Case report: automated machine checkout leaves an internal gas leak undetected: the need for complete checkout procedures.

We report a complete internal fresh gas flow disconnect within a Dräger Fabius GS anesthesia machine without any alarms being triggered. This was undetected primarily because of an incomplete machine checkout in which the step of ensuring proper gas flows by using a "test lung" was omitted. Machine-specific factors, however, also contributed to prevent diagnosis: (1) the machine passed its leak test because the flowmeter bobbin (i.e., floating ball) sealed the flowmeter when back pressure was applied; (2) the mechanical ventilator entrains room air, thus functioning in the absence of fresh gas flow; and (3) the electronic flow sensors functioned "appropriately" because the leak was downstream. Despite the advent of highly automated machines, manual checkout procedures remain crucial to minimizing undiagnosed failures.