BENEFICIAL AND HARMFUL EFFECTS OF POSITIVE END EXPIRATORY PRESSURE

  • 1 January 1978
    • journal article
    • research article
    • Vol. 147  (4) , 518-524
Abstract
The effects of increasing levels of positive end expiratory pressure on gas exchange and pulmonary mechanics were determined utilizing an ex vivo ventilated perfused canine pulmonary lobe. When zero positive end expiratory pressure was used, shunting, weight gain and a decrease in compliance occurred over the 4 1/2 h experiment. Shunting was eliminated when 5, 10 or 15 cm of water of positive end expiratory pressure were used. Increasing extravascular fluid sequestration and decreasing pulmonary compliance occurred progressively with increasing levels of positive end expiratory pressure above 5 cm of water. Pulmonary artery pressure increased immediately along with end inspiratory pressure, an amount approximately equal to the increase in positive end expiratory pressure and this is thought to be the primary cause of the increased rate of fluid sequestration. An optimal level of positive end expiratory pressure apparently exists when the shunt can be reduced and oxygenation improved without increasing the rate of extravascular fluid accumulation to the point where long time deleterious effects could outweigh immediate benefits.

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