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Obstructive Sleep Apnoea
Obstructive sleep apnoea (OSA) was first described in patients with Pickwikian Syndrome (see below), but it can also occur in subjects that are not obese and that do not have any abnormal ventilatory disorders.
The Pickwikian syndrome is defined as moderate to severe obesity, alveolar hypoventilation (reduced amount of air entering the pulmonary alveoli [air sacs in the lungs]), prolonged drowsiness, twitching, cyanosis (dark bluish to purplish coloration of the skin), periodic breathing and secondary polycythemia (excessive number of red blood cells in the blood). The origin and development of this syndrome is unknown, studies have shown that it can occur in non-obese patients as well.
The following can contribute/be associated with sleep apnoea (cessation of breathing): obesity, short thick neck, reduction in muscle tone of the soft palate, the uvula (the small conical flesh tissue haging from the centre of the soft palate), and the pharynx. The upper airway may be narrowed by enlarged tonsils, a deviated nasal septum, nasal polyps or congenital abnormalities.
During an episode of sleep apnoea, the individual's upper airway is narrowed by fat build up or relaxed muscles in the back of the throat. When the individual tries to inhale, he/she creates a suction and causes the airway to collapse (See image below). The individual is then unable to breathe for 10 seconds to 1 minute. During this time there is a reduction of oxygen uptake and an accumulation of carbon dioxide in the blood. In response to the brain wakes the individual up just enough to tighten the airway muscles and reopen it. The individual may gasp as he/she begins to breathe again. Because people that suffer from sleep apnoea do not sleep properly and are more sleepy during the day, they are 3 times more likely to have a motor vehicle accident.
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Blocked airway in a patient with sleep apnoea.
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Sleep apnoea is characterised by 30 or more apnoeic episodes during the night. Sleep apnoea can be divided into:
Central |
Respiratory movements are absent and no oro-nasal airflow |
Equal distribution between sexes |
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Obstructive |
Diaphragm and chest wall move with changes in intrathoracic pressure, there is no airflow obstruction at the mouth or nose
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10 times more common in males than females, mostly occurs in post-menopausal
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Mixed |
Respiratory movement and airflow are absent early in the episode followed by resumption of breathing |
Apnoea index is a measure of the number of apnoeas/hour, it is used to estimate the severity of sleep apnoea, a measure of 5 or less per hour is normal in adults.
Physiological vs Pathological Sleep Apnoea
In healthy adults brief apnoeas occur, these are common following body movements and during REM sleep. In infants and premature babies, apnoeas are more frequent in babies with low weight. In children (9-13 years), the occurrence is between 3-40 apnoeas during the night.
As the individual gets older, the number of apnoeas increases; these are more common in obese and snorers. These apnoeas are short, may happen less than 10 episodes/night and are more common in males than females.
Interesting fact.... |
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Sleep apnoea is considered to be pathological in humans, however in some animals it means energy conservation. Elephant seal pups stop breathing every time they fall asleep, and apnoea may last as long as 20 mins. |
Symptoms
| Snoring | Abnormal sleep behaviour |
| Memory impairment | Morning headaches |
| Changes in mood | Excessive somnolence |
Characteristics of untreated sleep apnoea
| Cardiovascular and respiratory complications | Hypoxia (decrease oxygen levels in the blood) |
| Pulmonary hypertension | Arrhythmias |
| Right heart failure | Hypertension |
| Respiratory failure | Impotence |
| Depression | Tiredness |
Treatment
To evaluate if the patietn has sleep apnoea he/she will be sent to a sleep laboratory to have a diagnostic sleep study. Once completed, the study will give the doctor an indication of the type of sleep apnoea and the severity.
There are two main ways of treating sleep apnoea:
1. Mandibular advancement splints
2. CPAP (continuous positive airways pressure).
In mild cases of sleep apnoea weight loss may help.
