Positive end expiratory pressure with increased intra-abdominal pressure.

Positive pressure ventilation with PEEP may be required in patients with increased IAP. Separately, PEEP and increase IAP have been shown in both man and animals to have significant hemodynamic effects. The results of this study demonstrated that, in dogs, the combination of PEEP with elevated IAP results in markedly increased CVP, PCWP, mean PAP and PVR. CO is depressed but to no greater degree than with the combination of IAP and positive pressure ventilation without PEEP. Interestingly, serum lactate levels markedly increase when both PEEP and IAP are applied, a finding not explained by the fall in CO. Possibly, the combination of PEEP with elevated IAP inhibits hepatic metabolism of lactate. Measures taken to reduce IAP and PEEP may not only improve hemodynamics but may result in reduced serum lactate levels.