• H J Bender, H Frankenberger, C Ryll, and M D Albrecht.
• Institut für Anaesthesiologie und operative Intensivmedizin, Klinikum Mannheim der Universität Heidelberg.
• Anaesthesist. 1993 Jun 1;42(6):365-75.

AbstractAlarm systems of ventilators enhance detection of possible critical events 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 available ventilators (Servoventilator 900C, Siemens, Inc.; Bennett 7200a, Hoyer, Inc.; Veolar, Hamilton, Inc.; EVITA, Dräger, Inc.) to critical events during artificial ventilation of a test lung were evaluated. We measured the alarm time (the time between event creation and alarm response) of ten different simulated critical events including disconnection, differentisized leaks, failure of the gas supply, and obstruction at different places in the artificial airway. DISCUSSION. All respirators were able to recognise severe critical situations such as hose disconnection, failure of gas supply, and total airway obstruction within a short time (< 15 s). The recognition of small airway leaks was more difficult for the ventilators even when the alarm thresholds were close. The alarm detection of the EVITA (software 10.0 or less) under conditions of partial airway obstruction may be a source of risk for the patient as the machine continued supplying inspiration with pressure-limited ventilation even when the pressure threshold was reached.

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