What do pulmonary function tests typically show during an acute asthma exacerbation?

During an acute asthma exacerbation, pulmonary function tests typically reveal a decreased peak expiratory flow rate. This is a hallmark of airway obstruction caused by bronchoconstriction, inflammation, and increased secretions, all of which contribute to narrowing of the airways.

In this condition, patients struggle to exhale forcefully, which results in a lower rate of airflow. The peak expiratory flow rate directly measures how quickly air can be expelled from the lungs, and any significant decrease indicated in this measure reflects the severity of the bronchial obstruction and the patient's compromised respiratory function.

Additional pulmonary function metrics, such as FEV1 (forced expiratory volume in one second) versus FVC (forced vital capacity), often show alterations leading to reduced ratios during an exacerbation. In contrast, the total lung capacity generally remains normal, but the dynamics of airway resistance change due to the acute event.