PEEP and low tidal volume ventilation reduce lung water in porcine pulmonary edema

This study analyzed the effect of both positive end-expiratory pressure (PEEP) and reduction in tidal volume (VT) on extravascular lung water (EVLW) in a permeability model of pulmonary edema. Inmediately after producing a pulmonary edema with oleic acid, 21 pigs were randomized into three groups. Group I (n = 8): PEEP of 0 cm H2O (ZEEP), VT of 12 ml/kg; Group II (n = 6): PEEP of 10 cm H2O, VT of 12 ml/kg; Group III (n = 7): PEEP of 10 cm H2O, VT of 6 ml/kg. EVLW was measured by the double indicator method (DI) at baseline (time 0) and after 30, 60, 120, 180, and 240 min and by the gravimetric method (G) at 240 min. Both methods correlated excellently (r = 0.94, p < 0.0001). EVLW-DI was significantly less with PEEP application (Group II versus Group I) at 180 min and thereafter. Likewise, EVLW-DI was less throughout the experimental period with reduced VT once PEEP was applied (Group III versus Group II). EVLW-G was less in Group II than in Group I at 16.3 +/- 2.7 and 23.2 +/- 4.2 ml/kg, respectively (p < 0.0001), and less in Group III than in Group II at 10.7 +/- 0.9 and 16.3 +/- 2.7 ml/kg (p < 0.0001). We conclude that early application of 10 cm H2O of PEEP reduces EVLW in permeability pulmonary edema. The lowering of VT reduced EVLW even further.