Perceived vessel lumen and cell-blood velocity ratio: impact on in vivo blood flow rate determination

1992 ◽  
Vol 262 (4) ◽  
pp. H1156-H1163 ◽  
Author(s):  
G. R. Cokelet ◽  
I. H. Sarelius
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Average Velocity ◽  
Velocity Ratio ◽  
Blood Flow Rate ◽  
Mass Conservation ◽  
Red Cell ◽  
Vessel Lumen ◽  
Image Width

Microscopic images of blood flow through individual capillary segments and divergent capillary bifurcations in cremaster muscle of golden hamster were videotaped, and the data from the videotapes (projected vessel image width and individual red cell velocities) were used in two ways to evaluate blood flow rate. The first method assumes 1) that the vessel lumen is circular with a diameter equal to the projected image width and 2) that the blood average velocity is proportional to the average red cell velocity. The second method makes neither of these assumptions but relies only on the principle of mass conservation. It is demonstrated that the two assumptions of the first method can lead to significant errors in hemodynamic relationships deduced from in vivo data. Although the second method cannot independently give absolute values of average velocity at one vessel location, it can give absolute values of the ratio of blood flow rates through two (or more) vascular lumina.

scholarly journals Patient-specific computational haemodynamics associated with surgical creation of an arteriovenous fistula

2021 ◽  
Author(s):  
George Hyde-Linaker ◽  
Pauline Hall Barrientos ◽  
Sokratis Stoumpos ◽  
Asimina Kazakidi
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Disease Patient ◽  
Blood Flow Rate ◽  
Fold Increase ◽  
Transitional Flow ◽  
Patient Specific ◽  
Venous Anastomosis ◽  
End Stage

Abstract Despite arteriovenous fistulae (AVF) being the preferred vascular access for haemodialysis, high primary failure rates (30-70%) and low one-year patency rates (40-70%) hamper their use. The haemodynamics within the vessels of the fistula change significantly following surgical creation of the anastomosis and can be a surrogate of AVF success or failure. Computational fluid dynamics (CFD) can crucially predict AVF outcomes through robust analysis of a fistula’s haemodynamic patterns, which is impractical in-vivo. We present a proof-of-concept CFD framework for characterising the AVF blood flow prior and following surgical creation of a successful left radiocephalic AVF in a 20-year-old end-stage kidney disease patient. The reconstructed vasculature was generated utilising multiple contrast-enhanced magnetic resonance imaging (MRI) datasets. Large eddy simulations were conducted for establishing the extent of arterial and venous remodelling. Following anastomosis creation, a significant 2-3-fold increase in blood flow rate was induced downstream of the left subclavian artery. This was validated through comparison with post-AVF patient-specific phase-contrast data. The increased flow rate yielded an increase in time-averaged wall shear stress (TAWSS), a key marker of adaptive vascular remodelling. We have demonstrated TAWSS and oscillatory shear distributions of the transitional-flow in the venous anastomosis are predictive of AVF remodelling.

Blood flow rate and cellular influx of glucose and arginine in mouse liver in vivo

1980 ◽  
Vol 238 (4) ◽  
pp. H553-H560
Author(s):  
E. M. Cornford ◽  
L. D. Braun ◽  
W. M. Pardridge ◽  
W. H. Oldendorf
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Mouse Liver ◽  
Blood Flow Rate

scholarly journals Computational Fluid Dynamics-Based Estimation of Blood Flow Rate in Doppler Analysis: In Vivo Validation by Means of Phase Contrast Magnetic Resonance Imaging

2009 ◽  
Author(s):  
Raffaele Ponzini ◽  
Christian Vergara ◽  
Giovanna Rizzo ◽  
Alessandro Veneziani ◽  
Alberto Redaelli ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Flow Rate ◽  
Ad Hoc ◽  
A Priori ◽  
Maximum Velocity ◽  
Blood Flow Rate ◽  
In Vivo Validation

In this work we carry out an in vivo validation of a method for estimating blood flow rate from the peak velocity, as it is usually done in single-wire Doppler catheter measurements. This method, originally proposed in [1] stems from the application of numerical analysis of the blood flow with Computational Fluid Dynamics (CFD) techniques. It proposes a new formula linking the maximum velocity and the flow rate, which, however, has the same practical cost of classical approaches based on a priori assumptions on the velocity profile. After the first clinical observations indicating the improved accuracy in flow rate estimates introduced by the new method discussed in [2, 3], in this paper we present an ad hoc in vivo validation, as firstly suggested in [4], still confirming the reliability of the new approach.

Womersley Number-Based Estimates of Blood Flow Rate in Doppler Analysis: In Vivo Validation by Means of Phase-Contrast MRI

2010 ◽  
Vol 57 (7) ◽  
pp. 1807-1815 ◽  
Author(s):  
Raffaele Ponzini ◽  
Christian Vergara ◽  
Giovanna Rizzo ◽  
Alessandro Veneziani ◽  
Alberto Roghi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Phase Contrast ◽  
Blood Flow Rate ◽  
Womersley Number ◽  
Phase Contrast Mri ◽  
Doppler Analysis ◽  
In Vivo Validation

Effects of NO-Donors on Thrombus Formation and Microcirculation in Cerebral Vessels of the Rat

1996 ◽  
Vol 76 (01) ◽  
pp. 111-117 ◽  
Author(s):  
Yasuto Sasaki ◽  
Junji Seki ◽  
John C Giddings ◽  
Junichiro Yamamoto
Keyword(s):  
Blood Flow ◽  
Thrombus Formation ◽  
Dependent Manner ◽  
Red Cell ◽  
Cell Velocity ◽  
Red Cell Velocity ◽  
The Mean ◽  
Wall Shear ◽  
Dose Dependent

SummarySodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), are known to liberate nitric oxide (NO). In this study the effects of SNP and SIN-1 on thrombus formation in rat cerebral arterioles and venules in vivo were assessed using a helium-neon (He-Ne) laser. SNP infused at doses from 10 Μg/kg/h significantly inhibited thrombus formation in a dose dependent manner. This inhibition of thrombus formation was suppressed by methylene blue. SIN-1 at a dose of 100 Μg/kg/h also demonstrated a significant antithrombotic effect. Moreover, treatment with SNP increased vessel diameter in a dose dependent manner and enhanced the mean red cell velocity measured with a fiber-optic laser-Doppler anemometer microscope (FLDAM). Blood flow, calculated from the mean red cell velocity and vessel diameters was increased significantly during infusion. In contrast, mean wall shear rates in the arterioles and venules were not changed by SNP infusion. The results indicated that SNP and SIN-1 possessed potent antithrombotic activities, whilst SNP increased cerebral blood flow without changing wall shear rate. The findings suggest that the NO released by SNP and SIN-1 may be beneficial for the treatment and protection of cerebral infarction

The Effect of Furosemide on the Intrarenal Blood Flow Distribution in the Dog

1972 ◽  
Vol 50 (8) ◽  
pp. 774-783 ◽  
Author(s):  
Serge Carrière ◽  
Michel Desrosiers ◽  
Jacques Friborg ◽  
Michèle Gagnan Brunette
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Urine Volume ◽  
Flow Distribution ◽  
Blood Flow Rate ◽  
Initial Distribution ◽  
Blood Flow Distribution ◽  
Intrarenal Blood Flow ◽  
Femoral Blood ◽  
Furosemide Administration

Furosemide (40 μg/min) was perfused directly into the renal artery of dogs in whom the femoral blood pressure was reduced (80 mm Hg) by aortic clamping above the renal arteries. This maneuver, which does not influence the intrarenal blood flow distribution, produced significant decreases of the urine volume, natriuresis, Ccreat, and CPAH, and prevented the marked diuresis normally produced by furosemide. Therefore the chances that systemic physiological changes occurred, secondary to large fluid movements, were minimized. In those conditions, however, furosemide produced a significant increase of the urine output and sodium excretion in the experimental kidney whereas Ccreat and CPAH were not affected. The outer cortical blood flow rate (ml/100 g-min) was modified neither by aortic constriction (562 ± 68 versus 569 ± 83) nor by the subsequent administration of furosemide (424 ± 70). The blood flow rate of the outer medulla in these three conditions remained unchanged (147 ± 52 versus 171 ± 44 versus 159 ± 54). The initial distribution of the radioactivity in each compartment remained comparable in the three conditions. In parallel with the results from the krypton-85 disappearance curves, the autoradiograms, silicone rubber casts, and EPAH did not suggest any change in the renal blood flow distribution secondary to furosemide administration.

The Effect of Hematocrit on the Clearance of Small Molecules during Hemodialysis

1983 ◽  
Vol 6 (3) ◽  
pp. 127-130 ◽  
Author(s):  
C. Woffindin ◽  
N.A. Hoenich ◽  
D.N.S. Kerr
Keyword(s):  
Blood Flow ◽  
Regression Analysis ◽  
Small Molecules ◽  
Flat Plate ◽  
Flow Rate ◽  
Distribution Curve ◽  
Blood Flow Rate ◽  
Hollow Fibre ◽  
Urea Clearance ◽  
Flow Rates

Data collected during the evaluation of a series of hemodialysers were analysed to see the effect of hematocrit on the clearance of urea and creatinine. All evaluations were performed on patients with a range of hematocrits with a mean close to 20%. The urea clearance of those in the upper half of the distribution curve (mean hematocrit 29.4%) was not significantly different from that of patients in the lower half of the distribution curve (mean hematocrit 16.9%) whether the clearance was studied at high or low blood flow rates and with hollow fibre or flat plate disposable hemodialysers. Likewise, there was no correlation between hematocrit and urea clearance by regression analysis. In contrast, the clearance of creatinine was affected by hematocrit being greater at lower hematocrit values. This difference was independent of blood flow rate and dialyser type and was confirmed by regression analysis.

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