[Effects of inverse ratio ventilation and positive end-expiratory pressure on gas exchanges in dogs with oleic acid induced pulmonary edema].

The purpose of this study was to determine the effect of inverse ratio ventilation (IRV) on gas exchanges and circulatory systems in 56 mongrel dogs with oleic acid induced pulmonary edema. The dogs were divided into 9 groups and were ventilated with 9 kinds of ventilatory modes such as I:E ratio of 1:2 (control), 2:1 (2:1 IRV), 3:1 (3:1 IRV), 1:2 with 5 cmH2O PEEP (1:2 PEEP 5), 2:1 with 5 cmH2O PEEP (2:1 PEEP 5), 3:1 with 5 cmH2O PEEP (3:1 PEEP 5), 1:2 with 10 cmH2O PEEP (1:2 PEEP 10), 2:1 with 10 cmH2O PEEP (2:1 PEEP 10) and 3:1 with 10 cmH2O PEEP (3:1 PEEP 10), using a Servo ventilator 900C. IRV could not improve arterial oxygenation in dogs with oleic acid induced pulmonary edema, but PEEP could significantly improve arterial oxygenation depending on PEEP level. Although in the control group, PaCO2 increased gradually, PaCO2 was kept constant for 8 hours in the 3:1 IRV groups. In the 2:1 group, PaCO2 did not change significantly until 6 hours, but in IRV with 10 cmH2O PEEP groups, PaCO2 showed the highest increase. There was no significant alteration in hemodynamics after ventilatory modes were changed to IRV. Although oxygen delivery was the best in the 3:1 IRV group, there was no statistical significance between the 3:1 IRV group and others. It was concluded that IRV did not improve arterial oxygenation but showed a favorable effect for CO2 elimination, in dogs with oleic acid induced pulmonary edema.