Which of the following is a hallmark feature of asthma?

Airflow obstruction is a hallmark feature of asthma. This condition is characterized by reversible obstruction of the airways, primarily due to inflammation, bronchoconstriction, and increased mucus production. During an asthma attack, patients typically experience difficulty in breathing as the airways constrict and airflow becomes restricted. This feature distinguishes asthma from other respiratory conditions and is crucial for diagnosis.

In asthma, the airflow limitation is often variable and can improve spontaneously or with treatment, which is an essential aspect of its management. Recognizing this reversible nature is important for understanding how asthma can be effectively controlled with bronchodilators and anti-inflammatory medications.

The other options do not reflect primary characteristics of asthma. For instance, while patients may experience cough in asthma, it is not always chronic or productive, and fever is not a common symptom associated with asthma episodes. Heart palpitations are not a central feature of asthma either, although some patients may report them, particularly when anxiety accompanies an asthma attack. Thus, airflow obstruction captures the essence of the pathophysiology of asthma and is essential for both diagnosis and management.