What do pulmonary function tests (PFTs) typically show in obstructive pulmonary disease?

In obstructive pulmonary disease, pulmonary function tests (PFTs) typically demonstrate a decreased ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC). This decrease occurs because in obstructive diseases, airflow is impeded, leading to a disproportionately greater reduction in FEV1 compared to FVC.

In conditions such as asthma and chronic obstructive pulmonary disease (COPD), patients often struggle to exhale air effectively due to narrowed airways or inflammation. As a result, even though the overall capacity (FVC) might remain relatively normal or only slightly reduced in some cases, the forced expiratory volume over one second (FEV1) takes a more significant hit. This results in an FEV1/FVC ratio that is diminished, indicating the obstructive nature of the pathology.

Understanding this ratio is crucial, as it helps differentiate between various types of lung diseases. A decreased FEV1/FVC is characteristic of obstructive diseases, contrasting with restrictive diseases, where both FEV1 and FVC are reduced but the FEV1/FVC ratio typically remains normal or is increased. Thus, recognizing this pattern is key in diagnosing and managing respiratory conditions effectively.