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 capillaries are recruited during pulsatile flow

2002 ◽  
Vol 92 (3) ◽  
pp. 1183-1190 ◽  
Author(s):  
Robert G. Presson ◽  
William A. Baumgartner ◽  
Amanda J. Peterson ◽  
Robb W. Glenny ◽  
Wiltz W. Wagner
Keyword(s):  
Pulsatile Flow ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Pressure Rise ◽  
Capillary Recruitment ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary ◽  
Direct Measurements ◽  
Pulmonary Arterial ◽  
The Mean

Capillaries recruit when pulmonary arterial pressure rises. The duration of increased pressure imposed in such experiments is usually on the order of minutes, although recent work shows that the recruitment response can occur in <4 s. In the present study, we investigate whether the brief pressure rise during cardiac systole can also cause recruitment and whether the recruitment is maintained during diastole. To study these basic aspects of pulmonary capillary hemodynamics, isolated dog lungs were pump perfused alternately by steady flow and pulsatile flow with the mean arterial and left atrial pressures held constant. Several direct measurements of capillary recruitment were made with videomicroscopy. The total number and total length of perfused capillaries increased significantly during pulsatile flow by 94 and 105%, respectively. Of the newly recruited capillaries, 92% were perfused by red blood cells throughout the pulsatile cycle. These data provide the first direct account of how the pulmonary capillaries respond to pulsatile flow by showing that capillaries are recruited during the systolic pulse and that, once open, the capillaries remain open throughout the pulsatile cycle.

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.

Measurement of pulmonary blood flow during exercise using nitrous oxide

1962 ◽  
Vol 17 (4) ◽  
pp. 579-586 ◽  
Author(s):  
Margaret R. Becklake ◽  
C. J. Varvis ◽  
L. D. Pengelly ◽  
S. Kenning ◽  
M. McGregor ◽  
...  
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Dilution Technique ◽  
Fick Principle ◽  
Pulmonary Capillary Blood Flow ◽  
Time Period ◽  
Pulmonary Capillary ◽  
Wide Range ◽  
Pulmonary Capillary Blood ◽  
The Difference

Pulmonary capillary blood flow (Qc) in the exercising subject was calculated from the rate of disappearance of N2O during steady state breathing of an N2O-He-O2 mixture. Measurements were made after alveolar rinsing (reciprocal of N2 washout) had occurred, and up to 30 sec, a time period accompanied by minimal recirculation, since FaNN2O during this period did not rise significantly. Repeatability of the method, judged as the difference of a second estimate from a first on the same subject, was comparable to that reported for the direct Fick technique in resting subjects (31 of 33 paired observations agreed within 20%). Results over a wide range agreed with almost simultaneous measurements by a dye dilution technique (24 of 26 paired observations agreed within 20%), and when related to pulse rate and to Vo2, were comparable to those of the other workers whose subjects were studied in a similar posture. Indeed, this technique (using the indirect Fick principle under “steady state” conditions) probably attains its greatest accuracy during exercise when other methods become less easily applicable. Submitted on December 18, 1961

Pulmonary capillary recruitment during airway hypoxia in the dog

1975 ◽  
Vol 39 (6) ◽  
pp. 900-905 ◽  
Author(s):  
W. W. Wagner ◽  
L. P. Latham
Keyword(s):  
Cardiac Output ◽  
Pulmonary Artery ◽  
Left Atrial ◽  
Weak Correlation ◽  
Capillary Length ◽  
Capillary Recruitment ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary ◽  
Anesthetized Dogs ◽  
Measuring Tool

To study the effect of hypoxia on the pulmonary capillaries, windows were inserted in the chest wall of 9 pentobarbital-anesthetized dogs. A microscope with an image-superimposing device was used to make drawings of the perfused capillaries. Summed lengths of individual perfused capillaries in the drawing were determined with a map-measuring tool. Total capillary length was constant between PaO2 of 160 and 70 Torr. As PaO2 fell below 70 Torr, recruitment of previously unperfused capillaries occurred in every case; at PaO2 of 40 Torr, the total length of perfused capillaries was about 4 times greater than during normoxia. There was no correlation between the recruitment of capillaries and alterations in left atrial pressure, only a weak correlation with cardiac output changes, but a very strong correlation with increased pulmonary artery pressure. This implies that recruitment was probably caused by vasoconstriction within the lung.

Site of recruitment in the pulmonary microcirculation

1989 ◽  
Vol 66 (5) ◽  
pp. 2079-2083 ◽  
Author(s):  
W. L. Hanson ◽  
J. D. Emhardt ◽  
J. P. Bartek ◽  
L. P. Latham ◽  
L. L. Checkley ◽  
...  
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Total Surface Area ◽  
Capillary Recruitment ◽  
Fluid Load ◽  
Pulmonary Arterial ◽  
Pulmonary Microcirculation ◽  
Adequate Oxygenation ◽  
Made In

Increasing the total surface area of the pulmonary blood-gas interface by capillary recruitment is an important factor in maintaining adequate oxygenation when metabolic demands increase. Capillaries are known to be recruited during conditions that raise pulmonary blood flow and pressure. To determine whether pulmonary arterioles and venules are part of the recruitment process, we made in vivo microscopic observations of the subpleural microcirculation (all vessels less than 100 microns) in the upper lung where blood flow is low (zone 2). To evoke recruitment, pulmonary arterial pressure was elevated either by an intravascular fluid load or by airway hypoxia. Of 209 arteriolar segments compared during low and high pulmonary arterial pressures, none recruited or derecruited. Elevated arterial pressure, however, did increase the number of perfused capillary segments by 96% with hypoxia and 165% with fluid load. Recruitment was essentially absent in venules (4 cases of recruitment in 289 segments as pressure was raised). These data support the concept that recruitment in the pulmonary circulation is exclusively a capillary event.

scholarly journals A perpetual switching system in pulmonary capillaries

2019 ◽  
Vol 126 (2) ◽  
pp. 494-501 ◽  
Author(s):  
Wiltz W. Wagner ◽  
Eric M. Jaryszak ◽  
Amanda J. Peterson ◽  
Claire M. Doerschuk ◽  
H. Glenn Bohlen ◽  
...  
Keyword(s):  
Acute Stress ◽  
Capillary Flow ◽  
Ex Vivo ◽  
Autologous Blood ◽  
Flow Patterns ◽  
Switching System ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary ◽  
Switching Patterns ◽  
Pulmonary Microcirculation

Of the 300 billion capillaries in the human lung, a small fraction meet normal oxygen requirements at rest, with the remainder forming a large reserve. The maximum oxygen demands of the acute stress response require that the reserve capillaries are rapidly recruited. To remain primed for emergencies, the normal cardiac output must be parceled throughout the capillary bed to maintain low opening pressures. The flow-distributing system requires complex switching. Because the pulmonary microcirculation contains contractile machinery, one hypothesis posits an active switching system. The opposing hypothesis is based on passive switching that requires no regulation. Both hypotheses were tested ex vivo in canine lung lobes. The lobes were perfused first with autologous blood, and capillary switching patterns were recorded by videomicroscopy. Next, the vasculature of the lobes was saline flushed, fixed by glutaraldehyde perfusion, flushed again, and then reperfused with the original, unfixed blood. Flow patterns through the same capillaries were recorded again. The 16-min-long videos were divided into 4-s increments. Each capillary segment was recorded as being perfused if at least one red blood cell crossed the entire segment. Otherwise it was recorded as unperfused. These binary measurements were made manually for each segment during every 4 s throughout the 16-min recordings of the fresh and fixed capillaries (>60,000 measurements). Unexpectedly, the switching patterns did not change after fixation. We conclude that the pulmonary capillaries can remain primed for emergencies without requiring regulation: no detectors, no feedback loops, and no effectors—a rare system in biology. NEW & NOTEWORTHY The fluctuating flow patterns of red blood cells within the pulmonary capillary networks have been assumed to be actively controlled within the pulmonary microcirculation. Here we show that the capillary flow switching patterns in the same network are the same whether the lungs are fresh or fixed. This unexpected observation can be successfully explained by a new model of pulmonary capillary flow based on chaos theory and fractal mathematics.

scholarly journals Pulmonary capillary surface area in supine exercising humans: demonstration of vascular recruitment

2019 ◽  
Vol 317 (3) ◽  
pp. L361-L368 ◽  
Author(s):  
David Langleben ◽  
Stylianos E. Orfanos ◽  
Michele Giovinazzo ◽  
Robert D. Schlesinger ◽  
Robert Naeije ◽  
...  
Keyword(s):  
Pulmonary Artery ◽  
Surface Area ◽  
Exercise Physiology ◽  
Calculated Data ◽  
Peak Exercise ◽  
Capillary Surface ◽  
Capillary Recruitment ◽  
Mean Pulmonary Arterial Pressure ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary

In exercising humans, cardiac output (CO) increases, with minor increases in pulmonary artery pressure (PAP). It is unknown if the CO is accommodated via distention of already perfused capillaries or via recruitment of nonconcomitantly perfused pulmonary capillaries. Ten subjects (9 female) performed symptom-limited exercise. Six had resting mean PAP (PAPm) <20 mmHg, and four had PAPm between 21 and 24 mmHg. The first-pass pulmonary circulatory metabolism of [3H]benzoyl-Phe-Ala-Pro (BPAP) was measured at rest and at peak exercise, and functional capillary surface area (FCSA) was calculated. Data are means ± SD. Mean pulmonary arterial pressure rose from 18.8 ± 3.3 SD mmHg to 28.5 ± 4.6 SD mmHg, CO from 6.4 ± 1.6 to 13.4 ± 2.9 L/min, and pulmonary artery wedge pressure from 14 ± 3.3 to 19.5 ± 5 mmHg (all P ≤ 0.001). Percent BPAP metabolism fell from 74.7 ± 0.1% to 67.1 ± 0.1%, and FCSA/body surface area (BSA) rose from 2,939 ± 640 to 5,018 ± 1,032 mL·min−1·m−2 (all P < 0.001). In nine subjects, the FCSA/BSA-to-CO relationship suggested principally capillary recruitment and not distention. In subject 10, a marathon runner, resting CO and FCSA/BSA were high, and increases with exercise suggested distention. Exercising humans demonstrate pulmonary capillary recruitment and distention. At moderate resting CO, increasing blood flow causes principally recruitment while, based on one subject, when exercise begins at high CO, further increases appear to cause distention. Our findings clarify an important physiologic question. The technique may provide a means for further understanding exercise physiology, its limitation in pulmonary hypertension, and responses to therapy.

Intravital microscopic observations of 15-μm microspheres lodging in the pulmonary microcirculation

2005 ◽  
Vol 98 (6) ◽  
pp. 2242-2248 ◽  
Author(s):  
Wayne J. E. Lamm ◽  
Susan L. Bernard ◽  
Wiltz W. Wagner ◽  
Robb W. Glenny
Keyword(s):  
Blood Flow ◽  
Flow Distribution ◽  
Lung Model ◽  
Blood Flow Distribution ◽  
Local Flow ◽  
Pulmonary Capillary Blood Flow ◽  
Pulmonary Capillary ◽  
Perfused Lung ◽  
Pulmonary Capillary Blood ◽  
Pulmonary Microcirculation

Vascular infusions of 15-μm-diameter microspheres are used to study pulmonary blood flow distribution. The sites of microsphere lodging and their effects on microvascular perfusion are debated but unknown. Using intravital microscopy of the subpleural surface of rat lungs, we directly observed deposition of fluorescent microspheres. In a pump-perfused lung model, ∼0.5 million microspheres were infused over 30 s into the pulmonary artery of seven rats. Microsphere lodging was analyzed for the location in the microvasculature and the effect on local flow after lodging. On average, we observed 3.2 microspheres per 160 alveolar facets. The microspheres always entered the arterioles as singlets and lodged at the inlets to capillaries, either in alveolar corner vessels or small arterioles. In all cases, blood flow continued either around the microspheres or into the capillaries via adjacent pathways. We conclude that 15-μm-diameter microspheres, in doses in excess of those used in typical studies, have no significant impact on pulmonary capillary blood flow distribution.

scholarly journals Contribution of serial and parallel microperfusion to spatial variability in pulmonary inter- and intra-acinar blood flow

2010 ◽  
Vol 108 (5) ◽  
pp. 1116-1126 ◽  
Author(s):  
A. R. Clark ◽  
K. S. Burrowes ◽  
M. H. Tawhai
Keyword(s):  
Blood Flow ◽  
Blood Vessels ◽  
Distal Portion ◽  
Model Structure ◽  
Capillary Recruitment ◽  
Pulmonary Acinus ◽  
Acinar Structure ◽  
Computational Simplicity ◽  
Pulmonary Microcirculation ◽  
Increased Blood Flow

This study presents a theoretical model of combined series and parallel perfusion in the human pulmonary acinus that maintains computational simplicity while capturing some important features of acinar structure. The model provides a transition between existing models of perfusion in the large pulmonary blood vessels and the pulmonary microcirculation. Arterioles and venules are represented as distinct elastic vessels that follow the branching structure of the acinar airways. These vessels are assumed to be joined at each generation by capillary sheets that cover the alveoli present at that generation, forming a “ladderlike” structure. Compared with a model structure in which capillary beds connect only the most distal blood vessels in the acinus, the model with combined serial and parallel perfusion provides greater capacity for increased blood flow in the lung via capillary recruitment when the blood pressure is elevated. Stratification of acinar perfusion emerges in the model, with red blood cell transit time significantly larger in the distal portion of the acinus compared with the proximal portion. This proximal-to-distal pattern of perfusion may act in concert with diffusional screening to optimize the potential for gas exchange.

Pulmonary capillary diameters and recruitment characteristics in subpleural and interior networks

1996 ◽  
Vol 80 (5) ◽  
pp. 1568-1573 ◽  
Author(s):  
A. C. Short ◽  
M. L. Montoya ◽  
S. A. Gebb ◽  
R. G. Presson ◽  
W. W. Wagner ◽  
...  
Keyword(s):  
Cross Sections ◽  
Blood Cells ◽  
Alveolar Wall ◽  
Lung Inflation ◽  
Capillary Recruitment ◽  
Cell Counts ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary ◽  
Wide Range

In vivo microscopic observations of pulmonary capillaries are limited to subpleural networks that are less dense than interior networks. In addition to the density difference, subpleural and interior capillary diameters may differ, although there are conflicting data on this point. We measured the diameters of subpleural and interior capillaries in rats and dogs. Subpleural diameters were 30% larger in rats and 20% larger in dogs. Because diameter and density differences might cause differences in recruitment between subpleural and interior networks, we measured subpleural and interior recruitment by counting the number of red blood cells per 10 microns of alveolar wall in histological cross sections of rapidly frozen rat lungs. Lung inflation pressures of 4, 12, and 25 cmH2O created a wide range of capillary recruitment in different groups of animals. Red blood cell counts for interior and subpleural capillaries moved in parallel and progressively increased as inflation pressures were reduced. These data demonstrate that recruitment in subpleural capillaries accurately reflect recruitment in interior capillaries and validate the use of in vivo microscopic observations of subpleural capillaries to investigate pulmonary capillary recruitment in general.

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