Respiratory

Obstructive Sleep Apnoea

Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is recurrent upper-airway narrowing or closure during sleep, causing sleep fragmentation and intermittent hypoxaemia; diagnosis uses sleep history and objective sleep testing, while treatment is tailored to symptoms, severity, comorbidity, safety risk and treatment adherence.

In a nutshell

OSAHS is recurrent sleep-related upper-airway collapse causing sleep fragmentation, intermittent hypoxaemia and daytime sleepiness or impaired vigilance. Suspect it from snoring, witnessed apnoeas, choking, unrefreshing sleep, morning headache, nocturia or unexplained fatigue; confirm with objective sleep testing. Treat with lifestyle measures plus CPAP when indicated, and address driving risk, adherence and OHS separately.

Classic presentation

Habitual snoring with witnessed apnoeas or choking, unrefreshing sleep and daytime sleepiness, often with obesity or treatment-resistant hypertension.

Key points

The pharynx collapses when sleep-related loss of dilator-muscle tone meets anatomical narrowing; repeated arousals reopen it but fragment sleep.
Use the Epworth Sleepiness Scale in assessment but not alone to decide referral; obtain collateral history and assess driving/vigilance risk.
Offer home respiratory polygraphy as the first-line objective test. AHI severity: mild 5 to <15, moderate 15 to <30, severe 30 or more events/hour.
Fast-track vocational/vigilance-critical workers, unstable cardiovascular disease, pregnancy, urgent major-surgery assessment and non-arteritic anterior ischaemic optic neuropathy.
Offer fixed-level CPAP for moderate or severe OSAHS; for symptomatic mild OSAHS offer CPAP with priority factors or after lifestyle advice is unsuccessful/inappropriate.
A mandibular advancement splint is a selective alternative when CPAP is declined or not tolerated; check age, dentition and periodontal health.
OHS requires obesity, awake hypercapnia and sleep-related breathing abnormality; severe OHS-related OSAHS starts with CPAP, while persistent hypercapnia or non-severe OSAHS may require NIV.
Anyone with sleepiness that may impair driving must stop driving; moderate/severe OSAHS with excessive sleepiness must be notified to DVLA, and mild or suspected disease must be notified if control is not achieved within 3 months.

First-line investigation

Sleep and collateral history, Epworth/STOP-Bang assessment and home respiratory polygraphy; add blood gases and carbon-dioxide monitoring when OHS or overlap syndrome is suspected.

Management

Protect against sleepiness-related harm

Advise anyone whose sleepiness may impair driving not to drive or perform vigilance-critical work; prioritise vocational drivers and other high-risk occupations for sleep-service assessment.^4,1

Confirm OSAHS and identify OHS

Use sleep and collateral history, Epworth with optional STOP-Bang, home respiratory polygraphy and AHI-based severity; check awake blood gases when obesity hypoventilation or overlap syndrome is possible.^1,6

Change risk factors and support tolerance

Address weight, physical activity, alcohol and sedatives, treat rhinitis, provide specialist education and support adherence to CPAP, splints or positional devices.^1,5

Choose pressure or oral treatment by phenotype

Offer fixed-level CPAP for moderate/severe OSAHS and selected symptomatic mild OSAHS; use a suitable mandibular advancement splint when CPAP is declined or not tolerated, and use NIV rather than assuming CPAP will suffice when OHS physiology persists.^1,3

Prove control and maintain safety

Review symptoms, vigilance, AHI/ODI, adherence, equipment and side effects within 1 month of CPAP, then annually once optimised; follow DVLA review and notification requirements for drivers.^1,4

Exam traps

A low Epworth score does not exclude OSAHS and should not override witnessed apnoeas, comorbidity or safety risk.
Oximetry alone may be insufficient, especially in heart failure or chronic lung disease; use respiratory polygraphy or polysomnography when indicated.
Do not treat OHS as uncomplicated OSAHS: confirm awake hypercapnia and consider NIV if CPAP does not correct symptoms, hypercapnia or respiratory indices.
A mandibular advancement splint requires suitable dental and periodontal health; positional devices are unlikely to treat severe OSAHS.
Excessive sleepiness and driving restrictions are safety issues even before a diagnosis is confirmed; apply the current DVLA rule, not a memorised threshold.

Illustrations

The obstruct–arouse–reopen cycleTime-course illustration of an obstructive event: airway closure, respiratory effort, falling oxygen saturation, arousal, airway reopening and sleep fragmentation.PassFinals · original

CPAP splinting the airway openIllustration of a CPAP mask delivering positive airway pressure that holds the pharynx open through the sleep cycle.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.