Gas movement during jet ventilation.

By examining flows in the expiratory limb of a bias flow circuit, it is possible to measure tidal, entrained and spilt volumes during jet ventilation. Using this method on a canine model, tidal volume fell and minute volume rose when the respiratory rate rose from 12 to 200 breaths/min. The changes were compatible with a convective model of gas movement. Entrained volume remained a constant fraction of tidal volume and spilt volume fell as a fraction of jet volume as respiratory rate increased.