Exercise-induced asthma

　　In the etiology of exercise-induced asthma (EIA), exercise intensity is the only trigger factor, and allergic rhinitis can also trigger exercise-induced asthma. The pathogenesis of exercise-induced asthma has not been fully elucidated, and it is currently believed that the following three factors are involved in its pathogenesis:

　　1. Heat and water loss during intense exercise, a large amount of air passes through the airways in a relatively short period of time; at the same time, breathing through the mouth allows the inhaled air to enter the lower respiratory tract without being moistened and warmed by the nasal cavity, leading to a decrease in the temperature of the bronchial mucosa, a large loss of airway moisture, and an increase in the osmotic pressure of the surface fluid of the respiratory tract epithelium. The increase in osmotic pressure and the decrease in airway temperature can induce bronchospasm of the smooth muscle.

　　2. Inflammatory response and inflammatory mediators since the essence of asthma is chronic airway inflammation, it is believed that exercise-induced asthma is no exception. However, the results are not entirely as expected. Although some studies have found that after 3 hours of exercise, the level of eosinophils and mast cells in BALF slightly increased, other studies did not find that the content of inflammatory cells and inflammatory mediators such as histamine, trypsin, and leukotriene C4 in the local airway tissue of EIA changed. In recent years, the role of LTD4 in the pathogenesis of EIA has gradually been recognized. The concentration of LTD4 in the BALF of EIA patients is significantly increased, and administration of LTD4 receptor antagonists 20 minutes before exercise can significantly reduce the severity of bronchospasm and shorten the recovery time.

　　3. Nervous mechanism it has been found that the sympathetic nervous response of EIA patients during exercise is lower than that of normal people; pre-exercise administration of norepinephrine can significantly reduce the severity of bronchospasm. In addition, the vagus nerve is also involved in the pathogenesis of EIA.

　　Complications of exercise-induced asthma (EIA) can be referred to as variant asthma, and the specific aspects are as follows:

　　1. Lower respiratory tract and lung infection

　　According to statistics, about half of the cases are induced by upper respiratory tract viral infections. As a result, the immune function of the respiratory tract is disturbed, making it susceptible to secondary lower respiratory tract and lung infections. Therefore, it is necessary to strive to improve the immune function of asthmatic patients, maintain airway patency, clear respiratory tract secretions, keep the ward clean, prevent colds, and reduce infections; once there are signs of infection, appropriate antibiotics should be selected based on bacteria and drug sensitivity for treatment.

　　2. Water and electrolyte and acid-base imbalance

　　Due to the onset of cough variant asthma, hypoxia, inadequate intake of food, dehydration, and cardiac, liver, especially respiratory and renal insufficiency, water and electrolyte imbalances and acid-base imbalances often occur, all of which are important factors affecting the efficacy and prognosis of asthma. It is necessary to strive to maintain water and electrolyte and acid-base balance, monitor electrolytes daily or even at any time, and promptly detect and treat abnormalities.

　　3. Pneumothorax and mediastinal emphysema

　　Due to gas trapping in the alveoli during the onset of cough variant asthma, the alveoli become overinflated, resulting in a significant increase in intrapulmonary pressure. Chronic asthma complicated with emphysema can lead to the rupture of bullae, forming spontaneous pneumothorax; excessive peak airway and alveolar pressure during mechanical ventilation can also easily cause alveolar rupture, leading to barotrauma, which can result in pneumothorax and even mediastinal emphysema.

　　Exercise-induced asthma (EIA) can occur in any age group, especially prevalent in adolescents. Patients usually begin to experience chest tightness, wheezing, shortness of breath, cough, and difficulty breathing minutes after intense exercise. Symptoms reach their peak 5 to 10 minutes after exercise stops, resolve spontaneously within 30 to 60 minutes, and only a few cases may persist for a longer period and require medication. The appearance of EIA symptoms is related to the type of exercise, with the most common types being cycling, running, and figure skating. In contrast, EIA is less common during sports activities in warm and humid environments, such as swimming, badminton, and tennis. EIA can occur under any climatic conditions, but the incidence increases when breathing dry cold air, while it is less likely to occur in warm and humid climates.

　　Leukotriene receptor antagonists such as Ankelai and Sinusine, antihistamine H1 receptor antagonists, and calcium channel blockers all have certain preventive effects on exercise-induced asthma (EIA), as follows:

　　1. Ankelai is used for the prevention and long-term treatment of asthma. For asthma patients whose condition cannot be completely controlled by beta-agonist therapy, Ankelai can be used as a first-line maintenance treatment.

　　2. Sinusine is indicated for the prevention and long-term treatment of asthma in adults aged 15 years and older, including the prevention of asthma symptoms during the day and at night, the treatment of asthma patients sensitive to aspirin, and the prevention of exercise-induced bronchospasm. This product is also used to alleviate symptoms caused by allergic rhinitis (seasonal allergic rhinitis and perennial allergic rhinitis in adults aged 15 to 15 years).

　　3. H1 histamine receptor antagonists prevent histamine from acting on target cells by reversibly competing with histamine receptor sites on cells, exerting antiallergic effects through blocking and antagonizing H1 receptors to prevent the occurrence of a series of physiological reactions.

　　4. Calcium channel blockers, the calcium channel blockers currently used in clinical practice mainly act on the L subtypes of voltage-dependent Ca2+ channels selectively.

　　The main examinations for exercise-induced asthma (EIA) include pulse diagnosis, blood pressure, pulmonary function tests, and exercise tests. Some studies have found that after 3 hours of exercise, the number of eosinophils and mast cells in BALF increases slightly, but other studies have not found that the content of inflammatory mediators such as histamine, elastase, and leukotriene C4 in the local airway tissue of EIA has changed.

　　Standard exercise provocation test, also known as exercise treadmill test. The subjects continue to exercise for 6 to 8 hours when they reach the maximum heart rate [(220-age)×80%] (submaximal heart rate). FEV1 or PEF is measured every 5 minutes before and after exercise, and continues for 15 to 30 minutes after exercise stops. If FEV1 or PEF decreases by more than 15% after exercise compared to before exercise, it is considered a positive exercise provocation test, and exercise-induced asthma can be diagnosed.

　　For exercise-induced asthma (EIA), it is recommended to eat detoxifying and cooling, cough-relieving and asthma-relieving foods, as well as fresh vegetables and fruits. It is forbidden to eat foods containing allergens such as animal protein, eggs, and honey. It is also forbidden to eat seafood, pungent and spicy foods, and刺激性, preserved, and roasted foods. Eating the following foods can greatly improve symptoms.

　　1. Red heart radish:The root of Brassica rapa, a herbaceous plant in the cruciferous family.

　　2. Sea cucumber skin:Sea cucumber, also known as jellyfish or white skin, resembles an umbrella and also looks like a white mushroom.

　　3. Coffee powder:Coffee beans are roasted, and there are many roasting methods. After roasting well, they are ground into powder and can be directly brewed or cooked.

　　The main treatment methods for exercise-induced asthma (EIA) include non-drug treatment and drug treatment. The specific details are as follows:

　　One: Non-drug treatment

　　1. Advise patients to avoid cold and dry environments and exercise in warm and humid environments.

　　2. It is recommended that patients breathe through the nose instead of the mouth during exercise, but in practice, this measure is difficult to complete. At this time, patients can wear a mask to provide warming and humidification.

　　3. Perform warm-up exercises before intense exercise, because research has found that warm-up exercises can cause the patient to enter an exercise refractory state, that is, EIA patients experience a reduction in bronchospasm within 40 minutes after the same exercise, or even no spasm at all.

　　Two: Drug treatment

　　1. Beta-2 adrenergic agonists: They are the most effective drugs for treating exercise-induced asthma, and about 90% of patients can effectively prevent asthma attacks by using beta-2 adrenergic agonists before exercise. It is recommended to use inhalers such as salbutamol (Ventolin aerosol) or terbutaline aerosol. Apply 10 to 20 minutes before exercise. If the exercise lasts for more than 2 hours, and symptoms such as asthma and chest tightness appear, the medication can be repeated once. Long-acting beta-2 adrenergic agonists like salmeterol can last up to 10 hours, which is suitable for long-duration exercise or for those who are not convenient to take medication before exercise.

　　2. Cromolyn: It is a mast cell membrane stabilizer and the first-line drug for treating EIA. Its indications are for those who cannot effectively control attacks with the sole use of β2-agonists and those who experience significant side effects when using β2-agonists before exercise. The combination of cromolyn with β2-agonists can increase efficacy. Cromolyn has two advantages: first, it does not increase heart rate, making it suitable for elderly patients and those with heart damage; second, it can prevent the late-phase bronchospasm response induced by exercise.

　　3. Theophylline: Due to its relatively weak bronchodilator effect, significant side effects, and slow onset time, it is not recommended as a first-line drug for preventing EIA. Oral theophylline 100-200mg 2 hours before exercise has a preventive effect.

　　4. Anticholinergic drugs: They can prevent some EIA attacks, but their efficacy is not as good as that of β2-agonists and cromolyn. Anticholinergic drugs are more effective for asthma patients sensitive to cold air and polluted air. The slow onset of action limits its application in EIA.

　　5. Glucocorticoids: For patients with normal lung function at rest, the prophylactic administration of β2-agonists and/or cromolyn before exercise can effectively control attacks. For asthma patients with abnormal lung function at rest, it is necessary to first control asthma and improve lung function when treating EIA, so that the above pre-exercise treatment can take effect. Long-term regular use of glucocorticoids can suppress airway inflammation, reduce airway reactivity, and once the patient's resting lung function reaches normal, they can use the above drugs before exercise like patients with normal lung function to prevent EIA attacks. The immediate prophylactic effect of glucocorticoids is poor.

　　Subjective factors affecting asthma prognosis, such as the age of the patient, are very important indicators. Usually, the prognosis of children with asthma and adolescents with asthma is good, while the prognosis of elderly asthma is poor.