[The comparison of IRV and PEEP on gas exchanges in dogs with aspiration pneumonia].

The purpose of this study was to determine the effects of pressure control inverse ratio ventilation (PC-IRV) and PEEP (in which both mean airway pressure and tidal volume were the same), on the gas exchange and the hemodynamics in 40 dogs in which the bronchi were injected with 2 ml.kg-1 0.1 N-hydrochloric acid. The dogs were classified into 5 groups and were ventilated with 5 kinds of ventilatory modes for 8 hours. The control group was ventilated by volume control ventilation (VCV) without PEEP, using a Servo Ventilator 900 C. Group A was ventilated artificially by VCV with 5 cm H2O PEEP for 3 hours after administrering hydrochloric acid; the group was then ventilated with PC-IRV for the next 5 hours. Group B was ventilated with the reversed ventilatory modes of group A. Group C was ventilated by VCV with 10 cm H2O PEEP after injecting hydrochloric acid, and a ventilatory mode with PC-IRV was used for the next 5 hours. Group D received the reversed ventilatory modes of group C. In all groups, PaO2 decreased from about 140 to 70 mmHg by injecting hydrochloric acid. PEEP improved arterial oxygenation significantly depending on the PEEP level, but PC-IRV did not improve PaO2 in the dogs in which aspiration pneumonia was induced. In group C, PaO2 showed the highest increase. PC-IRV decreased PaCO2. It was concluded that PC-IRV did not improve arterial oxygenation but showed a favorable effect for CO2 elimination in dogs with aspiration pneumonia induced by hydrochloric acid.