What is a key finding in pulmonary function tests for obstructive disorders?

• A. FEV1/FVC ratio greater than 70%
• B. FEV1 is equal to the predicted value
• C. FVC is often normal
• D. FEV1/FVC ratio less than 70%

Answer: (D)

In patients with obstructive pulmonary disorders, a key finding in pulmonary function tests is a reduced FEV1/FVC ratio, specifically a ratio less than 70%. This indicates that the reduction in forced expiratory volume in one second (FEV1) is disproportionately greater than the reduction in forced vital capacity (FVC). The FEV1 measures how much air a person can forcibly exhale in one second, and FVC measures the total amount of air exhaled after taking a deep breath.

In obstructive disorders, such as asthma and chronic obstructive pulmonary disease (COPD), there is an obstruction that hinders airflow during expiration. This leads to a significant decrease in FEV1 due to the narrowed airways, but the FVC is often less affected, particularly in the early stages of disease. Therefore, when calculating the FEV1/FVC ratio, a value less than 70% reflects that expiratory airflow is compromised, confirming the presence of an obstructive lung condition.

In contrast, a ratio greater than 70% would suggest normal or restrictive lung function, a situation where both FEV1 and FVC may be reduced but maintain a more proportional relationship. Having FEV1 equal to the predicted value