Certified Pulmonary Function Technologist (CPFT) Practice Exam

A decreased DLCO usually indicates which type of disease process?

1. Obstructive disease

2. Restrictive disease process

3. Vascular disease

4. Infectious disease

The correct answer is: Restrictive disease process

A decreased DLCO, or diffusing capacity of the lungs for carbon monoxide, typically indicates a restrictive disease process. This decrease is primarily associated with conditions that result in a reduction of the lung's ability to transfer gas from the alveoli to the bloodstream. Restrictive lung diseases, such as interstitial lung disease or pulmonary fibrosis, involve structural changes in the lung tissue, which impair gas exchange and lead to lower DLCO values. These conditions often cause stiffening of the lung parenchyma, reducing compliance and leading to less efficient gas transfer. In contrast, obstructive diseases like asthma or COPD may demonstrate a normal or increased DLCO initially, as the primary issue in these cases is airflow limitation rather than a direct impairment of the alveolar-capillary membrane. Vascular diseases may also affect DLCO, but more specifically, they would indicate conditions affecting blood flow rather than the lung volume itself. Infectious diseases might alter DLCO as well, but often depend on the extent and nature of the pulmonary involvement. Therefore, the connection between a decreased DLCO and restrictive lung disease underscores the importance of understanding how these various disease processes impact pulmonary function testing.