For the investigation the logfile was analysed.It was found that during the power-on self-test (post) repeatedly a problem was detected at the auxiliary vacuum pressure.The post was aborted and the unit was switched into operation.The ventilator again detected the faulty vacuum pressure.To prevent from damages, the system is designed to shut down automatic ventilation and to alert the user to this condition with "ventilator fail".Manual ventilation and the monitoring functions remain available to the full extent.The auxiliary vacuum pressure is needed to operate the valves that control the ventilation cycles and to keep the ventilator diaphragm in place during piston movement.If the vacuum pressure is measured out of range the system reacts with a shutdown of automatic ventilation and generation of a corresponding alarm since a dislocated or wrinkled piston diaphragm may cause significant mechanical damages to the ventilator unit.Reasons for a vacuum pressure out of range can be multiple; a pump issue, an occluded inlet filter, a leakage in the device-internal tubing; perforation of the ventilator diaphragm or issues with the sensor that measures the pressure.However it was not possible to determine the exact root cause.The number of similar cases, related to the same issue, is within the expected range of the respective risk assessment and thus accepted.
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