Elsevier

The Lancet

Volume 360, Issue 9328, 20 July 2002, Pages 237-245
The Lancet

Seminar
Obstructive sleep apnoea

https://doi.org/10.1016/S0140-6736(02)09464-3Get rights and content

Summary

Obstructive sleep apnoea is a disease of increasing importance because of its neurocognitive and cardiovascular sequelae. Abnormalities in the anatomy of the pharynx, the physiology of the upper airway muscle dilator, and the stability of ventilatory control are important causes of repetitive pharyngeal collapse during sleep. Obstructive sleep apnoea can be diagnosed on the basis of characteristic history (snoring, daytime sleepiness) and physical examination (increased neck circumference), but overnight polysomnography is needed to confirm presence of the disorder. Repetitive pharyngeal collapse causes recurrent arousals from sleep, leading to sleepiness and increased risk of motor vehicle and occupational accidents. The surges in hypoxaemia, hypercapnia, and catecholamine associated with this disorder have now been implicated in development of hypertension, but the association between obstructive sleep apnoea and myocardial infarction, stroke, and congestive heart failure is not proven. Continuous positive airway pressure, the treatment of choice for obstructive sleep apnoea, reduces sleepiness and improves hypertension.

Section snippets

Definitions

Severity of obstructive sleep apnoea is measured as the apnoea-hypopnoea index (AHI). An apnoea, defined as cessation of airflow for at least 10 s, is classified as obstructive or central on the basis of presence or absence of respiratory effort. A consensus conference (Chicago criteria) provided a definition of hypopnoea as including one of three features: substantial reduction in airflow (>50%), moderate reduction in airflow (< 50%) with desaturation (>3%), or moderate reduction in airflow (<

Epidemiology

Young and colleagues23, 24 showed that 4% of men and 2% of women in a middle-aged North American population had symptoms of obstructive sleep apnoea and an AHI of greater than 5 events per hour of sleep. 24% of North American men and 9% of women had an AHI greater than 5 events per hour of sleep, but only those with excessive daytime sleepiness were included in the former statistics. However, recently cardiovascular risk has been associated with AHIs that were previously deemed to be within the

Clinical presentation

Sleep apnoea should be suspected in individuals with the signs and symptoms outlined in panel 3.35 Measures of obesity, witnessed apnoeas, and prominent snoring are the strongest of these associations. Although patients with obstructive sleep apnoea are usually obese older men, more subtle presentations can occur. For example, roughly 30% of patients with obstructive sleep apnoea are not obese, but many physicians do not pursue this diagnosis in individuals who are not overweight. In view of

Pathophysiology—the pharyngeal airway

Although most mammals have rigid skeletal support of the pharyngeal airway, patency of the human upper airway is maintained mostly by muscle activation and soft tissue structures.10, 11, 12 The evolution of speech is thought to have needed substantial laryngeal motility, leading to a hyoid bone without rigid support and a vulnerable airway. Variables tending to promote pharyngeal collapse include negative pressure within the airway (eg, during inspiration) and positive pressure outside the

Alternative hypotheses

Although such pathophysiological mechanisms are generally accepted, other hypotheses have also been developed. First, the pharyngeal dilator muscles of patients with apnoea might become injured or fatigued over time by the repetitive collapse with high negative pressures. Muscle dysfunction or afferent nerve injury could thus evolve and have a perpetuating role in the cause of apnoea.63, 64, 65, 66 Although abnormalities have been identified in certain palatal muscles, dysfunction of the entire

Consequences

Once apnoea or hypopnoea develops, arousal from sleep is generally needed to stop the event (figure 2).68 Although the activity of the dilator muscle activity increases as apnoea progresses, the increases are generally insufficient to re-establish pharyngeal patency.69, 70 Thus, the patient repeatedly arouses from sleep throughout the night. The precise stimulus to arousal is debated, with most investigators suggesting some combination of increasing respiratory effort in association with

Diagnosis

A frequently used strategy for diagnosis of obstructive sleep apnoea is overnight polysomnography in a sleep laboratory, which generally incorporates recording of electroencephalogram, electro-oculogram, chin electromyogram,79 snoring (microphone), thermistor, electrocardiogram, pulse oximetry, and tibialis anterior electromyogram.79 Measurement of nasal pressure may also be helpful in identification of high inspiratory resistance and more subtle respiratory events.21, 22, 80 Results of many

CPAP

CPAP treatment remains the treatment of choice for obstructive sleep apnoea because of its effectiveness in elimination of apnoea and improvements in apnoea sequelae.3, 9, 17, 97 Results of randomised trials have shown substantial improvements in both sleepiness and neurocognitive performance of patients on nasal CPAP compared with those on placebo or subtherapeutic CPAP. In addition, decrements in blood pressure have been shown with CPAP treatment. Thus, treatment of obstructive sleep apnoea

Conclusion

The rising number of people with obesity will probably make obstructive sleep apnoea an increasingly important public-health problem, especially in view of the neurocognitive and cardiovascular sequelae associated with this disorder. Furthermore, CPAP has been established as the treatment of choice for obstructive sleep apnoea syndrome on the basis of randomised controlled trials, and improvements in our understanding of the underlying mechanisms of obstructive sleep apnoea will hopefully lead

Search strategy and selection criteria

This review was derived from our own experience and research with this disease, plus PubMed searches of each sub-heading cross-referenced with obstructive sleep apnoea. We placed most emphasis on the most recent published work and randomised controlled trials, when available. When no such trial was available, we relied on the highest quality of the available evidence (eg, case-control studies and case series), plus expert opinion of ourselves and other researchers and clinicians.

rather than an

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