Accuracy of 94 anaesthetic agent vaporizers in clinical use.
Using the Brüel & Kjaer Anaesthetic Gas Monitor type 1304, we have monitored the output of 94 anaesthetic agent vaporizers (Fluotec 3:58, Enfluratec 3:24, Isotec 3:12), in seven departments of anaesthesia, at different dial settings and flow rates. The range of output, for one type of vaporizer and dial setting (flow: 6 litre min-1) was largest with the Fluotec 3 (0.85-1.55% when dial set to 1%) and smallest with the Isotec 3 (0.85-1.15% when dial set to 1%). In determining the number of vaporizers with unacceptable inaccuracy, we applied acceptance limits of +/- 15% relative on each vaporizer and each dial setting. Using a flow of oxygen 6 litre min-1 17% of Fluotec 3.8% of Isotec 3 and 71% of Enfluratec 3 vaporizers had outputs outside those limits. Even when some specific conditions (vaporizers giving output beyond the limits at any two or more dial settings; output beyond the limits in the clinically relevant range (0.5-2%)) were added, a substantial number of vaporizers did not perform within the limits. We found a significantly greater accuracy of the vaporizers after 3-monthly calibration checks (P < 0.05) compared with vaporizers undergoing service and calibration only annually. Using a questionnaire, we found that fewer than 30% of the anaesthetists using the vaporizers would accept aberrance beyond +/- 10% relative of the dial setting.
Department of Anaesthesia, Herlev Hospital, University of Copenhagen, Medical School, Denmark.
J
J
Nielsen
F M
FM
Pedersen
F
F
Knudsen
M B
MB
Jensen
M
M
Ibsen
D000769:Anesthesia, Inhalation / Q000295:instrumentation*; D002138:Calibration; D004869:Equipment Safety; D009330:Nebulizers and Vaporizers / Q000592:standards*; D013997:Time Factors