Describe obstructive sleep apnoea with its assessment and management.

Nature and Consequences

• The mechanism — during sleep the pharyngeal dilator muscles (chiefly genioglossus) lose tone, and the pharynx, having NO rigid skeleton, collapses under the negative inspiratory pressure. Obstruction is worst in REM sleep, when muscle atonia is greatest, and when supine
• The cycle repeats: obstruction → hypoxia and hypercapnia → increasing respiratory effort → arousal (not remembered) → airway reopens → sleep resumes → obstruction — often hundreds of times a night

Assessment and Management

• History — from the patient and, crucially, from the partner.
• From the patient — unrefreshing sleep, morning headache, dry mouth, nocturia, poor concentration, irritability, reduced libido, and daytime sleepiness
• Ask about driving and occupation — this is a legal and safety obligation, not an optional question. Patients must be advised not to drive when sleepy and, where relevant, to inform the licensing authority
• The epworth sleepiness scale quantifies subjective sleepiness (8 situations, scored 0 to 3, maximum 24; above 10 is abnormal) — but it correlates poorly with severity and is a screening aid, not a diagnostic test
• The stop-BANG questionnaire is a useful screening tool — Snoring, Tiredness, Observed apnoea, blood Pressure, BMI, Age, Neck circumference, Gender
• Examination — BMI and neck circumference; blood pressure; nasal examination; the modified mallampati grade; tonsil size; retrognathia and dental occlusion; tongue size; and flexible nasendoscopy with the MULLER manoeuvre to assess the level of collapse
• Drug-induced sleep endoscopy (DISE) assesses the site and pattern of collapse under sedation, and is used to select patients for surgery
• Polysomnography is the gold standard, giving the apnoea-hypopnoea index (AHI) — the number of events per hour: mild 5 to 15, moderate 15 to 30, severe above 30; with oxygen desaturation indices and sleep architecture
• Home sleep apnoea testing is adequate for many uncomplicated adults and is far more accessible
• Check TSH, and consider acromegaly where the features suggest it
• Management — conservative measures apply to everyone: weight loss.
• Continuous positive airway pressure (CPAP) is the treatment of choice for moderate and severe disease — it acts as a pneumatic splint holding the pharynx open
• It is highly effective, improving sleepiness, blood pressure and accident risk; but adherence is the limiting factor, and depends on mask fit, humidification, treating nasal obstruction, and proper follow-up and support — which is where most CPAP failure actually originates
• Mandibular advancement devices — for mild to moderate disease, simple snoring, and CPAP intolerance; they advance the mandible and tongue base, and require adequate dentition
• Surgery is for selected patients, chiefly where there is a correctable anatomical obstruction or CPAP has genuinely failed:
• Adenotonsillectomy, which is the first-line treatment in children and is highly effective; and is useful in adults with large tonsils
• Nasal surgery (septoplasty, turbinate reduction), which rarely cures OSA but improves CPAP tolerance — an important and honest distinction
• Uvulopalatopharyngoplasty (UPPP) and modern palatal procedures, whose results are variable and depend heavily on patient selection
• Tongue base procedures, maxillomandibular advancement (which is highly effective but major surgery), and hypoglossal nerve stimulation, a newer option for selected patients
• Tracheostomy, which is curative by bypassing the obstruction and is reserved for life-threatening disease where nothing else is tolerated
• Warn about anaesthetic risk — patients with OSA are sensitive to opioids and sedatives and need careful postoperative monitoring.
• Ask the partner, not just the patient; witnessed apnoeas and choking arousals cannot be self-reported
• Ask about driving and occupation, which is a safety and legal obligation rather than an optional question
• Respiratory effort is preserved, which is what distinguishes obstructive from central apnoea
• The pharynx has no rigid skeleton, which is why it collapses when dilator tone is lost in sleep