Anaesthesia with the Boyle's bottle vaporizer.

Having used the Boyle's bottle vaporizer apparatus out of necessity in a developing country, the concentration of agent that had been administered was investigated retrospectively. Three anaesthetic agents, halothane, isoflurane and enflurane, were measured at different temperatures, using a Boyle's anaesthetic machine and a Boyle's bottle in circuit with a Magill breathing system connected to a Rascal II Agent Monitor. Bubbling a fresh gas flow of 5 l.min-1 through the anaesthetic liquids generated concentrations in excess of 12%. Elevating the initial temperature of the vaporizer increased the delivered concentration, although this effect was short-lived. Therapeutic concentrations of vapour were achieved for all three agents by avoiding bubbling and manipulating the 'splitting ratio' lever. The Boyle's bottle vaporizer may be used with modern anaesthetic agents such as halothane, isoflurane and enflurane. However, the limitations of and variations between vaporizers should be borne in mind. An agent monitor employed at the patient end of the circuit would be an important safety feature.