in both narcoleptics and sleep apneics in the brainstem and cerebellar regions. During sleep onset, whether REM or stage I-II, CBF values were paradoxically increased in narcoleptics but decreased severely in sleep apneics, while in normal volunteers they became diffusely but more moderately decreased. In REM sleep and dreaming CBF values greatly increased, particularly in right temporo-parietal regions in subjects experiencing both visual and auditory dreaming.

  11. Cerebral blood flow changes during vagus nerve stimulation for depression.

    PubMed

    Conway, Charles R; Sheline, Yvette I; Chibnall, John T; George, Mark S; Fletcher, James W; Mintun, Mark A

    2006-03-31

    Positron emission tomography (PET oxygen-15 labeled water or PET [15O]H2O) was used to identify changes in regional cerebral blood flow (rCBF) in response to acute vagus nerve stimulation (VNS) in four subjects with treatment-resistant major depression (TRMD). Four 90-s PET [15O]H2O scans were performed on each subject in an off-on sequence (2 VNS de-activated; 2 VNS activated). PET images were aligned, normalized for global uptake, and resampled to standard atlas space. Statistical t-images were used to evaluate change. VNS-induced increases in rCBF were found in the bilateral orbitofrontal cortex, bilateral anterior cingulate cortex, and right superior and medial frontal cortex. Decreases were found in the bilateral temporal cortex and right parietal area. Regions of change were consistent with brain structures associated with depression and the afferent pathways of the vagus nerve. PMID:16510266

  12. Cerebral blood flow asymmetries in headache-free migraineurs

    SciTech Connect

    Levine, S.R.; Welch, K.M.; Ewing, J.R.; Joseph, R.; D'Andrea, G.

    1987-11-01

    Regional cerebral blood flow (rCBF) asymmetries were studied in controls and patients with common and classic/complicated migraine using /sup 133/Xe inhalation with 8 homologously situated external collimators over each cerebral hemisphere. Migraine patients as a group more frequently had posterior rCBF asymmetries than controls (p less than 0.03). Although there were no differences in the number of anterior rCBF asymmetries, migraine patients had 2 or more asymmetric probe pairs more often than controls (p less than 0.02). The posterior rCBF asymmetries, consistent with the site of activation of many migraine attacks, may be related to more labile control of the cerebral circulation.

  13. The Utility of Cerebral Blood Flow Assessment in TBI.

    PubMed

    Akbik, Omar S; Carlson, Andrew P; Krasberg, Mark; Yonas, Howard

    2016-08-01

    Over the past few decades, intracranial monitoring technologies focused on treating and preempting secondary injury after traumatic brain injury (TBI) have experienced considerable growth. A physiological measure fundamental to the management of these patients is cerebral blood flow (CBF), which may be determined directly or indirectly. Direct measurement has proven difficult previously; however, invasive and non-invasive CBF monitors are now available. This article reviews the history of CBF measurements in TBI as well as the role of CBF in pathologies associated with TBI, such as cerebral autoregulation, hyperemia, and cortical spreading depression. The limitations of various CBF monitors are reviewed in order to better understand their role in TBI management. PMID:27315250

  14. Neural control of adrenal medullary and cortical blood flow during hemorrhage

    SciTech Connect

    Breslow, M.J.; Jordan, D.A.; Thellman, S.T.; Traystman, R.J.

    1987-03-01

    Hemorrhagic hypotension produces an increase in adrenal medullary blood flow and a decrease in adrenal cortical blood flow. To determine whether changes in adrenal blood flow during hemorrhage are neurally mediated, the authors compared blood flow responses following adrenal denervation (splanchnic nerve section) with changes in the contralateral, neurally intact adrenal. Carbonized microspheres labeled with /sup 153/Gd, /sup 114/In, /sup 113/Sn, /sup 103/Ru, /sup 95/Nb or /sup 46/Se were used. Blood pressure was reduced and maintained at 60 mmHg for 25 min by hemorrhage into a pressurized bottle system. Adrenal cortical blood flow decreased to 50% of control with hemorrhage in both the intact and denervated adrenal. Adrenal medullary blood flow increased to four times control levels at 15 and 25 min posthemorrhage in the intact adrenal, but was reduced to 50% of control at 3, 5, and 10 min posthemorrhage in the denervated adrenal. In a separate group of dogs, the greater splanchnic nerve on one side was electrically stimulated at 2, 5, or 15 Hz for 40 min. Adrenal medullary blood flow increased 5- to 10-fold in the stimulated adrenal but was unchanged in the contralateral, nonstimulated adrenal. Adrenal cortical blood flow was not affected by nerve stimulation. They conclude that activity of the splanchnic nerve profoundly affects adrenal medullary vessels but not adrenal cortical vessels and mediates the observed increase in adrenal medullary blood flow during hemorrhagic hypotension.

  15. A new approach to blood flow simulation in vascular networks.

    PubMed

    Tamaddon, Houman; Behnia, Mehrdad; Behnia, Masud; Kritharides, Leonard

    2016-01-01

    A proper analysis of blood flow is contingent upon accurate modelling of the branching pattern and vascular geometry of the network of interest. It is challenging to reconstruct the entire vascular network of any organ experimentally, in particular the pulmonary vasculature, because of its very high number of vessels, complexity of the branching pattern and poor accessibility in vivo. The objective of our research is to develop an innovative approach for the reconstruction of the full pulmonary vascular tree from available morphometric data. Our method consists of the use of morphometric data on those parts of the pulmonary vascular tree that are too small to reconstruct by medical imaging methods. This method is a three-step technique that reconstructs the entire pulmonary arterial tree down to the capillary bed. Vessels greater than 2 mm are reconstructed from direct volume and surface analysis using contrast-enhanced computed tomography. Vessels smaller than 2 mm are reconstructed from available morphometric and distensibility data and rearranged by applying Murray's laws. Implementation of morphometric data to reconstruct the branching pattern and applying Murray's laws to every vessel bifurcation simultaneously leads to an accurate vascular tree reconstruction. The reconstruction algorithm generates full arterial tree topography down to the first capillary bifurcation. Geometry of each order of the vascular tree is generated separately to minimize the construction and simulation time. The node-to-node connectivity along with the diameter and length of every vessel segment is established and order numbers, according to the diameter-defined Strahler system, are assigned. In conclusion, the present model provides a morphological foundation for future analysis of blood flow in the pulmonary circulation. PMID:26195135

  16. Bang-bang Model for Regulation of Local Blood Flow

    PubMed Central

    Golub, Aleksander S.; Pittman, Roland N.

    2013-01-01

    The classical model of metabolic regulation of blood flow in muscle tissue implies the maintenance of basal tone in arterioles of resting muscle and their dilation in response to exercise and/or tissue hypoxia via the evoked production of vasodilator metabolites by myocytes. A century-long effort to identify specific metabolites responsible for explaining active and reactive hyperemia has not been successful. Furthermore, the metabolic theory is not compatible with new knowledge on the role of physiological radicals (e.g., nitric oxide, NO, and superoxide anion, O2−) in the regulation of microvascular tone. We propose a model of regulation in which muscle contraction and active hyperemia are considered the physiologically normal state. We employ the “bang-bang” or “on/off” regulatory model which makes use of a threshold and hysteresis; a float valve to control the water level in a tank is a common example of this type of regulation. Active bang-bang regulation comes into effect when the supply of oxygen and glucose exceeds the demand, leading to activation of membrane NADPH oxidase, release of O2− into the interstitial space and subsequent neutralization of the interstitial NO. Switching arterioles on/off when local blood flow crosses the threshold is realized by a local cell circuit with the properties of a bang-bang controller, determined by its threshold, hysteresis and dead-band. This model provides a clear and unambiguous interpretation of the mechanism to balance tissue demand with a sufficient supply of nutrients and oxygen. PMID:23441827

  17. 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.

  18. Blood viscoelasticity measurement using steady and transient flow controls of blood in a microfluidic analogue of Wheastone-bridge channel

    PubMed Central

    Jun Kang, Yang; Lee, Sang-Joon

    2013-01-01

    Accurate measurement of blood viscoelasticity including viscosity and elasticity is essential in estimating blood flows in arteries, arterials, and capillaries and in investigating sub-lethal damage of RBCs. Furthermore, the blood viscoelasticity could be clinically used as key indices in monitoring patients with cardiovascular diseases. In this study, we propose a new method to simultaneously measure the viscosity and elasticity of blood by simply controlling the steady and transient blood flows in a microfluidic analogue of Wheastone-bridge channel, without fully integrated sensors and labelling operations. The microfluidic device is designed to have two inlets and outlets, two side channels, and one bridge channel connecting the two side channels. Blood and PBS solution are simultaneously delivered into the microfluidic device as test fluid and reference fluid, respectively. Using a fluidic-circuit model for the microfluidic device, the analytical formula is derived by applying the linear viscoelasticity model for rheological representation of blood. First, in the steady blood flow, the relationship between the viscosity of blood and that of PBS solution (μBlood/μPBS) is obtained by monitoring the reverse flows in the bridge channel at a specific flow-rate rate (QPBSSS/QBloodL). Next, in the transient blood flow, a sudden increase in the blood flow-rate induces the transient behaviors of the blood flow in the bridge channel. Here, the elasticity (or characteristic time) of blood can be quantitatively measured by analyzing the dynamic movement of blood in the bridge channel. The regression formula (ABlood (t) = Aα + Aβ exp [−(t − t0)/λBlood]) is selected based on the pressure difference (ΔP = PA − PB) at each junction (A, B) of both side channels. The characteristic time of bloodBlood) is measured by analyzing the area (ABlood) filled with blood in the bridge channel by selecting an appropriate detection window in the

  19. 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

    SciTech Connect

    Randall, N.J.; Beard, R.W.; Sutherland, I.A.; Figueroa, J.P.; Drost, C.J.; Nathanielsz, P.W.

    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 have value in the investigation of blood flow patterns in various clinical situations such as the pelvic pain syndrome and early pregnancy.

  20. Limb blood flow - Rest and heavy exercise in sitting and supine positions in man

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Montgomery, L. D.; Brock, P. J.; Van Beaumont, W.

    1979-01-01

    The objectives of the study were twofold: (1) to determine the effect of body position (hydrostatic pressure) on total blood flow in active and passive limbs at rest and after severe exercise; and (2) to further evaluate the impedance technique for measurement of blood flow. To this end, the effect of body position on the redistribution of total blood flow in active (leg) and passive (forearm) limbs during exercise was determined by measuring total limb impedance (blood flow) in five male and one female subjects in sitting and supine positions with a modified Beckman BR-100 rheograph. The results show that, at rest and after exercise, the supine position induces significantly greater flows in the leg but not in the forearm. With severe exercise, blood flows are increased in both passive and active limbs, so that there is probably no net transfer of blood volume from passive to active muscles. The advantages of the impedance technique over other methods are stressed.

  1. Bone and bone-marrow blood flow in chronic granulocytic leukemia and primary myelofibrosis

    SciTech Connect

    Lahtinen, R.; Lahtinen, T.; Romppanen, T.

    1982-03-01

    Blood flow in hematopoietic bone marrow and in nonhematopoietic bone has been measured with a Xe-133 washout method in 20 patients with chronic granulocytic leukemia (CGL) and in seven with primary myelofibrosis. Age-matched healthy persons served as controls. Bone-marrow blood flow in CGL was dependent upon the phase of the disease. In the metamorphosis phase, bone-marrow blood flow was high compared with that in the well-controlled phase. Apart from the initial phase, the mean values for bone blood flow in CGL were increased compared with the values of the healthy controls. In myelofibrosis the bone blood flow was also increased. Bone-marrow blood flow in these diseases was dependent upon the cellularity of bone marrow as measured morphometrically.

  2. Chronic intestinal ischaemia: measurement of the total splanchnic blood flow.

    PubMed

    Zacho, Helle D

    2013-04-01

    A redundant collateral network between the intestinal arteries is present at all times. In case of ischaemia in the gastrointestinal tract, the collateral blood supply can develop further, thus accommodating the demand for oxygen even in the presence of significant stenosis or occlusion of the intestinal arteries without clinical symptoms of intestinal ischaemia. Symptoms of ischemia develop when the genuine and collateral blood supply no longer can accommodate the need for oxygen. Atherosclerosis is the most common cause of obliteration in the intestinal arteries. In chronic intestinal ischaemia (CII), the fasting splanchnic blood flow (SBF) is sufficient, but the postprandial increase in SBF is inadequate and abdominal pain will therefore develop in relation to food intake causing the patient to eat smaller meals at larger intervals with a resulting weight loss. Traditionally, the CII-diagnosis has exclusively been based upon morphology (angiography) of the intestinal arteries; however, substantial discrepancies between CII-symptoms and the presence of atherosclerosis/stenosis in the intestinal arteries have been described repeatedly in the literature impeding the diagnosis of CII. This PhD thesis explores a method to determine the total SBF and its potential use as a diagnostic tool in patients suspected to suffer from CII. The SBF can be measured using a continuous infusion of a tracer and catheterisation of a hepatic vein and an artery. By measuring the SBF before and after a standard meal it is possible to assess the ability or inability to enhance the SBF and thereby diagnosing CII. In Study I, measurement of SBF was tested against angiography in a group of patients suspected to suffer from CII due to pain and weight loss. A very good agreement between the postprandial increase in SBF and angiography was found. The method was validated against a well-established method independent of the hepatic extraction of tracer using pAH in a porcine model (study II

  3. Effect of retransfusion after hemorrhagic hypotension on intrarenal distribution of blood flow in dogs

    PubMed Central

    Carriere, Serge; Daigneault, Bernard

    1970-01-01

    Hemorrhagic hypotension in anesthetized dogs produces a marked decrease of the cortical blood flow, whereas the medullary blood flow is well preserved. These animals were maintained at blood pressures of 50 mm Hg during a 3 hr period after which their blood pressures were restored by the reinfusion of blood or dextran, or both. In the first group of animals, the reinfusion of blood reestablished the blood pressure to control values, but the cortical blood flow was still nonuniformly decreased whereas the medullary blood flow appeared to be increased. In the second group of animals, phenoxybenzamine failed to protect the kidney completely since after blood reinfusion, the same anomalies described for the preceding group were found in 7 out of 10 dogs. The animals of the third group were reinfused with 50% of the shed blood and 10 ml/kg of a 10 g/100 ml solution of low molecular weight dextran. The modifications of the intrarenal distribution of the blood flow were less marked in this group although the blood flow rate of the inner cortex and the outer medulla was always elevated under these conditions. The reinfusion of low molecular weight dextran alone (20 ml/kg of a 10 g/100 ml solution) restored the blood pressure to levels slightly lower than those observed under control conditions but reestablished a normal pattern of intrarenal blood flow. The reinfusion of high molecular weight dextran was inefficient in correcting completely the anomalies of the renal blood flow. Mechanisms such as the increased sympathetic tone, the liberation of angiotensin, and the intravascular cellular aggregation could possibly account for the persisting anomalies of the renal circulation after reinfusion and are discussed. Images PMID:5480847

  4. Cerebral blood flow determination within the first 8 hours of cerebral infarction using stable xenon-enhanced computed tomography

    SciTech Connect

    Hughes, R.L.; Yonas, H.; Gur, D.; Latchaw, R.

    1989-06-01

    Cerebral blood flow mapping with stable xenon-enhanced computed tomography (Xe/CT) was performed in conjunction with conventional computed tomography (CT) within the first 8 hours after the onset of symptoms in seven patients with cerebral infarction. Six patients had hemispheric infarctions, and one had a progressive brainstem infarction. Three patients with very low (less than 10 ml/100 g/min) blood flow in an anatomic area appropriate for the neurologic deficit had no clinical improvement by the time of discharge from the hospital; follow-up CT scans of these three patients confirmed infarction in the area of very low blood flow. Three patients with moderate blood flow reductions (15-45 ml/100 g/min) in the appropriate anatomic area had significant clinical improvement from their initial deficits and had normal follow-up CT scans. One patient studied 8 hours after stroke had increased blood flow (hyperemia) in the appropriate anatomic area and made no clinical recovery.

  5. Physiological non-Newtonian blood flow through single stenosed artery

    NASA Astrophysics Data System (ADS)

    Mamun, Khairuzzaman; Rahman, Mohammad Matiur; Akhter, Most. Nasrin; Ali, Mohammad

    2016-07-01

    A numerical simulation to investigate the Non-Newtonian modelling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Where the physiological waveform is performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 96 to 800. Low Reynolds number k - ω model is used as governing equation. The investigation has been carried out to characterize tw