RespiratoryTier 2Topic

Diagnostic sleep studies

The tests

Polysomnography (PSG) - the gold-standard diagnostic test for sleep-disordered breathing and other sleep disorders, recording EEG, EOG, EMG, airflow, respiratory effort, oximetry, and ECG overnight
Full in-laboratory PSG remains the reference standard; home sleep apnoea testing (limited-channel, usually airflow/effort/oximetry only) is increasingly used for straightforward suspected OSA without significant comorbidity

Definitions

Apnoea (complete cessation of airflow >=10 seconds) and hypopnoea (partial reduction with desaturation/arousal) are counted and expressed as the Apnoea-Hypopnoea Index (AHI, events/hour)

Severity and home testing

AHI <5 = normal; 5-15 = mild OSA; 15-30 = moderate; >30 = severe
Home sleep apnoea testing tends to underestimate AHI (no EEG to confirm sleep, may miss events during brief wake) - not suitable for suspected central sleep apnoea, significant cardiorespiratory disease, or when other sleep disorders are suspected (these need full PSG)

Acting on the result

AHI severity, alongside symptom burden and comorbidity (cardiovascular disease, occupational driving risk), guides the decision to treat with CPAP

Conditions

Obstructive sleep apnoea, central sleep apnoea, REM sleep behaviour disorder (needs video-PSG), periodic limb movement disorder

Repeat studies

Repeat PSG/sleep study is used to titrate CPAP pressure and confirm treatment efficacy, not only for initial diagnosis

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