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

Abstract

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 Ringer's solution) with no PEEP administered. Animals in groups 2 through 5 were given 0, 4, 17, and 44 ml/ kg h of lactated Ringer's 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 Ringer's 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.