What does a decrease in FEV1 suggest in a pulmonary function test?

A decrease in FEV1 (Forced Expiratory Volume in one second) is indicative of obstructive lung disease. In obstructive lung disease, the main problem is that airflow is impeded during expiration due to conditions such as asthma, chronic obstructive pulmonary disease (COPD), and bronchitis.

When patients with these conditions perform a pulmonary function test, the FEV1 measurement tends to be significantly lower than normal because they struggle to get air out of their lungs quickly. This decrease points to a reduction in the ability to expel air, which characterizes the obstructive patterns seen on a spirometry graph.

In contrast, normal lung function would demonstrate FEV1 values within the expected range, while restrictive lung diseases are more associated with a reduction in overall lung volumes (including FEV1, but also FVC - Forced Vital Capacity), leading to different interpretations of the PFT results. Vascular lung disease does not typically affect FEV1 readings directly, as it primarily involves issues related to blood supply in the lungs rather than airway obstruction. Thus, a reduced FEV1 strongly suggests the presence of obstructive lung disease.