Measurement of tidal volume during high-frequency jet ventilation.

The measurement of tidal volume during high-frequency jet ventilation is difficult due to the high-frequency components of the inspiratory flow. To validate tidal volume measured with a screen pneumotachograph placed on the expiratory limb, we simultaneously determined tidal volume with a body plethysmograph in seven anesthetized normal adult New Zealand rabbits before and after saline lung lavage. Four to six comparisons of tidal volume were obtained by varying peak inspiratory pressures at each combination of frequency (120, 240, and 480/min) and inspiratory to expiratory time ratio (1:1, 1:3, 1:5, 1:9).