What is a characteristic of obstructive lung disease?

Obstructive lung disease is characterized by a reduced ability to expel air from the lungs, leading to an abnormal decrease in airflow. The FEV1 (forced expiratory volume in one second) reflects this airflow limitation, while the FVC (forced vital capacity) measures the total volume of air a patient can forcibly exhale after taking a deep breath.

In obstructive lung disease, the FEV1 decreases more significantly than the FVC, resulting in a low FEV1/FVC ratio, typically less than 70%. This finding indicates that the patient is unable to effectively expel air from their lungs, which is a hallmark of conditions such as asthma, chronic obstructive pulmonary disease (COPD), and bronchiectasis.

The other options do not align with the characteristics of obstructive lung disease: a FEV1/FVC ratio greater than 70% suggests normal lung function or restrictive lung disease, a FEV1 greater than 80% predicted indicates no significant obstruction, and normal lung volumes are also not indicative of obstructive disease, as these patients commonly present with hyperinflation. Therefore, a FEV1/FVC ratio less than 70% is the defining characteristic of obstructive lung disease.