Which type of lung disease is characterized by a decrease in the FEV1/FVC ratio?

Obstructive lung disease is characterized by a decrease in the FEV1/FVC ratio due to the presence of airflow limitation. In obstructive conditions, such as asthma or chronic obstructive pulmonary disease (COPD), the forced expiratory volume in one second (FEV1) is significantly reduced while the forced vital capacity (FVC) may remain relatively normal or slightly decreased. This results in a reduced FEV1/FVC ratio, typically less than 70%, indicating that the ability to exhale air is compromised.

In contrast, restrictive lung diseases, which involve conditions such as pulmonary fibrosis, affect lung expansion and typically result in both FEV1 and FVC being reduced, but the FEV1/FVC ratio is often preserved or even increased. This distinction emphasizes the underlying pathology of obstructive lung disease, which primarily involves airway narrowing or obstruction leading to impaired airflow, rather than a reduction in total lung capacity or compliance, which is more characteristic of restrictive lung disease.

Mixed lung diseases can feature aspects of both obstructive and restrictive impairments, making the FEV1/FVC ratio variable, while chronic lung disease is a broader term that encompasses various chronic respiratory conditions without specifying the nature of airflow dynamics. Thus, the clear link