Which pulmonary function test (PFT) finding is characteristic of obstructive lung disease?

Which pulmonary function test (PFT) finding is characteristic of obstructive lung disease?

• A. FEV1/FVC ratio greater than 70%
• B. FEV1/FVC ratio less than 70%
• C. FVC greater than the predicted value
• D. Normal TLC values

Answer: (B)

The characteristic finding of obstructive lung disease in pulmonary function tests is a reduced FEV1/FVC ratio, specifically less than 70%. This occurs because obstructive diseases, such as asthma and chronic obstructive pulmonary disease (COPD), primarily affect airflow, making it difficult for patients to exhale all of the air in their lungs. In obstructive lung disease, the FEV1 (forced expiratory volume in one second) is significantly reduced due to narrowed airways, while the FVC (forced vital capacity) may remain normal or be reduced to a lesser extent. The resulting low ratio of FEV1 to FVC indicates a predominance of airflow limitation, which is a hallmark of these conditions. Therefore, recognizing this key feature helps distinguish obstructive lung diseases from other types of respiratory conditions, thereby guiding diagnosis and management.

The characteristic finding of obstructive lung disease in pulmonary function tests is a reduced FEV1/FVC ratio, specifically less than 70%. This occurs because obstructive diseases, such as asthma and chronic obstructive pulmonary disease (COPD), primarily affect airflow, making it difficult for patients to exhale all of the air in their lungs.

In obstructive lung disease, the FEV1 (forced expiratory volume in one second) is significantly reduced due to narrowed airways, while the FVC (forced vital capacity) may remain normal or be reduced to a lesser extent. The resulting low ratio of FEV1 to FVC indicates a predominance of airflow limitation, which is a hallmark of these conditions. Therefore, recognizing this key feature helps distinguish obstructive lung diseases from other types of respiratory conditions, thereby guiding diagnosis and management.