A dräger service technician tested the device after the reported event without any deviation to specification.The elctronic log file was downloaded and submitted for analyses.Based on the information stored therein the case in question could be reconstructed.The log entries indicate, that a combination of a fresh gas deficit with an improperly opening auxiliary air intake valve led to the oberved ventilator failure.During downward movement of the piston the device detected that a negative pressure has been built-up to a certain level which is an indication for a fresh gas deficit.Such freh gas deficit can be caused by an unsuitable freh gas setting and/ or leakages in the patient circuit.The log entries do not allow for a more detailed analysis regading the exact root cause.However the provide evidence that the last leak test was perforemed on june 14.8 days prior to the reported event.This is against the instructions for use which advise the user to perform a leak test on a daily basis.The fabius is designed to open an auxiliary air intake valve on top of the ventilator to compensate the fresh gas deficit with ambient air.According to the log the compenstation did not happen as expected which indicates the the movement of the auxiliary air intake valve was restricted.The negative pressure further increased and the fabius finally reacted as specified by temporarily stopping the piston movement and generating a ventialtor failure alarm.In such case ventilation will resume automatically once the pressure is within the accepted range.Against the background of the technician's test results, it can be concluded there was no persistant device failure.Based on all availeble information it is seen likely that humidity has led to sticking or delayed opening of the valve.Based on experience this is caused by insufficient reprocessing (in particular drying).Traces can hardly be determined afterwards as the humidity will likely evaporate quickly.The fabius reacted as specified for this scenario.The number of similar cases is within the expected range of the respective risk assessment and thus accepted.
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