In pulmonary function testing, what does an FVC of less than 80% suggest?

An FVC (Forced Vital Capacity) of less than 80% indicates a reduction in the total volume of air that can be forcefully exhaled after taking a deep breath. This finding suggests a restrictive pattern of lung disease. In restrictive lung diseases, the lungs are unable to expand fully, leading to a decreased lung volume and consequently a lower FVC. Conditions such as pulmonary fibrosis, chest wall abnormalities, and pleural diseases can cause this restricted ability to inflate the lungs.

In contrast, obstructive lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD), typically present with normal or increased total lung capacity but a reduced FEV1/FVC ratio, where the FEV1 is significantly lowered while FVC may remain normal or only slightly reduced. Normal lung function would be indicated by FVC values of 80% or higher. Exercise limitation could be attributable to various factors but is not specifically inferred through the FVC measurement alone. Thus, the significant drop in FVC below 80% is a hallmark indicator of a restrictive lung pathology.