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Oxygen-induced hypercapnia — SCE Respiratory MCQ

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HardCOPDOxygen-induced hypercapniaSCE Respiratory

A 69-year-old man with COPD is admitted with pneumonia. He is alert, respiratory rate 24/min and SpO2 95% on 10 L/min oxygen. ABG shows pH 7.33, PaCO2 7.2 kPa, PaO2 18.6 kPa and HCO3 30 mmol/L. What is the most appropriate management?

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Correct answer: A — Reduce oxygen to a controlled 88-92% target and repeat ABG

This COPD patient has hyperoxaemia with hypercapnia, so oxygen should be titrated to 88-92% with repeat ABG to assess acidosis. Increasing oxygen may worsen CO2 retention through V/Q effects and the Haldane effect. The vignette does not support PE thrombolysis or pulmonary oedema as the immediate issue.

Reference: BTS Guideline for Oxygen Use in Adults 2017; NICE NG115