ICU · Respiratory

Acute respiratory failure: type 1 vs type 2, oxygen therapy, and when to intubate

Also known as Respiratory failure · Type 1 respiratory failure · Type 2 respiratory failure · Hypoxaemic respiratory failure · Hypercapnic respiratory failure · A-a gradient

Acute respiratory failure = inability of respiratory system to maintain adequate GAS EXCHANGE (oxygenation [O2 in] and/or ventilation [CO2 out]). TWO TYPES: TYPE 1 (HYPOXAEMIC) — PaO2 <60 mmHg (8 kPa) with NORMAL/LOW PaCO2 — from V/Q mismatch, shunt, diffusion impairment — causes: pneumonia, ARDS, PE, pulmonary oedema, asthma. TYPE 2 (HYPERCAPNIC) — PaCO2 45 mmHg (6 kPa) ± hypoxaemia — from ALVEOLAR HYPOVENTILATION (not enough air moved) — causes: COPD, neuromuscular (GBS, MG), opioid overdose, obesity hypoventilation, chest wall deformity. A-a GRADIENT (alveolar-arterial): helps distinguish — ELEVATED (20) = lung problem (V/Q mismatch/shunt); NORMAL (<15) = pure hypoventilation (normal lungs — just not breathing enough). MANAGEMENT: TYPE 1 → oxygen (high concentration) + treat cause + NIV/CPAP/HFNC if moderate + intubate if severe. TYPE 2 → NIV (BiPAP — ventilatory support) + oxygen (controlled — target SpO2 88-92% for CO2 retainers) + treat cause + intubate if NIV fails.