What are some common causes of low DLCO?

Low diffusion capacity of the lungs for carbon monoxide (DLCO) can indicate several pulmonary conditions, particularly those that affect the alveolar-capillary membrane or overall lung volume and function. Emphysema, a specific form of chronic obstructive pulmonary disease (COPD), is characterized by the destruction of alveoli, which significantly reduces the surface area available for gas exchange. This destruction leads to lower DLCO values because the impaired alveolar structure hinders the diffusion process.

In the case of emphysema, the destruction of alveolar walls results in a loss of elastic recoil and increased airflow obstruction, which directly impacts the ability of the lungs to transfer carbon monoxide. As a result, patients with emphysema typically showcase a reduced DLCO, making this option the most relevant cause among the choices provided.

While other conditions like asthma, chronic bronchitis, and pneumothorax can certainly affect lung function, they usually do not lead to a low DLCO in the same way that emphysema does. Asthma primarily involves reversible airway obstruction without significant destruction of the alveolar structures, chronic bronchitis is characterized by airway inflammation and does not typically cause a reduced DLCO unless there is severe associated emphysema, and pneumothorax may