What parameter is commonly used to assess the severity of an obstructive lung disease?

The parameter commonly used to assess the severity of an obstructive lung disease is the FEV1 percentage of predicted. FEV1, or Forced Expiratory Volume in one second, is a key component of pulmonary function testing and reflects the amount of air a person can forcibly exhale in one second after taking a deep breath.

In obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), the airflow is reduced, primarily due to narrowing of the airways. A significant decline in the FEV1 indicates that there is a substantial obstruction present. The FEV1 is typically compared to a predicted value based on factors such as age, gender, height, and ethnicity to determine the severity of the obstruction.

When FEV1 is expressed as a percentage of the predicted value, it allows for the classification of the severity of the obstruction into mild, moderate, severe, or very severe categories according to established guidelines. This makes it a crucial tool for clinicians in both diagnosing and managing obstructive lung diseases, as well as monitoring disease progression over time.

The other options, while relevant to overall lung function, do not specifically or reliably indicate the severity of obstructive disease. FVC percentage of predicted assesses overall lung