Gas Exchange during High Frequency Flow-Interruption in Rabbits before and after Bronchoalveolar Lavage

Abstract

ABSTRACT. The performance of a high frequency flowinterrupter (HFFI) type neonatal ventilator was evaluated on nine adult rabbits (control) and on five adult rabbits after bronchoalveolar lavage (BAL). Tidal volumes and airway pressures were measured during conventional ventilation and during HFFI at rates of 4, 6, 8, 10, and 12 cycles/s. Tidal volumes were adjusted to maintain PaC02 between 35 and 42 mm Hg in control rabbits and 35-55 mm Hg in BAL rabbits; a positive end-expiratory pressure of 4 cm H 2 0 was applied to BAL rabbits to reduce atelectasis and improve gas exchange. The normalized tidal volume required to maintain PaCO2 within the specified range during HFFI varied between 2.02 mllkg (0.30 SD) and 2.55 (0.41) in control rabbits and between 2.65 (0.57) and 2.97 (0.51) in BAL rabbits. In neither group did the normalized tidal volume vary systematically with the rate of ventilation (p < 0.05). Mean airway pressures were lower during HFFI than during conventional ventilation in control rabbits but comparable in the BAL group. Peak inflation pressures were greater during HFFI than conventional ventilation in control rabbits but similar in the BAL group. End-expiratory lung volume was not affected by ventilation rate during HFFI in control rabbits. We conclude 1 ) that HFFI can maintain gas exchange in rabbits suffering from acute respiratory distress with airway pressures that are comparable to those measured during conventional ventilation and 2) the capacity of HFFI to ventilate the lungs with significantly lower airway pressures than conventional ventilation depends, in part, on the condition of the lungs. (Pediatr Res 24: 203-208, 1988) Abbreviations BAL, bronchoalveolar lavage cps, cycles per second F102, fractional concentration of oxygen in inspired gas HFFI, high frequency flow-interruption HFJV, high frequency jet ventilation HFV, high frequency ventilation Pao, airway opening pressure Paw, airway (tracheal) pressure Paw, mean airway pressure Po, dynamic pressure head PEEP, positive end-expiratory pressure PIP, peak inspiratory pressure TIITTOT, fractional duration of inspiration V,,,, peak flow