The evaluation of the log file revealed that the device passed the automatic system test in the morning of the date of event without deviations.In the beginning of the concerned procedure the ventilation was disturbed by leakages in the pneumatic circuit which were indicated to the user by means of corresponding alarms.After approximately one hour the system triggered a reboot of one of the microprocessors onboard the so-called therapy control unit, the subsystem which controls ventilation and gas dosage.The reboot was successfully completed after a few seconds; therapy was resumed afterwards with the last valid settings as intended.The procedure was continued for 7.5 hours without further issues.The triggering condition for the processor reboot could not be determined by log file analysis.There's no causal connection to the initial leakages.The fact that this was a sporadic occurrence only would suggest that an external disturbance may have caused the reboot e.G.An electromagnetic impulse that exceeded the immunity barriers and led to communication interrupt between the internal subsystems.A reliable conclusion however can't be drawn since the event left no footprints and the device exhibited no deviations during testing in follow-up of the event.The number of similar cases, related to the same root cause, is within the expected range of the respective risk assessment and thus accepted.
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