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Oxygen-induced hypercapnia — SCE Respiratory MCQ

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HardCOPDOxygen-induced hypercapniaSCE Respiratory

An adult with suspected asthma has pre-bronchodilator FEV1 2.05 L and post-bronchodilator FEV1 2.30 L; predicted normal FEV1 is 2.42 L. FeNO and eosinophils were non-diagnostic. Which interpretation follows BTS/NICE/SIGN criteria?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — The response supports asthma by meeting both 12% plus 200 mL and 10% of predicted criteria

Explanation lettering: D = shown as B · E = shown as D · B = shown as E

D is correct. FEV1 rises by 0.25 L, which is 12.2% of baseline and 10.3% of predicted normal. BTS/NICE/SIGN diagnoses asthma when FEV1 increases by at least 12% and 200 mL from baseline, or by at least 10% of predicted normal; this response satisfies both formulations. A 400-mL threshold is not required, incomplete normalisation does not convert the result into COPD, FVC need not change in parallel, and objective results still sit within the compatible episodic clinical history.

Reference: https://www.nice.org.uk/guidance/ng245/chapter/recommendations