Diagnosis - Obstructive sleep apnoea

Obstructive sleep apnoea (OSA) can usually be diagnosed by watching you sleeping. This can happen in a sleep clinic. It can also be done using a testing device worn overnight at home.

Talk to your GP if you think you have OSA. They may need to refer you to a sleep specialist for further tests and treatment.

Before talking to your GP, ask a partner, friend or relative to observe you while you're asleep. 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 different situations. For example, watching TV or sitting in a meeting.

The final score will help your doctor determine whether you may have a sleep disorder.

A score of 8 to 9 is average during the daytime. A score of 16 to 24 means you're very sleepy and you need medical attention.

Seeing your GP

Your GP, will ask questions about your symptoms. For example, if you regularly fall asleep during the day against your will.

They will take your blood pressure and a blood sample. The sample will rule out other conditions. For example, an underactive thyroid gland (hypothyroidism).

Your GP can refer you to a sleep specialist.

Observing your sleep

The sleep specialists may ask you about your symptoms and medical history. They may also carry out a physical examination.

You will spending the night at a clinic or take some monitoring equipment home. The sleep specialists will assess your sleep overnight.

Testing at home

The specialist will show you how to use the portable equipment while you sleep at home.

The equipment may include:

  • a breathing sensor
  • a heart rate sensor
  • bands for your chest
  • oxygen sensors for your finger

The equipment records:

  • oxygen levels
  • breathing movements
  • heart rate
  • snoring through the night

Testing at a sleep centre

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

Different parts of your body will be monitored while you sleep.

Bands and small metallic discs called electrodes are placed on the surface of your skin. Sensors are also placed on your legs and an oxygen sensor attached to your finger.

You will have different tests 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

They may also use sound or video recording equipment.

You may be diagnosed with OSA during the early part of the night. If so, you may get continuous positive airway pressure (CPAP) treatment. This involves using a mask that delivers constant compressed air to the airway. This stops it closing and prevents OSA.

Read about treatment for obstructive sleep apnoea

After the tests, staff know if you have OSA. If you do, they can find out how much it is interrupting your sleep. They can then recommend treatment.

Determining the severity of OSA

How often your breathing is affected will determine how severe your OSA is. The Apnoea-Hypopnoea Index (AHI) measures this.

The scale is:

  • 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


Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 22 December 2020
Next review due: 22 December 2023

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