Distribution of Blood Flow in the Renal Cortex during Saline Loading

1. The effect of infusion of isotonic saline on the circulation in the renal cortex in the dog was investigated by an external counting technique involving measurement of the transit times for 85Krypton and 131I-labelled albumin after rapid injection into the renal artery. 2. During saline infusion superficial renal cortical blood flow and overall cortical blood flow rose by 23 and 15%, respectively. There was a 6% rise in the ratio superficial cortical blood flow to overall cortical flow, which however, was not significant. 3. Resistance to flow through cortex decreased. 4. Mean transit time for plasma through cortex decreased from an average of 2·9 sec in the control period to 2·6 and 2·1 sec during saline infusion. 5. Renal cortical blood volume, as estimated from the cortical blood flow and the mean transit time for plasma, was virtually unchanged. 6. These studies indicate that the decrease in resistance to flow during acute isotonic saline infusion is probably caused by a dilatation of the resistance vessels only. No significant redistribution of blood flow in cortex takes place; this, however, does not exclude regional changes in glomerular filtration rate.

Download Full-text

Comparison of Renal Blood Flow and Transit Times Measured by Means of 99mTc-Labelled Erythrocytes and Indocyanine Green in Humans with Normal and Diseased Kidneys

Clinical Science ◽

10.1042/cs0510151 ◽

1976 ◽

Vol 51 (2) ◽

pp. 151-159

Author(s):

F. C. Reubi ◽

C. Vorburger ◽

Gertrud Pfeiffer ◽

S. Golder

Keyword(s):

Blood Flow ◽

Indocyanine Green ◽

Renal Blood Flow ◽

Transit Time ◽

Mean Transit Time ◽

Common Mechanism ◽

Dilution Method ◽

Appearance Time ◽

Vascular Volume ◽

Transit Times

1. In nineteen patients with normal or diseased kidneys, renal blood flow, transit times and vascular volume were determined by means of an indicator-dilution method. Two different indicators, plasma-bound Indocyanine Green (IG) and 99mTc-labelled erythrocytes, were used simultaneously. 2. Comparison of the results indicates that IG slightly overestimates renal blood flow, appearance time, mean transit time and vascular volume, as the erythrocyte/IG ratios averaged 0·972, 0·903, 0·93 and 0·921 respectively. Overestimation of the mean transit time was less apparent when it was prolonged. In patients with reduced renal function, the average blood flow values obtained with the two indicators were in good agreement. 3. It is unlikely that axial streaming of erythrocytes accounts for their shorter mean transit time, because the individual erythrocyte/IG mean transit time ratios were independent of the rate of blood flow and the peripheral packed cell volume. 4. Since the erythrocyte/IG mean transit time ratios correlated significantly with the erythrocyte/IG ratios for appearance time and renal blood flow, the common mechanism leading to a depression of all erythrocyte/IG ratios is presumably extravascular circulation and delayed recovery of a small fraction of IG.

Download Full-text

An anatomic and physiological model of hepatic vascular system

Journal of Applied Physiology ◽

10.1152/jappl.1995.79.3.1008 ◽

1995 ◽

Vol 79 (3) ◽

pp. 1008-1026 ◽

Cited By ~ 1

Author(s):

D. R. Fine ◽

D. Glasser ◽

D. Hildebrandt ◽

J. Esser ◽

R. E. Lurie ◽

...

Keyword(s):

Blood Flow ◽

Transit Time ◽

Vascular System ◽

Model Parameters ◽

Activity Time ◽

Mathematical Relationship ◽

Portal Flow ◽

Splenic Blood Flow ◽

Liver Activity ◽

Transit Times

Hepatic function can be characterized by the activity/time curves obtained by imaging the aorta, spleen, and liver. Nonparametric deconvolution of the activity/time curves is clinically useful as a diagnostic tool in determining organ transit times and flow fractions. The use of this technique is limited, however, because of numerical and noise problems in performing deconvolution. Furthermore, the interaction of part of the tracer with the spleen and gastrointestinal tract, before it enters the liver, further obscures physiological information in the deconvolved liver curve. In this paper, a mathematical relationship is derived relating the liver activity/time curve to portal and hepatic behavior. The mathematical relationship is derived by using transit time spectrum/residence time density theory. Based on this theory, it is shown that the deconvolution of liver activity/time curves gives rise to a complex combination of splenic, gastrointestinal, and liver dependencies. An anatomically and physiologically plausible parametric model of the hepatic vascular system has been developed. This model is used in conjunction with experimental data to estimate portal, splenic, and hepatic physiological blood flow parameters for eight normal volunteers. These calculated parameters, which include the portal flow fraction, the splenic blood flow fraction, and blood transit times are shown to adequately correspond to published values. In particular, the model of the hepatic vascular system identifies the portal flow fraction as 0.752 +/- 0.022, the splenic blood flow fraction as 0.180 +/- 0.023, and the liver mean transit time as 13.4 +/- 1.71 s. The model has also been applied to two portal hypertensive patients. The variation in some of the model parameters is beyond normal limits and is consistent with the observed pathology.

Download Full-text

The Effects of Changes in PaCO2Cerebral Blood Volume, Blood Flow, and Vascular Mean Transit Time

Stroke ◽

10.1161/01.str.5.5.630 ◽

1974 ◽

Vol 5 (5) ◽

pp. 630-639 ◽

Cited By ~ 782

Author(s):

ROBERT L. GRUBB ◽

MARCUS E. RAICHLE ◽

JOHN O. EICHLING ◽

MICHEL M. TER-POGOSSIAN

Keyword(s):

Blood Flow ◽

Blood Volume ◽

Transit Time ◽

Mean Transit Time ◽

Volume Blood ◽

Volume Blood Flow

Download Full-text

Aggregation in environmental systems: seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-3059-2015 ◽

2015 ◽

Vol 12 (3) ◽

pp. 3059-3103 ◽

Cited By ~ 7

Author(s):

J. W. Kirchner

Keyword(s):

Transit Time ◽

Mean Transit Time ◽

Strong Nonlinearity ◽

Isotopic Tracers ◽

Water Fraction ◽

Benchmark Tests ◽

Environmental Systems ◽

Transit Times ◽

Event Based ◽

The Relationship

Abstract. Environmental heterogeneity is ubiquitous, but environmental systems are often analyzed as if they were homogeneous instead, resulting in aggregation errors that are rarely explored and almost never quantified. Here I use simple benchmark tests to explore this general problem in one specific context: the use of seasonal cycles in chemical or isotopic tracers (such as Cl−, δ18O, or δ2H) to estimate timescales of storage in catchments. Timescales of catchment storage are typically quantified by the mean transit time, meaning the average time that elapses between parcels of water entering as precipitation and leaving again as streamflow. Longer mean transit times imply greater damping of seasonal tracer cycles. Thus, the amplitudes of tracer cycles in precipitation and streamflow are commonly used to calculate catchment mean transit times. Here I show that these calculations will typically be wrong by several hundred percent, when applied to catchments with realistic degrees of spatial heterogeneity. This aggregation bias arises from the strong nonlinearity in the relationship between tracer cycle amplitude and mean travel time. I propose an alternative storage metric, the young water fraction in streamflow, defined as the fraction of runoff with transit times of less than roughly 0.2 years. I show that this young water fraction (not to be confused with event-based "new water" in hydrograph separations) is accurately predicted by seasonal tracer cycles within a precision of a few percent, across the entire range of mean transit times from almost zero to almost infinity. Importantly, this relationship is also virtually free from aggregation error. That is, seasonal tracer cycles also accurately predict the young water fraction in runoff from highly heterogeneous mixtures of subcatchments with strongly contrasting transit time distributions. Thus, although tracer cycle amplitudes yield biased and unreliable estimates of catchment mean travel times in heterogeneous catchments, they can be used reliably to estimate the fraction of young water in runoff.

Download Full-text

Effects of graded hypotension on cerebral blood flow, blood volume, and mean transit time in dogs

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1992.262.6.h1908 ◽

1992 ◽

Vol 262 (6) ◽

pp. H1908-H1914 ◽

Cited By ~ 2

Author(s):

M. Ferrari ◽

D. A. Wilson ◽

D. F. Hanley ◽

R. J. Traystman

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Cerebral Perfusion Pressure ◽

Blood Volume ◽

Transit Time ◽

Cerebral Perfusion ◽

Pressure Range ◽

Cerebral Blood Volume ◽

Perfusion Pressure ◽

Mean Transit Time

This study tested the hypothesis that cerebral blood flow (CBF) is maintained by vasodilation, which manifests itself as a progressive increase in mean transit time (MTT) and cerebral blood volume (CBV) when cerebral perfusion pressure is reduced. Cerebral perfusion pressure was decreased in 10 pentobarbital-anesthetized dogs by controlled hemorrhage. Microsphere-determined CBF was autoregulated in all tested cerebral regions over the 40- to 130-mmHg cerebral perfusion pressure range but decreased by 50% at approximately 30 mmHg. MTT and CBV progressively and proportionately increased in the right parietal cerebral cortex over the 40- to 130-mmHg cerebral perfusion pressure range. Total hemoglobin content (Hb1), measured in the same area by an optical method, increased in parallel with the increases in CBV computed as the (CBF.MTT) product. At 30 mmHg cerebral perfusion pressure, CBV and Hb were still increased and MTT was disproportionately lengthened (690% of control). We conclude that within the autoregulatory range, CBF constancy is maintained by both increased CBV and MTT. Outside the autoregulatory range, substantial prolongation of the MTT occurs. When CBV is maximal, further reductions in cerebral perfusion pressure produce disproportionate increases in MTT that signal the loss of cerebral vascular dilatory hemodynamic reserve.

Download Full-text

Transit time dispersion in the pulmonary arterial tree

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.2.565 ◽

1998 ◽

Vol 85 (2) ◽

pp. 565-574 ◽

Cited By ~ 27

Author(s):

Anne V. Clough ◽

Steven T. Haworth ◽

Christopher C. Hanger ◽

Jerri Wang ◽

David L. Roerig ◽

...

Keyword(s):

Transit Time ◽

Mean Transit Time ◽

Arterial Tree ◽

Lung Lobe ◽

Transit Times ◽

Pulmonary Capillary ◽

Time Dispersion ◽

Pulmonary Arterial ◽

The Difference ◽

In Transit

Knowledge of the contributions of arterial and venous transit time dispersion to the pulmonary vascular transit time distribution is important for understanding lung function and for interpreting various kinds of data containing information about pulmonary function. Thus, to determine the dispersion of blood transit times occurring within the pulmonary arterial and venous trees, images of a bolus of contrast medium passing through the vasculature of pump-perfused dog lung lobes were acquired by using an X-ray microfocal angiography system. Time-absorbance curves from the lobar artery and vein and from selected locations within the intrapulmonary arterial tree were measured from the images. Overall dispersion within the lung lobe was determined from the difference in the first and second moments (mean transit time and variance, respectively) of the inlet arterial and outlet venous time-absorbance curves. Moments at selected locations within the arterial tree were also calculated and compared with those of the lobar artery curve. Transit times for the arterial pathways upstream from the smallest measured arteries (200-μm diameter) were less than ∼20% of the total lung lobe mean transit time. Transit time variance among these arterial pathways (interpathway dispersion) was less than ∼5% of the total variance imparted on the bolus as it passed through the lung lobe. On average, the dispersion that occurred along a given pathway (intrapathway dispersion) was negligible. Similar results were obtained for the venous tree. Taken together, the results suggest that most of the variation in transit time in the intrapulmonary vasculature occurs within the pulmonary capillary bed rather than in conducting arteries or veins.

Download Full-text

Brain Blood Flow and Mean Transit Time as Related to Aging

Gerontology ◽

10.1159/000212402 ◽

1980 ◽

Vol 26 (2) ◽

pp. 104-107 ◽

Cited By ~ 9

Author(s):

M. Fujishima ◽

T. Omae

Keyword(s):

Blood Flow ◽

Transit Time ◽

Mean Transit Time ◽

Brain Blood Flow

Download Full-text

Interrelationships Among Regional Cerebral Blood Flow, Mean Transit Time, Vascular Volume and Cerebral Vascular Resistance

Stroke ◽

10.1161/01.str.5.6.719 ◽

1974 ◽

Vol 5 (6) ◽

pp. 719-724 ◽

Cited By ~ 9

Author(s):

YOSHIHIRO KURIYAMA ◽

TAKASHI AOYAMA ◽

KUNIHIKO TADA ◽

SHOTARO YONEDA ◽

TADAATSU NUKADA ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Vascular Resistance ◽

Transit Time ◽

Regional Cerebral Blood Flow ◽

Mean Transit Time ◽

Regional Cerebral Blood ◽

Vascular Volume ◽

Cerebral Vascular Resistance ◽

Cerebral Vascular

Download Full-text

A Simple and Rapid Non-Invasive Radioisotope Method to Determine Ventricular Ejection Fractions and Cardiopulmonary Transit Times

Nuklearmedizin ◽

10.1055/s-0037-1620606 ◽

1977 ◽

Vol 16 (02) ◽

pp. 57-62

Author(s):

A. Ahonen ◽

J. Kuikka

Keyword(s):

Ejection Fraction ◽

Right Ventricle ◽

Transit Time ◽

Mean Transit Time ◽

Left Ventricular ◽

Ventricular Ejection ◽

Ventricular Ejection Fraction ◽

Non Invasive ◽

Transit Times ◽

Whole Heart

SummaryEjection fractions and cardiopulmonary transit times were measured in 20 hospital patients by means of intravenously injected 99mTc-radiocardiography. Time activity curves from the regions of the whole heart, superior vena cava, right atrium, right ventricle, right lung, left atrium and left ventricle were drawn and analyzed by using the modified gamma function fitting method. The comparison between the ejection fractions determined from the whole heart curves and those from the ventricular curves shows a correlation coefficient of 0.93 for the right ventricle and of 0.90 for the left, although there was a systematic difference between the determinations. The analysis of the single ventricular curves gave about 10 per cent higher values than those obtained from the whole heart curvesThe cardiopulmonary parameters measured from the whole heart curves for 16 normal subjects the following results gave:right ventricular ejection fraction = 0.57 ± 0.08left ventricular ejection fraction = 0.62 ± 0.08pulmonary mean transit time = 6.1 ± 1.1 heart-beatsintracardiac mean transit time = 10.5 ± 1.8 heartbeatsright/left ventricular volume = 1.10 ± 0.09These values agree closely with the data accumulated using more elaborate methods. The method presented here is simple to perform, it is non-invasive, time-saving, inexpensive, easy to analyze and suitable for exercising subjects and for bed-side measurements. Data assembly and analysis are easily automated so that results are obtainable immediately after measurements.

Download Full-text