Do oxygen-enriched atmospheres exist beneath surgical drapes and contribute to fire hazard potential in the operating room?

The purposes of this study were to (1) describe the microenvironment in terms of oxygen concentration beneath the drapes of healthy subjects who were simulating patients undergoing minor surgical procedures with supplemental oxygen and to (2) evaluate the efficacy of using a scavenger system beneath the drapes. A convenience sample of 12 healthy volunteer subjects was studied in an ambulatory surgery center operating room, which was ventilated with 25 air exchanges per hour. The study was carried out in 2 parts. Each subject was supine, and oxygen was applied by a standard nondivided nasal cannula. The subjects were draped as routinely done for ophthalmic procedures. Oxygen concentrations were measured by using an Ohmeda Rascal II gas analyzer beneath the drapes and at the hypothetical surgical site with oxygen flow rates of 0, 1, 2, 3, and 4 L/min, allowing 5 minutes to elapse after a change in flow rate was made. Following a 10-minute break, the subjects were redraped, and the procedure was repeated using a scavenger system consisting of a suctioning system connected to wall suction at 170 to 190 mm Hg. Although the mean +/- SD oxygen saturation never fell below 95% (97.75% +/- 1.54%), mean +/- SD oxygen concentrations beneath the drapes were lower than normal room air concentrations (19.08% +/- 0.51%) when no oxygen was delivered to the patient. With supplemental oxygen and no scavenger system, oxygen concentrations beneath the drapes were consistently elevated (as high as 45% with 4 L/min) compared with normal ambient concentrations (21%) or with concentrations obtained at the surgical site (as high as 23.4%). With the scavenger system in place, mean +/- SD oxygen concentrations reached 34.08% +/- 5.52% beneath the drapes. Statistical analyses revealed that significantly higher oxygen concentrations occurred beneath the drapes with each incremental change in oxygen flow rate, and regardless of the oxygen flow rate used, oxygen concentrations beneath the drapes were significantly reduced with the use of the scavenger system.