Fact Sheet: Obstructive Sleep Apnoea
Obstructive Sleep Apnoea (OSA)
What is Sleep Apnoea?
Sleep apnoea occurs when breathing stops during sleep due to a complete blockage of the airway.
How do we breathe?
A breath results when the diaphragm (the muscle between the chest and abdomen) and the intercostal muscles (the muscles between the ribs) contract. This causes the ribcage and lungs to expand allowing air to enter the lungs. There are a number of other muscles in the nose and at the back of the throat, which also contract when we breathe in. This helps to open up the airway, better enabling air to move into the lungs.
What causes OSA?
If for some reason the airway is smaller, our body compensates for this while we are awake by making the muscles work harder to keep the airway open. However when we sleep our muscles are not as active or strong and the back of the throat may become narrower.
Because of this narrowing, during the night, the airway may partially or completely block. A partial blocking of the airway causes snoring. When there is a complete blockage of the airway it is called obstructive sleep apnoea or OSA.
What happens in OSA?
In some people the muscles in the airway can become so relaxed when they are asleep that the airway is completely blocked. OSA occurs when breathing stops for periods of at least 10 seconds during sleep. A person with OSA keeps trying to breathe but no air enters the lungs and the level of oxygen in the blood drops (hypoxia). This eventually leads to the breathing centre in the brain sending a message to the upper airway muscles to open the airway and breathing resumes, usually accompanied by a loud snort or gasp, causing them to wake. The person affected by sleep apnoea maybe unaware that they have woken and immediately returns to sleep. Once asleep the muscles relax again and the whole cycle recurs. This cycle can occur hundreds of times during sleep.
Who gets OSA?
OSA can occur at any age (including infancy) but is most common in over-weight middle-aged males. It affects between 1 and 4% of the population, and up to 10% in middle-aged males.
OSA is more common if:
A person is overweight. This makes people more susceptible to OSA because excess weight on the outside of the throat increases pressure on the inside of the throat, which in turn narrows the airway.
If alcohol, tranquillisers or sleeping tablets are used prior to going to sleep, this can excessively relax the muscles, making people more susceptible to OSA.
A condition that leads to excess tissue in the airway is present e.g. enlarged tonsils or jaw deformities.
Signs and symptoms of OSA
Often, the first indications of sleep apnoea are reports from others in the household about noisy snoring.
Other signs of OSA are:
- Waking up in the morning and feeling tired and as if you have not had enough sleep
- Falling asleep during the day
- Morning headache
- Constant tiredness during the day
- Difficulty concentrating
- Loss of interest in sex
- Memory loss
- Personality change
Why is OSA a problem?
Some studies have shown that people with OSA may be at greater risk of developing the following conditions
- Hypertension (high blood pressure)
- Heart disease
- Irregular heart beat (arrhythmia)
- Due to feeling sleepy throughout the day, there can be a propensity to fall asleep while driving, clearly potentially dangerous.
How is OSA diagnosed?
As there are many reasons for disturbed sleep, diagnosing OSA can be difficult. The doctor will first obtain a detailed history of the problem and will examine the throat for signs of narrowing. It may be helpful for a partner or other household member to be present, as they will be able to explain things that the patient is often unaware of.
Polysomnography is the main medical test undertaken to diagnose OSA. This involves an overnight stay in a special sleep clinic. Before going to sleep for the night, the person is attached to a number of leads to monitor what happens during sleep.
OSA cannot be cured but it can be managed. The two main treatment options are lifestyle changes and CPAP (continuous positive airway pressure).
In cases of mild OSA, lifestyle changes may lead to improvement in the condition.
- Weight loss - as even a small loss in weight can improve symptoms
- Avoiding alcohol for at least a few hours prior to going to sleep
- Avoiding sleeping tablets or tranquillisers
- Use measures to assist sleeping on the side, as OSA can often be worse when sleeping on the back
CPAP (Continuous positive airways pressure)
This is the treatment of choice for OSA. It necessitates the person wearing a mask over their nose while they sleep. An air compressor attached to the mask continuously forces air through the nasal passages. The pressure used is just enough to prevent the airway from collapsing during sleep. The amount of pressure required to maintain an open airway varies with each individual.
For further information log onto www.sleepapnoeanz.org.nz