The device had been examined on-site but did not exhibit any new malfunctions during testing.The failure codes recorded in the error log indicated that two consecutive motor encoder checks have occurred approx.One hour after start of the concerned procedure.The service engineer decided to replace the ventilator motor unit.The device passed all tests afterwards and was returned to use.The original motor was tested in the manufacturer's lab.It was found that reversal of rotation direction was not performed with the required dynamics.The motor drives the piston up and down via a spindle.The number of rotations equals the piston hub and thus, to the volume applied by the ventilator.Motor position, rotating speed and acceleration is being measured continuously and compared with the values calculated by the software.If significant deviations are detected, a shut-down is forced to protect the patient from potentially hazardous output resulting from false piston hubs.Dräger finally concludes that the system responded as designed upon a deviation within one subsystem.Automatic ventilation was shut down for safety reasons; the user was alerted to this condition by means of a corresponding alarm.There is no comparable case known.
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