‘Sleep Apnoea’ is a condition in which you develop ‘apnoea’ during sleep. Apnoea means ‘stoppage of breathing’. In fact, your breathing may not completely stop, but become very shallow, to the extent that you are not able to get adequate amount of air in to your lungs (technically known as ‘hypopnoea’).
Apnea and hypopnea can occur either because the air passage in your throat is obstructed (when it is known as ‘Obstructive’ sleep apnoea or OSA) or because your brain does not send signals to your chest muscles instructing the chest to expand to fill your lungs (known as ‘Central sleep apnoea’). Obstructive Sleep Apnoea is the commonest type of Sleep Apnoea.
Obstructive Sleep Apnoea is the most common reason for referral to a sleep clinic. It is a common cause of Excessive Daytime Sleepiness.
‘Sleep Apnoea’ refers to ‘apnoea’ occurring during sleep. Apnoea is a Latin term which means ‘stoppage of breathing’. In fact breathing may not completely stop, but become very shallow, to the extent that one is not able to get adequate amount of air in to the lungs (technically known as ‘hypopnoea’).
Sleep apnoea is usually caused by blockage of the air passage in the throat when it is called ‘Obstructive’ sleep apnoea. or OSA). It can also occur when the brain stops sending signals to the chest muscles instructing the chest to expand to fill the lungs. This is known as ‘Central sleep apnoea’.
The air passage in the throat is normally quite narrow but is sufficient to allow flow of air during breathing. The throat becomes narrower when one gains weight (due to collection of fat in the tissues). It can also be narrow if the bony structure of the jaws is comparatively small. Even when the passage is narrow, the normal tone of the muscles in the throat keeps the passage open during waking hours. However, the muscle tone goes down during sleep. This causes progressive narrowing and eventually complete closure of the airway during sleep.
When the airway narrows during sleep the person starts to snore. As sleep deepens, the narrowing become more pronounced, causing one to snore loudly. With further narrowing, the airflow becomes shallow, and the snoring may become less marked. Eventually when the throat gets fully blocked there is no airflow and breathing stops.
When breathing stops, the blood oxygen level goes down, often to dangerous levels. These events are sensed by the brain which makes the person wake up briefly. As soon as this happens, the muscles regain their tone and the throat opens up, and the sufferer wakes up briefly. The airway opens with a snorting sound, followed by rapid breathing. Such awakenings are very brief and is usually not remembered. A bed partner is likely to observe this as ‘breath holding’ episodes. As soon as breathing resumes, the person falls back to sleep, only for the cycle of events to repeat.
These repetitive events breaks the continuity of sleep and the person does not feel refreshed on waking up. This leads to excessive sleepiness and fatigue/tiredness in the waking hours. Many other symptoms can occur as a result of sleep apnoea. These include waking up with choking and gasping, restless sleep, need to visit the toilet often in the sleep period and others.
It is often quoted that OSA affects 4% of middle-aged men and 2% of middle-aged women. However, this statistic is rather old and the prevalence of OSA is much higher. More recent estimates indicate that OSA affects approximately 50% of men and 23% of women in middle-age.
Despite it being very common, many patients remain unaware of the diagnosis. It has been estimated that up to 90% of people with OSA remain undiagnosed.
Diagnosis:
Diagnosis of OSA requires a ‘sleep study’. Most services in the UK use home sleep studies to diagnose sleep apnoea. In some cases, more complex studies in a sleep laboratory may be needed.
