A SIMPLIFIED CONCEPT FOR CONTROLLING OXYGEN MIXTURES IN THE ANESTHETIC MACHINE - BETTER, CHEAPER AND MORE USER-FRIENDLY

Modern anaesthetic machines are equipped with several safety component s to prevent delivery of hypoxic mixtures. However, such a technical d evelopment has increased the complexity of the equipment. We report a reconstructed anaesthetic machine in which a paramagnetic oxygen analy zer has provided the means to simplify the apparatus. The new machine is devoid of several components conventionally included to prevent hyp oxic mixtures: oxygen failure protection device, reservoir O-2 alarm, N2O/air selector, and proportioning system for oxygen/nitrous oxide de livery. These devices have been replaced by a simple safety system usi ng a paramagnetic oxygen analyzer at the common gas outlet, which in a feed-back system cuts off the supply of nitrous oxide whenever the ox ygen concentration falls below 25%. The simplified construction of the anaesthetic machine has important consequences for safety, cost and u ser-friendliness. Reducing the complexity of the construction also sim plifies the pre-use checkout procedure, and an efficient 5-point check list is presented for the new machine.