Measurement of nitrous oxide concentrations in a simulated post anesthesia care unit environment

The postanesthesia care unit (PACU) nurse works in close proximity to patients during early stages of recovery. It is during this time that the patient exhales the highest levels of anesthetic gases. The National Institute for Occupational Health and Safety has established standards for exposure to waste anesthetic gases which state that sampling should be done in the breathing zone of those most heavily exposed. Thus, it is important that a sampling methodology, data acquisition system, and statistical analysis technique be developed which accurately measures waste anesthetic gas levels at a point representing the breathing zone of nurses providing bedside care. A study was conducted to obtain an understanding of how the concentration of nitrous oxide varies with distance from a recovering patient. The study found that concentration of nitrous oxide decreases with distance from the patient; the patient's respiration increases the level of nitrous oxide at the location of the nurse; and the respiration of the nurse pulls the flow field toward them, increasing their exposure to the gas. The results show the inadequacy of attempting to measure levels of gas exposure for PACU nurses by a sampling protocol which calls for samples taken at random points in the room.