What is indicated by a lower FEV1 value in a pulmonary function test?

A lower FEV1 value in a pulmonary function test primarily indicates a possible obstructive lung disease, as it reflects the volume of air that can be forcibly exhaled in one second. In obstructive conditions, such as asthma or chronic obstructive pulmonary disease (COPD), there is a narrowing or obstruction of the airways, which makes it difficult for air to flow out quickly. As a result, individuals with obstructive lung diseases typically exhibit a decreased FEV1, often in conjunction with a reduced FEV1/FVC (Forced Vital Capacity) ratio.

In contrast, a normal FEV1 would suggest that lung function is within expected ranges, while a lower FEV1 could also signify restrictive lung conditions, but typically the primary indicator is the FEV1/FVC ratio in such cases. Excessive lung compliance generally relates to conditions like emphysema, which may be present alongside obstructive diseases, but it does not directly correlate to just a low FEV1. Thus, the interpretation of a lower FEV1 value is most accurately associated with obstructive lung diseases.