Bronchial asthma is a chronic inflammatory disease of the airways involving a variety of cells, including inflammatory cells (eosinophils, mast cells, T lymphocytes, neutrophils, etc.), airway structural cells (airway smooth muscle cells and epithelial cells, etc.) and cellular components. This chronic inflammation leads to airway hyperresponsiveness in susceptible individuals, and when exposed to physical, chemical, and biological stimuli, widespread and variable reversible airflow limitation occurs, resulting in recurrent episodes of wheezing, coughing, shortness of breath, and chest tightness, often occurring or worsening at night and/or early in the morning, with most children in remission with treatment or on their own. Children are in the process of growth and development, and the diagnosis and treatment methods of asthma differ among children of different ages due to different anatomical, physiological, immunological and pathological characteristics of the respiratory system, different clinical phenotypes of asthma, and different degrees of response to medication and coordination and cooperation. I. Diagnostic criteria 1. Recurrent attacks of wheezing, cough, shortness of breath and chest tightness, mostly related to exposure to allergens, cold air, physical and chemical stimuli, respiratory tract infections and exercise, etc., often occurring or intensifying at night and/or early in the morning. 2.Dispersive or diffuse, expiratory-phase croup can be heard in both lungs during the attack, with prolonged expiratory phase. 3.The above signs and symptoms are effective with anti-asthma treatment or resolve on their own. 4.Except wheezing, cough, shortness of breath and chest tightness caused by other diseases. 5.In case of atypical clinical manifestations (such as no obvious wheezing or croup), at least one of the following should be present: (1) Positive bronchial excitation test or exercise excitation test; (2) Confirmation of reversible airflow limitation: positive bronchodilator test: increase in first second expiratory volume (FEV1) 15 min after inhalation of rapid-acting β2 agonist [such as salbutamol] ≥12% or effective anti-asthma treatment: ≥12% increase in FEV1 after 1-2 weeks of treatment with bronchodilators and oral (or inhaled) glucocorticoids; (3) 20% daily variability in maximum expiratory flow (PEF) (continuous monitoring for 1 to 2 weeks). Those who meet Articles 1 to 4 or 4 and 5 can be diagnosed as asthma. II. Characteristics of wheezing in children under 5 years of age 1. Clinical phenotype and natural course of wheezing in children under 5 years of age: wheezing is a very common clinical manifestation in preschool children, and recurrent wheezing can occur in non-asthmatic preschool children. Wheezing in children under 5 years of age can be classified into 3 clinical phenotypes: (1) Early transient wheezing: Mostly seen in premature births and parental smokers, wheezing is mainly due to environmental factors that delay lung development. (2) Persistent wheezing with early onset (before the age of 3 years): Children mainly present with recurrent wheezing associated with acute respiratory viral infections, with no atopic manifestations and no family history of allergic diseases. Wheezing symptoms usually persist until school age, and some children remain symptomatic at 12 years of age. In children younger than 2 years of age, the cause of wheezing episodes is usually associated with infections such as respiratory syncytial virus, and in children older than 2 years of age, it is often associated with other viral infections such as rhinovirus. (3) Delayed wheezing/asthma: These children have a typical atopic background, often with eczema, asthma symptoms often delayed and persistent into adulthood, and airways with typical asthma pathology. It should be noted, however, that types 1 and 2 of childhood wheeze can only be identified by retrospective analysis. Early intervention in children with wheezing facilitates disease control and therefore it is not advisable to classify patients as such at the time of initial treatment. Evaluation of wheezing in children under 5 years of age: More than 80% of asthma starts before the age of 3 years, and in patients with persistent asthma with pulmonary impairment, pulmonary impairment often starts in preschool, so it is necessary to identify children with wheezing who may develop persistent asthma from preschoolers for effective early intervention. However, there are no specific tests or indicators that can be used to make a definitive diagnosis of asthma in preschool wheezing children. A diagnosis of asthma is highly indicated in children with the following clinical features: (1) frequent episodes of wheezing more than once a month; (2) activity-induced cough or wheeze; (3) intermittent nocturnal cough not caused by a viral infection; (4) persistence of wheezing symptoms beyond 3 years of age. The Asthma Predictor Index can be used effectively to predict the risk of developing persistent asthma in children with wheezing within 3 years of age. Asthma Predictor Index: ≥4 wheezing episodes in the past 1 year, with 1 major risk factor or 2 minor risk factors. Primary risk factors include: (1) parental history of asthma; (2) physician diagnosis of atopic dermatitis; (3) evidence of sensitization to inhaled allergens. Secondary risk factors include: (1) evidence of food allergen sensitization; (2) peripheral blood eosinophils ≥4%; and (3) wheezing unrelated to the flu. If the asthma prediction index is positive, standardized treatment of asthma is recommended. Despite the possibility of overtreatment, antiasthmatic medication significantly reduces the severity and duration of wheezing episodes in preschool children compared with the use of antibiotics. Therefore, diagnostic treatment with anti-asthmatic medication for 2 to 6 weeks is recommended for re-evaluation in preschoolers with recurrent wheezing for which antibiotic therapy has not been effective. It must be emphasized that the majority of preschool children with wheezing have a good prognosis and their asthma-like symptoms may resolve spontaneously with age. Therefore, these children must be reevaluated periodically (3 to 6 months) to determine the need for continued antiasthmatic therapy. Cough variant asthma (CVA) is one of the most common causes of chronic cough in children, with cough as the only or main manifestation, without significant wheezing. The diagnosis is based on: (1) a cough lasting >4 weeks, often attacked or aggravated at night and/or early in the morning, with a predominantly dry cough; (2) no clinical signs of infection, or ineffective after prolonged antibiotic treatment; (3) effective diagnostic treatment with anti-asthmatic drugs; (4) exclusion of other causes of chronic cough; (5) positive bronchial excitation test and/or daily variability of PEF (monitored continuously for 1 to 2 weeks ) ≥ 20%; (6) personal or first- or second-degree relative history of atopic disease, or positive allergen test. The above items 1 to 4 are the basic conditions for diagnosis. 4, asthma diagnosis and disease monitoring and assessment of related tests: 1, pulmonary function test: pulmonary function measurement helps to confirm the diagnosis of asthma, and is also one of the important bases for assessing the severity of asthma and the level of control. For children with suspected asthma with FEV1 ≥ 70% of the normal expected value, bronchial excitation test can be selected to determine airway reactivity, and for children with suspected asthma with FEV1 < 70% of the normal expected value, bronchial diastolic test can be selected to assess the reversibility of airflow limitation. confirm the diagnosis of asthma. 2. Allergy status testing: inhalation allergen sensitization is a major risk factor for the development of persistent asthma in children, and early food sensitization in children increases the risk of inhalation allergen sensitization and predicts the development of persistent asthma. Therefore, allergen skin prick test or serum allergen-specific IgE assay is recommended for all children with recurrent wheezing suspected of asthma, especially preschool children who are unable to cooperate with pulmonary function testing, to understand the patient's allergic status and to assist in the diagnosis of asthma. It is also useful to understand the individual risk factors that contribute to the onset and exacerbation of asthma and helps to develop environmental interventions and determine allergen-specific immunotherapy regimens. 3, Airway non-invasive inflammatory index test: sputum or induced sputum eosinophils, exhaled nitric oxide (FeNO) levels, etc., can be used as asthma airway inflammatory index. Although there are no prospective studies to confirm the exact value of these noninvasive inflammatory markers in the diagnosis of asthma in children, monitoring of these markers can help to assess the level of asthma control and to develop the optimal asthma treatment plan. Staging and grading I. Staging Asthma can be divided into three phases: acute exacerbation, chronic persistent, and clinical remission. Acute exacerbation refers to the sudden onset of symptoms such as wheezing, cough, shortness of breath, chest tightness, etc., or the rapid aggravation of existing symptoms; chronic persistent refers to the occurrence of symptoms such as wheezing, cough, shortness of breath, chest tightness, etc., in different frequencies and/or degrees within the past 3 months; clinical remission refers to the disappearance of symptoms and signs with or without treatment, and the recovery of lung function to the level before the acute exacerbation, and maintenance for more than 3 months. The grading of asthma includes the grading of severity, the grading of asthma control level and the grading of acute attack severity. 1.Grading of severity of disease: The grading of severity of disease is mainly used for the first diagnosis and for children who have been diagnosed but not yet treated according to the standard asthma treatment, as a basis for setting the level of starting treatment plan. 2.Grading of control level: Asthma control level is used to assess whether children with standardized asthma treatment have achieved the asthma treatment goal and to guide the adjustment of the treatment plan to achieve and maintain asthma control. Long-term asthma treatment regimens dominated by asthma control levels allow patients to be treated more adequately and most asthma patients to achieve clinical control. 3.Acute asthma attack severity classification: Acute asthma attacks are often characterized by a progressive exacerbation process with reduced expiratory flow, often triggered by exposure to allergens, irritants or respiratory tract infections. It may occur within hours or days, or occasionally within minutes, which is life-threatening. Therefore, the condition should be properly evaluated in order to provide timely and effective emergency treatment. The goals of treatment are: (1) to achieve and maintain symptom control; (2) to maintain normal activity, including exercise capacity; (3) to bring lung function levels as close to normal as possible; (4) to prevent acute asthma attacks; (5) to avoid adverse effects caused by asthma medication; (6) to prevent death due to asthma. (2) Control treatment should be as early as possible. The principles of long-term, continuous, standardized and individualized treatment should be adhered to. Treatment includes: (1) acute exacerbation: rapid relief of symptoms, such as wheezing and anti-inflammatory treatment; (2) chronic persistence and clinical remission: prevention of symptom exacerbation and relapse, such as avoidance of triggers, anti-inflammation, reduction of airway hyperresponsiveness, prevention of airway remodeling, and good self-management. The combination of pharmacological and non-pharmacological treatments should be emphasized, and the role of non-pharmacological treatments such as asthma prevention and control education, allergen avoidance, management of children's psychological problems, quality of life improvement, pharmacoeconomics, etc. should not be neglected in the long-term management of asthma. Long-term treatment programs are divided into long-term treatment programs for children with asthma aged 5 years and older and long-term treatment programs for children under 5 years of age according to their age. Long-term treatment regimens are divided into 5 levels, and different asthma control medications are available in the regimens from level 2 to level 5. Children with primary asthma who have not been previously treated in a standardized manner are selected for the Level 2, Level 3, or Level 4 treatment regimens, depending on the severity of their disease rating. At all levels of treatment, the treatment regimen was reviewed every 1 to 3 months and adjusted appropriately according to disease control. If asthma is controlled and maintained for at least 3 months, the treatment regimen may be considered for downgrading until the minimum dose to maintain asthma control is determined. If partially controlled, escalation of therapy may be considered to achieve control. However, the child's aspiration technique, adherence to the dosing regimen, allergen avoidance, and other triggers should first be checked before escalating therapy. If not controlled, escalate or step up treatment until control is achieved. In the long-term treatment regimen for childhood asthma, in addition to the regular daily use of control therapy medications, relief medications are used as needed depending on the condition. Inhaled rapid-acting β2 agonists are currently the most effective relievers and are the first choice for acute asthma in children of all ages, usually no more than 3 to 4 times in 1 d. Combined inhalation of anticholinergic drugs is also an option as a palliative drug. children 5 years of age and older can be treated with a single inhaler containing formoterol and budesonide as a control and palliative drug. 1. Long-term treatment options for asthma in children aged 5 years and older: China has a wide geographic area and very uneven socioeconomic development, so the choice of combination therapy requires consideration of both regional and economic differences in addition to efficacy. It must be emphasized that inhaled long-acting β2 agonists (LABA) should not be used as monotherapy at any age, but only as combination therapy when using moderate amounts of inhaled glucocorticoids (ICS). 2. Long-term treatment plan for asthma in children under 5 years of age: For the long-term treatment of asthma in children under 5 years of age, the most effective therapeutic agent is ICS. For most children, low-dose ICS (Tier 2) is recommended as initial control therapy. If low-dose ICS does not control symptoms, increasing the dose of ICS is the best option. Leukotriene receptor antagonists (LTRA) may be used in children who are unable or unwilling to use ICS, or who have allergic rhinitis. Oral extended-release theophylline has some efficacy in the long-term treatment of asthma in children under 5 years of age, and its use should not be completely abandoned clinically; however, theophylline is less effective than low-dose ICS, and the adverse effects are more pronounced.LABA or combination formulations have not been adequately studied in children under 5 years of age. IV. Treatment of acute exacerbations Treatment is individualized on an original basis, depending primarily on the severity of the acute exacerbation and the response to initial therapeutic measures. The hospital treatment process for acute asthma exacerbation is described in [Annex 1]. If an acute asthma attack is treated with asthma relieving drugs such as bronchodilators and glucocorticoids with reasonable application, but still has severe or progressive dyspnea, it is called asthma critical state (asthma persistent state, status asthmaticus). If bronchial obstruction is not relieved in time, it can rapidly develop into respiratory failure and become directly life-threatening, which is then called life-threatening asthma attack (1ife threatening asthma). Any child with critical asthma should be placed in a good medical environment, provided with oxygen to maintain oxygen saturation above 0,92-0,95, monitored with cardiopulmonary monitoring, blood gas analysis and ventilation function, and sedation is prohibited for those who are not extubated. 1, inhaled rapid-acting β2 agonists: use oxygen-driven (oxygen flow 6-8L/min) or air compression pump nebulizer inhalation, the first hour can be every 20 minutes once, and then according to the condition of every 1-4 hours repeat inhalation treatment; drug dose: each inhalation salbutamol 2, 5-5mg or Terbutalin (Terbutalin) 5-10mg. if there is no nebulizer inhaler, can Use pressure type quantitative aerosol (pMDI) through the fog storage tank, each time a single dose of spray, continuous use of 4 ~ 10 spray, the interval of medication and nebulized inhalation method is the same. If there is no condition to use inhaled rapid-acting β2 agonist, subcutaneous injection of epinephrine can be used, but clinical observation should be strengthened to prevent the occurrence of cardiovascular and other adverse reactions. Drug dose: each subcutaneous injection of 1:1000 epinephrine 0,01ml/kg, the maximum dose does not exceed 0,3ml. if necessary, every 20 minutes, but not more than 3 times. If treatment with inhaled rapid-acting β2 agonists is ineffective, intravenous application of β2 agonists may be required. Drug dose: salbutamol 15μg/kg slowly intravenously for more than 10 min; the dose is 1~2μg/(kg?min) [≤5μg/(kg?min)] for severe disease requiring intravenous maintenance drip. When applying β2 agonist intravenously, serious adverse reactions such as arrhythmia and hypokalemia are likely to occur, so it is necessary to strictly control the indications and dose, and make necessary monitoring of ECG, blood gas and electrolytes. 2.Glucocorticoid: Systemic application of glucocorticoid is the first-line drug for the treatment of severe asthma attack in children, and its early use can reduce the severity of the disease and show obvious efficacy 3-4 hours after administration. Drug dose: oral prednisone 1~2mg/(kg?d). Children with severe disease can receive intravenous hydrocortisone succinate 5-10mg/(kg?d) or methylprednisolone 1-2mg/(kg?d), which can be repeated at 4-8h intervals according to the disease. High-dose ICS is helpful in the treatment of asthma attacks in children, and nebulized inhalation of budesonide suspension 1mg/dose is chosen, and it is used once every 6-8 hours. However, in severe cases, inhalation therapy should not replace systemic glucocorticoid therapy to avoid delaying the disease. 3.Anti-cholinergic drugs: They are an integral part of the combination therapy for critical asthma in children, and their clinical safety and efficacy have been established. They should be used in combination as early as possible in severe cases that do not respond well to β2 agonist therapy. Drug dose: ipratropium bromide 250-500μg each time, add β2 agonist solution for nebulized inhalation, the interval is the same as the inhalation of β2 agonist. 4.Aminophylline: Intravenous aminophylline can be used as an additional treatment option for children with critical asthma. Drug dose: loading dose 4-6 mg/kg (≤250 mg), slow intravenous drip 20-30 min, followed by continuous drip maintenance dose 0,7-1 mg/(kg?h) according to age, such as those who have used oral aminophylline, directly use maintenance dose continuous intravenous drip. Can also use intermittent dosing method, every 6 ~ 8 hours slow intravenous drip 4 ~ 6mg/kg. 5. magnesium sulfate: help critical asthma symptom relief, good safety. Drug dose: 25 ~ 40mg / (kg?d) (≤ 2 g / d), divided into 1 ~ 2 times, add 10% glucose solution 20ml slow intravenous infusion (more than 20min), use 1 ~ 3 d as appropriate. Adverse reactions include transient flushing, nausea, etc., usually occur during drug infusion. Overdose may be antagonized by sedation of 10% calcium gluconate. If the condition of children with critical asthma continues to deteriorate after treatment with oxygen therapy, systemic glucocorticoids, β2 agonists, etc., adjuvant mechanical ventilation should be given promptly. In order to consolidate the therapeutic effect, maintain the long-term stability of the child's condition and improve the quality of life, the management of the clinical remission period should be strengthened. 1. Encourage the child to adhere to regular daily PEF measurements, monitor changes in condition, and record the asthma diary. 2. Pay attention to the presence of asthma attack aura, such as cough, shortness of breath, chest tightness, etc. Once they appear, emergency medication should be used promptly to reduce the symptoms of asthma attack. 3.Continue to use long-term control medication after remission, such as using the lowest effective maintenance amount of ICS, etc. 4.Dose adjustment and course of control therapy: for those who use medium to high dose ICS alone, try to reduce the dose by 50% after achieving and maintaining asthma control for 3 months. If control can be achieved with low-dose ICS alone, switch to once-daily dosing. For combined ICS and LABA, reduce ICS by approximately 50% until low-dose ICS is achieved before considering discontinuation of LABA, and consider discontinuation if asthma control is maintained with the lowest dose of ICS and no recurrence of symptoms for 1 year. A significant proportion of children under 5 years of age have spontaneous remission of asthma symptoms, so the control regimen for children of this age should be evaluated at least twice a year to determine the need for continued treatment. 5. According to the specific situation of the child, including the understanding of the triggers and the pattern of previous attacks, study with the child and parents, and propose and take all necessary practical preventive measures, including avoiding exposure to allergens, preventing asthma attacks, and maintaining long-term control and stability of the disease. 6. Treatment of coexisting diseases: 70% to 80% of children with asthma also have allergic rhinitis, and some children have coexisting sinusitis and gastroesophageal reflux. These coexisting diseases can affect the control of asthma and need to be treated at the same time.