Once OSAS is diagnosed, its treatment is relatively straightforward. Lifestyle measures, such as weight loss, alcohol consumption and smoking should be addressed. However, the commonest and most rapidly effective treatment for moderate-to-severe OSAS is with nocturnal continuous positive airway pressure (CPAP) (figure 2). This is usually delivered through the upper airway using a mask over the nose, or the nose and mouth, attached by a hose to an air compressor that generates a flow of air at positive pressure throughout the breathing cycle, of sufficient magnitude to keep the upper airway open and prevent it from collapsing. CPAP thereby acts as a pneumatic splint for the upper airway. Unfortunately, CPAP does not permanently restore or correct the problems leading to upper airway obstruction; it therefore needs to be applied throughout each night for maximum effect. If well tolerated and used consistently, CPAP has been shown to reverse or ameliorate the somnolence, cognitive deficit, reduced health status, hypertension and metabolic disturbances associated with OSAS.

In snoring or mild OSAS, an alternative therapy may be used: the mandibular repositioning device (MRD) (figure 3). This device may also be useful in patients who cannot or will not tolerate or adhere to CPAP. Although less reliably effective than CPAP, MRDs can be used as adjuncts to CPAP therapy. They should always be constructed by a trained professional.

Other potential treatments include: tonsillectomy, where appropriate and especially in children; upper airway surgery in exceptional cases where significant craniofacial abnormalities are present; and bariatric surgery for those in whom severe obesity is the primary contributor to OSAS. Stimulation of the hypoglossal nerve through implanted  electrodes is increasingly being trialled in patients with OSAS who fail to respond to more conventional modes of therapy, though this treatment remains very much under development. No effective pharmacological therapies are currently available.

As with other forms of long-term treatment, adherence requires application of the specific treatment by trained personnel and long-term follow-up.

In few other chronic medical conditions is a simple treatment so rapidly effective and cost-efficient as CPAP in OSAS.

See the entire Sleep breathing disorders Chapter