Operating room air pollution: influence of anaesthetic circuit, vapour concentration, gas flow and ventilation

Atmospheric halothane was sampled from three selected operating theatres and anaesthetic rooms during the middle of operating sessions. Two of the operating theatres studied were ventilated with total air exchange once every six minutes; the third operating theatre had no ventilation. End-tidal samples were obtained from anaesthetists. Halothane vapour concentrations were analysed by gas-liquid chromatography. The effect of commonly used anaesthetic circuits on the level of contamination in the ambient atmosphere was studied. Concentrations of halothane vapour in the theatre atmosphere were found to vary with sampling site, anaesthetic circuit used, total gas flow and vapour concentration, the scavenging system employed and the efficiency of ventilation system. Although the ventilation system considerably reduced the level of halothane in the operating room atmosphere, it did not totally eliminate the contaminating vapour. A significant reduction in operating-room pollution was obtained by use of simple scavenging equipment. Scavenging of anaesthetic vapours outside the operating room led to 97.3 per cent reduction of overall mean concentration of halothane in the operating room atmosphere and reduction of 72 per cent in end-tidal samples of anaesthetists, with the Magill semiclosed circuit. The implications of these findings are discussed.