SYMPTOMS OF OBSTRUCTIVE SLEEP APNOEA (OSA)

Many of the features of OSA are not a direct result of snoring per se but are a consequence of obstructive events during sleep which cause blood oxygen levels to drop to dangerously low levels. The absolute priority given to the body’s need for oxygen can be put into perspective when we consider that a healthy human can survive without food for several weeks, survive without water for days, but will die within minutes of oxygen deprivation. Not surprisingly, snoring is the most prevalent symptom of OSA, occurring in about 95% of patients with the syndrome. A cluster of other symptoms is also very common and will be found to a greater or lesser extent depending on the number of apnoeas experienced in a night and the severity of oxygen deprivation.

Sleepiness

The patient with OSA is classically prone to daytime sleepiness, often found slumped in front of a television or at the table during a dinner party. Most alarming are those patients who seek help after falling asleep behind the wheel of a car or while operating dangerous machinery. The tendency to fall asleep during the day is attributed to poor quality sleep at night caused by arousals associated with each obstructive event. Anyone who has observed a patient with OSA will be aware of the repetitive nature of airway obstruction and the resulting sleep fragmentation. Airway collapse is followed by increasing respiratory efforts to overcome the obstruction and to relieve intolerably low blood oxygen levels (hypoxaemia). The degree of sleep disturbance probably relates to the severity of the apnoeic period; some patients experiencing a mild arousal from REM to NREM states, while others will be fully awakened by such an episode. Sufferers of advanced OSA are caught in a cruel cycle. The relentless process of obstruction and arousal many times a night leaves the sufferer sleep deprived, lethargic and irritable. He cannot help trying to make up for lost sleep at every opportunity yet it is sleep which sets in motion events such as loss of upper airway tone which in turn result in obstruction and arousal.

Personality changes and memory loss

Memory deterioration and an inability to concentrate are symptomatic of sleep apnoea. The reasons for this are not completely understood but it is suggested that they result from the cumulative damage of perhaps many years of hypoxaemia during sleep. The disturbed sleep patterns of OSA are also likely to result in such impairment, and there is little doubt that both hypoxaemia and sleep fragmentation contribute to the problem of impaired memory and learning ability. As a consequence of the social readjustments that have to be made and the behavioral and personality changes which may arise, these people may be seen in the first instance by Psychiatrists for treatment of depressive illness.

Physiological changes

The behavioral changes which become increasingly apparent to spouse and friends are accompanied by potentially serious physiological changes, particularly to the heart and circulatory system. Some of the changes occur rapidly in response to each of the many obstructive events during sleep. Blood pressure, for example, is normally slightly lower at night than during the day, but in OSA blood pressure rises during apnoeic periods. There can also be quite startling changes in heart rate when the hypoxaemia associated with obstruction induces a slower heart rate (bradycardia) followed by an increase (tachycardia) when normal breathing is resumed. Apnoea may also be associated with irregular heart beats or arrhythmias, which are potentially life threatening.

Superimposed over the transient yet dramatic changes which occur during sleep are several long term and persistent abnormalities. Blood pressure often remains high and may be the first measurable symptom observed at an initial consultation. Increased blood pressure and other changes to the blood circulatory system also affect the heart which may become enlarged in an effort to overcome the harmful effects of hypoxaemia on the cardiovascular system.

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