What does the FEV1/FVC ratio help to distinguish?

The FEV1/FVC ratio is a critical metric in pulmonary function testing that primarily helps to differentiate between obstructive and restrictive lung diseases. In obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), airflow is impeded, resulting in a significantly reduced FEV1 (forced expiratory volume in one second) while the FVC (forced vital capacity) is less affected. This leads to a decreased FEV1/FVC ratio, typically below the normal threshold of around 70%.

In contrast, restrictive lung diseases, like pulmonary fibrosis or sarcoidosis, involve overall reduced lung volume which affects both FEV1 and FVC. However, the FEV1 may be proportionately reduced with the FVC, thus maintaining a normal or even elevated FEV1/FVC ratio. By examining this ratio, healthcare providers can assess whether the underlying issue is primarily obstructive or restrictive, guiding further evaluation and management.

The other options address different aspects of lung health but do not specifically utilize the FEV1/FVC ratio for their distinctions. For example, while normal lungs can be distinguished from diseased lungs using various metrics, the FEV1/FVC ratio is particularly informative for identifying the type of lung disease.