What is the typical DLCO result in chronic bronchitis?

• A. Reduced
• B. Normal
• C. Increased
• D. Variable

Answer: (B)

In chronic bronchitis, the typical DLCO (Diffusing Capacity of the Lungs for Carbon Monoxide) result is generally normal. This is due to the primary pathophysiological changes associated with chronic bronchitis, which primarily affect the airways rather than the alveolar-capillary membrane where gas exchange occurs.

In chronic bronchitis, inflammation and mucus production lead to narrowing of the airways and obstruction, but the alveoli usually remain intact and functional for gas exchange, allowing for the preservation of the DLCO. Therefore, although individuals may experience significant airflow limitations and hypoxemia, the ability of lungs to transfer carbon monoxide (a surrogate marker for oxygen diffusion capacity) typically remains unaltered.

This contrasts with other pulmonary conditions such as emphysema, where destruction of alveolar walls leads to a markedly reduced DLCO, reflecting impaired gas exchange capability. Hence, a normal DLCO result in chronic bronchitis is consistent with the pathophysiology of the disease, further emphasizing the distinct mechanisms by which different pulmonary disorders impact lung function tests.