Canadian Journal of Anesthesia, Vol 21, 114-116, Copyright © 1974 by Canadian Anesthesiologists' Society

Downstream Contamination of In-Series Vapourizers

¹ Department of Anaesthesia, Vancouver General Hospital and Faculty of Medicine, University of Brithish Columbia

Contamination of in-series vapourizers by transfilling has been reported^1,2 and it has been shown that if a vapourizer designed to volatilize a liquid of low vapour pressure (methoxyflurane) is placed in a downstream series position relative to a vapourizer designed for a liquid of high vapour pressure (halothane), the methoxyflurane vapourizer containing even small amounts of halothane can deliver anaesthetic concentrations of this agent in addition to the expected methoxyflurane output. This transfilling most probably occurs when vapourizers in series are opened simultaneously.

To determine the extent of this problem halothane concentrations were measured in the output from methoxyflurane vapourizers which were downstream from halothane vapourizers on twenty anaesthetic machines. The results are displayed in Table I. These results indicate that contamination had occurred in 70 per cent of the vapourizers tested and that in two of the twenty machines the concentrations were significantly high (1400 p.p.m. and 1200 p.p.m.).

It is suggested that vapourizers not be placed in series on anaesthetic machines, but have completely separate circuits.