GE Corometrics 170 Series, Operator'S Manual

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5-2 170 Series Monitor Revision D
2003023-001
Fetal Heart Rate Monitoring: Ultrasound (External Method)
Ultrasound (External Method)
Methodology
An ultrasound transducer placed on the maternal abdomen is used to direct an
ultrasonic beam toward the fetal heart; the transducer detects Doppler shifted
frequency changes in echoes created by moving cardiac structures. An
autocorrelation process is used to determine the time interval between successive
cardiac cycles.
The fetal heart rate is displayed in BPM and continuously plotted on the strip chart
recorder paper.
GE Medical Systems Information Technologies offers two styles of ultrasound
transducers: loop-style and button-style. Both styles are discussed in the “Maternal/
Fetal Monitoring Operator’s Manual” .
Fetal Movement Detection
NOTE:
The fetal movement detection
option is associated with the primary
ultrasound connector only. For Models
172 and 174 (dual ultrasound), FMD is
not available for the secondary
ultrasound connector.
Fetal movement detection (FMD) is an option which can be installed in your
monitor to function with the ultrasound channel. Contact your Service
Representative for information about purchasing this option.
Methodology
Fetal movement detection is designed to detect gross fetal body movements and
body movements with associated limb movement. GE Medical Systems
Information Technologies defines “gross fetal body movement” as the “extension,
flexion, or rolling over of the fetal trunk about the longitudinal axis of the body and
associated limb movements.” Movements of the extremities alone
may not be
detected. Eye movements will not be detected.
CAUTION
FALSE DETECTION—The following may be automatically
detected as fetal movement: transducer movement and maternal
movement such as coughing, laughing, repositioning, mother
poking her abdomen, in addition to emesis, fetal hiccups, or twins.
During fetal sleep, or in the event of a fetal demise, some of these
detected movements may be confused with fetal movement.
Enabling/Disabling Fetal Movement Detection
Fetal movement detection is enabled/disabled from a service setup mode. Refer to
the
“170 Series Service Manual” for more information.