Clinical Instructions For Fetal Use - GE LOGIQ 500 Advanced Reference Manual

Bioeffects

Clinical instructions for fetal use

Umbilical artery
6–10
Following are illustrative examples of clinical instructions for
fetal Doppler use which were prepared by Harold Schulman,
M.D. and John Hobbins, M.D.
To obtain a signal:
For continuous wave Doppler instrument, place the pencil probe
with appropriate conducting gel on the maternal abdomen. The
volume should be at a comfortable level and the power output
-
and gain at a mid setting. Slowly move the pencil probe by
changing the angle or location on the maternal abdomen until
the characteristic sound of the fetal umbilical flow can be heard.
This is a swishing sound with a rate usually between 120 and
160 BPM. It should be lacking in discernible clicks or sounds
similar to valve movement on cardiac auscultation. When the
image is obtained, adjust the controls in order to optimize the
image by reducing the power output to the lowest setting at
which a good quality signal is obtained. The gain setting should
also be reduced to make the signal appear crisp with minimal
background noise. If diastolic flow signals are not obtained, the
angle of the beam incident to the umbilical cord may be too high
and another area of cord should be examined to determine
whether diastolic flow is present. When a good quality signal is
obtained all the way across the display screen, the image may
be frozen.
Prior to taking measurements, the signals should be examined
to ensure that the variations in waveform size that may be
caused by fetal breathing movements are not present. Fetal
breathing movements will invalidate any measurements due to
the variations they cause in umbilical flow.
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LOGIQ 500 Advanced Reference Manual
2276614–100 Rev. 0