RST Polysomnographic Recording Procedures Questions and Answers — Questions and Answers
Question 1: During a polysomnogram, the technologist observes a persistent, rhythmic 60 Hz waveform across multiple EEG and EOG channels. Which of the following is the MOST likely cause of this artifact?
- Sweat artifact from the patient
- Improper grounding of electrical equipment (Correct answer)
- Patient's heartbeat (ECG artifact)
- Movement of the patient's head on the pillow
Correct answer: Improper grounding of electrical equipment
A rhythmic 60 Hz waveform is the characteristic signature of electrical interference from the alternating current (AC) power lines used in North America. This type of artifact often indicates an issue with the electrical grounding of the polysomnograph or other nearby devices, which allows the electrical field to interfere with the sensitive bio-potential recordings.
Question 2: According to AASM guidelines for recording chin EMG, what is the correct placement for the three recommended electrodes?
- One on the tip of the chin, and two on the masseter muscles bilaterally.
- Two on the submental muscle group and one on the mentalis muscle. (Correct answer)
- One under the left jawline, one under the right jawline, and one on the forehead as a reference.
- Three electrodes placed in a line directly under the inferior edge of the mandible.
Correct answer: Two on the submental muscle group and one on the mentalis muscle.
The AASM recommends placing three electrodes to record chin EMG: one in the midline on the mentalis muscle (1 cm above the inferior edge of the mandible), and two on the submental muscles (one 2 cm to the left of midline and 2 cm below the inferior edge, and one in the same position on the right). This arrangement allows for a primary and backup derivation to monitor muscle atonia during REM sleep.
Question 3: A technologist is preparing to place respiratory effort belts on an adult patient. To ensure an accurate recording of paradoxical breathing, the thoracic belt should be placed at the level of the:
- Umbilicus
- Lower costal margin
- Axilla (under the armpits) (Correct answer)
- Clavicle
Correct answer: Axilla (under the armpits)
The recommended placement for the thoracic respiratory effort belt is high on the chest, at or just below the level of the axilla (under the armpits). The abdominal belt is placed at the level of the umbilicus. This separation is crucial for clearly identifying paradoxical respiratory effort, where the chest and abdomen move in opposite directions, a key sign of obstructive respiratory events.
Question 4: During physiological calibrations, the technologist observes that when the patient looks to the left, the E1 (left eye) and E2 (right eye) channels produce in-phase deflections. What does this indicate?
- A normal and expected physiological response.
- A reversed electrode placement in the E1 or E2 derivation. (Correct answer)
- The patient is not following instructions correctly.
- EEG artifact is contaminating the EOG channels.
Correct answer: A reversed electrode placement in the E1 or E2 derivation.
With standard EOG electrode placement (E1 below the left outer canthus, E2 above the right outer canthus, both referenced to M2/M1), conjugate eye movements should produce out-of-phase deflections. For example, looking left causes a negative deflection in E1 and a positive deflection in E2. If the signals are in-phase, it suggests one of the exploring electrodes may be referenced incorrectly or placed on the wrong side, requiring troubleshooting before the study begins.
Question 5: Which of the following describes the primary purpose of using the International 10-20 System for EEG electrode placement in polysomnography?
- To minimize the total number of electrodes required for the study.
- To ensure electrode placement is standardized and reproducible across different patients and labs. (Correct answer)
- To place electrodes directly over specific anatomical sleep centers of the brain.
- To reduce the impedance levels of the scalp electrodes.
Correct answer: To ensure electrode placement is standardized and reproducible across different patients and labs.
The International 10-20 System is a standardized method that uses specific anatomical landmarks on the skull (nasion, inion, and preauricular points) to ensure that electrode placement is proportional to the size and shape of the head. This standardization allows for consistency and reproducibility of recordings, making it possible to compare data collected from different patients and in different sleep centers.
Question 6: A patient's recording shows an abrupt shift in EEG frequency lasting 5 seconds, accompanied by a sudden increase in chin EMG amplitude during Stage N2 sleep. According to AASM scoring criteria, this event would most likely be scored as a(n):
- Sleep spindle
- K-complex
- Arousal (Correct answer)
- Epoch of wakefulness
Correct answer: Arousal
The AASM defines an arousal during NREM sleep as an abrupt shift in EEG frequency (to alpha, theta, and/or frequencies greater than 16 Hz) that lasts for at least 3 seconds. For an arousal to be scored from REM sleep, there must also be a concurrent increase in submental EMG lasting at least 1 second. The scenario describes the criteria for an arousal from NREM sleep.
RST Polysomnographic Recording Procedures Questions and Answers
During a polysomnogram, the technologist observes a persistent, rhythmic 60 Hz waveform across multiple EEG and EOG channels.
Which of the following is the MOST likely cause of this artifact?