Which condition may cause an obstructive pattern seen in pulmonary function tests?

An obstructive pattern on pulmonary function tests is characterized by a reduced forced expiratory volume in one second (FEV1) with a relatively preserved forced vital capacity (FVC), leading to a decreased FEV1/FVC ratio. Asthma is a condition that is well-known for producing this obstructive pattern due to airway inflammation, bronchoconstriction, and increased mucus production, which all contribute to an obstruction of airflow, particularly during expiration.

In asthma, the episodic nature of airflow obstruction is often reversible with bronchodilators, distinguishing it from other conditions. The acute bronchial constriction and inflammation associated with asthma can significantly impact airflow, especially during an exacerbation, leading to the characteristic changes observed on pulmonary function tests. This is why asthma is correctly identified as a condition that can cause an obstructive pattern in pulmonary function tests.

In contrast, chronic bronchitis, while also obstructive, may have additional features that complicate the clinical picture. Conditions such as pulmonary fibrosis and pneumonia typically lead to a restrictive pattern rather than an obstructive one, as they affect lung volumes rather than causing difficulty with airflow.