User's Manual

Fetal Monitoring
15-7
Ultrasound Monitoring
Channel 1
The ultrasound transducer sends sound waves into the uterine cavity and detects
echoes returning from objects in the path. The monitor uses auto-correlation to
analyze these echoes from moving objects, specifically the fetal heart. The rhythm
of the motion is used to compute the fetal heart rate. To produce a reliable
recording, the transducer must be positioned properly to send sound waves
directly at the fetal heart.
Ultrasound Transducer Preparation and Application
The transducer connections are color-coded and uniquely keyed.
1. Plug the ultrasound transducer (green) connector into the FHR1 (green)
connector on the front of the monitor. The groove on the transducer connector
must be aligned properly.
2. Apply a generous amount of gel over the face of the ultrasound transducer.
3. Adjust the volume as necessary to hear the fetal heart sounds while
positioning the ultrasound transducer.
4. Place the transducer on the mother’s abdomen and gently move it along the
abdomen to locate the sharpest and clearest fetal heart sounds.
5. The transducer should be held securely in place with the transducer belts
without causing discomfort to the patient.
6. Check the mother’s pulse. Be sure it does not coincide with the displayed heart
rate. If it does, the transducer may be detecting the maternal blood flow, rather
than the fetal heart beat. Reposition the transducer toward the fetal heart.
!
• To obtain consistent, reliable information, proper application of
transducers is essential.
!
• The gel is necessary to ensure that good signals are produced
by the transducer. Use enough gel to cover the flat transducer
face before it is placed on the mother’s abdomen. Add
additional gel, if necessary, to improve the signal.
!
• Remember to calibrate the monitor each time you begin a
monitoring session. Refer to Calibration on page 15-6.
!
• Keep the transducer face in contact with the abdomen. Tilt the
transducer to locate the clearest heart sounds, then reposition it
in the direction of the tilt until you hear the best signal while the
transducer is flat on the abdomen.