Which measurement reflects the severity of an obstructive lung disease?

The measurement that reflects the severity of an obstructive lung disease is Forced Expiratory Volume in 1 second (FEV1). In obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), patients experience difficulty exhaling air from the lungs due to narrowed airways, which leads to a reduction in FEV1.

FEV1 is a critical parameter because it quantifies the volume of air that can be forcefully exhaled in the first second of a breath. A lower FEV1 indicates greater airway obstruction and, consequently, more severe impairment of lung function. This makes it a valuable measure for diagnosing the severity of obstructive conditions. Additionally, the FEV1/FVC ratio is commonly used; a significant reduction in this ratio further confirms the presence of an obstructive pattern.

While the other measurements mentioned also provide important information about lung function, they do not specifically reflect the severity of obstructive lung disease as directly as FEV1. For instance, Forced Vital Capacity (FVC) is a measure of the total volume of air that can be exhaled forcefully after taking a deep breath, but it does not differentiate between obstructive and restrictive patterns. Peak Expiratory Flow Rate