💡HYPOXIA: LOW O₂, MANY CAUSES! Hypoxia is a sign, not a diagnosis. Understanding the mechanism helps you identify the cause and treat it quickly. ⸻ 1️⃣ V/Q Mismatch 📍 Most common cause of hypoxia 🔹 Ventilation and perfusion are mismatched 🔹 Seen in asthma, COPD, pneumonia 💎 Pearl: Improves with supplemental oxygen. ⸻ 2️⃣ Shunt 📍 Blood bypasses ventilated alveoli 🔹 No gas exchange occurs 🔹 Seen in ARDS, severe pneumonia, atelectasis 💎 Pearl: Does NOT significantly improve with oxygen. ⸻ 3️⃣ Diffusion Defect 📍 Impaired gas transfer across alveolar membrane 🔹 Pulmonary fibrosis 🔹 Interstitial lung disease 💎 Pearl: Worse during exercise. ⸻ 4️⃣ Hypoventilation 📍 Reduced alveolar ventilation 🔹 CNS depression 🔹 Neuromuscular disorders 🔹 Obesity hypoventilation 💎 Pearl: ↑ PaCO₂ + ↓ PaO₂ ⸻ 5️⃣ Low FiO₂ 📍 Reduced inspired oxygen 🔹 High altitude 🔹 Poorly ventilated environments 💎 Pearl: Improves with increased FiO₂. ⸻ 6️⃣ Pulmonary Embolism (PE) 📍 Perfusion defect 🔹 Sudden dyspnea 🔹 Pleuritic chest pain 🔹 Tachycardia 💎 Pearl: Ventilation present, perfusion absent. ⸻ 7️⃣ ARDS 📍 Diffuse alveolar injury 🔹 Severe hypoxemia 🔹 Pulmonary edema 🔹 Reduced lung compliance 💎 Pearl: Refractory hypoxemia despite oxygen therapy. ⸻ 💎 High-Yield Exam Pearls 🫁 V/Q Mismatch → Most common 🫁 Shunt → Doesn’t improve with O₂ 🫁 Diffusion Defect → Worse on exertion 🫁 Hypoventilation → High CO₂ 🫁 Low FiO₂ → High altitude 🫁 PE → Ventilation without perfusion 🫁 ARDS → Refractory hypoxemia ⸻ 📚aumedprep.com.au
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