Effect of positive end-expiratory pressure on extravascular lung water in porcine acute respiratory failure

Recent studies of acute respiratory failure suggest that PEEP causes increased pulmonary interstitial fluid collection and therefore increased extravascular lung water (EVLW). We examined the effect of increasing levels of PEEP on EVLW in 20 to 25-kg pigs with acute respiratory failure induced by continuous infusion of live Pseudomonas aeruginosa (2 × 108 organisms/20 kg-min). Animals were intubated, paralyzed, and ventilated at 15 ml/kg tidal volume and an Fio2 of 0.4. Pigs in group 1 were given 4 ml/kg · h of iv fluid (lactated Ringerʼs solution) with no PEEP administered. Animals in groups 2 through 5 were given 0, 4, 17, and 44 ml/ kg h of lactated Ringerʼs solution, respectively, and PEEP was added at 5-cm H2O increments per half-hour, starting one hour after beginning P. aeruginosa infusion. EVLW in PEEP animals was less than or equal to that in controls despite variation in the administration of lactated Ringerʼs solution. This suggests that PEEP may slow EVLW accumulation over time and provide a protective effect that allows increased amounts of crystalloid fluids to be administered.