8 Monitoring SpO2
167
CAUTION
If you measure SpO
2
on a limb that has an inflated noninvasive blood pressure cuff, a non-pulsatile
SpO
2
INOP can occur. If the monitor is configured to suppress this alarm there may be a delay of up
to 60 seconds in indicating a critical status, such as sudden pulse loss or hypoxia.
Alarm Delays
There is a delay between a physiological event at the measurement site and the corresponding alarm at
the monitor. This delay has two components:
• The general system delay time is the time between the occurrence of the physiological event and
when this event is represented by the displayed numerical values. This delay depends on the
algorithmic processing and the configured averaging time. The longer the averaging time
configured, the longer the time needed until the numerical values reflect the physiological event.
• The time between the displayed numerical values crossing an alarm limit and the alarm indication
on the monitor. This delay is the combination of the configured alarm delay time plus the general
system alarm signal delay time.
The alarm delay time can be configured to a fixed value (between 0 and 30 seconds) or the monitor can
be configured to apply a delay based on an intelligent algorithm. See “About Smart Alarm Delays” on
page 167 for details on how this works.
See “Performance Specifications” on page 401 for delay specifications.
About Smart Alarm Delays
The Smart Alarm Delay functionality is currently not available in the U.S.A. or in clinical environments under FDA control.
The monitor can be configured to apply a delay before announcing SpO
2
limit alarms. The delay is
calculated using an intelligent algorithm. This capability can be used to suppress alarms which occur
because a limit is exceeded for a short time or by a small amount.
WARNING
Before using Smart Alarm Delays, make sure that you fully understand how the delay is applied and
what the consequences are.
The following factors are considered when calculating the delay:
• the amount by which a limit is exceeded
• the time it is exceeded for, and hence
•the speed with which the values change when a limit is exceeded
If the measured value rises, or falls, very quickly, an alarm will be announced with only a short delay. If
the value changes slowly, the delay will be longer before an alarm is announced. And if the value
changes slowly and only for a short time, an alarm may not be announced at all. Here are some specific
examples to illustrate this.
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