American Board of Family Medicine (ABFM) Practice Exam 2026 - Free ABFM Practice Questions and Study Guide

Restrictive pulmonary conditions are typically characterized by a reduced ability of the lungs to expand fully, leading to lower lung volumes. One key aspect of these conditions is that they often result in a low diffusing capacity of the lung for carbon monoxide. This occurs because the structural abnormalities or inflammation associated with restrictive diseases can impair the surface area available for gas exchange or affect the functionality of the alveolar-capillary membrane.

In conditions such as pulmonary fibrosis or asbestosis, the thickening or scarring of lung tissues reduces the efficiency of gas exchange, leading to a decrease in diffusing capacity. As a result, when assessing patients with restrictive disease through pulmonary function tests, you would expect to see a low value in diffusing capacity measurements.

Other choices provided do not align with the characteristics of restrictive pulmonary conditions. For example, high diffusing capacity is typically associated with healthy lung function and is not a characteristic of restrictive pathology. Similarly, normal pulmonary function tests would not be expected in restrictive conditions, as these tests often show reduced lung volumes. Lastly, increased airway resistance is more commonly associated with obstructive lung diseases rather than restrictive conditions, where airflow limitation is due to factors affecting lung expansion rather than airway obstruction.