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Traditional 510(k) of Fetal & Maternal Monitor
F15 Series Fetal & Maternal Monitor User Manual
electrode to obtain precise FHR with direct fetal ECG as the signal source.
(4) Erratic Traces / Drop out
When the fetal heart moves partially out of the ultrasound wave path, the transducer receives mixed or
weak signals, and thereby the monitor presents erratic traces. When the fetal heart moves fully out of
the path, inadequate consecutive and periodic signals are received, and no trace is represented.
Erratic traces and transitory episodes of drop out are common, especially when the fetus or/and
mother move(s). If they exist for an extended period, it indicates that the transducer is not aimed at the
fetus. Repositioning of the transducer is needed.
(5) Switching to maternal heart rate
When the fetal heart moves partly or fully out of the ultrasound beam, the transducer receives weak
fetal heart signal and other strong signal (usually maternal heart signal). After the mixed signals are
transferred to the monitor, as the fetal heart signal is too weak or lost, the maternal heart signal plays a
leading role and the monitor picks up and displays the maternal heart rate.
When the maternal heart rate is relatively low, the switch to the maternal heart rate may simulate an
FHR deceleration.
When the maternal heart rate is relatively high, the switch to the maternal heart rate may simulate a
normal fetal heart rate pattern, which may cover FHR deceleration or fetal demise.
With twins or multiple fetuses, the potential to experience these artifacts is increased.
The following points shall be noticed in order to keep a good capture effect of ultrasound
transducer for a long time:
1.
If the fetal heart sound is heard from loudspeaker, while the FHR traces in chaos, or not
stable. This is because the transducer is placed at back of fetus, please adjust the position of
transducer.
The FHR trace is not recorded well after fetal movement or change of mother's position. This
2.
is because the movement of the location of fetal heart which makes the ultrasound
transducer deviated from the fetal heart.
3.
The FHR trace is in chaos or interrupted during uterine contraction. This is because the fetus
moves downward at that time. In order to avoid the situation, please fix the transducer at the
position 1-2 cm lower than the transducer position when there are no contractions.
4.
Apical abdomen may make fetal heart transducer move easily and difficult to record FHR
trace, thus please fix the transducer in caution and adjust it in time.
5.
Urine increase makes distention of bladder and then leads to deviation of ultrasound
transducer from the fetal heart, thus please remind the patient to urinate.
6.
Long time monitoring makes the couplant decrease, so that the ultrasound transducer cannot
work normally, thus please supplement the couplant.
7.
If the fetus is in occipitoposterior position due to fetal descent and rotation, and fetal back
moves to the direction of maternal back, making monitoring become difficult. In this case
please move the ultrasound transducer to the middle of abdomen below navel.
8.
If the obvious fetal heart deceleration is heard, while the FHR trace display or record is not
consistent with the sound, the sound from loudspeaker shall prevail, on the premise that the
sound is indeed from the fetus, not mother by confirmation in other ways.
9.
If the monitor alarms automatically, besides considering the fetus is in danger, the ultrasound
transducer deviating from the optimum position should also be taken into consideration.
A8.3 Audio Output and Screen Reading
In most instances, the audio output from the monitor speaker corresponds to the readings presented
on the monitor screen. But occasionally the fetal heart sound may differ from the trace and numeric.
When the fetal heart moves partially out of the ultrasound wave path, the transducer receives weaker
FHR signal and other stronger signals (usually maternal heart/pulse rate). After the signals are
transmitted to the monitor, the audio system and the video system of the monitor process the signals
separately. On one hand, the audio circuit filters the low-frequency signals and gives audio output of
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