Nitrous‐oxide Analgesia During Ambulance Transportation. Airborne Levels of Nitrous Oxide

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Abstract
A model experiment was performed for studying N2O levels in the breathing zones of the different members of an ambulance team, i.e., the anesthetist, the accompanying person in the ambulance coupe, and the ambulance driver. Without a functioning local exhaust coupled to the exhalation valve, the integrated average level of N2O in the breathing zone of the anesthetist was 650-1700 ppm, with top concentrations up to 7500 ppm. The accompanying person in the ambulance coupe was exposed to average concentrations of 58-280 ppm, with top concentrations up to 660 ppm. The mean exposure of the driver was 9-45 ppm (maximum 81 ppm). The exposure to N2O was decreased in all parts of the ambulance by an effective local exhaust system. A prerequisite for N2O analgesia in ambulances is an effective local exhaust coupled to the exhalation valve or face mask. The ambulance coupe should be equipped with a motor-driven exhaust fan in the roof, the ordinary inlet fan of the ambulance should be switched on at maximum speed, and any additional heater or fan in the ambulance coupe should be placed inside the coupe and not behind the driver''s seat.