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Appendix: Concepts of Alarm Response
Delay
Concepts of Alarm Response Delay
As with any patient monitors, the audible and visual alarms are subject to alarm response
delay, which is composed of Alarm Condition Delay and Alarm Signal Generation Delay. Alarm
Condition Delay is the time from the occurrence of the triggering event to when the alarm
system determines the alarm condition exists. While Alarm Signal Generation Delay is the
time from the onset of an alarm condition to the generation of its alarm signal. The graphic
below is a simplified illustration of the concept of alarm response delay using a pulse
oximeter that measures SpO
2
as an example. The graphic does not reflect actual lengths of
delays.
Reference Definition
1 SaO
2
2 Alarm Limit
3 Displayed SpO
2
4 Alarm Signal Generation
SpO
2
Saturation
t Time
The Alarm Condition Delay is graphically represented as t
2
– t
1
in the figure above to show the
delay due to processing and averaging.