Obstructive sleep apnoea syndrome

Patients who are tired all the time may have obstructive sleep apnoea, says Dr Harry Brown

Many patients complain of being tired all the time. Some complain of snoring, others of interrupted sleep.

Within this group are some with obstructive sleep apnoea syndrome, a condition resulting from partial or complete closure of the upper airways while asleep.

The asphyxia is sensed by the body and an arousal is generated, kick-starting the breathing cycle and resumption of normal airflow. This can lead to disruption of the sleep cycle and result in broken sleep. The patient may be unaware of this, but may present with daytime sleepiness and other problems.

The syndrome affects 4 per cent of men and 2 per cent of women in middle age. Awareness is increasing but  many cases go undiagnosed.

Pathogenesis
The fundamental problem in obstructive sleep apnoea is a block at the upper airway, (usually at the level of the oropharynx). Complete blockage of the airways results in apnoea; if there is partial blockage this can lead to snoring, while near occlusion results in hypopnoea.

At the onset of sleep there is a normal response by the respiratory muscles to reduce activity. This may be low enough to close off the upper airway and cause the obstruction. In turn, because of the lack of oxygen, a lighter element of sleep is induced (a microarousal) and respiratory effort increases to reopen the airways.

Symptoms
Loud snoring and excessive daytime sleepiness are significant symptoms. Occasionally the person may wake and complain of poor quality of sleep or feeling as if they have been choking.

The interrupted sleep cycle, probably not noticed by the patient, can lead to symptoms when the person is awake, including feeling continually tired, having impaired intellectual function and easily falling asleep.

This could just mean falling asleep while watching television, but it can become much more of a problem. Some patients with established obstructive sleep apnoea have been shown to have reduced driving ability and to be at increased risk of car accidents.

Such patients should be warned not drive if feeling tired. They should inform the Driver and Vehicle Licensing Agency and their insurance company of their diagnosis.

Risk factors
During inspiration when sleeping, the normal pharyngeal muscular tone is lost and the pharynx collapses. Anyone with a narrowed upper airway because of a physical abnormality, for example a large tongue, small chin, nasal obstruction, enlarged tonsils or overweight, may be at risk of developing the condition.

Other risk factors include excess alcohol intake, sedatives and hypothyroidism.

Diagnosis
The upper airway should be assessed looking for any obvious abnormalities and weight and height measured to calculate the BMI. The patient’s neck size should also be measured; a neck larger than 43cm can be associated with obstructive sleep apnoea.

The Epworth Sleepiness Scale is a useful screening questionnaire.

Complications
Obstructive sleep apnoea is thought to be associated with hypertension as well as reduced left ventricular function. There has also been a suggestion that the condition may be associated with the development of vascular disease. A small percentage of patients will develop pulmonary hypertension, leading to right heart failure.

Treatment
Initially, attention should be paid to risk factors and weight loss if the patient is obese, as well as a reduction in alcohol intake and sedative. The patient should be put in touch with a self-help group.

Surgical correction of upper airway abnormalities such as nasal polyps or macroglossia may help.

Devices that fit in the mouth to reposition the tongue and jaw, increasing the size of the upper airway, can be useful.

Nasal continuous positive airways pressure (CPAP) is the most effective treatment. This provides an airway splint and increases the intra-airway pressure, avoiding an upper airways collapse and sustaining the patency of the airway.

Dr Brown is a GP in Leeds 

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