The investigation of sleep disordered breathing: seeing through a glass, darkly?

Timely diagnosis and treatment of obstructive sleep apnoea (OSA) in childhood is important to prevent morbidity and increased healthcare utilisation.1 In this issue, Burke et al2 highlight an important clinical question—how to best diagnose OSA in children, asking the question: is one night of oximetry enough? They note the limited availability of polysomnography, the international gold standard diagnostic test3 for OSA and that pulse oximetry is widely available.However, widespread availability of oximetry risks widespread misinterpretation. It is crucial to understand that not all oximeters are ‘born equal’ and the technology available may have significant limitations. The diagnostic yield of any oximeter will depend crucially on the device used and its settings, the scoring criteria applied to the trace, alongside the clinical interpretation of the data. Modern oximeters are able to detect and remove motion artefact, which is critical in restless young children (figure 1). Oximeters need to be set with short averaging times (usually maximum 3?s) to avoid smoothing out of brief desaturation events (figure 2). McGill scoring criteria are recommended with a score >1 (three or more clusters of desaturation events ?4% and at least three desaturations to <90%) being indicative of OSA,3 but as noted by Burke and colleagues,