What effect does obesity have on pulmonary function test results?

Obesity has a significant impact on pulmonary function tests, primarily contributing to a restrictive pattern characterized by decreased lung volumes. This occurs because excess body weight can restrict the diaphragm and thoracic cage movement, limiting lung expansion. As a result, patients with obesity often present with reduced inspiratory capacity, total lung capacity, and forced vital capacity on pulmonary function tests.

The restrictive pattern arises because the limitation in lung expansion leads to a reduced amount of air that can be inhaled, rather than affecting the airflow limitation typically seen in obstructive lung diseases. Therefore, decreased lung volumes are expected findings in individuals with obesity during pulmonary function testing.

In contrast, options suggesting increased lung volumes or typical normal results do not accurately reflect the physiological limitations imposed by obesity on lung function. Furthermore, while obesity may influence airway resistance to some degree, the most pronounced effect is the reduction in lung volumes, hence the restrictive spirometric pattern is the key aspect associated with obesity in pulmonary function tests.