An evaluation of fourteen oxygen analysers for use in patient breathing circuits.

Fourteen in-line oxygen monitors designed for use in patient breathing circuits were assessed to determine the lifespans of their sensors when exposed to oxygen, their response times to a sudden change in oxygen concentration from 30% to 0%, the effects of exposure to nitrous oxide, and the effects of some agents and conditions commonly encountered in anaesthetic breathing systems by exposing the sensors repeatedly for three two-hour periods to 1% halothane, 2% enflurane, saturated water vapour at 37 degrees C, 5% carbon dioxide, or a continuous pressure of 40 mmHg. Under the conditions of this study all sensors but one exceeded the manufacturers' claimed lifespans, and all had clinically adequate response times to sudden hypoxic changes. None had significantly altered responses when repeatedly exposed to nitrous oxide. Water vapour was the most common cause of error for both polarographic and galvanic cell sensors, although some errors occurred with each of the test conditions; errors from all causes occurred evenly throughout the lifespans of both types of sensor. The incidence of over-read errors was approximately equal to that of under-read errors. However, clinically potentially dangerous over-read errors of greater than 6% oxygen did not occur in any of the sensors, with the exception, on some occasions, of the Datex Oxygen Analyser when exposed to saturated water vapour at 37 degrees C.