INTRODUCTION — In-laboratory, attended polysomnography (PSG) is a diagnostic test for sleep-related breathing disorders, and it is also used in conjunction with the clinical history and other tests to diagnose a variety of additional sleep disorders, including narcolepsy, sleep-related movement disorders, and certain parasomnias. During PSG, the patient sleeps while connected to a variety of monitoring devices that record physiologic variables. Patterns of physiologic abnormalities during sleep may be diagnostic of sleep-disordered breathing as well as many other sleep disorders.
In selected patients, the diagnostic evaluation for obstructive sleep apnea (OSA) may be performed at home without a technician in attendance. Home sleep apnea testing is only useful for the diagnosis of OSA in selected patients; it is not a substitute for PSG when other sleep disorders are suspected. (See "Home sleep apnea testing for obstructive sleep apnea in adults".)
This topic provides an overview of the performance of in-laboratory PSG in adults with suspected sleep disorders. The diagnosis of specific sleep disorders, and the role of PSG in the diagnostic evaluation of sleep disorders, is covered in individual disease-based topic reviews. An overview of PSG in infants and children is presented separately. (See "Overview of polysomnography in infants and children".)
TECHNIQUE
Preparation — Consumption of alcohol or caffeine prior to polysomnography (PSG) may alter the nature and severity of the underlying sleep disorder that is being measured by PSG. As examples, alcohol may exacerbate obstructive sleep apnea (OSA) and alter sleep architecture, while caffeine may contribute to insomnia and sleep fragmentation.
Patients should abstain from caffeine in the afternoon and evening of the day on which PSG is planned. Alcohol is a more complex issue when PSG is being performed for suspected OSA because the absence of alcohol on the night of PSG could yield a false negative result if the patient habitually consumes alcohol in the evening. Ultimately, however, it is neither safe nor practical to encourage patients to consume alcohol prior to presenting to the sleep laboratory. Portable monitoring may be an option for some patients if alcohol is felt to be a significant factor in their clinical presentation and the use of alcohol is unlikely to change. (See "Home sleep apnea testing for obstructive sleep apnea in adults".)
Patients with suspected OSA should continue their usual medications on the night of the PSG, including sleep aids. The medications should be recorded by the technician so that the results can be optimally interpreted. This is particularly true if benzodiazepines or opioids are among the medications, since these medications may exacerbate sleep-disordered breathing.
For patients with suspected OSA who have a history of severe insomnia, especially when sleeping in a new environment, or are very nervous about sleeping in the sleep lab, we may prescribe zolpidem to take the evening of the PSG if there are no contraindications to this medication. Zolpidem is a sleep aid that improves sleep continuity and quality, thereby improving the quality of PSG without exacerbating sleep apnea [1]. Patients who have never taken zolpidem in the past should try the medicine at home during one of the nights prior to PSG in order to assess their response to it. If it is effective, patients may bring it with them on the night of the study. Sleeping medication should be taken once the patient is in the lab and not prior to coming to the lab.
Any patient who takes a sedative and then wants to leave before the completion of the study should be encouraged to remain in the laboratory until the morning, even if the patient insists that the monitoring equipment be removed. The patient should not be allowed to drive home in the middle of the night under the influence of the sedative. The US Food and Drug Administration (FDA) recommends that patients avoid driving the day after using the extended release formulation of zolpidem [2,3]. (See "Pharmacotherapy for insomnia in adults", section on 'Benzodiazepine receptor agonists'.)
When PSG is being performed for purposes other than the diagnosis of sleep-related breathing disorders, the protocol for medications may differ. As an example, patients being evaluated for narcolepsy with PSG followed by a multiple sleep latency test (MSLT) must discontinue stimulants at least one to two weeks before testing to avoid false positive and false negative results; other psychoactive medications should be discontinued at least two weeks, and preferably four weeks, before testing if it is safe to do so. Antidepressants can inhibit rapid eye movement (REM) sleep. In addition, a two-week sleep diary including bedtimes, wake times, estimated time of sleep, and naps should be recorded prior to the MSLT. (See "Quantifying sleepiness", section on 'Multiple sleep latency test (MSLT)' and "Clinical features and diagnosis of narcolepsy in adults", section on 'Diagnostic evaluation'.)
For patient safety reasons, discontinuation of medications before sleep testing should be discussed with the prescribing clinician. It may not always be clinically feasible to discontinue some psychoactive medications. These medications should be clearly documented in PSG/MSLT reports.
For patients that are particularly anxious about having a sleep study, it may be helpful for them to take a brief tour of the laboratory before the study is scheduled. It may also be helpful for a family member or friend to accompany them during the set-up. Patients can be encouraged to bring their own pillow if they use a special pillow to sleep.
Protocols
General considerations — Patients are connected to a variety of monitoring devices during PSG (figure 1). The sleeping room is usually equipped with an infrared camera and audio system that allows the technologist to see, hear, and communicate with the patient without entering the bedroom. There is also a separate bathroom for the patient to use.
The technologist periodically documents relevant information as the study proceeds. This usually includes the heart rate, respiratory rate, oxygen saturation, presence or absence of snoring and its volume, body position, and any abnormal movements or vocalizations. When the study includes a continuous positive airway pressure (CPAP) titration, the technologist also documents which masks are tried and the reasons for changing. The pressure changes and mask leak should also be documented over the course of the night. (See "Mode selection for titration of positive airway pressure in adults with obstructive sleep apnea".)
Physiologic variables are recorded digitally on a computerized system while the patient sleeps and during any intervening wakefulness. Following collection, the data are scored manually by a technician who identifies physiologic events, stages of sleep, and wakefulness. Modern systems provide computer assistance by tabulating and collating the scored data. Software integrates video images of the patient onto the polysomnographic recordings.
Synchronized digital video allows parasomnias and other movement disorders to be detected. Abnormal movements during sleep should be documented, including the exact time, so that the stage of sleep during which the event occurred can be assessed. (See "Polysomnography in the evaluation of abnormal movements during sleep".)
Split-night protocol — There is a growing trend to perform a split-night protocol when there is high clinical suspicion for OSA. During a split-night study, the diagnosis of OSA is established during the first portion of the study and the amount of positive airway pressure (PAP) that is necessary to prevent upper airway collapse during sleep is determined during the remaining portion.
According to the American Academy of Sleep Medicine's (AASM) practice parameters for PSG and related procedures, a split-night study is a valid alternative to full-night diagnostic PSG followed by a second full night of PAP titration, if the following criteria are met [4]:
●An apnea-hypopnea index (AHI) consistent with moderate to severe OSA is documented during ≥2 hours of sleep.
●There are ≥3 hours of the study remaining during which PAP titration may be conducted, since obstructive events can worsen as the night progresses.
The goal of the PAP titration portion of the PSG study is elimination or near elimination of obstructive events with PAP during rapid eye movement (REM) and non-REM (NREM) sleep. Ideally this should include REM sleep in the supine position when apneas are most likely to occur.
A second full-night PSG may be performed for titration of PAP if these criteria are not met [5]. Alternatively, the patient may be prescribed an auto-titrating CPAP with a range of treatment pressures at home instead of returning for an in-laboratory titration study. If the patient has had a partial but incomplete titration, the information from the titration can be used to help set the range of pressures for the auto-titrating CPAP. For patients with very severe oxygen desaturation during the study who are started on auto-titrating CPAP, it may be relevant to obtain an overnight pulse oximetry study with the patient on the optimal pressure range. (See "Titration of positive airway pressure therapy for adults with obstructive sleep apnea".)
Split-night studies can provide an accurate appraisal of disease severity and establishes the correct positive airway pressure in a single night in the majority of patients [6]. Overall, split-night PSG appears to be cost effective [7,8]. It decreases healthcare costs compared with doing two separate in-laboratory studies for diagnosis and treatment of OSA, minimizes scheduling delays, and does not adversely affect compliance [9].
Daytime studies — Daytime PSG may be used for night shift workers or other individuals who are usually awake at night and asleep during the day. The protocol and duration of the study are the same as those performed at night.
INDICATIONS — The most common indications for polysomnography (PSG) in adults include diagnostic evaluation of suspected sleep-disordered breathing including obstructive sleep apnea (OSA), titration of positive airway pressure, and assessment of the adequacy of therapy that is already being used [5]:
●PSG (as opposed to home sleep apnea testing) is particularly important in the diagnostic evaluation of patients with advanced cardiopulmonary disease, who have a higher likelihood of central apneas, and in patients suspected of having other comorbid sleep disorders. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults", section on 'Diagnostic evaluation'.)
●Both full-night and split-night studies are used to titrate positive airway pressure therapy in patients with OSA. (See "Titration of positive airway pressure therapy for adults with obstructive sleep apnea".)
●PSG can assess the efficacy of therapy when there is concern that the patient is not adequately treated with the currently prescribed therapy, or when there has been significant weight loss or gain [10].
•For patients who are already receiving positive airway pressure therapy, PSG is started and performed with the patient wearing continuous positive airway pressure (CPAP). The pressure is titrated if breakthrough OSA is detected. PSG in this setting can also determine if the patient has developed treatment-emergent central sleep apnea. This is particularly relevant if the patient's CPAP unit at home does not have download capability or does not distinguish between central and obstructive events, or if there is a question about the identity of obstructive versus central apneas on the download data. (See "Mode selection for titration of positive airway pressure in adults with obstructive sleep apnea" and "Mode selection for positive airway pressure titration in adult patients with central sleep apnea syndromes".)
•For patients who are being treated with an oral appliance, PSG is performed with the oral appliance in position and the patient is awakened if breakthrough OSA is identified in order to adjust the device. (See "Oral appliances in the treatment of obstructive sleep apnea in adults", section on 'Device titration'.)
•Patients who have undergone surgical therapy for OSA should also be re-evaluated after an appropriate healing interval to determine the degree of residual OSA. (See "Surgical treatment of obstructive sleep apnea in adults".)
PSG is also used to assess and diagnose other forms of sleep-disordered breathing, including Cheyne-Stokes breathing, central apnea, concurrent chronic obstructive pulmonary disease and OSA, and hypoventilation possibly related to obesity or neuromuscular disease. (See "Central sleep apnea: Risk factors, clinical presentation, and diagnosis" and "Sleep-disordered breathing in heart failure" and "Sleep-related breathing disorders and stroke" and "Sleep-related breathing disorders in COPD".)
PSG is also part of the diagnostic evaluation of selected patients with periodic limb movements during sleep, parasomnias, rapid eye movement (REM) sleep behavior disorder, and excessive daytime sleepiness. (See "Approach to abnormal movements and behaviors during sleep" and "Rapid eye movement sleep behavior disorder", section on 'Diagnosis' and "Approach to the patient with excessive daytime sleepiness".)
When nocturnal seizures are considered as part of the differential diagnosis of abnormal movements or behaviors during sleep, extended electroencephalogram (EEG) monitoring is typically performed during the PSG. (See "Polysomnography in the evaluation of parasomnias and epilepsy".)
CONTRAINDICATIONS — There are no contraindications to polysomnography (PSG), but the following caveats must be noted. The patient should be medically stable, since nurses and physicians are not usually immediately available during testing. Special accommodations may be necessary for some patients, including those with spinal cord injury. These preparations should be made before the patient presents to the sleep laboratory.
Patients with active respiratory infections with significant and unusual nasal congestion and severe coughing should be rescheduled to a time when they are not sick. Similarly, patients with acute pain treated with high-dose opioids that they do not usually take should be rescheduled. Other less common reasons for deferral of testing include infestations of lice or bed bugs. Chronic, stable doses of opioids and chronic respiratory problems do not preclude testing.
Pacemakers, defibrillators, and left ventricular assist devices are usually not a contraindication to PSG, but clinicians should check with their sleep laboratory. For inpatients, the risks versus the benefits of transfer from the hospital ward to the sleep laboratory should be considered [11]. A portable sleep study may be more appropriate in some cases. (See "Obstructive sleep apnea and other sleep disorders in hospitalized adults".)
COMPLICATIONS — Complications of polysomnography (PSG) are rare. The most common complication is skin irritation caused by adhesive used to attach electrodes to the patient. Drawbacks include inconvenience, difficulty sleeping in the laboratory setting, strange surroundings, and discomfort related to the monitoring equipment or bed.
As patients can and do experience medical emergencies while undergoing testing, laboratories must be prepared with ready access to age-appropriate resuscitative equipment, staff training, and an established protocol for access to emergency medical services. In a multiyear review of a hospital-based sleep laboratory, the rate of safety events was approximately 1 in 150 studies [12]. The most common events were chest pain, shortness of breath, and vital sign abnormalities.
MEASURED VARIABLES — Measurement of the following physiologic variables is required during polysomnography (PSG), according to the American Academy of Sleep Medicine (AASM) [10,11,13]:
●Sleep stages – Global neural electroencephalographic activity (EEG), eye movements (ie, electrooculogram [EOG]), and submental electromyographic activity (EMG) are used to identify the stages of sleep. The EEG is generally measured from the frontal, central, and occipital regions of the brain. The submental EMG detects hypotonia, which is typical of rapid eye movement (REM) sleep, and is helpful in detecting involuntary clenching or grinding of the teeth. (See "Stages and architecture of normal sleep", section on 'Sleep staging' and "Polysomnography in the evaluation of parasomnias and epilepsy", section on 'EEG derivations'.)
●Respiratory effort – Esophageal manometry is the gold standard for assessing ventilatory effort, but it is not routinely used because placement of the esophageal manometer is invasive. Respiratory inductive plethysmography (RIP) and diaphragmatic and/or intercostal EMG are frequently used alternatives or back-up [13-15]. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Respiratory effort'.)
●Airflow – Nasal prongs measuring nasal pressure detect inspiratory and expiratory flow and may be the most accurate method to identify subtle inspiratory flow limitation. Nasal pressure is especially helpful in detecting hypopneas. An important limitation of nasal pressure transducers is that they cannot detect mouth breathing. To overcome this limitation, a thermistor is usually added. Thermistors detect airflow at the mouth by sensing alterations in heat exchange. Thermistor data are utilized to detect apneas. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Respiratory airflow'.)
●Snoring – Snoring is detected with a microphone attached to the neck.
●End-tidal carbon dioxide (CO2) – An end-tidal carbon dioxide (CO2) monitor is an adjunctive method used to identify hypoventilation in selected studies. This is more commonly used in pediatric studies. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Ventilation' and "Overview of polysomnography in infants and children", section on 'Respiratory monitoring'.)
●Transcutaneous PCO2 monitor – Some sleep laboratories incorporate transcutaneous PCO2 monitoring in selected patients. This provides a quantitative measure for CO2, but it is subject to errors for a variety of reasons. It is useful when evaluating for the presence of hypoventilation during sleep, especially if oxygen or positive airway pressure is being used.
●Oxygen saturation – Pulse oximetry is used to monitor the oxyhemoglobin saturation during PSG. The signal averaging time should not exceed three seconds [13]. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Pulse oximetry'.)
The impact of skin color on pulse oximetry data will need to be systematically evaluated as it relates to the device specifications and scoring of sleep disordered breathing [16,17].
●Electrocardiogram – Electrocardiography is performed to detect arrhythmias during sleep. A single modified lead II alone is preferred, which can be obtained from a single torso electrode [13].
The following physiologic variables are recommended during PSG, according the AASM [10,11,13]:
●Body position – Some patients only have abnormalities when sleeping in certain positions. Therefore, body position (eg, supine, left lateral, right lateral, prone) is monitored throughout the test using a position sensor and/or video monitor. The technologist also documents the patient's position and when the patient changes position. If the head of the bed is elevated, the technologist should note the approximate elevation and whether this is comparable to how the patient sleeps at home.
●Limb movements – An EMG of the anterior tibialis of both legs is generally monitored during PSG, in order to detect leg movements. (See "Polysomnography in the evaluation of parasomnias and epilepsy", section on 'EMG derivations'.)
Video-monitoring using an infrared sensor and a two-way communication system between the sleep study bedroom and the technologist control room is also important for patient monitoring.
DERIVED INFORMATION — Polysomnography (PSG) can provide tremendous amounts of data that need to be analyzed and integrated. As a result, it should be interpreted by a specialist trained in the diagnosis of sleep disorders [10]. Patterns of abnormalities identified during PSG are often diagnostic. Formal sleep reports summarize data over the entire night in both graphical (figure 2 and figure 3) and tabular form (figure 4).
The following information is normally derived from an attended, in-laboratory PSG [11,13].
●Total recording time – The total time that the patient is being monitored from lights out to lights on.
●Total sleep time – The total sleep time (TST), in minutes, is the total duration of light sleep (stages N1 and N2), deep sleep (stage N3), and rapid eye movement (REM) sleep (stage R).
●Sleep efficiency – Sleep efficiency (SE) percentage is the TST divided by the total recording time (ie, the time in bed).
●Sleep stage percentage – The sleep stage percentage (SSP) for a particular sleep stage is the duration of that sleep stage divided by the TST.
●Sleep latency in minutes – The period between lights out to the first epoch of sleep.
●Sleep stage latency – The latency to any sleep stage is the duration from sleep onset to the initiation of that sleep stage. Most clinical studies report latency to the first epoch of sleep and the latency to REM sleep.
●Arousals – Arousals range from full awakenings to three-second transient electroencephalography (EEG) shifts to a lighter stage of sleep. Arousals are generally counted and then divided by the TST to give the number of arousals per hour of sleep (ie, arousal index). EEG arousals are an important measure of sleep disturbance and they provide a baseline from which to assess treatment response [18]. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Arousals'.)
●Apneas – Apnea is the cessation, or near cessation, of airflow. It is typically characterized as being obstructive, central, or mixed. Precise criteria for scoring an apnea are presented separately. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Apneas'.)
●Hypopneas – Hypopnea is an abnormal reduction of airflow to a degree that is insufficient to meet the criteria for an apnea. Precise criteria for scoring a hypopnea are presented separately. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Hypopneas'.)
●Respiratory effort-related arousals – Respiratory effort-related arousals (RERAs) are arousals that are associated with a change in airflow that does not meet the criteria for apnea or hypopnea. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Respiratory effort-related arousals'.)
●Cheyne-Stokes breathing – Cheyne-Stokes breathing is a breathing pattern of consecutive cycles of crescendo and decrescendo changes in airflow and respiratory effort. The point with the least airflow and effort is a central apnea. Cheyne-Stokes breathing is seen in association with neurologic or cardiac disorders such as heart failure with reduced ejection fraction. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Cheyne-Stokes respiration'.)
●Indices – Indices derived from polysomnographic data describe the frequency of abnormal respiratory events during sleep. These include the apnea index (AI), apnea-hypopnea index (AHI) per hour, and respiratory disturbance index (RDI). It is helpful to report these indices at baseline and at each level of positive airway pressure during titration. It is helpful to note these parameters for supine versus non-supine positions and for REM versus non-REM (NREM) sleep stages. These indices are described in detail separately. (See "Polysomnography in the evaluation of sleep-disordered breathing in adults", section on 'Measures of sleep-disordered breathing severity'.)
●Snoring – The amount and intensity of snoring can be determined with a small microphone attached to the neck, under the chin. Some centers calculate a snoring index, which describes the number of snores per hour of sleep.
●Body position – With observation of body position, it can be determined whether obstructive apneas, hypopneas, or snoring are dependent upon body position.
●Oxyhemoglobin saturation – The baseline oxyhemoglobin saturation, mean oxyhemoglobin saturation, frequency of desaturation episodes, duration of desaturation episodes, severity of desaturation episodes, duration spent at an oxyhemoglobin saturation ≤88 percent, and nadirs of oxyhemoglobin saturation can be determined from the oximetry recording during PSG. The oxygen desaturation index (ODI) reports the number of times per hour that the oxyhemoglobin saturation drops by 3 percent (ODI 3 percent) or 4 percent (ODI 4 percent) from baseline.
●Limb movements – Limb movements during sleep may be counted both as isolated events and in association with arousals. Both the number of limb movements and the number of limb movements with arousal are tabulated, and an index of number per hour is noted in the report. As with the other variables, the number of events per hour of sleep can be used to quantify severity. (See "Polysomnography in the evaluation of abnormal movements during sleep".)
●EEG abnormalities – Any abnormal EEG patterns (eg, spikes, spike and wave pattern) or evidence of seizure activity should be noted and sample images saved. Any abnormal activity or repetitive movements during sleep should also be noted and video images saved if possible. (See "Polysomnography in the evaluation of parasomnias and epilepsy".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Sleep-related breathing disorders in adults" and "Society guideline links: Parasomnias, hypersomnias, and circadian rhythm disorders".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: What is a sleep study? (The Basics)")
●Beyond the Basics topic (see "Patient education: Sleep apnea in adults (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Technique – Attended, in-laboratory polysomnography (PSG) is considered the gold standard diagnostic test for obstructive sleep apnea (OSA) and other sleep disorders. During PSG, the patient sleeps while connected to numerous monitoring devices and a technologist records physiologic variables. Patterns of physiologic abnormalities during sleep are often diagnostic. (See 'Technique' above.)
●Indications – Diagnostic evaluation of suspected OSA, titration of positive airway pressure therapy, and assessment of the effectiveness of therapy are the most common indications for PSG. There are no contraindications to PSG and few complications, although patients should be medically stable to undergo the procedure. (See 'Indications' above and 'Contraindications' above and 'Complications' above.)
●Measured variables – Physiologic variables assessed during PSG include the sleep stages, respiratory effort, airflow, oxyhemoglobin saturation, electrocardiography, body position, and limb movements. (See 'Measured variables' above.)
●Derived information – From these physiologic variables, an abundance of information is derived. This includes sleep architecture, the frequency of abnormal events (eg, apneas) during sleep, and various diagnostic measures (eg, apnea-hypopnea index [AHI]). (See 'Derived information' above.)
