DISTAL EFFECTS OF TRACHEAL GAS INSUFFLATION - CHANGES WITH CATHETER POSITION AND OLEIC-ACID LUNG INJURY

We separated distal (turbulence-related) and proximal (dead space wash out-related) effects of tracheal gas insufflation (TGI) by comparing t he effects of straight and inverted catheters. We reasoned that the in verted catheter was unlikely to remove CO2 from conducting airways dis tal to its orifice. In six normal dogs during TGI at 10 l/min, advanci ng the catheters from 10 to 1 cm above the main carina decreased dead space volume by 29 +/- 12 and 12 +/- 6 mi (P < 0.04) with the straight and inverted catheters, respectively. By comparison, the tracheal vol ume between 10 and 1 cm above the carina was 15 +/- 2 mi. In another s et of dogs (n = 5), we examined the distal effects of TGI before and a fter oleic acid-induced lung injury. During TGI at 10 l/min before and after oleic acid injury, the differences in arterial PCO2 between the straight and inverted catheters were 5 +/- 1 and 9 +/- 6 Torr (P < 0. 18), respectively. Our data suggest that distal effects of TGI become more pronounced as the catheter tip is positioned closer to the main c arina. The distal effects of TGI were not diminished after oleic acid injury when minute ventilation was maintained constant.