Concentration elimination of anaesthetic gases in operating theratres. Influence of anaesthesia apparatus leakages.

Halothane and nitrous oxide (N2O) concentrations were measured in operating theatres, in the areas corresponding to theinhalation zones of the anaesthetists and operating nurses. The measurements were performed in an operating theatre with a non-recirculating air exchange rate of 20/h. This was performed partly in model experiments and partly during the administration of anaesthesia by intubation. In the model experiments. the measurements were taken both with and without a specially constructed scavenging system. During anaesthesia, the measurements were taken exclusively with the scavenging system, although well-defined leakages were fitted into the otherwise gas-tight anaesthetic system. The results were supplemented by smoke experiments which showed the air distribution patterns. The investigation showed that the gases were concentrated over and around the operating table. Activities during surgery diluted this concentration. Furthermore, it was shown that leakage in the anaesthetic system significantly influences the achieving of a low gas-air mixture. Halothane concentrations in the inhalation zone of the anaesthetist and operating nurse can be reduced to 0.02 and 0.01 p.p.m. respectively, if the anaesthetic system is completely gas-tight.