CARDIORESPIRATORY EFFECTS OF CONVENTIONAL AND HIGH-FREQUENCY VENTILATION IN RABBITS WITH BILATERAL PNEUMOTHORACES AND SURFACTANT DEPLETED LUNGS

We compared high frequency ventilation (HFV) to conventional mechanica l ventilation (CMV) under normoxic and normocapnic condition in surfac tant depleted rabbits with bilateral pneumothoraces. We hypothesized t hat lower airway pressures would be required with HFV under these cond itions. We applied CMV and HFV in 8 anaesthetized rabbits with a proto type ventilator at frequencies of 30, 100, 200, and 300 cycles/min. A positive end-expiratory pressure (PEEP) just below the pressure suffic ient to open the air leak from the pneumothoraces was applied at all f requencies. Airway pressures, gas exchange, heart rate, and mean arter ial pressure were recorded. Peak airway pressure decreased significant ly from 2.50 to 2.10 kPa when the frequency of ventilation was increas ed from 30 to 300 cycles/min. There were no significant changes in mea n airway pressure P arterial pH, heart rate, and mean arterial pressur e when HFV was compared to CMV. In conduction, during HFV peak airway pressures measured at the mouth were decreased. Our ability to maintai n adequate gas exchange in the face of ongoing pulmonary air leaks may reflect lower alveolar pressures. (C) 1993 Wiley-Liss, Inc.