Obstructive Sleep Apnea

Patient: 52M, BMI 38, on amlodipine 10, lisinopril 40, chlorthalidone 25, BP still 152/94. Daytime somnolence (Epworth 18), witnessed apneas by wife, morning headaches. Sleep study: AHI 48, nadir SpO₂ 72%.

Key findings: Severe OSA (AHI > 30) causing resistant hypertension. OSA is the #1 secondary cause of resistant HTN. Nocturnal hypoxemia → sympathetic surges → sustained daytime HTN. Also increases risk of Afib, stroke, and sudden cardiac death.

Management:

• Auto-CPAP titration, start 4-20 cmH₂O auto-adjusting (most patients need 8-12 cmH₂O)
• Mask fitting is critical for compliance, trial nasal pillows, nasal mask, or full face mask based on preference
• Weight loss counseling, 10% weight loss can reduce AHI by 26-50%
• Recheck BP after 3 months of CPAP, may be able to reduce antihypertensives
• Screen for metabolic syndrome, T2DM (OSA independently worsens insulin resistance)

Teaching point: CPAP reduces BP by ~3-5 mmHg on average, modest but clinically meaningful in resistant HTN. The benefit is greatest in patients who use CPAP > 4h/night. Non-compliant patients get no benefit, making adherence counseling essential.

Patient: 64F, BMI 42, scheduled for elective knee replacement. STOP-BANG score 6 (high risk). Never had a sleep study. Anesthesia requesting clearance.

Key findings: High pre-test probability of OSA (STOP-BANG ≥ 5). Undiagnosed OSA increases perioperative risk: post-op respiratory depression from opioids, difficult intubation, hypoxemia, Afib, ICU admission.

Management:

• Home sleep apnea test (HSAT) or in-lab polysomnography before elective surgery
• If OSA confirmed: start CPAP pre-operatively (even 1-2 weeks of use reduces perioperative complications)
• Perioperative precautions: CPAP at bedside post-op, minimize opioids (use multimodal analgesia), continuous pulse oximetry, semi-upright positioning
• Avoid benzodiazepines (worsen upper airway collapse)
• Anesthesia alert: potential difficult airway, have video laryngoscope available

Teaching point: STOP-BANG is the validated screening tool for OSA: Snoring, Tired, Observed apnea, Pressure (HTN), BMI > 35, Age > 50, Neck > 40 cm, Gender male. Score ≥ 5 = high probability of moderate-severe OSA.

Patient: 58M, BMI 52, presents with progressive dyspnea, lower extremity edema, somnolence. ABG: pH 7.32, PaCO₂ 58, PaO₂ 52, HCO₃ 34. Hgb 18.2 (polycythemia). Echo: RV dilation, estimated RVSP 55 mmHg. Sleep study: AHI 62.

Key findings: OHS = obesity (BMI ≥ 30) + awake daytime hypercapnia (PaCO₂ > 45) + sleep-disordered breathing, without another cause of hypoventilation. Elevated bicarb = chronic respiratory acidosis with metabolic compensation. Polycythemia from chronic hypoxia.

Management:

• Bilevel PAP (BiPAP) with backup rate, preferred over CPAP in OHS (addresses both obstruction AND hypoventilation)
• Supplemental O₂ titrated to SpO₂ 88-92% (avoid over-oxygenation, may worsen hypercapnia)
• Weight loss: bariatric surgery referral (most effective long-term intervention for OHS)
• Diuretics for right heart failure (RV volume overload from chronic pulmonary HTN)
• Monitor ABGs, PaCO₂ should improve with consistent BiPAP use over weeks

Teaching point: OHS is NOT just "severe OSA." It's a distinct entity with daytime hypercapnia requiring BiPAP with backup rate (not just CPAP). Untreated OHS has 18% mortality at 18 months vs 3% with treatment. Weight loss is curative.