Adsorption of desflurane from the scavenging system during high-flow and minimal-flow anaesthesia by zeolites

Application of high-silica zeolites in a special adsorber allows complete selective adsorption of the inhalation anaesthetic desflurane from the outlet port of the scavenging system of the anaesthesia machine. In comparison with charcoal filters, zeolites allow almost complete desorption at moderate temperatures followed by condensation of the desflurane to the liquid phase. The adsorption of scavenged desflurane by zeolites was measured in 13 patients. The duration of the anaesthesia was between 70 and 130 min. A minimal-flow regime (0.5 L min-1 fresh gas inflow) was used for maintenance in seven patients and a higher-flow regime (3 L min-1 fresh gas flow) was used for maintenance in six patients. In minimal-flow anaesthesia, 62% of the delivered desflurane was adsorbed by the zeolite while 86% of the delivered desflurane was adsorbed in higher-flow anaesthesia. Preliminary results show that about 85% of the adsorbed desflurane could be recovered as liquid with high purity via desorption.