A patient with obstructive lung disease would likely have which of the following tests results?

In a patient with obstructive lung disease, the characteristic pulmonary function test results show that the ratio of forced expiratory volume in the first second (FEV1) to forced vital capacity (FVC) is reduced, typically less than 70%. This reduction occurs because the FEV1 decreases more significantly than the FVC due to narrowed airways, which leads to difficulty in exhaling air from the lungs.

In obstructive lung diseases, such as chronic obstructive pulmonary disease (COPD) or asthma, the maximum airflow during expiration is compromised. Therefore, while total lung capacity and often FVC may remain normal or may even be increased, the FEV1 is noticeably decreased, causing the FEV1/FVC ratio to drop below the normal threshold of 70%.

Recognizing this hallmark of obstructive lung disease is crucial for diagnosis and management, as it guides clinicians in determining the presence and severity of the obstruction.