Biomedical Sciencemiddle twist
A 54-year-old woman has progressive exertional dyspnoea. Spirometry shows a forced expiratory volume in one second of 2.4 L (reference greater than 2.0 L) and a normal FEV1/FVC ratio. Total lung capacity is normal, but diffusion capacity for carbon monoxide is 55% of predicted. Haemoglobin is 82 g/L (reference 120–160 g/L), and high-resolution computed tomography shows no interstitial lung disease. Which change most directly accounts for the reduced measured diffusion capacity?