Alternating ventilation in a rat model of increased abdominal pressure.

Abstract

During alternating ventilation (AV) one lung is inflating while the other is deflating. Considering the possible respiratory and hemodynamic advantages of AV, we investigated its effects during increased intra-abdominal pressure (IAP=10 mmHg). In Sprague-Dawley rats (n=6, 270-375g) the main bronchi were independently cannulated, and respiratory mechanics determined while animals underwent different ventilatory patterns: synchronic ventilation without increased IAP (SV-0), elevated IAP during SV (SV-10), and AV with elevated IAP (AV-10). Thirty-three other animals (SV-0, n=10; SV-10, n=11 and AV-10, n=12) were ventilated during 3h. Mean arterial pressure (MAP), and lung histology were assessed. Increased IAP resulted in significantly higher elastances (p<0.001), being AV-10 lower than SV-10 (p<0.020). SV-10 showed higher central venous pressure (p<0.003) than S-0; no change was observed in AV-10. Wet/dry lung weight ratio was lower in AV-10 than SV-10 (p=0.009). Application of AV reduced hemodynamic and lung impairments induced by increased IAP during SV.