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

What is a hallmark finding in obstructive lung disease?

1. Decreased TLC and RV

2. Increased TLC and RV

3. Normal FVC with decreased RV

4. Decreased FEV1 with normal FVC

The correct answer is: Increased TLC and RV

In obstructive lung disease, the hallmark finding is indeed the increase in total lung capacity (TLC) and residual volume (RV). This occurs as the airways become obstructed, typically due to conditions such as chronic obstructive pulmonary disease (COPD) or asthma, leading to difficulty in expiration. As the airways narrow, patients often experience a trapping of air in the lungs, which causes the lungs to remain overinflated. As a result, TLC increases because of the additional volume that remains in the lungs after an exhalation. Similarly, RV, the volume of air that remains in the lungs after a maximum exhalation, also increases. In contrast, conditions such as restrictive lung disease would lead to decreased TLC and RV, thus ruling out the first choice. The normal FVC with decreased RV is also not characteristic of obstructive lung disease, as this describes more of a restrictive pattern. Lastly, decreased FEV1 with normal FVC would suggest a restrictive process rather than obstructive lung disease. Therefore, the increase in both TLC and RV is a characteristic finding in obstructive lung disease which underscores the impact of these conditions on lung mechanics and air trapping.