Journal of Applied Physiology, Vol 77, Issue 4 1630-1637, Copyright © 1994 by American Physiological Society

ARTICLES

Stability of alveolar capillary opening pressures

R. G. Presson Jr, O. Okada, C. C. Hanger, P. S. Godbey, J. A. Graham, R. W. Glenny, R. L. Capen and W. W. Wagner Jr
Department of Anesthesia, Indiana University School of Medicine, Indianapolis 46202.

Little is known about the stability of the process by which pulmonary capillaries open. To investigate this process, pulmonary capillary perfusion patterns in isolated pump-perfused canine lobes were studied using video microscopy. After pump flow was set to perfuse one-half of the capillaries, the pump was turned off and all of the capillaries emptied. Turning the pump back on reopened the capillaries. The on-off cycle was repeated six times. If the same capillaries were perfused during each observation, it would demonstrate that there were stable and significant differences between individual capillary opening pressures, causing consistent recruitment of those capillaries with the lowest opening pressures. Alternatively, variable perfusion patterns would result if capillary opening pressures changed between observations, if the differences in opening pressures between capillary segments were negligible, or if experimental conditions changed between cycles. The perfusion pattern was more reproducible than expected by chance alone, which indicated the existence of stable differences among alveolar capillary opening pressures.

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