Norm of Polysomnography (PSG, Cardiopulmonary Sleep Study, CPAP Titration Study, Multiple Sleep Latency Test, MSLT, Sleep Apnea Study, Sleep Oximetry, Sleep Study)
No abnormal patterns of sleep or breathing.
Usage of Polysomnography (PSG, Cardiopulmonary Sleep Study, CPAP Titration Study, Multiple Sleep Latency Test, MSLT, Sleep Apnea Study, Sleep Oximetry, Sleep Study)
Routinely indicated for the diagnosis of sleep-related breathing disorders (such as obstructive sleep apnea), suspicion of periodic limb movement sleep disorders, narcolepsy, evaluation of violent sleep behaviors, and in certain atypical parasomnias. Also part of a CPAP titration study (treatment for obstructive sleep apnea), narcolepsy. May also be used to help diagnose disorders of arousal (sleepwalking, night terrors), rapid eye movement (REM) behavioral disorder, dissociative disorders, nocturnal seizures, nocturnal reflux, and nocturnal pain syndromes.
Description of Polysomnography (PSG, Cardiopulmonary Sleep Study, CPAP Titration Study, Multiple Sleep Latency Test, MSLT, Sleep Apnea Study, Sleep Oximetry, Sleep Study)
Polysomnography (PSG) is a procedure that takes recordings of the electric potentials generated by the cerebral cortex of the brain during sleep. Electrical potentials demonstrated on PSG are of six types: (1) those generated by eye movements, (2) surface electrical potentials generated by chin muscle activity, (3) surface electrical potentials generated by the heart, (4) surface electrical potentials generated by the muscles in the leg (anterior tibalis), (5) nasal and oral airflow (each separately or combined), and (6) respiratory effort of chest and abdomen by piezoelectric or inductance belts. In special instances additional sensors are placed either on the head or on the abdomen, or are used to measure penile erections. This study can be coordinated with a multiple sleep latency test when an evaluation of excessive daytime sleepiness (that is, narcolepsy) is desired. The use of computerized digital monitoring provides objectivity in scoring of sleep-related events.
Professional Considerations of Polysomnography (PSG, Cardiopulmonary Sleep Study, CPAP Titration Study, Multiple Sleep Latency Test, MSLT, Sleep Apnea Study, Sleep Oximetry, Sleep Study)
Consent form is NOT required.
- See Client and Family Teaching.
- Document the client's current medications, and his or her height and weight.
- Verify with the physician whether certain medications should be withheld before the test.
- Review and complete the pretest questionnaire with the client.
- Sensor placement:
- a. The client sits on a bed or chair and electrodes are placed on the scalp (see the EEG description), around the eyes, and under the chin.
- b. The airflow monitors are placed near the mouth and nose, and the respiratory belts are placed around the chest and abdomen.
- c. Electrodes are placed on the chest to measure the ECG and on the legs to measure movements. For nocturnal penile tumescence testing, a mercury strain gauge will be placed at the base and tip of the penile shaft.
- d. Other sensors, such as a pH probe, are placed as necessary.
- The client is asked to follow several commands to ensure that the sensors are functioning properly. This includes eye blinking, looking right, looking left, breath holding, right and left leg movements. This is known as “biocalibration.”
- The client then sleeps, and the PSG recordings are taken. A technician is continuously monitoring the recordings and client to detect lead detachment. For nocturnal penile tumescence testing, pressure is placed on the head of the penis with a pressure plate to determine at what pressure the penis will buckle.
- a. The data obtained from a polysomnogram include the amount of sleep during the test, the amount of each stage of sleep, any events occurring during sleep, the number of arousals, the number of respiratory events, and the degree of desaturation.
- b. Apneas are defined as a complete cessation of breathing, whereas hypopneas are a partial cessation of breathing. These are usually reported as the number of respiratory events (apneas plus hypopneas) for an hour. This is known as the RDI, respiratory distress index, or the AHI, apnea hypopnea index.
- CPAP titration studies:
- a. CPAP (continuous positive air pressure) is a treatment for obstructive sleep apnea and is essentially an air splint. Room air is blown through a mask covering the nose. The air pressure opens the posterior area of the pharynx eliminating the obstruction and snoring.
- b. The air pressure is titrated throughout the night, usually being slowly increased until both the obstructive respiratory events and the snoring are eliminated.
- c. Occasionally a bi-level machine that provides separate inspiratory and expiratory pressures is used.
- “Split-night” studies:
- a. In these studies the first half of the night is used to confirm the existence of significant sleep-disordered breathing. The second half of the night is used to titrate CPAP. The use of “split-night” studies is still controversial. Not all laboratories will perform them.
- The multiple sleep latency test (MSLT):
- a. The MSLT measures the degree of daytime sleepiness.
- b. Usually only the brain waves (EEG), eye movements (EOG), chin muscle activity (EMG), and heart activity (ECG) are measured during the (MSLT).
- c. The MSLT consists of five naps taken throughout the day, each 2 hours apart.
- d. The client is given up to 20 minutes to fall asleep on each nap. If the client falls asleep, he or she is given 15 minutes to sleep.
- e. Two results are obtained: The first is the average time to fall asleep on the five naps, known as the “mean sleep latency.” The second is the number of naps on which REM is seen, known as “sleep-onset REMs.”
- The various sensors are removed, and the conductive medium is removed from the scalp.
- Every sleep lab should have facilities available for a client's morning toilet.
Client and Family Teaching
- Often a pretest questionnaire is filled out the night of this study or mailed to the client before the study.
- You will sleep all night in the sleep lab, and a videotape will be taken of you while you sleep. If the PSG will be followed by a multiple sleep latency test, you will spend the day in the sleep laboratory.
- You will have wires and sensors attached to you, which are needed to perform the sleep study. The wires and sensors receive signals from your brain waves, muscle movement, heart, and breathing patterns that help evaluate your sleep patterns.
- For clients who will have a CPAP titration study: A CPAP mask might be used for part or all of the test to determine whether it will help reduce sleep apnea. This mask fits very snugly over your nose and mouth. It delivers air into your lungs under pressure, and so it might be uncomfortable until you get used to it. You will be able to select the mask that is most comfortable for you.
- You will be able to perform normal daily activities after the test.
- Your test results will be sent to your referring physician, who will explain the results to you.
Factors That Affect Results
- The use of caffeine or other stimulants before the test.
- The client's normal sleep-wake cycle.
- The client's information before the study and comfort sleeping in an unusual situation.
- Nocturnal penile tumescence testing results may be inconclusive because of the client's anxiety, embarrassment, or startle response during testing, as well as sleep disorders that cause a reduction in the amount of REM-type sleep. Most penile nocturnal erections occur during REM sleep.
- CPAP titration studies: A client's success in using CPAP is highly dependent on the skill of the sleep technician. The degree of client education about CPAP before the study of CPAP is a factor that can affect how well the client is able to tolerate the CPAP mask while sleeping. The technicians should be aware of the presence of any claustrophobia or difficulties the client might have by having things on the face.
- Even moderate weight reduction reduces the incidence of sleep-disordered breathing in obese clients with obstructive sleep apnea.