Obstructive sleep apnoea - Diagnosing obstructive sleep apnoea

Obstructive sleep apnoea (OSA) can usually be diagnosed after you've been observed sleeping at a sleep clinic, or by using a testing device worn overnight at home.

If you think you have OSA, it's important to visit your GP in case you need to be referred to a sleep specialist for further tests and treatment.

Before seeing your GP, it may be helpful to ask a partner, friend or relative to observe you while you are asleep if possible. If you have OSA, they may be able to spot episodes of breathlessness.

It may also help to fill out an Epworth Sleepiness Scale questionnaire. This asks how likely you'll be to doze off in a number of different situations, such as watching TV or sitting in a meeting. The final score will help your doctor determine whether you may have a sleep disorder.

An online version of the Epworth Sleepiness Scale can be found on the British Lung Foundation website.

Seeing your GP

When you see your GP, they will usually 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. These will help 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, your GP will need to refer you to a local sleep centre. These are specialist clinics or hospital departments that help treat people with sleep disorders. The Sleep Apnoea Trust Association has a list of NHS sleep clinics in the UK.

Observing your sleep

The sleep specialists at the sleep centre may first ask you about your symptoms and medical history, and they may also carry out a physical examination.

This may include measuring your height and weight to work out your body mass index (BMI), as well as measuring your neck circumference. This is because being overweight and having a large neck can increase your risk of OSA.

The sleep specialists will then arrange for your sleep to be assessed overnight, either by spending the night at the clinic or taking some monitoring equipment home with you and bringing it back the next day for them to analyse.

Testing at home

In many cases, the sleep centre will teach you how to use portable recording equipment while you sleep at home.

The equipment you are given may include:

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

The equipment records oxygen levels, breathing movements, heart rate and snoring through the night.

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

Testing at a sleep centre

The main test carried out to analyse your sleep at a sleep centre is known as polysomnography.

During the night, several different parts of your body will be carefully monitored while you sleep.

Electrodes (small metallic discs) and bands will be placed on the surface of your skin and different parts of your body. Sensors will also be placed on your legs, and an oxygen sensor will be attached to your finger.

A number of different tests will be carried out during polysomnography, including:

• electroencephalography (EEG) – this monitors brain waves
• electromyography (EMG) – this monitors muscle tone
• recordings of movements in your chest and abdomen
• recordings of airflow through your mouth and nose
• pulse oximetry – this measures your heart rate and blood oxygen levels
• electrocardiography (ECG) – this monitors your heart

Sound recording and video equipment may also be used.

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 it closing, which prevents OSA.

Read about treating OSA for more information about CPAP.

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.

Determining the severity of OSA

The severity of OSA is determined by how often your breathing is affected over the course of an hour. These episodes are measured using the apnoea-hypopnoea index (AHI).

Severity 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

Current evidence suggests treatment is most likely to be beneficial in people with moderate or severe OSA, although some research has suggested treatment may also help some people with mild OSA.