EFM - Electronic Fetal Monitoring Fetal Monitoring Equipment Technology Questions and Answers — Questions and Answers
Question 1: A laboring patient with a high BMI is having frequent periods of fetal heart rate signal loss with an external ultrasound transducer. Which of the following actions is MOST appropriate to obtain a more accurate and continuous fetal heart rate tracing?
- Increase the amount of ultrasound gel and readjust the belt.
- Apply a fetal scalp electrode (FSE), assuming there are no contraindications. (Correct answer)
- Reposition the patient onto her left side.
- Administer a fluid bolus to the mother.
Correct answer: Apply a fetal scalp electrode (FSE), assuming there are no contraindications.
Internal fetal monitoring with a fetal scalp electrode (FSE) provides a more direct and accurate measurement of the fetal heart rate, bypassing subcutaneous tissue that can interfere with the ultrasound signal, which is common in patients with a high BMI. It is the most appropriate step when external monitoring is inadequate and a more precise tracing is required, provided the membranes are ruptured and no contraindications exist.
Question 2: The tocodynamometer is correctly placed on the maternal abdomen to measure uterine contractions. What aspect of uterine activity does this external device measure LEAST accurately?
- Frequency
- Duration
- Intensity (Correct answer)
- Resting tone
Correct answer: Intensity
The tocodynamometer (toco) is a pressure-sensitive device that measures the frequency and duration of uterine contractions with reasonable accuracy. However, it provides only a relative measure of contraction intensity because the reading is influenced by factors like maternal size, position, and belt tightness. An Intrauterine Pressure Catheter (IUPC) is required for an accurate quantitative measurement of intensity.
Question 3: An ultrasound transducer used for external fetal monitoring functions based on which technological principle?
- Magnetic resonance imaging
- Electrocautery
- Doppler effect (Correct answer)
- Bioelectrical impedance
Correct answer: Doppler effect
External fetal monitors use an ultrasound transducer that emits high-frequency sound waves and detects changes in their frequency as they reflect off the moving fetal heart structures. This phenomenon is known as the Doppler effect, which allows the machine to calculate and display the fetal heart rate.
Question 4: While troubleshooting an erratic fetal heart rate tracing from a fetal scalp electrode (FSE), the nurse observes a regular, repeating artifact on the monitor strip that corresponds with a 60-cycle pattern. What is the most likely source of this interference?
- Maternal movement
- Fetal hiccups
- Improper FSE attachment
- Electrical interference from other equipment (Correct answer)
Correct answer: Electrical interference from other equipment
A 60-cycle (or 50-cycle, depending on the region's power standard) artifact is a classic sign of electrical interference. This can be caused by other electrical devices in the room, poor grounding of the fetal monitor, or faulty cables. It creates a very regular, sawtooth-like pattern on the tracing that is distinct from physiological signals.
Question 5: For internal monitoring of uterine contractions, an Intrauterine Pressure Catheter (IUPC) is inserted. Which of the following is a prerequisite for its placement?
- The fetus must be in a vertex presentation.
- The patient must have an epidural in place.
- The cervix must be fully dilated.
- The amniotic membranes must be ruptured. (Correct answer)
Correct answer: The amniotic membranes must be ruptured.
An IUPC is a flexible catheter that is placed inside the uterine cavity, alongside the fetus, to directly measure the pressure generated by contractions. To insert the catheter into the uterus, the amniotic sac must be broken (ruptured membranes).
Question 6: Which of the following describes the signal processing function of an external fetal monitor when calculating the fetal heart rate from the Doppler ultrasound signal?
- It directly measures the R-R interval of the fetal ECG.
- It uses autocorrelation to detect the periodic signal of the fetal heart. (Correct answer)
- It counts the number of uterine contractions over ten minutes.
- It measures the electrical potential of the maternal abdominal muscles.
Correct answer: It uses autocorrelation to detect the periodic signal of the fetal heart.
The ultrasound transducer picks up many sounds from the maternal abdomen. The monitor's software uses a signal processing technique called autocorrelation. This method identifies the repetitive, periodic signal characteristic of the fetal heartbeat and calculates the rate, distinguishing it from other background noises and maternal signals.
EFM - Electronic Fetal Monitoring Fetal Monitoring Equipment Technology Questions and Answers
A laboring patient with a high BMI is having frequent periods of fetal heart rate signal loss with an external ultrasound transducer.
Which of the following actions is MOST appropriate to obtain a more accurate and continuous fetal heart rate tracing?