9 Monitoring SpO2
195
Alarm Delays
There is a delay between a change in the oxygen saturation at the measurement site and the
corresponding alarm indication at the monitor. This delay has two components:
• The general measurement delay time is the time between the occurrence of the saturation
change and when the new value is represented by the displayed numerical values. This
delay depends on the algorithmic processing and the averaging time configured for SpO
2
. The
longer the averaging time configured, the longer the time needed until the numerical values reflect
the change in saturation.
• The time between the displayed numerical values crossing an alarm limit and the alarm
indication on the monitor. This delay is the sum of the alarm delay time configured for SpO
2
,
plus the system alarm delay. The system alarm delay is the processing time the system needs for
any alarm to be indicated on the monitor, after the measurement has triggered the alarm. See
“Monitor Performance Specifications” on page 464 for the system alarm delay specification.
For SpO
2
high and low limit alarms, there are two different types of alarm delay time. The standard
alarm delay is set to a fixed value. The Smart Alarm Delay varies, based on an intelligent algorithm,
and can be used instead of the standard alarm delay.
The
Desat alarm always uses the standard alarm delay.
Standard Alarm Delay
The standard alarm delay time can be configured to a fixed value between 0 and 30 seconds, in
1 second steps.
Smart Alarm Delays
The Smart Alarm Delay functionality is currently not available in China or in clinical environments under SFDA control.
When Smart Alarm Delays are used, the delay before the indication of an SpO
2
high or low limit alarm
depends on the amount by which the limit is exceeded and for how long. This capability can be used to
avoid alarms when the SpO
2
values show a pattern of recovering after a limit violation.
There are three modes available, Short, Medium and Long. All modes have a minimum delay of
10 seconds. The maximum delay is 25 seconds for Short mode, 50 seconds for Medium mode and
100 seconds for Long mode.
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