11-4
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:
% SpO
2
Seconds Sat-Seconds
2× 2= 4
4× 3= 12
6× 6= 36
Total Sat-Seconds= 52
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.
NOTE
The “SpO
2
Too Low” or “SpO
2
Too High” alarm is presented in the case that SpO
2
value violates
the alarm limits for 3 times within one minute even if the setting of Sat-Seconds is not reached.
Seconds
SpO
2
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