What physiological change occurs during an asthma attack that reduces the mean expiration volume?

During an asthma attack, the muscle walls of the bronchi contract, a process known as bronchoconstriction. This contraction narrows the airways, making it more difficult for air to flow in and out of the lungs. As a result, the mean expiration volume decreases because less air can be exhaled effectively. The constricted airways lead to increased resistance against the airflow, causing a significant impact on respiratory function.

This physiological change is a hallmark of asthma, as it can trigger wheezing, coughing, and shortness of breath, highlighting the importance of managing bronchial muscle tone in individuals with asthma. Understanding this mechanism is crucial for recognizing how asthma attacks can impede normal respiratory physiology.