10 Monitoring FHR and FMP Using Ultrasound
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Additional Information
Artifact in Fetal Heart Rate Measurement
How to detect it and reduce its occurrence using the Avalon Fetal Monitor
The ultrasound derived FHR measurement technique in Avalon fetal monitors, like all other
ultrasound fetal monitors’ FHR measurement techniques, has limitations that can lead to
misrepresentation of the fetal heart rate pattern and potential misinterpretation of the fetal condition.
An incorrect interpretation of the trace may lead to either unnecessary interventions or to failure to
detect fetal distress and the need for intervention. Therefore, the on-going evaluation of the recorded
trace requires regular confirmation that the trace represents true FHR. Specific situations requiring
such confirmation include the following:
♦ After starting a measurement or changing a transducer
♦ After maternal position changes, for example during pushing with contractions
♦ When the tracing shows abrupt changes in baseline rate, variability, or pattern (decelerations to
accelerations) especially in the second stage of labor
♦ When the baseline maternal heart rate is within about 15 bpm of the FHR
♦ When the user is unable to determine a baseline rate and variability occurs between consecutive
contractions
There are several ways to verify the source and/or accuracy of the recorded fetal heart rate pattern.
These include:
Verification of the FHR with:
♦ An obstetric stethoscope,
♦ Ultrasound imaging, or
♦ A fetal scalp electrode
Verification of the maternal heart rate:
♦ Using pulse oximetry - for a maternal heart rate pattern displayed simultaneously with the FHR
(Cross-Channel Verification (CCV) feature),
♦ Using Maternal ECG - for a maternal heart rate pattern displayed simultaneously with the FHR
(CCV feature), or
♦ Manual determination of the maternal pulse
FHR1 EQUIP MALF or FHR2 EQUIP MALF or FHR3 EQUIP MALF INOP
displayed.
(see “Patient Alarms and INOPs” on
page 73).
FHR1 SIGNAL LOSS or FHR2 SIGNAL LOSS or FHR3 SIGNAL LOSS
INOP displayed.
FHR1 UNPLUGGED or FHR2 UNPLUGGED or FHR3 UNPLUGGED
INOP displayed.
If you suspect the transducer is malfunctioning. Test the transducer. See below.
Problem Possible Causes Solutions
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