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Oxygen-induced hypercapnia peri-arrest — SCE Acute Medicine MCQ

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HardCritical Care MedicineOxygen-induced hypercapnia peri-arrestSCE Acute Medicine

A 69-year-old woman with known severe COPD is admitted with infective exacerbation. After two hours on high-concentration oxygen she becomes somnolent. ABG shows pH 7.18, PaCO2 12.1 kPa, PaO2 20.2 kPa and bicarbonate 34 mmol/L. She has a documented plan for full escalation. What is the most appropriate next step in management?

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Correct answer: D — Controlled oxygen, acute NIV and urgent critical care review

The patient has severe oxygen-induced acute-on-chronic hypercapnic respiratory failure, requiring oxygen titration and ventilatory support with NIV. Bicarbonate does not remove CO2 and may worsen intracellular acidosis. CPAP does not provide the ventilatory assistance needed for hypercapnia. The pearl is that a high PaO2 in COPD may be a warning sign when the pH and CO2 are deteriorating.

Reference: BTS/ICS Guideline for acute hypercapnic respiratory failure