314.3 🏥 內科專科考前版

314.3.1 Mechanistic Deep Dive

314.3.1.1 Pharyngeal Anatomy + Collapse

  • Pharyngeal muscles (genioglossus, palatoglossus) maintain patency
  • Decreased tone in sleep
  • REM sleep further reduces tone
  • Anatomic crowding + obesity reduces space
  • Negative inspiratory pressure → collapse

314.3.1.2 CPAP Mechanism

  • Pneumatic splint
  • Prevents collapse
  • Improves V/Q
  • Reduces sympathetic drive

314.3.1.3 Cheyne-Stokes Pathophysiology

  • Prolonged circulation time (HF)
  • Hypocapnic-eucapnic-hypercapnic cycling
  • CO2 chemoreceptor instability
  • Worsens HF further (vicious cycle)

314.3.1.4 Tirzepatide Mechanism in OSA

  • GIP + GLP-1 dual agonist
  • Weight loss ~ 20%
  • Anti-inflammatory + metabolic
  • Reduces airway adipose tissue
  • Improves ventilatory drive

314.3.2 Recent Trials & Updates

314.3.2.1 SURMOUNT-OSA (2024) — Tirzepatide

  • N = 469 OSA + obesity (BMI ≥ 30)
  • Tirzepatide vs placebo
  • AHI reduced ~ 50% (mean decline)
  • Weight loss substantial
  • FDA approval pending 2024-2025
  • Practice-changing for obese OSA

314.3.2.2 STAR (2014) — Inspire HGNS

  • Moderate-severe OSA + CPAP-intolerant
  • AHI reduced 68%
  • FDA approval
  • 5-year sustained efficacy

314.3.2.3 SAVE (2016) — CPAP in OSA + CVD

  • N = 2717
  • No CV outcome benefit
  • Adherence issues
  • Subgroup compliant users improved

314.3.2.4 SERVE-HF (2015) — ASV in HFrEF + CSR

  • ↑ Mortality 28%
  • ASV no longer recommended for HFrEF + predominant CSR
  • Caution generalized

314.3.2.5 MERIDIAN-2 (2024) — Hypoxia-Targeted Therapy

  • Combination atomoxetine + oxybutynin for OSA
  • Reduces AHI
  • Norepinephrine + anticholinergic (tongue muscle activation)

314.3.2.6 LANCE-OSA Trial

  • Solriamfetol for residual sleepiness post-CPAP

314.3.3 High-Yield Specialist Points

314.3.3.1 Drug-Induced Sleep Endoscopy (DISE)

  • Inducing sleep + bronchoscopy
  • Identifies site of collapse (palate, oropharynx, hypopharynx, larynx)
  • Guides surgical + HGNS patient selection

314.3.3.2 OSA Phenotypes

  • Anatomic: high collapsibility
  • Loop gain: ventilatory instability
  • Arousal threshold: easily aroused
  • Muscle responsiveness: poor pharyngeal dilator response
  • 4 endotypes + targeted therapy emerging

314.3.3.3 Resistant Hypertension + OSA

  • High prevalence
  • ABPM + screening for OSA
  • CPAP for resistant HTN
  • Modest BP reduction (2-3 mmHg)
  • Adjunct to BP medications

314.3.3.4 AF + OSA

  • Strong association
  • 50%+ AF patients have OSA
  • Untreated OSA → 50%+ ablation recurrence
  • Screen + treat OSA before AF ablation

314.3.3.5 Obesity Hypoventilation Syndrome (OHS)

  • Already covered (Ch312)
  • Often OSA + OHS overlap
  • BiPAP more often needed than CPAP

314.3.3.6 Driving + OSA

  • Untreated OSA → 2-3x MVA risk
  • Reporting laws variable
  • Counsel patients
  • Treatment improves driving safety

314.3.3.7 Anesthesia + OSA

  • Higher complication risk
  • STOP-BANG pre-op
  • Regional anesthesia preferred
  • CPAP perioperatively
  • Avoid opioids

314.3.3.8 Pediatric OSA Treatment

  • Adenotonsillectomy first-line (75% cure)
  • CPAP if persistent + adolescent
  • Weight loss if obese
  • Orthodontic treatment for craniofacial abnormalities

314.3.3.9 Insomnia + OSA Overlap

  • Common
  • COMISA (comorbid insomnia + OSA)
  • CBT-I + CPAP combination

314.3.3.10 Periodic Limb Movement Disorder

  • Often coexisting
  • Dopamine agonist treatment
  • Iron supplementation if deficient

314.3.4 Pearls

  • AHI ≥ 15 OR AHI ≥ 5 + symptoms = OSA
  • CPAP is gold standard
  • HGNS (Inspire) for moderate-severe + CPAP-intolerant + BMI < 32
  • SURMOUNT-OSA 2024: tirzepatide reduces AHI 50%+ in obese — game-changer
  • SERVE-HF: ASV NOT for HFrEF + CSR (↑ mortality)
  • SAVE: CPAP in OSA + CVD = neutral; adherence matters
  • OSA + AF: treat OSA before ablation
  • DISE: site of collapse for surgical / HGNS selection