Sleep on the cheap: the role of overnight oximetry in the diagnosis of sleep apnoea hypopnoea syndrome

The obstructive sleep apnoea hypopnoea syndrome (SAHS) has been recognised for over 30 years and an effective treatment—namely, nasal continuous positive airway pressure (nCPAP)—has been available for almost 20 years. Research into SAHS has risen exponentially during this time, providing us with greater understanding of the epidemiology, pathophysiology, and morbidity associated with the disease. Despite this research, the most cost effective pathway for the diagnosis and management of SAHS has yet to be established and remains the subject of debate. The gold standard diagnostic test for SAHS is overnight multichannel polysomnography (PSG) which enables detection of obstructive apnoeas, hypopnoeas, and arousals. However, PSG has several drawbacks. It is an expensive system to set up and run. The sleep laboratory is an artificial environment and some patients have a disturbed sleep pattern due to the foreign setting and thus interpretation of the PSG findings in these patients is problematic. The definition and quantification of apnoeas, hypopnoeas, and arousals remain subjects of debate.1-3 The apnoea hypopnoea index (AHI) increases in normal subjects with age, has moderate interobserver variation, and is poorly correlated with symptoms of excessive daytime somnolence.4 5 Thus, despite full PSG, identification of those patients with SAHS who benefit …