Certified Respiratory Therapist Practice Exam

Which of the following would indicate a restrictive disorder in lung function testing?

1. Decreased FEV1 and increased FEV1%

2. Normal FVC and decreased FEV1%

3. Decreased FVC with normal FEV1

4. Increased FVC and decreased FEV1

The correct answer is: Decreased FVC with normal FEV1

A decreased forced vital capacity (FVC) combined with a normal forced expiratory volume in one second (FEV1) is a hallmark indicator of restrictive lung disorders. In restrictive lung diseases, the lung volumes are reduced due to conditions that limit lung expansion, such as pulmonary fibrosis or pleural diseases. In this scenario, the normal FEV1 suggests that the airflow is not obstructed, which often remains intact in restrictive disorders, but the reduction in FVC implies that the total lung capacity is compromised. This pattern is characteristic of restrictive lung function as it reflects an inability of the lungs to fully expand rather than a blockage of airflow, enabling clear differentiation from obstructive disorders where FEV1 would typically be decreased alongside a lower FEV1%. Other options would not appropriately represent a restrictive pattern. For instance, a decreased FEV1 with an increased FEV1% may indicate an obstructive process, while a normal FVC combined with a decreased FEV1% does not suggest restriction, as it implies that total lung capacity is unaffected. An increased FVC coupled with a decreased FEV1 is inconsistent with both restrictive and obstructive patterns, further underscoring why the choice indicating decreased FVC with normal FEV1 is the representative