In the context of obstructive lung disease, what is the FEV1 usually less than?

In obstructive lung disease, the FEV1 (Forced Expiratory Volume in one second) is typically less than 80% of the predicted value. This measurement is crucial for assessing the severity of obstruction in the airways. When the FEV1 falls below this threshold, it indicates significant airway limitation, commonly seen in conditions such as asthma and chronic obstructive pulmonary disease (COPD).

A FEV1 value of 80% or less suggests that there is notable difficulty in expelling air from the lungs, which is characteristic of obstructive pathology. This reduction in airflow can be due to various factors, including inflammation, bronchoconstriction, or structural changes in the airways.

The relationship between FEV1 and the severity of lung disease is an essential part of respiratory therapy and helps guide treatment decisions, including the use of bronchodilators and corticosteroids. Understanding the FEV1 value in the context of lung function testing aids clinicians in diagnosing and managing obstructive lung diseases effectively.