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Obstructive sleep apnoea (OSA)

What is obstructive sleep apnoea (OSA)?

Obstructive sleep apnoea, or OSA, is a breathing problem that happens when you sleep.

It’s called OSA because:

Obstructive: there’s an obstruction in the airway

Sleep: it happens when you’re asleep

Apnoea: it means you stop breathing

When you go to sleep your muscles relax, including those in your throat. In some people the relaxing muscles cause the airways to narrow. This can reduce the amount of air flowing in and out of your airways. This makes you snore.

If your throat closes completely, you stop breathing for a time. This is called an apnoea if it lasts for 10 seconds or more. If the airways in your throat narrow this is called a hypopnoea. When this happens, there may be a dip in the level of oxygen in your blood.

Your brain will start your breathing again. Some people wake up briefly, but others are not aware of what’s happening. Breathing often restarts with a gasp or grunt and some movement. You relax again, and the pattern then starts again.

If you have severe OSA, this cycle can happen hundreds of times a night. These frequent arousals disrupt your sleep and so you can feel very sleepy during the day.

Diagram - Air travelling freely through the airways

In normal breathing, air can travel freely to and from your lungs through your airways during sleep.



Diagram - air cannot pass through the collapsed airway

In OSA, your airway collapses, stopping air from travelling to and from your lungs, disturbing your sleep.


Next: Symptoms of OSA >

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Download our OSA information (PDF, 351KB)

Last medically reviewed: March 2019. Due for review: November 2021

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.