EDAN SONOTRAX Basic User Manual - Chapter 4 Examining

SONOTRAX Series Ultrasonic Pocket Doppler User Manual                              Examining 

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Chapter 4 Examining 

4.1 FH Examining 

Before applying the Doppler for fetal heart (FH) examining, a proper probe should be chosen. 

The 2.0 MHz obstetrical probe is optimized for deep penetration and late pregnancy. The 3.0 

MHz obstetrical probe has higher sensitivity and is optimized for early pregnancy (after 10 weeks 

gestation). 

NOTE: 

In some cases, fetal heart beats at 10 weeks gestation can not be detected due to the 

maternal physical difference and the operator’s technique. 

Perform fetal heart examining using the following procedures: 

1) Confirm the fetus’s position by hand. 

2) Determine the probable probe location for optimal FHR examining. 

3) Take out the probe and switch on the Doppler. 

4) Apply a certain amount of coupling gel to the probe faceplate and place the probe against the 

abdomen at the predetermined location. Move the probe around or tilt it until clear and 

rhythmic heart sound is heard from the headphone or speaker. At the same time, a numeric 

FHR is displayed on the LCD (except SONOTRAX Lite). 

If the Doppler works in mode 1, the numeric is the real-time heart rate, it changes continuously. 

If the Doppler works in mode 2, the numeric is the average of every 8 heart beats, it changes 

slowly. 

If the Doppler works in mode 3, press the 

  button once and start counting immediately, 

viz. count one at the moment when the button is pressed. The LCD shows a flashing heart shape 

symbol and “---”. Press the 

  button again on the 10

th

 count (after nine beat intervals). The 

Doppler calculates and displays the average FHR over the 10 beats. This rate value will not 

disappear until another measurement starts or the mode is changed.