ALARM ACTIVITY OF VENTILATORS AFTER SIMUL ATED CRITICAL EVENTS ON CMVIPPV MODE

Alarm systems of ventilators enhance detection of possible critical ev ents during artificial ventilation. Due to their significance, in some countries the alarm detection of ventilators is regulated by federal law. Up to now, no recommendations for the adjustment of alarm limits exist and only a few detailed investigations of the accuracy of alarm detection are available. Methods. The response of four commercially av ailable ventilators (Servo-ventilator 900C, Siemens, Inc.; Bennett 720 0a, Hoyer, Inc.; Veolar, Hamilton, Inc.; EVITA, Drager, Inc.) to criti cal events during artificial ventilation of a test lung were evaluated . We measured the alarm time (the time between event creation and alar m response) of ten different simulated critical events including disco nnection, differentsized leaks, failure of the gas supply, and obstruc tion at different places in the artificial airway. Discussion. All res pirators were able to recognise severe critical situations such as hos e disconnection, failure of gas supply, and total airway obstruction w ithin a short time (< 15 s). The recognition of small airway leaks was more difficult for the ventilators even when the alarm thresholds wer e close. The alarm detection of the EVITA (software 10.0 or less) unde r conditions of partial airway obstruction may be a source of risk for the patient as the machine continued supplying inspiration with press ure-limited ventilation even when the pressure threshold was reached.