Revision D 170 Series Monitor 5-11
2003023-001
Fetal Heart Rate Monitoring: Fetal Heart Rate Alarms
FHR Low Alarm
The simplest example of a low FHR alarm occurs when the FHR value is
continuously less than the threshold (low limit) for 30 seconds. When data
consistently violates the limit, the time-to-alarm is 30 seconds. See
Figure 5-6.
Figure 5-6. Low FHR Alarm Example
Sample Clinical Exceptions
Figure 5-7 provides an example of FHR fluctuations above and below the high
alarm limit setting.
Figure 5-7. Fluctuations Near High Alarm Limit Example
Whether or not the pattern shown in Figure 5-7 generates an alarm depends on what
percentage of the data violates the limit. The monitor evaluates the data on an on-
going basis; the methodology can be simplified as follows:
A FHR threshold alarm occurs if the FHR violates the alarm limit setting for
more time than it stays within the specified acceptable range.
The time-to-alarm increases as a greater percentage of data stays within the
specified acceptable range.
12
3
4
5
Time (minutes)
FHR (BPM)
low alarm limit
(threshold)
alarm activates
12
3
4
5
Time (minutes)
FHR (BPM)
high alarm limit
(threshold)
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