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Q1: Diagnosis & mechanism (2 min)
"A 52-year-old obese man snores loudly, has witnessed apnoeas and daytime sleepiness. What is this and what is happening overnight?"
- Diagnosis: obstructive sleep apnoea (OSA / OSAHS).
- Mechanism: during sleep the wakefulness drive to the pharyngeal dilator muscles (genioglossus, CN XII) is withdrawn; the airway narrows and collapses. Airflow stops while respiratory effort continues (straining against a closed airway).
- Progressive hypoxia + hypercapnia → chemoreceptor firing → a brief cortical arousal restores tone, the airway reopens with a loud snort, ventilation resumes and CO2 falls; sleep resumes and the cycle repeats dozens to hundreds of times a night.
- Mnemonic: "OSA = effort, no flow; CSA = no effort, no flow."
Q2: Scoring & severity (2 min)
"How do you confirm the diagnosis and grade the severity? Reproduce the key scoring systems."
- Polysomnography is the gold standard (EEG/EOG/chin EMG, airflow, respiratory effort, oximetry, ECG, leg EMG, position). Calculates the AHI.
- Severity (AASM/AASM–ICSD-3): mild 5–15, moderate 15–30, severe over 30 per hour.
- Epworth Sleepiness Scale (0–24): over 10 = excessive daytime sleepiness; 16+ severe.
- STOP-BANG: Snoring, Tiredness, Observed apnoea, blood Pressure, BMI over 35, Age over 50, Neck over 40 cm, male Gender. 0–2 low, 3–4 intermediate, 5–8 high risk.
Q3: Management ladder (3 min)
"Walk me through the management."
- All patients — weight loss (most effective reversible factor; 10% weight loss → ~20–30% AHI fall), sleep hygiene, avoid alcohol/sedatives, stop smoking, positional therapy, treat nasal obstruction.
- CPAP (gold standard) for moderate–severe OSA — pneumatic airway splint, 4–20 cmH2O. Effective use = at least 4 h/night on 70% of nights. Support adherence: mask fitting, humidification, ramp, pressure relief, follow-up.
- Mandibular advancement device — for mild OSA or CPAP-intolerant patients; protrudes the jaw; needs adequate dentition.
- Surgery — selected patients only: UPPP, maxillomandibular advancement, hypoglossal nerve stimulation (BMI under 32, CPAP failure), and bariatric surgery for morbid obesity (can remit OSA).
- Residual sleepiness on compliant CPAP — add modafinil/armodafinil (never as a substitute for CPAP).
Q4: OHS & overlap syndrome — the trap (2 min)
"Your patient is morbidly obese with a daytime PaCO2 of 52 mmHg and bicarbonate 32. What changed?"
- This is obesity hypoventilation syndrome (OHS): BMI over 30 + PaCO2 over 45 mmHg + sleep-disordered breathing.
- Do NOT use CPAP alone — use NIV / BiPAP (pressure support) to augment ventilation, plus aggressive weight loss.
- Overlap syndrome (OSA + COPD) — higher risk of pulmonary hypertension, hypercapnia and cor pulmonale; treat with CPAP ± long-term oxygen, avoid uncontrolled oxygen (CO2 retention).
Q5: Complications & the SAVE trial (2 min)
"What happens if you don't treat him? And does CPAP prevent heart attacks?"
- Untreated OSA → systemic hypertension (incl. resistant), atrial fibrillation, MI, heart failure, stroke, type 2 diabetes, road-traffic accidents, and increased mortality.
- SAVE trial (McEvoy 2016, NEJM): CPAP in moderate-severe OSA with established CVD did not reduce recurrent cardiovascular events — but did improve sleepiness and quality of life. Lesson: treat OSA early, before irreversible end-organ damage.
- Always screen for OSA in: resistant hypertension, paroxysmal AF, nocturnal angina, unexplained pulmonary hypertension, cryptogenic stroke, and road-traffic accidents.
Q6: Special situations (1 min)
"Children? Pregnancy? Peri-operative?"
- Children — adenotonsillar hypertrophy; adenotonsillectomy is first-line, CPAP if residual.
- Pregnancy — snoring/OSA raises gestational hypertension, pre-eclampsia, GDM risk; CPAP is safe.
- Peri-operative — anticipate a difficult airway and post-op respiratory depression; use short-acting agents, monitor in HDU, and continue CPAP throughout.