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Emphysema physiology — SCE Respiratory MCQ

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HardRespiratory PhysiologyEmphysema physiologySCE Respiratory

A smoker has obstruction, TLC 118% predicted, KCO 48% predicted and TLCO 35% predicted; haemoglobin is normal. Which structural change best accounts for this combination?

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Correct answer: A — Loss of alveolar-capillary surface area from emphysema

Explanation lettering: C = shown as B · B = shown as C

A is correct. Hyperinflation with markedly reduced TLCO and KCO indicates loss of effective alveolar-capillary surface area, typical of emphysema. Pure asthma generally preserves or raises transfer. Obesity reduces ERV and often preserves KCO. Pleural disease causes restriction rather than hyperinflation, while laryngeal obstruction alters flow-loop morphology and does not destroy the gas-exchange surface. Normal haemoglobin removes anaemia as the explanation.

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