Determinants of ventilation during high-frequency jet ventilation

To better define the variables unrelated to ventilator frequency that affect gas transport during high-frequency jet ventilation (HFJV), we performed experiments in anesthetized paralyzed dogs (n = 8). The independent effects of changing driving pressure (300, 200, 150 kPa), catheter used for HFJV delivery (14-gauge and jet port of endotracheal tube), inspiratory time (30%, 50%, and 70%), and injector cannula diameter (12-gauge, 14-gauge, and 16-gauge) on minute volume (VE ), gas exchange, and cardiac output were studied at a ventilatory frequency of 100 min-1. VE increased with increasing driving pressure and inspiratory time. Entrainment decreased with increasing inspiratory time or when HFJV was delivered either via the jet port of the endotracheal tube, or via a jet cannula with distal side holes. Arterial PCO2 varied inversely with VE. Arterial oxygenation increased with hypocarbia, whereas venous admixture and cardiac output were unchanged. Several factors affect the ventilator-delivered and entrained volumes during HFJV, which in turn affect gas exchange. The determinants of gas exchange during HFJV appear to be similar to those described for conventional low-frequency positive-pressure ventilation. © 1987