What is the cause of exercise-induced asthma

Exercise-induced asthma is also a type of asthma. The main cause of the disease is the amount of exercise. Allergic rhinitis can also induce exercise-induced asthma. Therefore, it is important to clarify the cause of exercise-induced asthma and then treat it correctly.

1. The amount of exercise is the only triggering factor . In addition, allergic rhinitis can also induce exercise-induced asthma.

2. Heat loss and water loss

During strenuous exercise, a large amount of air passes through the airways in a relatively short period of time; at the same time, mouth breathing allows the inhaled air to enter the lower respiratory tract directly without being moistened and warmed by the nasal cavity, which causes the bronchial mucosal temperature to drop. A large amount of airway water loss causes the osmotic pressure of the fluid on the surface of the respiratory epithelium to increase. Physical stimulation such as increased osmotic pressure and decreased airway temperature can induce bronchial smooth muscle spasm.

3. Inflammatory response and inflammatory mediators

Since the essence of asthma is chronic inflammation of the airways, it is believed that exercise-induced asthma is no exception. However, the research results are not exactly as expected. Although some experiments have found a slight increase in eosinophil and mast cell degranulation in BALF 3 hours after exercise, other studies have not found changes in the levels of inflammatory cells and inflammatory mediators such as histamine, tryptase, and leukotriene C4 in local airway tissues of EIA. In recent years, the role of LTD4 in the onset of EIA has gradually been recognized. The LTD4 concentration in the BALF of EIA patients is significantly increased. Giving LTD4 receptor antagonists 20 minutes before exercise can significantly reduce the degree of bronchospasm and shorten its recovery time.

4. Neural Mechanism

Studies have found that the sympathetic nerve responsiveness of EIA patients during exercise is lower than that of normal people; giving norepinephrine before exercise can significantly reduce the degree of bronchospasm. In addition, the vagus nerve is also involved in the onset of EIA.