Simple and accurate monitoring of end-tidal carbon dioxide tensions during high-frequency jet ventilation

To determine whether end-tidal carbon dioxide tension (PETCO2) accurately reflects PaCO2 during high-frequency jet ventilation (HFJV), 43 studies were performed on eight mongrel dogs with normal lungs. During HFJV, minute volume was modified to obtain a range of PaCO2 values from 15.5 to 74.5 torr. When PETCO2 was measured with an infrared gas analyzer, there was a poor correlation between PaCO2 and PETCO2 values. However, when the high-frequency ventilator was adjusted to deliver large tidal-volume (sigh) breaths, PETCO2 values were significantly (r = 0.94, p less than .001) correlated with PaCO2. Our data suggest that the PETCO2 of alveolar gas is an accurate indicator of the PaCO2 during HFJV in nondiseased lungs.