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To the Editor.—
The Food and Drug Administration recently investigated an incident involving an infant death attributed to a malfunctioning neonatal incubator. An Air Shields C86 Isolette incubator overheated owing to two unrelated failures: (1) The primary thermostat functioned intermittently, ie, most of the time the thermostat would function properly, turning the heater off and on to maintain the incubator temperature at the set-point temperature; but occasionally, the thermostat would "stick" in the "on" position, allowing the heater to function uncontrolled. (2) A back-up safety thermostat (mercury in glass type) was broken. Under normal conditions when the temperature reached 39.4 °C, this thermostat would have turned off the heater and sounded an alarm.The FDA investigation also revealed that the primary thermostat could exceed its recommended maximum temperature (37.2 °C) if allowed to drift out of calibration. Analysis shows further that backup safety thermostats can malfunction from mercury column separation
Haffner ME. Malfunction of a Neonatal Incubator. JAMA. 1982;247(17):2372. doi:10.1001/jama.1982.03320420028023