Performance of Anesthesia Machines' Devices that are Not Part of the Food and Drug Administration's Daily Checkout

Abstract

Objective. The Food and Drug Administration’s (FDA) checkoutrecommendations are to be applied, at least daily, on anesthesia machines.Devices included in the checkout are crucial to the safe operation of themachine. Remaining devices do not need to be checked as often. However, theyshould be checked at some appropriate interval. We calculated the reliabilityof the non-FDA checkout devices, to predict failure rates of these devices.Methods. The study included 36 North American Drager Narkomed anesthesiamachines that were in service a total of 109,410 days at a universityhospital. Reliability (i.e., statistical) analyses were done using in-housedata recorded by biomedical technicians during 3359 monthly machineinspections. If any one device was operating outside of the limits of themanufacturer’s specifications, the machine was labeled as having failedits inspection. Results. Assumptions of the failure analysis were satisfied.The mean time between failures equaled 1351 days or 3.7 years (lower95%confidence bound 1123 days or 3.1 years). The mean daily probability of oneor more devices failing to perform within the manufacturer’sspecification between inspections equaled 1.1%, 2.2%, and4.4% for inspectionsevery 1, 2, or 4 months, respectively. Probabilities that a machine would failon demand between inspections were approximately equal to the mean dailyprobabilities of machine failure. The mean number of days per year that amachine would be operating with a device that is outside of the limits of itsspecifications equaled 4, 8, and 12 days, respectively. The mean dailyprobabilities of failure and the probabilities of failure on demand were bothdirectly proportional to the inspection interval. Conclusions. Our failureanalysis provides a rational basis for choosing an appropriate inspectioninterval for anesthesia machines’ devices that are not included in theFDA’s checkout recommendations.