Experimental pulmonary edema due to intermittent positive pressure ventilation with high inflation pressures. Protection by positive end-expiratory pressure.

We used a small animal respirator to ventilate normal, anesthetized rats with room air at peak inspiratory pressures of 14, 30, or 45 cm H2O and no added end-expiratory pressures (intermittent positive pressure breathing [IPPB] 14/0, high inspiratory positive pressure breathing [HIPPB] 30/0, HIPPB 45/0). Other rats were ventilated with the same high inspiratory pressures but with an added end-expiratory pressure of 10 cm H2O (positive end-expiratory pressure [PEEP] 30/10, PEEP 45/10). Control rats that were not ventilated and the IPPB 14/0 group showed no pathologic lung changes. The HIPPB 30/0 and PEEP 30/10 groups had perivascular edema but no alveolar edema. The HIPPB 45/0 animals had alveolar and perivascular edema, severe hypoxemia, and decreased dynamic compliance and died within one hour. In contrast, the PEEP 45/10 animals had no alveolar edema and survived. We postulate that interstitial perivascular edema develops from ventilation with high inflating pressures by mechanisms of lung interdependen...