A respiratory therapist has just performed a pulmonary function study and notes that the results show obstructive lung disease with a decreased DLCO value. Which of the following is the best interpretation of these results?

a. The patient has pulmonary fibrosis.
b. The patient has asthma.
c. The patient has cystic fibrosis.
d. The patient has emphysema.
e. The patient has chronic bronchitis.

D
A decreased DLCO is a hallmark clinical manifestation in emphysema because of the destruction of the alveolar pulmonary capillaries and decreased surface area for gas diffusion associated with the disease. The DLCO is usually normal in all other obstructive lung disorders. Pulmonary fibrosis is a restrictive disease, not an obstructive disease.