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Restrictive lung function defect — SCE Respiratory MCQ

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HardRespiratory PhysiologyRestrictive lung function defectSCE Respiratory

A patient has TLC 66% predicted, TLCO 39% predicted and KCO 61% predicted with basal crackles. Which physiological interpretation is best?

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

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Correct answer: E — Parenchymal restriction with impaired gas transfer, consistent with ILD

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

A is correct. Confirmed restriction plus reduced TLCO and reduced KCO supports intrinsic parenchymal loss or thickening, consistent with ILD in this clinical setting. Extrapulmonary restriction often has preserved or raised KCO. Reduced TLCO is not synonymous with emphysema, and preserved FEV1/FVC is expected in restriction. Pulmonary vascular disease may lower TLCO disproportionately but does not usually explain a clearly reduced TLC with crackles.

Reference: ERS/ATS interpretive strategies for lung-function tests: https://publications.ersnet.org/content/erj/60/1/2101499