Comparison of the effects of low-flow and high-flow inhalational anaesthesia with nitrous oxide and desflurane on mucociliary activity and pulmonary function tests

Background and objectives The aim of this study was to investigate the effects of inhalational anaesthesia using low and high gas flow rates of nitrous oxide and desflurane on mucociliary clearance and pulmonary function. Methods Fifty adult patients of the American Society of Anesthesiologists physical status I-II, aged between 18 and 70 years, were recruited to the study. Patients were assigned randomly to one of two study groups. The fresh gas flow rate was 1 l min(-1) (0.5 l min(-1) O-2 + 0.5 l min(-1) N2O + desflurane) in group 1 and 3 l min(-1) (1.5 l min(-1) O-2 + 1.5 l min(-1) N2O + desflurane) in group 2. Patients' haemodynamic parameters and changes in the humidity and temperature of the inspired gases were recorded and the saccharin clearance time was measured before and after anaesthesia. Respiratory parameters, body temperature, end-tidal CO2 concentration and inspired and expired oxygen and nitrous oxide concentrations were also recorded. Results The forced vital capacity and forced expiratory volume in 1 s were significantly lower and the saccharin clearance time was significantly longer in group 2 compared to group 1 (P < 0.05). There were statistically significant differences between the groups regarding the humidity and temperature of the inspired gases (P < 0.05). Conclusion Respiratory function and mucociliary clearance are better preserved in a low-flow anaesthesia technique than in high-flow anaesthesia with nitrous oxide and desflurane. Therefore, a low-flow anaesthesia technique with nitrous oxide and desflurane may provide an important clinical advantage because it provides appropriately heated and humidified gases to the tracheobronchial tree. Eur J Anaesthesiol 2011;28:279-283 Published online 30 November 2010