Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is suggested by a normal FEV1/FVC ratio and a reduced FEV1%?

1. Obstructive lung disease

2. Restrictive lung disease

3. Normal lung function

4. Mixed lung disease

The correct answer is: Restrictive lung disease

A normal FEV1/FVC ratio combined with a reduced FEV1% indicates a pattern consistent with restrictive lung disease. In restrictive lung conditions, the total volume of air that the lungs can hold is decreased, which influences the forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC). In restrictive lung disease, both FEV1 and FVC can be reduced, but the ratio typically remains normal or may even be slightly increased because FEV1 and FVC decrease proportionally. This contrasts with obstructive lung disease, where the FEV1 is significantly decreased relative to FVC, leading to a low FEV1/FVC ratio. The context here highlights that while a reduced FEV1% signifies that the patient may not be able to take in as much air, it does not suggest a primary obstruction in airflow as seen in obstructive lung disease. Instead, it shows that overall lung volumes are restricted, a hallmark of conditions such as pulmonary fibrosis or pleural diseases. Therefore, the combination of a normal FEV1/FVC ratio with a reduced FEV1% strongly points to the presence of restrictive lung disease.