Diffusion capacity for carbon monoxide is decreased in all of the following Except:

Answer is A (Chronic Bronchitis): Diffusion capacity for carbon monoxide (DLCO) is usually normal in chronic bronchitis and other obstructive lung diseases with the exception of Emphysema where it is decreased. Diffusion capacity for carbon monoxie (DLCO) Diffusion capacity is altered in disease affecting the functional integrity of the alveolar capillary membrane. In Emphysema, alveolar walls are destroyed, so the surface area of alveolar-capillary bed is diminished resulting in diminished DL CO. Three main categories are associated with lowered DLCO Emphysema Q Interstitial Lung Disease Q Pulmonary vascular disease (Recurrent Pulmonary emboli or Primary Pulmonary Hypeension)Q