Rediffusion of nitrous oxide prevents increases in endotracheal tube cuff pressure

An endotracheal tube designed to reduce nitrous oxide-induced intracuff pressure increases (Mallinckrodt Brandt rediffusion tracheal tube) and its relationship to nitrous oxide exposure was studied. Thirty-two subjects undergoing general anesthesia with endotracheal intubation used either a conventional endotracheal tube (Mallinckrodt Intermediate Hi-Lo) or a nitrous oxide rediffusion endotracheal tube (Mallinckrodt Brandt rediffusion). Intracuff pressures and nitrous oxide concentration were monitored continuously throughout surgery and recorded at 10-minute intervals for 50 minutes. The mean intratracheal cuff pressure in the rediffusion tube rose slightly from an initial 15.0 +/- 0.0 mmHg (mean +/- 1 SD) to 18.5 +/- 2.2 mmHg, which was less than in the conventional tube, 15.0 +/- 0.0 mmHg (initial) to 29.5 +/- 3.8 mmHg (50 minutes). Mean nitrous oxide concentration measured near the pilot balloon was 19.57 +/- 15.8 ppm with the conventional tube and 13.0 +/- 20.7 ppm with the rediffusion tube. Mean nitrous oxide concentration measured near the anesthetist's breathing area was 7.57 +/- 5.8 ppm with the conventional tube and 3.57 +/- 3.3 ppm in the rediffusion tube. All nitrous oxide concentration values remained within National Institute for Occupational Safety and Health recommendations (less than 25 ppm) and did not differ significantly between groups.