The Journal of Thoracic and Cardiovascular Surgery, Vol 75, 267-272, Copyright © 1978 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Prevention of pulmonary insufficiency through prophylactic use of PEEP and rapid respiratory rates
J Askanazi, SD Wax, JF Neville Jr, EL Hanson, PB Kane, B Markarian, CE Bredenberg and WR Webb
This study evaluated the effectiveness of prophylactic positive end-
expiratory pressure (PEEP) rapid respiratory rates (RRR), and high tidal
volume (HTV) in prevention of congestive atelectasis. Measurements of
pulmonary hemodynamics, mechanics, gas exchange, functional residual
capacity (FRC), pathology, and cinemicroscopy were performed in 45
anesthetized dogs subjected to hemorrhagic hypotension. Randomly, the
animals received control ventilation, HTV (20 ml. per kilogram), RRR (32
breaths per minute), or PEEP (5 cm. of water). Carbon dioxide was added as
needed to maintain normocapnia. Control and HTV animals showed
characteristic changes of congestive atelectasis (capillary congestion,
stasis, interstitial edema, periarterial hemorrhage, alveolar edema, and
hemorrhage). These microscopic and cinemicroscopic changes were prevented
by PEEP and RRR and correlated with decreased physiological shunting (PEEP
10 percent, RRR 13 percent, HTV 22 percent; p less than 0.01) in the
postshock phase. PEEP increased FRC by 40 percent (p less than 0.02) and
reduced the pulmonary artery--small pulmonary vein gradient (PA-SPV),
suggesting a direct effect on the capillary bed. RRR did not affect FRC but
minimized the SPV-LA gradient. This effect on the pulmonary venules
theoretically could be mediated by stimulating lymphatic flow, thereby
decreasing interstitial edema. Thus PEEP and RRR are beneficial when used
prophylactically but may work by widely differing mechanisms.
