Operating room fires: part II. optimizing safety.

Background: The second part of the authors' study on operating room fires analyzes the construct of the nasal cannula used during facial surgery for patients under conscious sedation with supplemental oxygen. This prospective study compares two common styles of nasal cannulas with a nasopharyngeal system described in their first report.

Methods: Twenty patients underwent upper and/or lower lid blepharoplasty under conscious sedation with one of three methods of supplemental oxygen delivery: a Mac-Safe nasal cannula (Unomedical, Inc., McAllen, Texas), a Salter nasal cannula (Salter Laboratories, Arvin, Calif.), and a nasopharyngeal system with cut ends of a cannula placed into a rubber nasopharyngeal tube. Oxygen concentrations were measured at 24 locations around the face for each method at a low (3 liters/minute) and high flow rates (6 liters/minute) using a random access mass spectrometer unit.

Results: At both low and high oxygen flow rates, the median oxygen concentration at and above the nose was statistically lower (p < 0.001) using the nasopharyngeal system than with either the Mac-Safe or Salter nasal cannula. In addition, the oxygen concentrations measured using the two nasal cannulas were more variable than with the nasopharyngeal method, particularly at locations around and above the nose.

Conclusions: This study demonstrates that mass spectrometry oxygen readings around the face are similar to room air when the cut ends of the oxygen cannulas are passed down the nasaopharyngeal tube, whereas readings are significantly higher with the nasal cannulas. The nasopharyngeal system that the authors describe represents a significantly safer means of oxygen delivery during conscious sedation.