Polysomnography (PSG; polysomnography) is a sleep medicine procedure and is used to diagnose sleep disorders. Among others, the common obstructive sleep apnea syndrome (OSAS) should be mentioned here, which is part of the metabolic syndrome (clinical name for the symptom combination obesity (overweight), hypertension (high blood pressure), elevated fasting glucose (fasting blood sugar) and fasting insulin serum levels (insulin resistance), and dyslipidemia (elevated VLDL triglycerides, decreased HDL cholesterol)) often affects obese (obese) patients. This disorder is characterized by obstructive (narrowing of the airways) apneas (cessations of breathing) or hypopneas (periods when the patient does not breathe or breathes too little during sleep) and often by snoring (rhonchopathy). However, other sleep disorders of diverse origin, such as hypersomnias (increased to excessive daytime sleepiness), insomnias (difficulty falling asleep or staying asleep), parasomnias (adverse events or sensations during the various sleep phases), or sleep-related movement disorders can also be examined. Polysomnography is performed as an inpatient in a sleep laboratory. The recordings can be used to create an individual sleep profile, which usually allows a precise diagnosis of sleep disorders. Because sleep diagnostics are highly susceptible to interference and sleep disorders have variable courses, repeat examinations may be necessary.
Indications (areas of application)
- Nightmares
- Apnea (pause in breathing, cessation of breathing)
- Epilepsy (seizure disorder)
- Enuresis nocturna – Nocturnal enuresis in children after the age of 4.
- Exploding head syndrome – Upon waking or falling asleep, the patient experiences a loud, non-painful, explosive sound.
- Hypopnea (under-breathing, reduced breathing.
- Hypersomniac disorders – state of excessive sleepiness during the day that cannot be explained by inadequate sleep duration; this clinical picture includes:
- Idiopathic hypersomnia – Extreme daytime sleepiness with very long but nonrestorative sleep episodes.
- Hypersomnia secondary to another mental or physical illness.
- Narcolepsy (sleeping sickness) – Narcolepsy is a neurological disorder and is one of the hypersomnias, it is characterized by extreme daytime sleepiness, attacks of falling asleep, cataplexies (sudden loss of muscle tone with falling), and vivid nightmares. (< 1 %),
- Kleine-Levin syndrome – Genetic syndrome that is one of the recurrent hypersomnias and is characterized by severe daytime sleepiness with a central cause (the cause is in the central nervous system). The hypersomnias occur periodically over days to weeks and may go into complete remission (temporary or permanent abatement of symptoms) in the interim. In addition, patients suffer from behavioral abnormalities such as hypersexuality, polyphagia (abnormally increased appetite), cognitive loss of function (loss of mental performance), aggressive behavior and psychotic symptoms such as hallucinations.
- Insomniac disorders – pattern of complaints with insufficient duration and/or quality of sleep including difficulty falling asleep, difficulty sleeping through the night and early morning awakenings.
- Catathrenia – sleep-related moaning.
- Lethal familial insomnia – disease from the group of prion diseases with progressive spongiform encephalopathy (progressive sponge-like brain disease that is lethal (fatal). Caused by malformed protein structures (prions) that destroy nerve cells) and initial sleep disorders.
- Menstruation-related hypersomnia – Recurrent episodes of hypersomnia associated with menstruation (menstruation in women).
- Non-breathing-related sleep disorder:
- Restless legs syndrome (“Restless legs”) – disorder characterized by painful, extremely uncomfortable sensations in the legs. Constant movement can give the patient relief – including the syndrome of nocturnal periodic leg movements (PLMD).
- Non-obstructive sleep apnea (non-respiration, i.e., cessation of breathing):
- Central sleep apnea syndrome (there is always a decreased or a (reflex) increased respiratory drive despite an open upper airway).
- Sleep-related hypoventilation syndromes (reduced breathing over an extended window of time during sleep)
- Non-REM parasomnias
- Pavor nocturnus – “sleep terror.” Affects mainly children. Patients awaken with a loud initial cry under intense fear accompanied by vegetative symptoms (sweating, restlessness). Unlike nightmares, a sleep event is not remembered by the patient
- States of confusion from sleep
- Sleep-related eating disorders – eating and drinking during an incomplete waking response without awareness of this process by the patient.
- Sleep-related hallucinations
- Obesity hypoventilation syndrome – hypoventilation syndrome with reversible underlying disease, obesity (extreme overweight/obesity).
- Obstructive sleep apnea syndrome (OSAS) – When diagnosis is confirmed to initiate therapy and routinely at three, six or twelve months.
- Psychophysiologic insomnia – Sleep disorder originating in increased physical or emotional tension.
- Psychogenic paralysis – paralysis of the whole body or individual parts of the body for which no organic cause can be demonstrated.
- Panic attacks
- Paradoxical insomnia – Subjective sleep disorder that cannot be objectified on polysomnography.
- Parasomnias – Undesirable behaviors referred to as occurring predominantly during sleep or at the sleep-wake transition.
- Periodic leg movements during sleep – Repetitive leg movements that may be accompanied by waking episodes.
- Rhythmic movement disorders – Rhythmic movements of the body or individual body parts during falling asleep.
- Rhonchopathy (pathological snoring).
- Sleep-related dissociative disorder – occurrence of dissociative events during the sleep-wake transition (Dissociative disorder is the term used to describe a loss of psychological integration of behavior and experience).
- Sleep-related movement disorders
- Restless legs syndrome (“Restless legs”) – disorder characterized by painful, extremely uncomfortable sensations in the legs. Constant movement can give the patient relief – including the syndrome of nocturnal periodic leg movements (PLMD).
- Sleep-related leg cramps,
- Rhythmic movement disorders or benign myoclonias (rapid involuntary muscle twitches) in childhood and adolescence,
- Teeth grinding (bruxism)
- Behavioral disorder in REM sleep – disorder in which there is a loss of natural sleep inhibition of motor activity (body movement). This involves aggressive behavior within dream experiences, a clustered occurrence in connection with alcohol or benzodiazepine withdrawal (withdrawal of sleeping pills) and as a possible initial manifestation of Parkinson’s disease (shaking disease) is described.
- Circadian rhythm disorders – disturbance of the sleep-wake rhythm with desynchronization of the same.
Contraindications
Cardiorespiratory polygraphy is a noninvasive diagnostic procedure, so there are no contraindications to consider, except for adequate indication. However, sufficient compliance (patient cooperation) is a prerequisite for performance.
Before the examination
Before the examination, a detailed internal medical history and a thorough physical examination are necessary to narrow down the diagnosis. For the most part, polysomnography is a noninvasive diagnostic method that does not require more intensive preparation of the patient. If intrathoracic pressure measurement is performed using an esophageal probe, the patient must be informed about possible complications and consent must be obtained. Because a variety of diagnostic measuring devices are used at the same time, the patient must be educated about the course of the examination.
The procedure
The goal of polysomnography is to record sleep architecture or stages and continuity of sleep. Neurological parameters as well as circulatory parameters are collected and recorded. In addition, video monitoring is required, which necessitates the continuous presence of medical personnel.This serves to monitor patient behavior as well as to control the technique, which is susceptible to interference, since EEG probes, for example, frequently become detached. Small polysomnography is the name given to an examination used for the diagnosis of psychiatric clinical pictures, for the differential diagnosis of epilepsies, and for therapy monitoring of breathing-related sleep disorders such as OSAS. The following parameters are recorded:
- Electroencephalogram (EEG) – recording of brain waves.
- Electrocardiogram (ECG) – recording of the electrical activity of the heart.
- Pulse oximetry – recording of blood oxygen saturation and heart rate.
- Electrooculography (EOG) – recording of eye movements; recording of REM phases (rapid-eye-movement phases; rapid eye movements; most dreams occur during this phase).
- Submental electromyography (EMG) – recording muscle activity, e.g., of the legs or masticatory muscles.
- Respiratory flow and movements – Both abdominal (belly breathing) and thoracic (chest breathing) respiratory movements are measured.
Continuous registration is performed for at least 6 hours. A large polysomnography is performed in cases of therapy-resistant sleep disorders (e.g., after initial suspicion of a psychogenic disorder), daytime sleepiness, and suspected respiratory sleep disorders. In addition to the above parameters, the following additional measures may be monitored:
- Blood pressure
- Movements and body position
- Erection measurement
- Body temperature
- Intrathoracic pressure (pressure in the chest) – By esophageal probe (probe used to measure pressure in the esophagus).
- Mask pressure measurement – Used when using a CPAP machine for OSAS (breathing aid that creates positive pressure, thereby counteracting airway constriction).
- Snoring sounds
- Sound monitoring by means of microphone
To investigate nocturnal hypoventilation, standard polysomnography is supplemented with continuous recording of partial pressure of carbon dioxide (pCO 2). Transcutaneous measurement is most commonly used for this purpose. Polysomnography is the most comprehensive sleep examination and is performed in certified sleep laboratories. In most cases, the examination takes place as an inpatient on two consecutive days and nights. While polysomnography is performed in the sleep laboratory, polygraphy takes place in the patient’s own bed. The scope of the performed examinations is reduced to the determination of the nocturnal oxygen saturation and pulse rate, as well as about the body position and breathing during sleep including snoring. Depending on the type of device, an electrocardiogram (ECG) and electromyography (EMG) are also part of the polygraphy. EMG makes it possible to record the nocturnal activity of the leg muscles during sleep. Determination of the data ensures, among other things, the diagnosis of sleep apnea or restless legs syndrome (restless legs).
After the examination
No special measures are required on the patient after polysomnography. Depending on the results of the examination, medication or other therapeutic measures may need to be performed. In the event of erroneous measurements, artifacts, or inconclusive results, a repeat of the examination should be considered.
Potential complications
Because polysomnography is a noninvasive procedure, no complications are expected.If pressure measurement is performed using an esophageal probe, it should be noted that insertion of an esophageal probe is very uncomfortable and is associated with high patient stress. Rarely, injury to the nasopharynx or esophageal mucosa occurs.