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Sleep-related disorders of breathing 

Sleep-related disorders of breathing

Chapter:
Sleep-related disorders of breathing
Author(s):

J.R. Stradling

and S.E. Craig

DOI:
10.1093/med/9780199204854.003.180502

A relevant case history from Oxford Case Histories in Respiratory Medicine has been added to this chapter.

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date: 27 March 2017

Obstructive sleep apnoea (OSA) and other sleep-related breathing problems significantly impair the functioning of about 0.5 to 1% of the population and are becoming increasingly common.

Obstructive sleep apnoea

OSA in adults is commoner in men than women (3–5:1) and usually caused by obesity (BMI typically >30 kg/m2) and fat deposits in the neck area (typically collar size of 17 inches (43 cm) or more). This external loading can be fended off during wakefulness but not during sleep, when the withdrawal of postural muscle tone allows the pharyngeal dilators to be overwhelmed, leading to excessive narrowing or collapse of the airway, with consequent apnoea. The most important consequence of sleep-induced upper airway narrowing is sleep fragmentation.

Clinical features—there is a continuum from light intermittent snoring through to severe, all-night, OSA. The main symptom of OSA is daytime hypersomnolence, which correlates broadly with the degree of sleep disruption. Other common symptoms are loud snoring, restless or unrefreshing sleep, observed apnoeas, nocturia, and apparent personality change.

Diagnosis—it is important to ask the correct questions to assess sleepiness; a well validated and simple way to do this being with the Epworth Sleepiness Scale, in which the patient is asked to state how likely they are to doze off or fall asleep in a number of ordinary situations, e.g. sitting and reading. Patients scoring higher than normal generally merit further investigation in the form of some type of sleep study to (1) assess sleep fragmentation, (2) establish if a respiratory problem is responsible, and (3) decide if upper airway obstruction is the primary cause. Classical OSA, observed with a simple commercially available monitoring system, causes a snoring–silence–snoring pattern of sleep (from room microphone) together with body movements (from video) and oscillations in the pulse and SaO2 (from oximeter). Full polysomnography can provide much further information, but is not generally required in straightforward cases.

Management—mild symptoms may resolve with simple treatments and advice as follows: (1) learn to sleep on your side and avoid sleeping on your back, (2) no alcohol after 18.00 h, (3) no sedatives, (4) lose weight, (5) stop smoking, (6) keep the nose as clear as possible. However, if OSA and symptoms are severe, there is only one fully effective therapy—nasal continuous positive airway pressure (NCPAP): this involves wearing a small mask over the nose while asleep, with the air pressure kept at a fixed level above atmospheric (usually about 10 cmH2O) by a pump, sufficient to splint open the pharynx and resist collapse, allowing unobstructed breathing and undisturbed sleep.

Prognosis—many patients with OSA have visceral obesity and the metabolic syndrome (hypertension, insulin resistance, hyperlipidaemia), and their vascular mortality is higher than average. However, there is no controlled interventional data to support the routine use of NCPAP to reduce vascular risk in patients with OSA who would not otherwise want to use the treatment for relief of daytime sleepiness.

Sleep-induced hypoventilation and central sleep apnoea

Aetiology—breathing during sleep may decrease because of a reduction in central output to the respiratory muscles, which can be caused by (1) absent ventilatory drive—Ondine’s curse, caused by congenital abnormality, brainstem damage, or blunting secondary to lung disease; (2) unstable ventilatory drive—at sleep onset, with hypoxaemia, altitude, heart failure; (3) REM-related oscillations—neuromuscular diseases, chest-wall abnormalities, and chronic airways obstruction; (4) reflex central apnoea—when pharyngeal collapse inhibits inspiration.

Clinical features—some of the central apnoeas disturb sleep and present with daytime sleepiness, such that they can be confused with OSA, whereas others tend to present with symptoms of respiratory failure, such as morning headaches with confusion, cyanosis, and ankle oedema.

Management—without treatment the chronic ventilatory failure associated with some neurological disorders (e.g. acid maltase deficiency, postpoliomyelitis syndrome, motor neuron disease, Duchenne dystrophy) usually progresses rapidly to death. Supporting breathing overnight can fully reverse ventilatory failure, and the response to treatment can be dramatic, with resolution of all symptoms, restoration of normal blood gases, and addition of decades of active life.

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