Abstract
The introduction of systems to facilitate the changing of vaporisers on the back bar of the anaesthetic machine has increased the risk of a vaporiser being tipped or inverted prior to attachment. The performance of three Ohmeda Tec 3 and three Ohmeda Tec 4 vaporisers following tipping to 30°, 90° and inversion to 180° was measured using a calibrated Datex Capnomac AGM-103 analyser. Both types of vaporiser when switched off tolerated tipping and inversion without alteration of the anaesthetic concentration subsequently delivered. The same was true for the Tec 3 after tipping to 30° and 90° with the dial set at zero or above. However, after inversion of the Tec 3 vaporiser with the dial at zero or higher, the anaesthetic concentration delivered was much greater than shown on the dial, initially exceeding 12% for all agents. Should a Tec 3 vaporiser be inverted with the dial at any setting other than OFF, it is necessary to adequately flush it with fresh gas and check its output prior to use.