American Board of Surgery Qualifying Exam (ABS QE) Practice Test

Which parameter is decreased in both obstructive and restrictive lung diseases?

1. FEV1

2. FVC

3. RV

4. TLC

The correct answer is: FVC

In both obstructive and restrictive lung diseases, one key parameter that can be decreased is the forced vital capacity (FVC). This measure indicates the total amount of air that can be exhaled after taking a deep breath. While the primary characteristic of obstructive lung diseases is a decrease in airflow, as reflected in a reduced FEV1 (forced expiratory volume in 1 second) and a relatively preserved FVC, in restrictive lung diseases, the FVC is decreased due to reduced lung volumes and compliance. In obstructive diseases, patients often have a difficulty in exhaling air due to airway obstruction but may still have a preserved or even increased total lung capacity (TLC). In restrictive diseases, the lung volumes are inherently decreased, thus affecting FVC directly. In both types of diseases, if FVC is significantly reduced, it emphasizes the reduced ability to expel air from the lungs, crucially noting that this parameter is affected across both categories of lung pathology. The other parameters are typically not decreased in the same way across both obstructive and restrictive diseases. FEV1 generally is lower in obstructive lung disease, reflecting airflow limitation, while it can be less affected in restrictive diseases. Residual volume (RV) may actually be normal