Obstructive sleep apnoea (OSA) is diagnosed by observation of your sleep.

If you have symptoms of excessive daytime sleepiness, such as feeling drowsy, a lack of energy and poor memory, ask a partner, friend or relative to observe you while you are asleep. If you have OSA, they may be able to spot episodes of breathlessness.

If you think you have OSA, visit your GP.

Physical examination and tests

Your GP will ask you a number of questions about your symptoms, such as whether you regularly fall asleep during the day against your will.

Your GP will also carry out a physical examination and some tests, including a blood pressure test. A blood test is also likely to be arranged.

A physical examination and tests are carried out to rule out other conditions that could explain your tiredness, such as hypothyroidism (an underactive thyroid gland).

The next step is to observe you while you are asleep. To do this, you may be asked to spend a night at a sleep centre so that any events that indicate OSA can be monitored. This is known as polysomnography (see below).

Alternatively, you may be given a monitoring device to wear at night while you sleep at home (a home sleep study). The device is returned to the sleep centre the following day so that the recorded information can be downloaded by staff.

Testing at a sleep centre

Sleep centres are specialist clinics or hospital departments that help treat people with sleep disorders.

Typically you will be referred for an overnight stay in a sleep centre, during which your sleep will be observed.

Polysomnography

The main investigation into your sleep is polysomnography. This investigation will enable sleep specialists to decide what is the best treatment for you.

During polysomnography, specialist nurses will place a series of electrodes on the surface of your skin (this is painless) and bands on other areas.

You will then be provided with a room in which you can sleep for the night. While you sleep, specialist sleep nurses will monitor the signals from the electrodes.

Electrodes and bands are placed on the following areas:

• electrodes on your face and scalp
• electrodes above your lip
• bands around your chest
• bands around your abdomen (tummy)

Sensors will also be placed on your legs, and an oxygen sensor will be attached to your finger.

The tests that are carried out during a polysomnography include:

• electro-encephalography (EEG) – this monitors your brain waves
• electromyography (EMG) – this monitors your muscle tone
• recording thoracoabdominal movements (movements in your chest and abdomen)
• recording oronasal airflow (the airflow in your mouth and nose)
• pulse oximetry – this measures your heart rate and blood oxygen levels
• electrocardiography (ECG) – this monitors your heart
• sound and video recording to record your breathing and snoring, and your behaviour during the night

Polysomnography must be done by experienced technicians in a hospital or sleep centre.

If OSA is diagnosed during the early part of the night, you may be given continuous positive airway pressure (CPAP) treatment. CPAP involves using a mask that delivers constant compressed air to the airway and stops the airway from closing, which prevents OSA.

Read how sleep apnoea is treated for more information about CPAP treatment.

Once the tests have been completed, staff at the sleep centre should have a good idea about whether or not you have OSA. If you do, they can determine how much it is interrupting your sleep and recommend appropriate treatment.

Apnoea-hypopnoea index (AHI)

The severity of OSA is determined by how many episodes of apnoea and hypopnoea you experience over the course of an hour. These episodes are measured using the apnoea-hypopnoea index (AHI).

The severity of OSA is measured using the following criteria:

• mild – an AHI reading of 5 to 14 episodes an hour
• moderate – an AHI reading of 15 to 30 episodes an hour
• severe – an AHI reading of more than 30 episodes an hour

An AHI reading of less than 10 is unlikely to be linked to a clinical problem or sleep disorder.

Home study

A home sleep study is a possible option. However, you will still need to visit a specialist sleep centre during the day to learn how to use the home study equipment.

You will need to learn how to use portable recording equipment, which includes:

• a breathing sensor
• sensors to monitor your heart rate
• oxygen sensors that are put around your finger and bands around your chest

The equipment records levels of oxygen, breathing movements, heart rate and snoring.

After you have used this equipment overnight, you will need to take it to the sleep centre, where the information will be analysed by sleep specialists.

If more information about sleep quality is required by the sleep centre, a polysomnography will be required, which will be carried out at the sleep centre.