Volume Ventilator Alarm Failure Case Study

A patient needed the use of a volume ventilator at his home for a respiratory ailment. While being treated by the ventilator, an alarm condition occurred. No alarm was heard in the house. Fortunately, no permanent damage occurred.

Expert Findings

After review of the documentation and evaluation of the ventilator, it was discovered that the ventilator failed preventing the audible alarm:

• The ventilator was put in alarm mode where an audible signal was observed. Sound measurements were made throughout a house to determine if the alarm was not heard.
• The ventilator did indeed have an alarm mode where no audible alarm was available.
• Investigation of the circuit diagram revealed a transistor in the audible alarm circuit went into saturation, diverting the speaker driving current.

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