The diffusing capacity of the lungs for CO (DLCO) is reduced in which of the following conditions?

• A Pulmonary fibrosis ✓
• B Polycythemia vera
• C Asthma during an asymptomatic period
• D Left-to-right cardiac shunt

Explanation

DLCO measures the ability of the lungs to transfer gas across the alveolar-capillary membrane. It is reduced in conditions that destroy alveolar surface area or thicken the alveolar-capillary membrane, such as pulmonary fibrosis, emphysema, and pulmonary vascular disease. Polycythemia increases hemoglobin available to bind CO, thus increasing DLCO. Asthma with normal interstitium and cardiac shunts do not impair diffusion capacity.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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