The investigation was carried out based on the available information and electronic device logfile of the involved anesthesia device.Based on this, the reported shut down could be understood.In case of a ventilator failure during automatic ventilation, the ventilator initiates an autonomous shutdown while changing mode to man/spont (safety mode) and generating the appropriate ventilator fail alarm.Manual ventilation remains possible, as it was in this specific case.It was found that, on the reported date of event, the device was powered on at 7:26 am and the subsequent power-on self-test (post) has been successfully completed at 7:30 am.The case in question was started at 1:37 pm using man/spont and continued in volume af mode from 1:46 pm.Amongst others, the device alarmed repeatedly for volume not attained, fg low or leak, apnea and pressure high in the following and the resulting tidal volumes were widely varying.At 1:56 pm an unexpected pressure peak of 92.3 hpa at the patient end of the breathing circuit was detected and both, negative pressures and positive pressure peaks alternated.Then, due to a too fast and too high pressure increase, the ventilator performed an emergency shutdown while autonomously changing mode to man/spont and generating the respective ventilator fail alarm according to its specifications.The case was continued using man/spont until 2:00 pm, when the device was rebooted.After successful completion of the subsequent post at 2:05 pm, ventilation was continued in pressure mode and ventilation was unremarkable until end of operation.Finally, no indication for a malfunction could be found; the device reacted as specified in this case in question.The root cause for the reported symptom most likely was an overpressure at the patient end of the circuit leading to a pressure peak and thus to the emergency shutdown of the ventilator.It is possible that the patient was coughing against the ventilator or a bronchial suction system was used leading to a pressure disturbance.
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