The investigation was based on evaluation of the electronic log file.A sporadic malfunction of a cpu board which controls the device-internal communication between user interface and vgc (ventilation and gas controller) was identified to be root cause of the reported failure.This leads to a shutdown of the ventilator and gas mixer.In this situation, the device automatically switches to monitoring mode while alarming the user to this condition by means of a corresponding alarm.Manual ventilation with emergency oxygen dosage remains possible including the application of anesthetic gas as well.The monitoring functionality remains unaffected.Dräger finally concludes, that the device has reacted according to its safety concept and has performed an emergency shutdown of the affected components accompanied by the respective alarms.Similar cases are known, however, the exact failure mechanism could not be determined during in-depth analysis.It was only possible to narrow down the root cause to the respective pcb.The fact that the identical type of board is used in the workstation twice and does not exhibit malfunctions in the second application periphery makes a general design issue rather unlikely.A reasonable explanation would be electrostatic discharge of the user during interaction with the device or any other kind of electromagnetic disturbance that exceeds the immunity barriers of the device.The primus was developed in compliance to the requirements of (b)(4).The number of similar cases, related to the same root cause, is within the expected range of the respective risk assessment and thus accepted.
|