Effect of increasing flow on distribution of pulmonary capillary transit times

1994 ◽  
Vol 76 (4) ◽  
pp. 1701-1711 ◽  
Author(s):  
R. G. Presson ◽  
C. C. Hanger ◽  
P. S. Godbey ◽  
J. A. Graham ◽  
T. C. Lloyd ◽  
...  
Keyword(s):  
Blood Flow ◽  
Relative Dispersion ◽  
Capillary Perfusion ◽  
Capillary Recruitment ◽  
Complex Morphology ◽  
Transit Times ◽  
Pulmonary Capillary ◽  
In Transit ◽  
The Relationship ◽  
Flow Capillary

The complex morphology of the pulmonary capillary network causes capillary transit times to be dispersed about a mean. It is known that flow-induced decreases in mean capillary transit time are partially offset by capillary recruitment and distension, but the effect of these factors on the rest of the distribution of transit times is unknown. We have studied the relationship between blood flow, capillary recruitment, and the distribution of transit times in isolated canine lungs with videomicroscopy. Doubling baseline lobar blood flow recruited capillaries. All transit times in the distribution decreased, as did relative dispersion. Doubling flow again caused a further decrease in transit times, but neither capillary recruitment nor relative dispersion changed significantly. We conclude that capillary transit times become more homogeneous as lobar flow increases from low to intermediate levels. Further increases in flow across a fully recruited network are associated with decreases in transit times but not with more homogeneous capillary perfusion.

Capillary recruitment and transit time in the rat lung

1997 ◽  
Vol 83 (2) ◽  
pp. 543-549 ◽  
Author(s):  
Robert G. Presson ◽  
Thomas M. Todoran ◽  
Bracken J. De Witt ◽  
Ivan F. McMurtry ◽  
Wiltz W. Wagner
Keyword(s):  
Blood Flow ◽  
Transit Time ◽  
Pulmonary Blood Flow ◽  
Perfusion Pressure ◽  
Intact Animal ◽  
Metabolic Rates ◽  
Rat Lung ◽  
Capillary Perfusion ◽  
Capillary Recruitment ◽  
In Transit

Presson, Robert G., Jr., Thomas M. Todoran, Bracken J. De Witt, Ivan F. McMurtry, and Wiltz W. Wagner, Jr.Capillary recruitment and transit time in the rat lung. J. Appl. Physiol. 83(2): 543–549, 1997.—Increasing pulmonary blood flow and the associated rise in capillary perfusion pressure cause capillary recruitment. The resulting increase in capillary volume limits the decrease in capillary transit time. We hypothesize that small species with relatively high resting metabolic rates are more likely to utilize a larger fraction of gas-exchange reserve at rest. Without reserve, we anticipate that capillary transit time will decrease rapidly as pulmonary blood flow rises. To test this hypothesis, we measured capillary recruitment and transit time in isolated rat lungs. As flow increased, transit time decreased, and capillaries were recruited. The decrease in transit time was limited by an increase in the homogeneity of the transit time distribution and an increased capillary volume due, in part, to recruitment. The recruitable capillaries, however, were nearly completely perfused at flow rates and pressures that were less than basal for the intact animal. This suggests that a limited reserve of recruitable capillaries in the lungs of species with high resting metabolic rates may contribute to their inability to raise O2 consumption manyfold above basal values.

Erythrocyte and polymorphonuclear cell transit time and concentration in human pulmonary capillaries

1994 ◽  
Vol 77 (4) ◽  
pp. 1795-1800 ◽  
Author(s):  
J. C. Hogg ◽  
H. O. Coxson ◽  
M. L. Brumwell ◽  
N. Beyers ◽  
C. M. Doerschuk ◽  
...  
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
Lung Resection ◽  
Capillary Blood ◽  
Lung Sample ◽  
Pulmonary Capillaries ◽  
Transit Times ◽  
Pulmonary Capillary ◽  
Capillary Blood Volume ◽  
Pulmonary Capillary Blood

Pulmonary capillary transit times were examined in patients who required lung resection by use of 99mTc-labeled macroaggregates (99Tc-MAA) and chromium-labeled erythrocytes (51Cr-RBC) to measure regional blood flow and volume in the resected lung. Cell flow (cells.ml-1.s-1) to each resected lung sample was determined by multiplying the number of polymorphonuclear leukocytes (PMN) per milliliter of circulating blood by the blood flow to that sample. Capillary blood volume was obtained by multiplying the morphometrically determined fraction of pulmonary blood in capillaries by the total 51Cr-RBC volume in each sample. Cell concentrations (cells/ml) in capillary blood were calculated morphometrically, and capillary transit times were obtained by dividing cell concentration by cell flow. The results show that PMN transit times were 60–100 times longer than the RBC transit times, with a 22% overlap between their distributions. We conclude that PMN are concentrated with respect to RBC in pulmonary capillary blood because of differences in their transit times and that these long transit times provide an opportunity for PMN-endothelial interactions.

Parallel changes of blood flow and heterogeneity of capillary plasma perfusion in rat brains during hypocapnia

1996 ◽  
Vol 270 (4) ◽  
pp. H1441-H1445
Author(s):  
J. Vogel ◽  
R. Abounader ◽  
H. Schrock ◽  
K. Zeller ◽  
R. Duelli ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Coefficient Of Variation ◽  
Blue Dye ◽  
Capillary Perfusion ◽  
Brain Capillary ◽  
Arterial Pco2 ◽  
Transit Times ◽  
The Brain ◽  
Experimental Group

Plasma perfusion patterns were investigated in brain capillaries during decreased cerebral blood flow induced by hyperventilation. Anesthetized rats were decapitated 3-4 s after being given an intravenous bolus injection of Evans blue dye. the measured steep increase of the arterial dye concentration at this moment ensures that different capillary plasma transit times are reflected in different intracapillary dye concentrations. The observed heterogeneity of capillary plasma transit time was expressed as the coefficient of variation (means +/- SD) of the intracapillary dye concentrations. For comparison, cerebral blood flow was determined at comparable PCO2 values in a second experimental group. At arterial PCO2 values between 40 and 25 mmHg, the cerebral blood flow and the coefficient of variation of the intracapillary dye concentration decreased with decreasing PCO2, whereas at PCO2 values <25 mmHg cerebral blood flow and coefficient of variation did not correlate with the arterial PCO2. However, it cannot be excluded that the coefficient of variation of the intracapillary dye concentration increases between 25 and 14 mmHg and decreases between 14 and 10 mmHg. It is concluded that the reduction of cerebral blood flow measured during moderate hypocapnia is paralleled by a decreased heterogeneity of the brain capillary perfusion. During severe hypocapnia this relationship is lost, indicating a potential disturbance of the cerebral microcirculation.

Transit time dispersion in the pulmonary arterial tree

1998 ◽  
Vol 85 (2) ◽  
pp. 565-574 ◽  
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.

Distribution of pulmonary capillary transit times in recruited networks

1990 ◽  
Vol 69 (2) ◽  
pp. 473-478 ◽  
Author(s):  
R. L. Capen ◽  
W. L. Hanson ◽  
L. P. Latham ◽  
C. A. Dawson ◽  
W. W. Wagner
Keyword(s):  
Cardiac Output ◽  
Transit Time ◽  
Relative Dispersion ◽  
Capillary Networks ◽  
Transit Times ◽  
Pulmonary Capillary ◽  
Lower Lung ◽  
Anesthetized Dogs ◽  
The Mean

When pulmonary blood flow is elevated, hypoxemia can occur in the fastest-moving erythrocytes if their transit times through the capillaries fall below the minimum time for complete oxygenation. This desaturation is more likely to occur if the distribution of capillary transit times about the mean is large. Increasing cardiac output is known to decrease mean pulmonary capillary transit time, but the effect on the distribution of transit times has not been reported. We measured the mean and variance of transit times in single pulmonary capillary networks in the dependent lung of anesthetized dogs by in vivo videofluorescence microscopy of a fluorescein dye bolus passing from an arteriole to a venule. When cardiac output increased from 2.9 to 9.9 l/min, mean capillary transit time decreased from 2.0 to 0.8 s. Because transit time variance decreased proportionately (relative dispersion remained constant), increasing cardiac output did not alter the heterogeneity of local capillary transit times in the lower lung where the capillary bed was nearly fully recruited.

Selected Contribution: Measuring the response time of pulmonary capillary recruitment to sudden flow changes

2000 ◽  
Vol 89 (3) ◽  
pp. 1233-1238 ◽  
Author(s):  
Eric M. Jaryszak ◽  
William A. Baumgartner ◽  
Amanda J. Peterson ◽  
Robert G. Presson ◽  
Robb W. Glenny ◽  
...  
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Response Time ◽  
Capillary Recruitment ◽  
Lung Lobe ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary ◽  
Flow Changes ◽  
Pulmonary Microcirculation

To determine how rapidly pulmonary capillaries recruit after sudden changes in blood flow, we used an isolated canine lung lobe perfused by two pumps running in parallel. When one pump was turned off, flow was rapidly halved; when it was turned on again, flow immediately doubled. We recorded pulmonary capillary recruitment in subpleural alveoli using videomicroscopy to measure how rapidly the capillaries reached a new steady state after these step changes in blood flow. When flow was doubled, capillary recruitment reached steady state in <4 s. When flow was halved, steady state was reached in ∼8 s. We conclude that the pulmonary microcirculation responds rapidly to step changes in flow, even in the capillaries that are most distant from the hilum.

Pulmonary capillary perfusion: intra-alveolar fractal patterns and interalveolar independence

1999 ◽  
Vol 86 (3) ◽  
pp. 825-831 ◽  
Author(s):  
Wiltz W. Wagner ◽  
Thomas M. Todoran ◽  
Nobuhiro Tanabe ◽  
Teresa M. Wagner ◽  
Judith A. Tanner ◽  
...  
Keyword(s):  
Fractal Dimensions ◽  
Capillary Perfusion ◽  
Self Similarity ◽  
Pulmonary Capillary ◽  
Switching Patterns ◽  
Fractal Patterns ◽  
Capillary Bed ◽  
Switching Characteristics ◽  
Rapid Switching ◽  
The Relationship

Pulmonary capillary perfusion was analyzed from videomicroscopic recordings to determine flow switching characteristics among capillary segments in isolated, blood-perfused canine lungs. Within each alveolus, the rapid switching pattern was repetitive and was, therefore, nonrandom (fractal dimensions near 1.0). This self-similarity over time was unexpected in a network widely considered to be passive. Among adjacent alveoli, the relationship among the switching patterns was even more surprising, for there was virtually no relationship between the perfusion patterns (coefficients of determination approaching zero). These findings demonstrated that the perfusion patterns in individual alveolar walls were independent of their next-door neighbors. The lack of dependence among neighboring networks suggests an interesting characteristic: the failure of one alveolar-capillary bed would leave its neighbors relatively unaffected, a feature of a robust design.

scholarly journals Blood flow, capillary transit times, and tissue oxygenation: the centennial of capillary recruitment

2020 ◽  
Vol 129 (6) ◽  
pp. 1413-1421
Author(s):  
Leif Østergaard
Keyword(s):  
Blood Flow ◽  
Transit Time ◽  
Tissue Oxygenation ◽  
Plasma Viscosity ◽  
Capillary Endothelium ◽  
External Compression ◽  
Capillary Recruitment ◽  
Transit Times ◽  
Vascular Origin ◽  
Open Capillaries

The transport of oxygen between blood and tissue is limited by blood’s capillary transit time, understood as the time available for diffusion exchange before blood returns to the heart. If all capillaries contribute equally to tissue oxygenation at all times, this physical limitation would render vasodilation and increased blood flow insufficient means to meet increased metabolic demands in the heart, muscle, and other organs. In 1920, Danish physiologist August Krogh was awarded the Nobel Prize in Physiology or Medicine for his mathematical and quantitative, experimental demonstration of a solution to this conceptual problem: capillary recruitment, the active opening of previously closed capillaries to meet metabolic demands. Today, capillary recruitment is still mentioned in textbooks. When we suspect symptoms might represent hypoxia of a vascular origin, however, we search for relevant, flow-limiting conditions in our patients and rarely ascribe hypoxia or hypoxemia to short capillary transit times. This review describes how natural changes in capillary transit-time heterogeneity (CTH) and capillary hematocrit (HCT) across open capillaries during blood flow increases can account for a match of oxygen availability to metabolic demands in normal tissue. CTH and HCT depend on a number of factors: on blood properties, including plasma viscosity, the number, size, and deformability of blood cells, and blood cell interactions with capillary endothelium; on anatomical factors including glycocalyx, endothelial cells, basement membrane, and pericytes that affect the capillary diameter; and on any external compression. The review describes how risk factor- and disease-related changes in CTH and HCT interfere with flow-metabolism coupling and tissue oxygenation and discusses whether such capillary dysfunction contributes to vascular disease pathology.

Ventilatory threshold is related to walking tolerance in patients with intermittent claudication

VASA ◽  
2012 ◽  
Vol 41 (4) ◽  
pp. 275-281 ◽  
Author(s):  
da Rocha Chehuen ◽  
G. Cucato ◽  
P. dos Anjos Souza Barbosa ◽  
A. R. Costa ◽  
M. Ritti-Dias ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Intermittent Claudication ◽  
Lower Limb ◽  
Ventilatory Threshold ◽  
Reactive Hyperemia ◽  
Ankle Brachial Index ◽  
Metabolic Parameters ◽  
Walking Distance ◽  
The Relationship

Background: This study assessed the relationship between lower limb hemodynamics and metabolic parameters with walking tolerance in patients with intermittent claudication (IC). Patients and methods: Resting ankle-brachial index (ABI), baseline blood flow (BF), BF response to reactive hyperemia (BFRH), oxygen uptake (VO2), initial claudication distance (ICD) and total walking distance (TWD) were measured in 28 IC patients. Pearson and Spearman correlations were calculated. Results: ABI, baseline BF and BF response to RH did not correlate with ICD or TWD. VO2 at first ventilatory threshold and VO2peak were significantly and positively correlated with ICD (r = 0.41 and 0.54, respectively) and TWD (r = 0.65 and 0.71, respectively). Conclusions: VO2peak and VO2 at first ventilatory threshold, but not ABI, baseline BF and BFHR were associated with walking tolerance in IC patients. These results suggest that VO2 at first ventilatory threshold may be useful to evaluate walking tolerance and improvements in IC patients.

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