Polysomnography (PSG)

PSG determines underlying sleep disorder pathology, provides qualitative and quantitative measurements associated with the disorder, and provides information on which to base the proper course of treatment. PSG is indicated for persons complaining of daytime sleepiness, fatigue, inability to stay on task, falling asleep at inappropriate times, insomnia, nocturnal awakenings, waking with gasping or choking feelings, witnessed sleep-related apneas, abnormal snoring patterns, and any other unexplained symptoms associated with disruption of normal sleeping patterns that have persisted for 6-12 months.

Instruct the patient to keep a sleep log for 1-2 weeks before the PSG.
Remind the patient that on the day of the study, caffeinated beverages, alcohol, and sedatives are not permitted.
Extra time is needed to set up and attach equipment to the patient. Typically, the PSG is recorded during the patient's normal sleep time; however, partial or extended periods of sleep deprivation may be necessary if seizure activity is suspected.
The sleep technologist records the patient's history and factors such as age, height, weight, current medications, visual problems, and history of seizures, head injuries, headaches, or strokes. The sleep log is reviewed, and a bedtime questionnaire is completed. The patient wears normal bedtime attire.
Use the following list to identify the monitoring equipment used:
1. Two sets of scalp electrodes to monitor sleep stages (EEG)
2. One electrode to the outer canthus of each eye (EOG)
3. One electrode to the chin (submental)
4. Electrodes to the legs (anterior tibialis; EMG)
5. ECG leads for heart rhythms and rates
6. Impedance monitor (respiratory effort)
7. Oral/nasal thermistor between nose and upper lip (airflow)
8. Pulse oximeter (SpO₂; O₂ sensor)
After application, interface all electrode leads with a "jack box," which contains the preamplifiers and impedance meter. From the jack box, signals are sent through additional amplifiers and filters and finally to a multichannel recorder or polygraph. The polygraph can provide a hard copy recording of all channels and signals that can be computer processed and displayed on a monitor. Electrode connections are subsequently tested for integrity and adjustments made before the patient retires.
During the recording, both audio and infrared camera video recordings are made.
Provide a bedside commode because the leads are relatively short.
When the test is completed and equipment removed from the patient, ask the patient to complete another questionnaire; score related to the patient's sleep experience during the test.
Follow guidelines in Chapter 1 for safe, effective, informed intratest care.

If seizures are a factor, up to 16 additional scalp electrodes are applied according to the International 10-20 System of Electrode Placement. The International 10-20 System of Electrode Placement is the conventional system (established in 1958) used to identify and place scalp surface electrodes for the recording of brain electrical potentials. The 10-20 System nomenclature is used to indicate that the distance between electrodes is either 10% or 20% of the front to back or right-side to left-side distance of the skull.

Procedural Alert

A home sleep study is an alternative for patients who have trouble falling asleep in a sleep laboratory. Sensors are applied in the clinic, and the patient is shown how to attach the mobile monitoring unit

Abnormal EEG recordings indicate problems with either sleep architecture (e.g., sleep onset, stages, offset) or seizure disorders.
Abnormal leg EMG is consistent with movement disorders (e.g., restless legs syndrome, nocturnal myoclonus, leg jerks).
An AHI >5 indicates sleep-disordered breathing. OSA is characterized by absence of airflow for >10 seconds despite continued respiratory effort (e.g., thoracic breathing or snoring accompanied by periods of apnea). Central sleep apnea (CSA) is characterized by absence of both airflow and respiratory effort; airflow ceases because respiratory effort is absent. Mixed sleep apnea generally begins as a central apnea and becomes obstructive apnea. Sleep apnea has been linked with cardiac arrest, strokes, pulmonary hypertension, brainstem lesions, and head trauma.
An ODI >5 is associated with oxygen desaturation, which generally occurs with an apneic event but can also occur with hypoventilation.

Pretest Patient Care

Explain test purpose and procedure. Tell the patient that these tests are done when signs and symptoms have persisted for at least 6-12 months. Caution the patient not to change their daily routine the day before the test.
Reassure the patient that lead wires, monitors, and sensors will not interfere with changes of position during sleep.
Record the patient's age, height, weight, and gender. A brief history and before- and after-bedtime questionnaires are taken.
Have the patient prepare for sleep at the normal time according to routine and discontinue any medications used to help with sleep.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

Have the patient resume usual activities and routines.
Review test results; report and record findings. Modify the nursing care plan as needed.
Explain the need for possible follow-up treatment. Treatment for insomnia may involve a combination of approaches, including cognitive behavioral therapy and pharmacologic intervention.
Explain to the patient that maintaining good sleep hygiene (e.g., getting a good night's sleep) has been shown to increase levels of leptin (a hormone produced by adipose tissue), which decreases appetite and increases metabolism.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Caffeinated beverages and alcohol can delay sleep onset or exacerbate some types of sleep disorders.
Sedatives (hypnotics) shorten sleep onset and reduce nocturnal awakenings, which may skew the results of the PSG.
Changes in daily routine on the day of the sleep study may cause false-positive or false-negative results.
During the PSG, environmental noise, lights, and temperature may have an adverse effect on the patient's ability to fall asleep.

Normal

EEG: Normal sleep onset time, sleep stages, and sleep offset (going from sleepfulness to wakefulness [i.e., awakening])
Airflow monitors: Evidence of sustained airflow throughout the night
EOG: Normal slow, rolling movements at sleep onset; rapid eye movement during REM sleep
EtCO₂: Normocapnic (35-45 mm Hg during the awake state, increasing a couple of mm Hg during sleep)
EMG: Absence of periodic leg movements or jerks
SpO₂: >90%
Snoring sensor: Absence of abnormal patterns of snoring
ECG: Absence of rhythmic disturbances, bradycardias, or tachycardias
Audio and video recordings: Absence of restless sleep, sleep walking, sleep talking, and night terrors, among other conditions
Chest impedan Evidence of sustained respiratory effort throughout night
Apnea/hypopnea index (AHI): Adults <5 apneas/hypopneas per hour (after age 60 years, <10 apneas/hypopneas per hour)
Oxygen desaturation index (ODI): Adults, <5 per hour (SpO₂<90%)

Stages of Sleep^a
Term	Electroencephalogram (EEG) Definition
Sleep onset	Transition from wakefulness to sleepfulness; usually takes at least 10 min (i.e., nonrapid eye movement [nREM], stage I)
Stage I nREM	Occurs at sleep onset; consists of low-voltage EEG with mainly theta and alpha activity; 4%-5% of sleep
Stage II nREM	Follows stage I; low-voltage EEG with sleep spindles and K complexes; 45%-55% of sleep
Stage III nREM	Consists of 20%-50% high-amplitude delta waves; referred to as delta or slow-wave sleep; 4%-6% of sleep
Stage IV nREM	Consists of 50% high-amplitude delta waves and is also called slow-wave sleep; 12%-15% of sleep
Stage REM	Low-voltage, mixed frequency; non-alpha activity with rapid eye movements, called paradoxical sleep; 20%-25% of sleep
Sleep offset	Transition from sleepfulness to wakefulness, alpha and beta activity, also called awakening

^aSleep staging is done in 30-second epochs.

section name header

Introduction ⬇

Procedure ⬆ ⬇

Clinical Implications ⬆ ⬇

Interventions ⬆ ⬇

Interfering Factors ⬆ ⬇

Reference Values ⬆