Based on the analysis of the device logfile, the case could be reconstructed.It was found that the device forced a shutdown of automatic ventilation due to a detected wrong motor position.The motor speed is being monitored continuously; speed fluctuations caused e.G.By an abraded collector disc will result in a deviation between measured and expected piston position.To prevent from damages, the system is designed to shut down automatic ventilation and to alert the user to this condition by means of a corresponding alarm.Manual ventilation and the monitoring functions remain available to the full extent.The log analysis revealed no indications for a general motor- or motor control problem.Since there were no problems observed during piston referenciation during power-on self-test either, a motor failure seems unlikely.Thus, most likely foreign objects in the light barrier or a contaminated encoder disc was disturbing the correct detection of the motor position and in consequence to the reported symptom.Dräger finally concludes that the device behaved as specified upon the detected issue; no patient consequences have been reported.The device was inspected in follow-up to the event and no indications for a technical device failure were found either.After testing, the device was returned back to use, and no further problems have been reported.The number of similar cases, related to the same phenomenon, is within the expected range of the respective risk assessment and thus accepted.
|