Naloxone and acid-base balance in man.

Sir,—I read Dr Paymaster's letter (1978) with interest as I have encountered similar difficulties with the Cape Waine, Mark III Anaesthetic Machine. Here again there is a "push-pull" switch situated on the front panel of the machine for the delivery of emergency oxygen. This button has been left pushed to the "on" position after use and this has not been noticed by another anaesthetist using the machine immediately afterwards. The position of the switch is a hazard. Located at the front of the machine, it is liable to be pushed to the "on" position by any member of the theatre staff who leans against the machine. The switch is noiseless and the anaesthetist may be unaware that a high concentration of oxygen is being delivered to the patient. Two cases of awareness during anaesthesia have occurred as a result of this problem. Many similar incidents must have occurred and I would support the suggestion of a warning device to guard against the machine inadvertently delivering 100% oxygen. This problem has been notified to Cape Waine Ltd, who propose the fitting of a metal shroud to prevent accidental activation of the emergency oxygen switch.