329.3 🏥 內科專科考前版

329.3.1 Mechanistic Deep Dive

329.3.1.1 Hypoxic Pulmonary Vasoconstriction

  • Adaptive response to alveolar hypoxia
  • Redirects blood from poorly ventilated areas
  • Pathological at high altitude (entire lung hypoxic)
  • Heterogeneous → stress failure

329.3.1.2 Boyle’s Law in Diving

  • Pressure × Volume = constant
  • Ascent → expansion of gas
  • Rapid ascent → barotrauma
  • N2 dissolved in tissues comes out of solution

329.3.1.3 CO Pathophysiology

  • 200x higher affinity for hemoglobin than O2
  • Carboxyhemoglobin → no oxygen carrying
  • Also cytotoxic at cellular level (mitochondria)
  • Half-life: 4-5 hr air, 1-1.5 hr 100% O2, 23 min hyperbaric

329.3.2 Recent Trials & Updates

329.3.2.1 Acetazolamide for AMS

  • Multiple studies confirm prophylaxis benefit
  • 125-250 mg BID
  • ~ 50% reduction in AMS

329.3.2.2 Nifedipine vs Sildenafil for HAPE

  • Both effective for prevention + treatment
  • Mixed comparative data
  • Nifedipine more established

329.3.2.3 Hyperbaric Oxygen Indications (2024)

  • Decompression sickness
  • Arterial gas embolism
  • CO poisoning (severe)
  • Cyanide poisoning (adjunct)
  • Necrotizing fasciitis
  • Diabetic ulcers
  • Radiation injury

329.3.3 High-Yield Specialist Points

329.3.3.1 Sleep at Altitude

  • Periodic breathing (Cheyne-Stokes)
  • Acetazolamide helps
  • Less REM sleep
  • Worsens at sleep

329.3.3.2 Children at High Altitude

  • More susceptible
  • Less able to recognize symptoms
  • Gradual ascent + monitoring critical

329.3.3.3 Pregnancy + High Altitude

  • Avoid > 2500m if possible
  • Acetazolamide pregnancy category C
  • Conservative approach

329.3.3.4 Chronic Mountain Sickness (CMS) / Monge Disease

  • Long-term high altitude resident
  • Polycythemia, pulmonary HTN
  • Treatment: descend to lower altitude, phlebotomy

329.3.3.5 Patent Foramen Ovale + DCS

  • Paradoxical embolism through PFO
  • 2-3x DCS risk
  • Closure considered for select divers

329.3.3.6 HBOT Side Effects

  • Barotrauma (ear, sinus)
  • O2 toxicity (seizures)
  • Claustrophobia
  • Pulmonary fibrosis (long-term)

329.3.3.7 Inhalation Injury Severity Grading

  • Bronchoscopy + visualization
  • Grade I-IV
  • Predicts outcomes

329.3.3.8 Indoor Air Quality + Lung Disease

  • Cooking fumes
  • Secondhand smoke
  • Mold
  • Volatile organic compounds
  • Particulate matter

329.3.3.9 Wildfire Smoke Exposure

  • Increasing climate change
  • ↑ Respiratory exacerbations
  • N95 masks for protection
  • Air filtration
  • Stay indoors during high AQI

329.3.3.10 Vapes / E-Cigarettes + EVALI (Ch306)

  • Vitamin E acetate
  • Lipoid pneumonia
  • Acute respiratory failure
  • Steroid + cessation

329.3.4 Pearls

  • AMS: HA + GI > 2500m; acetazolamide
  • HAPE: rapid dyspnea + frothy sputum; descend + nifedipine
  • HACE: ataxia + altered MS; descend + dexamethasone
  • DCS: post-dive joint/neuro; 100% O2 + HBOT
  • AGE: post-dive stroke-like; Trendelenburg + HBOT
  • CO poisoning: 100% O2; HBOT for severe (CO-Hb > 25%, neuro, pregnancy)
  • Cyanide: hydroxocobalamin (Cyanokit)
  • Phosgene: delayed pulmonary edema 6-24 hr
  • NO2 (silo filler): delayed bronchiolitis obliterans
  • Near-drowning: lung-protective ventilation; no routine antibiotics