Effect of graded administration of PEEP on lung water in noncardiogenic pulmonary edema

The effect of graded application of positive end-expiratory pressure (PEEP) was studied in 10 mongrel dogs with pulmonary edema induced by oleic acid infusion. Six animals received progressive increases in PEEP (5 cm H2O) 120 min after the injection of oleic acid. These animals were compared to 4 control animals who did not receive PEEP. We found no difference between the 2 groups in lung water measured by a double indicator dilution technique during PEEP application. Lung water determined by gravimetric analysis was also not different between groups at the end of the experiment. PEEP did result in significant reductions in shunt fraction and alveolar-arterial oxygen tension difference suggesting that PEEP improves gas exchange in pulmonary edema by increasing lung volume, but not by altering lung water accumulation.