Sleep apnoea tests and diagnosis
If you have symptoms that suggest you may have sleep apnoea, you should seek medical advice. It will help, if you have a partner, to ask him or her to observe you sleeping. Your partner’s comments can help the doctor with the diagnosis. Your doctor will examine you, check your blood pressure and ask for blood tests, which will help to determine other possible causes of your symptoms, such as an underactive thyroid gland.
You may then be referred to a sleep clinic, a specific hospital department that specialises in sleep disorders. You may be asked to have some simple tests that include seeing how quickly you go to sleep, and how well you can manage to stay awake. You may also be asked to stay overnight. Your blood oxygen levels will be measured through a simple device called an oximeter, and you may have a sleep apnoea test. This often includes a polysomnogram.
A sleep study or polysomnogram (PSG) is a multiple-component test carried out while you are asleep. It electronically transmits and records specific physical measurements including breathing rate, heart rate, blood pressure, oxygen level of the blood and depth of sleep. The recordings are analysed by a sleep specialist to determine whether or not you have sleep apnoea or another type of sleep disorder.
Sleep apnoea can range from being mild, with five to 15 episodes an hour, to severe, with over 30 episodes an hour.
If sleep apnoea is diagnosed, you may be asked to return to the sleep clinic for further evaluation in order to determine the best treatment option.
What to expect
On the night of your sleep study, you will be assigned to a private bedroom in a sleep clinic, usually in a hospital. Near the bedroom will be a central monitoring area, where the technicians monitor sleeping patients.
You will be hooked up to equipment that may look uncomfortable. However most people fall asleep with little difficulty.
Surface electrodes will be put on your face and scalp and will send recorded electrical signals to the measuring equipment. These signals, which are generated by your brain and muscle activity, are then recorded digitally. Belts will be placed around your chest and abdomen to measure your breathing. An oximeter probe will be put on your finger to measure the amount of oxygen in your blood.
Other tests and equipment used
- EEG (electroencephalogram) to measure and record brain wave activity
- EMG (electromyogram) to record muscle activity such as face twitches, teeth grinding and leg movements, and to determine the presence of REM stage sleep. During REM sleep, intense dreams often occur as the brain undergoes heightened activity.
- EOG (electro-oculogram) to record eye movements. These movements are important in determining the different sleep stages, particularly REM stage sleep.
- ECG ( electrocardiogram) to record heart rate and rhythm.
- Nasal airflow sensor to record airflow.
- Snore microphone to record snoring activity