Why does someone with severe asthma become physically fatigued during a prolonged attack? What are the physiologic events that occur during an attack?

Asthma is a chronic respiratory condition in which the airways become inflamed, narrowing and making it difficult to breathe. Severe asthma attacks can cause significant physical fatigue due to extensive physiologic changes during an attack. During an asthmatic episode, the body responds with certain physiological events that can lead to physical fatigue and exhaustion.

The most common physiological event associated with severe asthmatic episodes is bronchoconstriction. Bronchoconstriction occurs when muscles around the airways contract, causing them to become narrower (Rijssenbeek-Nouwens et al., 2019). This reduces the amount of oxygen entering into the lungs, making breathing more labored and strenuous for those suffering from severe asthma. As a result of this narrowed airway passage, more energy must be exerted by respiration muscles in order for adequate oxygenation of cells throughout the body (Vidita et al., 2017). This causes increased workload on both cardiac and respiratory muscles leading to excessive muscular fatigue in cases of severe asthma attacks. Additionally, bronchoconstriction increases airway resistance which leads to increased work rate for ventilation as well as increased levels of exertion from those trying to adequately breathe (McConnell & Allen 2020). As such, someone suffering from a prolonged attack will experience considerable physical tiredness due to these metabolic demands placed on their body during an attack.