Failure of positive end-expiratory pressure to decrease lung water content in alloxan-induced pulmonary edema.

The effect of 10 cm H2O of positive end-expiratory pressure (PEEP) on pulmonary extravascular water volume (PEWV) was measured in an animal model of noncardiogenic pulmonary edema. Three groups of animals were studied: (1) controls, (2) those given a saline infusion plus alloxan, and (3) those which received saline infusion plus alloxan and PEEP. All animals were ventilated with a constant volume ventilator. Mean PEWV (+/- SEM) in milliliters per gram of dry lung weight was 4.00 +/- 0.21 for group 1, 6.01 +/- 0.70 for group 2, and 5.77 +/- 0.83 for group 3. Mean PEWV increased significantly in both alloxan groups (groups 2 and 3) as compared to the control group (for both, p less than 0.05); however, PEWV did not differ significantly in the group that received PEEP, as compared to the group ventilated without PEEP. Arterial PO2 and airway pressure required to deliver a constant tidal volume did not change significantly in the experimental groups as compared to the control group. It was concluded that PEEP does not decrease lung water content in pulmonary edema caused by damage to fluid-exchanging vessels.