Blood flow and blood velocity measurementin vivo by electromagnetic induction

1984 ◽  
Vol 22 (3) ◽  
pp. 193-211 ◽  
Author(s):  
D. G. Wyatt
Keyword(s):  
Blood Flow ◽  
Electromagnetic Induction ◽  
Blood Velocity

Vasodilation contributes to the rapid hyperemia with rhythmic contractions in humans

1998 ◽  
Vol 76 (4) ◽  
pp. 418-427 ◽  
Author(s):  
J K Shoemaker ◽  
M E Tschakovsky ◽  
R L Hughson
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Perfusion Pressure ◽  
Blood Velocity ◽  
Pulsed Doppler ◽  
Contraction Rate ◽  
Handgrip Exercise ◽  
Arterial Diameter ◽  
Exercise Tests ◽  
Rhythmic Contractions

The hypothesis that the rapid increases in blood flow at the exercise onsetare exclusively due to the mechanical effects of the muscle pump was tested in six volunteersduring dynamic handgrip exercise. While supine, each subject completed a series of eightdifferent exercise tests in which brachial artery blood pressure (BP) was altered by25–30 mmHg (1 mmHg = 133.3 Pa) by positioning the arm above or below the heart.Two different weights, corresponding to 4.9 and 9.7% of maximal voluntary isometriccontraction, were raised and lowered at two different contraction rate schedules (1s:1s and 2s:2swork–rest) each with a 50% duty cycle. Beat-by-beat measures of mean blood velocity (MBV)(pulsed Doppler) were obtained at rest and for 5 min following step increases in work ratewith emphasis on the first 24 s. MBV was increased 50–100% above rest following the firstcontraction in both arm positions (p < 0.05). The increase in MBV from rest was greaterin the below position compared with above, and this effect was observed following the first andsubsequent contractions (p < 0.05). However, the positional effect on the increase inMBV could not be explained entirely by the ~40% greater BP in this position. Also, the greaterworkload resulted in greater increases in MBV as early as the first contraction, compared withthe light workload (p < 0.05) despite similar reductions in forearm volume followingsingle contractions. MBV was greater with faster contraction rate tests by 8 s of exercise. Itwas concluded that microvascular vasodilation must act in concert with a reduction in venouspressure to increase forearm blood flow within the initial 2–4 s of exercise.Key words: Doppler, mean blood velocity, arterial diameter,handgrip exercise, perfusion pressure.

The effect of I.V. L-NG Methylarginine Hydrochloride (L-NMMA: 546C88) on Basal and Acetazolamide (Diamox®) induced Changes of Blood Velocity in Cerebral Arteries and Regional Cerebral Blood flow in Man

Cephalalgia ◽  
2005 ◽  
Vol 25 (5) ◽  
pp. 344-352 ◽  
Author(s):  
LH Lassen ◽  
B Sperling ◽  
AR Andersen ◽  
J Olesen
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Regional Cerebral Blood Flow ◽  
Cerebral Arteries ◽  
Blood Velocity ◽  
Percentage Increase ◽  
Regional Cerebral Blood ◽  
Cerebral Arterioles ◽  
Induced Changes ◽  
Oxide Synthase

The aim of this study was to estimate the effect of Nitric Oxide synthase (NOS)-inhibition (L-NMMA) on the diameter of the middle cerebral artery (MCA) and on regional cerebral blood flow (rCBF). Furthermore, to assess the effect of L-NMMA on acetazolamide induced increases in MCA blood velocity (Vmean) and rCBF. In an open crossover design 12 healthy subjects attended the laboratory twice. The first day 6 mg/kg L-LNMMA i.v. over 15 min preceded 1 g acetazolamide iv over 5 min. Eight days later only acetazolamide was given. Vmean in MCA was determined with transcranial Doppler (TCD) and rCBF with Xe-133 inhalation SPECT at baseline, after L-NMMA and 25 and 55 min after acetazolamide infusion. After L-NMMA the decrease in rCBFMCA was 6.8% (± 7.4) ( P < 0.019, n = 12), whereas Vmean was not affected ( P = 0.83, n = 8). The change in MCA diameter was estimated to -1.3% ( P = 0.44, n = 8). L-NMMA did not affect acetazolamide increases in Vmean ( P = 0.67, n = 8) nor rCBF ( P = 0.29, n = 12). The percentage increase of Vmean was 1.5 times that of rCBF ( n = 8). Our data suggest that the basal tone of human cerebral arterioles but not of conduit arteries is NO-dependent. The action of acetazolamide in man is not NO-dependent.

Abstract 032: Uninterrupted Sitting Induces Unfavorable Changes In Resting Hemodynamics And Inflammatory And Vascular Biomarkers In Physically Inactive And Active Adults

Circulation ◽  
2021 ◽  
Vol 143 (Suppl_1) ◽  
Author(s):  
Megan C Nelson ◽  
Madeline P Casanova ◽  
Jennavere R Ball ◽  
Rachel D Midence ◽  
Timothy R Johnson ◽  
...  
Keyword(s):  
Physical Activity ◽  
Blood Flow ◽  
Mean Arterial Pressure ◽  
Shear Rate ◽  
Arterial Pressure ◽  
Vascular Function ◽  
Blood Velocity ◽  
Inflammatory Biomarkers ◽  
Active Adults ◽  
Over Time

Introduction: A single bout of uninterrupted sitting impairs vascular function in the legs, which may be due to reductions in blood flow and shear stress. Participating in regular moderate-to-vigorous physical activity (MVPA) has been identified as an effective approach for improving vascular function, and recent evidence suggests meeting the physical activity (PA) guidelines may attenuate some of the negative health outcomes associated with excessive sedentary behavior; however, it is not well understood how meeting the PA guidelines may influence the acute response to sitting. Our aim was to investigate the effects of 3 h of uninterrupted sitting on hemodynamics and vascular and inflammatory biomarkers in physically inactive and active adults. Hypothesis: We hypothesized active adults would experience less detrimental physiological changes after sitting compared to inactive adults. Methods: Eleven inactive (mean±SD, age: 47.1±8.9 y, body fat: 33.1±8.5%; 78.5% women) and 16 active adults (age: 46.1±8.9 y, body fat: 25.2±7.2%; 31.1% women) completed 3 h of uninterrupted sitting. Adults self-reported their PA with the International PA Questionnaire. Adults engaging in ≥150 min·wk -1 were classified as active and <150 min·wk -1 , inactive. Hemodynamic variables, and superficial femoral artery (SFA) diameter and blood velocity were measured each hour over 3 h of sitting. Mean arterial pressure, blood flow and shear rate were calculated. Serum vascular and inflammatory biomarkers were measured pre and post sitting. Linear mixed-effects modeling was used to assess changes in dependent variables over time and between inactive and active adults, controlling for sex. Results: Inactive and active adults self-reported 7.3±7.1 and 93.3±64.8 min·d -1 of MVPA, respectively. Endothelin-1 (baseline: 8.3±13.4 pg/mL, post: 81.1±103.0 pg/mL; p<0.001) and interleukin-6 (baseline: 0.08±0.06 pg/mL, post: 0.11±0.11 pg/mL; p=0.03) increased post sitting compared to baseline in all adults, regardless of PA status. Systolic blood pressure, mean arterial pressure, calf circumference, and SFA diameter, blood velocity, and mean blood flow decreased over time in both groups (p<0.05 for all). There was an interaction effect for mean shear rate (p=0.008); inactive adults experienced a decline over 3 h of sitting (baseline: 76.1±48.2 s -1 ; 1 h: 55.0±27.4 s -1 ; 2 h: 45.3±24.2 s -1 ; 3 h: 40.8±25.5 s -1 ) while active participants demonstrated no change (baseline: 36.6±21.4 s -1 ; 1 h: 28.1±21.4 s -1 ; 2 h: 26.1±20.9 s -1 ; 3 h: 23.8±19.5 s -1 ). Inactive adults also had a higher oscillatory shear index compared to active adults (p<0.001). Conclusion: Uninterrupted sitting induced unfavorable changes regardless of PA status; however, active adults demonstrated a more favorable shear profile. Meeting PA guidelines may attenuate some unfavorable changes within the vasculature associated with prolonged sitting.

scholarly journals Mathematical Modeling of Treatment Effect on Tumor Growth and Blood Flow through a Channel with Magnetic Field

2021 ◽  
pp. 66-79
Author(s):  
K. W. Bunonyo ◽  
C. U. Amadi
Keyword(s):  
Magnetic Field ◽  
Differential Equation ◽  
Ordinary Differential Equation ◽  
Blood Flow ◽  
Tumor Growth ◽  
Blood Velocity ◽  
Frequency Parameter ◽  
Womersley Number ◽  
Permeability Parameter ◽  
Flow Through

In this research, we investigated the effect of tumor growth on blood flow through a micro channel by formulated the governing model with the assumption that blood is an incompressible, eclectrially conducting fluid which flow is caused by the pumping action of the heart and suction. The governing model was scaled using some dimensionless variables and the region of the tumor was obtained from Dominguez [1] which was incorporated in our model. The model is further reduced to an ordinary differential equation using a perturbation condition. However, the ordinary differential equation was solved using method of undermined coefficients, and the constants coefficients obtained via matrix method. Furthermore, the simulation to study the effect of the pertinent parameters was done suing computation software called Mathematica. It is seen in our investigation that the entering parameters such as magnetic field parameter, the Reynolds number, womersley number, oscillatory frequency parameter, and permeability parameter affect the blood velocity profile in decreasing and increasing fashion.

scholarly journals Effect of Xenon-Induced Flow Activation on Xenon-Enhanced Computed Tomography Cerebral Blood Flow Calculations

1998 ◽  
Vol 18 (11) ◽  
pp. 1192-1195 ◽  
Author(s):  
Walter D. Obrist ◽  
Zihong Zhang ◽  
Howard Yonas
Keyword(s):  
Computed Tomography ◽  
Blood Flow ◽  
Blood Velocity ◽  
Time Varying ◽  
Standard Analysis ◽  
Stable Xenon ◽  
Flow Activation ◽  
Induced Flow ◽  
Minimal Bias ◽  
Enhanced Computed Tomography

Computer simulations of stable xenon (sXe) uptake curves were used to evaluate the effect of xenon-induced flow activation on CBF calculations by xenon-enhanced computed tomography, Estimates of flow activation were based on repeated transcranial Doppler measurements of blood velocity during 4,5 minutes of sXe inhalation, The synthetic curves were generated from a generalized Kety equation that included time-varying blood flow activation, In contrast to the peak 35% increase in blood flow velocity during sXe inhalation, a standard analysis of the flow-varying synthetic curves revealed only minor 3% to 5% increases in calculated CBF. It is concluded that brief xenon inhalations can provide blood flow estimates that contain minimal bias from activation.

The effect of body acceleration on the dispersion of solute in a non-Newtonian blood flow through an artery

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nur Husnina Saadun ◽  
Nurul Aini Jaafar ◽  
Md Faisal Md Basir ◽  
Ali Anqi ◽  
Mohammad Reza Safaei
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Yield Stress ◽  
Solute Concentration ◽  
Casson Fluid ◽  
Blood Velocity ◽  
Content Type ◽  
Body Acceleration ◽  
Lead Angle ◽  
Flow Through

Purpose The purpose of this study is to solve convective diffusion equation analytically by considering appropriate boundary conditions and using the Taylor-Aris method to determine the solute concentration, the effective and relative axial diffusivities. Design/methodology/approach >An analysis has been conducted on how body acceleration affects the dispersion of a solute in blood flow, which is known as a Bingham fluid, within an artery. To solve the system of differential equations analytically while validating the target boundary conditions, the blood velocity is obtained. Findings The blood velocity is impacted by the presence of body acceleration, as well as the yield stress associated with Casson fluid and as such, the process of dispersing the solute is distracted. It graphically illustrates how the blood velocity and the process of solute dispersion are affected by various factors, including the amplitude and lead angle of body acceleration, the yield stress, the gradient of pressure and the Peclet number. Originality/value It is witnessed that the blood velocity, the solute concentration and also the effective and relative axial diffusivities experience a drop when either of the amplitude, lead angle or the yield stress rises.

Timed synchronization of muscle contraction to heartbeat enhances muscle hyperemia

2020 ◽  
Vol 128 (4) ◽  
pp. 805-812
Author(s):  
Gaia Giuriato ◽  
Stephen J. Ives ◽  
Cantor Tarperi ◽  
Lorenzo Bortolan ◽  
Federico Ruzzante ◽  
...  
Keyword(s):  
Blood Flow ◽  
Muscle Contraction ◽  
Blood Velocity ◽  
Muscle Contractions ◽  
Velocity Spectrum ◽  
Functional Hyperemia ◽  
Central Hemodynamics ◽  
Active Muscle ◽  
Vascular Conductance ◽  
Significant Difference

Blood flow (BF) to exercising muscles is susceptible to variations of intensity, and duration of skeletal muscle contractions, cardiac cycle, blood velocity, and vessel dilation. During cyclic muscle activity, these elements may change proportionally with or without direct optimal temporal alignment, likely influencing BF to active muscle. Ideally, the pulsed delivery of blood to active muscle timed with the inactive phase of muscle duty-cycle would enhance the peak and average BF. To investigate the phenomenon of muscle contraction and pulse synchronicity, electrically evoked muscle contractions (trains of 20 Hz, 200-ms duration) were synchronized with each systolic phase of the anterograde blood velocity spectrum (aBVS). Specifically, unilateral quadriceps contractions matched in-phase (IP) with the aBVS were compared with contractions matched out-of-phase (OP) with the aBVS in 10 healthy participants (26 ± 3 yr). During each trial, femoral BF of the contracting limb and central hemodynamics were recorded for 5 min with an ultrasound Doppler, a plethysmograph, and a cardioimpedance device. At steady state (5th min) IP BF (454 ± 30 mL/min) and vascular conductance (4.3 ± 0.2 mL·min−1·mmHg−1), and OP MAP (108 ± 2 mmHg) were significantly lower ( P < 0.001) in comparison to OP BF (784 ± 25 mL/min) and vascular conductance (6.7 ± 0.2 mL·min−1·mmHg−1), and IP MAP (113 ± 3 mmHg). On the contrary, no significant difference (all, P > 0.05) was observed between IP and OP central hemodynamics (HR: 79 ± 10 vs. 76 ± 11 bpm, CO: 8.0 ± 1.6 vs. 7.3 ± 1.6 L/min), and ventilatory patterns (V̇e:14 ± 2 vs. 14 ± 1 L/min, V̇o2:421 ± 70 vs. 397 ± 34 mL/min). The results suggest that muscle contractions occurring during OP that do not interfere with aBVS elicit a maximization of muscle functional hyperemia. NEW & NOTEWORTHY When muscle contraction is synchronized with the pulsed delivery of blood flow to active muscle, muscle functional hyperemia can be either maximized or minimized. This suggests a possibility to couple different strategies to enhance the acute and chronic effects of exercise on the cardiovascular system.

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