Continuous positive airway pressure

The most effective therapy for obstructive sleep apnoea is continuous positive airway pressure (CPAP). CPAP works by splinting the upper airway open. It can significantly reduce the number of apnoea and hypopnea events, and reduce daytime sleepiness. With good adherence, it can also improve mental health outcomes.

Consider CPAP for patients with:

• severe obstructive sleep apnoea—apnoea–hypopnoea index of more than 30 events per hour or hypoxic burden (percentage of sleep time during which oxygen saturation measured by pulse oximetry [SpO₂] is less than 90%) of more than 5%
• symptoms of daytime dysfunction and moderate obstructive sleep apnoea (apnoea–hypopnoea index of more than 5 events per hour or hypoxic burden of approximately 1 to 5%)
• obstructive sleep apnoea and hypertension—CPAP appears to produce a clinically significant reduction in blood pressure. Patients without significant sedation may prefer to manage hypertension with lifestyle modifications or drug therapy (see Blood pressure reduction). If blood pressure remains elevated despite lifestyle modifications or drug therapy, reassess whether the patient may benefit from CPAP.

The effect of CPAP on cardiovascular events and mortality in patients with coexisting obstructive sleep apnoea and cardiovascular disease is unclear. Benefit has been shown in some observational studies, but a randomised controlled trial did not find any benefit¹.

For a patient with mild to moderate obstructive sleep apnoea without daytime dysfunction, with or without cardiovascular disease, a ‘watch and wait’ approach is reasonable. Consider general measures (eg weight loss) to improve sleep and prevent progression to symptomatic disease.

CPAP is usually started in a specialist clinic or by a general practitioner with expertise in CPAP. The clinic can assist with optimising the mask interface, controlling leaks and fitting chin straps. Managing common problems with long-term CPAP summarises some common problems that occur with CPAP. CPAP machines are expensive; therefore, patients may prefer to trial the treatment by renting a CPAP machine, if possible, before purchasing one.

The airway pressure required to prevent obstructive apnoea and hypopnoea varies between patients. The pressure can be titrated during a second sleep study (the CPAP titration study), or using an automatic titrating CPAP machine. In symptomatic patients, do not delay starting treatment to await a titration study. Consider starting the patient on either a standard rate of 10 cmH₂O, or a rate based on 10% of the patient’s body weight (eg start a 60 kg patient on 6 cmH₂O) until a titration study can be performed.

In patients who remain symptomatic with CPAP treatment, consider a repeat sleep study to identify leaks, changes in pressure requirements, or other disorders requiring independent treatment (eg restless legs syndrome).

Patient information about CPAP is available from the Sleep Health Foundation website.