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8 Cards in this Set

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What is it?

The fetal Doppler is a handheld ultrasound transducer used to detect and monitor fetal heartbeat during prenatal care. An audible simulation of the fetus’s heartbeat is achieved through the Doppler effect. Some dopplers can also display the heartbeat on a monitor in beats per minute.

History

The fetal doppler was invented by Dr. Edward Hon at the Yale University School of medicine. This was the earliest report of Fetal Heart Rate monitoring (FHR), which Dr. Hon used to try to explain the causes of fetal bradycardia. In the following years, many investigators started making similar observations on heart rate and fetal distress using FHR.

History pt 2

This led to Dr. Hon and his colleges holding two international conferences in 1971 and 72 to discuss and settle on common nomenclature and standardize FHR monitoring methods. The first fetal monitors created for clinical and practical use were produced by Hammacher and Hewlett-Packard, using external tocography and phonocardiography to make the monitors less bulky and less limiting for research.

History definitions

*Bradycardia: Abnormally slow heart action. *External Tocography: procedure for recording contractions of the muscle during childbirth. *Phonocardiography: The recording of all sounds made by the heart during a heart cycle.

How does it work

The transducer probe generates sound through piezoelectric crystals, which generate change shape rapidly when a current is applied. The change in shape creates the vibrations for the sound produced by the probe at a high frequency. As the sound travels and hits boundaries, the waves travel back to the crystals on the probe, which generate electric current in response.

How does it work pt 2

The machine connected to the probe uses the speed of the waves to calculate the distance between objects and the frequency of the wave to calculate the object's movement. This movement measurement is based on the Doppler Effect. As the sound wave returns from a moving object, its frequency changes. The machine uses the changes in frequency to produce a moving image.

Advantages/Disadvantages

An advantage fetal dopplers hold over acoustic fetal stethoscopes is the electronic audio output which lets other people besides only the user to listen to the fetus’s heartbeat.


A disadvantage is the possible lower reliability of an electronic complex device due to operator or instrument error. Another disadvantage is the high cost.

Safety

Yes but FDA recommends use only by a health professional. No at home use or damage to the fetus is possible