What is polysomnography (PSG)?
Polysomnography, also known as PSG or sleep study, is a test used to diagnose sleep disorders. It is done while you are fully asleep. After you complete the overnight study, a specialist will interpret your sleep pattern data.
As part of your PSG, your doctor will examine the following to chart your sleep cycles and identify any disruptions in your sleep patterns:
- Heart rate
- Brain waves
- Body position
- Eye movements
- Limb movements
- Breathing patterns
- Blood oxygen level
- Chest and abdominal movements
- Snoring and other noises you may make during sleep
Why do you need polysomnography (PSG)?
Your doctor may recommend a polysomnogram test if they suspect that you have any of the following.
- Central sleep apnoea, a disorder in which breathing constantly stops and restarts during sleep. This happens because your brain fails to send correct signals to the muscles that help you with breathing.
- Obstructive sleep apnoea (OSA), a disorder in which your throat muscles periodically relax during sleep and inadvertently block your airway.
- Periodic limb movement disorder, in which you involuntarily flex and extend your legs while sleeping. This condition may be associated with restless legs syndrome.
- Narcolepsy, a brain condition that makes you suddenly fall asleep at inappropriate times.
- Rapid eye movement (REM) sleep behaviour disorder, which makes you act out dreams as you sleep.
- Chronic insomnia, which means that you have trouble falling asleep or staying asleep.
- Unusual behaviours during sleep
If sleep disorders go untreated, they can raise your risk of:
What are the risks and complications of polysomnography (PSG)?
Polysomnography is a non-invasive and painless test. In general, the risks are low.
You may however experience skin irritation caused by the adhesive used to attach the electrodes to your skin.
How do you prepare for polysomnography (PSG)?
Avoid consuming alcohol and caffeine the afternoon and evening before the test. Both substances can affect sleep patterns and impact your test results.
You should also avoid napping in the afternoon before a sleep study.
Inform your doctor about any medications that you are taking, in case any of them will interfere with your sleep study test.
What can you expect in polysomnography (PSG)?
Polysomnography tests are done in a private room with an attached bathroom. The sleeping area will usually have a low-light video camera so that the team can monitor your sleep movements in the dark. There will also be an audio system so that they can talk to you and hear you from their monitoring station outside the room.
You can bring your own pyjamas and other items that you use for your bedtime routine so that you will feel more comfortable and at home.
Estimated duration
This test takes about 10 – 12 hours. Typical check-in times start between 8pm – 10pm, and typical check-out times start between 6am – 8am.
The goal is for you to sleep for at least 7 hours during the test.
Before the procedure
You will be asked to arrive at the sleep clinic about 2 hours before your usual bedtime. As you get ready for bed, a technician will set up the following monitoring equipment on you.
- Sensors on your scalp, temples, chest and legs. These sensors are connected to a computer through wires that are long enough to allow you some freedom to move.
- A small clip on your finger to monitor blood oxygen levels.
- Elastic belts around your chest and stomach to record your chest movements and breathing patterns.
If you are suspected to have sleep apnoea, the technologist may also set up a positive airway pressure machine. This device consists of a mask-like device that delivers a gentle stream of air to enhance your breathing. If necessary, oxygen may also be used during the study to enhance your breathing.
After the procedure
When the test is over, all the monitoring equipment are removed before you leave the clinic. You can resume your normal daily activities immediately.
You will be given a follow-up appointment with your doctor to discuss your PSG results and suitable treatment options.
If you are diagnosed with sleep apnoea, your doctor may recommend that you use a continuous positive airway pressure (CPAP) machine. Follow-up polysomnography may be necessary to help determine the right CPAP settings for you.
