SpO
2
Pulse Oximetry SpO2 Monitoring
6 - 8 0070- 0-0704-02 Passport V Operating Instructions
With Sat-Seconds alarm management, high and low alarm limits are set in the same way as
traditional alarm management. A Sat-Seconds limit is also set. The Sat-Seconds limit controls
the amount of time that SpO
2
saturation may be outside the set limits before an alarm
sounds. The method of calculation is as follows: the number of percentage points that the
SpO
2
saturation falls outside the alarm limit is multiplied by the number of seconds that it
remains outside the limit. This can be stated as the equation:
Sat-Seconds= Points × Seconds
Only when the Sat-Seconds limit is reached, the monitor gives a Sat-Seconds alarm. For
example, the figure below demonstrates the alarm response time with a Sat-Seconds limit set
at 50 and a low SpO
2
limit set at 90%. In this example, the patient % SpO
2
drops to 88% (2
points) and remains there for 2 seconds. Then it drops to 86% (4 points) for 3 seconds, and
then to 84% (6 points) for 6 seconds. The resulting Sat-Seconds are:
After approximately 10.9 seconds, a Sat-Second alarm would sound, because the limit of 50
Sat-Seconds would have been exceeded.
Saturation levels may fluctuate rather than remaining steady for a period of several seconds.
Often, the patient % SpO
2
may fluctuate above and below an alarm limit, re-entering the
non-alarm range several times. During such fluctuation, the monitor integrates the number of
%SpO
2
points, both positive and negative, until either the Sat-Seconds limit is reached, or the
patient %SpO
2
re-enters the non-alarm range and remains there.
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