Effects of driving pressure and respiratory rate on airway pressure and PaCO2 in rabbits during high-frequency jet ventilation.

The effects of driving pressure (DP) and respiratory rate (RR) on mean airway pressure (Paw), PaCO2, and other respiratory variables were studied during high-frequency jet ventilation (HFJV) in anesthetized rabbits. The animals were tracheotomized and paralyzed, and various combinations of RR (4, 8, 12, and 16 Hz) and DP (0.5, 1.0, and 2.0 kg/cm2) were applied randomly with an inspiratory/expiratory ratio of 1.0. HFJV was delivered via a 2.5-Fr catheter through a T-attachment, using 100% oxygen, and a hot-wire flowmeter was connected to the outlet of the T-attachment for measurement of the minute volume (MV). Heart rate, arterial BP and CVP, respiratory variables, and arterial blood gases were monitored during the study. There were no direct correlations between PaCO2 and DP, MV, or RR. However, there was an inverse correlation between PaCO2 and tidal volume, and linear correlations were found between Paw and DP, and between DP and MV. It is concluded that HFJV over an RR range of 4 to 16 Hz depends mainly upon tidal volume. When the desired PaCO2 and Paw are determined, DP and RR can be calculated following the equations established in this study.