Polysomnography (also called a sleep study test) is the main and most accurate sleep apnea test to date, capable of detecting different types of sleep disorders in just one night.
This type of sleep test is one of the most complex procedures in modern sleep medicine. Being a comprehensive study, polysomnographic testing is capable of identifying almost all types of sleep disorders the patient might have. Hence it is often considered the gold standard in somnology as it provides a clear picture on what the patient is experiencing during sleep – including snoring, apnoeas, REM-behavioral disorder, or narcolepsy.
How is Polysomnography Performed?
The test is conducted in a clinical settings environment, with the patient staying for the night at the facility while being monitored by a sleep specialist. The specialist actively tracks the patient's therapy on a screen throughout the night. All abnormal activities are recorded and analyzed in real-time. In the morning, the doctor (somnologist) analyzes the compiled data and provides a detailed diagnosis to the patient.
💡 Good to know: The polysomnographic testing is often aided by video surveillance using a night vision camera, which allows the specialist to track physical movements during sleep.
What Can Polysomnography (PSG) Detect?
Sleep apnea (both obstructive and central types) can be easily detected during a polysomnography test. As a multi-parametric sleep study, PSG detects the following vital signals and events during the night:
Neurological & Muscle Activity
Monitors Brain activity (electroencephalogram – EEG), Rapid eye movement (electrooculogram – EOG), and abnormal muscle electrical activity (electromyogram – EMG).
Cardiorespiratory Functions
Tracks Cardiac activity (electrocardiogram – ECG), oxygen saturation and pulse (pulse oximetry), respiratory effort, and respiratory flow throughout the night.
Physical Movements
Records snoring intensity and frequency, body position changes, and periodic lower limb movements that might disrupt the natural sleep cycle.
Typical Polysomnographic Diagnostic Tools
Modern sleep monitoring utilizes highly advanced, compact devices to record patient data. Below are two of the most widely used screening devices in sleep medicine:
1 ApneaLink™ Plus Diagnostic Device
A compact, portable sleep testing device used to record respiratory effort, pulse, oxygen saturation, and nasal flow. It is highly effective for initial sleep apnea screenings and provides clear, automated reports for sleep physicians.
2 Nox T3 Portable Sleep Monitor
An advanced, lightweight sleep monitor that measures a multitude of parameters including audio (snoring), respiratory effort, and body position. It is highly regarded for its precision and ease of use in both clinical and home environments.
Preparation: Do's and Don'ts
Polysomnographic examination is conducted when it is convenient for the patient and they are ready to spend a night in the sleep clinic. Patients are even allowed to bring their personal pillow from home. Preparations for the test are minor but essential:
What you SHOULD do before the test:
- Clean and properly dry your hair (to ensure scalp sensors stick properly).
- Maintain your normal diet to avoid influencing your regular sleep pattern.
- Take your usual daily medications (unless instructed otherwise by your doctor).
What you should AVOID:
- Avoid acrylic nails and polish on the index fingers (as this interferes with the pulse oximeter).
- Do not take afternoon naps on the day of the study.
- Avoid consuming heavy caffeine or alcohol before your appointment.
⚠️ Keep in mind: Polysomnography is a completely painless and non-invasive procedure. The only minor inconvenience is sleeping in a different bed and potential slight skin irritation from the adhesive used for the sensors.
What to Expect: 5 Steps of a Sleep Study
If you have an upcoming polysomnography test, here is a quick breakdown of how the night usually unfolds:
Frequently Asked Questions
Is the polysomnography test painful?
Not at all. The procedure is entirely non-invasive and painless. The sensors are applied to your skin using a mild, skin-friendly adhesive or tape, and simply rest on the surface to read physiological signals.
What if I can't fall asleep in a clinic?
It is very common for patients to worry about "performance anxiety" or not sleeping as well as they do at home. However, sleep technicians usually only need a few hours of actual sleep data to make an accurate diagnosis. You do not need a perfect 8 hours of sleep for the test to be successful.
Why do I need to remove my nail polish?
One of the sensors used during the study is a pulse oximeter, which is clipped to your index finger to measure the oxygen levels in your blood. Dark nail polish or acrylic nails can block the light sensor and provide inaccurate readings.
Conclusion
Polysomnography is one of the most valuable studies in sleep medicine, giving the most comprehensive and objective multi-parametric data measuring both the quantity and quality of sleep. This modern-day diagnostic tool allows doctors to pinpoint with uttermost precision when each phase of sleep begins and ends.
In addition, polysomnography allows the identification of almost all sleep diseases. It can be used to determine if the patient is snoring, gnashing their teeth, if they have sleep apnea, narcolepsy, or parasomnias like sleepwalking or REM-behavioral disorder.
