The effect of capillary pressure and lung distention on capillary recruitment. Godbey, Patricia S., Jacquelyn A. Graham, Robert G. Presson, Jr, Wiltz W. Wagner, Jr., and Thomas C. Lloyd, Jr. Departments of Anesthesia, Physiology/Biophysics, Pediatrics, and Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120
APStracts 2:0215A, 1995.
To investigate the effect of capillary pressure and alveolar distention on capillary recruitment, we used video microscopy to quantify capillary recruitment in individual subpleural alveolar walls. Canine lobes were perfused with autologous blood either while inflated by positive airway pressure or while inflated by negative intrapleural pressure in the intact thorax with airway pressure remaining atmospheric. Low flow rates minimized the arterio-venous pressure gradient (< 5 mmHg) permitting capillary pressure estimation by averaging these pressures. Capillary pressure was varied stepwise from airway pressure to 30 mmHg above airway pressure. Capillary recruitment always began as capillary pressure exceeded airway pressure. At low positive airway pressures, the capillaries of the excised lobes opened suddenly over a narrow pressure range. At higher airway pressures and in the intact thorax, recruitment occurred over a wide range of capillary pressures. We conclude that capillary perfusion begins when intracapillary pressure just exceeds alveolar pressure, but that further increases in capillary pressure recruit capillaries depending on tension in the alveolar wall, whether imposed by positive airway pressure or by gravity when the lung is suspended in an intact thorax. 

Received 21 November 1994; accepted in final form 16 May 1995.
APS Manuscript Number A1191-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.