11 Monitoring FHR and FMP Using Ultrasound
Testing Ultrasound Transducers
If any of the following tests fail, repeat the test using another transducer. If the second transducer
passes the tests, confirming that the first transducer is defective, contact your service personnel.
If the second transducer also fails the tests, contact your service personnel.
You can test all ultrasound transducers, including the cableless ones, as described above.
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. Thus, the on-going evaluation of the recorded trace
requires regular confirmation that the trace represents the 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
To test an ultrasound transducer:
Switch on the monitor and the
Connect the transducer to the fetal
Select the fetal heart sound for this
Increase the loudspeaker volume
to an audible level.
Holding the transducer in one
hand, move your other hand
repeatedly towards and then away
from the surface.
Check that a noise is heard from