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Sample records for clitoral blood flow

  1. Clitoral blood flow increases following vaginal pressure stimulation.

    PubMed

    Lavoisier, P; Aloui, R; Schmidt, M H; Watrelot, A

    1995-02-01

    The vascular responses of clitoral arteries to vaginal pressure stimulation in 10 volunteer women were evaluated by Doppler ultrasonography. Pressure stimulations (20-160 mm Hg) along the lower third of the vagina increased blood velocity and flow into clitoral arteries in 9 of the 10 women. The latency and duration of the Doppler responses ranged from 0.1 to 1.6 sec and from 3.2 to 9.5 sec, respectively, and the response was associated with a blood flow increase of 4 to 11 times the baseline prestimulation level. This response parallels that recorded in the cavernous arteries in men when a similar range of pressure stimulations are applied to the glans penis. Similar responses evoked in the male and female suggest a sexual synergy that may occur during intercourse in that such physiological responses and reflexes may be reciprocally reinforced.

  2. Sexual Response in Women with Type 1 Diabetes Mellitus: A Controlled Laboratory Study Measuring Vaginal Blood Flow and Subjective Sexual Arousal.

    PubMed

    Both, Stephanie; Ter Kuile, Moniek; Enzlin, Paul; Dekkers, Olaf; van Dijk, Marieke; Weijenborg, Philomeen

    2015-08-01

    Previous studies have indicated that women with diabetes mellitus are at higher risk to develop sexual dysfunctions. In the current study, we hypothesized that lower genital arousal response-as a consequence of diabetes-related damage to nerves and blood vessels-might play a part in these higher prevalence rates. Vaginal blood flow, subjective sexual response, and clitoral sensitivity were compared between women with diabetes and healthy controls, and associations with diabetes complications were investigated. In pre- and postmenopausal women with type 1 diabetes (n = 42) and healthy controls (n = 46), vaginal blood flow was measured as vaginal pulse amplitude (VPA). VPA was assessed at rest, during erotic film viewing, and during vibrotactile clitoral stimulation. Subjective sexual arousal was measured using a questionnaire. Clitoral sensitivity was assessed by a vibration perception test. Data on diabetes complications were obtained from medical records, and neuropathy was assessed by quantitative sensory testing. VPA, subjective sexual arousal, and clitoral sensitivity were not significantly different between women with diabetes and controls. Nevertheless, women with diabetes who had retinopathy showed significantly lower VPA than women without retinopathy, and women with diabetes who had neuropathy showed significantly higher sensation thresholds for vibrotactile clitoral stimulation. The results do not support the hypothesis of a disrupted genital arousal response in women with diabetes. However, the observed associations between retinopathy and vaginal blood flow, and between neuropathy and clitoral sensitivity, suggest that diabetes-related complications might adversely affect the physiological basis of female sexual response. PMID:26054485

  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 vital organs. ... brain, liver, kidneys, stomach, and muscles, including the heart muscle itself. At the same time, the veins ...

  4. Cavernous haemangioma mimicking as clitoral hypertrophy.

    PubMed

    Nayyar, Sajid; Liaqat, Naeem; Sultan, Nayyar; Dar, Sajid Hameed

    2014-01-01

    Haemangioma is the most common benign neoplasm of infantile age. It is most commonly located in head and neck region, trunk and extremities but very rarely it can be located at clitoris. However, it is very important to differentiate clitoral haemangioma from enlargement of the clitoris secondary to androgen excess. Only four cases of clitoromegaly caused by cavernous haemangioma have been reported in the literature so far. Herein, we report our experience with a 10-year-old girl who presented with clitoromegaly and normal hormonal assay that turned out to be clitoral cavernous haemangioma after histopathological examination of the clitoral mass.

  5. 21 CFR 884.5970 - Clitoral engorgement device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Clitoral engorgement device. 884.5970 Section 884.5970 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... § 884.5970 Clitoral engorgement device. (a) Identification. A clitoral engorgement device is designed...

  6. Blood Flow in Arteries

    NASA Astrophysics Data System (ADS)

    Ku, David N.

    Blood flow in arteries is dominated by unsteady flow phenomena. The cardiovascular system is an internal flow loop with multiple branches in which a complex liquid circulates. A nondimensional frequency parameter, the Womersley number, governs the relationship between the unsteady and viscous forces. Normal arterial flow is laminar with secondary flows generated at curves and branches. The arteries are living organs that can adapt to and change with the varying hemodynamic conditions. In certain circumstances, unusual hemodynamic conditions create an abnormal biological response. Velocity profile skewing can create pockets in which the direction of the wall shear stress oscillates. Atherosclerotic disease tends to be localized in these sites and results in a narrowing of the artery lumena stenosis. The stenosis can cause turbulence and reduce flow by means of viscous head losses and flow choking. Very high shear stresses near the throat of the stenosis can activate platelets and thereby induce thrombosis, which can totally block blood flow to the heart or brain. Detection and quantification of stenosis serve as the basis for surgical intervention. In the future, the study of arterial blood flow will lead to the prediction of individual hemodynamic flows in any patient, the development of diagnostic tools to quantify disease, and the design of devices that mimic or alter blood flow. This field is rich with challenging problems in fluid mechanics involving three-dimensional, pulsatile flows at the edge of turbulence.

  7. 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

  8. 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.

  9. 21 CFR 884.5970 - Clitoral engorgement device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Clitoral engorgement device. 884.5970 Section 884.5970 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES OBSTETRICAL AND GYNECOLOGICAL DEVICES Obstetrical and Gynecological Therapeutic Devices § 884.5970 Clitoral engorgement device....

  10. Modelling pulmonary blood flow

    PubMed Central

    Tawhai, Merryn H.; Burrowes, Kelly S.

    2008-01-01

    Computational model analysis is a method that has been used widely to understand and interpret complexity of interactions in the pulmonary system. Pulmonary blood transport is a multi-scale phenomenon that involves scale-dependent structure and function, therefore requiring different model assumptions for the microcirculation and the arterial or venous flows. The blood transport systems interact with the surrounding lung tissue, and are dependent on hydrostatic pressure gradients, control of vasoconstriction, and the topology and material composition of the vascular trees. This review focuses on computational models that have been developed to study the different mechanisms contributing to regional perfusion of the lung. Different models for the microcirculation and the pulmonary arteries are considered, including fractal approaches and anatomically-based methods. The studies that are reviewed illustrate the different complementary approaches that can be used to address the same physiological question of flow heterogeneity. PMID:18434260

  11. Disorders of cochlear blood flow.

    PubMed

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

    2003-09-01

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

  12. 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…

  13. 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.

  14. 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)

  15. Blood Flow, Slip, and Viscometry

    PubMed Central

    Nubar, Yves

    1971-01-01

    The viscosity of blood, measured by the usual viscometers in which slip is not considered, is found to be flow dependent, varying markedly with shear rate, pressure gradient, and vessel diameter in the lower ranges of these factors. The study postulates, on grounds thought reasonable, that slip may be present in blood flow, as a function of the nature of the wall surfaces, shear stress at the wall, and relative cell volume (RCV) adjacent to the wall. It presumes that blood possesses a specific, flow-independent viscosity, and determines theoretically the viscosity indications of viscometers if blood slipped in the instruments. The study shows that if the slip function is of a certain plausible form, these viscosity indications would exhibit a flow dependence of much the same pattern as the actual indications supplied by the usual viscometers. The slip postulate permits, therefore, an interpretation of the “anomalous” flow behavior of blood, dispensing with the prevailing assumption of an ad hoc variability of its viscosity with flow factors. To the extent that viscometric data for blood may be representative of other non-newtonian fluids, the slip postulate may be applicable to these fluids. PMID:5573368

  16. 21 CFR 884.5970 - Clitoral engorgement device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Clitoral engorgement device. 884.5970 Section 884.5970 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... apply a vacuum to the clitoris. It is intended for use in the treatment of female sexual...

  17. 21 CFR 884.5970 - Clitoral engorgement device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Clitoral engorgement device. 884.5970 Section 884.5970 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... apply a vacuum to the clitoris. It is intended for use in the treatment of female sexual...

  18. 21 CFR 884.5970 - Clitoral engorgement device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Clitoral engorgement device. 884.5970 Section 884.5970 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... apply a vacuum to the clitoris. It is intended for use in the treatment of female sexual...

  19. 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.

  20. Dorsal clitoral nerve injury following transobturator midurethral sling

    PubMed Central

    Moss, Chailee F; Damitz, Lynn A; Gracely, Richard H; Mintz, Alice C; Zolnoun, Denniz A; Dellon, A Lee

    2016-01-01

    Introduction Transobturator slings can be successfully used to treat stress urinary incontinence and improve quality of life through a minimally invasive vaginal approach. Persistent postoperative pain can occur and pose diagnostic and therapeutic dilemmas. Following a sling procedure, a patient complained of pinching clitoral and perineal pain. Her symptoms of localized clitoral pinching and pain became generalized over the ensuing years, eventually encompassing the entire left vulvovaginal region. Aim The aim of this study was to highlight the clinical utility of conventional pain management techniques used for the evaluation and management of patients with postoperative pain following pelvic surgery. Methods We described a prototypical patient with persistent pain in and around the clitoral region complicating the clinical course of an otherwise successful sling procedure. We specifically discussed the utility of bedside sensory assessment techniques and selective nerve blocks in the evaluation and management of this prototypical patient. Results Neurosensory assessments and a selective nerve block enabled us to trace the source of the patient’s pain to nerve entrapment along the dorsal nerve of the clitoris. We then utilized a nerve stimulator-guided hydrodissection technique to release the scar contracture Conclusion This case demonstrates that the dorsal nerve of the clitoris is vulnerable to injury directly and/or indirectly. Assimilation of a time-honored pain management construct for the evaluation and management of patients’ pain may improve outcomes while obviating the need for invasive surgery. PMID:27729812

  1. [Clitoral epidermoid cyst causing clitoromegaly. A rare case report].

    PubMed

    Masson, V; Fiquet François, C; Rausky, J; Mazouz Dorval, S; Revol, M

    2014-04-01

    Clitoromegaly is uncommon. It is mostly congenital, hormonal or tumoral. Epidermoid cyst is rare. It can be the consequence of trauma, but in some situations the cyst can be non-traumatic. We report the case of a 53-year-old woman who presented a misdiagnosis of clitoromegaly due to hormonal condition. Surgical exploration has highlighted an epidermoid cyst. This observation underlines the importance to evoke a cystic origin for clitoral hypertrophy and encourages us to propose imaging (ultrasound, MRI) in case of etiological doubt. The preoperative diagnosis must be made to preserve vascularization and innervation of the clitoris.

  2. Clitoral and labial sizes in women wıth PCOS.

    PubMed

    Köşüş, A; Kamalak, Z; Köşüş, N; Hizli, D; Eser, A

    2016-01-01

    The aim of this study was to examine the external genital features in Turkish women with polycystic ovary syndrome (PCOS). Thirty-two newly diagnosed PCOS cases and 35 healthy women were included the study. All women underwent a thorough gynaecological examination. Clitoral length, and labia minora length and width were recorded. The groups were compared for features of external genital structures. Clitoral and labial lengths were significantly higher in PCOS group. There was a strong correlation between clitoral length and modified Ferriman-Gallwey score. The most effective predictor of PCOS was found to be clitoral length. Clitoral length alone predicted 99.9% of PCOS patients. There were some subclinical genital changes in women with PCOS. These changes in PCOS patients may be a sign of hyperandrogenism and might have diagnostic value in indistinct cases.

  3. Some potential blood flow experiments for space

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  4. 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).

  5. Blood Cell Interactions and Segregation in Flow

    PubMed Central

    Munn, Lance L.; Dupin, Michael M.

    2009-01-01

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

  6. 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.

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

    PubMed Central

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

    2015-01-01

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

  8. 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.

  9. Vascular structure determines pulmonary blood flow distribution.

    PubMed

    Hlastala, M P; Glenny, R W

    1999-10-01

    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.

  10. 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

  11. 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.

  12. 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.

  13. Blood flow and permeability in microvessels

    NASA Astrophysics Data System (ADS)

    Sugihara-Seki, Masako; Fu, Bingmei M.

    2005-07-01

    The mechanics of blood flow in microvessels and microvessel permeability are reviewed. In the first part, characteristics of blood flow in vivo and in vitro are described from a fluid-mechanical point of view, and mathematical models for blood flow in microvessels are presented. Possible causes of the increased flow resistance obtained in vivo compared to in vitro are examined, including the effects of irregularities of vessel lumen, the presence of endothelial surface glycocalyx and white blood cells. In the second part, the ultrastructural pathways and mechanisms whereby endothelial cells and the clefts between the cells modulate microvessel permeability to water and solutes are introduced. Previous and current models for microvessel permeability to water and solutes are reviewed. These models examine the role of structural components of interendothelial cleft, such as junction strands and surface glycocalyx, in the determination of water and solute transport across the microvessel walls. Transport models in the tissue space surrounding the microvessel are also described.

  14. 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.

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. Patient Satisfaction of Surgical Treatment of Clitoral Phimosis and Labial Adhesions Caused by Lichen Sclerosus

    PubMed Central

    King, Michelle; Rieff, Mollie; Krapf, Jill; Goldstein, Andrew T.

    2015-01-01

    Abstract Introduction Lichen sclerosus (LS) is a chronic inflammatory dermatosis, usually affecting the anogenital skin in women. This chronic inflammation can cause scarring of genitalia including narrowing of the introitus and phimosis of the clitoris. These architectural changes can lead to recurrent tearing during intercourse (vulvar granuloma fissuratum) and decreased clitoral sensation. Surgical correction of vulvar granuloma fissuratum (VGF) and clitoral phimosis can be performed, but there is little data on the patient satisfaction and complications following these surgical procedures. Aim To evaluate patient experience and outcomes in women undergoing surgical correction of scarring caused by anogenital LS. Methods A retrospective chart review of patients at a vulvar disorders clinic was performed to identify women who had undergone surgical correction of clitoral phimosis or lysis of vulvar adhesions for VGF due to LS. Twenty‐eight women were contacted via telephone between 4 and 130 months postoperatively. An eight‐question survey was used to determine patient experience and outcomes. Main Outcome Measures All participants completed an eight‐question survey to evaluate patient satisfaction with the surgery, effects on clitoral sensation, orgasm and pain with intercourse, postoperative symptoms or complications, and the presence of recurrent vulvar scarring. Results Participants reported that they were either very satisfied (44%) or satisfied (40%) with the procedure. Of the women who experienced decreased clitoral sensation prior to surgery, 75% endorsed increased clitoral sensitivity postoperatively. Of the women who had dyspareunia prior to surgery, the majority of women reported having pain‐free sex (33%) or improved but not completely pain‐free sex (58%) after surgery. There were no complications or symptoms made worse by the surgical procedures. Conclusions This study shows high patient satisfaction and low complication risk associated

  20. 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.…

  1. The Role of Clitoral Anatomy in Female to Male Sex Reassignment Surgery

    PubMed Central

    2014-01-01

    Introduction. Controversies on clitoral anatomy and its role in female sexual function still make clitoral reconstructive surgery very challenging. We evaluated the role of clitoral anatomic features in female to male sex reassignment surgery. Material and Methods. The study included 97 female transsexuals, aged from 18 to 41 years, who underwent single stage metoidioplasty between March 2008 and January 2013. The operative technique involved vaginectomy, the release of clitoral ligaments and urethral plate, urethroplasty by combining buccal mucosa graft and genital flaps, and scrotoplasty with insertion of testicle prostheses. Postoperative questionnaire was used to evaluate aesthetic, functional, and sexual outcome. Results. The mean followup was 30 months. The mean length of the neophallus was 7 cm, compared to mean preoperative length of the hypertrophied clitoris of 3.3 cm. Complications occurred in 27.84% of all patients, related mostly to urethroplasty. Voiding while standing was achieved in all cases. None of the patients had problems in sexual arousal, masturbation, or orgasms. Conclusion. Accurate knowledge of the clitoral anatomy, physiology, and neurovascular supply is crucial for a successful outcome of female to male sex reassignment surgery. Our approach appears to ensure overall satisfaction and high quality of sexual life. PMID:24982953

  2. In vivo determination of bone blood flow

    SciTech Connect

    Rosenthal, M.S.; De Luca, P.M. Jr.; Pearson, D.W.; Nickles, R.J.

    1984-01-01

    Quantitative measurement of bone blood flow is vital to understand the hemodynamics of bone systems especially in the study of asceptic bone necroses. These ''silent bends'' result from micro-emboli in femoral arterioles from small nitrogen bubbles released from lipids during a diver's ascent. A technique to determine bone blood flow in vivo has been developed by measuring the rate of inert gas washout of Ar-41 (t /sub 1/2/ = 1.83 h, E = 1293 keV) from the bone mineral matrix. Argon gas is formed in vivo by neutron activation of Ca-44 using 14.3 MeV neutrons, following the reaction Ca-44(n, ..cap alpha..)Ar-41. The blood flow in the irradiated bone is determined by measuring the clearance rate of Ar-41 using gamma-ray spectroscopy. To date, measurements have been made on dead and living rats (weight 300g). The results indicated that in the no-flow situation the clearance rate is consistent with the physical half-life of Ar-41, while for the live rats the clearance rate for argon is dependent on the flow of blood in the bone. The observed clearance times correspond to flows greater than 3 ml of blood per 100 ml of argon distribution volume/min (F/pV), with the bone-blood partition coefficient for argon approximately one. In addition, measurements of the partitioning of argon and other gases with bone have been measured in order to understand blood-bone systems more fully.

  3. 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.

  4. Luteal blood flow and luteal function

    PubMed Central

    Takasaki, Akihisa; Tamura, Hiroshi; Taniguchi, Ken; Asada, Hiromi; Taketani, Toshiaki; Matsuoka, Aki; Yamagata, Yoshiaki; Shimamura, Katsunori; Morioka, Hitoshi; Sugino, Norihiro

    2009-01-01

    Background Blood flow in the corpus luteum (CL) is associated with luteal function. The present study was undertaken to investigate whether luteal function can be improved by increasing CL blood flow in women with luteal phase defect (LFD). Methods Blood flow impedance in the CL was measured by transvaginal color-pulsed-Doppler-ultrasonography and was expressed as a resistance index (RI). The patients with both LFD [serum progesterone (P) concentrations < 10 ng/ml during mid-luteal phase] and high CL-RI (≥ 0.51) were given vitamin-E (600 mg/day, n = 18), L-arginine (6 g/day, n = 14) as a potential nitric oxide donor, melatonin (3 mg/day, n = 13) as an antioxidant, or HCG (2,000 IU/day, n = 10) during the subsequent menstrual cycle. Results In the control group (n = 11), who received no medication to increase CL blood flow, only one patient (9%) improved in CL-RI and 2 patients (18%) improved in serum P. Vitamin-E improved CL-RI in 15 patients (83%) and improved serum P in 12 patients (67%). L-arginine improved CL-RI in all the patients (100%) and improved serum P in 10 patients (71%). HCG improved CL-RI in all the patients (100%) and improved serum P in 9 patients (90%). Melatonin had no significant effect. Conclusion Vitamin-E or L-arginine treatment improved luteal function by decreasing CL blood flow impedance. CL blood flow is a critical factor for luteal function. PMID:19144154

  5. 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…

  6. 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.

  7. Effects of Dorzolamide on Choroidal Blood Flow, Ciliary Blood Flow, and Aqueous Production in Rabbits

    PubMed Central

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

    2015-01-01

    Purpose To determine the effects of topical dorzolamide (a carbonic anhydrase inhibitor) on choroidal and ciliary blood flow and the relationship between ciliary blood flow and aqueous flow. Methods The experiments were performed in four groups of pentobarbital-anesthetized rabbits treated with topical dorzolamide (2%, 50 μL). In all groups, intraocular pressure (IOP) and mean arterial pressure (MAP) at the eye level were measured continuously by direct cannulation. In group 1, aqueous flow was measured by fluorophotometry before and after dorzolamide treatment. In group 2, aqueous flow was measured after dorzolamide at normal MAP and while MAP was held constant at 80, 55, or 40 mm Hg with occluders on the aorta and vena cava. In group 3, the same MAP levels were used, and ciliary blood flow was measured transsclerally by laser Doppler flowmetry (LDF). In group 4, choroidal blood flow was measured by LDF with the probe tip positioned in the vitreous over the posterior pole during ramp increases and decreases in MAP before and after dorzolamide. Results Dorzolamide lowered IOP by 19% (P < 0.01) and aqueous flow by 17% (P < 0.01), and increased ciliary blood flow by 18% (P < 0.01), which was associated with a significant reduction in ciliary vasculature resistance (−7%, P < 0.01). Dorzolamide shifted the relationship between ciliary blood flow and aqueous flow downward relative to the previously determined control relationship in the rabbit. Dorzolamide did not alter choroidal blood flow, choroidal vascular resistance, or the choroidal pressure flow relationship. Conclusions Acute topical dorzolamide is a ciliary vasodilator and has a direct inhibitory effect on aqueous production, but it does not have a detectable effect on choroidal hemodynamics at the posterior pole in the rabbit. PMID:19182250

  8. 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.

  9. Effects of aortic irregularities on blood flow.

    PubMed

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

    2016-04-01

    Anatomic aortic anomalies are seen in many medical conditions and are known to cause disturbances in blood flow. Turner syndrome (TS) is a genetic disorder occurring only in females where cardiovascular anomalies, particularly of the aorta, are frequently encountered. In this study, numerical simulations are applied to investigate the flow characteristics in four TS patient- related aortic arches (a normal geometry, dilatation, coarctation and elongation of the transverse aorta). The Quemada viscosity model was applied to account for the non-Newtonian behavior of blood. The blood is treated as a mixture consisting of water and red blood cells (RBC) where the RBCs are modeled as a convected scalar. The results show clear geometry effects where the flow structures and RBC distribution are significantly different between the aortas. Transitional flow is observed as a jet is formed due to a constriction in the descending aorta for the coarctation case. RBC dilution is found to vary between the aortas, influencing the WSS. Moreover, the local variations in RBC volume fraction may induce large viscosity variations, stressing the importance of accounting for the non-Newtonian effects. PMID:26104133

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Computational Analysis of Human Blood Flow

    NASA Astrophysics Data System (ADS)

    Panta, Yogendra; Marie, Hazel; Harvey, Mark

    2009-11-01

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

  17. 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.

  18. Electromagnetic blood flowmeters and flow probes: theoretic and practical considerations.

    PubMed

    Scott, E A; Sandler, G A

    1978-09-01

    Electromagnetic blood flowmeters and flow probes are used to measure blood flow in blood vessels throughout the circulatory system. The principle of this measuring device is based on laws of electromagnetic induction discovered in the 19th century. The instrument has been predominantly used in research, but is presently used in human cardiovascular units to measure blood flow in blood vessels, and in prosthesis in conjection with cardiovascular surgical procedures. Electromagnetic flow equipment provides the most accurate measurement (in vivo) of blood flow available, both for acute and chronic implants. This report presents some of the theoretic and practical considerations for effective use of this instrument.

  19. Lagrangian Coherent Structures in Blood Flow

    NASA Astrophysics Data System (ADS)

    Shadden, Shawn

    2008-11-01

    Knowledge of fluid transport is particularly compelling in understanding the function of cardiovascular processes. Transport of chemicals, cells, and compounds in the vascular system is influenced by local flow structures in large vessels. Local flow features can also induce cell-signaling pathways and biologic response critical to maintaining health or disease progression. Complex vessel geometry, the pulsatile pumping of blood, and low Reynolds number turbulence leads to complex flow features in large vessels. However, we are gaining the ability to study transport in large vessels with unprecedented detail, which is in part allowing us to broaden the ``shear-centric'' view of hemodynamics. In this talk we will describe the application of computational fluid mechanics and the computation of Lagrangian coherent structures (LCS) to study transport in various cardiovascular applications. We will discuss some of the challenges of this work and some results of computing LCS in several regions of the vascular system. In collaboration with Charles Taylor, Stanford University.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. Regulation of cerebral blood flow during exercise.

    PubMed

    Querido, Jordan S; Sheel, A William

    2007-01-01

    Constant cerebral blood flow (CBF) is vital to human survival. Originally thought to receive steady blood flow, the brain has shown to experience increases in blood flow during exercise. Although increases have not consistently been documented, the overwhelming evidence supporting an increase may be a result of an increase in brain metabolism. While an increase in metabolism may be the underlying causative factor for the increase in CBF during exercise, there are many modulating variables. Arterial blood gas tensions, most specifically the partial pressure of carbon dioxide, strongly regulate CBF by affecting cerebral vessel diameter through changes in pH, while carbon dioxide reactivity increases from rest to exercise. Muscle mechanoreceptors may contribute to the initial increase in CBF at the onset of exercise, after which exercise-induced hyperventilation tends to decrease flow by pial vessel vasoconstriction. Although elite athletes may benefit from hyperoxia during intense exercise, cerebral tissue is well protected during exercise, and cerebral oxygenation does not appear to pose a limiting factor to exercise performance. The role of arterial blood pressure is important to the increase in CBF during exercise; however, during times of acute hypotension such as during diastole at high-intensity exercise or post-exercise hypotension, cerebral autoregulation may be impaired. The impairment of an increase in cardiac output during exercise with a large muscle mass similarly impairs the increase in CBF velocity, suggesting that cardiac output may play a key role in the CBF response to exercise. Glucose uptake and CBF do not appear to be related; however, there is growing evidence to suggest that lactate is used as a substrate when glucose levels are low. Traditionally thought to have no influence, neural innervation appears to be a protective mechanism to large increases in cardiac output. Changes in middle cerebral arterial velocity are independent of changes in

  5. 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

  6. 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

  7. Gut blood flow in the estuarine crocodile, Crocodylus porosus.

    PubMed

    Axelsson, M; Fritsche, R; Holmgren, S; Grove, D J; Nilsson, S

    1991-08-01

    Simultaneous recordings of blood flow in the right and left aorta and carotid and coeliac artery were made in the crocodile, Crocodylus porosus at rest and during various stimuli. In resting animals the right aorta and carotid artery flow profiles resembled the recordings obtained in the caiman (Axelsson et al. 1989a), with an anterograde blood flow throughout the cardiac cycle. As in the caiman, the left aorta flow profile was complex with both anterograde and retrograde blood flow during the cardiac cycle, and a net left aorta blood flow near zero at rest. The coeliac artery blood flow profile did not show the complex pattern seen in the upper aorta, immediately suggesting that most of the coeliac artery blood originates elsewhere. We believe that coeliac artery blood flow in the resting animal derives from the right aorta via the abdominal anastomosis between the two aortas. Feeding induced an increase in the coeliac artery and left aorta blood flow, probably due to a decrease in visceral vascular resistance, and hence coeliac arterial and the left aorta blood pressure, which facilitates blood flow (from right to left aorta) through the foramen of Panizza. During short 'fright dives', heart rate fell and there was a decrease in the recorded blood flows: carotid artery blood flow did not decrease to the same extent as the RAo and coeliac artery flow, indicating some capacity for redistribution of blood to the cephalic circuits during diving. Similarly, a near-unimpaired carotid artery blood flow was maintained after adrenaline injection. Substance P increased the coeliac artery blood flow and produced a right-to-left cardiac shunt, probably by construction of the pulmonary vasculature.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Tissue blood flow mapping using laser technology

    NASA Astrophysics Data System (ADS)

    Wardell, Karin; Linden, Maria; Nilsson, Gert E.

    1995-03-01

    By the introduction of the laser Doppler perfusion imager (LDPI) the microvascular blood flow in a tissue area can be mapped by sequentially moving a laser beam over the tissue. The measurement is performed without touching the tissue and the captured perfusion values in the peripheral circulation are presented as a color-coded image. In the ordinary LDPI-set-up, 64 X 64 measurement sites cover an area in the range of about 10 - 150 cm2 depending on system settings. With a high resolution modification, recordings can be done on tissue areas as small as 1 cm2. This high resolution option has been assessed in animal models for the mapping of small vessels. To be able to record not only spatial but also temporal perfusion components of tissue blood flow, different local area scans (LAS) have been developed. These include single point recording as well as integration of either 2 X 2, 3 X 3, or 4 X 4 measurement sites. The laser beam is repeatedly moved in a quadratic pattern over the small tissue area of interest and the output value constitutes the average perfusion of all captured values within the actual region. For the evaluation, recordings were performed on healthy volunteers before and after application of a vasodilatating cream on the dorsal side of the hand.

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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

  5. Redistribution of blood flow in acute hypometabolic behavior.

    PubMed

    Jevning, R; Wilson, A F; Smith, W R; Morton, M E

    1978-07-01

    Cardiac output, renal and hepatic blood flows, arterial lactate concentration, and minute volume were measured before, during, and after 40 min of rest induced either by the practice known as "transcendental meditation" (TM) or by an ordinary eyes-closed rest-relaxation period. Two groups of normal young adults were studied: one group consisted of regular practitioners of TM and the other of similar individuals studied prior to learning this technique. Marked declines of renal blood flow were noted in both groups. Decline of hepatic blood flow, increased cardiac output, decreased arterial lactate, and minute volume were also recorded in the TM-induced rest period. These changes imply a considerable increase of nonrenal, nonhepatic blood flow during TM (44%) and, to a lesser extent, during rest (12%). Increased cerebral and/or skin blood flow is hypothesized to account for part of the redistributed blood flow in the practitioner.

  6. 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.

  7. Multiscale modeling of blood flow: from single cells to blood rheology.

    PubMed

    Fedosov, Dmitry A; Noguchi, Hiroshi; Gompper, Gerhard

    2014-04-01

    Mesoscale simulations of blood flow, where the red blood cells are described as deformable closed shells with a membrane characterized by bending rigidity and stretching elasticity, have made much progress in recent years to predict the flow behavior of blood cells and other components in various flows. To numerically investigate blood flow and blood-related processes in complex geometries, a highly efficient simulation technique for the plasma and solutes is essential. In this review, we focus on the behavior of single and several cells in shear and microcapillary flows, the shear-thinning behavior of blood and its relation to the blood cell structure and interactions, margination of white blood cells and platelets, and modeling hematologic diseases and disorders. Comparisons of the simulation predictions with existing experimental results are made whenever possible, and generally very satisfactory agreement is obtained.

  8. Effect of glomerulopressin on ovarian blood flow in dogs.

    PubMed

    Uranga, J; Del Castillo, E

    1979-10-01

    The present study showed that glomerulopressin decreased ovarian blood flow in normal dogs and that this effect could be inhibited by treatment with indomethacin. In addition diabetic dogs had a high plasma level of glomerulopressin and a low ovarian blood flow that was shown to increase after treatment with indomethacin. This suggests that the low ovarian blood flow in diabetis might be due to a prostaglandin synthesizing effect of glomerulopressin.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Correlation of skin temperature and blood flow oscillations

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Usanov, D. A.; Skripal, A. V.; Fomin, A. V.

    2011-10-01

    Interrelation of skin temperature and blood flow oscillations of fingers under normal conditions in healthy subjects has been investigated. Oscillations of a blood flow were measured by means of photoplethysmography; oscillations of a temperature were registered by means of thermal imaging camera. The method of blood flow reconstruction by temperature oscillations with the use of the Pennes bioheat transfer equation and a definition of delay time of a temperature in relation to blood flow signal has been described. Temperature oscillations have a lag in relation to blood flow oscillations of approximately 10-20 seconds. Delay time of temperature waves can be used for the definition of an effective thickness of a tissue layer separating blood vessels and skin surface. Use of the described technique of comparison of finger blood flow and temperature oscillations allows to raise correlation coefficient of the signals from 0.35 to 0.63 on average, which testifies of high degree of conditionality of temperature oscillations by blood flow oscillations. The considered method of non-contact restoration of blood flow oscillations by means of temperature oscillation measurements might find practical application in skin thermal lesions research, research of influence of physical and chemical factors on a skin microcirculation.

  14. Correlation of skin temperature and blood flow oscillations

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Usanov, D. A.; Skripal, A. V.; Fomin, A. V.

    2012-03-01

    Interrelation of skin temperature and blood flow oscillations of fingers under normal conditions in healthy subjects has been investigated. Oscillations of a blood flow were measured by means of photoplethysmography; oscillations of a temperature were registered by means of thermal imaging camera. The method of blood flow reconstruction by temperature oscillations with the use of the Pennes bioheat transfer equation and a definition of delay time of a temperature in relation to blood flow signal has been described. Temperature oscillations have a lag in relation to blood flow oscillations of approximately 10-20 seconds. Delay time of temperature waves can be used for the definition of an effective thickness of a tissue layer separating blood vessels and skin surface. Use of the described technique of comparison of finger blood flow and temperature oscillations allows to raise correlation coefficient of the signals from 0.35 to 0.63 on average, which testifies of high degree of conditionality of temperature oscillations by blood flow oscillations. The considered method of non-contact restoration of blood flow oscillations by means of temperature oscillation measurements might find practical application in skin thermal lesions research, research of influence of physical and chemical factors on a skin microcirculation.

  15. 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.

  16. Measurement of human cochlear blood flow.

    PubMed

    Miller, J M; Bredberg, G; Grenman, R; Suonpää, J; Lindström, B; Didier, A

    1991-01-01

    Cochlear blood flow (CBF) was measured with a laser-Doppler (L-D) flowmeter (Periflux PR2-B) in four unanesthetized human subjects with chronic tympanic membrane perforations and nine anesthetized human subjects undergoing middle ear operations. The L-D recordings were made over the promontory and/or the round window membrane during carbogen breathing and direct electrical stimulation of the cochlea in both groups and with warm water irrigation of the external ear canal in the anesthetized subjects. Carbogen led to little or no change in CBF as monitored with either measurement approach in either subject group. Electrical stimulation yielded an increase (15% to 25%) in CBF as recorded from the promontory in seven of the nine subjects tested. Warm (44 degrees C to 49 degrees C) water irrigation produced changes of 20% to 60% in CBF that were partially recoverable in the 10 minutes available for study. This study demonstrated the feasibility of direct CBF measurement in humans with the L-D method. Moreover, the data indicate that carbogen has little influence on CBF and that electrical stimulation at relatively safe levels and warm water irrigation of the ear canal produce increases in human CBF.

  17. 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

  18. 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.

  19. 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

  20. 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.

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

    PubMed Central

    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

  2. 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

  3. Blood flow boosts BMP signaling to keep vessels in shape.

    PubMed

    Franco, Claudio A; Gerhardt, Holger

    2016-09-26

    Bone morphogenic proteins (BMPs) and blood flow regulate vascular remodeling and homeostasis. In this issue, Baeyens et al. (2016. J. Cell Biol http://dx.doi.org/10.1083/jcb.201603106) show that blood flow sensitizes endothelial cells to BMP9 signaling by triggering Alk1/ENG complexing to suppress cell proliferation and to recruit mural cells, thereby establishing endothelial quiescence. PMID:27672213

  4. 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.

  5. 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.

  6. 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.

  7. Effect of tumor blood flow manipulations on radiation response

    SciTech Connect

    Pallavicini, M.G.; Hill, R.P.

    1983-09-01

    The effect of anesthestics and several vasoactive agents on the blood flow, temperature, and radiation response of the solid murine KHT sarcoma was evaluated to better understand the relationship of tumor blood flow and the proportion of hypoxic cells. Tumor blood flow, assessed by 133-Xeonon clearance, decreased by 59 and 24% following treatment with pentobarbital and urethane, respectively. In addition, both drugs reduced body and tumor temperature. Metaraminol, a sympathomimetic agent, and nitroglycerin also reduced tumor blood flow by 40 and 12%, respectively. Tumor radiation response following drug treatment was quantitated by an in vitro agar assay. Results indicate that drug-induced reductions in tumor blood flow generally result in an increase in the apparent tumor cell hypoxic fraction.

  8. 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.

  9. 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.

  10. 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.

  11. Palmar skin blood flow and temperature responses throughout endoscopic sympathectomy.

    PubMed

    Crandall, Craig G; Meyer, Dan M; Davis, Scott L; Dellaria, Suzanne M

    2005-01-01

    Thoracic surgical sympathectomy is often performed to treat primary palmar and axillary hyperhidrosis. An increase in palmar skin temperature is frequently used to identify the success of the procedure. Because changes in palmar skin temperature occur secondary to changes in skin blood flow, the objective of this study was to test the hypothesis that monitoring palmar skin blood flow would provide greater temporal resolution relative to monitoring palmar skin temperature. In 11 patients with palmar and/or axillary hyperhidrosis, we measured palmar skin temperature and blood flow (via laser Doppler flowmetry) throughout the sympathectomy procedure. Five minutes after the initial cautery, skin blood flow increased from 48 +/- 7 perfusion units to 121 +/- 17 perfusion units (P <0.001), whereas no significant change in temperature was observed (31.0 degrees C +/- 0.5 degrees C to 31.3 degrees C +/- 0.5 degrees C; P >0.05). The time required to reach peak skin blood flow (22 +/- 3 min) was significantly less than the time required to reach peak skin temperature (34 +/- 0.3 min; P <0.001). Finally at 5, 10, and 15 min after the initial cautery, skin blood flow increased to a larger percentage of the total increase in skin blood flow relative skin temperature (all P <0.006). These data suggest that monitoring skin blood flow provides greater temporal resolution when compared with monitoring skin temperature during thoracic sympathectomy. However, the initial cautery of the parietal pleura over the ganglion may result in increases in skin blood flow before physical disruption of the ganglion. This occurrence may limit the utility of skin blood-flow measurements in identifying the success of the procedure. PMID:15616091

  12. 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.

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

    PubMed

    Javadzadegan, Ashkan; Simmons, Anne; Barber, Tracie

    2016-01-01

    The presence of a spiral arterial blood flow pattern in humans has been widely accepted. It is believed that this spiral component of the blood flow alters arterial haemodynamics in both positive and negative ways. The purpose of this study was to determine the effect of spiral flow on haemodynamic changes in aorta-renal bifurcations. In this regard, a computational fluid dynamics analysis of pulsatile blood flow was performed in two idealised models of aorta-renal bifurcations with and without flow diverter. The results show that the spirality effect causes a substantial variation in blood velocity distribution, while causing only slight changes in fluid shear stress patterns. The dominant observed effect of spiral flow is on turbulent kinetic energy and flow recirculation zones. As spiral flow intensity increases, the rate of turbulent kinetic energy production decreases, reducing the region of potential damage to red blood cells and endothelial cells. Furthermore, the recirculation zones which form on the cranial sides of the aorta and renal artery shrink in size in the presence of spirality effect; this may lower the rate of atherosclerosis development and progression in the aorta-renal bifurcation. These results indicate that the spiral nature of blood flow has atheroprotective effects in renal arteries and should be taken into consideration in analyses of the aorta and renal arteries. PMID:26414530

  14. 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.

  15. Cardiac cryosurgery: regional myocardial blood flow of ventricular cryolesions

    SciTech Connect

    Holman, W.L.; Ikeshita, M.; Lease, J.G.; Smith, P.K.; Ungerleider, R.M.; Cox, J.L.

    1986-11-01

    Cryosurgery is one of three methods introduced recently for the treatment of ventricular tachyarrhythmias. Cryothermic exposure ablates arrhythmogenic ventricular myocardium, and produces a dense fibrous scar with a sharp border to histologically normal tissue. Myocardial blood flow in the region of the cryolesion, however, has not been quantitated. The purpose of this study was to measure regional blood flow within and around the cryolesion in an attempt to identify ischemic zones that might become arrhythmogenic. Left ventricular cryolesions were created in eleven adult dogs. Two weeks later, the animals underwent radioactive tracer microsphere injection for quantitation of regional myocardial blood flow. The fibrotic cryolesion demonstrated a significantly depressed blood flow (0.44 +/- 0.07 ml/min/g) compared to blood flow in control tissue (1.36 +/- 0.12 ml/min/g) (P less than 0.001). A 1-mm strip of myocardium immediately adjacent to the cryolesion, as well as other myocardium surrounding and subjacent to the cryolesion, did not show a significant decrease in regional blood flow. The border between the fibrotic cryolesion and the surrounding myocardium is, therefore, sharply defined not only in terms of histology but also in regards to regional blood flow. These data lend further support to the safe clinical use of cryothermia in the treatment of refractory ventricular tachycardia.

  16. Assessing cerebral blood flow control from variability in blood pressure and arterial CO2 levels.

    PubMed

    Nikolić, Dragana; Birch, Anthony A; Panerai, Ronney B; Simpson, David M

    2015-08-01

    Blood flow to the brain is controlled by a number of physiological mechanisms that respond to changes in arterial blood pressure, arterial CO2 levels and many other factors. Assessing the integrity of this control system is a major challenge. We report on repeatability of measures based on single and multiple input models during spontaneous and enhanced fluctuations in blood pressure.

  17. 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.

  18. [Helical (spiral or swirling) blood flow in cardiovascular system].

    PubMed

    Kirsanov, R I; Kulikov, V P

    2013-01-01

    In article covers theoretical preconditions for the hypothesis about helical (spiral or swirling) blood flow in cardiovascular system followed by its experimental corroboration. The role of the modern blood flow visualization methods--such as Color Doppler ultrasound and magnetic-resonance angiography--in registration and investigation of the regularities of the given phenomenon is described. The data describing the known parameters of helical blood flow--such as direction of the rotation and its quantitative parameters in large arteries--are given. The main hypotheses for flow screw mechanisms are considered from the point of view of cardiovascular system structural organization. Biological role of helical blood flow is discussed, in respect of which there are diametrically opposed points of view, which consider it as a physiological phenomenon on one side, and as a patogenetic factor of atherosclerosis development on the other.

  19. Effect of plasma exchange on blood viscosity and cerebral blood flow.

    PubMed Central

    Brown, M M; Marshall, J

    1982-01-01

    The effects of plasma exchange using a low viscosity plasma substitute on blood viscosity and cerebral blood flow were investigated in eight subjects with normal cerebral vasculature. Plasma exchange resulted in significant reductions in plasma viscosity, whole blood viscosity, globulin and fibrinogen concentration without affecting packed cell volume. The reduction in whole blood viscosity was more pronounced at low shear rates suggesting an additional effect on red cell aggregation. Despite the fall in viscosity there was no significant change in cerebral blood flow. The results support the metabolic theory of autoregulation. Although changes in blood viscosity appear not to alter the level of cerebral blood flow under these circumstances, plasma exchange could still be of benefit in the management of acute cerebrovascular disease. PMID:6805689

  20. 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

  1. 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.

  2. Intrarenal blood flow distribution during adenosine-mediated vasoconstriction.

    PubMed

    Macias, J F; Fiksen-Olsen, M; Romero, J C; Knox, F G

    1983-01-01

    Intrarenal infusion of adenosine induces an initial vasoconstriction followed by a subsequent vasodilation. The intrarenal distribution of blood flow in the vasoconstriction phase is unknown. The present study was undertaken to assess the effect of intrarenal infusion of adenosine on intracortical distribution of renal blood flow during both the vasoconstriction and vasodilation phases. Renal blood flow distribution was measured with radiolabeled microspheres in anesthetized sodium-depleted dogs before and during the early vasoconstriction phase and the late vasodilation phase of intrarenal infusion of adenosine. During the vasoconstriction phase, there was a uniform decrease in blood flow in each renal cortical zone. In the late phase of adenosine infusion, there was a significant increase in deep cortical flow without significant changes in superficial cortical flow compared with control. The effects of adenosine were also compared with those exerted by norepinephrine in which decreased blood flow was demonstrated in all zones. We conclude that the vasoconstrictor phase of adenosine infusion is characterized by a uniform reduction of renal blood flow to all cortical zones, whereas the vasodilator phase is characterized by a selective deep cortical vasodilation.

  3. 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.

  4. 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.

  5. Rheology of Human Blood, near and at Zero Flow

    PubMed Central

    Merrill, E. W.; Gilliland, E. R.; Cokelet, G.; Shin, H.; Britten, A.; Wells, R. E.

    1963-01-01

    Static normal human blood possesses a distinctive yield stress. When the yield stress is exceeded, the same blood has a stress-shear rate function under creeping flow conditions closely following Casson's model, which implies reversible aggregation of red cells in rouleaux and flow dominated by movement of rouleaux. The yield stress is essentially independent of temperature and its cube root varies linearly with hematocrit value. The dynamic rheological properties in the creeping flow range are such that the relative viscosity of blood to water is almost independent of temperature. Questions raised by these data are discussed, including red cell aggregation promoted by elements in the plasma. PMID:13935042

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

    PubMed

    Ortega, J M

    2013-08-01

    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

  7. 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

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

    PubMed

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

    2016-09-01

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

  9. 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

  10. 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

  11. Influence of Hypoxia on Cerebral Blood Flow Regulation in Humans.

    PubMed

    Steinback, Craig D; Poulin, Marc J

    2016-01-01

    The brain is a vital organ that relies on a constant and adequate supply of blood to match oxygen and glucose delivery with the local metabolic demands of active neurones. It is well established that cerebral blood flow is altered in response to both neural activity and humoral stimuli. Thus, augmented neural activation (e.g. visual stimulation) leads to locally increased cerebral blood flow via functional hyperaemia, whereas humoral stimuli (i.e. alterations in arterial PO2 and PCO2) produce global increases in cerebral blood flow. Perhaps not surprisingly, cerebrovascular responses to neural activity and humoral stimuli may not be highly correlated because they reflect different physiological mechanisms for vasodilation. Exquisite regulation of cerebral blood flow is particularly important under hypoxic conditions when cerebral PO2 can be reduced substantially. Indeed, cerebrovascular reactivity to hypoxia determines the capacity of cerebral vessels to respond and compensate for a reduced oxygen supply. This reactivity is dynamic, changing with prolonged exposure to hypoxic environments, and in patients and healthy individuals exposed to chronic intermittent periods of hypoxia. More recently, a number of animal studies have provided evidence that glial cells (i.e. astrocytes) play an important role in regulating cerebral blood flow under normoxic and hypoxic conditions. This review aims to summarize our current understanding of cerebral blood flow control during hypoxia in humans and put into context the underlying neurovascular mechanisms that may contribute to this regulation. PMID:27343093

  12. 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

  13. 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.

  14. Blood flow changes in permanent maxillary canines during retraction.

    PubMed

    McDonald, F; Pitt Ford, T R

    1994-02-01

    The influence of external load on the blood flow of permanent maxillary canine teeth was assessed by laser Doppler flowmetry (LDF). Blood flow readings were obtained from 10 maxillary canines and compared with the contralateral teeth simultaneously. Readings were obtained from the teeth before, during, and after the application of a 50 g force (gf) which was applied using a removable appliance. The probe for LDF measurement was held in place by a splint constructed of a silicone impression material designed to allow movement of the tooth, but prevent instability of the probe. LDF demonstrated a reading from the canine teeth consistent with recordings of blood flow, i.e. the traces were similar to the pulsatile nature of pulse pressure recordings taken from the subjects' ear-lobes. After loading the effect on the canine was (1) a decrease in blood flow as measured with LDF followed by (2) an increase in flow after 32.3 minutes (SD 4.74). These changes were statistically significant (P < 0.05) using Student's t-test. The increase in blood flow was still present after 24 and 48 hours, but returned to preload values within 72 hours. In two cases it was found that the decrease in blood flow remained as long as the load was applied. The response appeared similar to reactive hyperaemia found following placement of a tourniquet. However, the response time was substantially longer for the hyperaemic phase.

  15. 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.

  16. Effects of cilostazol lotion on blood flow in rabbit skin.

    PubMed

    Ono, I; Gunji, H; Suda, K; Kaneko, F

    1994-04-01

    Cilostazol (Cls) is a inhibitor of phosphodiesterase and increases cyclic AMP (cAMP) in platelets and also raises the vascular smooth muscle cell cAMP level causing vasodilation. Therefore, it was expected to increase local blood flow in the skin. Topical application of Cls may improve local blood flow without systemic effects in clinical situations. In this paper the effect of Cls lotion on skin blood flow was assessed in animal experiments. Application of this lotion allowed skin blood flow to remain at increased levels for about 60-90 min. Tissue assay of the Cls content revealed that Cls is absorbed percutaneously and retained, even in the inner tissue layer, for at least 180 min.

  17. 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.

  18. 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

  19. Blood flow changes coincide with cellular rearrangements during blood vessel pruning in zebrafish embryos.

    PubMed

    Kochhan, Eva; Lenard, Anna; Ellertsdottir, Elin; Herwig, Lukas; Affolter, Markus; Belting, Heinz-Georg; Siekmann, Arndt F

    2013-01-01

    After the initial formation of a highly branched vascular plexus, blood vessel pruning generates a hierarchically structured network with improved flow characteristics. We report here on the cellular events that occur during the pruning of a defined blood vessel in the eye of developing zebrafish embryos. Time-lapse imaging reveals that the connection of a new blood vessel sprout with a previously perfused multicellular endothelial tube leads to the formation of a branched, Y-shaped structure. Subsequently, endothelial cells in parts of the previously perfused branch rearrange from a multicellular into a unicellular tube, followed by blood vessel detachment. This process is accompanied by endothelial cell death. Finally, we show that differences in blood flow between neighboring vessels are important for the completion of the pruning process. Our data suggest that flow induced changes in tubular architecture ensure proper blood vessel pruning. PMID:24146748

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1988-04-01

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

  8. 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.

  9. Functional Doppler optical coherence tomography for cortical blood flow imaging

    NASA Astrophysics Data System (ADS)

    Yu, Lingfeng; Liu, Gangjun; Nguyen, Elaine; Choi, Bernard; Chen, Zhongping

    2010-02-01

    Optical methods have been widely used in basic neuroscience research to study the cerebral blood flow dynamics in order to overcome the low spatial resolution associated with magnetic resonance imaging and positron emission tomography. Although laser Doppler imaging and laser speckle imaging can map out en face cortical hemodynamics and columns, depth resolution is not available. Two-photon microscopy has been used for mapping cortical activity. However, flow measurement requires fluorescent dye injection, which can be problematic. The noninvasive and high resolution tomographic capabilities of optical coherence tomography make it a promising technique for mapping depth resolved cortical blood flow. Here, we present a functional Doppler optical coherence tomography (OCT) imaging modality for quantitative evaluation of cortical blood flow in a mouse model. Fast, repeated, Doppler OCT scans across a vessel of interest were performed to record flow dynamic information with a high temporal resolution of the cardiac cycles. Spectral Doppler analysis of continuous Doppler images demonstrates how the velocity components and longitudinally projected flow-volume-rate change over time, thereby providing complementary temporal flow information to the spatially distributed flow information of Doppler OCT. The proposed functional Doppler OCT imaging modality can be used to diagnose vessel stenosis/blockage or monitor blood flow changes due to pharmacological agents/neuronal activities. Non-invasive in-vivo mice experiments were performed to verify the capabilities of function Doppler OCT.

  10. 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.

  11. Ultrafast Ultrasound Imaging of Ocular Anatomy and Blood Flow

    PubMed Central

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

    2016-01-01

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

  12. Angiotensin II alters blood flow distribution in amphibians.

    PubMed

    Slivkoff, M D; Warburton, S J

    2001-01-01

    In toads, angiotensin II (ANG II) induces the water absorption response (WR) during which the seat patch (pelvic+inner-thigh skin) is pressed to a wet substrate from which water flows osmotically into the animal. Since ANG II is a potent vasoconstrictor, it has the potential to redistribute blood flow. To determine the regional circulatory effects of ANG II, we used microsphere methods to measure relative changes in blood flow to several skin regions and other organs before and after ANG II administration in terrestrial toads and aquatic bullfrogs. In toads, after ANG II administration, seat patch and bladder blood flow increased by 264.2%+/-197.6% and 287.2%+/-86.7%, respectively (P<0.05), while dorsal and pectoral skin flow decreased by 48.0%+/-19.4% and 21.3%+/-25.4%, respectively (P<0.05). In bullfrogs, ANG II caused no significant changes in blood flow. Our results support our hypothesis that, in toads, ANG II increases and decreases blood flow to regions of the body associated with water gain and water loss, respectively.

  13. Development of a wireless sensor for the measurement of chicken blood flow using the laser Doppler blood flow meter technique.

    PubMed

    Nishihara, Kei; Iwasaki, Wataru; Nakamura, Masaki; Higurashi, Eiji; Soh, Tomoki; Itoh, Toshihiro; Okada, Hironao; Maeda, Ryutaro; Sawada, Renshi

    2013-06-01

    Here, we report the development of an integrated laser Doppler blood flow micrometer for chickens. This sensor weighs only 18 g and is one of the smallest-sized blood flow meters, with no wired line, these are features necessary for attaching the sensor to the chicken. The structure of the sensor chip consists of two silicon cavities with a photo diode and a laser diode, which was achieved using the microelectromechanical systems technique, resulting in its small size and significantly low power consumption. In addition, we introduced an intermittent measuring arrangement in the measuring system to reduce power consumption and to enable the sensor to work longer. We were successfully able to measure chicken blood flow for five consecutive days, and discovered that chicken blood flow shows daily fluctuations.

  14. 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

  15. Ultrasonic Imaging of Hemodynamic Force in Carotid Blood Flow

    NASA Astrophysics Data System (ADS)

    Nitta, N.; Homma, K.

    Hemodynamic forces including blood pressure and shear stress affect vulnerable plaque rupture in arteriosclerosis and biochemical activation of endothelium such as NO production. In this study, a method for estimating and imaging shear stress and pressure gradient distributions in blood vessel as the hemodynamic force based on viscosity estimation is presented. Feasibility of this method was investigated by applying to human carotid blood flow. Estimated results of shear stress and pressure gradient distributions coincide with the ideal distributions obtained by numerical simulation and flow-phantom experiment.

  16. Three-phase CFD analytical modeling of blood flow.

    SciTech Connect

    Jung, J.; Hassanein, A.; Mathematics and Computer Science

    2008-01-01

    The behavior of blood cells in disturbed flow regions of arteries has significant relevance for understanding atherogenesis. However, their distribution with red blood cells (RBCs) and leukocytes is not so well studied and understood. Our three-phase computational fluid dynamics approach including plasma, RBCs, and leukocytes was used to numerically simulate the local hemodynamics in such a flow regime. This model has tracked the wall shear stress (WSS), phase distributions, and flow patterns for each phase in a concentrated suspension shear flow of blood. Unlike other computational approaches, this approach does not require dispersion coefficients as an input. The non-Newtonian viscosity model was applied to a wide physiological range of hematocrits, including low shear rates. The migration and segregation of blood cells in disturbed flow regions were computed, and the results compared favorably with available experimental data. The predicted higher leukocyte concentration was correlated with relatively low WSS near the stenosis having a high WSS. This behavior was attributed to flow-dependent interactions of the leukocytes with RBCs in pulsatile flow. This three-phase hemodynamic analysis may have application to vulnerable plaque formation in arteries with in vivo complex flow conditions.

  17. 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…

  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. 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.

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

    PubMed

    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. 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.

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

    PubMed

    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. PMID:2645693

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

    PubMed

    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.

  4. Margination of White Blood Cells in Microcapillary Flow

    NASA Astrophysics Data System (ADS)

    Fedosov, Dmitry A.; Fornleitner, Julia; Gompper, Gerhard

    2012-01-01

    Margination of white blood cells (WBCs) towards vessel walls is an essential precondition for their efficient adhesion to the vascular endothelium. We perform numerical simulations with a two-dimensional blood flow model to investigate the dependence of WBC margination on hydrodynamic interactions of blood cells with the vessel walls, as well as on their collective behavior and deformability. We find WBC margination to be optimal in intermediate ranges of red blood cell (RBC) volume fractions and flow rates, while, beyond these ranges, it is substantially attenuated. RBC aggregation enhances WBC margination, while WBC deformability reduces it. These results are combined in state diagrams, which identify WBC margination for a wide range of flow and cell suspension conditions.

  5. The effect of flow acceleration on the cyclic variation of blood echogenicity under pulsatile flow.

    PubMed

    Huang, Chih-Chung; Liao, Chen-Chih; Lee, Po-Yang; Shih, Cho-Chiang

    2013-04-01

    It has been shown that the echogenicity of blood varies during a flow cycle under pulsatile flow both in vitro and in vivo. In general, the echogenicity of flowing whole blood increases during the early systole phase and then reduces to a minimum at late diastole. While it has been postulated that this cyclic variation is associated with the dynamics of erythrocyte aggregation, the mechanisms underlying this increasing echogenicity with flow velocity remain uncertain. The effect of flow acceleration has also been proposed as an explanation for this phenomenon, but no specific experiments have been conducted to test this hypothesis. In addition, the influence of ultrasonic attenuation on the cyclic variation of echogenicity requires clarification. In the present study, a Couette flow system was designed to simulate blood flowing with different acceleration patterns, and the flow velocity, attenuation, and backscattering coefficient were measured synchronously from 20%- and 40%-hematocrit porcine whole blood and erythrocyte suspensions using 35-MHz ultrasound transducers. The results showed ultrasonic attenuation exerted only minor effects on the echogenicity of blood under pulsatile flow conditions. Cyclic variations of echogenicity were clearly observed for whole blood with a hematocrit of 40%, but no variations were apparent for erythrocyte suspensions. The echogenicity did not appear to be enhanced when instantaneous acceleration was applied to flowing blood in any case. These findings show that flow acceleration does not promote erythrocyte aggregation, even when a higher peak velocity is applied to the blood. Comparison of the results obtained with different accelerations revealed that the cyclic variation in echogenicity observed during pulsatile blood flow may be jointly attributable to the effect of shear rate and the distribution of erythrocyte on aggregation.

  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. Pulsatile blood flow, shear force, energy dissipation and Murray's Law

    PubMed Central

    Painter, Page R; Edén, Patrik; Bengtsson, Hans-Uno

    2006-01-01

    Background Murray's Law states that, when a parent blood vessel branches into daughter vessels, the cube of the radius of the parent vessel is equal to the sum of the cubes of the radii of daughter blood vessels. Murray derived this law by defining a cost function that is the sum of the energy cost of the blood in a vessel and the energy cost of pumping blood through the vessel. The cost is minimized when vessel radii are consistent with Murray's Law. This law has also been derived from the hypothesis that the shear force of moving blood on the inner walls of vessels is constant throughout the vascular system. However, this derivation, like Murray's earlier derivation, is based on the assumption of constant blood flow. Methods To determine the implications of the constant shear force hypothesis and to extend Murray's energy cost minimization to the pulsatile arterial system, a model of pulsatile flow in an elastic tube is analyzed. A new and exact solution for flow velocity, blood flow rate and shear force is derived. Results For medium and small arteries with pulsatile flow, Murray's energy minimization leads to Murray's Law. Furthermore, the hypothesis that the maximum shear force during the cycle of pulsatile flow is constant throughout the arterial system implies that Murray's Law is approximately true. The approximation is good for all but the largest vessels (aorta and its major branches) of the arterial system. Conclusion A cellular mechanism that senses shear force at the inner wall of a blood vessel and triggers remodeling that increases the circumference of the wall when a shear force threshold is exceeded would result in the observed scaling of vessel radii described by Murray's Law. PMID:16923189

  8. Blood flow in capillaries of the human lung.

    PubMed

    Haber, Shimon; Clark, Alys; Tawhai, Merryn

    2013-10-01

    A novel model for the blood system is postulated focusing on the flow rate and pressure distribution inside the arterioles and venules of the pulmonary acinus. Based upon physiological data it is devoid of any ad hoc constants. The model comprises nine generations of arterioles, venules, and capillaries in the acinus, the gas exchange unit of the lung. Blood is assumed incompressible and Newtonian and the blood vessels are assumed inextensible. Unlike previous models of the blood system, the venules and arterioles open up to the capillary network in numerous locations along each generation. The large number of interconnected capillaries is perceived as a porous medium in which the flow is macroscopically unidirectional from arterioles to venules openings. In addition, the large number of capillaries extending from each arteriole and venule allows introduction of a continuum theory and formulation of a novel system of ordinary, nonlinear differential equations which governs the blood flow and pressure fields along the arterioles, venules, and capillaries. The solution of the differential equations is semianalytical and requires the inversion of three diagonal, 9 × 9 matrices only. The results for the total flow rate of blood through the acinus are within the ballpark of physiological observations despite the simplifying assumptions used in our model. The results also manifest that the contribution of the nonlinear convection term of the Navier-Stokes equations has little effect (less than 2%) on the total blood flow entering/leaving the acinus despite the fact that the Reynolds number is not much smaller than unity at the proximal generations. The model makes it possible to examine some pathological cases. Here, centri-acinar and distal emphysema were investigated yielding a reduction in inlet blood flow rate.

  9. Skeletal blood flow: implications for bone-scan interpretation

    SciTech Connect

    Charkes, N.D.

    1980-01-01

    The dispersion of the skeleton throughout the body and its complex vascular anatomy require indirect methods for the measurement of skeletal blood flow. The results of one such method, compartmental analysis of skeletal tracer kinetics, are presented. The assumptions underlying the models were tested in animals and found to be in agreement with experimental observations. Based upon the models and the experimental results, inferences concerning bone-scan interpretation can be drawn: decreased cardiac output produces low-contrast (technically poor) scans; decreased skeletal flow produces photon-deficient lesions; increase of cardiac output or of generalized systemic blood flow is undetectable 1 to 2 h after dose; increased local skeletal blood flow results from disturbance of the bone microvasculature and can occur from neurologic (sympatholytic) disorders or in association with focal abnormalities that also incite the formation of reactive bone (e.g., metastasis, fracture, etc.). Mathematical solutions of tracer kinetic data thus become relevant to bone-scan interpretation.

  10. Effective pulmonary blood flow in normal children at rest.

    PubMed Central

    Bowyer, J J; Warner, J O; Denison, D M

    1988-01-01

    Effective pulmonary blood flow was measured with a soluble inert gas uptake method (10% argon, 3.5% freon-22, 35% oxygen, balance nitrogen) in 98 apparently healthy children aged 5-14 years. None had any evidence of cardiorespiratory disease and all had normal values for absolute and dynamic lung volumes and transfer factor for carbon monoxide. Values of blood flow measured by a rebreathing method correlated reasonably closely with height, weight, body surface area, and lung volumes, and to a lesser extent with hand and foot size. The mean (SD) effective pulmonary blood flow index was 2.7 (0.31) 1 min-1 m-2. Small children found a single breath method of measuring flow more difficult to perform and the results were more variable. PMID:3238641

  11. 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.

  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. 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

  14. 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

  15. 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.

  16. Study on blood flow pulsation using laser speckle contrast imaging

    NASA Astrophysics Data System (ADS)

    Yuan, Shuai; Chen, Yu; Preza, Chrysanthe; Tang, Cha-Min

    2011-03-01

    Laser speckle contrast imaging (LSCI) is becoming an established method for full-field imaging of blood flow dynamics in animal models. Blood flow pulsation originated from heart beat affects blood flow measurement results of LSCI and it is considered as major physiology noise source for most biomedical applications. But in some biomedical applications, the details of the pulsation process might provide useful information for disease diagnostics. In this study, we investigated the ability as well as the limitation of LSCI in monitoring flow pulsation in phantom study. Both intralipid (2% - 5%) and human whole blood samples are used in phantom study. A syringe pump is controlled by a computer-programmable motor controller and liquid phantom is pushed through a 400 μm ID capillary tube by the pump at different pulsation patterns, varied in frequency (1-7 Hz), valley-to-peak ratio (10%-50%), acceleration/deceleration rate, etc. Speckle contrast images are acquired at 15-30 frames-per-seconds. Our results show: (1) it is very hard for LSCI to pick up signals from high frequency pulsation (5-7 Hz), which is close to the heart back frequency of rats. This might be caused by the nature of fluid dynamics of blood during pulsation. LSCI might not work well for animal models in detecting pulsation. (2) With low frequency pulsation (1 Hz, close to human normal pulsation rate), our experimental results shows from most pulsation patterns, LSCI could catch the fine details of the blood flow change in a cycle. LSCI might be used for studying human blood flow pulsation.

  17. [The landmarks of the measurement of cerebral blood flow].

    PubMed

    István, Nyáry

    2008-01-30

    History of the measurement of local cerebral blood flow may cover a period of one and a half centuries. Parallel forthcoming of both theoretical and technical development were the key elements of ensuing progress resulting in the present state, when by the aid of in vivo blood flow and metabolic maps, we can visualize locales of brain functioning and their interconnections. Two theoretical landmarks should be mentioned in this historic process. First, the work of Adolf Fick, as the starter of quantitative measurements in this field, and Seymour Kety's model of a single, homogenously perfused tissue element. The solution of this model, in the form of Kety's equation is still fundamental to present day blood flow mapping techniques. Among the numerous investigators over the past years, two Hungarian scientist can be named as major contributors. Kálmán Sántha made substantial studies with continuous registration of local cerebral blood flow by the aid of thermocouples, while Emil P6sztor invented the hydrogen clearance method for the measurement of local cerebral blood flow both in human and in animal studies.

  18. An analysis of the sluicing gate in pulmonary blood flow.

    PubMed

    Fung, Y C; Zhuang, F Y

    1986-05-01

    For pulmonary blood flow in zone 2 condition, in which the blood pressure in the venule (pven) is lower than the alveolar gas pressure (pA), the blood exiting from the capillary sheet and entering a venule must go through a sluicing gate. The sluicing gate exists because the venule remains patent while the capillaries will collapse when the static pressure of blood falls below the alveolar gas pressure. In the original theory of sheet flow the effect of the tension in the interalveolar septa on the flow through the sluicing gate was ignored. Since the tension multiplied by the curvature of the membrane is equivalent to a lateral pressure tending to open the gate, and since the curvature of the capillary wall is high in the gate region, this effect may be important. The present analysis improves the original theory and demonstrates that the effect of membrane tension is to cause flow to increase when the venous pressure continues to decrease. The shape of the sluicing gate resembles that of a venturi tube, and can be determined by an iterative integration of the differential equations. The result forms an important link in the theory of pulmonary blood flow in zone 2 condition.

  19. Effects on regional cerebral blood flow of transcendental meditation.

    PubMed

    Jevning, R; Anand, R; Biedebach, M; Fernando, G

    1996-03-01

    Previous blood flow measurements in this laboratory have indicated increased nonrenal nonhepatic blood flow during behaviorally induced rest states, especially during the stylized mental technique of transcendental meditation (TM). We have hypothesized that increased cerebral blood flow (CBF) may account for most of the increased nonrenal nonhepatic blood flow during TM. In this report we describe increased frontal and occipital CBF in TM determined by the electrical impedance plethysmographic methodology known as rheoencephalography (REG), which allows noninvasive, nondisturbing, continuous CBF monitoring. We also report high correlation between increased CBF and decreased cerebrovascular resistance (CVR) during TM, suggesting that a contributing vascular mechanism to the increased CBF may be decreased CVR. Because only a small amount of stage 1 sleep was observed during TM and because stage 1 sleep has been reported to be accompanied by decreased CBF, we believe that sleep did not contribute to the CBF increase. The data of this study are consistent with the hypothesis that blood flow changes during TM comprise a patterned response subserving needs of increased cerebral activity.

  20. 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.

  1. 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.

  2. Hydrokinetic approach to large-scale cardiovascular blood flow

    NASA Astrophysics Data System (ADS)

    Melchionna, Simone; Bernaschi, Massimo; Succi, Sauro; Kaxiras, Efthimios; Rybicki, Frank J.; Mitsouras, Dimitris; Coskun, Ahmet U.; Feldman, Charles L.

    2010-03-01

    We present a computational method for commodity hardware-based clinical cardiovascular diagnosis based on accurate simulation of cardiovascular blood flow. Our approach leverages the flexibility of the Lattice Boltzmann method to implementation on high-performance, commodity hardware, such as Graphical Processing Units. We developed the procedure for the analysis of real-life cardiovascular blood flow case studies, namely, anatomic data acquisition, geometry and mesh generation, flow simulation and data analysis and visualization. We demonstrate the usefulness of our computational tool through a set of large-scale simulations of the flow patterns associated with the arterial tree of a patient which involves two hundred million computational cells. The simulations show evidence of a very rich and heterogeneous endothelial shear stress pattern (ESS), a quantity of recognized key relevance to the localization and progression of major cardiovascular diseases, such as atherosclerosis, and set the stage for future studies involving pulsatile flows.

  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. Pulmonary blood flow distribution after banding of pulmonary artery.

    PubMed Central

    Samánek, M; Fiser, B; Ruth, C; Tůma, S; Hucín, B

    1975-01-01

    Radioisotope lung scanning was used to investigate the distribution of pulmonary blood flow after banding of the pulmonary artery in children with a left-to-right shunt and pulmonary hypertension. An abnormal distribution of blood flow in the lung on the side of the operation approach was observed in all patients in the first three weeks following surgery. Abnormalities were still observed in 17 of 21 children 10 months to more than 8 years after the banding operation. There was no significant relation between the occurrence of these abnormalities and time after surgery. Diminished flow to the zones of the right lung was observed less frequently. The incidence of abnormalities in flow distribution was also high preoperatively. Respiratory complications in infants with large left-to-right shunts were considered to be responsible for most of the abnormal blood flow distributions observed. Radioactive lung scanning was found to be a valuable diagnostic method in the early and late postoperative period in infants and small children. It was more sensitive than the other techniques used in revealing deviation of blood flow from one lung in those cases with shifting of the applied band. Images PMID:1111558

  5. 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

  6. Blood flow mechanics in cardiovascular development.

    PubMed

    Boselli, Francesco; Freund, Jonathan B; Vermot, Julien

    2015-07-01

    Hemodynamic forces are fundamental to development. Indeed, much of cardiovascular morphogenesis reflects a two-way interaction between mechanical forces and the gene network activated in endothelial cells via mechanotransduction feedback loops. As these interactions are becoming better understood in different model organisms, it is possible to identify common mechanogenetic rules, which are strikingly conserved and shared in many tissues and species. Here, we discuss recent findings showing how hemodynamic forces potentially modulate cardiovascular development as well as the underlying fluid and tissue mechanics, with special attention given to the flow characteristics that are unique to the small scales of embryos.

  7. 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

  8. Multiple equilibrium states for blood flow in microvascular networks

    NASA Astrophysics Data System (ADS)

    Pollock-Muskin, Halley; Diehl, Cecilia; Mohamed, Nora; Karst, Nathan; Geddes, John; Storey, Brian

    2015-11-01

    When blood flows through a vessel bifurcation at the microvascular scale, the hematocrits in the downstream daughter vessels are generally not equal. This phenomenon, known as plasma skimming, can cause heterogeneity in the distribution of red blood cells inside a vessel network. Using established models for plasma skimming, we investigate the equilibrium states in a microvascular network with simple topologies. We find that even simple networks can have multiple equilibrium states for the flow rates and distributions of red blood cells inside the network for fixed inlet conditions. In a ladder network, we find that for certain inlet conditions the network can have 2N observable equilibrium states where N is the number of rungs in the ladder. For ladders with even just a few rungs, the complex equilibrium curves make it seemingly impossible to set the internal state of the network by controlling the inlet flows. Microfluidic experiments are being used to confirm the model predictions.

  9. 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

  10. Heart blood flow simulation: a perspective review.

    PubMed

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

    2016-08-25

    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

  11. The flow of human blood through capillary tubes.

    PubMed Central

    Sirs, J A

    1991-01-01

    1. The current interpretation of in vivo blood flow is mainly based on the Hagen-Poiseuille equation, although blood is not a Newtonian fluid. In this paper, experimental pressure-flow curves of blood are explained on the basis that the viscosity of the blood is the sum of two components, a Newtonian viscosity term, N, and an anomalous viscosity term equal to A/(B + D), where A and B are constants, and D the shear rate. 2. To a first approximation, blood flow in capillary tubes, comparable to that in vivo, can be deduced if the applied pressure in Poiseuille's equation is reduced by an effective back-pressure, p, equal to 8Al/3R, where l is the length of the capillary tube, and R its radius. 3. The theory explains the progressive change, from a parabolic velocity profile in large vessels, to a flattened profile in small vessels, as observed in vivo. 4. Experimental evidence is given that p is proportional to the length, and increases with decrease of R. The effect of the anomalous viscosity coefficient A was studied by varying the haematocrit, fibrinogen level, erythrocyte flexibility and temperature. 5. As the tube bore is decreased, the Fahraeus-Lindqvist effect decreases N, but this is offset by an increase of the anomalous component, A. This results, at lower pressures, in an increase of the effective blood viscosity in small vessels and of the peripheral resistance, and, at higher pressures, in a decrease of the effective blood viscosity. 5. Blood flow is proportional to the radius to the power n, where n is a variable that increases with increase of A and decrease of the applied pressure. PMID:1798043

  12. Sexual experience blocks the ability of clitoral stimulation to induce a conditioned place preference in the rat.

    PubMed

    Parada, M; Jafari, N; Pfaus, J G

    2013-07-01

    We have previously established the rewarding value of clitoral stimulation (CLS) through the demonstration that manual, distributed, CLS induces a significant conditioned place preference (CPP) and conditioned partner preference in naïve, hormonally primed and non-hormonally primed rats. The present experiment asks whether previous sexual experience might inhibit the ability of clitoral stimulation to induce a conditioned place preference. Female Long-Evans rats were ovariectomized and treated with 10 μg of estradiol benzoate (EB) 48 h and 500 μg of progesterone (P) 4h prior to receiving either 0, 1, or 5 consecutive copulatory sessions with a sexually vigorous male. Each copulatory session ended when females received at least 1 ejaculation. Females then experienced 10 alternating trials of distributed CLS or no CLS paired with one side of a non-biased CPP box under the same hormone-priming regimen. Females that experienced 5 consecutive copulatory sessions did not develop a significant place preference indicated by both a preference score (the proportion of time spent in the reinforced chamber) and a difference score (time in the non-reinforced chamber minus the time in the reinforced chamber) compared prior to and following the 10 conditioning trials. This suggests that repeated copulatory experience might induce a desensitization of the genitosensory circuit since copulation includes both clitoral, and vaginocervical stimulation from mounts plus intromissions. Alternatively, repeated sexual experience prior to conditioning may generate a UCS pre-exposure effect that cannot be altered when manual clitoral stimulation is paired with a new environment.

  13. Full dynamics of a red blood cell in shear flow.

    PubMed

    Dupire, Jules; Socol, Marius; Viallat, Annie

    2012-12-18

    At the cellular scale, blood fluidity and mass transport depend on the dynamics of red blood cells in blood flow, specifically on their deformation and orientation. These dynamics are governed by cellular rheological properties, such as internal viscosity and cytoskeleton elasticity. In diseases in which cell rheology is altered genetically or by parasitic invasion or by changes in the microenvironment, blood flow may be severely impaired. The nonlinear interplay between cell rheology and flow may generate complex dynamics, which remain largely unexplored experimentally. Under simple shear flow, only two motions, "tumbling" and "tank-treading," have been described experimentally and relate to cell mechanics. Here, we elucidate the full dynamics of red blood cells in shear flow by coupling two videomicroscopy approaches providing multidirectional pictures of cells, and we analyze the mechanical origin of the observed dynamics. We show that contrary to common belief, when red blood cells flip into the flow, their orientation is determined by the shear rate. We discuss the "rolling" motion, similar to a rolling wheel. This motion, which permits the cells to avoid energetically costly deformations, is a true signature of the cytoskeleton elasticity. We highlight a hysteresis cycle and two transient dynamics driven by the shear rate: an intermittent regime during the "tank-treading-to-flipping" transition and a Frisbee-like "spinning" regime during the "rolling-to-tank-treading" transition. Finally, we reveal that the biconcave red cell shape is highly stable under moderate shear stresses, and we interpret this result in terms of stress-free shape and elastic buckling. PMID:23213229

  14. Fontan Outcomes and Pulmonary Blood Flow at Birth.

    PubMed

    Evans, William N; Acherman, Ruben J; Reardon, Leigh C; Ciccolo, Michael L; Galindo, Alvaro; Rothman, Abraham; Winn, Brody J; Yumiaco, Noel S; Restrepo, Humberto

    2016-01-01

    We previously noted, in a small group of post-Fontan patients, a possible association between hepatic fibrosis scores and the status of pulmonary blood flow at birth. To further explore this observation, we examined data from all Fontan patients seen in our center from July 2010 to March 2015. We identified 200 patients for analysis. Of the 200 patients, 56 underwent transvenous-hepatic biopsy. Of the 200 patients, 13 (6.5%) had protein-losing enteropathy. We divided both the 56 biopsy patients and the entire cohort of 200 patients into 4 groups: (1) unobstructed pulmonary blood flow at birth with functional left ventricles, (2) unobstructed pulmonary blood flow at birth with functional right ventricles, (3) obstructed pulmonary blood flow at birth with functional left ventricles, and (4) obstructed pulmonary blood flow at birth with functional right ventricles. Analysis of the 56 liver-biopsy patient groups showed median hepatic total-fibrosis scores for the 4 groups of 2 (0-6), 2 (0-8), 3 (2-6), and 4 (1-8), respectively, with statistical significance between groups 4 and 1 (p = 0.031). For the entire cohort of 200 patients, we analyzed the incidence of protein-losing enteropathy for each of the four groups and found protein-losing enteropathy percent occurrences of 0, 2.9, 8.8, and 16.1, respectively, with statistical significance between groups 4 and 2 (p = 0.031) and between groups 4 and 1 (p = 0.025). A history of obstructed pulmonary blood flow at birth, coupled with a functional right ventricle, may predict a poorer long-term Fontan outcome.

  15. 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

  16. 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.

  17. Vasodilator interactions in skeletal muscle blood flow regulation

    PubMed Central

    Hellsten, Y; Nyberg, M; Jensen, L G; Mortensen, S P

    2012-01-01

    During exercise, oxygen delivery to skeletal muscle is elevated to meet the increased oxygen demand. The increase in blood flow to skeletal muscle is achieved by vasodilators formed locally in the muscle tissue, either on the intraluminal or on the extraluminal side of the blood vessels. A number of vasodilators have been shown to bring about this increase in blood flow and, importantly, interactions between these compounds seem to be essential for the precise regulation of blood flow. Two compounds stand out as central in these vasodilator interactions: nitric oxide (NO) and prostacyclin. These two vasodilators are both stimulated by several compounds, e.g. adenosine, ATP, acetylcholine and bradykinin, and are affected by mechanically induced signals, such as shear stress. NO and prostacyclin have also been shown to interact in a redundant manner where one system can take over when formation of the other is compromised. Although numerous studies have examined the role of single and multiple pharmacological inhibition of different vasodilator systems, and important vasodilators and interactions have been identified, a large part of the exercise hyperaemic response remains unexplained. It is plausible that this remaining hyperaemia may be explained by cAMP- and cGMP-independent smooth muscle relaxation, such as effects of endothelial derived hyperpolarization factors (EDHFs) or through metabolic modulation of sympathetic effects. The nature and role of EDHF as well as potential novel mechanisms in muscle blood flow regulation remain to be further explored to fully elucidate the regulation of exercise hyperaemia. PMID:22988140

  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

    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.

  20. Quantification of regional blood flow to canine flexor tendons

    SciTech Connect

    Weidman, K.A.; Simonet, W.T.; Wood, M.B.; Cooney, W.P.; Ilstrup, D.M.

    1984-01-01

    Although the blood supply and the microcirculation of flexor tendons have been studied and defined extensively using qualitative methods, the quantitative assessment of blood flow has been lacking because of the limitations of the available experimental techniques. The authors studied the regional blood supply to the flexor tendons of dogs by the technique of radionuclide-labeled microspheres. Seven adult mongrel dogs were used. Microsphere injection and tissue-counting techniques previously used for other tissues were applied. Samples of proximal, isthmus, and distal portions of the profundus and superficialis flexor tendons were harvested from each digital unit of available limbs from each dog. Mean (+/- SE) flows (ml/100 g dry tissue/min) were proximal profundus 1.78 +/- 0.60 and superficialis 7.10 +/- 1.50. The differences were significant. The study suggests that regional variation in blood flow to canine digital flexor tendons exists, so that a single value for blood flow to these tendons is not relevant. Furthermore, the study supports the concept of dual (vascular and synovial) nutrition to the digital flexor tendons in dogs. These observations may have implications regarding tendon repair techniques.

  1. 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

  2. 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.

  3. Atlas of computerized blood flow analysis in bone disease.

    PubMed

    Gandsman, E J; Deutsch, S D; Tyson, I B

    1983-11-01

    The role of computerized blood flow analysis in routine bone scanning is reviewed. Cases illustrating the technique include proven diagnoses of toxic synovitis, Legg-Perthes disease, arthritis, avascular necrosis of the hip, fractures, benign and malignant tumors, Paget's disease, cellulitis, osteomyelitis, and shin splints. Several examples also show the use of the technique in monitoring treatment. The use of quantitative data from the blood flow, bone uptake phase, and static images suggests specific diagnostic patterns for each of the diseases presented in this atlas. Thus, this technique enables increased accuracy in the interpretation of the radionuclide bone scan.

  4. Sympathetic restraint of muscle blood flow during hypoxic exercise

    PubMed Central

    Stickland, Michael K.; Smith, Curtis A.; Soriano, Benjamin J.; Dempsey, Jerome A.

    2009-01-01

    Control of exercising muscle blood flow is a balance between local vasodilatory factors and the increase in global sympathetic vasoconstrictor outflow. Hypoxia has been shown to potentiate the muscle sympathetic nerve response to exercise, potentially limiting the increase in muscle blood flow. Accordingly, we investigated sympathetic restraint to exercising muscle during whole body exercise in hypoxia. Six dogs chronically instrumented with ascending aortic and hindlimb flow probes and a terminal aortic catheter were studied at rest and mild [2.5 miles/h (mph), 5% grade] and moderate (4.0 mph, 10% grade) exercise while breathing room air or hypoxia (PaO2 ∼45 mmHg) in the intact control condition and following systemic α-adrenergic blockade (phentolamine). Hypoxia caused an increase in cardiac output (CO), hindlimb flow (FlowL), and blood pressure (BP), while total (CondT) and hindlimb conductance (CondL) were unchanged at rest and mild exercise but increased with moderate exercise. During both mild and moderate exercise, α-blockade in normoxia resulted in significant vasodilation as evidenced by increases in CO (10%), FlowL (17%), CondT (33%), CondL (43%), and a decrease in BP (−18%), with the increase in CondL greater than the increase in CondT during mild exercise. Compared with the normoxic response, α-blockade in hypoxia during exercise resulted in a significantly greater increase in CondT (59%) and CondL (74%) and a correspondingly greater decrease in BP (−34%) from baseline. These findings indicate that there is considerable hypoxia-induced sympathetic restraint of muscle blood flow during both mild and moderate exercise, which helps to maintain arterial blood pressure in hypoxia. PMID:19297541

  5. Impaired endothelial function and blood flow in repetitive strain injury.

    PubMed

    Brunnekreef, J; Brunnekreef, J J; Benda, N; Benda, N M M; Schreuder, T; Schreuder, T H A; Hopman, M; Hopman, M T E; Thijssen, D; Thijssen, D H J

    2012-10-01

    Repetitive Strain Injury (RSI) is a disabling upper extremity overuse injury that may be associated with pathophysiological changes in the vasculature. In this study we investigated whether RSI is associated with endothelial dysfunction and impaired exercise-induced blood flow in the affected forearm. 10 patients with RSI (age, 40.2 ± 10.3; BMI, 23.8 ± 3.3) and 10 gender- and age-matched control subjects (age, 38.0 ± 12.4; BMI, 22.7 ± 3.4) participated in this study. Brachial artery blood flow was measured at rest and during 3-min periods of isometric handgrip exercise at 15%, 30% and 45% of the individual maximal voluntary contraction. Brachial artery endothelial function was assessed as the flow mediated dilation (FMD), by measuring brachial artery diameter and velocity before and after 5-min ischemic occlusion. We found a lower exercise-induced brachial artery blood flow in patients with RSI than in controls (p=0.04). Brachial artery FMD was significantly lower in patients with RSI than in controls (p<0.01), whilst a lower FMD was also found in patient with unilateral RSI when comparing the affected arm with the non-affected arm (p=0.04). Our results suggest that patients with RSI have an attenuated exercise-induced blood flow and an impaired endothelial function in the affected arm. These findings importantly improve our understanding of the pathophysiological mechanism of RSI.

  6. Accurate blood flow measurements: are artificial tracers necessary?

    PubMed

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

    2012-01-01

    Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case), as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (approximately 33%, based on in vitro reference measurements). These results suggest that flow characteristics reported in literature cannot be compared without a careful evaluation of the imaging characteristics. A method to predict the expected flow averaging behavior for a particular facility is presented.

  7. 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

  8. 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.

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

    PubMed

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

    2003-05-01

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

  10. Computational Biorheology of Human Blood Flow in Health and Disease

    PubMed Central

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

    2014-01-01

    Hematologic disorders arising from infectious diseases, hereditary factors and environmental influences can lead to, and can be influenced by, significant changes in the shape, mechanical and physical properties of red blood cells (RBCs), and the biorheology of blood flow. Hence, modeling of hematologic disorders should take into account the multiphase nature of blood flow, especially in arterioles and capillaries. We present here an overview of a general computational framework based on dissipative particle dynamics (DPD) which has broad applicability in cell biophysics with implications for diagnostics, therapeutics and drug efficacy assessments for a wide variety of human diseases. This computational approach, validated by independent experimental results, is capable of modeling the biorheology of whole blood and its individual components during blood flow so as to investigate cell mechanistic processes in health and disease. DPD is a Lagrangian method that can be derived from systematic coarse-graining of molecular dynamics but can scale efficiently up to arterioles and can also be used to model RBCs down to the spectrin level. We start from experimental measurements of a single RBC to extract the relevant biophysical parameters, using single-cell measurements involving such methods as optical tweezers, atomic force microscopy and micropipette aspiration, and cell-population experiments involving microfluidic devices. We then use these validated RBC models to predict the biorheological behavior of whole blood in healthy or pathological states, and compare the simulations with experimental results involving apparent viscosity and other relevant parameters. While the approach discussed here is sufficiently general to address a broad spectrum of hematologic disorders including certain types of cancer, this paper specifically deals with results obtained using this computational framework for blood flow in malaria and sickle cell anemia. PMID:24419829

  11. 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.

  12. 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

  13. 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.

  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. 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

  16. 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

  17. 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

  18. Method and apparatus for characterizing blood flow through the heart

    SciTech Connect

    Dam, N.G.; Gray, R.I.; Kramer, H.H.; Picunko, T.

    1981-10-13

    An automated method and improved device provide a measurement of blood flow through the heart by the detection and analysis of radioactivity emitted by a radioactive tracer introduced into a patient's bloodstream. Real time, cardiac cycle by cardiac cycle information is processed and displayed to provide diagnostically useful information on an essentially ongoing basis as the patient is being tested.

  19. Development of a miniature intraventricular axial flow blood pump.

    PubMed

    Yamazaki, K; Umezu, M; Koyanagi, H; Outa, E; Ogino, S; Otake, Y; Shiozaki, H; Fujimoto, T; Tagusari, O; Kitamura, M

    1993-01-01

    A new intraventricular axial flow blood pump has been designed and developed as a totally implantable left ventricular assist device (LVAD). This pump consists of an impeller combined with a guide-vane, a tube housing, and a DC motor. The pump is introduced into the LV cavity through the LV apex, and the outlet cannula is passed antegrade across the aortic valve. Blood is withdrawn from the LV through the inlet ports at the pump base, and discharged to the ascending aorta. Our newly developed axial flow pump system has the following advantages: 1) it is a simple and compact system, 2) minimal blood stasis both in the device and the LV cavity, 3) minimal blood contacting surface of the pump, 4) easy accessibility with a less invasive surgical procedure, and 5) low cost. A pump flow > 5 L/min was obtained against 100 mmHg differential pressure in the mock circulatory system. The pump could produce a passive pulsatile flow effect with a beating heart more efficiently than other non-pulsatile pumps because of minimal pressure drop and inertia along the bypass tract. Anatomic fit studies using dissected hearts of dilated cardiomyopathy (DCM) cadavers showed that this pump could smoothly pass through the aortic valve without any interference with mitral valve function. Recently, a dynamic pressure groove bearing and a miniature lip seal have been developed. The dynamic pressure groove bearing has a simple structure and acts as a pressure resistant sealing mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. 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.

  1. 21 CFR 870.2120 - Extravascular blood flow probe.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Extravascular blood flow probe. 870.2120 Section 870.2120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2120...

  2. 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

  3. Gastritis and gastric blood flow in hyperdynamic septic pigs.

    PubMed

    Lucas, C E; Ravikant, T; Walt, A J

    1976-01-01

    The present study was designed to determine the gastric hemodynamics in a septic model that causes both a hyperdynamic state and acute erosive gastritis. Sepsis was established in twelve pigs by the intramuscular shank injection of Pastuerella multocida (42 X 10(8) colonies) in triptose phosphate broth; four pigs received sterile broth injections (shams) and eight received sterile saline injections (controls). After 18 hours, cardiac output was measured by both the cardiogreen dilution technic and the radioactive microsphere dilution technic; cardiac output was then compared to total and regional gastric blood flow measured by the raioactive microsphere entrapment technic. Acute erosive gastritis developed in septic pigs in the fundus and body of the stomach; the antrum was spared. Cardiac output was significantly increased in septic pigs compared with sham and control pigs. Total gastric blood flow and regional blood flow to the fundus, body, and antrum were also increased in direct proportion to the increase in cardiac output. These data suggest that acute erosive gastritis is primarily due to an end-organ cellular insult from sepsis and is not primarily due to a decrease or redistribution in gastric blood flow.

  4. 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…

  5. [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.

  6. 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

  7. Heat transfer to blood flow in a small tube.

    PubMed

    Wang, C Y

    2008-04-01

    Blood flow in a small tube (30-1000 mum) can be successfully modeled by the two-fluid model. The fully developed, constant heat flux convective heat transfer problem is studied. The velocity and temperature profiles are determined in closed form. Formulas for friction-factor-Reynolds number product, axial temperature gradient, and Nusselt number are found.

  8. Doppler instrumentation for measuring blood velocity and flow

    NASA Technical Reports Server (NTRS)

    Gill, R. W.; Hottinger, C. F.; Meindl, J. D.

    1975-01-01

    Doppler ultrasonic blood flowmeters are reviewed in detail. The importance of measurement accuracy for transcutaneous flowmeters and their clinical application is stressed. Doppler imaging was combined with conventional pulse echo imaging, and diagnostic information was extracted from flow signals. The range and extent of applications of Doppler instruments was also presented.

  9. Limb Blood Flow After Class 4 Laser Therapy

    PubMed Central

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

    2012-01-01

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

  10. Clitoral stimulation modulates appetitive sexual behavior and facilitates reproduction in rats.

    PubMed

    Cibrian-Llanderal, Tamara; Tecamachaltzi-Silvaran, Miriam; Triana-Del Rio, Rodrigo; Pfaus, James G; Manzo, Jorge; Coria-Avila, Genaro A

    2010-05-11

    In rats, sexual reward, appetitive sexual behaviors and reproduction are modulated by the amount and rate of vaginocervical stimulation. Here the effect of clitoral stimulation (CLS) on proceptivity was assessed. In Exp 1, ovariectomized, hormone-primed Wistar females formed three groups: G1 (1 CLS every second), G2 (1 CLS every 5s) and G3 (no CLS). Precopulatory CLS consisted of 5cycles of 1min of stimulation with the tip of a cotton swab connected to a vibrator device, followed by 1-2min of rest. CLS increased proceptive behavior in G1 compared to G2, but not compared to G3. In Exp 2, gonadally-intact rats in late proestrous received CLS prior to copulation. No differences in sexual behavior were detected between the groups, but CLS enhanced reproduction in females that received >9 intromissions. 28, 66 and 10% of females became pregnant in G1, G2, and G3, respectively. These data indicate that precopulatory CLS affects proceptive behaviors depending on the pattern and rhythm of stimulation in hormone-primed females. In virgin rats that have received sufficient vagino cervical stimulation CLS also increases fertility.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. Mechanical determinants of myocardial blood flow and its distribution.

    PubMed

    Archie, J P

    1975-07-01

    There are two mechanical determinants of coronary blood flow and its distribution: resistance and pressure gradient. Resistance is determined by blood viscosity and the anatomy and geometry of the coronary vascular bed. The coronary vascular pressure gradient is the difference between aortic root pressure and intramyocardial pressure. A number of factors such as coronary atherosclerosis, ventricular hypertrophy, and myocardial edema may adversely affect the determinants of coronary flow before, during, or after cardiopulmonary bypass, thereby lowering or eliminating regional or local coronary reserve and promoting the likelihood of a myocardial ischemic injury. The subendocardial layers of the left ventricle appear to be more vulnerable, perhaps in part because they depend entirely on diastolic coronary flow.

  17. 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

  18. 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

  19. 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.

  20. Fluid ingestion during exercise increases skin blood flow independent of increases in blood volume.

    PubMed

    Montain, S J; Coyle, E F

    1992-09-01

    The purpose of this experiment was to determine whether fluid ingestion attenuates the hyperthermia and cardiovascular drift that occurs during exercise dehydration due to increases in blood volume. In addition, forearm blood flow, which is indicative of skin blood flow, was measured to determine whether the attenuation of hyperthermia and cardiovascular drift during exercise with fluid ingestion is due to higher skin blood flow. On three different occasions, seven trained cyclists [mean age, body weight, and maximum oxygen uptake: 23 +/- 3 yr, 73.9 +/- 10.5 kg, and 4.75 +/- 0.34 (SD) l/min, respectively] cycled at a power output equal to 62-67% maximum oxygen uptake for 2 h in a warm environment (33 degrees C, 50% relative humidity, wind speed 2.5 m/s). During exercise, they randomly received no fluid (NF) or a volume of a carbohydrate-electrolyte fluid replacement solution (FR) sufficient to replace 80 +/- 2% of sweat loss or were intravenously infused with 5.3 ml/kg of a blood volume expander (BVX; 6% dextran in saline). The infusion of 398 +/- 23 ml of BVX maintained blood volume at levels similar to that when 2,404 +/- 103 ml of fluid were ingested during FR and greater than that when no fluid was ingested during the 2nd h of exercise (P less than 0.05). However, BVX and NF resulted in similar esophageal and rectal temperatures, forearm blood flow, and elevations in serum osmolality and sodium concentration during 2 h of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Diagnosis Of Regional Cerebral Blood Flow By Partitioning.

    NASA Astrophysics Data System (ADS)

    Zemcov, Alexander; Sansone, Joseph; Barclay, Laurie

    1986-06-01

    A scheme is proposed for discriminating between patients with Alzheimer's disease and age-matched normals using regional cerebral blood flow data measured by the noninvasive Xe-133 inhalation technique. Regional blood flows which are known to be decreased in Alzheimer's disease but are known to overlap to some degree with flows from normals are usually interpreted subjectively. In the scheme presented these flow values are used to form cumulative distributions for each subject group and for each detector. Pairs of distributions for homologous detectors are compared and the blood flow value at which this difference is the greatest is identified as the cutoff value. The 32 pairs of distributions give rise to 32 cutoff values. For each individual and detector the flow values are compared to their respective cutoffs. Those flow values which exceed their cutoff are assigned a 1 and those that are less than the cutoff a 0. For each subject and hemisphere these binary values are cummed where the sums for each hemisphere range in value from 0 to 16. A new cutoff for this sum is chosen and the sums for each patient are compared to this value. In the two groups sited the cutoff was set at a sum of 12 for each hemisphere. The majority of the normals had hemispheric sums of 14 or greater. The patients with Alzheimer's disease had sums that were equally distributed over the whole range of possible sums. This result indicated that the classification scheme was unlikely to classify a normal as an abnormal. However, there was a significant likelihood that an abnormal could be classified as a normal. These two qualities are defined as the sensitivity and specificity respectively. The test was sensitive (90%) but less specific (70%). The results of this classification scheme compared favorably with the subjective interpretation of experienced readers.

  6. Methods for blood flow measurements using ultrasound contrast agents

    NASA Astrophysics Data System (ADS)

    Fowlkes, J. Brian

    2003-10-01

    Blood flow measurements using ultrasound contrast agents are being investigated for myocardial perfusion and more recently in other organ systems. The methods are based largely on the relative increase in echogenicity due to the concentration of bubbles present in the ultrasound beam. In the simplest form, regional differences in blood volume can be inferred but the possibility exists to extract perfusion from the transit of contrast agent through tissue. Perfusion measurements rely on determining the flux of blood through a tissue volume and as such require knowledge of the fractional blood volume (FBV), i.e., ml blood/g tissue and the rate of exchange, commonly measured as the mean transit time (MTT). This presentation will discuss methods of determining each of these values and their combination to estimate tissue perfusion. Underlying principles of indicator-dilution theory will be provided in the context of ultrasound contrast agents. Current methods for determining MTT will include imaging of the intravenous bolus, in-plane contrast disruption with interval and real-time contrast recovery imaging, and control of contrast agent flow using arterial disruption (contrast interruption). The advantages and limitations of the methods will be examined along with current applications. [Work supported in part by NIH.

  7. 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.

  8. 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.

  9. Blood flow dynamics under venipuncture and viscosity estimation from pressure and flow variations

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Makov, Yu. N.; Gurbatov, S. N.

    2013-01-01

    We have calculated the nonstationary flow of a viscous liquid in a narrow tube under the action of pressure variations with time. Such a flow accompanies venipuncture the procedure of taking a sample from a vein with a hypodermic needle. We show how the changes in the flow characterstics during venipuncture make it possible to actively estimate viscosity. This method is "nonperturbative" for blood in the sense that the measurement process weakly affects the measured quantity. It may find application in medicine.

  10. Occlusion-free Blood Flow Animation with Wall Thickness Visualization.

    PubMed

    Lawonn, Kai; Glaßer, Sylvia; Vilanova, Anna; Preim, Bernhard; Isenberg, Tobias

    2016-01-01

    We present the first visualization tool that combines pathlines from blood flow and wall thickness information. Our method uses illustrative techniques to provide occlusion-free visualization of the flow. We thus offer medical researchers an effective visual analysis tool for aneurysm treatment risk assessment. Such aneurysms bear a high risk of rupture and significant treatment-related risks. Therefore, to get a fully informed decision it is essential to both investigate the vessel morphology and the hemodynamic data. Ongoing research emphasizes the importance of analyzing the wall thickness in risk assessment. Our combination of blood flow visualization and wall thickness representation is a significant improvement for the exploration and analysis of aneurysms. As all presented information is spatially intertwined, occlusion problems occur. We solve these occlusion problems by dynamic cutaway surfaces. We combine this approach with a glyph-based blood flow representation and a visual mapping of wall thickness onto the vessel surface. We developed a GPU-based implementation of our visualizations which facilitates wall thickness analysis through real-time rendering and flexible interactive data exploration mechanisms. We designed our techniques in collaboration with domain experts, and we provide details about the evaluation of the technique and tool.

  11. Nephron blood flow dynamics measured by laser speckle contrast imaging.

    PubMed

    Holstein-Rathlou, Niels-Henrik; Sosnovtseva, Olga V; Pavlov, Alexey N; Cupples, William A; Sorensen, Charlotte Mehlin; Marsh, Donald J

    2011-02-01

    Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50-100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney.

  12. 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.

  13. 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)

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

    PubMed

    Jang, Jaeseong; Ahn, Chi Young; Jeon, Kiwan; Heo, Jung; Lee, DongHak; Joo, Chulmin; Choi, Jung-il; Seo, Jin Keun

    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

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. Pressure Gradient Estimation Based on Ultrasonic Blood Flow Measurement

    NASA Astrophysics Data System (ADS)

    Nitta, Naotaka; Homma, Kazuhiro; Shiina, Tsuyoshi

    2006-05-01

    Mechanical load to the blood vessel wall, such as shear stress and pressure, which occurs in blood flow dynamics, contribute greatly to plaque rupture in arteriosclerosis and to biochemical activation of endothelial cells. Therefore, noninvasive estimations of these mechanical loads are able to provide useful information for the prevention of vascular diseases. Although the pressure is the dominant component of mechanical load, for practical purposes, the pressure gradient is also often important. So far, we have investigated the estimation of the kinematic viscosity coefficient using a combination of the Navier-Stokes equations and ultrasonic velocity measurement. In this paper, a method for pressure gradient estimation using the estimated kinematic viscosity coefficient is proposed. The validity of the proposed method was investigated on the basis of the analysis with the data obtained by computer simulation and a flow phantom experiment. These results revealed that the proposed method can provide a valid estimation of the pressure gradient.

  20. 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.

  1. One dimensional modeling of blood flow in large networks

    NASA Astrophysics Data System (ADS)

    Wang, Xiaofei; Lagree, Pierre-Yves; Fullana, Jose-Maria; Lorthois, Sylvie; Institut de Mecanique des Fluides de Toulouse Collaboration

    2014-11-01

    A fast and valid simulation of blood flow in large networks of vessels can be achieved with a one-dimensional viscoelastic model. In this paper, we developed a parallel code with this model and computed several networks: a circle of arteries, a human systemic network with 55 arteries and a vascular network of mouse kidney with more than one thousand segments. The numerical results were verified and the speedup of parallel computing was tested on multi-core computers. The evolution of pressure distributions in all the networks were visualized and we can see clearly the propagation patterns of the waves. This provides us a convenient tool to simulate blood flow in networks.

  2. Regulation of blood flow in the retinal trilaminar vascular network.

    PubMed

    Kornfield, Tess E; Newman, Eric A

    2014-08-20

    Light stimulation evokes neuronal activity in the retina, resulting in the dilation of retinal blood vessels and increased blood flow. This response, named functional hyperemia, brings oxygen and nutrients to active neurons. However, it remains unclear which vessels mediate functional hyperemia. We have characterized blood flow regulation in the rat retina in vivo by measuring changes in retinal vessel diameter and red blood cell (RBC) flux evoked by a flickering light stimulus. We found that, in first- and second-order arterioles, flicker evoked large (7.5 and 5.0%), rapid (0.73 and 0.70 s), and consistent dilations. Flicker-evoked dilations in capillaries were smaller (2.0%) and tended to have a slower onset (0.97 s), whereas dilations in venules were smaller (1.0%) and slower (1.06 s) still. The proximity of pericyte somata did not predict capillary dilation amplitude. Expression of the contractile protein α-smooth muscle actin was high in arterioles and low in capillaries. Unexpectedly, we found that blood flow in the three vascular layers was differentially regulated. Flicker stimulation evoked far larger dilations and RBC flux increases in the intermediate layer capillaries than in the superficial and deep layer capillaries (2.6 vs 0.9 and 0.7% dilation; 25.7 vs 0.8 and 11.3% RBC flux increase). These results indicate that functional hyperemia in the retina is driven primarily by active dilation of arterioles. The dilation of intermediate layer capillaries is likely mediated by active mechanisms as well. The physiological consequences of differential regulation in the three vascular layers are discussed.

  3. Regulation of Blood Flow in the Retinal Trilaminar Vascular Network

    PubMed Central

    Kornfield, Tess E.

    2014-01-01

    Light stimulation evokes neuronal activity in the retina, resulting in the dilation of retinal blood vessels and increased blood flow. This response, named functional hyperemia, brings oxygen and nutrients to active neurons. However, it remains unclear which vessels mediate functional hyperemia. We have characterized blood flow regulation in the rat retina in vivo by measuring changes in retinal vessel diameter and red blood cell (RBC) flux evoked by a flickering light stimulus. We found that, in first- and second-order arterioles, flicker evoked large (7.5 and 5.0%), rapid (0.73 and 0.70 s), and consistent dilations. Flicker-evoked dilations in capillaries were smaller (2.0%) and tended to have a slower onset (0.97 s), whereas dilations in venules were smaller (1.0%) and slower (1.06 s) still. The proximity of pericyte somata did not predict capillary dilation amplitude. Expression of the contractile protein α-smooth muscle actin was high in arterioles and low in capillaries. Unexpectedly, we found that blood flow in the three vascular layers was differentially regulated. Flicker stimulation evoked far larger dilations and RBC flux increases in the intermediate layer capillaries than in the superficial and deep layer capillaries (2.6 vs 0.9 and 0.7% dilation; 25.7 vs 0.8 and 11.3% RBC flux increase). These results indicate that functional hyperemia in the retina is driven primarily by active dilation of arterioles. The dilation of intermediate layer capillaries is likely mediated by active mechanisms as well. The physiological consequences of differential regulation in the three vascular layers are discussed. PMID:25143628

  4. 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

  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. Contrast enhanced computerized tomography measurement of vascular blood flow

    NASA Astrophysics Data System (ADS)

    Sixou, B.; Boissel, L.; Sigovan, M.

    2016-10-01

    In this work, we study the measurement of blood velocity with contrast enhanced computed tomography. The transport equation is used as a constraint to obtain stable solutions. The inverse problem is formulated as an optimal control problem. The density of the contrast agent is reconstructed together with the flow field. The inversion scheme is tested on a simple phantom. The reconstruction of the velocity is improved but the convergence of the method is slow.

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

    NASA Technical Reports Server (NTRS)

    Ploutz-Snyder, Lori

    2009-01-01

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

  8. 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.

  9. Frequency response characteristics of cerebral blood flow autoregulation in rats.

    PubMed

    Kolb, Brittany; Rotella, Diane L; Stauss, Harald M

    2007-01-01

    Transfer function analysis of blood pressure and cerebral blood flow in humans demonstrated that cerebrovascular autoregulation operates most effectively for slow fluctuations in perfusion pressure, not exceeding a frequency of approximately 0.15 Hz. No information on the dynamic properties of cerebrovascular autoregulation is available in rats. Therefore, we tested the hypothesis that cerebrovascular autoregulation in rats is also most effective for slow fluctuations in perfusion pressure below 0.15 Hz. Normotensive Wistar-Kyoto rats (n = 10) were instrumented with catheters in the left common carotid artery and jugular vein and flow probes around the right internal carotid artery. During isoflurane anesthesia, fluctuations in cerebral perfusion pressure were elicited by periodically occluding the abdominal aorta at eight frequencies ranging from 0.008 Hz to 0.5 Hz. The protocol was repeated during inhibition of myogenic vascular function (nifedipine, 0.25 mg/kg body wt iv). Increases in cerebral perfusion pressure elicited initial increases in cerebrovascular conductance and decreases in resistance. At low occlusion frequencies (<0.1 Hz), these initial responses were followed by decreases in conductance and increases in resistance that were abolished by nifedipine. At occlusion frequencies of 0.1 Hz and above, the gains of the transfer functions between pressure and blood flow and between pressure and resistance were equally high in the control and nifedipine trial. At occlusion frequencies below 0.1 Hz, the gains of the transfer functions decreased twice as much under control conditions than during nifedipine application. We conclude that dynamic autoregulation of cerebral blood flow is restricted to very low frequencies (<0.1 Hz) in rats.

  10. 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.

  11. Mixing problems in using indicators for measuring regional blood flow

    SciTech Connect

    Ushioda, E.; Nuwayhid, B.; Tabsh, K.; Erkkola, R.; Brinkman, C.R.; Assali, N.S.

    1982-01-01

    A basic requirement for using indicators for measuring blood flow is adequate mixing of the indicator with blood prior to sampling the site. This requirement has been met by depositing the indicator in the heart and sampling from an artery. Recently, authors have injected microspheres into veins and sampled from venous sites. The present studies were designed to investigate the mixing problems in sheep and rabbits by means of Cardio-Green and labeled microspheres. The indicators were injected at different points in the circulatory system, and blood was sampled at different levels of the venous and arterial systems. Results show the following: (a) When an indicator of small molecular size (Cardio-Green) is allowed to pass through the heart chambers, adequate mixing is achieved, yielding accurate and reproducible results. (b) When any indicator (Cardio-Green or microspheres) is injected into veins, and sampling is done at any point in the venous system, mixing is inadequate, yielding flow results which are inconsistent and erratic. (c) For an indicator or large molecular size (microspheres), injecting into the left side of the heart and sampling from arterial sites yield accurate and reproducible results regardless of whether blood is sampled continuously or intermittently.

  12. Unsteady magnetohydrodynamic blood flow through irregular multi-stenosed arteries.

    PubMed

    Mustapha, Norzieha; Amin, Norsarahaida; Chakravarty, Santabrata; Mandal, Prashanta Kumar

    2009-10-01

    Flow of an electrically conducting fluid characterizing blood through the arteries having irregular shaped multi-stenoses in the environment of a uniform transverse magnetic-field is analysed. The flow is considered to be axisymmetric with an outline of the irregular stenoses obtained from a three-dimensional casting of a mild stenosed artery, so that the physical problem becomes more realistic from the physiological point of view. The marker and cell (MAC) and successive-over-relaxation (SOR) methods are respectively used to solve the governing unsteady magnetohydrodynamic (MHD) equations and pressure-Poisson equation quantitatively and to observe the flow separation. The results obtained show that the flow separates mostly towards the downstream of the multi-stenoses. However, the flow separation region keeps on shrinking with the increasing intensity of the magnetic-field which completely disappears with sufficiently large value of the Hartmann number. The present observations certainly have some clinical implications relating to magnetotherapy which help reducing the complex flow separation zones causing flow disorder leading to the formation and progression of the arterial diseases.

  13. Unsteady magnetohydrodynamic blood flow through irregular multi-stenosed arteries.

    PubMed

    Mustapha, Norzieha; Amin, Norsarahaida; Chakravarty, Santabrata; Mandal, Prashanta Kumar

    2009-10-01

    Flow of an electrically conducting fluid characterizing blood through the arteries having irregular shaped multi-stenoses in the environment of a uniform transverse magnetic-field is analysed. The flow is considered to be axisymmetric with an outline of the irregular stenoses obtained from a three-dimensional casting of a mild stenosed artery, so that the physical problem becomes more realistic from the physiological point of view. The marker and cell (MAC) and successive-over-relaxation (SOR) methods are respectively used to solve the governing unsteady magnetohydrodynamic (MHD) equations and pressure-Poisson equation quantitatively and to observe the flow separation. The results obtained show that the flow separates mostly towards the downstream of the multi-stenoses. However, the flow separation region keeps on shrinking with the increasing intensity of the magnetic-field which completely disappears with sufficiently large value of the Hartmann number. The present observations certainly have some clinical implications relating to magnetotherapy which help reducing the complex flow separation zones causing flow disorder leading to the formation and progression of the arterial diseases. PMID:19665698

  14. 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.

  15. Holographic laser Doppler imaging of microvascular blood flow.

    PubMed

    Magnain, C; Castel, A; Boucneau, T; Simonutti, M; Ferezou, I; Rancillac, A; Vitalis, T; Sahel, J A; Paques, M; Atlan, M

    2014-12-01

    We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radio frequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radio frequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range in vitro and imaging of superficial blood perfusion with a spatial resolution of about 10 micrometers in rodent models of cortical and retinal blood flow.

  16. Quantification of blood flow and topology in developing vascular networks.

    PubMed

    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.

  17. Diagnostic yield of blood flow and blood pool studies of the liver

    SciTech Connect

    Azar, M.; Royal, H.D.; Parker, J.A.; Kolodny, G.M.

    1984-01-01

    The accuracy of Tc-99m RBC studies of the liver to diagnose cavernous hemangiomas has been previously reported. The authors have reviewed 82 of these studies performed in the last four years to determine the prevalence of this benign lesion when it is suspected. Studies were performed in patients with focal solid abnormalities of the liver if the patient had no known primary or if there were no definitive clinical or laboratory findings to support the diagnosis of metastatic disease. Blood flow, immediate blood pool and one hour delayed blood pool images were obtained in all patients. The combination of decreased or normal blood flow and markedly increased blood pool is pathognomonic for patients having cavernous hemangiomas. Seventeen percent (14/82) of patients were found to have cavernous hemangiomas of the liver. The remaining patients had metastatic disease (38), abscess (6), hepatomas (6), and miscellaneous diagnosis (11). All patients diagnosed as having cavernous hemangioma have been followed for at least one year. Seven of the remaining patients were lost to medical follow-up. In the series no false positive or false negative results have been obtained; however, false negative cases are anticipated for small or thrombosed hemangiomas. RBC liver studies should be encouraged since 1) the diagnostic yield is high; 2) it is the diagnostic procedure of choice; 3) biopsy of these lesions can be catastrophic; and 4) therapy and prognosis is greatly altered if the liver lesions are proven to be benign.

  18. Effects of caffeine on blood pressure, heart rate, and forearm blood flow during dynamic leg exercise.

    PubMed

    Daniels, J W; Molé, P A; Shaffrath, J D; Stebbins, C L

    1998-07-01

    This study examined the acute effects of caffeine on the cardiovascular system during dynamic leg exercise. Ten trained, caffeine-naive cyclists (7 women and 3 men) were studied at rest and during bicycle ergometry before and after the ingestion of 6 mg/kg caffeine or 6 mg/kg fructose (placebo) with 250 ml of water. After consumption of caffeine or placebo, subjects either rested for 100 min (rest protocol) or rested for 45 min followed by 55 min of cycle ergometry at 65% of maximal oxygen consumption (exercise protocol). Measurement of mean arterial pressure (MAP), forearm blood flow (FBF), heart rate, skin temperature, and rectal temperature and calculation of forearm vascular conductance (FVC) were made at baseline and at 20-min intervals. Plasma ANG II was measured at baseline and at 60 min postingestion in the two exercise protocols. Before exercise, caffeine increased both systolic blood pressure (17%) and MAP (11%) without affecting FBF or FVC. During dynamic exercise, caffeine attenuated the increase in FBF (53%) and FVC (50%) and accentuated exercise-induced increases in ANG II (44%). Systolic blood pressure and MAP were also higher during exercise plus caffeine; however, these increases were secondary to the effects of caffeine on resting blood pressure. No significant differences were observed in heart rate, skin temperature, or rectal temperature. These findings indicate that caffeine can alter the cardiovascular response to dynamic exercise in a manner that may modify regional blood flow and conductance. PMID:9655769

  19. 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.

  20. Uncertainty quantification in coronary blood flow simulations: Impact of geometry, boundary conditions and blood viscosity.

    PubMed

    Sankaran, Sethuraman; Kim, Hyun Jin; Choi, Gilwoo; Taylor, Charles A

    2016-08-16

    Computational fluid dynamic methods are currently being used clinically to simulate blood flow and pressure and predict the functional significance of atherosclerotic lesions in patient-specific models of the coronary arteries extracted from noninvasive coronary computed tomography angiography (cCTA) data. One such technology, FFRCT, or noninvasive fractional flow reserve derived from CT data, has demonstrated high diagnostic accuracy as compared to invasively measured fractional flow reserve (FFR) obtained with a pressure wire inserted in the coronary arteries during diagnostic cardiac catheterization. However, uncertainties in modeling as well as measurement results in differences between these predicted and measured hemodynamic indices. Uncertainty in modeling can manifest in two forms - anatomic uncertainty resulting in error of the reconstructed 3D model and physiologic uncertainty resulting in errors in boundary conditions or blood viscosity. We present a data-driven framework for modeling these uncertainties and study their impact on blood flow simulations. The incompressible Navier-Stokes equations are used to model blood flow and an adaptive stochastic collocation method is used to model uncertainty propagation in the Navier-Stokes equations. We perform uncertainty quantification in two geometries, an idealized stenosis model and a patient specific model. We show that uncertainty in minimum lumen diameter (MLD) has the largest impact on hemodynamic simulations, followed by boundary resistance, viscosity and lesion length. We show that near the diagnostic cutoff (FFRCT=0.8), the uncertainty due to the latter three variables are lower than measurement uncertainty, while the uncertainty due to MLD is only slightly higher than measurement uncertainty. We also show that uncertainties are not additive but only slightly higher than the highest single parameter uncertainty. The method presented here can be used to output interval estimates of hemodynamic indices

  1. Chaotic dynamics of red blood cells in oscillating shear flow

    NASA Astrophysics Data System (ADS)

    Bagchi, Prosenjit; Cordasco, Daniel

    2015-11-01

    A 3D computational study of deformable red blood cells in dilute suspension and subject to sinusoidally oscillating shear flow is considered. It is observed that the cell exhibits either a periodic motion or a chaotic motion. In the periodic motion, the cell reverses its orientation either about the flow direction or about the flow gradient, depending on the initial conditions. In certain parameter range, the initial conditions are forgotten and the cells become entrained in the same sequence of horizontal reversals. The chaotic dynamics is characterized by a nonperiodic sequence of horizontal and vertical reversals, and swings. The study provides the first conclusive evidence of the chaotic dynamics of fully deformable cells in oscillating flow using a deterministic numerical model without the introduction of any stochastic noise. An analysis of the chaotic dynamics shows that chaos is only possible in certain frequency bands when the cell membrane can rotate by a certain amount allowing the cells to swing near the maximum shear rate. We make a novel observation that the occurrence of the vertical or horizontal reversal depends only on whether a critical angle, that is independent of the flow frequency, is exceeded at the instant of flow reversal.

  2. Functional monitoring of blood flow dynamics in brain with photon correlation techniques

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Ashwin B.; Gannon, Kimberly; Baker, Wesley B.; Kavuri, Venki; Mullen, Michael T.; Detre, John A.; Yodh, Arjun G.

    2016-03-01

    We introduce a new software correlator approach for continuous high-speed (up to 100 Hz) monitoring of blood flow dynamics with Diffuse Correlation Spectroscopy. The functionality of the high-speed software correlator is demonstrated with measurements of baseline blood flow dynamics. The utility of high-data-rate blood flow monitoring is demonstrated with measurements of cerebral autoregulation dynamics.

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. Collection of peripheral blood stem cells using an automated discontinuous flow blood cell separator.

    PubMed

    Pierelli, L; Menichella, G; Paoloni, A; Teofili, L; Sica, S; Foddai, M L; Rossi, P L; Leone, G; Mango, G; Bizzi, B

    1990-01-01

    Twenty collections of peripheral blood stem cells were performed in 3 patients (2 NHL, 1 AML) using the Haemonetics V50S discontinuous flow blood cell separator. A modified lymphocyte collection protocol (Nebraska Surge) was used in all instances. Leukapheresis were performed after 1 or 2 courses of chemotherapy and started when peripheral blood leukocytes count reached 1 x 10e9/l and platelets count 80 x 10e9/l. A mean blood volume of 5.9 +/- 0.6 litres was processed per procedure and the mean yields for mononuclear cells, nucleated cells and CFU-GM were respectively 5.4 +/- 1.4 x 10e9, 4.9 +/- 1.6 x 10e9 and 128.5 +/- 182.3 x 10e4 per procedure. Haemonetics V50S had showed a mean collection efficiency for mononuclear cells of 67.5 +/- 5.0% per procedure. Results obtained are not significantly different from the ones obtained with an automated continuous flow separator even if extracorporeal circulation is consistently high in patients with a low hematocrit when the 250 ml Latham Bowl is used.

  9. Tension of red blood cell membrane in simple shear flow

    NASA Astrophysics Data System (ADS)

    Omori, T.; Ishikawa, T.; Barthès-Biesel, D.; Salsac, A.-V.; Imai, Y.; Yamaguchi, T.

    2012-11-01

    When a red blood cell (RBC) is subjected to an external flow, it is deformed by the hydrodynamic forces acting on its membrane. The resulting elastic tensions in the membrane play a key role in mechanotransduction and govern its rupture in the case of hemolysis. In this study, we analyze the motion and deformation of an RBC in a simple shear flow and the resulting elastic tensions on the membrane. The large deformation of the red blood cell is modelled by coupling a finite element method to solve the membrane mechanics and a boundary element method to solve the flows of the internal and external liquids. Depending on the capillary number Ca, ratio of the viscous to elastic forces, we observe three kinds of RBC motion: tumbling at low Ca, swinging at larger Ca, and breathing at the transitions. In the swinging regime, the region of the high principal tensions periodically oscillates, whereas that of the high isotropic tensions is almost unchanged. Due to the strain-hardening property of the membrane, the deformation is limited but the membrane tension increases monotonically with the capillary number. We have quantitatively compared our numerical results with former experimental results. It indicates that a membrane isotropic tension O(10-6 N/m) is high enough for molecular release from RBCs and that the typical maximum membrane principal tension for haemolysis would be O(10-4 N/m). These findings are useful to clarify not only the membrane rupture but also the mechanotransduction of RBCs.

  10. Determination of cerebral cortical blood flow: a thermal technique.

    PubMed

    Hoehner, P J; Krause, G S; White, B C; Gadzinski, D S

    1983-01-01

    A mathematical model for tissue thermodilution was developed to study cerebral cortical perfusion before and after controlled perfusion arrest. Cerebral cortical perfusion rates are readily determined by this method. A thermistor was introduced into the subdural space and secured in direct contact with the frontal cortex in 12 dogs on ketamine and gallamine anesthesia. A 22-gauge angiocath was placed in the right superior thyroid artery and directed into the carotid artery on the same side as the thermistor. The dogs were placed on cardiac bypass using a circuit from the right atrium to the pulmonary artery and a second circuit from the left ventricular apex to the left femoral artery. Arterial pressure, central venous pressure (CVP), intracranial pressure (ICP), and left atrial pressure (LAP) were monitored directly. A heat exchanger was used to maintain a constant blood temperature of 37 C in the output of the left side bypass circuit. Thermal flow curves were generated in the cerebral cortex by injecting 2 to 4 cc of cold saline into the common carotid artery through the injection catheter. Preliminary evaluation of this flow method in comparison to radioactive microspheres indicates that this method can be used in a reliable and reproducible fashion to determine cerebral cortical blood flow.

  11. Form, shape and function: segmented blood flow in the choriocapillaris

    PubMed Central

    Zouache, M. A.; Eames, I.; Klettner, C. A.; Luthert, P. J.

    2016-01-01

    The development of fluid transport systems was a key event in the evolution of animals and plants. While within vertebrates branched geometries predominate, the choriocapillaris, which is the microvascular bed that is responsible for the maintenance of the outer retina, has evolved a planar topology. Here we examine the flow and mass transfer properties associated with this unusual geometry. We show that as a result of the form of the choriocapillaris, the blood flow is decomposed into a tessellation of functional vascular segments of various shapes delineated by separation surfaces across which there is no flow, and in the vicinity of which the transport of passive substances is diffusion-limited. The shape of each functional segment is determined by the distribution of arterioles and venules and their respective relative flow rates. We also show that, remarkably, the mass exchange with the outer retina is a function of the shape of each functional segment. In addition to introducing a novel framework in which the structure and function of the metabolite delivery system to the outer retina may be investigated in health and disease, the present work provides a general characterisation of the flow and transfers in multipole Hele-Shaw configurations. PMID:27779198

  12. 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.

  13. Developmental validation of a novel lateral flow strip test for rapid identification of human blood (Rapid Stain Identification--Blood).

    PubMed

    Schweers, Brett A; Old, Jennifer; Boonlayangoor, P W; Reich, Karl A

    2008-06-01

    Human blood is the body fluid most commonly encountered at crime scenes, and blood detection may aid investigators in reconstructing what occurred during a crime. In addition, blood detection can help determine which items of evidence should be processed for DNA-STR testing. Unfortunately, many common substances can cause red-brown stains that resemble blood. Furthermore, many current human blood detection methods are presumptive and prone to false positive results. Here, the developmental validation of a new blood identification test, Rapid Stain Identification--Blood (RSID--Blood), is described. RSID--Blood utilizes two anti-glycophorin A (red blood cell membrane specific protein) monoclonal antibodies in a lateral flow strip test format to detect human blood. We present evidence demonstrating that this test is accurate, reproducible, easy to use, and highly specific for human blood. Importantly, RSID--Blood does not cross-react with ferret, skunk, or primate blood and exhibits no high-dose hook effect. Also, we describe studies on the sensitivity, body fluid specificity, and species specificity of RSID--Blood. In addition, we show that the test can detect blood from a variety of forensic exhibits prior to processing for DNA-STR analysis. In conclusion, we suggest that RSID--Blood is effective and useful for the detection of human blood on forensic exhibits, and offers improved blood detection when compared to other currently used methods.

  14. Clinical applications of the continuous flow blood separator machine.

    PubMed Central

    Oon, C J; Hobbs, J R

    1975-01-01

    The NCl/IBM or Aminco Continuous Flow Blood Separator Machine is a safe apparatus for the selective removal or exchange of either packed red blood cells, leucocyte-rich or platelet-rich layers or plasma. Abnormal fractions from any of these layers may be collected and discarded. Normal constituents may be collected for therapeutic uses. The wide scope of its applications includes important uses in clinical immunology: temporary provision of good leucocytes or platelets; harvesting of immune leucocytes (preparation of transfer factor at up to 10 units per harvest); removal of cryo- or macro-globulins, immune complexes or blocking factors; replacement therapy for antibody or complement deficiencies. Examples are given of such uses together with some of the medical problems so far encountered. Images FIG. 6 PMID:1106917

  15. 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

  16. Pulsatile flow of Casson's fluid through stenosed arteries with applications to blood flow.

    PubMed

    Chaturani, P; Samy, R P

    1986-01-01

    The effects of non-Newtonian nature of blood and pulsatility on flow through a stenosed tube have been investigated. A perturbation method is used to analyse the flow. It is of interest to note that the thickness of the viscous flow region is non-uniform (changing with axial distance). An analytic relation between viscous flow region thickness and red cell concentration has been obtained. It is important to mention that some researchers have obtained an approximate solution for the flow rate-pressure gradient equation (assuming the ratio between the yield stress and the wall shear to be very small in comparison to unity); in the present analysis, we have obtained an exact solution for this non-linear equation without making that assumption. The approximate and exact solutions compare well with one of the exact solutions. Another important result is that the mean and steady flow rates decrease as the yield stress theta increases. For the low values of the yield stress, the mean flow rate is higher than the steady flow rate, but for high values of the yield stress, the mean flow rate behaviour is of opposite nature. The critical value of the yield stress at which the flow rate behaviour changes from one type to another has been determined. Further, it seems that there exists a value of the yield stress at which flow stops for both the flows (steady and pulsatile). It is observed that the flow stop yield value for pulsatile flow is lower than the steady flow. The most notable result of pulsatility is the phase lag between the pressure gradient and flow rate, which is further influenced by the yield stress and stenosis. Another important result of pulsatility is the mean resistance to flow is greater than its steady flow value, whereas the mean value of the wall shear for pulsatile flow is equal to steady wall shear. Many standard results regarding Casson and Newtonian fluids flow, uniform tube flow and steady flow can be obtained as the special cases of the present

  17. 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).

  18. Skin blood flow with elastic compressive extravehicular activity space suit.

    PubMed

    Tanaka, Kunihiko; Gotoh, Taro M; Morita, Hironobu; Hargens, Alan R

    2003-10-01

    During extravehicular activity (EVA), current space suits are pressurized with 100% oxygen at approximately 222 mmHg. A tight elastic garment, or mechanical counter pressure (MCP) suit that generates pressure by compression, may have several advantages over current space suit technology. In this study, we investigated local microcirculatory effects produced with negative ambient pressure with an MCP sleeve. The MCP glove and sleeve generated pressures similar to the current space suit. MCP remained constant during negative pressure due to unchanged elasticity of the material. Decreased skin capillary blood flow and temperature during MCP compression was counteracted by greater negative pressure or a smaller pressure differential.

  19. A simulated dye method for flow visualization with a computational model for blood flow.

    PubMed

    Kim, T; Cheer, A Y; Dwyer, H A

    2004-08-01

    A numerical dye method for the visualization of unsteady three-dimensional flow calculations is introduced by coupling the unsteady convection-diffusion equation to the Navier-Stokes equation for mass and momentum. This system of equations is descretized using a finite volume projection-like algorithm with generalized coordinates and overset grids. A powerful pressure prediction method is used to accelerate the convergence of the Pressure Poisson equation. To demonstrate the visualization technique, blood flow through the aortic arch region and the three main arterial branches is computed using various Womersley numbers. In this technique, parcels of fluid are followed in time as a function of the cardiac cycle without having to track individual particles, which in turn aids us to better understand some important aspects of the three-dimensionality of the developing unsteady flow. Using this numerical dye method we analyze the strength of the cross flow during the cardiac cycle, the relationship between the penetration of blood into the aortic branches from its relative position in the ascending aortic region and the effects of the Womersley parameter. This technique can be very useful in the design and development of stents where the topology of the device would require understanding where the blood emanating from the heart ends up at the end of the cardiac cycle. Moreover, this method could be useful in investigating the influence of flow and geometry on the local introduction of medication.

  20. 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.

  1. 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.

  2. 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

  3. Numerical Simulation of Unsteady Blood Flow through Capillary Networks.

    PubMed

    Davis, J M; Pozrikidis, C

    2011-08-01

    A numerical method is implemented for computing unsteady blood flow through a branching capillary network. The evolution of the discharge hematocrit along each capillary segment is computed by integrating in time a one-dimensional convection equation using a finite-difference method. The convection velocity is determined by the local and instantaneous effective capillary blood viscosity, while the tube to discharge hematocrit ratio is deduced from available correlations. Boundary conditions for the discharge hematocrit at divergent bifurcations arise from the partitioning law proposed by Klitzman and Johnson involving a dimensionless exponent, q≥1. When q=1, the cells are partitioned in proportion to the flow rate; as q tends to infinity, the cells are channeled into the branch with the highest flow rate. Simulations are performed for a tree-like, perfectly symmetric or randomly perturbed capillary network with m generations. When the tree involves more than a few generations, a supercritical Hopf bifurcation occurs at a critical value of q, yielding spontaneous self-sustained oscillations in the absence of external forcing. A phase diagram in the m-q plane is presented to establish conditions for unsteady flow, and the effect of various geometrical and physical parameters is examined. For a given network tree order, m, oscillations can be induced for a sufficiently high value of q by increasing the apparent intrinsic viscosity, decreasing the ratio of the vessel diameter from one generation to the next, or by decreasing the diameter of the terminal vessels. With other parameters fixed, oscillations are inhibited by increasing m. The results of the continuum model are in excellent agreement with the predictions of a discrete model where the motion of individual cells is followed from inlet to outlet.

  4. Inhibition of coronary blood flow by a vascular waterfall mechanism.

    PubMed

    Downey, J M; Kirk, E S

    1975-06-01

    The mechanism whereby systole inhibits coronary blood flow was examined. A branch of the left coronary artery was maximally dilated with an adenosine infusion, and the pressure-flow relationship was obtained for beating and arrested states. The pressure-flow curve for the arrested state was shifted toward higher pressures and in the range of pressures above peak ventricular pressure was linear and parallel to that for the arrested state. Below this range the curve for the beating state converged toward that for the arrested state and was convex to the pressure axis. These results were compared with a model of the coronary vasculature that consisted of numerous parallel channels, each responding to local intramyocardial pressure by forming vascular waterfalls. When intramyocardial pressure in the model was assigned values from zero at the epicardium to peak ventricular pressure at the endocardium, pressure-flow curves similar to the experimental ones resulted. Thus, we conclude that systole inhibits coronary perfusion by the formation of vascular waterfalls and that the intramyocardial pressures responsible for this inhibition do not significantly exceed peak ventricular pressure.

  5. Human red blood cells deformed under thermal fluid flow.

    PubMed

    Foo, Ji-Jinn; Chan, Vincent; Feng, Zhi-Qin; Liu, Kuo-Kang

    2006-03-01

    The flow-induced mechanical deformation of a human red blood cell (RBC) during thermal transition between room temperature and 42.0 degrees C is interrogated by laser tweezer experiments. Based on the experimental geometry of the deformed RBC, the surface stresses are determined with the aid of computational fluid dynamics simulation. It is found that the RBC is more deformable while heating through 37.0 degrees C to 42.0 degrees C, especially at a higher flow velocity due to a thermal-fluid effect. More importantly, the degree of RBC deformation is irreversible and becomes softer, and finally reaches a plateau (at a uniform flow velocity U > 60 microm s(-1)) after the heat treatment, which is similar to a strain-hardening dominated process. In addition, computational simulated stress is found to be dependent on the progression of thermotropic phase transition. Overall, the current study provides new insights into the highly coupled temperature and hydrodynamic effects on the biomechanical properties of human erythrocyte in a model hydrodynamic flow system.

  6. 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.

  7. 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.

  8. Radioactive oxygen-15 in the study of cerebral blood flow, blood volume, and oxygen metabolism

    SciTech Connect

    Ter-Pogossian, M.M.; Herscovitch, P.

    1985-10-01

    The short half-life of /sup 15/O led early observers to believe that it was unsuitable for use as a biological tracer. However, initial studies with this nuclide demonstrated its potential usefulness for in vivo, regional physiologic measurements. Subsequently, techniques were developed to measure cerebral blood flow (CBF), blood volume, and oxygen metabolism using intracarotid injection of /sup 15/O-labeled radiopharmaceuticals and highly collimated scintillation probes to record the time course of radioactivity in the brain. The development of positron emission tomography (PET) made possible the in vivo, noninvasive measurement of the absolute concentration of positron-emitting nuclides. A variety of tracer kinetic models were formulated to obtain physiologic measurements from tomographic images of the distribution of 15O-labeled radiopharmaceuticals in the brain. Regional cerebral oxygen metabolism is measured using scan data obtained following the inhalation of /sup 15/O-labeled oxygen. The tracer kinetic models used to measure rCBV, blood flow, and oxygen metabolism will be described and their relative advantages and limitations discussed. Several examples of the use of /sup 15/O tracer methods will be reviewed to demonstrate their widespread applicability to the study of cerebral physiology and pathophysiology. 110 references.

  9. Monitoring blood flow and photobleaching during topical ALA PDT treatment

    NASA Astrophysics Data System (ADS)

    Sands, Theresa L.; Sunar, Ulas; Foster, Thomas H.; Oseroff, Allan R.

    2009-02-01

    Photodynamic therapy (PDT) using topical aminolevulinic acid (ALA) is currently used as a clinical treatment for nonmelanoma skin cancers. In order to optimize PDT treatment, vascular shutdown early in treatment must be identified and prevented. This is especially important for topical ALA PDT where vascular shutdown is only temporary and is not a primary method of cell death. Shutdown in vasculature would limit the delivery of oxygen which is necessary for effective PDT treatment. Diffuse correlation spectroscopy (DCS) was used to monitor relative blood flow changes in Balb/C mice undergoing PDT at fluence rates of 10mW/cm2 and 75mW/cm2 for colon-26 tumors implanted intradermally. DCS is a preferable method to monitor the blood flow during PDT of lesions due to its ability to be used noninvasively throughout treatment, returning data from differing depths of tissue. Photobleaching of the photosensitizer was also monitored during treatment as an indirect manner of monitoring singlet oxygen production. In this paper, we show the conditions that cause vascular shutdown in our tumor model and its effects on the photobleaching rate.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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

  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.

  16. Outflow boundary conditions for blood flow in arterial trees.

    PubMed

    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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Skin blood flow dynamics and its role in pressure ulcers

    PubMed Central

    Liao, Fuyuan; Burns, Stephanie; Jan, Yih-Kuen

    2013-01-01

    Pressure ulcers are a significant healthcare problem affecting the quality of life in wheelchair bounded or bed-ridden people and are a major cost to the healthcare system. Various assessment tools such as the Braden scale have been developed to quantify the risk level of pressure ulcers. These tools have provided an initial guideline on preventing pressure ulcers while additional assessments are needed to improve the outcomes of pressure ulcer prevention. Skin blood flow function that determines the ability of the skin in response to ischemic stress has been proposed to be a good indicator for identifying people at risk of pressure ulcers. Wavelet spectral and nonlinear complexity analyses have been performed to investigate the influences of the metabolic, neurogenic and myogenic activities on microvascular regulation in people with various pathological conditions. These findings have contributed to the understanding of the role of ischemia and viability on the development of pressure ulcers. The purpose of the present review is to provide an introduction of the basic concepts and approaches for the analysis of skin blood flow oscillations, and present an overview of the research results obtained so far. We hope this information may contribute to the development of better clinical guidelines for the prevention of pressure ulcers. PMID:23602509

  4. 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.

  5. Measurement of regional pulmonary blood volume in patients with increased pulmonary blood flow or pulmonary arterial hypertension

    SciTech Connect

    Wollmer, P.; Rozcovek, A.; Rhodes, C.G.; Allan, R.M.; Maseri, A.

    1984-01-01

    The effects of chronic increase in pulmonary blood flow and chronic pulmonary hypertension on regional pulmonary blood volume was measured in two groups of patients. One group of patients had intracardiac, left-to-right shunts without appreciable pulmonary hypertension, and the other consisted of patients with Eisenmenger's syndrome or primary pulmonary hypertension, i.e. patients with normal or reduced blood flow and severe pulmonary hypertension. A technique based on positron tomography was used to measure lung density (by transmission scanning) and regional pulmonary blood volume (after inhalation of /sup 11/CO). The distribution of pulmonary blood volume was more uniform in patients with chronic increase in pulmonary blood flow than in normal subjects. There were also indications of an absolute increase in intrapulmonary blood volume by about 15%. In patients with chronic pulmonary arterial hypertension, the distribution of pulmonary blood volume was also abnormally uniform. There was, however, no indication that overall intrapulmonary blood volume was substantially different from normal subjects. The abnormally uniform distribution of pulmonary blood volume can be explained by recruitment and/or dilatation of vascular beds. Intrapulmonary blood volume appears to be increased in patients with intracardiac, left-to-right shunts. With the development of pulmonary hypertension, intrapulmonary blood volume falls, which may be explained by reactive changes in the vasculature and/or obliteration of capillaries.

  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. 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.

  10. 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.

  11. Changes in human colonic mucosal-submucosal blood flow after body surface cooling.

    PubMed Central

    Forrester, D W; Davison, J S; Spence, V A; Walker, W F

    1981-01-01

    Mucosal-submucosal blood flow in the human colostomy was measured by a radioisotopic washout technique. Changes in blood flow were recorded in 10 subjects after peripheral vasoconstriction evoked by surface cooling of the body. Accompanying the vasoconstriction was a rise in mucosal-submucosal blood flow of approximately 40%. An interpretation of the blood flow changes and the associated alterations in mean arterial blood pressure provide evidence for vasomotor and local regulatory control in the colostomy microcirculation. We believe, therefore that the colostomy is a suitable preparation for studying the human colonic microcirculation. PMID:7262624

  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. 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.

  14. Dynamic modes of red blood cells in oscillatory shear flow

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi

    2010-06-01

    The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle θ , and phase angle ϕ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. (i) tank-treading (TT): ϕ rotates while the shape and θ oscillate. (ii) tumbling (TB): θ rotates while the shape and ϕ oscillate. (iii) intermediate motion: both ϕ and θ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation becomes delayed with respect to the shear oscillation. At a high frequency, multiple limit-cycle oscillations coexist. The thermal fluctuations can induce transitions between two orbits at very low shear amplitudes. For a high mean shear rate with small shear oscillation, the shape and θ oscillate in the TT motion but only one attractor exists even at high shear frequencies. The measurement of these oscillatory modes is a promising tool for quantifying the viscoelasticity of RBCs, synthetic capsules, and lipid vesicles.

  15. 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

  16. Theory to predict shear stress on cells in turbulent blood flow.

    PubMed

    Morshed, Khandakar Niaz; Bark, 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Influence of gravity on flow distribution of red blood cells in microcirculation.

    PubMed

    Tateishi, N; Suzuki, Y; Shirai, M; Maeda, N

    2000-07-01

    The influence of the gravity on flow distribution of erythrocytes in microcirculation was examined. We developed a new centrifuge system with a rotation disc. An observation system of blood flow in a micro-flow channel was arranged on the disc. Erythrocyte flow in the micro-flow tube was displaced under the gravity. This study suggests that the gravity affects the transfer of substances from blood vessels to tissues.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Local anesthetics, pulpal blood flow and C. Edmund Kells.

    PubMed

    Gutmann, James L

    2011-01-01

    Historically there was an attempt by many dental practitioners to implicate anesthetic solutions in the death of the dental pulp. However, their implications may or may not have been valid, as damage to the dental pulp may have resulted from excessive and deleterious restorative procedures on teeth that were anesthetized. Unfortunately little was known about the anesthetic solutions at that time, their composition, which included vasoconstrictors, and their potential to alter pulpal blood flow. This paper will explore both the historical perspectives and concerns regarding the impact of anesthetic solutions on the dental pulp through the eyes of Dr. C. Edmund Kells, along with the contemporary perspectives and realities through the eyes of science, sound research data and clinical practice.

  8. Cerebral blood flow imaging in paediatrics: a review.

    PubMed

    Gordon, I

    1996-12-01

    The ability to study regional cerebral blood flow (rCBF) is available in many institutions, especially with the spread of multi-headed gamma cameras. The use of this technique in paediatrics requires special attention to detail in the manner of data acquisition and handling the child. The interpretation of the rCBF study in a child requires knowledge of normal brain maturation. The major clinical use in paediatrics is epilepsy because of the advances in surgery and the frequency of complex partial seizures. Other indications in paediatric neurology include brain death, acute neurological loss including stroke, language disorders, cerebral palsy, hypertension due to renovascular disease, traumatic brain injury and migraine. There are paediatric psychological conditions in which rCBF assessment has been undertaken, including anorexia nervosa, autism, Gilles de la Tourette Syndrome (GTS) and attention deficit disorder-hyperactivity (ADHD). This article attempts to review all aspects of rCBF studies in paediatrics. PMID:9004297

  9. Blood flow in the ears of patients receiving cochlear implants.

    PubMed

    Nakashima, Tsutomu; Hattori, Taku; Sone, Michihiko; Sato, Eisuke; Tominaga, Mitsuo; Sugiura, Makoto

    2004-06-01

    We measured cochlear blood flow (CBF) in 55 patients who received cochlear implants, using a laser-Doppler probe placed over the site of drilling in the cochlear bony wall. The subjects included 29 patients with congenital deafness of unknown cause, 8 with idiopathic progressive sensorineural hearing loss, 4 with postmeningitic deafness, 3 with Waardenburg's syndrome, 3 with congenital cytomegalovirus infection, and 8 whose deafness had other causes. There was a wide range of CBF values in patients with congenital deafness of unknown cause. In the patients with idiopathic progressive sensorineural hearing loss, the CBF was significantly lower in patients more than 40 years old. Intracochlear calcification following meningitis appears to be associated with a reduced CBF.

  10. 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.

  11. Regional spinal cord blood flow during local cooling

    SciTech Connect

    Sakamoto, T.; Monafo, W.W. )

    1990-06-01

    We used the tissue distribution of ({sup 14}C)butanol to quantitate regional blood flow in the spinal cord (RSCBF) of pentobarbital-anesthetized, normothermic rats in which segmental local cooling pentobarbital-anesthetized, normothermic rats in which segmental local cooling of the spinal cord (to 25-28{degrees}C) at vertebral levels C4-C6 (n = 6) or T13-L1 (n = 6) was induced. Thirty minutes later, blood flow measurements were made at seven levels of the spinal cord and in the sciatic nerve trunks and biceps femoris muscles. Sham-cooled rats served as controls (n = 12). In control rats, RSCBF varied between 41.5 +/- 2.4 and 65.1 +/- 3.2 ml.min-1.100 g-1. Local cooling of the C4-C6 cord segment reduced RSCBF by 32%, from 65.1 +/- 3.2 to 44.4 +/- 3.5 ml.min-1.100 g-1 (P less than 0.01). Tissue vascular resistance (R) in the cooled C4-C6 segment was elevated versus control. There were no other changes in RSCBF at the other cord levels or in the cauda equina. Similarly, local cooling of the T13-L1 segment resulted in a 40% fall in RSCBF in that segment, from 57.1 +/- 2.4 to 34.1 +/- 4.3 ml.min-1.100 g-1 (P less than 0.001). R in the cooled T13-L1 segment was elevated versus control. RSCBF was reduced by 30% in the adjacent proximal T12 segment (P less than 0.001) and by 21% in the adjacent distal L2-L3 segment (P less than 0.05). R was increased in both of these adjacent segments. RSCBF was not altered elsewhere in the cord.

  12. Bang-bang model for regulation of local blood flow.

    PubMed

    Golub, Aleksander S; Pittman, Roland N

    2013-08-01

    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

  13. 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

  14. [Effect of dynamic cardiomyoplasty on coronary arterial blood flow].

    PubMed

    Tsukube, T; Okada, M; Mukai, T

    1993-12-01

    We investigated whether or not dynamic cardiomyoplasty adversely affected coronary arterial blood flow (CABF) through compression of the coronary arteries by muscular contraction during systole and incomplete relaxation of the skeletal muscle flap during diastole. Dynamic cardiomyoplasty was performed in 20 mongrel dogs using a left latissimus dorsi muscle flap, paced synchronously with the R wave of the electrocardiogram. A Doppler catheter (3 F in diameter) was placed in the left main trunk of the coronary artery to analyze the instantaneous changes of coronary arterial blood flow velocity by fast Fourier transformation analysis. We compared both systolic and diastolic properties during assisted versus unassisted cardiac cycles by calculating the peak velocity and the time velocity integrate (TVI). A significant enhancement of systolic CABF was recognized by increases in the systolic peak velocity (26.5 +/- 29.2%) and TVI (20.2 +/- 38.6%). The improved systolic CABF was consistent with an increase in systolic aortic pressure (15.5 +/- 4.3%) and stroke volume (42.8 +/- 11.2%). CABF was also enhanced in diastole because a significant increase of diastolic peak velocity (4.4 +/- 9.4%) and TVI (11.0 +/- 16.7%) was observed. Enhancement of diastolic CABF was associated with the augmentation of cardiac function and the reduction of left ventricular end-diastolic pressure. It could be concluded that CABF was increased by the enhancement of cardiac function as a result of dynamic cardiomyoplasty leading to an increase of cardiac output and aortic pressure and a decrease of left ventricular end-diastolic pressure.

  15. Multiscale Modeling of Red Blood Cell Mechanics and Blood Flow in Malaria

    PubMed Central

    Fedosov, Dmitry A.; Lei, Huan; Caswell, Bruce; Suresh, Subra; Karniadakis, George E.

    2011-01-01

    Red blood cells (RBCs) infected by a Plasmodium parasite in malaria may lose their membrane deformability with a relative membrane stiffening more than ten-fold in comparison with healthy RBCs leading to potential capillary occlusions. Moreover, infected RBCs are able to adhere to other healthy and parasitized cells and to the vascular endothelium resulting in a substantial disruption of normal blood circulation. In the present work, we simulate infected RBCs in malaria using a multiscale RBC model based on the dissipative particle dynamics method, coupling scales at the sub-cellular level with scales at the vessel size. Our objective is to conduct a full validation of the RBC model with a diverse set of experimental data, including temperature dependence, and to identify the limitations of this purely mechanistic model. The simulated elastic deformations of parasitized RBCs match those obtained in optical-tweezers experiments for different stages of intra-erythrocytic parasite development. The rheological properties of RBCs in malaria are compared with those obtained by optical magnetic twisting cytometry and by monitoring membrane fluctuations at room, physiological, and febrile temperatures. We also study the dynamics of infected RBCs in Poiseuille flow in comparison with healthy cells and present validated bulk viscosity predictions of malaria-infected blood for a wide range of parasitemia levels (percentage of infected RBCs with respect to the total number of cells in a unit volume). PMID:22144878

  16. Acute effects of firefighting on arterial stiffness and blood flow.

    PubMed

    Fahs, Christopher A; Yan, Huimin; Ranadive, Sushant; Rossow, Lindy M; Agiovlasitis, Stamatis; Echols, George; Smith, Denise; Horn, Gavin P; Rowland, Thomas; Lane, Abbi; Fernhall, Bo

    2011-04-01

    Sudden cardiac events are responsible for 40-50% of line-of-duty firefighter fatalities, yet the exact cause of these events is unknown. Likely, combinations of thermal, physical, and mental factors impair cardiovascular function and trigger such events. Therefore, the purpose of this study was to examine the impact of firefighting activities on vascular function. Sixty-nine young (28 ± 1 years) male firefighters underwent 3 hours of firefighting activities. Carotid, aortic, and brachial blood pressures (BP), heart rate (HR), augmentation index (AIx), wave reflection timing (TR), aortic pulse wave velocity (PWV), forearm blood flow (FBF), and forearm reactive hyperemia (RH) were measured before and after firefighting activities. Paired samples t-tests revealed significant (p < 0.05) increases in aortic diastolic BP, HR, AIx, PWV, RH, and FBF, and significant decreases in brachial and aortic pulse pressure and TR following firefighting activities. In conclusion, these results suggest that 3 hours of firefighting activities increase both arterial stiffness and vasodilation.

  17. 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.

  18. 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.

  19. A comparison of Newtonian and non-Newtonian models for pulsatile blood flow simulations

    NASA Astrophysics Data System (ADS)

    Husain, Iqbal; Labropulu, Fotini; Langdon, Chris; Schwark, Justin

    2013-04-01

    Mathematical modeling of blood flows in the arteries is an important and challenging problem. This study compares several non-Newtonian blood models with the Newtonian model in simulating pulsatile blood flow through two three-dimensional models of an arterial stenosis and an aneurysm. Four non-Newtonian blood models, namely the Power Law, the Casson, the Carreau, and the Generalized Power Law, as well as the Newtonian model of blood viscosity, are used to investigate the flow effects induced by these different blood constitutive equations. The aim of this study is three-fold: firstly, to investigate the variation in wall shear stress in an artery with a stenosis or aneurysm at different flow rates and degrees of severity; secondly, to compare the various blood models and hence quantify the differences between the models and judge their significance; and lastly, to determine whether the use of the Newtonian blood model is appropriate over a wide range of shear rates.

  20. Local blood flow, cerebrovascular autoregulation and CO2 responsiveness in the rabbit hypothalamus

    PubMed Central

    Cranston, W. I.; Rosendorff, C.

    1971-01-01

    1. Local blood flow has been measured in the hypothalamus and other areas of the brain in the conscious rabbit, by measuring the rate of clearance of small volumes (2·5-10 μl.) of a saline solution of the inert tracer 133Xe injected locally. 2. Increasing the arterial PCO2 caused a mean rise in the hypothalamic blood flow of 34%. 3. The hypothalamic blood flow remained relatively constant over a mean arterial blood pressure range of 41-140 mm Hg. 4. Hypothalamic blood flow was relatively unaffected by anaesthesia with intravenous pentobarbitone; by contrast, blood flow in the cerebral cortex was greatly reduced. 5. It is concluded that the technique is a valid and useful one, since CO2 responsiveness and autoregulation is maintained. Different areas of grey matter have different flow rates, and vary in their responsiveness to barbiturate anaesthesia. PMID:5090987

  1. Measurement of blood flow through surgical anastomosis using the radioactive microsphere technique

    SciTech Connect

    Hummel, S.J.; Delgado, G.; Butterfield, A.; Dritschilo, A.; Harbert, J.

    1985-10-01

    Two different radioactive microspheres ( U Ce and UWSc) were used to measure blood flow to an area of the large intestine in dogs before and after a surgical resection was performed with surgical staples. The healing of an anastomosis is theoretically related to the blood flow to the anastomotic site. Blood flow studies were conducted in three dogs using this technique. The average blood flow preoperatively was 0.558 mL/minute per gram and 1.04 mL/minute per gram postoperatively. These results indicate a statistically significant increase in blood flow at the anastomotic site six days after anastomosis when compared with the blood flow to the same area before any surgical procedures.

  2. 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.

  3. 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

  4. 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 two Non-Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has also been investigated to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of pressure, wall shear stress distributions and the streamlines contours. At early systole pressure differences between Newtonian and Non-Newtonian models are observed at pre-stenotic, throat and immediately after throat regions. In the case of wall shear stress, some differences between Newtonian and Non-Newtonian models are observed when the flows are minimum such as at early systole or diastole.

  5. Airway blood flow response to dry air hyperventilation in sheep

    SciTech Connect

    Parsons, G.H.; Baile, E.M.; Pare, P.D.

    1986-03-01

    Airway blood flow (Qaw) may be important in conditioning inspired air. To determine the effect of eucapneic dry air hyperventilation (hv) on Qaw in sheep the authors studied 7 anesthetized open-chest sheep after 25 min. of warm dry air hv. During each period of hv the authors have recorded vascular pressures, cardiac output (CO), and tracheal mucosal and inspired air temperature. Using a modification of the reference flow technique radiolabelled microspheres were injected into the left atrium to make separate measurements after humid air and dry air hv. In 4 animals a snare around the left main pulmonary artery was used following microsphere injection to prevent recirculation (entry into L lung of microspheres from the pulmonary artery). Qaw to the trachea and L lung as measured and Qaw for the R lung was estimated. After the final injection the sheep were killed and bronchi (Br) and lungs removed. Qaw (trachea plus L lung plus R lung) in 4 sheep increased from a mean of 30.8 to 67.0 ml/min. Airway mucosal temp. decreased from 39/sup 0/ to 33/sup 0/C. The authors conclude that dry air hv cools airway mucosa and increases Qaw in sheep.

  6. Redistribution of pulmonary blood flow during hypoxic exercise.

    PubMed

    Kuwahira, I; Moue, Y; Urano, T; Kamiya, U; Iwamoto, T; Ishii, M; Clancy, R L; Gonzalez, N C

    2001-08-01

    Pulmonary blood flow (PBF) distribution was studied at rest and during exercise in rats acclimatized to chronic hypoxia (barometric pressure [PB] 370 Torr for 3 weeks, A rats) and non-acclimatized (NA) littermates. Both A and NA rats exercised in hypoxia (inspired O2 pressure [PIO2] approximately 70 Torr) or in normoxia (PlO2 approximately 145 Torr). PBF distribution was determined using fluorescent-labeled microspheres injected into the right atrium. The lungs were cut into 28 samples to determine relative scatter of specific PBF ([sample fluorescence intensity/sample dry weight)/(total lung fluorescence intensity/total lung dry weight]). Exercise produced redistribution of PBF both in NA and A rats, and this effect was larger in hypoxia than in normoxia, with minimal redistribution occurring during normoxic exercise in NA rats. The pattern of distribution varies considerably among individual animals. As a result of distribution, the previous high flow areas would be overperfused during hypoxic exercise in some rats. The results support the concept that hypoxic pulmonary vasoconstriction is not uniform and suggest that the combination of hypoxia and exercise may lead to overperfusion and capillary leak in some individuals. PMID:11531029

  7. Spatial heterogeneity of local blood flow and metabolite content in dog hearts

    SciTech Connect

    Franzen, D.; Conway, R.S.; Zhang, H.; Sonnenblick, E.H.; Eng, C. )

    1988-02-01

    Spatial variation (heterogeneity) of myocardial blood flow was studied under basal conditions in relation to four biochemical markers: creatine kinase (CK), lactate dehydrogenase (LDH), ATP, and glycogen. A total of 508 individual 0.5-g samples from the left ventricular free wall was studied in 12 dogs. Myocardial blood flow was measured by radioactive microspheres injected via a pigtail catheter into the left ventricle during light sedation; following thoracotomy, a second set of microspheres was injected via a catheter into the left atrium. In 27-54 samples/heart, myocardial blood flow, CK, LDH, protein, ATP, and glycogen were determined, permitting a direct correspondence between local blood flow and metabolic markers in each sample and an assessment of the spatial heterogeneity of flow and metabolite content. The coefficient of variation, which defines the extent of spatial heterogeneity, averaged 20% for closed-chest flow measurement, 19% for open-chest flow measurement, 22% for CK, 17% for LDH, 15% for protein, 8% for ATP, and 18% for glycogen. The correlation between local blood flow and the studied metabolities can only explain a minor portion of the spatial heterogeneity of myocardial blood flow. Although a physiological link between blood flow and metabolite content for small regions of the heart is demonstrated, the true local variability of blood flow may be modulated predominantly by other factors.

  8. 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

  9. Blood viscoelasticity measurement using steady and transient flow controls of blood in a microfluidic analogue of Wheastone-bridge channel.

    PubMed

    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 (QPBS (SS) /QBlood (L) ). 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) = A α  + A β exp [-(t - t 0 )/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

  10. Skin and muscle components of forearm blood flow in directly heated resting man.

    NASA Technical Reports Server (NTRS)

    Detry, J.-M. R.; Brengelmann, G. L.; Rowell, L. B.; Wyss, C.

    1972-01-01

    Changes in forearm muscle blood flow (FMBF) during direct whole-body heating were measured in 17 normal subjects using three different methods. We conclude that FMBF is not increased by direct whole-body heating. Since renal and splanchnic blood flow fall 30% under these conditions, maximal total skin blood flow in 12 previously studied subjects can be estimated from the rise in cardiac output to be 7.6 L/min (3.0-11.1 L/min).

  11. 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

  12. Effect of copper IUD on microcirculation of blood flow in rabbit uterus

    SciTech Connect

    Zhang, M.; Wang, H.F.; Meng, Z.; Huang, H.Y.

    1987-12-01

    A survey of the rabbit's normal microcirculation of blood flow volume in the endometrium and myometrium with or without a copper intrauterine device (IUD) was made. It was found through statistical analyses that the IUD stimulated the endometrium so that microcirculation of blood flow volume in the endometrium increased significantly, but it did not change the microcirculation of blood flow volume in the myometrium and in the opposite uterus.

  13. Extraction of the magnetohydrodynamic blood flow potential from the surface electrocardiogram in magnetic resonance imaging.

    PubMed

    Nijm, Grace M; Swiryn, Steven; Larson, Andrew C; Sahakian, Alan V

    2008-07-01

    The magnetohydrodynamic effect generates voltages related to blood flow, which are superimposed on the electrocardiogram (ECG) used for gating during cardiac magnetic resonance imaging (MRI). A method is presented for extracting the magnetohydrodynamic signal from the ECG. The extracted magnetohydrodynamic blood flow potential may be physiologically meaningful due to its relationship to blood flow. Removal of the magnetohydrodynamic voltages from the ECG can potentially lead to improved gating and diagnostically useful ECGs.

  14. Mimicking the Interfacial Dynamics of Flowing White Blood Cells

    NASA Astrophysics Data System (ADS)

    Santore, Maria

    2015-03-01

    The rolling of particles on surfaces, facilitated by hydrodynamic forces combined with localized surface interactions of the appropriate strengths, spatial arrangements, and ranges, is a technologically useful means of transporting and manipulating particles. One's intuition for the rolling of a marble or a car tire cannot be extrapolated down to microparticle length scales because the microparticle interactions are dominated by electrostatic, van der Waals, and hydrogen bonding interactions rather than a friction that depends on an imposed normal force. Indeed, our microparticle rolling systems are inspired by the rolling of white blood cells on the inner walls of venules as part of the innate immune response: Selectin molecules engage with their counterparts on the opposing surfaces to slow cell motion relative to that for freely flowing cells. In the resulting rolling signature, ligand-receptor binding and crack closing on the front of the cell are balanced with molecular dis-bonding and crack opening at the rear. The contact region is relatively static, allowing other interactions (for instance signaling) to occur for a finite duration. Thus, achieving particle rolling in synthetic systems is important because it facilitates particle-surface interactions in a continuous nonfouling fashion where the contact surface is continually renewed. In developing a synthetic model for this system, we employ polymers to modify flowing particles and /or planar collectors, producing heterogeneous interfaces which can support rolling or produce other motion signatures such as skipping, arrest, or free flow. We identify, in the synthetic system, combinations of variables that produce rolling and demonstrate how the distinction between rolling and arrest is not a simple matter of the adhesion strength between the particles and the collector. Rolling is a cooperative process and the coordination of binding in one location with dis-bonding in another requires appropriate length

  15. Changes in global cerebral blood flow in humans: effect on regional cerebral blood flow during a neural activation task.

    PubMed

    Ramsay, S C; Murphy, K; Shea, S A; Friston, K J; Lammertsma, A A; Clark, J C; Adams, L; Guz, A; Frackowiak, R S

    1993-11-01

    1. The primary objective of this study was to examine in man, how induced changes in global cerebral blood flow (gCBF) affected a regional cerebral blood flow (rCBF) increase resulting from a neural activation task (opening of eyes). A secondary objective was to quantify how such induced changes in gCBF were distributed between representative regions of either predominantly grey matter or white matter. 2. Positron emission tomography with intravenous infusion of H2(15)O, was used to measure gCBF in six normal males. Concomitant measures of rCBF were obtained in three different regions of interest (ROI): a representative area of predominantly grey matter, a representative area of predominantly white matter and an area of visual cortex. 3. Cerebral blood flow was altered by establishing steady-state changes in PCO2 at a near constant ventilation of approximately 30 l min-1. The mean PET,CO2 (+/- S.D.) levels (mmHg) that resulted were: low, 21.8 +/- 1.8; normal, 39.8 +/- 1.0, and high, 54.8 +/- 1.2. The normal and high levels were obtained by adding appropriate amounts of CO2 to the inspirate. The corresponding mean gCBF levels across all six subjects with eyes closed were: low, 24.2 +/- 4.6; normal, 37.2 +/- 3.9 and high, 66.8 +/- 7.6 ml min-1 dl-1. 4. Blood flow in grey matter (insular cortex) and white matter (centrum semiovale) at normal levels of PCO2 averaged 56.8 +/- 10.1 and 20.3 +/- 3.4 ml min dl-1 respectively. As PCO2 rose, the increase in rCBF to grey matter was approximately three times greater than that to white matter. 5. An activation state of eyes open in a brightly lit room was compared to a baseline state of eyes closed in a darkened room at the three levels of PCO2 (and hence at three levels of gCBF). Over the whole gCBF range a significant (P = 0.028) effect of increasing rCBF in the visual cortex ROI was found in response to opening the eyes; the effect of this activation on rCBF was not significantly dependent (P = 0.34) on the PCO2 (and hence g

  16. Time-resolved volumetric MRI blood flow: a Doppler ultrasound perspective

    NASA Astrophysics Data System (ADS)

    van Pelt, Roy; Oliván Bescós, Javier; Nagel, Eike; Vilanova, Anna

    2014-03-01

    Hemodynamic information is increasingly inspected to assess cardiovascular disease. Abnormal blood-flow patterns include high-speed jet flow and regurgitant flow. Such pathological blood-flow patterns are nowadays mostly inspected by means of color Doppler ultrasound imaging. To date, Doppler ultrasound has been the prevailing modality for blood-flow analysis, providing non-invasive and cost-effective blood-flow imaging. Since recent years, magnetic resonance imaging (MRI) is increasingly employed to measure time-resolved blood-flow data. Albeit more expensive, MRI enables volumetric velocity encoding, providing true vector-valued data with less noise. Domain experts in the field of ultrasound and MRI have extensive experience in the interpretation of blood-flow information, although they employ different analysis techniques. We devise a visualization framework that extends on common Doppler ultrasound visualizations, exploiting the added value of MRI velocity data, and aiming for synergy between the domain experts. Our framework enables experts to explore the advantages and disadvantages of the current renditions of their imaging data. Furthermore, it facilitates the transition from conventional Doppler ultrasound images to present-day high-dimensional velocity fields. To this end, we present a virtual probe that enables direct exploration of MRI-acquired blood-flow velocity data using user-friendly interactions. Based on the probe, Doppler ultrasound inspired visualizations convey both in-plane and through-plane blood-flow velocities. In a compound view, these two-dimensional visualizations are linked to state-of-the-art three-dimensional blood-flow visualizations. Additionally, we introduce a novel volume rendering of the blood-flow velocity data that emphasizes anomalous blood-flow patterns. The visualization framework was evaluated by domain experts, and we present their feedback.

  17. Mathematical analysis of non-Newtonian blood flow in stenosis narrow arteries.

    PubMed

    Sriyab, Somchai

    2014-01-01

    The flow of blood in narrow arteries with bell-shaped mild stenosis is investigated that treats blood as non-Newtonian fluid by using the K-L model. When skin friction and resistance of blood flow are normalized with respect to non-Newtonian blood in normal artery, the results present the effect of stenosis length. When skin friction and resistance of blood flow are normalized with respect to Newtonian blood in stenosis artery, the results present the effect of non-Newtonian blood. The effect of stenosis length and effect of non-Newtonian fluid on skin friction are consistent with the Casson model in which the skin friction increases with the increase of either stenosis length or the yield stress but the skin friction decreases with the increase of plasma viscosity coefficient. The effect of stenosis length and effect of non-Newtonian fluid on resistance of blood flow are contradictory. The resistance of blood flow (when normalized by non-Newtonian blood in normal artery) increases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. The resistance of blood flow (when normalized by Newtonian blood in stenosis artery) decreases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. PMID:25587350

  18. Mathematical analysis of non-Newtonian blood flow in stenosis narrow arteries.

    PubMed

    Sriyab, Somchai

    2014-01-01

    The flow of blood in narrow arteries with bell-shaped mild stenosis is investigated that treats blood as non-Newtonian fluid by using the K-L model. When skin friction and resistance of blood flow are normalized with respect to non-Newtonian blood in normal artery, the results present the effect of stenosis length. When skin friction and resistance of blood flow are normalized with respect to Newtonian blood in stenosis artery, the results present the effect of non-Newtonian blood. The effect of stenosis length and effect of non-Newtonian fluid on skin friction are consistent with the Casson model in which the skin friction increases with the increase of either stenosis length or the yield stress but the skin friction decreases with the increase of plasma viscosity coefficient. The effect of stenosis length and effect of non-Newtonian fluid on resistance of blood flow are contradictory. The resistance of blood flow (when normalized by non-Newtonian blood in normal artery) increases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. The resistance of blood flow (when normalized by Newtonian blood in stenosis artery) decreases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length.

  19. Use of impedance plethysmography to continually monitor bone marrow blood flow

    NASA Technical Reports Server (NTRS)

    Montgomery, L. D.; Mcewen, G. N., Jr.; Gerber, R. L.; Cann, C. E.; Morey, E. R.

    1984-01-01

    An impedance-plethysmographic technique is described which can be used to quantify temporal bone-marrow blood-flow changes. Results obtained with the impedance technique compare favorably with the data from simultaneously administered microspheres. Injection of sympathomimetic drugs produced measurable responses: isoproterenol caused a significant increase in bone-marrow blood flow within 1 min, and levarterenol decreased bone-marrow blood flow. Data obtained with impedance plethysmography suggest that the technique is feasible for multiple measurements on the same animal and that the technique can be used to study acute or chronic changes in bone-marrow blood flow following various experimental treatments.

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

    SciTech Connect

    Stewart, R.S.; Devous, M.D. Sr.; Rush, A.J.; Lane, L.; Bonte, F.J.

    1988-04-01

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

  1. Cerebral blood flow velocity in two patients with neonatal cerebral infarction.

    PubMed

    Nishimaki, S; Seki, K; Yokota, S

    2001-04-01

    Cerebral blood flow velocity was measured in the middle cerebral artery of two patients who exhibited unilateral neonatal cerebral infarction during the neonatal period. Doppler studies demonstrated increases in cerebral blood flow velocity but decreases in the resistance index on the affected side of the middle cerebral artery in the neonate who developed hemiplegia with cystic encephalomalacia, although the neonate with normal neurologic outcome exhibited symmetric cerebral blood flow velocity and resistance index. The asymmetry in cerebral blood flow velocity measurements of both middle cerebral arteries may be useful to evaluate the severity of brain damage and predict the neurodevelopmental prognosis of unilateral neonatal cerebral infarction. PMID:11377112

  2. Regional cerebral blood flow in essential hypertension: data evaluation by a mapping system

    SciTech Connect

    Rodriguez, G.; Arvigo, F.; Marenco, S.; Nobili, F.; Romano, P.; Sandini, G.; Rosadini, G.

    1987-01-01

    Regional cerebral blood flow was studied by means of the 133Xe inhalation method in 26 untreated and 10 treated patients with essential hypertension. The untreated subjects were divided into newly and previously diagnosed groups to assess the relation between regional cerebral blood flow and the duration of hypertension. The overall flow reduction was more marked in the frontal and temporal regions in the previously diagnosed group, and this was attributed to pathological changes in the district served by the middle cerebral artery. Regional temporal lobe impairment was also noted in the newly diagnosed and treated subjects. A significant correlation was found between regional cerebral blood flow and mean arterial blood pressure.

  3. Measurement of the Doppler power of flowing blood using ultrasound Doppler devices.

    PubMed

    Huang, Chih-Chung; Chou, Hung-Lung; Chen, Pay-Yu

    2015-02-01

    Measurement of the Doppler power of signals backscattered from flowing blood (henceforth referred to as the Doppler power of flowing blood) and the echogenicity of flowing blood have been used widely to assess the degree of red blood cell (RBC) aggregation for more than 20 y. Many studies have used Doppler flowmeters based on an analogue circuit design to obtain the Doppler shifts in the signals backscattered from flowing blood; however, some recent studies have mentioned that the analogue Doppler flowmeter exhibits a frequency-response problem whereby the backscattered energy is lost at higher Doppler shift frequencies. Therefore, the measured Doppler power of flowing blood and evaluations of RBC aggregation obtained using an analogue Doppler device may be inaccurate. To overcome this problem, the present study implemented a field-programmable gate array-based digital pulsed-wave Doppler flowmeter to measure the Doppler power of flowing blood, in the aim of providing more accurate assessments of RBC aggregation. A clinical duplex ultrasound imaging system that can acquire pulsed-wave Doppler spectrograms is now available, but its usefulness for estimating the ultrasound scattering properties of blood is still in doubt. Therefore, the echogenicity and Doppler power of flowing blood under the same flow conditions were measured using a laboratory pulser-receiver system and a clinical ultrasound system, respectively, for comparisons. The experiments were carried out using porcine blood under steady laminar flow with both RBC suspensions and whole blood. The experimental results indicated that a clinical ultrasound system used to measure the Doppler spectrograms is not suitable for quantifying Doppler power. However, the Doppler power measured using a digital Doppler flowmeter can reveal the relationship between backscattering signals and the properties of blood cells because the effects of frequency response are eliminated. The measurements of the Doppler power and

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  5. Pulmonary blood flow redistribution by increased gravitational force

    NASA Technical Reports Server (NTRS)

    Hlastala, M. P.; Chornuk, M. A.; Self, D. A.; Kallas, H. J.; Burns, J. W.; Bernard, S.; Polissar, N. L.; Glenny, R. W.

    1998-01-01

    This study was undertaken to assess the influence of gravity on the distribution of pulmonary blood flow (PBF) using increased inertial force as a perturbation. PBF was studied in unanesthetized swine exposed to -Gx (dorsal-to-ventral direction, prone position), where G is the magnitude of the force of gravity at the surface of the Earth, on the Armstrong Laboratory Centrifuge at Brooks Air Force Base. PBF was measured using 15-micron fluorescent microspheres, a method with markedly enhanced spatial resolution. Each animal was exposed randomly to -1, -2, and -3 Gx. Pulmonary vascular pressures, cardiac output, heart rate, arterial blood gases, and PBF distribution were measured at each G level. Heterogeneity of PBF distribution as measured by the coefficient of variation of PBF distribution increased from 0.38 +/- 0.05 to 0.55 +/- 0.11 to 0.72 +/- 0.16 at -1, -2, and -3 Gx, respectively. At -1 Gx, PBF was greatest in the ventral and cranial and lowest in the dorsal and caudal regions of the lung. With increased -Gx, this gradient was augmented in both directions. Extrapolation of these values to 0 G predicts a slight dorsal (nondependent) region dominance of PBF and a coefficient of variation of 0.22 in microgravity. Analysis of variance revealed that a fixed component (vascular structure) accounted for 81% and nonstructure components (including gravity) accounted for the remaining 19% of the PBF variance across the entire experiment (all 3 gravitational levels). The results are inconsistent with the predictions of the zone model.

  6. Transient Non-Newtonian Blood Flow under Magnetic Targeting Drug Delivery in an Aneurysm Blood Vessel with Porous Walls

    NASA Astrophysics Data System (ADS)

    Alimohamadi, Haleh; Imani, Mohsen

    2014-11-01

    The present investigation deals with numerical solution of blood flow patterns through an aneurysm artery under the applied magnetic field. Transient extended Navier-Stokes, Brinkman, continuity, and heat conduction equations govern this phenomenon and unsteady pulsatile inlet velocity varies by human heart-beating frequency. Our simulation demonstrates applying 105 magnetic field intensity (MnF) to recirculate flow and increase fluid flux and maximum blood temperature by 62.5x and 3.5%, respectively, in the aneurysm region. It is also shown that the vessel's wall porosity plays an important role in magnetic targeting of drug delivery performance, as this parameter can noticeably change maximum blood temperature and pressure.

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

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J.

    2014-01-01

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

  8. Canine bone blood flow measurements using serial microsphere injections.

    PubMed

    McGrory, B J; Moran, C G; Bronk, J; Weaver, A L; Wood, M B

    1994-06-01

    The objective of this study was to determine the reproducibility of serial bone blood flow (BBF) quantitation using multiple microsphere injections. Three consecutive estimates of BBF were obtained, using 15-mu radionuclide-labeled microspheres from 21 anesthetized adult dogs. A dose of 3 million spheres/kg was used in seven dogs (Cohort 1); a dose of 0.5 million spheres/kg was used in the remaining 14 dogs (Cohorts 2 and 3). Estimates of BBF were made at an average of 129, 153, and 175 minutes after the animals had been anesthetized in the first two cohorts and 179, 203, and 225 minutes in Cohort 3. The dogs in Cohort 1 had no surgical intervention; the dogs in Cohorts 2 and 3 had increasingly complex surgical interventions. Despite stabilization of cardiovascular status, BBF was found to vary by 33.4% in Cohort 1, 25.7% in Cohort 2, and 42.5% in Cohort 3 over the three injections. Cortical BBF fell by 13.9%, 12.1%, and 12.4% between the first and second, and by 31.0%, 11.2%, and 29.9% between the second and third estimates for Cohorts 1, 2, and 3, respectively. Variation in right to left blood flow was used as an overall measure of error caused by technique and did not consistently increase between the first, second, or third BBF estimates in any cohort. Cortical BBF data were found to be significantly more reliable than cancellous data (p < 0.01); error caused by technique was least in the midshaft femoral or midshaft humeral cortical samples. Increasing the dose of spheres administered from 0.5 to 3 million/kg for three serial microsphere injections increased the number of reliable samples and did not lead to increased technical error or shunting. This study demonstrates that there is a significant decrease in BBF over time in the anesthetized dog; therefore, serial estimates of BBF can only be interpreted if the results are normalized or if a control group of animals is included.

  9. Comparison of instruments for investigation of microcirculatory blood flow and red blood cell concentration

    NASA Astrophysics Data System (ADS)

    O'Doherty, Jim; McNamara, Paul; Clancy, Neil T.; Enfield, Joey G.; Leahy, Martin J.

    2009-05-01

    The use of laser Doppler perfusion imaging (LDPI) and laser speckle perfusion imaging (LSPI) is well known in the noninvasive investigation of microcirculatory blood flow. This work compares the two techniques with the recently developed tissue viability (TiVi) imaging system, which is proposed as a useful tool to quantify red blood cell concentration in microcirculation. Three systems are evaluated with common skin tests such as the use of vasodilating and vasoconstricting drugs (methlynicotinate and clobetasol, respectively) and a reactive hyperaemia maneuver (using a sphygmomanometer). The devices investigated are the laser Doppler line scanner (LDLS), the laser speckle perfusion imager (FLPI)-both from Moor Instruments (Axminster, United Kingdom)-and the TiVi imaging system (WheelsBridge AB, Linköping, Sweden). Both imaging and point scanning by the devices are used to quantify the provoked reactions. Perfusion images of vasodilatation and vasoconstriction are acquired with both LDLS and FLPI, while TiVi images are acquired with the TiVi imager. Time acquisitions of an averaged region of interest are acquired for temporal studies such as the reactive hyperaemia. In contrast to the change in perfusion over time with pressure, the TiVi imager shows a different response due its measurement of blood concentration rather than perfusion. The responses can be explained by physiological understanding. Although the three devices sample different compartments of tissue, and output essentially different variables, comparisons can be seen between the three systems. The LDLS system proves to be suited to measurement of perfusion in deeper vessels, while FLPI and TiVi showed sensitivity to more superficial nutritional supply. LDLS and FLPI are insensitive to the action of the vasoconstrictor, while TiVi shows the clear boundaries of the reaction. Assessment of the resolution, penetration depth, and acquisition rate of each instrument show complimentary features that should

  10. Bacopa monnieri increases cerebral blood flow in rat independent of blood pressure.

    PubMed

    Kamkaew, Natakorn; Norman Scholfield, C; Ingkaninan, Kornkanok; Taepavarapruk, Niwat; Chootip, Krongkarn

    2013-01-01

    Bacopa monnieri (L.) Wettst. (Brahmi in India and Thailand) is an ayurvedic dementia treatment, but its effect on cerebral blood flow (CBF) is still unknown. We sought to test its chronic and acute effects on CBF compared with Ginkgo biloba and donepezil. CBF was measured by laser Doppler from rat cerebral cortex after 8 weeks of daily oral dosing of these drugs. Systolic blood pressure was also measured using the tail cuff method or via arterial cannulation. In rats treated with B. monnieri (40 mg/kg), CBF was 25% increased [2927 ± 123 perfusion units, (PU)] compared with shams (2337 ± 217 PU, p < 0.05, nine rats). G. biloba (60 mg/kg) also increased CBF (by 29% to 3019 ± 208 PU, p < 0.05, nine rats). No clear effect was obtained with donepezil (1 mg/kg). Chronic administration of the preparations had no effect on blood pressure. In contrast, intravenous acute infusion of these herbals (20-60 mg/kg) had marked dose-dependent hypotensive actions (diastolic ~31 mmHg lower with 40 mg/kg of either extract), which correspondingly reduced CBF by ~15%. Likewise, CBF fell slightly with acute intravenous sodium nitroprusside and rose with noradrenaline. Donepezil (1 mg/kg) was slightly hypotensive without affecting CBF. Increased CBF with B. monnieri may account for its reported procognitive effect, and its further exploration as an alternative nootropic drug is worthwhile.

  11. Relation of retinal blood flow and retinal oxygen extraction during stimulation with diffuse luminance flicker

    PubMed Central

    Palkovits, Stefan; Lasta, Michael; Told, Reinhard; Schmidl, Doreen; Werkmeister, René; Cherecheanu, Alina Popa; Garhöfer, Gerhard; Schmetterer, Leopold

    2015-01-01

    Cerebral and retinal blood flow are dependent on local neuronal activity. Several studies quantified the increase in cerebral blood flow and oxygen consumption during activity. In the present study we investigated the relation between changes in retinal blood flow and oxygen extraction during stimulation with diffuse luminance flicker and the influence of breathing gas mixtures with different fractions of O2 (FiO2; 100% 15% and 12%). Twenty-four healthy subjects were included. Retinal blood flow was studied by combining measurement of vessel diameters using the Dynamic Vessel Analyser with measurements of blood velocity using laser Doppler velocimetry. Oxygen saturation was measured using spectroscopic reflectometry and oxygen extraction was calculated. Flicker stimulation increased retinal blood flow (57.7 ± 17.8%) and oxygen extraction (34.6 ± 24.1%; p < 0.001 each). During 100% oxygen breathing the response of retinal blood flow and oxygen extraction was increased (p < 0.01 each). By contrast, breathing gas mixtures with 12% and 15% FiO2 did not alter flicker–induced retinal haemodynamic changes. The present study indicates that at a comparable increase in blood flow the increase in oxygen extraction in the retina is larger than in the brain. During systemic hyperoxia the blood flow and oxygen extraction responses to neural stimulation are augmented. The underlying mechanism is unknown. PMID:26672758

  12. Relation of retinal blood flow and retinal oxygen extraction during stimulation with diffuse luminance flicker.

    PubMed

    Palkovits, Stefan; Lasta, Michael; Told, Reinhard; Schmidl, Doreen; Werkmeister, René; Cherecheanu, Alina Popa; Garhöfer, Gerhard; Schmetterer, Leopold

    2015-01-01

    Cerebral and retinal blood flow are dependent on local neuronal activity. Several studies quantified the increase in cerebral blood flow and oxygen consumption during activity. In the present study we investigated the relation between changes in retinal blood flow and oxygen extraction during stimulation with diffuse luminance flicker and the influence of breathing gas mixtures with different fractions of O2 (FiO2; 100% 15% and 12%). Twenty-four healthy subjects were included. Retinal blood flow was studied by combining measurement of vessel diameters using the Dynamic Vessel Analyser with measurements of blood velocity using laser Doppler velocimetry. Oxygen saturation was measured using spectroscopic reflectometry and oxygen extraction was calculated. Flicker stimulation increased retinal blood flow (57.7 ± 17.8%) and oxygen extraction (34.6 ± 24.1%; p < 0.001 each). During 100% oxygen breathing the response of retinal blood flow and oxygen extraction was increased (p < 0.01 each). By contrast, breathing gas mixtures with 12% and 15% FiO2 did not alter flicker-induced retinal haemodynamic changes. The present study indicates that at a comparable increase in blood flow the increase in oxygen extraction in the retina is larger than in the brain. During systemic hyperoxia the blood flow and oxygen extraction responses to neural stimulation are augmented. The underlying mechanism is unknown. PMID:26672758

  13. Differences in blood flow volume and vascular resistance between free flaps: assessment in 58 cases.

    PubMed

    Takanari, Keisuke; Kamei, Yuzuru; Toriyama, Kazuhiro; Yagi, Shunjiro; Torii, Shuhei

    2009-01-01

    In free-flap transfer, blood flow in the transferred flap contributes to wound healing and to resistance against infection in the recipient site. Successful reconstructions using free tissue transfers may be required to define and choose flaps with abundant blood flow in necessary cases. We investigated blood flow in the flap by transit-time ultrasound flowmeter in 58 free-flap transfers. Flow volume was compared between flap tissues as vascular resistance in the flap was calculated. Fasciocutaneous and osteocutaneous flaps had relatively low blood flow volume, myocutaneous flaps had more, and intraperitoneal flaps had still higher blood flow volume. These differences were statistically significant. Vascular resistance significantly decreased in the same order of comparison. Our findings will help in selecting the most suitable flaps for reconstructive surgery. PMID:18942044

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    PubMed

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

    2012-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    PubMed

    Soltani, M; Chen, P

    2013-01-01

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

  18. Middle cerebral artery blood velocity and cerebral blood flow and O2 uptake during dynamic exercise.

    PubMed

    Madsen, P L; Sperling, B K; Warming, T; Schmidt, J F; Secher, N H; Wildschiødtz, G; Holm, S; Lassen, N A

    1993-01-01

    Results obtained by the 133Xe clearance method with external detectors and by transcranial Doppler sonography (TCD) suggest that dynamic exercise causes an increase of global average cerebral blood flow (CBF). These data are contradicted by earlier data obtained during less-well-defined conditions. To investigate this controversy, we applied the Kety-Schmidt technique to measure the global average levels of CBF and cerebral metabolic rate of oxygen (CMRO2) during rest and dynamic exercise. Simultaneously with the determination of CBF and CMRO2, we used TCD to determine mean maximal flow velocity in the middle cerebral artery (MCA Vmean). For values of CBF and MCA Vmean a correction for an observed small drop in arterial PCO2 was carried out. Baseline values for global CBF and CMRO2 were 50.7 and 3.63 ml.100 g-1.min-1, respectively. The same values were found during dynamic exercise, whereas a 22% (P < 0.0001) increase in MCA Vmean was observed. Hence, the exercise-induced increase in MCA Vmean is not a reflection of a proportional increase in CBF.

  19. 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.

  20. Functional laser speckle imaging of cerebral blood flow under hypothermia

    NASA Astrophysics Data System (ADS)

    Li, Minheng; Miao, Peng; Zhu, Yisheng; Tong, Shanbao

    2011-08-01

    Hypothermia can unintentionally occur in daily life, e.g., in cardiovascular surgery or applied as therapeutics in the neurosciences critical care unit. So far, the temperature-induced spatiotemporal responses of the neural function have not been fully understood. In this study, we investigated the functional change in cerebral blood flow (CBF), accompanied with neuronal activation, by laser speckle imaging (LSI) during hypothermia. Laser speckle images from Sprague-Dawley rats (n = 8, male) were acquired under normothermia (37°C) and moderate hypothermia (32°C). For each animal, 10 trials of electrical hindpaw stimulation were delivered under both temperatures. Using registered laser speckle contrast analysis and temporal clustering analysis (TCA), we found a delayed response peak and a prolonged response window under hypothermia. Hypothermia also decreased the activation area and the amplitude of the peak CBF. The combination of LSI and TCA is a high-resolution functional imaging method to investigate the spatiotemporal neurovascular coupling in both normal and pathological brain functions.

  1. Altered Regional Cerebral Blood Flow in Chronic Whiplash Associated Disorders.

    PubMed

    Vállez García, David; Doorduin, Janine; Willemsen, Antoon T M; Dierckx, Rudi A J O; Otte, Andreas

    2016-08-01

    There is increasing evidence of central hyperexcitability in chronic whiplash-associated disorders (cWAD). However, little is known about how an apparently simple cervical spine injury can induce changes in cerebral processes. The present study was designed (1) to validate previous results showing alterations of regional cerebral blood flow (rCBF) in cWAD, (2) to test if central hyperexcitability reflects changes in rCBF upon non-painful stimulation of the neck, and (3) to verify our hypothesis that the missing link in understanding the underlying pathophysiology could be the close interaction between the neck and midbrain structures. For this purpose, alterations of rCBF were explored in a case-control study using H2(15)O positron emission tomography, where each group was exposed to four different conditions, including rest and different levels of non-painful electrical stimulation of the neck. rCBF was found to be elevated in patients with cWAD in the posterior cingulate and precuneus, and decreased in the superior temporal, parahippocampal, and inferior frontal gyri, the thalamus and the insular cortex when compared with rCBF in healthy controls. No differences in rCBF were observed between different levels of electrical stimulation. The alterations in regions directly involved with pain perception and interoceptive processing indicate that cWAD symptoms might be the consequence of a mismatch during the integration of information in brain regions involved in pain processing. PMID:27444853

  2. Measurement and modeling of coronary blood flow.

    PubMed

    Sinclair, Matthew D; Lee, Jack; Cookson, Andrew N; Rivolo, Simone; Hyde, Eoin R; Smith, Nicolas P

    2015-01-01

    Ischemic heart disease that comprises both coronary artery disease and microvascular disease is the single greatest cause of death globally. In this context, enhancing our understanding of the interaction of coronary structure and function is not only fundamental for advancing basic physiology but also crucial for identifying new targets for treating these diseases. A central challenge for understanding coronary blood flow is that coronary structure and function exhibit different behaviors across a range of spatial and temporal scales. While experimental studies have sought to understand this feature by isolating specific mechanisms, in tandem, computational modeling is increasingly also providing a unique framework to integrate mechanistic behaviors across different scales. In addition, clinical methods for assessing coronary disease severity are continuously being informed and updated by findings in basic physiology. Coupling these technologies, computational modeling of the coronary circulation is emerging as a bridge between the experimental and clinical domains, providing a framework to integrate imaging and measurements from multiple sources with mathematical descriptions of governing physical laws. State-of-the-art computational modeling is being used to combine mechanistic models with data to provide new insight into coronary physiology, optimization of medical technologies, and new applications to guide clinical practice. PMID:26123867

  3. Latency relationships between cerebral blood flow velocity and intracranial pressure.

    PubMed

    Asgari, Shadnaz; Vespa, Paul M; Bergsneider, Marvin; Hu, Xiao

    2012-01-01

    Pulsatile intracranial pressure (ICP) is a key to the understanding of several neurological disorders in which compliance is altered, e.g., hydrocephalus. A recently proposed model suggests that ICP pulse is a standing wave and not a transmitted wave. The present work, aimed at obtaining a better understanding of the pulsatility in the cranium, tries to test the following hypotheses: first, ICP pulse onset latency would be lower than that of cerebral blood flow velocity (CBFV) pulses measured at a distal vessel; second, CBFV pulse at different intracranial arteries will have different pulse onset latencies, and hence they are not generated as a standing wave. The dataset used in the present study consists of ICP and CBFV signals collected from 60 patients with different diagnoses. The results reveal that the ICP pulse leads CBFV for 90% of the patients regardless of the diagnosis and mean ICP value. In addition, we show that CBFV pulse onset latency is roughly determined by the distance of the measurement point to the heart. We conclude that the ICP signal is not generated as a standing wave and that ICP pulse onset may be related to the arteries proximal to the heart.

  4. Effects of temperature on blood flow in facial tissues

    SciTech Connect

    Kwon, H.J.; Rhee, J.G.; Song, C.W.; Waite, D.E.

    1986-10-01

    This study evaluated the effect of temperature on blood flow by using rubidium 86 to determine the fraction of cardiac output going to specific facial tissues of rats. Seventy-seven male Holtzman rats were divided into two groups and various subgroups. The intraoral subgroups were categorized according to the temperature of the water irrigating the oral cavity (11, 39, 41, 43, or 45/sup 0/C). The extraoral subgroups were categorized according to whether heat or ice was applied to the cheek of the rats and the duration of application (10 or 20 minutes). Rats were killed within 60 seconds after injection of 86Rb, and tissue samples were taken from the buccal mucosa, facial skin, masseter muscle, mandible, tongue, and maxilla. The fraction of isotope uptake in each gram of these tissues (FU/g) was then calculated. For the intraoral group, the bath temperature of 39/sup 0/C increased the FU/g in all tissues except masseter muscle and tongue. Higher bath temperature did not further alter the FU/g. Lowering the temperature to 11 degrees C changed the FU/g significantly only in the tongue. For the extraoral group, 20-minute application of ice was required to reduce FU/g significantly in all tissues but masseter muscle and skin. Extraoral heat application for 10 minutes increased FU/g significantly in skin and tongue, but no further change was seen after 20 minutes of application.

  5. Numerical method of characteristics for one-dimensional blood flow

    NASA Astrophysics Data System (ADS)

    Acosta, Sebastian; Puelz, Charles; Rivière, Béatrice; Penny, Daniel J.; Rusin, Craig G.

    2015-08-01

    Mathematical modeling at the level of the full cardiovascular system requires the numerical approximation of solutions to a one-dimensional nonlinear hyperbolic system describing flow in a single vessel. This model is often simulated by computationally intensive methods like finite elements and discontinuous Galerkin, while some recent applications require more efficient approaches (e.g. for real-time clinical decision support, phenomena occurring over multiple cardiac cycles, iterative solutions to optimization/inverse problems, and uncertainty quantification). Further, the high speed of pressure waves in blood vessels greatly restricts the time step needed for stability in explicit schemes. We address both cost and stability by presenting an efficient and unconditionally stable method for approximating solutions to diagonal nonlinear hyperbolic systems. Theoretical analysis of the algorithm is given along with a comparison of our method to a discontinuous Galerkin implementation. Lastly, we demonstrate the utility of the proposed method by implementing it on small and large arterial networks of vessels whose elastic and geometrical parameters are physiologically relevant.

  6. Regional cerebral blood flow alterations in obstructive sleep apnea.

    PubMed

    Yadav, Santosh K; Kumar, Rajesh; Macey, Paul M; Richardson, Heidi L; Wang, Danny J J; Woo, Mary A; Harper, Ronald M

    2013-10-25

    Obstructive sleep apnea (OSA) is a condition characterized by upper airway muscle atonia with continued diaphragmatic efforts, resulting in repeated airway obstructions, periods of intermittent hypoxia, large thoracic pressure changes, and substantial shifts in arterial pressure with breathing cessation and resumption. The hypoxic exposure and hemodynamic changes likely induce the structural and functional deficits found in multiple brain areas, as shown by magnetic resonance imaging (MRI) procedures. Altered cerebral blood flow (CBF) may contribute to these localized deficits; thus, we examined regional CBF, using arterial spin labeling procedures, in 11 OSA (age, 49.1±12.2 years; 7 male) and 16 control subjects (42.3±10.2 years; 6 male) with a 3.0-Tesla MRI scanner. CBF maps were calculated, normalized to a common space, and regional CBF values across the brain quantified. Lowered CBF values emerged near multiple bilateral brain sites in OSA, including the corticospinal tracts, superior cerebellar peduncles, and pontocerebellar fibers. Lateralized, decreased CBF appeared near the left inferior cerebellar peduncles, left tapetum, left dorsal fornix/stria terminalis, right medial lemniscus, right red nucleus, right midbrain, and midline pons. Regional CBF values in OSA are significantly reduced in major sensory and motor fiber systems and motor regulatory sites, especially in structures mediating motor coordination; those reductions are often lateralized. The asymmetric CBF declines in motor regulatory areas may contribute to loss of coordination between upper airway and diaphragmatic musculature, and lead to further damage in the syndrome.

  7. Cerebral blood flow in sickle cell cerebrovascular disease

    SciTech Connect

    Huttenlocher, P.R.; Moohr, J.W.; Johns, L.; Brown, F.D.

    1984-05-01

    Cerebral blood flow (CBF) has been studied by the xenon-133 (/sup 133/Xe) inhalation method in 16 children with suspected sickle cell cerebrovascular disease. Abnormalities consisting of decreases in total, hemispheral, or regional CBF were found in 17 of 26 studies. Eleven studies performed immediately after stroke, transient ischemic attack, or depression of state of alertness showed abnormalities. In addition to confirming regional cerebrovascular insufficiency in children with stroke due to major cerebral artery occlusion, the method detected diffuse decrease in CBF in children with stupor, coma, and seizures who had normal angiographic findings. In contrast, six of seven studies obtained after exchange transfusion or during maintenance on hypertransfusion therapy showed normal findings. The difference between results in patients with acute neurologic disturbances and those receiving transfusion therapy was statistically significant (P less than .005). The data indicate that the /sup 133/Xe method reliably demonstrates cerebrovascular impairment in sickle cell disease. They also suggest that CBF changes in patients with sickle cell disease can be reversed by exchange transfusion and by hypertransfusion therapy. The /sup 133/Xe CBF method may be useful for following up children with sickle cell disease who are at high risk for recurrent stroke.

  8. Unveiling astrocytic control of cerebral blood flow with optogenetics.

    PubMed

    Masamoto, Kazuto; Unekawa, Miyuki; Watanabe, Tatsushi; Toriumi, Haruki; Takuwa, Hiroyuki; Kawaguchi, Hiroshi; Kanno, Iwao; Matsui, Ko; Tanaka, Kenji F; Tomita, Yutaka; Suzuki, Norihiro

    2015-06-16

    Cortical neural activities lead to changes in the cerebral blood flow (CBF), which involves astrocytic control of cerebrovascular tone. However, the manner in which astrocytic activity specifically leads to vasodilation or vasoconstriction is difficult to determine. Here, cortical astrocytes genetically expressing a light-sensitive cation channel, channelrhodopsin-2 (ChR2), were transcranially activated with a blue laser while the spatiotemporal changes in CBF were noninvasively monitored with laser speckle flowgraphy in the anesthetised mouse cortex. A brief photostimulation induced a fast transient increase in CBF. The average response onset time was 0.7 ± 0.7 sec at the activation foci, and this CBF increase spread widely from the irradiation spot with an apparent propagation speed of 0.8-1.1 mm/sec. The broad increase in the CBF could be due to a propagation of diffusible vasoactive signals derived from the stimulated astrocytes. Pharmacological manipulation showed that topical administration of a K(+) channel inhibitor (BaCl2; 0.1-0.5 mM) significantly reduced the photostimulation-induced CBF responses, which indicates that the ChR2-evoked astrocytic activity involves K(+) signalling to the vascular smooth muscle cells. These findings demonstrate a unique model for exploring the role of the astrocytes in gliovascular coupling using non-invasive, time-controlled, cell-type specific perturbations.

  9. Hemodynamic and organ blood flow responses to halothane and sevoflurane anesthesia during spontaneous ventilation.

    PubMed

    Crawford, M W; Lerman, J; Saldivia, V; Carmichael, F J

    1992-12-01

    This study compared systemic hemodynamic and organ blood flow responses to equipotent concentrations of halothane and sevoflurane during spontaneous ventilation in the rat. The MAC values for halothane and sevoflurane were determined. Cardiac output and organ blood flows were measured using radiolabeled microspheres. Measurements were obtained in awake rats (control values) and at 1.0 MAC halothane or sevoflurane. The MAC values (mean +/- SEM) for halothane and sevoflurane were 1.10% +/- 0.05% and 2.40% +/- 0.05%, respectively. The PaCO2 increased to a similar extent in both groups compared with control values. During halothane anesthesia, heart rate decreased by 12% (P < 0.01), cardiac index by 26% (P < 0.01), and mean arterial blood pressure by 18% (P < 0.01) compared with control values. Stroke volume index and systemic vascular resistance did not change. During sevoflurane anesthesia, hemodynamic variables remained unchanged compared with control values. Coronary blood flow decreased by 21% (P < 0.01) and renal blood flow by 18% (P < 0.01) at 1.0 MAC halothane, whereas both remained unchanged at 1.0 MAC sevoflurane. Cerebral blood flow increased to a greater extent with halothane (63%; P < 0.01) than with sevoflurane (35%; P < 0.05). During halothane anesthesia, hepatic arterial blood flow increased by 48% (P < 0.01), whereas portal tributary blood flow decreased by 28% (P < 0.01). During sevoflurane anesthesia, hepatic arterial blood flow increased by 70% (P < 0.01) without a concomitant reduction in portal tributary blood flow. Total liver blood flow decreased only with halothane (16%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

  10. Carotid chemoreceptor modulation of blood flow during exercise in healthy humans.

    PubMed

    Stickland, Michael K; Fuhr, Desi P; Haykowsky, Mark J; Jones, Kelvin E; Paterson, D Ian; Ezekowitz, Justin A; McMurtry, M Sean

    2011-12-15

    Carotid chemoreceptor (CC) inhibition reduces sympathetic nervous outflow in exercising dogs and humans. We sought to determine if CC suppression increases muscle blood flow in humans during exercise and hypoxia. Healthy subjects (N = 13) were evaluated at rest and during constant-work leg extension exercise while exposed to either normoxia or hypoxia (inspired O(2) tension, F(IO(2)), ≈ 0.12, target arterial O(2) saturation = 85%). Subjects breathed hyperoxic gas (F(IO(2)) ≈ 1.0) and/or received intravenous dopamine to inhibit the CC while femoral arterial blood flow data were obtained continuously with pulsed Doppler ultrasound. Exercise increased heart rate, mean arterial pressure, femoral blood flow and conductance compared to rest. Transient hyperoxia had no significant effect on blood flow at rest, but increased femoral blood flow and conductance transiently during exercise without changing blood pressure. Similarly, dopamine had no effect on steady-state blood flow at rest, but increased femoral blood flow and conductance during exercise. The transient vasodilatory response observed by CC inhibition with hyperoxia during exercise could be blocked with simultaneous CC inhibition with dopamine. Despite evidence of dopamine reducing ventilation during hypoxia, no effect on femoral blood flow, conductance or mean arterial pressure was observed either at rest or during exercise with CC inhibition with dopamine while breathing hypoxia. These findings indicate that the carotid chemoreceptor contributes to skeletal muscle blood flow regulation during normoxic exercise in healthy humans, but that the influence of the CC on blood flow regulation in hypoxia is limited.

  11. Carotid chemoreceptor modulation of blood flow during exercise in healthy humans.

    PubMed

    Stickland, Michael K; Fuhr, Desi P; Haykowsky, Mark J; Jones, Kelvin E; Paterson, D Ian; Ezekowitz, Justin A; McMurtry, M Sean

    2011-12-15

    Carotid chemoreceptor (CC) inhibition reduces sympathetic nervous outflow in exercising dogs and humans. We sought to determine if CC suppression increases muscle blood flow in humans during exercise and hypoxia. Healthy subjects (N = 13) were evaluated at rest and during constant-work leg extension exercise while exposed to either normoxia or hypoxia (inspired O(2) tension, F(IO(2)), ≈ 0.12, target arterial O(2) saturation = 85%). Subjects breathed hyperoxic gas (F(IO(2)) ≈ 1.0) and/or received intravenous dopamine to inhibit the CC while femoral arterial blood flow data were obtained continuously with pulsed Doppler ultrasound. Exercise increased heart rate, mean arterial pressure, femoral blood flow and conductance compared to rest. Transient hyperoxia had no significant effect on blood flow at rest, but increased femoral blood flow and conductance transiently during exercise without changing blood pressure. Similarly, dopamine had no effect on steady-state blood flow at rest, but increased femoral blood flow and conductance during exercise. The transient vasodilatory response observed by CC inhibition with hyperoxia during exercise could be blocked with simultaneous CC inhibition with dopamine. Despite evidence of dopamine reducing ventilation during hypoxia, no effect on femoral blood flow, conductance or mean arterial pressure was observed either at rest or during exercise with CC inhibition with dopamine while breathing hypoxia. These findings indicate that the carotid chemoreceptor contributes to skeletal muscle blood flow regulation during normoxic exercise in healthy humans, but that the influence of the CC on blood flow regulation in hypoxia is limited. PMID:22025661

  12. Measurement of temperature decrease caused by blood flow in focused ultrasound irradiation by thermal imaging method

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Takenobu; Hatano, Yuichi; Mori, Yashunori; Shen, Rakushin; Endoh, Nobuyuki

    2016-07-01

    In this study, to estimate the local temperature changes caused by a thick blood vessel, the temperature distribution in a tissue phantom with a thick blood vessel during focused ultrasound irradiation was measured by a thermal imaging method. The blood flow rate in the simulated blood vessel was varied and the relationship between flow rate and temperature decrease was examined. The phantom using the thermal imaging method is divided into two parts, and the increases in temperature distribution as a function of blood flow rate are measured using a thermocamera under constant ultrasound irradiation. The irradiation conditions of ultrasound waves were a central frequency of 1 MHz, a wave number length of 200 cycles, and a duty ratio of 0.2. The irradiation duration was 5 min, and the ultrasound intensity I SPTA was 36 W/cm2. The amount of temperature decrease caused by the cooling effect of blood flow increased with the blood flow rate and it became constant at a certain threshold of blood flow rate. The threshold of blood flow rate is about 250 ml/min.

  13. Blood flow dynamics and sensitivity in breasts after reconstruction with DIEP-flap.

    PubMed

    Klasson, Stina; Svensson, Karin; Wollmer, Per; Velander, Patrik; Svensson, Henry

    2014-12-01

    A method of breast reconstruction is based on the Deep Inferior Epigastric Perforator (DIEP) technique. Skin and fat are transplanted from the abdomen to the chest; blood vessels are reconnected through microsurgery. Nerves are, however, left unconnected. This study aims to evaluate the blood flow and reinnervation of blood vessels and skin in breasts reconstructed by DIEP flaps without neural repair. In all, DIEP flaps of 10 patients were tested at an average of 16.3 months postoperatively. Blood flow was assessed by PeriScan PIM II System, both before and after indirect heating. Tactile perception threshold was assessed by Semmes-Weinstein monofilament and thermal sensibility by SENSELab MSA Thermotest. The patients' contralateral breasts were used as controls. The blood flow of the flaps was statistically significantly lower than in the control breasts, both before and after indirect heating. The change in blood flow after indirect heating did, however, not significantly differ when comparing the breasts. All flaps regained deep pressure sensibility in all four quadrants. Five patients regained even better sensibility in one of their quadrants. Seven patients regained perception of cold stimuli, five perceived warmth. This study has shown that skin blood flow regulation is present in DIEP flaps 1 year after reconstruction. Blood flow dynamics are very similar to those in the normal breast. There is also a recovery of tactile and thermal sensibility, but this study has not shown any clear parallels between recovery blood flow, tactile sensibility and thermal sensibility.

  14. Blood flow dynamics and sensitivity in breasts after reconstruction with DIEP-flap.

    PubMed

    Klasson, Stina; Svensson, Karin; Wollmer, Per; Velander, Patrik; Svensson, Henry

    2014-12-01

    A method of breast reconstruction is based on the Deep Inferior Epigastric Perforator (DIEP) technique. Skin and fat are transplanted from the abdomen to the chest; blood vessels are reconnected through microsurgery. Nerves are, however, left unconnected. This study aims to evaluate the blood flow and reinnervation of blood vessels and skin in breasts reconstructed by DIEP flaps without neural repair. In all, DIEP flaps of 10 patients were tested at an average of 16.3 months postoperatively. Blood flow was assessed by PeriScan PIM II System, both before and after indirect heating. Tactile perception threshold was assessed by Semmes-Weinstein monofilament and thermal sensibility by SENSELab MSA Thermotest. The patients' contralateral breasts were used as controls. The blood flow of the flaps was statistically significantly lower than in the control breasts, both before and after indirect heating. The change in blood flow after indirect heating did, however, not significantly differ when comparing the breasts. All flaps regained deep pressure sensibility in all four quadrants. Five patients regained even better sensibility in one of their quadrants. Seven patients regained perception of cold stimuli, five perceived warmth. This study has shown that skin blood flow regulation is present in DIEP flaps 1 year after reconstruction. Blood flow dynamics are very similar to those in the normal breast. There is also a recovery of tactile and thermal sensibility, but this study has not shown any clear parallels between recovery blood flow, tactile sensibility and thermal sensibility. PMID:24693867

  15. Upper extremity blood flow in collegiate and high school baseball pitchers A preliminary report.

    PubMed

    Bast, S C; Perry, J R; Poppiti, R; Vangsness, C T; Weaver, F A

    1996-01-01

    The arterial and venous volume blood flow in the dominant and nondominant upper extremities of five male pitchers, ages 16 to 21, was measured using color flow duplex ultrasound. Blood-flow measurements were obtained at baseline, after warm-up, and after each sequence of 20 pitches until 100 pitches were thrown. Blood flow was additionally determined 1 hour after the last pitch. The velocity of each pitch was recorded with a speed gun. Anthropomorphic measurements of the upper extremity were obtained at baseline and immediately after Pitch 100 using a standard measuring tape. The highest average arterial volume flow in the pitching arm occurred after 40 pitches, reaching a peak of 549 ml/min (56% increase from baseline). Thereafter, the average arterial blood flow steadily declined, reaching an average of 402 ml/min after the 100th pitch (14% increase from baseline). In contrast, the arterial blood flow in the nonpitching arm increased only slightly from baseline, reaching a maximal volume flow of 448 ml/min immediately after the warm-up period (10% increase from baseline). The volume flow then persistently fell to a level 30% below baseline after the 100th pitch. Although this small pilot study does not demonstrate causation between a decline in pitching performance and arterial blood flow, it suggests arterial flow in the dominant extremity falls as the pitch count increases.

  16. Effect of intracapsular hyperpressure on femoral head blood flow. Laser Doppler flowmetry in dogs.

    PubMed

    Vegter, J; Klopper, P J

    1991-08-01

    Intracapsular hyperpressure in the hip joint of dogs affected femoral head blood flow, especially in the juvenile animals. Graphic recording of the laser Doppler signal curve using rapid sampling time demonstrated venous hip joint tamponade in both juvenile and adult dogs. Laser Doppler flowmetry seems to be a sensitive and reproducible method to demonstrate femoral-head blood-flow changes.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  18. Does topical minoxidil increase skin blood flow? A laser Doppler flowmetry study.

    PubMed

    de Boer, E M; Bezemer, P D; Bruynzeel, D P; Nieboer, C

    1988-01-01

    Cutaneous blood flow was measured by Laser Doppler Flowmetry after topical application of minoxidil lotion, in 9 healthy males with androgenetic alopecia, and other volunteers. No reaction in the cutaneous blood flow was seen after application of 2%, 5%, or placebo minoxidil lotion.

  19. Cortical blood flow in controlled hypotension as measured by thermal diffusion 1

    PubMed Central

    Carter, L. Philip; Atkinson, James R.

    1973-01-01

    A thermal diffusion flow probe which gave a continuous, dynamic, quantitative record of cortical blood flow (CBF) was used to assess CBF in experimental animals with controlled hypotension. Acute hypotension was produced by trimethaphan camsylate, halothane, and sodium nitroprusside. Halothane produced less reduction in CBF per drop in blood pressure than the other two agents. Images PMID:4772724

  20. Adrenergically stimulated blood flow in brown adipose tissue is not dependent on thermogenesis.

    PubMed

    Abreu-Vieira, Gustavo; Hagberg, Carolina E; Spalding, Kirsty L; Cannon, Barbara; Nedergaard, Jan

    2015-05-01

    Brown adipose tissue (BAT) thermogenesis relies on blood flow to be supplied with nutrients and oxygen and for the distribution of the generated heat to the rest of the body. Therefore, it is fundamental to understand the mechanisms by which blood flow is regulated and its relation to thermogenesis. Here, we present high-resolution laser-Doppler imaging (HR-LDR) as a novel method for noninvasive in vivo measurement of BAT blood flow in mice. Using HR-LDR, we found that norepinephrine stimulation increases BAT blood flow in a dose-dependent manner and that this response is profoundly modulated by environmental temperature acclimation. Surprisingly, we found that mice lacking uncoupling protein 1 (UCP1) have fully preserved BAT blood flow response to norepinephrine despite failing to perform thermogenesis. BAT blood flow was not directly correlated to systemic glycemia, but glucose injections could transiently increase tissue perfusion. Inguinal white adipose tissue, also known as a brite/beige adipose tissue, was also sensitive to cold acclimation and similarly increased blood flow in response to norepinephrine. In conclusion, using a novel noninvasive method to detect BAT perfusion, we demonstrate that adrenergically stimulated BAT blood flow is qualitatively and quantitatively fully independent of thermogenesis, and therefore, it is not a reliable parameter for the estimation of BAT activation and heat generation.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  2. Augmenting collateral blood flow during ischemic stroke via transient aortic occlusion

    PubMed Central

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

    2014-01-01

    Collateral circulation provides an alternative route for blood flow to reach ischemic tissue during a stroke. Blood flow through the cerebral collaterals is a critical predictor of clinical prognosis after stroke and response to recanalization, but data on collateral dynamics and collateral therapeutics are lacking. Here, we investigate the efficacy of a novel approach to collateral blood flow augmentation to increase collateral circulation by optically recording blood flow in leptomeningeal collaterals in a clinically relevant model of ischemic stroke. Using high-resolution laser speckle contrast imaging (LSCI) during thromboembolic middle cerebral artery occlusion (MCAo), we demonstrate that transiently diverting blood flow from peripheral circulation towards the brain via intra-aortic catheter and balloon induces persistent increases in blood flow through anastomoses between the anterior and middle cerebral arteries. Increased collateral flow restores blood flow in the distal middle cerebral artery segments to baseline levels during aortic occlusion and persists for over 1 hour after removal of the aortic balloon. Given the importance of collateral circulation in predicting stroke outcome and response to treatment, and the potential of collateral flow augmentation as an adjuvant or stand-alone therapy for acute ischemic stroke, this data provide support for further development and translation of collateral therapeutics including transient aortic occlusion. PMID:24045399

  3. Measurement of Retinal Blood Flow Rate in Diabetic Rats: Disparity Between Techniques Due to Redistribution of Flow

    PubMed Central

    Leskova, Wendy; Watts, Megan N.; Carter, Patsy R.; Eshaq, Randa S.; Harris, Norman R.

    2013-01-01

    Purpose. Reports of altered retinal blood flow in experimental models of type I diabetes have provided contrasting results, which leads to some confusion as to whether flow is increased or decreased. The purpose of our study was to evaluate early diabetes-induced changes in retinal blood flow in diabetic rats, using two distinctly different methods. Methods. Diabetes was induced by injection of streptozotocin (STZ), and retinal blood flow rate was measured under anesthesia by a microsphere infusion technique, or by an index of flow based on the mean circulation time between arterioles and venules. Measurements in STZ rats were compared to age-matched nondiabetic controls. In addition, the retinal distribution of fluorescently-labeled red blood cells (RBCs) was viewed by confocal microscopy in excised flat mounts. Results. Retinal blood flow rate was found to decrease by approximately 33% in the STZ rats compared to controls (P < 0.001) as assessed by the microsphere technique. However, in striking contrast, the mean circulation time through the retina was found to be almost 3× faster in the STZ rats (P < 0.01). This contradiction could be explained by flow redistribution through the superficial vessels of the diabetic retina, with this possibility supported by our observation of significantly fewer RBCs flowing through the deeper capillaries. Conclusions. We conclude that retinal blood flow rate is reduced significantly in the diabetic rat, with a substantial decrease of flow through the capillaries due to shunting of blood through the superficial layer, allowing rapid transit from arterioles to venules. PMID:23572104

  4. Iodoamphetamine as a new tracer for local cerebral blood flow in the rat: comparison with isopropyliodoamphetamine.

    PubMed

    Rapin, J R; Le Poncin-Lafitte, M; Duterte, D; Rips, R; Morier, E; Lassen, N A

    1984-06-01

    Rats were injected with iodoamphetamine synthesized and labeled with 125I or with 125I- isopropyliodoamphetamine , a molecule of established value for the determination of local cerebral blood flow. The blood kinetics, tissue distribution, and brain uptake index for each tracer exhibited practically no differences. Autoradiographic quantification of the local cerebral blood flow, calculated according to the microsphere model, produced identical results for both molecules. However, compared with the values reported for other tracers, our values constituted an underestimation of white matter blood flow and a more real estimation of hippocampal flow. It is concluded from the brain uptake of the derivatives of both amphetamines during the first minutes following their injection that these tracers can be used as a chemical microembolus for the measurement of local cerebral blood flow. PMID:6725437

  5. Iodoamphetamine as a new tracer for local cerebral blood flow in the rat: comparison with isopropyliodoamphetamine

    SciTech Connect

    Rapin, J.R.; Le Poncin-Lafitte, M.; Duterte, D.; Rips, R.; Morier, E.; Lassen, N.A.

    1984-06-01

    Rats were injected with iodoamphetamine synthesized and labeled with /sup 125/I or with /sup 125/I- isopropyliodoamphetamine, a molecule of established value for the determination of local cerebral blood flow. The blood kinetics, tissue distribution, and brain uptake index for each tracer exhibited practically no differences. Autoradiographic quantification of the local cerebral blood flow, calculated according to the microsphere model, produced identical results for both molecules. However, compared with the values reported for other tracers, our values constituted an underestimation of white matter blood flow and a more real estimation of hippocampal flow. It is concluded from the brain uptake of the derivatives of both amphetamines during the first minutes following their injection that these tracers can be used as a chemical microembolus for the measurement of local cerebral blood flow.

  6. Micro-PIV quantification of capillary blood flow redistribution caused by laser-assisted vascular occlusion

    NASA Astrophysics Data System (ADS)

    Kurochkin, Maxim A.; Stiukhina, Elena S.; Fedosov, Ivan V.; Postnov, Dmitry E.; Tuchin, Valery V.

    2016-04-01

    We propose μPIV-based technique for quantitative assessment of blood flow redistribution in microcirculatory networks. Our approach is based on per-segment averaging of measured quantities so we can avoid most of problems that are typical for point-wise measurements. The key point of our technique is the digital processing algorithms of recorded data that include: capillary network axial line construction; interrogation regions centering; blood flow velocity local estimate using PIV approach; blood flow velocity calculation by means of averaging over entire vessel segment; the calculation of blood volume flow rate map. We illustrate the application of developed technique with in vivo measurements and blood flow velocity map reconstruction for chorioallantoic membrane (CAM) of chicken embryo, in which the local vascular occlusion was produced using continuous wave laser light irradiation..

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  8. Blood flow measurements in the ears of patients receiving cochlear implants.

    PubMed

    Nakashima, Tsutomu; Hattori, Taku; Sone, Michihiko; Sato, Eisuke; Tominaga, Mitsuo

    2002-11-01

    We measured cochlear blood flow in 12 patients who received cochlear implants, using a laser-Doppler probe with an outer diameter of 0.8 mm. The subjects had congenital deafness, idiopathic progressive sensorineural hearing loss, Waardenburg's syndrome, narrow internal auditory canal, or sudden deafness. Putting the probe tip to the site of drilling for cochlear implantation, we measured blood flow before, during, and after the cochlear bony wall was opened. The laser-Doppler output was confirmed even after the tip of the probe was inserted into the perilymphatic space in all cases. Our results revealed that blood flow was maintained in all cochleas, although there was a probability of reduction in blood flow volume. We conclude that laser-Doppler flowmetry is both relatively safe and useful for measuring blood flow in the ears during cochlear implantation procedures.

  9. Computational modelling of blood-flow-induced changes in blood electrical conductivity and its contribution to the impedance cardiogram.

    PubMed

    Trakic, A; Akhand, M; Wang, H; Mason, D; Liu, F; Wilson, S; Crozier, S

    2010-01-01

    Studies have shown that blood-flow-induced change in electrical conductivity is of equal importance in assessment of the impedance cardiogram (ICG) as are volumetric changes attributed to the motion of heart, lungs and blood vessels. To better understand the sole effect of time-varying blood conductivity on the spatiotemporal distribution of trans-thoracic electric fields (i.e. ICG), this paper presents a segmented high-resolution (1 mm(3)) thoracic cardiovascular system, in which the time-varying pressures, flows and electrical conductivities of blood in different vessels are evaluated using a set of coupled nonlinear differential equations, red blood cell orientation and cardiac cycle functions. Electric field and voltage simulations are performed using two and four electrode configurations delivering a small alternating electric current to an anatomically realistic and electrically accurate model of modelled human torso. The simulations provide a three-dimensional electric field distribution and show that the time-varying blood conductivity alters the voltage potential difference between the electrodes by a maximum of 0.28% for a cardiac output of about 5 L min(-1). As part of a larger study, it is hoped that this initial model will be useful in providing improved insights into blood-flow-related spatiotemporal electric field variations and assist in the optimal placement of electrodes in impedance cardiography experiments.

  10. Multi-modal in vivo imaging of brain blood oxygenation, blood flow and neural calcium dynamics during acute seizures

    NASA Astrophysics Data System (ADS)

    Ringuette, Dene; Jeffrey, Melanie A.; Carlen, Peter L.; Levi, Ofer

    2016-03-01

    Dysfunction of the vascular endothelium has been implicated in the development of epilepsy. To better understand the relation between vascular function and seizure and provide a foundation for interpreting results from functional imaging in chronic disease models, we investigate the relationship between intracellular calcium dynamics and local cerebral blood flow and blood oxygen saturation during acute seizure-like events and pharmacological seizure rescue. To probe the relation between the aforementioned physiological markers in an acute model of epilepsy in rats, we integrated three different optical modalities together with electrophysiological recordings: Laser speckle contrast imaging (LSCI) was used to study changes in flow speeds, Intrinsic optical signal imaging (IOSI) was used to monitor changes in oxygenated, de-oxygenated, and total hemoglobin concentration, and Calcium-sensitive dye imaging was used to monitor intracellular calcium dynamics. We designed a dedicated cortical flow chamber to remove superficial blood and dye resulting from the injection procedure, which reduced spurious artifacts. The near infrared light used for IOSI and LSCI was delivered via a light pipe integrated with the flow chamber to minimize the effect of fluid surface movement on illumination stability. Calcium-sensitive dye was injected via a glass electrode used for recording the local field potential. Our system allowed us to observe and correlate increases in intracellular calcium, blood flow and blood volume during seizure-like events and provide a quantitative analysis of neurovascular coupling changes associated with seizure rescue via injection of an anti-convulsive agent.

  11. Modeling and numerical simulation of blood flow using the Theory of Interacting Continua

    PubMed Central

    Massoudi, Mehrdad; Kim, Jeongho; Antaki, James F.

    2011-01-01

    In this paper we use a modified form of the mixture theory developed by Massoudi and Rajagopal to study the blood flow in a simple geometry, namely flow between two plates. The blood is assumed to behave as a two-component mixture comprised of plasma and red blood cells (RBCs). The plasma is assumed to behave as a viscous fluid whereas the RBCs are given a granular-like structure where the viscosity also depends on the shear-rate. PMID:22611284

  12. Brain blood-flow changes during motion sickness. [thalamus vascular changes in dogs during swing tests

    NASA Technical Reports Server (NTRS)

    Johnson, W. H.; Hsuen, J.

    1973-01-01

    The possibility of diminished blood flow in the brain is studied as one of the factors resulting from an increase in skeletal muscle blood volume concomitant with other characteristics of motion sickness. Thermistors are implanted in the thalamus of dogs and blood flow changes are recorded while they are subjected to sinusoidal movement on a two pole swing. Results of these initial steps in a proposed long term exploration of different areas of the brain are presented.

  13. Computer simulation of blood flow patterns in arteries of various geometries.

    PubMed

    Wong, P K; Johnston, K W; Ethier, C R; Cobbold, R S

    1991-11-01

    The purpose of this study is to illustrate the application of computer simulation to the study of blood flow through arteries and to demonstrate the relationship between geometry of the vessels and local flow patterns. A finite element computer program was developed to simulate steady and pulsatile blood flow by solving the continuity and Navier-Stokes equations. The accuracy of the computational method has been confirmed by comparing the numeric results to analytic solutions and to published experimental data from physical models. The results are presented as plots of the velocity vectors, streamlines, and pressure contours. The computational model has been applied to illustrate flow patterns in the following situations: pulsatile flow in a cylindric artery and an artery with an axisymmetric stenosis, steady flow in cylindric arteries with stenoses of varying severity and with different flow rates, steady flow in an artery containing a fusiform aneurysm, steady flow in a two-dimensional model of a symmetric Y-shaped bifurcation, and steady flow in a two-dimensional model of the carotid bifurcation. Regions that are commonly associated with arterial disease often coincide with zones of reversed or stagnant flow. In conclusion, the versatility and feasibility of computational simulation of blood flow is illustrated by this study. Although this mathematic model is a simplification of the real flow phenomena, it yields results that provide useful insights into the understanding of local blood flow patterns for a variety of complex geometries.

  14. Effect of vasopressors on organ blood flow during endotoxin shock in pigs

    SciTech Connect

    Breslow, M.J.; Miller, C.F.; Parker, S.D.; Walman, A.T.; Traystman, R.J.

    1987-02-01

    A volume-resuscitated porcine endotoxin shock model was used to evaluate the effect on organ blood flow of increasing systemic arterial blood pressure with vasopressors. Administration of 0.05-0.2 mg/kg of Escherichia coli endotoxin (E) reduced mean arterial blood pressure (MAP) to 50 mmHg, decreased systemic vascular resistance to 50% of control, and did not change cardiac output or heart rate. Blood flow measured with radiolabeled microspheres to brain, kidney, spleen, and skeletal muscle was reduced during endotoxin shock, but blood flow to left ventricle, small and large intestine, and stomach remained at pre-endotoxin levels throughout the study period. Four groups of animals were used to evaluate the effect of vasopressor therapy. Vasopressors were administered starting 60 min after E exposure, and the dose of each was titrated to increase MAP to 75 mmHg. Despite the increase in MAP, brain blood flow did not increase in any group. Norepinephrine alone increased blood flow to the left ventricle. The dose of norepinephrine required to increase MAP by 20-25 mmHg during E shock was 30 times the does required for a similar increase in MAP in animals not receiving E. The authors conclude 1) that hypotension in the fluid resuscitated porcine E shock model is primarily the result of peripheral vasodilatation, 2) that the vascular response to vasoconstrictors in this model is markedly attenuated following E administration, 3) that blood pressure elevation with norepinephrine, dopamine, and phenylephrine neither decreases blood flow to any organs nor increases blood flow to organs with reduced flow, and 4) that norepinephrine, dopamine, and phenylephrine affect regional blood flow similarly in this model.

  15. Mechanisms underlying phase lag between systemic arterial blood pressure and cerebral blood flow velocity.

    PubMed

    Kuo, Terry B J; Chern, Chang-Ming; Yang, Cheryl C H; Hsu, Hung-Yi; Wong, Wen-Jang; Sheng, Wen-Yung; Hu, Han-Hwa

    2003-01-01

    To explore the mechanisms underlying the phase lag between oscillations in arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV), ABP and CBFV signals were recorded noninvasively from normal volunteers who lay quietly in a supine position. Mean ABP (MAP) and CBFV (MFV) were calculated beat-to-beat by means of integration. Cerebral vascular resistance (CVR) was calculated by dividing MAP with MFV. Frequency domain analysis of MAP, MFV and CVR signals revealed very-low frequency (VLF, 0.016-0.04 Hz), low-frequency (LF, 0.04-0.15 Hz), and high-frequency (HF, 0.15-0.4 Hz) components. The transfer phase of MAP-CVR coupling in the LF and HF range was frequency-dependent, which is equivalent to a time delay of 2 s. However, the transfer phase differed in the CVR-MFV coupling in that the phase was distributed around 180 degrees across the LF and HF ranges. Cross-correlation analysis revealed a positive relationship between MAP-CVR coupling, with MAP leading by 2 s, and a negative relationship between CVR-MFV coupling, with CVR leading by 0.3 s. We concluded that the phase lag between oscillations in ABP and CBFV was chiefly contributed to by the starting latency of cerebral autoregulation (i.e. cerebral vasomotion, revealed by MAP-CVR coupling). Moreover, the negative correlation of the CVR-MFV coupling could offer a different explanation for the physiologic significance of the phase lead of CBFV-ABP oscillations.

  16. Intensive blood pressure lowering increases cerebral blood flow in older subjects with hypertension.

    PubMed

    Tryambake, Dinesh; He, Jiabao; Firbank, Michael J; O'Brien, John T; Blamire, Andrew M; Ford, Gary A

    2013-06-01

    Hypertension is associated with reduced cerebral blood flow (CBF). Intensive (<130/80 mm Hg) blood pressure (BP) lowering in older people might give greater reduction in cardiovascular risk, but there are concerns that this might produce hypoperfusion which may precipitate falls and possibly stroke. We determined the effect of intensive compared with usual BP lowering on CBF in hypertensive older subjects. Individuals aged >70 years with a history of systolic hypertension on 1 or no BP lowering drugs were recruited from primary care (n=37; age, 75±4 years; systolic BP, >150 mm Hg) and randomized to receive intensive (target BP, <130/80 mm Hg) or usual (target BP, <140/85 mm Hg) BP lowering for 12 weeks, with reviews every 2 weeks. CBF, determined using 3T arterial spin labeling MRI, and 24-hour ambulatory BP were performed at baseline and after 12 weeks of treatment. Baseline BP (ambulatory or in clinic) and baseline gray matter CBF were not significantly different between the groups. After treatment, BP was reduced significantly in both groups but fell more in the intensive group (26/17 versus 15/5 mm Hg; P<0.01). Over the same period, gray matter CBF increased significantly in the intensive group (7±11 mL/min per 100 g; P=0.013) but was unchanged in the usual BP target group (-3±9 mL/min per 100 g; P=0.23); P<0.01 for comparison. Intensive BP lowering in older people with hypertension increases CBF, compared with BP lowering to usual target. These findings suggest hypertension in older people shifts the autoregulatory CBF curve rightward and downward and is reversible with BP lowering.

  17. Noninvasive color Doppler sonography of uterine blood flow throughout pregnancy in sheep and goats.

    PubMed

    Elmetwally, M; Rohn, K; Meinecke-Tillmann, S

    2016-04-01

    In contrast to cattle or horses, uterine blood flow in small ruminants has been investigated predominantly after surgical intervention and chronic instrumentation. The objective of the present study was to investigate the clinical applicability of noninvasive color Doppler sonography to characterize blood flow in the maternal uterine artery of sheep, n = 11 (18 pregnancies) and goats, n = 11 (20 pregnancies). The following parameters were measured transrectally or transabdominally: blood flow volume, time-averaged maximum velocity (TAMV), resistance index (RI), pulsatility index (PI), Time-averaged mean velocity, impedance of blood flow (AB or systolic/diastolic [S/D] velocity ratio), peak velocity of blood flow and blood flow acceleration. Examinations started 2 weeks after breeding and continued at 2-week intervals until parturition. Outcomes for sheep and goats were similar and will be discussed together. Based on noninvasive color Doppler sonography, blood flow volume increased (approximately 60-fold, P < 0.0001) until the end of pregnancy, with a rapid increase early in gestation, and a slow increase after week 18. Time-averaged maximum velocity in the uterine artery increased (approximately 4-fold; P < 0.0001) throughout pregnancy in sheep and goats. Furthermore, for uterine artery blood flow, there was an effect of stage of pregnancy on PI and RI (P < 0.001 and P < 0.0001, respectively), both indices decreased until the end of gestation. Time-averaged mean velocity decreased from week 18 to 20 in both species. The blood flow acceleration increased (P < 0.0001) until week 16 and week 14 in sheep and goats, respectively, and then decreased until parturition. Similar to PI and RI, vascular impedance of the uterine decreased (P < 0.0001) throughout pregnancy. This is apparently the first study using noninvasive color Doppler sonography of uterine blood flow throughout physiological pregnancy in small ruminants. Clearly, this technology facilitates repeated

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

    SciTech Connect

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

    1984-05-31

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

  19. Effects of fluid recirculation on mass transfer from the arterial surface to flowing blood

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Guo; Zhang, Xi-Wen; Liu, Ying-Xi

    2012-06-01

    The effect of disturbed flow on the mass transfer from arterial surface to flowing blood was studied numerically, and the results were compared with that of our previous work. The arterial wall was assumed to be viscoelastic and the blood was assumed to be incompressible and non-Newtonian fluid, which is more close to human arterial system. Numerical results indicated that the mass transfer from the arterial surface to flowing blood in regions of disturbed flow is positively related with the wall shear rates and it is significantly enhanced in regions of disturbed flow with a local minimum around the reattachment point which is higher than the average value of the downstream. Therefore, it may be implied that the accumulation of cholesterol or lipids within atheromatous plaques is not caused by the reduced efflux of cholesterol or lipids, but by the infiltration of the LDL (low-density lipoprotein) from the flowing blood to the arterial wall.

  20. Forearm blood flow responses of offspring of hypertensives to an extended stress task.

    PubMed

    Ditto, B; Miller, S B

    1989-02-01

    The forearm blood flow and other cardiovascular responses of 10 healthy young men with a parental history of hypertension to an extended laboratory stressor were compared with the responses of 10 age-matched men with normotensive parents. To eliminate the effects of the anticipation of stress on baseline measures, all subjects participated in a separate 1-hour counterbalanced baseline session in which no stress was presented. There were no significant differences between the two groups in resting blood pressure, heart rate, blood volume pulse, forearm blood flow and vascular resistance, and self-report anxiety, although offspring of hypertensive parents exhibited marginally greater (p = 0.08) forearm blood flow at rest. During the stress session, subjects played video games for 1 hour and avoided mild electric shocks depending on performance. Offspring of hypertensive parents exhibited significantly greater heart rate (+19 +/- 6 vs. +3 +/- 2%), forearm blood flow (+52 +/- 14 vs. +9 +/- 4%), and self-report anxiety (+25 +/- 6 vs. +9 +/- 3%) responses to the task. There were no significant group differences in blood pressure response to the task. Significant positive correlations between forearm blood flow and heart rate responses to the task were observed. These findings extend earlier results that suggested healthy young offspring of hypertensive and normotensive parents may exhibit different patterns of hemodynamic response to stress in the absence of differences in resting blood pressure or blood pressure responsiveness to stress. PMID:2914737

  1. Forearm blood flow responses of offspring of hypertensives to an extended stress task.

    PubMed

    Ditto, B; Miller, S B

    1989-02-01

    The forearm blood flow and other cardiovascular responses of 10 healthy young men with a parental history of hypertension to an extended laboratory stressor were compared with the responses of 10 age-matched men with normotensive parents. To eliminate the effects of the anticipation of stress on baseline measures, all subjects participated in a separate 1-hour counterbalanced baseline session in which no stress was presented. There were no significant differences between the two groups in resting blood pressure, heart rate, blood volume pulse, forearm blood flow and vascular resistance, and self-report anxiety, although offspring of hypertensive parents exhibited marginally greater (p = 0.08) forearm blood flow at rest. During the stress session, subjects played video games for 1 hour and avoided mild electric shocks depending on performance. Offspring of hypertensive parents exhibited significantly greater heart rate (+19 +/- 6 vs. +3 +/- 2%), forearm blood flow (+52 +/- 14 vs. +9 +/- 4%), and self-report anxiety (+25 +/- 6 vs. +9 +/- 3%) responses to the task. There were no significant group differences in blood pressure response to the task. Significant positive correlations between forearm blood flow and heart rate responses to the task were observed. These findings extend earlier results that suggested healthy young offspring of hypertensive and normotensive parents may exhibit different patterns of hemodynamic response to stress in the absence of differences in resting blood pressure or blood pressure responsiveness to stress.

  2. Blood flow distribution in a polymyxin coated fibrous bed for endotoxin removal. Effect of a new blood path design.

    PubMed

    Ronco, C; Brendolan, A; Scabardi, M; Ronco, F; Nakamura, H

    2001-03-01

    The analysis of flow distribution in cartridges designed for hemoperfusion is extremely important. Taking advantage of a new imaging technique, based on the analysis of a helical scanner-generated imaging sequence, we studied the blood flow distribution in a series of cartridges for extracorporeal removal of endotoxin. Cartridges with improved design were compared to cartridges with a standard design. The improved design consists in a different structure of the holes of the distributor of the flow within the adsorbent unit. Cartridges were studied in vitro with human blood from voluntary donors at blood flows of 100 and 250 ml/min. The progression of density in specific regions of interest (ROI) was analyzed to detect the distribution of the dye injected in the blood circuit. The study demonstrates that both at 100 ml/min and at 250 ml/min of blood flow, the progression of flow appears more homogeneous in the devices with improved design. In detail, the flow distribution measured by the incremental density values detected in the ROIs of the proximal comers (close to the arterial port) and in the ROIs of the central region of the device (close to the inner wall of the case) displays a significant difference between the standard and the improved device. The ROIs studied in the standard devices display a slower increase in density and significantly lower absolute values expressed in Hounsfield units. The experimental method utilized to analyze flow distribution seems to represent an important means to study the performance and design of this type of device.

  3. Local anaesthetic techniques and pulsatile ocular blood flow

    PubMed Central

    Chang, B.; Hee, W.; Ling, R.; Broadway, D.; Beigi, B.

    2000-01-01

    AIM—To compare pulsatile ocular blood flow (POBF) and intraocular pressure (IOP) between eyes of patients receiving either peribulbar (with and without balloon compression) or subconjunctival local anaesthesia (LA).
METHODS—30 eyes of 30 patients undergoing cataract surgery by phacoemulsification were investigated in a study of parallel group design. Ten patients had peribulbar LA and 10 minutes compression with a Honan's balloon (group A). A further 10 patients who received peribulbar LA alone (group B) acted as controls for the effects of balloon compression. Ten other patients were given subconjunctival LA (group C). POBF and IOP were measured using a modified Langham pneumatonometer. Three measurements were made in each eye, the first recording immediately before LA, the second 1 minute after, and the third 10 minutes after LA.
RESULTS—No significant change in POBF or IOP was recorded in eyes receiving subconjunctival LA. In the peribulbar groups (A and B), there was a drop in median POBF of 252 and 138 µl/min respectively 1 minute after LA, which was statistically significant in both groups (p<0.01). By 10 minutes, POBF tended to return to baseline levels, but remained significantly reduced in group B (p<0.05). In addition, there was a significant (p<0.05) reduction in IOP (mean drop of 4.82 mm Hg) in group A following peribulbar LA with balloon compression.
CONCLUSIONS—POBF was significantly reduced after peribulbar LA but was unchanged after subconjunctival LA. Balloon compression reduced IOP and improved POBF following peribulbar LA. The findings may have clinical implications in patients with compromised ocular circulation or significant glaucomatous optic neuropathy.

 PMID:11049951

  4. Blood flow velocity in monocular retinoblastoma assessed by color doppler

    PubMed Central

    Bonanomi, Maria Teresa B C; Saito, Osmar C; de Lima, Patricia Picciarelli; Bonanomi, Roberta Chizzotti; Chammas, Maria Cristina

    2015-01-01

    OBJECTIVE: To analyze the flow of retrobulbar vessels in retinoblastoma by color Doppler imaging. METHODS: A prospective study of monocular retinoblastoma treated by enucleation between 2010 and 2014. The examination comprised fundoscopy, magnetic resonance imaging, ultrasonography and color Doppler imaging. The peak blood velocities in the central retinal artery and central retinal vein of tumor-containing eyes (tuCRAv and tuCRVv, respectively) were assessed. The velocities were compared with those for normal eyes (nlCRAv and nlCRVv) and correlated with clinical and pathological findings. Tumor dimensions in the pathological sections were compared with those in magnetic resonance imaging and ultrasonography and were correlated with tuCRAv and tuCRVv. In tumor-containing eyes, the resistivity index in the central retinal artery and the pulse index in the central retinal vein were studied in relation to all variables. RESULTS: Eighteen patients were included. Comparisons between tuCRAv and nlCRAv and between tuCRVv and nlCRVv revealed higher velocities in tumor-containing eyes (p<0.001 for both), with a greater effect in the central retinal artery than in the central retinal vein (p=0.024). Magnetic resonance imaging and ultrasonography measurements were as reliable as pathology assessments (p=0.675 and p=0.375, respectively). A positive relationship was found between tuCRAv and the tumor volume (p=0.027). The pulse index in the central retinal vein was lower in male patients (p=0.017) and in eyes with optic nerve invasion (p=0.0088). CONCLUSIONS: TuCRAv and tuCRVv are higher in tumor-containing eyes than in normal eyes. Magnetic resonance imaging and ultrasonography measurements are reliable. The tumor volume is correlated with a higher tuCRAv and a reduced pulse in the central retinal vein is correlated with male sex and optic nerve invasion. PMID:26735219

  5. Induction of ventricular collapse by an axial flow blood pump.

    PubMed

    Amin, D V; Antaki, J F; Litwak, P; Thomas, D; Wu, Z J; Watach, M

    1998-01-01

    An important consideration for clinical application of rotary blood pump based ventricular assist is the avoidance of ventricular collapse due to excessive operating speed. Because healthy animals do not typically demonstrate this phenomenon, it is difficult to evaluate control algorithms for avoiding suction in vivo. An acute hemodynamic study was thus conducted to determine the conditions under which suction could be induced. A 70 kg calf was implanted with an axial flow assist device (Nimbus/UoP IVAS; Nimbus Inc., Rancho Cordova, CA) cannulated from the left ventricular apex to ascending aorta. On initiation of pump operation, several vasoactive interventions were performed to alter preload, afterload, and contractility of the left ventricle. Initially, dobutamine increased contractility and heart rate ([HR] = 139; baseline = 70), but ventricular collapse was not achievable, even at the maximal pump speed of 15,000 rpm. Norepinephrine decreased HR (HR = 60), increased contractility, and increased systemic vascular resistance ([SVR] = 24; baseline = 15), resulting in ventricular collapse at a pump speed of 14,000 rpm. Isoproterenol (beta agonist) increased HR (HR = 103) and decreased SVR (SVR = 12), but ventricular collapse was not achieved. Inferior vena cava occlusion reduced preload, and ventricular collapse was achieved at speeds as low as 11,000 rpm. Esmolol (beta1 antagonist) decreased HR (HR = 55) and contractility, and ventricular collapse was achieved at 11,500 rpm. Episodes of ventricular collapse were characterized initially by the pump output exceeding the venous return and the aortic valve remaining closed throughout the cardiac cycle. If continued, the mitral valve would remain open throughout the cardiac cycle. Using these unique states of the mitral and aortic valves, the onset of ventricular collapse could reliably be identified. It is hoped that the ability to detect the onset of ventricular collapse, rather than the event itself, will assist in

  6. Cerebral glucose utilization and blood flow in Huntington's Disease (HD)

    SciTech Connect

    Phelps, M.E.; Mazziotta, J.C.; Wapenski, J.; Riege, W.; Baxter, L.R.

    1985-05-01

    Previous studies in the authors' Laboratory have been carried out on 13 patients symptomatic of HD (SHD) and 15 asymptomatic at-risk for HD (ARHD) with a ECAT II and identification of changes in caudate metabolism using an index technique. The authors report now studies of additional 28 subjects (11 SHD, 17 ARHD) studied drug free and compared to age/sex matched controls using the higher resolution NeuroECAT, FDG for glucose utilization (LCMRGlc) and 0-15 water for cerebral blood flow (CBF). Patients had neurological, psychiatric-tests, x-ray CT and were video taped to determine type, timing and amount of choreathetic movements during study. In SHD (disease duration 4.9 +- 2.7 yrs), significant decreases (30%) in LCMRGlc were found in striatum (SHD=19.3 +- 7.7, controls = 29.9 +- 5.8 ..mu.. moles/min/100g) despite no to moderate caudate atrophy on x-ray CT. Hemisphere and cortical CMRGlc were not significantly decreased. There was a significant correlation between disease duration and ratio of caudate to putamen (Cd/Put). Pattern of LCMRGlc and CBF matched in SHD. The caudate to hemisphere LCMRGlc ratio was not different between ARHD and controls except variance was about 4 times greater for ARHD (ARHD=1.21 +- 0.15, controls = 1.28 +- 0.04) indicating presence of subpopulations in ARHD group. Four ARHD subjects had a ratio of 1 Std. Dev. from mean of SHD (no normals had values in this range). The 2 ARHD subjects with lowest caudate LCMRGlc had Cd/Put ratios > 2 Std. Dev. from controls. Results show 1) LCMRGlc abnormalities in all SHD patients and subpopulations in ARHD, 2) metabolic alterations appear to begin in caudate and spread to putamen and that a Cd/Put value of 0.7 should be found at start of symptoms, and 3) cortex and thalamus are relatively spared in ARHD and early SHD.

  7. Retinal blood flow measurement by circumpapillary Fourier domain Doppler optical coherence tomography.

    PubMed

    Wang, Yimin; Bower, Bradley A; Izatt, Joseph A; Tan, Ou; Huang, David

    2008-01-01

    We present in vivo human total retinal blood flow measurements using Doppler Fourier domain optical coherence tomography (OCT). The scan pattern consisted of two concentric circles around the optic nerve head, transecting all retinal branch arteries and veins. The relative positions of each blood vessel in the two OCT conic cross sections were measured and used to determine the angle between the OCT beam and the vessel. The measured angle and the Doppler shift profile were used to compute blood flow in the blood vessel. The flows in the branch veins was summed to give the total retinal blood flow at one time point. Each measurement of total retinal blood flow was completed within 2 s and averaged. The total retinal venous flow was measured in one eye each of two volunteers. The results were 52.90+/-2.75 and 45.23+/-3.18 microlmin, respectively. Volumetric flow rate positively correlated with vessel diameter. This new technique may be useful in the diagnosis and treatment of optic nerve and retinal diseases that are associated with poor blood flow, such as glaucoma and diabetic retinopathy.

  8. In Vivo Imaging of Mammalian Cochlear Blood Flow Using Fluorescence Microendoscopy

    PubMed Central

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

    2010-01-01

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

  9. Optimizing dynamic T2* MR imaging for measurement of cerebral blood flow using infusions for cerebral blood volume.

    PubMed

    Newman, G C; Hospod, F E; Fain, S B; Cook, T D

    2006-01-01

    We describe an approach to measuring cerebral blood flow (CBF) based on independent measurements of cerebral blood volume (CBV) and mean transit time (MTT) with calculation of CBF by using the central volume theorem: CBF = CBV / MTT. This permits optimization of the individual acquisitions and analyses. In particular, measurement of CBV during contrast infusion, rather than simultaneously with MTT from a single bolus, yields values more consistent with those of other methods.

  10. 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

  11. 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.

  12. Intraocular Pressure, Blood Pressure, and Retinal Blood Flow Autoregulation: A Mathematical Model to Clarify Their Relationship and Clinical Relevance

    PubMed Central

    Guidoboni, Giovanna; Harris, Alon; Cassani, Simone; Arciero, Julia; Siesky, Brent; Amireskandari, Annahita; Tobe, Leslie; Egan, Patrick; Januleviciene, Ingrida; Park, Joshua

    2014-01-01

    Purpose. This study investigates the relationship between intraocular pressure (IOP) and retinal hemodynamics and predicts how arterial blood pressure (BP) and blood flow autoregulation (AR) influence this relationship. Methods. A mathematical model is developed to simulate blood flow in the central retinal vessels and retinal microvasculature as current flowing through a network of resistances and capacitances. Variable resistances describe active and passive diameter changes due to AR and IOP. The model is validated by using clinically measured values of retinal blood flow and velocity. The model simulations for six theoretical patients with high, normal, and low BP (HBP-, NBP-, LBP-) and functional or absent AR (-wAR, -woAR) are compared with clinical data. Results. The model predicts that NBPwAR and HBPwAR patients can regulate retinal blood flow (RBF) as IOP varies between 15 and 23 mm Hg and between 23 and 29 mm Hg, respectively, whereas LBPwAR patients do not adequately regulate blood flow if IOP is 15 mm Hg or higher. Hemodynamic alterations would be noticeable only if IOP changes occur outside of the regulating range, which, most importantly, depend on BP. The model predictions are consistent with clinical data for IOP reduction via surgery and medications and for cases of induced IOP elevation. Conclusions. The theoretical model results suggest that the ability of IOP to induce noticeable changes in retinal hemodynamics depends on the levels of BP and AR of the individual. These predictions might help to explain the inconsistencies found in the clinical literature concerning the relationship between IOP and retinal hemodynamics. PMID:24876284

  13. Development of a Flexible Implantable Sensor for Postoperative Monitoring of Blood Flow

    PubMed Central

    Cannata, Jonathan M.; Chilipka, Thomas; Yang, Hao-Chung; Han, Sukgu; Ham, Sung W.; Rowe, Vincent L.; Weaver, Fred A.; Shung, K. Kirk; Vilkomerson, David

    2013-01-01

    We have developed a blood flow measurement system using Doppler ultrasound flow sensors fabricated of thin and flexible piezoelectric-polymer films. These flow sensors can be wrapped around a blood vessel and accurately measure flow. The innovation that makes this flow sensor possible is the diffraction-grating transducer. A conventional transducer produces a sound beam perpendicular to its face; therefore, when placed on the wall of a blood vessel, the Doppler shift in the backscattered ultrasound from blood theoretically would be 0. The diffraction-grating transducer produces a beam at a known angle to its face; therefore, backscattered ultrasound from the vessel will contain a Doppler signal. Flow sensors were fabricated by spin coating a poly(vinylidene fluoride–trifluoroethylene) copolymer film onto a flexible substrate with patterned gold electrodes. Custom-designed battery-operated continuous wave Doppler electronics along with a laptop computer completed the system. A prototype flow sensor was evaluated experimentally by measuring blood flow in a flow phantom and the infrarenal aorta of an adult New Zealand White rabbit. The flow phantom experiment demonstrated that the error in average velocity and volume blood flow was less than 6% for 30 measurements taken over a 2.5-hour period. The peak blood velocity through the rabbit infrarenal aorta measured by the flow sensor was 118 cm/s, within 1.7% of the measurement obtained using a duplex ultrasound system. The flow sensor and electronics operated continuously during the course of the 5-hour experiment after the incision on the animal was closed. PMID:23091251

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

    PubMed

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

    2014-09-01

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

  15. Anxiety and cerebral blood flow during behavioral challenge. Dissociation of central from peripheral and subjective measures

    SciTech Connect

    Zohar, J.; Insel, T.R.; Berman, K.F.; Foa, E.B.; Hill, J.L.; Weinberger, D.R.

    1989-06-01

    To investigate the relationship between anxiety and regional cerebral blood flow, we administered behavioral challenges to 10 patients with obsessive-compulsive disorder while measuring regional cerebral blood flow with the xenon 133 inhalation technique. Each patient was studied under three conditions: relaxation, imaginal flooding, and in vivo (actual) exposure to the phobic stimulus. Subjective anxiety, obsessive-compulsive ratings, and autonomic measures (heart rate, blood pressure) increased significantly, but respiratory rate and PCO/sub 2/ did not change across the three conditions. Regional cerebral blood flow increased slightly (in the temporal region) during imaginal flooding, but decreased markedly in several cortical regions during in vivo exposure, when anxiety was highest by subjective and peripheral autonomic measures. These results demonstrate that intense anxiety can be associated with decreased rather than increased cortical perfusion and that ostensibly related states of anxiety (eg, anticipatory and obsessional anxiety) may be associated with opposite effects on regional cerebral blood flow.

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

    PubMed

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

    2015-05-01

    Investigations were conducted in 37 patients, suffering complicated pancreatic pseudocysts. In accordance to data of ultrasound Doppler flowmetry for the blood flow along portal vein, a. hepatis communis, a. mesenterica superior in complicated pancreatic pseudocysts compensatory--adaptive reactions on level of hepatic--spanchnic blood flow are directed towards restriction of the blood inflow through the portal vein system. This is accompanied by the common peripheral vascular resistence raising in basin of a. mesenterica superior, which have depended upon the patients' state severity, caused by reduction of the volume blood flow in a certan vascular collector. The oxygen debt of the liver in these patients is compensated by the volume blood flow enhancement along a. hepatis communis. PMID:26419022

  17. Probing depth and dynamic response of speckles in near infrared region for spectroscopic blood flow imaging

    NASA Astrophysics Data System (ADS)

    Yokoi, Naomichi; Aizu, Yoshihisa

    2016-04-01

    Imaging method based on bio-speckles is a useful means for blood flow visualization of living bodies and, it has been utilized for analyzing the condition or the health state of living bodies. Actually, the sensitivity of blood flow is influenced by tissue optical properties, which depend on the wavelength of illuminating laser light. In the present study, we experimentally investigate characteristics of the blood flow images obtained with two wavelengths of 780 nm and 830 nm in the near-infrared region. Experiments are conducted for sample models using a pork layer, horse blood layer and mirror, and for a human wrist and finger, to investigate optical penetration depth and dynamic response of speckles to the blood flow velocity for two wavelengths.

  18. Grow with the Flow: A Dynamic Tale of Blood Clot Formation

    NASA Astrophysics Data System (ADS)

    Leiderman, Karin; Fogelson, Aaron

    2008-11-01

    The body heals injured blood vessels and prevents bleeding by clotting the blood. Clots are primarily made of blood-borne cells and a fibrous material that is assembled at the site of injury in flowing blood. Clot composition and structure change with local chemistry and fluid dynamics, which in turn alter the flow. To better understand this fluid-structure coupling, we have created a mathematical model to simulate the formation of a blood clot in a dynamic fluid environment. The growing clot is represented as a mixed porous medium whose permeability is dependent on the coagulation chemistry within it. The flow field resulting from a clot with specific calculated permeability and size can then be recovered by solving the Navier-Stokes equations with an added friction term. We report on how this complex fluid-structure interaction affects the limiting factor(s) of blood clot growth.

  19. Numerical analysis of the internal flow field in screw centrifugal blood pump based on CFD

    NASA Astrophysics Data System (ADS)

    Han, W.; Han, B. X.; Y Wang, H.; Shen, Z. J.

    2013-12-01

    As to the impeller blood pump, the high speed of the impeller, the local high shear force of the flow field and the flow dead region are the main reasons for blood damage. The screw centrifugal pump can effectively alleviate the problems of the high speed and the high shear stress for the impeller. The softness and non-destructiveness during the transfer process can effectively reduce the extent of the damage. By using CFD software, the characteristics of internal flow are analyzed in the screw centrifugal pump by exploring the distribution rules of the velocity, pressure and shear deformation rate of the blood when it flows through the impeller and the destructive effects of spiral blades on blood. The results show that: the design of magnetic levitation solves the sealing problems; the design of regurgitation holes solves the problem of the flow dead zone; the magnetic levitated microcirculation screw centrifugal pump can effectively avoid the vortex, turbulence and high shear forces generated while the blood is flowing through the pump. Since the distribution rules in the velocity field, pressure field and shear deformation rate of the blood in the blood pump are comparatively uniform and the gradient change is comparatively small, the blood damage is effectively reduced.

  20. The Rheology of Blood Flow in a Branched Arterial System.

    PubMed

    Shibeshi, Shewaferaw S; Collins, William E

    2005-01-01

    Blood flow rheology is a complex phenomenon. Presently there is no universally agreed upon model to represent the viscous property of blood. However, under the general classification of non-Newtonian models that simulate blood behavior to different degrees of accuracy, there are many variants. The power law, Casson and Carreau models are popular non-Newtonian models and affect hemodynamics quantities under many conditions. In this study, the finite volume method is used to investigate hemodynamics predictions of each of the models. To implement the finite volume method, the computational fluid dynamics software Fluent 6.1 is used. In this numerical study the different hemorheological models are found to predict different results of hemodynamics variables which are known to impact the genesis of atherosclerosis and formation of thrombosis. The axial velocity magnitude percentage difference of up to 2 % and radial velocity difference up to 90 % is found at different sections of the T-junction geometry. The size of flow recirculation zones and their associated separation and reattachment point's locations differ for each model. The wall shear stress also experiences up to 12 % shift in the main tube. A velocity magnitude distribution of the grid cells shows that the Newtonian model is close dynamically to the Casson model while the power law model resembles the Carreau model. ZUSAMMENFASSUNG: Die Rheologie von Blutströmungen ist ein komplexes Phänomen. Gegenwärtig existiert kein allgemein akzeptiertes Modell, um die viskosen Eigenschaften von Blut wiederzugeben. Jedoch gibt es mehrere Varianten unter der allgemeinen Klassifikation von nicht-Newtonschen Modellen, die das Verhalten von Blut mit unterschiedlicher Genauigkeit simulieren. Die Potenzgesetz-, Casson und Carreau-Modelle sind beliebte nicht-New-tonsche Modelle und beeinflussen die hämodynamischen Eigenschaften in vielen Situationen. In dieser Studie wurde die finite Volumenmethode angewandt, um die h

  1. Pulsatile magneto-hydrodynamic blood flows through porous blood vessels using a third grade non-Newtonian fluids model.

    PubMed

    Akbarzadeh, Pooria

    2016-04-01

    In this paper, the unsteady pulsatile magneto-hydrodynamic blood flows through porous arteries concerning the influence of externally imposed periodic body acceleration and a periodic pressure gradient are numerically simulated. Blood is taken into account as the third-grade non-Newtonian fluid. Besides the numerical solution, for small Womersley parameter (such as blood flow through arterioles and capillaries), the analytical perturbation method is used to solve the nonlinear governing equations. Consequently, analytical expressions for the velocity profile, wall shear stress, and blood flow rate are obtained. Excellent agreement between the analytical and numerical predictions is evident. Also, the effects of body acceleration, magnetic field, third-grade non-Newtonian parameter, pressure gradient, and porosity on the flow behaviors are examined. Some important conclusions are that, when the Womersley parameter is low, viscous forces tend to dominate the flow, velocity profiles are parabolic in shape, and the center-line velocity oscillates in phase with the driving pressure gradient. In addition, by increasing the pressure gradient, the mean value of the velocity profile increases and the amplitude of the velocity remains constant. Also, when non-Newtonian effect increases, the amplitude of the velocity profile.

  2. Pulsatile magneto-hydrodynamic blood flows through porous blood vessels using a third grade non-Newtonian fluids model.

    PubMed

    Akbarzadeh, Pooria

    2016-04-01

    In this paper, the unsteady pulsatile magneto-hydrodynamic blood flows through porous arteries concerning the influence of externally imposed periodic body acceleration and a periodic pressure gradient are numerically simulated. Blood is taken into account as the third-grade non-Newtonian fluid. Besides the numerical solution, for small Womersley parameter (such as blood flow through arterioles and capillaries), the analytical perturbation method is used to solve the nonlinear governing equations. Consequently, analytical expressions for the velocity profile, wall shear stress, and blood flow rate are obtained. Excellent agreement between the analytical and numerical predictions is evident. Also, the effects of body acceleration, magnetic field, third-grade non-Newtonian parameter, pressure gradient, and porosity on the flow behaviors are examined. Some important conclusions are that, when the Womersley parameter is low, viscous forces tend to dominate the flow, velocity profiles are parabolic in shape, and the center-line velocity oscillates in phase with the driving pressure gradient. In addition, by increasing the pressure gradient, the mean value of the velocity profile increases and the amplitude of the velocity remains constant. Also, when non-Newtonian effect increases, the amplitude of the velocity profile. PMID:26792174

  3. Experimentally determined blood and water flow limitations for hydrophobic compounds using perfused gills of trout

    SciTech Connect

    Sijm, D.T.H.M.; Verberne, M.E.; Paert, P.; Opperhuizen, A.

    1995-12-31

    The influence of physiologically relevant water and blood flows on the uptake of a number of hydrophobic compounds was investigated using perfused gills of rainbow trout. For all compounds studied, the uptake rate constants increased with water flow at lower flow and remained constant at higher flow. The uptake rate constants did not change when blood flow decreased at lower flow, while they increased at higher flow. Both water and blood flows thus influence the uptake of hydrophobic chemicals. using these experimental data and allometric relations, it was established that the water flow can limit the uptake of hydrophobic chemicals for fish weighing more than 5 g. The flow of water will not limit uptake in fish < 5 g, irrespective of physiological conditions and oxygen concentration. At low oxygen concentration, which will increase the water flow in large fish, the uptake of hydrophobic chemicals may increase with a factor of 5 or more. Increasing the blood flow may maximally increase the uptake of hydrophobic chemicals two-fold, in small as well as in large fish.

  4. Monitoring the blood coagulation process under various flow conditions with optical coherence tomography.

    PubMed

    Xu, Xiangqun; Geng, Jinhai; Teng, Xiangshuai

    2014-04-01

    Our previous work demonstrated that an optical coherence tomography (OCT) technique was able to characterize the whole blood coagulation process. The 1/e light penetration depth (d(1/e)) derived from the profiles of reflectance versus depth was developed for detecting the whole blood coagulation process in static state. To consider the effect of blood flow, in the present study, d(1/e) versus time from the coagulating porcine blood circulated in a mock flow loop with various steady laminar flows at mean flow speed in the range from 5 to 25  mm/s. The variation of d(1/e) was used to represent the change of blood properties during coagulation in different hematocrits (HCT) ranging from 25% to 55%, velocities from 5 to 25  mm/s, and tubing sizes from 0.9 to 2 mm. The results showed that there were positive correlations between coagulation time (t(c)) and HCT, velocity, and tubing size, respectively. In addition, the coagulation rate (S(r)) was decreased with the increase of HCT, velocity, and tubing size. This study testified that HCT, flow velocity, and tubing size were substantial factors affecting the backscattering properties during flowing blood coagulation. Furthermore, OCT has the potential to represent the process of flowing blood coagulation with proper parameters.

  5. Effect of continuous regional vasoactive agent infusion on liver metastasis blood flow.

    PubMed Central

    Dworkin, M. J.; Carnochan, P.; Allen-Mersh, T. G.

    1997-01-01

    Regionally administered vasopressors might increase tumour chemotherapy uptake by differentially constricting normal and tumour blood vessels, leading to a selective increase in blood flow to the tumour. In this study, we compared the effects of the vasopressors angiotensin II, vasopressin and endothelin I and the vasodilator calcitonin gene-related peptide (CGRP) by continuously measuring liver parenchymal and tumour blood flow during a 30-min regional vasoactive infusion in a rat HSN liver metastasis model. Vasopressin and angiotensin II produced a vasoconstriction that decreased despite continued infusion, while endothelin I infusion led to prolonged vasoconstriction with a more gradual onset. CGRP infusion resulted in increased vessel conductance but a reduction in blood flow due to systemic hypotension. The tumour to normal flow ratio (TNR) was transiently increased during infusion of all pressors, but only endothelin I produced sufficient change to result in a rise in average TNR throughout pressor infusion. Continuous liver and tumour blood flow measurement throughout vasoactive infusion demonstrated that the extent and the duration of blood flow change varied with the agents assessed. No vasoactive agent increased tumour blood flow, but endothelin I had the most suitable vasoactive properties for enhancing tumour uptake of continuously infused chemotherapy. PMID:9365170

  6. Hydrogen clearance: Assessment of technique for measurement of skin-flap blood flow in pigs

    SciTech Connect

    Thomson, J.G.; Kerrigan, C.L. )

    1991-10-01

    The hydrogen clearance technique has been used for many years by investigators to determine brain blood flow and has been partially validated in this setting using other methods of blood flow measurement. The method has been modified to allow blood flow measurements in skin, but the accuracy of H2 clearance for measuring skin blood flow has not been determined. Multiple blood flow measurements were performed using H2 clearance and radioactive microspheres on skin flaps and control skin in pigs. On 12 pigs, a total of 117 flap and 42 control skin measurements were available for analysis. There was no significant difference between the two techniques in measuring mean control skin blood flow. In skin flaps, H2 clearance was significantly correlated to microsphere-measured blood flow, but it consistently gave an overestimate. Sources of error may include injury to the tissues by insertion of electrodes, consumption of H2 by the electrodes, or diffusion of H2 from the relatively ischemic flap to its well-vascularized bed. Further studies are necessary to determine the cause of this error and to measure the technique's accuracy in skeletal muscle and other flaps.

  7. Regulation of local subcutaneous blood flow in patients with psoriasis and effects of antipsoriatic treatment on subcutaneous blood flow

    SciTech Connect

    Klemp, P.

    1985-08-01

    Local regulation of the doubled subcutaneous blood flow (SBF) rates in psoriatic lesional skin was studied in 8 patients using a traumatic epicutaneous /sup 133/Xe labeling washout technique. Venous stasis of 40 mm Hg induced a significant reduction in the SBF (-34%, p less than 0.01), i.e., a normal vasoconstrictor response. Limb elevation of 40 cm above heart level induced no statistical changes in the SBF (p = 0.50), i.e., a normal local autoregulation response. This indicates normal, local regulation mechanisms of SBF in psoriasis. In another 8 patients, the effect on SBF of a 4-week antipsoriatic treatment with tar was studied in lesional and symmetrically nonlesional skin areas. One patient was clear of psoriasis on day 22, and was followed only to that time. The mean pretreatment SBF in lesional skin areas was 3.87 +/- SD 0.78 ml X (100 g X min)-1, which was not statistically different from measurements on days 3, 7, 14, and 21 after treatment had started. Between day 21 and day 28, the SBF decreased significantly to 3.38 +/- SD 0.78 ml X (100 g X min)-1, p less than 0.05. The difference between the pretreatment SBF and SBF at the end of treatment was statistically significant, p less than 0.05. The changes in SBF in symmetrically nonlesional skin areas were statistically nonsignificant during the period of treatment. Pretreatment SBF was 2.60 +/- SD 1.08 (N = 8), and on day 28 was 1.91 +/- SD 0.74 ml X (100 g X min)-1 (N = 7). However, the tendency of a decreasing SBF at the end of treatment was a clear trend, since SBF in 6 of 7 patients decreased during the third week and in the patient who was discharged on day 22, a decrease in the SBF was observed on days 14 and 21.

  8. Effect of acetazolamide on cerebral blood flow in subacute and chronic cerebrovascular disease

    SciTech Connect

    Hojer-Pedersen, E.

    1987-09-01

    Acetazolamide increases cerebral blood flow. The generalized and regional changes in blood flow after administration of acetazolamide were evaluated by the xenon-133 inhalation technique in a series of patients with subacute or chronic focal cerebral ischemia. Acetazolamide augmented interhemispheric asymmetry of cerebral blood flow in patients with unilateral occlusion of major cerebral arteries, whereas no significant side-to-side asymmetry was evident in patients with minor arterial lesions. Low flow areas in relation to computed tomography-verified infarcts tended to be larger after administration of acetazolamide. Hyperfrontality was present at rest and during stimulation with acetazolamide. A decline of cerebral blood flow with advancing age was greater in patients than in normal controls. The vasodilator response to acetazolamide did not change with age.

  9. Sympathetic alpha-adrenergic regulation of blood flow and volume in hamsters arousing from hibernation.

    PubMed

    Osborne, P G; Sato, J; Shuke, N; Hashimoto, M

    2005-08-01

    Mammals arousing from hibernation display pronounced regional heterothermy, where the thoracic and head regions warm faster than the abdominal and hindlimb regions. We used laser-Doppler flowmetry to measure peripheral hind foot blood flow during hibernation and arousal and gamma imaging of technetium-labeled albumin to measure whole blood volume distribution in hamsters arousing from hibernation. It was discovered that the hibernating hamster responds to physical but not to sound or hypercapnic stimulation with rapid, 73% reduction of hind foot blood flow. Hind foot blood flow vasoconstriction was maintained from the onset of arousal until late in arousal when rectal temperature was rapidly increased. alpha-Adrenergic blockade early in arousal increased hind foot blood flow by 700%, suggesting that vasoconstriction was mediated by activation of sympathetic tone. Gamma imaging revealed that, by the early phase of arousal from hibernation, the blood volume of the body below the liver is greatly reduced, whereas blood volumes of the thorax and head are much greater than corresponding volumes in anesthetized hamsters. As arousal progresses and cardiac activity increases and regional heterothermy develops, this regional blood volume distribution is largely maintained; however, blood volume slowly decreases in the thoracic region and slowly increases in the shoulder and head regions. The rapid increase in rectal temperature, characteristic of mid- to late- arousal phases, is probably mediated, in part, by reduction of adrenergic tone on abdominal and hindlimb vasculature. Warm blood then moves into the hind body, produces an increase in temperature, blood flow, and blood volume in the hind body and compensatory reductions of blood volume in the neck, head, and thoracic regions.

  10. Longitudinal cerebral blood flow and amyloid deposition: an emerging pattern?

    PubMed Central

    Sojkova, Jitka; Beason-Held, Lori; Zhou, Yun; An, Yang; Kraut, Michael A; Ye, Weigo; Ferrucci, Luigi; Mathis, Chester A; Klunk, William E; Wong, Dean F; Resnick, Susan M

    2008-01-01

    Although cerebral amyloid deposition may precede cognitive impairment by decades, the relationship between amyloid deposition and longitudinal change in neuronal function has not been studied. The aim of this paper is to determine whether nondemented individuals with high and low amyloid burden show different patterns of longitudinal regional cerebral blood flow (rCBF) changes in the years preceding measurement of amyloid deposition. Methods Twenty-eight nondemented participants (mean (SD) age at [11C] PIB 82.5(4.8) yrs; 6 mildly impaired) from the Baltimore Longitudinal Study of Aging underwent yearly resting-state [15O]H2O PET scans for up to 8 years. [11C]PIB images of amyloid deposition were acquired on average 10.8(0.8) years after the first CBF scan. [11C]PIB distribution volume ratios (DVR) of regions of interest were estimated by fitting a reference tissue model to the measured time activity curves. Based on mean cortical DVR, participants were divided into high and low [11C]PIB retention groups. Differences in longitudinal rCBF changes between high and low [11C]PIB groups were investigated by voxel-based analysis. Results Longitudinal rCBF changes differed significantly between high (n=10) and low (n=18) [11C]PIB groups (p<=0.001). Greater longitudinal decreases in rCBF in the high [11C]PIB group were seen in right anterior/mid cingulate, right supramarginal gyrus, left thalamus and midbrain bilaterally relative to the low group. Greater increases in rCBF over time in the high [11C]PIB group were found in left medial and inferior frontal gyri, right precuneus, left inferior parietal lobule, and the left postcentral gyrus. Conclusion In this group of nondemented older adults, those with high [11C]PIB show greater longitudinal declines in rCBF in certain areas, representing regions with greater decrements in neuronal function. Greater longitudinal increases in rCBF are also observed in those with higher amyloid load and may represent an attempt to preserve

  11. Cyclic variations of high-frequency ultrasonic backscattering from blood under pulsatile flow.

    PubMed

    Huang, Chih-Chung

    2009-08-01

    It was shown previously that ultrasonic scattering from whole blood varies during the flow cycle under pulsatile flow both in vitro and in vivo. It has been postulated that the cyclic variations of the backscattering signal are associated with red blood cell (RBC) aggregation in flowing whole blood. To obtain a better understanding of the relationship between blood backscattering and RBC aggregation behavior for pulsatile flowing blood, the present study used high-frequency ultrasound to characterize blood properties. The backscattering signals from both whole blood and an RBC suspension at different peak flow velocities (from 10 to 30 cm/s) and hematocrits (20% and 40%) under pulsatile flow (stroke rate of 20 beats/min) were measured with 3 single-element transducers at frequencies of 10, 35, and 50 MHz in a mock flow loop. To avoid the frequency response problem of a Doppler flowmeter, the integrated backscatter (IB) and flow velocity as functions of time were calculated directly using RF signals from flowing blood. The experimental results showed that cyclic variations of the IB curve were clearly observed at a low flow velocity and a hematocrit of 40% when using 50 MHz ultrasound, and that these variations became weaker as the peak flow velocity increased. However, these cyclic variations were detected only at 10 cm/s when using 10 MHz ultrasound. These results demonstrate that a high flow velocity can stop the formation of rouleaux and that a high hematocrit can promote RBC aggregation to produce cyclic variations of the backscattering signal under pulsatile flow. In addition, slight cyclic variations of the IB curve for an RBC suspension were observed at 35 and 50 MHz. Furthermore, the peak of the IB curve from whole blood led the peak of the velocity waveform when using high-frequency ultrasound, which could be explained by the assumption that a rapid flow can promote RBC aggregation under pulsatile flow. Together, the experimental results showed that the

  12. Blood filling and flow in lungs during change in body position in space

    NASA Technical Reports Server (NTRS)

    Pogodin, A. S.; Mazhbich, B. I.

    1980-01-01

    In the horizontal position (supine and lateral), in the upright position (head up and head down) and during change of the cat body position in space, quantitative responses of regional blood volume and blood flow in the lungs (ml/100 cu cm) revealed presence of the gradient in the gravitation direction. Blood volume and blood flow of different lung portions changed qualitatively and quantitatively in different ways. These changes occurred only in the direction producing the equality of regional hydrostatical and hemodynamic loads in the lungs at either horizontal level.

  13. Effect of nitroglycerin and dipyridamole on regional left ventricular blood flow during coronary artery occlusion.

    PubMed Central

    Becker, L C

    1976-01-01

    Coronary vasodilators have been variously reported to increase, decrease, or have no effect upon blood flow to ischemic myocardium. Consequently, the effects of two different types of dilators, nitroglycerin (TNG) and dipyridamole, were studied with radioactive microspheres in open-chested dogs after coronary artery ligation. Given as a bolus i.v. injection 0.4 mg TNG resulted in an increase in blood flow to nonischemic areas of myocardium and a preservation of flow to ischemic regions, despite a fall in blood pressure. 5 min later blood pressure and nonischemic flow were back to base line, and a small selective increase in flow to ischemic myocardium was found (0.15-0.18 ml/min per g, P less than 0.05). During an 0.2 mg/min infusion of TNG, and also after 1 mg/kg i.v. dipyridamole, ischemic flow was maintained in the face of a 20-30% reduction in blood pressure. In this setting, nonischemic flow was unchanged during TNG and doubled after dipyridamole. With the addition of methoxamine in both dilator groups, blood pressure returned to base line while flow to ischemic areas increased above base-line values (TNG, 0.16-0.20 ml/min per g, P less than 0.01; dipyridamole, 0.18-0.31 ml/min per g, P less than 0.05). Epicardial ST segment elevations increased during TNG infusion and were unchanged after dipyridamole, but with addition of methoxamine, ST segments became less elevated in both drug groups, concomitant with the observed increase in collateral blood flow. These data indicate that both types of coronary vasodilators, when used in conjunction with methoxamine to support blood pressure, reduce collateral resistance, increase collateral flow, and reduce epicardial ST-segment elevations. PMID:825534

  14. Blood flow measurement using a highly filled carbon polymer sandwich sensor and an elasto-pseudo compressible vascular flow.

    PubMed

    Mehdian, M; Rahnejat, H

    1996-01-01

    Vascular grafts are widely employed in clinical practice and still pose significant problems of compatibility and longevity, particularly when the prosthesis is to replace arteries of small diameter. Once a graft has been implanted in the vascular tree, there is no easy way of assessing its interactions with the surrounding tissue. Doppler flow probes or some imaging techniques are commonly used to monitor flow velocity in vascular prostheses. It is, however, difficult to monitor a patient's recovery on a continuous basis. Continuous means of measurement can be quite invaluable. This paper presents a high-carbon filled polymer (HCFP) sensor that is developed for blood flow measurement in vascular grafts. Furthermore, a computational fluid dynamics model of incompressible blood flow in elastic blood vessels is presented. PMID:9046189

  15. Nonlinear relationship between level of blood flow and skin temperature for different dynamics of temperature change.

    PubMed

    Vuksanović, Vesna; Sheppard, Lawrence William; Stefanovska, Aneta

    2008-05-15

    We present a study of the relationship between blood flow and skin temperature under different dynamics of skin-temperature-change: locally induced thermal shock and well controlled, gradual change. First, we demonstrate memory phenomena for blood flow and skin temperature under both conditions. Secondly, we point out that the "hysteresis" loops obtained are dependent on initial conditions, indicating physiological response times of more than twenty minutes. We also show that under thermal shock the level of blood flow is preserved up to some characteristic temperature limit, independently of subject.

  16. In-vivo imaging of blood flow dynamics using color Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

    2000-04-01

    Noninvasive quantitation of blood flow in the retinal micro circulation may elucidate the progression and treatment of ocular disorders including diabetic retinopathy, age-related degeneration, and glaucoma. Color Doppler optical coherence tomography was recently introduced as a technique allowing simultaneous micron-scale resolution cross-sectional imaging of tissue micro structure and blood flow in the human retina. Here, time-resolved imaging of dynamics of blood flow profiles was performed to measure cardiac pulsatility within retinal vessels. Retinal pulsatility has been shown to decrease throughout the progression of diabetic retinopathy.

  17. Effect of tap-water iontophoresis on sweat gland recruitment, skin temperature and skin blood flow.

    PubMed

    Kolkhorst, Fred W; DiPasquale, Dana M; Buono, Michael J

    2002-02-01

    Our interest was to quantify the role of sweat gland activation on the maintenance of skin temperature during mild exercise in the heat. Seven days of tap-water iontophoresis decreased the number of active sweat glands by 72% which significantly increased forearm skin temperature and blood flow during mild exercise (70 W) in the heat (32 degrees C). Skin temperature of the treated forearm was 0.5 degrees C warmer (P=0.049); skin blood flow in the treated forearm was 13% higher than the control arm (P=0.021). These results illustrate the importance of sweat evaporation on skin temperature and blood flow during exercise.

  18. Quantitative values of blood flow through the human forearm, hand, and finger as functions of temperature

    NASA Technical Reports Server (NTRS)

    Montgomery, L. D.

    1974-01-01

    A literature search was made to obtain values of human forearm, hand and finger blood flow as functions of environmental temperature. The sources used include both government and laboratory reports and the research presented in the open literature. An attempt was made to review many of the more quantitative noninvasive determinations and to collate the results in such a way as to yield blood flow values for each body segment as continuous functions of temperature. A brief review of the various ways used to measure blood flow is included along with an abstract of each work from which data was taken.

  19. Quantifying blood flow and wall shear stresses in the outflow tract of chick embryonic hearts

    PubMed Central

    Liu, Aiping; Nickerson, Andrew; Troyer, Aaron; Yin, Xin; Cary, Robert; Thornburg, Kent; Wang, Ruikang; Rugonyi, Sandra

    2011-01-01

    Wall shear stresses (WSS) exerted by blood flow on cardiac tissues modulate growth and development of the heart. To study the role of hemodynamic conditions on cardiac morphogenesis, here, we present a methodology that combines imaging and finite element modeling to quantify the in vivo blood flow dynamics and WSS in the cardiac outflow tract (OFT) of early chicken embryos (day 3 out of 21-day incubation period). We found a distinct blood flow field and heterogeneous distribution of WSS in the chicken embryonic heart OFT, which have physiological implications for OFT morphogenesis. PMID:21572557

  20. Numerical methods for simulating blood flow at macro, micro, and multi scales.

    PubMed

    Imai, Yohsuke; Omori, Toshihiro; Shimogonya, Yuji; Yamaguchi, Takami; Ishikawa, Takuji

    2016-07-26

    In the past decade, numerical methods for the computational biomechanics of blood flow have progressed to overcome difficulties in diverse applications from cellular to organ scales. Such numerical methods may be classified by the type of computational mesh used for the fluid domain, into fixed mesh methods, moving mesh (boundary-fitted mesh) methods, and mesh-free methods. The type of computational mesh used is closely related to the characteristics of each method. We herein provide an overview of numerical methods recently used to simulate blood flow at macro and micro scales, with a focus on computational meshes. We also discuss recent progress in the multi-scale modeling of blood flow.

  1. Effect of tap-water iontophoresis on sweat gland recruitment, skin temperature and skin blood flow.

    PubMed

    Kolkhorst, Fred W; DiPasquale, Dana M; Buono, Michael J

    2002-02-01

    Our interest was to quantify the role of sweat gland activation on the maintenance of skin temperature during mild exercise in the heat. Seven days of tap-water iontophoresis decreased the number of active sweat glands by 72% which significantly increased forearm skin temperature and blood flow during mild exercise (70 W) in the heat (32 degrees C). Skin temperature of the treated forearm was 0.5 degrees C warmer (P=0.049); skin blood flow in the treated forearm was 13% higher than the control arm (P=0.021). These results illustrate the importance of sweat evaporation on skin temperature and blood flow during exercise. PMID:11858947

  2. Blood flow characteristics in the ascending aorta after TAVI compared to surgical aortic valve replacement.

    PubMed

    Trauzeddel, Ralf Felix; Löbe, Ulrike; Barker, Alex J; Gelsinger, Carmen; Butter, Christian; Markl, Michael; Schulz-Menger, Jeanette; von Knobelsdorff-Brenkenhoff, Florian

    2016-03-01

    Ascending aortic blood flow characteristics are altered after aortic valve surgery, but the effect of transcatheter aortic valve implantation (TAVI) is unknown. Abnormal flow may be associated with aortic and cardiac remodeling. We analyzed blood flow characteristics in the ascending aorta after TAVI in comparison to conventional stented aortic bioprostheses (AVR) and healthy subjects using time-resolved three-dimensional flow-sensitive cardiovascular magnetic resonance imaging (4D-flow MRI). Seventeen patients with TAVI (Edwards Sapien XT), 12 with AVR and 9 healthy controls underwent 4D-flow MRI of the ascending aorta. Target parameters were: severity of vortical and helical flow pattern (semiquantitative grading from 0 = none to 3 = severe) and the local distribution of systolic wall shear stress (WSSsystole). AVR revealed significantly more extensive vortical and helical flow pattern than TAVI (p = 0.042 and p = 0.002) and controls (p < 0.001 and p = 0.001). TAVI showed significantly more extensive vortical flow than controls (p < 0.001). Both TAVI and AVR revealed marked blood flow eccentricity (64.7 and 66.7%, respectively), whereas controls showed central blood flow (88.9%). TAVI and AVR exhibited an asymmetric distribution of WSSsystole in the mid-ascending aorta with local maxima at the right anterior aortic wall and local minima at the left posterior wall. In contrast, controls showed a symmetric distribution of WSSsystole along the aortic circumference. Blood flow was significantly altered in the ascending aorta after TAVI and AVR. Changes were similar regarding WSSsystole distribution, while TAVI resulted in less helical and vortical blood flow. PMID:26493195

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

    PubMed

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

    2014-01-15

    The purpose of this study was to investigate blood flow and its heterogeneity within and among the knee muscles in five young (26 ± 6 years) and five old (77 ± 6 years) healthy men with similar levels of physical activity while they performed two types of submaximal fatiguing isometric contraction that required either force or position control. Positron emission tomography (PET) and [(15)O]-H2O were used to determine blood flow at 2 min (beginning) and 12 min (end) after the start of the tasks. Young and old men had similar maximal forces and endurance times for the fatiguing tasks. Although muscle volumes were lower in the older subjects, total muscle blood flow was similar in both groups (young men: 25.8 ± 12.6 ml min(-1); old men: 25.1 ± 15.4 ml min(-1); age main effect, P = 0.77) as blood flow per unit mass of muscle in the exercising knee extensors was greater in the older (12.5 ± 6.2 ml min(-1) (100 g)(-1)) than the younger (8.6 ± 3.6 ml min(-1) (100 g)(-1)) men (age main effect, P = 0.001). Further, blood flow heterogeneity in the exercising knee extensors was significantly lower in the older (56 ± 27%) than the younger (67 ± 34%) men. Together, these data show that although skeletal muscles are smaller in older subjects, based on the intact neural drive to the muscle and the greater, less heterogeneous blood flow per gram of muscle, old fit muscle achieves adequate exercise hyperaemia.

  4. GPU-Based Parallelized Solver for Large Scale Vascular Blood Flow Modeling and Simulations.

    PubMed

    Santhanam, Anand P; Neylon, John; Eldredge, Jeff; Teran, Joseph; Dutson, Erik; Benharash, Peyman

    2016-01-01

    Cardio-vascular blood flow simulations are essential in understanding the blood flow behavior during normal and disease conditions. To date, such blood flow simulations have only been done at a macro scale level due to computational limitations. In this paper, we present a GPU based large scale solver that enables modeling the flow even in the smallest arteries. A mechanical equivalent of the circuit based flow modeling system is first developed to employ the GPU computing framework. Numerical studies were employed using a set of 10 million connected vascular elements. Run-time flow analysis were performed to simulate vascular blockages, as well as arterial cut-off. Our results showed that we can achieve ~100 FPS using a GTX 680m and ~40 FPS using a Tegra K1 computing platform. PMID:27046603

  5. Measurement of real pulsatile blood flow using X-ray PIV technique with CO2 microbubbles

    PubMed Central

    Park, Hanwook; Yeom, Eunseop; Seo, Seung-Jun; Lim, Jae-Hong; Lee, Sang-Joon

    2015-01-01

    Synchrotron X-ray imaging technique has been used to investigate biofluid flows in a non-destructive manner. This study aims to investigate the feasibility of the X-ray PIV technique with CO2 microbubbles as flow tracer for measurement of pulsatile blood flows under in vivo conditions. The traceability of CO2 microbubbles in a pulsatile flow was demonstrated through in vitro experiment. A rat extracorporeal bypass loop was used by connecting a tube between the abdominal aorta and jugular vein of a rat to obtain hemodynamic information of actual pulsatile blood flows without changing the hemorheological properties. The decrease in image contrast of the surrounding tissue was also investigated for in vivo applications of the proposed technique. This technique could be used to accurately measure whole velocity field information of real pulsatile blood flows and has strong potential for hemodynamic diagnosis of cardiovascular diseases. PMID:25744850

  6. Regulation of Increased Blood Flow (Hyperemia) to Muscles During Exercise: A Hierarchy of Competing Physiological Needs

    PubMed Central

    Joyner, Michael J.; Casey, Darren P.

    2015-01-01

    This review focuses on how blood flow to contracting skeletal muscles is regulated during exercise in humans. The idea is that blood flow to the contracting muscles links oxygen in the atmosphere with the contracting muscles where it is consumed. In this context, we take a top down approach and review the basics of oxygen consumption at rest and during exercise in humans, how these values change with training, and the systemic hemodynamic adaptations that support them. We highlight the very high muscle blood flow responses to exercise discovered in the 1980s. We also discuss the vasodilating factors in the contracting muscles responsible for these very high flows. Finally, the competition between demand for blood flow by contracting muscles and maximum systemic cardiac output is discussed as a potential challenge to blood pressure regulation during heavy large muscle mass or whole body exercise in humans. At this time, no one dominant dilator mechanism accounts for exercise hyperemia. Additionally, complex interactions between the sympathetic nervous system and the microcirculation facilitate high levels of systemic oxygen extraction and permit just enough sympathetic control of blood flow to contracting muscles to regulate blood pressure during large muscle mass exercise in humans. PMID:25834232

  7. Effects of cord compression on fetal blood flow distribution and O/sub 2/ delivery

    SciTech Connect

    Itskovitz, J.; LaGamma, E.F.; Rudolph, A.M.

    1987-01-01

    The authors used the radionuclide microsphere technique in nine fetal lambs to examine the effect of partial cord compression on distribution of cardiac output and O/sub 2/ delivery to fetal organs and venous flow patterns. With a 50% reduction in umbilical blood flow the fraction of fetal cardiac output distributed to the brain, heart, carcass, kidneys, and gastrointestinal tract increased. Pulmonary blood flow fell. O/sub 2/ delivery to the brain and myocardium was maintained but was reduced to peripheral, renal, and gastrointestinal circulations. Hepatic blood flow decreased and O/sub 2/ delivery fell by 75%. The proportion of umbilical venous blood passing through the ductus venosus increased from 43.9 to 71.8%. The preferential distribution of ductus venosus blood flow through the foramen ovale was enhanced and the proportion of O/sub 2/ delivery to upper body organs derived from the ductus venosus increased. Abdominal inferior vena caval blood flow increased, and it was also preferentially distributed through the foramen ovale and constituted the major fraction of the arterial blood supply to the upper body organs. Thus cord compression modified the distribution of cardiac output and the patterns of venous returns in the fetus. This pattern of circulatory response differs from that observed with other causes of reduced O/sub 2/ delivery.

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

    PubMed Central

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

    2012-01-01

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

  9. Acute effects of Helicobacter pylori extracts on gastric mucosal blood flow in the mouse

    PubMed Central

    Henriksnäs, Johanna; Atuma, Christer; Phillipson, Mia; Sandler, Stellan; Engstrand, Lars; Holm, Lena

    2009-01-01

    AIM: To investigate the mechanisms underlying the reduction in gastric blood flow induced by a luminal water extract of Helicobacter pylori (HPE). METHODS: The stomachs of isoflurane-anesthetized mice were exteriorized, and the mucosal surface exposed. Blood flow was measured with the laser-Doppler technique, and systemic arterial blood pressure monitored. C57BL/6 mice were exposed to water extract produced from H pylori strain 88-23. To investigate the role of a nerve- or iNOS-mediated pathway, we used intraluminal lidocaine and iNOS-/- mice. Blood flow response to the endogenous nitric oxide synthase inhibitor asymmetric dimethyl arginine (ADMA) was also assessed. RESULTS: In wild-type mice, HPE decreased mucosal blood flow by approximately 30%. This reduction was abolished in iNOS-deficient mice, and by pre-treatment with lidocaine. Luminally applied ADMA resulted in reduction in blood flow similar to that observed in wild-type mice exposed to HPE. CONCLUSION: A H pylori water extract reduces gastric mucosal blood flow acutely through iNOS- and nerve-mediated pathways. PMID:19132773

  10. Investigation of Blood Flow and the Effect of Vasoactive Substances in Cutaneous Blood Vessels of "Xenopus Laevis"

    ERIC Educational Resources Information Center

    Škorjanc, Aleš; Belušic, Gregor

    2015-01-01

    In the present study, a preparation of frog skin was presented, which can be used to demonstrate the basic concepts of blood flow regulation in a very clear and attractive way to high school and university students. In a freshly euthanized "Xenopus," a patch of abdominal skin was exposed from the internal side and viewed with a USB…

  11. Analysis of Blood Flow in a Partially Blocked Bifurcated Blood Vessel

    NASA Astrophysics Data System (ADS)

    Abdul-Razzak, Hayder; Elkassabgi, Yousri; Punati, Pavan K.; Nasser, Naseer

    2009-09-01

    Coronary artery disease is a major cause of death in the United States. It is the narrowing of the lumens of the coronary blood vessel by a gradual build-up of fatty material, atheroma, which leads to the heart muscle not receiving enough blood. This my ocardial ischemia can cause angina, a heart attack, heart failure as well as sudden cardiac death [9]. In this project a solid model of bifurcated blood vessel with an asymmetric stenosis is developed using GAMBIT and imported into FLUENT for analysis. In FLUENT, pressure and velocity distributions in the blood vessel are studied under different conditions, where the size and position of the blockage in the blood vessel are varied. The location and size of the blockage in the blood vessel are correlated with the pressures and velocities distributions. Results show that such correlation may be used to predict the size and location of the blockage.

  12. Measurement of cerebral blood flow rate and its relationship with brain function using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Wang, Yi; Zhao, Yuqian; Dou, Shidan; Ma, Yushu; Ma, Zhenhe

    2016-03-01

    Activity of brain neurons will lead to changes in local blood flow rate (BFR). Thus, it is important to measure the local BFR of cerebral cortex on research of neuron activity in vivo, such as rehabilitation evaluation after stroke, etc. Currently, laser Doppler flowmetry is commonly used for blood flow measurement, however, relatively low resolution limits its application. Optical coherence tomography (OCT) is a powerful noninvasive 3D imaging modality with high temporal and spatial resolutions. Furthermore, OCT can provide flow distribution image by calculating Doppler frequency shift which makes it possible for blood flow rate measurement. In this paper, we applied OCT to measure the blood flow rate of the primary motor cortex in rats. The animal was immobilized and anesthetized with isoflurane, an incision was made along the sagittal suture, and bone was exposed. A skull window was opened on the primary motor cortex. Then, blood flow rate changes in the primary motor cortex were monitored by our homemade spectral domain OCT with a stimulation of the passive movement of the front legs. Finally, we established the relationship between blood flow rate and the test design. The aim is to demonstrate the potential of OCT in the evaluation of cerebral cortex function.

  13. In-vitro study on haemodiluted blood flow in a sinusoidal microstenosis.

    PubMed

    Kang, M J; Ji, H-S; Lee, S J

    2010-01-01

    In-vitro experiments were carried out to investigate the haemodynamic and haemorheological behaviours of haemodiluted blood flow through a microstenosis using a micro-particle image velocimetry (PIV) technique. The micro-PIV system employed in this study consisted of a two-head neodymium:yttrium-aluminium-garnet (Nd:YAG) laser, a cooled charge-coupled device camera, and a delay generator. To simulate blood flow in a stenosed vascular vessel, a polydimethylsiloxane (PDMS) microchannel with a sinusoidal throat of 80 per cent severity was employed. The width and depth of the microchannel were 100 microm and 50 microm, respectively. To compare the flow characteristics in the microstenosis, the same experiments were repeated in a straight microchannel under the same flow conditions. Using a syringe pump, human blood with 5 per cent haematocrit was supplied into the microstenosis channel. The flow characteristics and transport of blood cells through the microstenosis were investigated with various flowrates. The mean velocity fields were nearly symmetric with respect to the channel centreline. In the contraction section, the oncoming blood flow was accelerated rapidly, and the maximum velocity at the throat was almost 4.99 times faster than that of the straight microchannel without stenosis. In the diffusion section, the blood cells show rolling, deformation, twisting, and tumbling motion due to the flow-choking characteristics at the stenotic region. The results from this study will provide useful basic data for comparison with those obtained by clinical researchers. PMID:20225454

  14. Estimation of Skin Blood Flow Artefacts in NIRS Signals During a Verbal Fluency Task.

    PubMed

    Seiyama, Akitoshi; Higaki, Kotona; Takeuchi, Nao; Uehara, Masahiro; Takayama, Naoko

    2016-01-01

    The aim of this study was to clarify effects of skin (scalp) blood flow on functional near infrared spectroscopy (fNIRS) during a verbal fluency task. In the present study, to estimate the influence of skin blood flow on fNIRS signals, we conducted examinations on 19 healthy volunteers (39.9±13.1 years, 11 male and 8 female subjects). We simultaneously measured the fNIRS signals, skin blood flow (i.e., flow, velocity, and number of red blood cells [RBC]), and pulse wave rates using a multimodal fNIRS system. We found that the effects of skin blood flow, measured by the degree of interference of the flow, velocity, and number of RBCs, and pulse wave rates, on NIRS signals varied considerably across subjects. Further, by using the above physiological parameters, we evaluated application of the independent component analysis algorithm proposed by Molgedey and Schuster (MS-ICA) to remove skin blood flow artefacts from fNIRS signals.

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

    SciTech Connect

    Brusino, F.G.; Reves, J.G.; Smith, L.R.; Prough, D.S.; Stump, D.A.; McIntyre, R.W.

    1989-04-01

    Cerebral blood flow was measured in 20 patients by xenon 133 clearance methodology during nonpulsatile hypothermic cardiopulmonary bypass to determine the effect of age on regional cerebral blood flow during these conditions. Measurements of cerebral blood flow at varying perfusion pressures were made in patients arbitrarily divided into two age groups at nearly identical nasopharyngeal temperature, hematocrit value, and carbon dioxide tension and with equal cardiopulmonary bypass flows of 1.6 L/min/m2. The range of mean arterial pressure was 30 to 110 mm Hg for group I (less than or equal to 50 years of age) and 20 to 90 mm Hg for group II (greater than or equal to 65 years of age). There was no significant difference (p = 0.32) between the mean arterial pressure in group I (54 +/- 28 mm Hg) and that in group II (43 +/- 21 mm Hg). The range of cerebral blood flow was 14.8 to 29.2 ml/100 gm/min for group I and 13.8 to 37.5 ml/100 gm/min for group II. There was no significant difference (p = 0.37) between the mean cerebral blood flow in group I (21.5 +/- 4.6 ml/100 gm/min) and group II (24.3 +/- 8.1 ml/100 gm/min). There was a poor correlation between mean arterial pressure and cerebral blood flow in both groups: group I, r = 0.16 (p = 0.67); group II, r = 0.5 (p = 0.12). In 12 patients, a second cerebral blood