| disease | Pediatric Bronchial Asthma |
| alias | Infantile Asthma, Asthma |
Bronchial asthma, commonly referred to as asthma, is a reversible, obstructive respiratory disease characterized by recurrent episodes of cough, wheezing, and dyspnea, accompanied by airway hyperresponsiveness. It is generally believed to be related to allergic reactions, but numerous studies have shown that not all asthma patients have clear immunological changes, and conversely, not all patients with allergic diseases develop asthma. Asthma can occur at any age, but most cases begin before the age of 4-5. Active prevention and treatment of childhood bronchial asthma are of great significance for the prevention and treatment of adult bronchial asthma.
bubble_chart Epidemiology
1. Prevalence The reported prevalence rates of asthma vary among countries, but surveys from various nations confirm an increasing trend in the prevalence of childhood asthma. There are few reports on the prevalence of childhood asthma in our country. According to a survey conducted from 1988 to 1991 involving nearly 1 million children from 20 provinces and cities across the country, the overall prevalence of asthma among urban and rural children was 0.9% to 1.1%. However, prevalence rates differ by region. For example, in 1978, a survey by Huashan Hospital in Shanghai of 140,000 people found the prevalence of asthma among urban children to be 1.9%, and 1.3% in rural areas. In 1984, a survey in Changsha of 250,000 people found the prevalence of asthma among children to be 1.3%, higher than that in adults. A survey by Xi'an Children's Hospital of 27,000 people found the prevalence of asthma to be 1.3%, with infants and young children reaching as high as 5.2%. A survey in Guangdong Province of 450,000 people found the prevalence of asthma among children to be 0.9%. A survey in Henan Province of 400,000 people found the prevalence of asthma among children to be 0.9%. A survey in Chongqing of 144,000 people found the prevalence to be 1.6%. Additionally, statistics from 1979 to 1988 show that approximately 120,000 children were hospitalized due to wheezing symptoms, accounting for 4.8% of pediatric hospitalizations during the same period, with a mortality rate of 0.03%.
2. Age It is generally believed that about 70-80% of cases occur before the age of 5. Data from Shanghai indicates that 75% of cases occur before the age of 4, with the earliest onset at 3 months after birth. According to a survey in Xi'an, 50% of childhood asthma cases occur before the age of 3. Reports from both domestic and international sources indicate that the prevalence of asthma is equal among boys and girls from the age of 10 to adolescence.Triggers The factors that induce bronchial asthma are multifaceted, and common factors include the following:
1. Allergens: Allergens can be roughly divided into three categories: ① Pathogens and their toxins that cause infections. Infantile asthma attacks are often closely related to respiratory infections, with more than 95% of infant asthma cases caused by respiratory infections. The main pathogens are respiratory viruses, such as respiratory syncytial virus (RSV), adenovirus, influenza, and parainfluenza viruses. It has been proven that RSV infection can cause wheezing due to a specific IgE-mediated type I allergic reaction. Other local infections such as sinusitis, tonsillitis, and dental caries may also be triggering factors. ② Inhalants: Usually inhaled through the respiratory tract. Skin tests in China show that the main allergens causing asthma are dust mites, house dust, mold, multi-valent Mongolian snakegourd root (Artemisia, ragweed), feathers, etc. There are also reports of asthma caused by contact with silkworms, especially mites as inhalant allergens, which play a significant role in respiratory allergic diseases. Children are more allergic to mites than adults, and the spring and autumn seasons are the most suitable for mite survival, hence dust mite asthma is more common in these seasons, especially at night. Additionally, asthma attacks caused by inhaled allergens are often related to season, region, and living environment. Once contact is stopped, symptoms can be relieved or disappear. ③ Food: Mainly heterologous proteins, such as milk, eggs, fish, shrimp, spices, etc. Food allergies are common in infancy and gradually decrease after the age of 4-5.
3. Climate: Child patients are very sensitive to climate changes, such as sudden cold temperatures or reduced air pressure, which can often trigger asthma attacks. Therefore, the incidence of asthma in children generally increases significantly in spring and autumn.
4. Psychological factors: Although psychological factors are less obvious in causing asthma attacks in children than in adults, asthmatic children are often affected by emotions, such as crying, laughing, or being angered or frightened, which can trigger asthma attacks. Some scholars have proven that emotional excitement or other psychological activity disorders are often accompanied by vagus nerve excitation.
5. Genetic factors: Asthma is hereditary. The family and personal allergy history of affected children, such as asthma, infant eczema, urticaria, and allergic rhinitis, have a higher prevalence than the general population.
6. Exercise: Foreign reports indicate that about 90% of asthmatic children can have asthma triggered by exercise, also known as exercise-induced asthma (EIA), which is more common in older children. Intense and continuous running (for more than 5-10 minutes) is most likely to induce asthma, and its mechanism is non-immune.
Bronchial asthma is a complex disease caused by multiple factors. The mechanism of disease is still unclear, and the currently recognized mechanisms include the following three aspects.
1. Type I hypersensitivity and IgE synthesis regulation disorder. After the antigen (allergen) initially enters the human body, it acts on B lymphocytes, turning them into plasma cells that produce IgE. IgE adsorbs onto mast cells or basophils, with its Fc segment binding to specific receptors on the cell membrane, firmly attaching IgE to the cell membrane, thereby sensitizing the body. When the corresponding antigen re-enters the sensitized body, it adsorbs onto the mast cells and basophils, binding with IgE, leading to cell membrane degranulation and the release of a series of chemical mediators including histamine, slow-reacting substance, bradykinin, 5-hydroxytryptamine, and prostaglandins. These bioactive substances can cause capillary dilation, increased permeability, smooth muscle spasm, and glandular hypersecretion, leading to bronchial asthma.
Recent studies have shown that the increase in IgE is also related to cellular immune function disorders. A large number of studies have proven that T cells not only have quantitative changes but may also have functional defects. In addition, high IgE may also be related to the delayed maturation of suppressor T cells.
2. Airway inflammation changes. Through fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) techniques, biopsies of asthma animal models and asthma patients have shown varying degrees of inflammatory changes in airway tissues.
3. Airway hyperresponsiveness. Airway hyperresponsiveness refers to the abnormally increased responsiveness of the airway to various specific or non-specific stimuli. Asthma patients exhibit airway hyperresponsiveness. Airway hyperresponsiveness includes immediate reactions (Type I hypersensitivity) and sustained reactions. It is currently believed that sustained airway hyperresponsiveness is mainly related to airway inflammation. The mechanism of seasonal epidemic airway hyperresponsiveness is mainly related to inflammatory mediators. Studies have found that the responsiveness of the airway to histamine and acetylcholine is parallel to the severity of asthma in children. These are also related to neural regulation disorders, especially autonomic nervous system dysfunction.
It is known that bronchial smooth muscle is dually innervated by the sympathetic and parasympathetic nerves, maintaining a dynamic balance under the regulation of the brain-hypothalamus-pituitary axis. In normal individuals, the tension of bronchial smooth muscle depends on the excitatory state of cholinergic receptors, whereas in asthma patients, it does not. Their parasympathetic nerve tension is increased, α-adrenergic nerve activity is enhanced, and β-adrenergic nerve function is reduced or partially blocked. Due to these abnormalities, the hyperresponsiveness of the airway in asthma patients is one of the pathophysiological bases of asthma attacks.
bubble_chart Pathological Changes
The main pathological changes in asthma include bronchial smooth muscle spasm, inflammatory cell infiltration, thickening of the basement membrane, airway mucosal edema, epithelial shedding mixed with cellular debris, increased mucus secretion, and dysfunction of the mucosal cilia. These changes lead to bronchial mucosal hypertrophy and mucus plugging within the bronchi. The result of these pathological changes is the narrowing of the airway lumen, leading to increased airway resistance and the manifestation of asthma.
bubble_chart Clinical Manifestations
In 1984, the National Asthma Academic Conference recommended classifying asthma into three categories based on the causes of its induction: extrinsic, intrinsic, and mixed asthma, following the international unified classification method. However, it is sometimes difficult to distinguish clinically, and it does not provide guidance for prognosis judgment.
1. Extrinsic asthma: It mostly occurs before the age of 6, with a clear personal and/or family history of allergic diseases; it has obvious seasonality and regionality; inhalation allergen skin tests are often positive; bronchial provocation tests can also be positive. In older children, the prelude symptoms are mainly allergic rhinitis, without fever, continuous sneezing, clear nasal discharge, pale nasal mucosa, increased eosinophils in nasal secretions and peripheral blood, elevated serum IgE, and higher airway hyperresponsiveness than normal children.
2. Intrinsic asthma: It was previously thought to be more common in adult-type asthma, with severe and stubborn conditions, mostly perennial or chronic recurrent attacks, without obvious personal or family allergy history, mostly negative skin tests, and no obvious seasonality. In the past, infectious asthma was considered intrinsic asthma, but recent years have confirmed that infants with recurrent wheezing due to RSV-induced bronchiolitis have specific RSV IgE in their airway secretions.
3. Mixed asthma: Any tracheal asthma is a complex disease caused by multiple factors. The mechanism of disease is still unknown, and the currently recognized mechanisms are as follows.
Onset: The onset can be acute or slow. Infants and young children often have 1-2 days of upper respiratory tract infection before the onset, similar to general bronchitis. Older children have a more acute onset, mostly at night, possibly related to changes in night intermediate qi; accumulation of more allergens such as mites and house dust indoors; and decreased secretion of adrenaline in the blood at night. Most attacks gradually subside after a few hours to a day. In particularly severe cases, the onset may be critical asthma from the start, or last for a long time, even several days, called status asthmaticus.
Symptoms during an attack: The child is dysphoric and restless, with difficulty breathing, especially expiratory difficulty, often unable to lie flat, shrugging and bending the back when sitting, showing orthopnea. Sometimes wheezing sounds can be heard outside the room. The child's complexion is pale, with nasal flaring, cyanosis of the lips and nails, even cold sweating, and a frightened and restless expression, often indicating a critical condition that requires active treatment.
At the beginning of the disease, there is only dry cough, followed by wheezing symptoms. As bronchial spasm is relieved, thick white sputum is expelled, and breathing gradually subsides. Some children may have severe cough leading to upper abdominal muscle pain. It may or may not be accompanied by fever. Chest signs include chest retraction during inspiration, and bulging of the suprasternal fossa and intercostal spaces during expiration due to increased intrathoracic pressure, with significant jugular vein distension. Percussion reveals tympanic sounds in both lungs, with diaphragmatic descent and reduced cardiac dullness, suggesting lung qi swelling (but in children, this lung qi swelling sign often disappears on its own when the condition is relieved, so it is called pulmonary inflation sign). At this time, breath sounds are weakened, and wheezing and dry rales can be heard throughout the lungs. In severe cases, especially status asthmaticus, breath sounds are almost absent in both lungs, and right heart load increases due to lung stirred pulse spasm, as well as severe hypoxemia leading to heart failure.
Clinical manifestations also vary depending on the allergen causing the asthma attack. Those caused by upper respiratory tract infection often have dry and wet rales in the chest, accompanied by fever, increased total white blood cells, etc. If caused by inhalation allergens, it is often accompanied by nasal itching, clear nasal discharge, sneezing, dry cough, followed by wheezing and breathlessness. Those highly sensitive to food mostly do not have fever, and in addition to asthma symptoms, they often have lip and facial swelling, vomiting, abdominal pain, diarrhea, and urticaria, mostly appearing a few minutes after eating. If the sensitivity to food is mild, symptoms appear more slowly, often only grade I asthma or difficulty breathing.
Intermittent symptoms during remission At this time, although there is no difficulty in breathing and the child appears normal, they may still feel chest discomfort. Since the pathological factors causing bronchial susceptibility still exist, exposure to infection or external allergens can immediately trigger an asthma attack. However, in most children, the symptoms can completely disappear, and no wheezing can be heard in the lungs.
The sputum of children with bronchial asthma is generally colorless, viscous, and transparent, sometimes foamy, and may turn yellow when accompanied by bacterial infection. A large number of eosinophils can be found in the sputum, and sometimes Charcot-Leyden crystals can be seen, the latter being composed of low molecular weight polypeptides. Most children have difficulty expectorating the thick sputum, which is scant in quantity. When symptoms are relieved, a significant improvement in breathing difficulty is observed after expectorating a large amount of thick, foamy sputum. However, in infants and preschool children, most of the sputum is swallowed.
Chronic recurrent symptoms: Asthma itself is a chronic disease, but some children experience year-round attacks, or although they can be controlled with medication, the stage of remission is very short, mostly due to poor control of acute attacks or recurrent infections. Due to long-term bronchospasm, increased airway resistance leads to lung qi swelling. Physical examination may reveal a barrel-shaped chest, increased anteroposterior diameter, lowered lung bases, and reduced relative dullness of the heart. Even without acute attacks, chest tightness and shortness of breath are often felt after activity, and wheezing sounds are often heard in the lungs, or frequent infections with copious sputum, leading to atelectasis due to blockage by inflammatory secretions, mostly seen in the right middle lobe. Some develop bronchiectasis, mostly in the right middle lobe. Occasionally, mediastinal emphysema or pneumothorax may occur. Severe cases may have varying degrees of cardiopulmonary dysfunction, and even cor pulmonale. Children with concurrent allergic rhinitis may also develop chronic sinusitis and otitis media. As the disease progresses, oxygen metabolism disorders worsen, and these children often exhibit short stature, malnutrition, hunchback, and often appear in a state resembling social withdrawal.
bubble_chart Auxiliary Examination
The diagnosis of infantile asthma generally does not require special laboratory tests, but it is necessary to further determine whether it is exogenous, endogenous, or mixed asthma, and to further understand its disease cause and mechanism of disease, and to evaluate the efficacy and prognosis. Therefore, it is necessary to conduct some targeted laboratory tests.
1. Eosinophil count: Most children with allergic rhinitis and asthma have an eosinophil count in the blood exceeding 300×106L (300/mm3). Increased eosinophils and the presence of Curschmann's spirals and Charcot-Leyden crystals can also be found in the sputum.
2. Blood routine: Red blood cells, hemoglobin, total white blood cell count, and neutrophils are generally normal, but the total white blood cell count may increase after the use of β-receptor agonists. If there is a bacterial infection, both will increase.
3. Chest X-ray: Most are normal during the remission stage. During the attack stage, most children may show simple hyperinflation or increased hilar vascular shadows; with concurrent infection, pulmonary infiltration may appear, and different signs may be present with other complications, but chest X-ray helps to exclude asthma caused by other reasons.
4. Skin allergen test: The purpose of the allergen test is to understand the disease cause of asthma in children and to select specific desensitization therapy. Skin tests are provocation tests performed on the skin with allergens, usually on the extensor side of the upper arm. There are three main methods: ① Patch test: used to determine the sensitizing substances of exogenous contact dermatitis; ② Scratch test: mainly used to detect sensitizing substances of immediate reactions. A drop of the test agent is applied to the test site, then a scratch is made, with the depth of the scratch not causing bleeding. The reaction is observed after 20 minutes, with a positive reaction showing redness and wheal. The advantage of this method is safety and not causing severe reactions, but the disadvantage is that it is not as sensitive as intradermal tests; ③ Intradermal test: more sensitive, simple to operate, and does not require special equipment. It is currently the most commonly used method for specific tests. It is generally used to observe immediate reactions, but can also observe delayed reactions. The amount of allergen extract injected in the intradermal test is 0.01～0.02ml. The concentration of the extract is generally 1:100 (W/V), but for Mongolian snakegourd root, a concentration of 1:1000～1:10000 is often used.
The purpose of the skin test is to identify the allergens causing asthma, so sympathomimetic drugs, antihistamines, theophylline, and corticosteroids should be discontinued 24～48 hours before the test to avoid interference with the results.
5. Pulmonary function test: Pulmonary function tests are important for assessing the severity of asthma and judging the efficacy. They generally include lung volume, lung ventilation, diffusion function, flow-volume loop, and respiratory mechanics tests, but they require more sophisticated equipment and cannot be monitored at any time. Children with asthma often show an increase in total lung capacity (TLC) and functional residual capacity (FRC), while residual volume (RV) and vital capacity (VC) may be normal or decreased; more importantly, changes in respiratory flow rates are observed, manifested as changes in forced vital capacity (FVC), forced expiratory flow at 25～75% of FVC (FEF25～75%), and peak expiratory flow rate (PF).
In recent years, scholars both domestically and internationally have recommended the use of miniature flow meters to measure the Peak Expiratory Flow Rate (PEFR) for monitoring the condition changes of asthma patients at any time. The method involves the subject standing, holding the peak flow meter in the right hand, taking a deep breath of fetid mouth odor, and immediately inserting the mouthpiece of the instrument into the mouth. The lips should tightly enclose the mouthpiece, without fistula disease air, exhaling with maximum force and speed, repeating 3-4 times, and selecting the highest value for recording and evaluation. During the examination, the child should not hold their breath between inhalation and exhalation, and the procedure should be demonstrated to the child repeatedly before the test. At the same time, height should be measured and then compared with the standard values of normal children in the local area. If it is below normal, inhaling a bronchodilator such as salbutamol aerosol 2 puffs, and if the value can increase by 15%, it has diagnostic significance. The peak flow meter test can not only diagnose asthma but also monitor the condition of asthma patients, measure airway hyperresponsiveness, with its greatest feature being portable, convenient for parents and children to self-monitor the condition, record in an asthma diary, adjust the treatment plan, and achieve the goal of controlling asthma attacks for a longer period. However, in critically ill children, due to systemic exhaustion or a sharp decrease in airway ventilation, it is often not suitable to repeatedly perform the test.
6. Blood Gas Analysis Blood gas analysis is an important laboratory test for assessing asthma conditions, especially for severe cases complicated with hypoxemia and hypercapnia, which can guide treatment. Some scholars classify asthma attacks into grade III based on blood gas results. ① Grade I: pH is normal or slightly elevated, PaO2 is normal, PaCO2 is slightly low, indicating that asthma is in the early stage, with grade I hyperventilation, and bronchospasm is not severe. It can be relieved by oral or aerosol inhalation of antiasthmatic drugs; ② Grade II: pH is normal, PaO2 is slightly low, PaCO2 remains normal, indicating insufficient ventilation, more pronounced bronchospasm, and worsening condition. Intravenous antiasthmatic drugs may be added if necessary. ③ Grade III: pH decreases, PaO2 significantly decreases, PaCO2 increases, indicating severe ventilation insufficiency, bronchospasm, and severe obstruction, often occurring in status asthmaticus, requiring active treatment or intensive care.
7. Other Laboratory Tests These include inhalation of different concentrations of methacholine or histamine, exercise tests for children with suspected asthma but normal pulmonary function tests, and in vitro tests such as radioimmunoassay, enzyme-linked immunosorbent assay, histamine release test, and basophil degranulation test to detect allergens. Some reports suggest that children with asthma may have a deficiency of the trace element zinc.
Based on the medical history and typical asthma attacks, the diagnosis is generally not difficult. The first National Pediatric Respiratory Disease Academic Conference held in Chengdu in 1987 and the National Infantile Asthma Conference held in Wenzhou in 1988 proposed the following diagnostic criteria for infant asthma, childhood asthma, and allergic cough.
Infant Asthma: Clinical and adrenaline tests are scored for infants with recurrent cough attacks ≥3 times, as shown in Table 16-2.
Table 16-2 Infant Asthma Scoring Table
| Item | Score | Description |
| Sudden onset | 1 | Wheezing occurs within 12 hours of onset |
| Wheezing | 1 | |
| Shortness of breath | 2 | Intermittent phenomenon during crying or laughing |
| Asthma | 2 | Atypical 1 point |
| Itchy eyes and nose | 1 | Repeated rubbing of nose and eyes |
| Continuous sneezing | 1 | |
| History of infant eczema | 1 | |
| Family history of asthma | 1 |
Adrenaline test: 1% adrenaline 0.01ml/kg each time (or use salbutamol, terbutaline, clenbuterol, etc. for quantitative aerosol inhalation test) subcutaneous injection, asthma wheezing basically disappears after 10-15 minutes for 4 points, wheezing symptoms disappear for 3 points, wheezing symptoms decrease for 2 points, a score of 6-8 points is diagnosed as "suspected infant asthma"; a score > points is diagnosed as infant asthma.
Childhood asthma: ① Age over 3 years; ② Main symptoms and signs: including wheezing, shortness of breath or chest tightness, paroxysmal cough; wheezing sounds in the lungs, must recur ≥3 times; ③ Asthma attacks often have a certain season, time, and corresponding triggers; ④ Use of asthma medications (bronchodilators) can alleviate and relieve asthma symptoms; ⑤ After 0.5% salbutamol aerosol inhalation, forced expiratory volume in one second (FEV1) increases by more than 15%; ⑥ Often has a personal or family (first or second-degree relatives) history of allergies.
Among them, items ② and ④ are necessary conditions, items ③ and ⑥ are reference conditions. Item ⑤ is an auxiliary condition.
Allergic cough: Some asthma children have very atypical clinical manifestations, with recurrent cough as the only complaint, often misdiagnosed as "upper respiratory infection" or "bronchitis" and long-term misuse of antibiotics, but the symptoms persist. The diagnostic criteria are as follows: ① Children of any age can develop the disease, but it is more common in preschool children; ② Cough recurs for more than one month, characterized by nocturnal or early morning attacks, dry cough with little phlegm; ③ No clinical signs of infection or long-term use of antibiotics is ineffective; ④ Use of asthma medications can relieve cough attacks.
bubble_chart Treatment Measures
The treatment principle is to adopt multiple measures to relieve bronchospasm, improve pulmonary ventilation function, and control infection during acute attacks.
Treatment of Acute Attacks The treatment of acute asthma attacks mainly includes oxygen therapy, bronchodilators, and corticosteroids. The types of drugs and doses used depend on the severity of the asthma attack. The aforementioned treatment measures are effective for both immune and non-immune asthma.
Antiasthmatic drugs mainly include two categories, namely sympathomimetic amines and xanthines. Sympathomimetic amines vary according to their effects on cell receptors (α or β). Their main effect is to stimulate adenylate cyclase, increasing the conversion of intracellular adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP), thereby stabilizing the cell membrane, inhibiting the release of biological mediators, and reducing congestion and edema of the bronchial mucosa, achieving the effect of relaxing smooth muscle; xanthine drugs inhibit phosphodiesterase, preventing cAMP from being rapidly decomposed into 5'AMP, and maintaining the concentration of cAMP in cells, thereby achieving the effect of bronchodilation.
(1) Commonly used sympathomimetic amine drugs: stimulate α receptors and β1 receptor drugs, which may cause side effects such as pale complexion, headache, vomiting, palpitations, arrhythmia, and increased blood pressure after application, and have gradually been replaced by β2 receptor agonists. The latter have high selectivity for β2 receptors, and therapeutic doses can significantly dilate bronchial smooth muscle, with less effect on the heart and other aspects, but sometimes grade I nausea, vomiting, and occasionally muscle tremors and palpitations due to stimulation of skeletal muscle β2 receptors may occur. Long-term use may lead to drug resistance.
During acute attacks, β2 receptor agonist aerosols should be the first choice because they act quickly, require small doses, and have fewer side effects. Currently, commonly used dosage forms are metered dose inhalers (MDI, i.e., hand-controlled) and nebulizers, which can be used for both acute asthma attacks and maintenance therapy. When using the former, hand control and inhalation need to be synchronized, as children under 4-5 years old may have difficulty mastering it, which can often affect the efficacy. Currently, to improve efficacy, a spacer is connected to the metered dose inhaler and mouthpiece, allowing most of the drug to be inhaled through repeated breathing. Recently, powder aerosols and "disk inhalers (Rotadisk)" have been invented abroad, which not only improve the efficacy of inhalation therapy but also avoid the irritation of Freon in MDIs and air pollution. For severe asthma, nebulized inhalation (nebulizer), intraosseous, and intravenous injections can also be used.
(2) Xanthine drugs: are the most commonly used bronchodilators. The clinically used aminophylline is a complex salt of theophylline and ethylenediamine (containing 80-85% theophylline). For acute attacks, if oral administration is ineffective, it can be injected intravenously, with an initial dose of 4-5 mg/kg (loading dose), diluted with 5-10% glucose solution, and slowly injected within 30 minutes. If aminophylline treatment has already been used (within 6 hours), the dose should be halved. Maintenance doses can then be given. For children aged 1-9 years, aminophylline can be chosen for intravenous infusion at 0.6-0.9 mg/kg·h, and blood aminophylline concentration should be measured if possible, with the effective blood concentration for treating asthma being 10-20 μg/ml. Generally, the drug is administered at 4-5 mg/kg per dose, every 6-8 hours. If possible, the peak and trough blood aminophylline concentrations should be monitored to find the optimal dosing regimen. After the condition stabilizes, the concentration can be monitored every 2-3 months.
Due to the narrow therapeutic range of aminophylline and individual differences, close attention should be paid to toxic reactions during treatment. If symptoms such as nausea, vomiting, dysphoria, restlessness, or even hematemesis, tinnitus, delirium, and convulsions occur, the medication should be discontinued immediately. In cases of heart failure, liver dysfunction, fever, or concurrent use of erythromycin-like drugs, the dose should be reduced as drug excretion slows down.
⑶ Anticholinergic drugs mainly include: ① Ipratropium bromide, an isopropyl derivative of atropine, has high selectivity for bronchial smooth muscle and can block the bronchoconstriction caused by vagus nerve cholinergic fibers. It is mainly used as an aerosol inhalation, 20～80μg each time, 3～6 times a day. The efficacy in infants is better than in school-age children, and the therapeutic dose generally does not cause thickening of secretions or interfere with ciliary clearance. Some recommend the combined use of anticholinergic drugs and β2 agonists to improve the efficacy of asthma relief. ② Scopolamine has the effects of relaxing bronchial smooth muscle, inhibiting glandular secretion, improving ventilation function, and sedation. The dose is 0.01～0.02mg/kg each time, which can be intramuscularly injected or slowly intravenously dripped with glucose solution. It also has the effects of slowing heart rate and grade I blood pressure reduction, and can reduce the adverse reactions of aminophylline on the heart and blood vessels in patients with tachycardia.
⑷ α-receptor blockers: The commonly used preparation in China is phentolamine, which can dilate small blood vessels, relieve pulmonary stirred pulse spasm, increase cardiac contractility, and dilate spasmodic bronchi. It is effective in clearing pulmonary circulation and regulating the ventilation/blood flow ratio. It is often used with β-receptor agonists to improve capillary permeability and stabilize lysosomal enzymes, which not only dilates spasmodic bronchi but also eliminates airway inflammatory reactions. In the past, corticosteroids were mainly used for patients with status asthmaticus and chronic refractory asthma attacks, but in severe attacks, intravenous hydrocortisone, dexamethasone, etc., can also be used. Generally, after the condition improves, oral prednisone is used and gradually reduced for maintenance. The long-term oral use of corticosteroids can lead to adrenal cortex dysfunction, and once stopped or reduced, symptoms of adrenal cortex insufficiency or recurrence of asthma may occur. To reduce systemic side effects and enhance local airway desensitization and anti-inflammatory effects, Brown first synthesized beclomethasone dipropionate aerosol (BDA) in 1972 and used it for the prevention and treatment of asthma, achieving good efficacy. Generally, 1～2 weeks before the high season of infantile asthma, or when the weather changes suddenly, or after suffering from upper respiratory tract infection, BDA is inhaled 2～4 times a day, 1～2 puffs each time (each puff contains 50μg of BDA), and the daily inhalation dose should not exceed 400μg. Generally, there are no side effects, only local irritation in the oropharynx, so gargling is recommended after use. Occasionally, fungal infections have been reported. However, BDA is different from isoproterenol or salbutamol aerosol, its effect occurs 3 days after use. When asthma attacks acutely, only inhaling BDA is not only ineffective but may also worsen symptoms. Therefore, β-receptor agonists should be first chosen during acute attacks, and after symptoms slightly alleviate, BDA can be inhaled. For other mild, grade II, and chronic asthma children, as well as corticosteroid-dependent asthma children, BDA is a good medicine for controlling airway inflammation, reducing bronchial asthma attacks, and gradually relieving children's dependence on corticosteroids. In recent years, with the in-depth study of the inflammatory theory in the pathogenesis of asthma, BDA has received more and more attention and has gradually become one of the first-choice drugs for treating asthma.
Treatment of status asthmaticus Some people define status asthmaticus as continuous asthma attacks, ineffective after three uses of bronchodilators, clinically presenting with dyspnea, hypoxemia (or cyanosis), which should be treated urgently, otherwise it may lead to pulmonary ventilation failure and death. In 1972, Wood et al. proposed the clinical scoring criteria for status asthmaticus (Table 16-4).
Table 16-4 Wood's clinical scoring criteria
| Item | 0 points | 1 point | 2 points |
| PaO2(kPa) or cyanosis | Breathing air 9.3～11.3 | Breathing air <9.3 | Breathing 40% O2<9.3 |
| No cyanosis | Mild cyanosis | Severe cyanosis | |
| Breath sounds | Normal | Asymmetrical | Weak or absent |
| Accessory muscle use | None | Grade II | Extreme effort |
| Wheezing | None | Grade II | Significant |
| Mental status | Normal | Drowsiness or dysphoria | Unconsciousness |
A score ≥ indicates respiratory insufficiency; a score ≥ accompanied by PaCO2>8.7kPa indicates respiratory failure. Domestic experts suggest that a score ≥7 with PaCO2between 6.7～9.3kPa may be treated conservatively, while PaCO2>9.3kPa is an indication for intubation.
The treatment plan for status asthmaticus in children, as established by the 1988 National Academic Exchange Conference on Infantile Asthma, is as follows: ① Oxygen inhalation: The concentration should be 40%, with a flow rate of about 4～5ml/min, to maintain PaCO2 above 9.3kPa; ② Use of bronchodilators: a. β-agonists: 0.5% salbutamol can be used for nebulization, dose: 1～4 years 0.25ml, ～6 years 0.5ml, ～12 years, nebulize every 1～2 hours, and change to every 6 hours after the condition improves; b. Aminophylline, the initial loading dose is 4～5mg/kg, slowly intravenously injected over 20～30 minutes, the maintenance dose is 0.6～1mg/kg/h, the dose is halved for children under 1 year old. Theophylline blood concentration should be monitored, and after the condition improves, 4～5mg/kg can be intravenously injected every 6 hours. c. Intravenous infusion of salbutamol, used when the condition does not improve after nebulized salbutamol and intravenous aminophylline, the general dose is 4～5mg/kg each time, the speed is 8μg/min, the onset time is 20～30 minutes, and the maintenance time is 4～6 hours; ③ Adrenal corticosteroids: Methylprednisolone 1～2mg/kg each time or hydrocortisone 0.25～0.5mg/kg each time, every 6 hours; ④ Isoproterenol intravenous drip, only for children with asthma who are not responsive to the above treatments and do not have the conditions for intubation and mechanical ventilation. Initially, slowly drip at 0.1μg/kg﹒min, each milliliter contains 5μg, under the monitoring of electrocardiogram and blood gas, the dose can be increased every 10～15 minutes, the maximum dose should not exceed 3～4μg/kg﹒min; until PaO2 and ventilation function improve, if the heart rate exceeds 180～200 times﹒min, the dose should be reduced. Effective cases will have symptoms relieved 2 hours after treatment, at which time the dose can be gradually reduced, generally the medication is maintained for 24 hours. Some suggest that the use of α-blockers at the same time can slow down the heart rate; ⑤ Mechanical ventilation: For those with persistent dyspnea, almost no wheezing and breath sounds, consciousness disorder until unconsciousness, after inhaling 40% oxygen, cyanosis still exists, when PaCO2 exceeds 9.3kPa, assisted mechanical ventilation should be performed, muscle relaxants can be added if necessary, and the ventilator is preferably of the volume-controlled type.
Other treatments also include sedation, maintaining water and electrolyte balance, using antibiotics in case of infection, and comprehensive measures such as dispelling phlegm and strengthening the heart.
Treatment of Chronic Bronchial Asthma Children with chronic bronchial asthma have varying degrees of lung function impairment due to multiple episodes, such as lung hyperinflation, poor elastic recoil, hypoxemia, and some children may show cardiac dysfunction. The treatment principles are: first, local inhalation of β-receptor agonists, 3 to 4 times daily, and in severe cases, oral theophylline can be added (every 6 to 8 hours, 4 to 5 mg/kg per dose), or oral β-receptor agonists can also be used. In recent years, long-acting aminophylline (aminophylline sustained-release tablets, 100mg or 200mg per tablet, taken every 12 hours) and long-acting salbutamol (salbutamol sustained-release or controlled-release tablets, 4mg per dose for children, 8mg for those over 12 years old, taken every 12 hours) have been available. Additionally, after controlling asthma attacks, switching to beclomethasone dipropionate aerosol inhalation is also a measure for treating chronic asthma. Other anti-asthmatic, antitussive, resolving phlegm, and anti-inflammatory drugs are selected based on symptoms. In recent years, some scholars have suggested that asthma onset is related to immune regulation disorders, so there are also reports of using Chinese medicinals (Six-Ingredient Rehmannia Pill, Jade Screen Powder), levamisole, and other immune enhancers for treatment, achieving certain therapeutic effects. In pediatric diseases, chronic persistent episodes in the philtrum are relatively rare, and the key lies in controlling and preventing acute episodes.
The prognosis of childhood asthma is generally favorable, with a mortality rate of about 2 to 4 per 100,000. The prognosis of asthma is often related to the age of onset, the severity of the condition, the duration of the disease, and whether there is a family history of the disease. According to foreign data, 80% of children can be completely cured by adolescence, and 70% stop having attacks after the age of 10. However, some scholars believe that although these children no longer show clinical symptoms, some may still have airway hyperresponsiveness. Therefore, only when clinical symptoms disappear and respiratory function tests are completely normal can it be considered a full recovery.
The reasons for the improvement or cessation of symptoms after adolescence may be related to: ① the basic maturation of neuroendocrine function after adolescence, especially the normal function of the adrenal cortex, which helps control asthma; ② the allergens and allergic conditions present in the body improve with age and through desensitization therapy, enhancing the body's immune regulation and reducing the level of IgE; ③ improvements in environmental conditions help avoid contact with allergens; ④ with age and physical exercise, the constitution is strengthened, enhancing the body's ability to resist infections and diseases, thereby reducing and controlling asthma attacks.
Repeated episodes of bronchial asthma have a significant impact on the growth, development, daily life, and learning of affected children, and prevention should be initiated as early as possible.
Avoiding allergens and identifying triggering factors: Treatment requires a detailed understanding of the triggering factors and specifics of each episode. Attention should be paid to preventing respiratory infections, eliminating foci of infection (such as timely treatment of sinusitis, nasal polyps, tonsillitis, dental caries, etc.), and avoiding overexertion, getting caught in the rain, running, and emotional stress. Known allergens, such as contact with Mongolian snakegourd root or the use of aspirin, should be avoided and managed promptly. If possible, improving the living environment or relocating may be beneficial.
Immunotherapy: This includes non-specific immunotherapy and specific desensitization therapy. In recent years, methods such as thymosin, inactivated BCG, bronchitis vaccine, nucleic acid, measles vaccine, and placental lipopolysaccharide have been used. The goal of these treatments is to stimulate the body's immune function, enhance lymphocyte proliferation, and produce non-specific IgG, thereby improving the patient's immune function.
Another type is desensitization therapy, which is suitable for extrinsic asthma. It involves starting with a small dose of the allergen that causes the body's allergic reaction and gradually increasing the concentration, thereby reducing the body's IgE response and achieving both therapeutic and preventive effects. Desensitization therapy should generally be continued for 2-3 years, with better efficacy in children than in adults and in those allergic to a single allergen. However, due to the vast variety of allergens, such as dust, mites, Mongolian snakegourd root, and molds, which are almost ubiquitous, the role of this therapy remains controversial.
Kaman Shu solution is a recently developed immune enhancer and regulator, with sodium carboxymethyl starch as its main component. Animal experiments and clinical applications have shown that it improves cellular and humoral immune functions in children with recurrent respiratory infections and asthma, thereby enhancing the body's resistance. Dosage: 22.5% Kaman Shu solution, 7ml per dose for ages 1-4, 10ml for ages up to 7, and 15ml for ages up to 14, three times daily, for a course of 3-6 months.
Preventing viral infections: Respiratory infections, especially RSV infections, are closely related to the onset of infantile asthma, making the prevention of viral respiratory infections crucial. Currently, there are few effective antiviral drugs available, commonly used are: ① Interferon, which has broad-spectrum antiviral effects. There are reports of using interferon aerosol to prevent viral respiratory infections and prevent asthma attacks, but it is difficult to source, expensive, and side effects increase with longer treatment durations. ② Ribavirin aerosol, which has shown some efficacy in preventing and treating infectious asthma, can be administered by nasal drops or aerosol inhalation, 2-3 times daily.
Stabilizing cell membranes: By stabilizing mast cell membranes and inhibiting mast cell degranulation, the release of chemical mediators can be prevented, thereby preventing asthma attacks. ① Sodium cromoglycate is the first-choice preventive drug. This drug is not absorbed in the intestines and requires 20mg of powder to be inhaled via a spray inhaler, 3-4 times daily. It usually takes effect within 2-4 weeks, with a treatment course of 4-6 months. However, this drug does not dilate the bronchi and is ineffective for acute attacks. In some cases, inhalation of this drug may even induce bronchial asthma. ② Ketotifen, which can be taken orally, also has the effect of stabilizing mast cell membranes and antihistamine effects, suitable for all types of asthma. The dose is 0.08-0.12mg/kg/day, to be taken for at least 6-12 months. However, its bronchodilating effect is not strong, and it is now widely used to prevent asthma attacks. Side effects include drowsiness, dizziness, and fatigue, which are less common in children than in adults.
Physical exercise is extremely important for children with long-term asthma and can be carried out alongside medication. Physical exercise promotes blood circulation and metabolism, improves respiratory function, enhances muscle tone, and increases the body's adaptability to temperature and environmental changes. Participating in sports can also stimulate appetite, maintain a cheerful spirit, and improve the body's disease resistance. Additionally, establishing a regular lifestyle, treatment in accordance with local conditions, gradually increasing the amount of exercise, engaging in cold water face and foot washing exercises, and participating in swimming activities during the summer are all beneficial forms of exercise. As long as it is done under the guidance of a doctor and with certain medications, persistent physical exercise is an important measure to prevent asthma attacks and regulate the body's functional state.
Chinese medicine Chinese medicinals treatment During the interictal period, Chinese medicine advocates reinforcing healthy qi and securing the root, strengthening tonifying the spleen and replenishing qi, and kidney-tonifying methods. The traditional methods of "treating winter diseases in summer" and "treating summer diseases in winter" have been widely adopted.
Reducing mental stimulation and psychological burden on sick children Asthma is also a psychosomatic disease. Since the onset of asthma is related to the excitability of the nervous system, medical staff must inform parents to avoid the following two incorrect tendencies when dealing with asthmatic children: ① Excessive pampering and indulgence, which can lead to the gradual formation of abnormal personality traits in the child, and the disease may fluctuate with emotional changes; ② Too little concern for the sick child, even to the point of neglect and indifference, which can increase the psychological pressure on the child and be detrimental to the condition. Children often miss school due to illness, and the pressure from academic and physical exercise can be significant. If not handled correctly, it can increase their psychological burden. Therefore, for asthmatic children, under the supervision of medical staff, they should be encouraged to participate in group activities, learn self-management, keep a daily asthma diary, and enhance their confidence in overcoming the disease. Doctors should also explain in detail to parents and children (older children) the disease causes and prevention measures of asthma, and encourage parents, children, and doctors to work closely together to overcome the disease. As long as the child persists in treatment, most can reduce attacks until they are basically cured. Many children also achieve natural recovery during adolescence due to improvements in their own constitution and changes in their environment.
1. Bronchiolitis This disease is more common in infants under 1 year old, with a higher incidence in winter and spring. It also presents with dyspnea and wheezing, but the onset is slower, and bronchodilators are not significantly effective. The pathogen is respiratory syncytial virus, followed by parainfluenza virus type 3. However, bronchitis can also produce specific IgE, participating in type I hypersensitivity reactions. Since the 1970s, there have been several outbreaks in Guangxi, Wenzhou, Shanxi, and Beijing in China, but it is generally not difficult to distinguish from typical asthma.
2. Asthmatic Bronchitis This condition is more common in children aged 1 to 4 years. It starts with a clear respiratory infection and resolves as the inflammation is controlled. Clinically, wheezing can be heard, but dyspnea is not severe, and the onset and cessation are not sudden. The course lasts about a week. As the child grows older and the frequency of respiratory infections decreases, the frequency of wheezing also decreases, and the severity lessens. However, in recent years, many domestic scholars believe that asthmatic bronchitis is essentially asthma.
3. Bronchial Lymph Subcutaneous Node This disease can cause persistent cough and asthma-like expiratory dyspnea, but there is no significant paroxysmal phenomenon. The subcutaneous node tuberculin test is positive. Chest X-ray shows nodular dense shadows at the hilum, with surrounding infiltration. In some cases, enlarged lymph nodes can compress the trachea or undergo caseous changes, and when they rupture into the trachea, they can cause severe asthma symptoms and dyspnea.
4. Bronchiectasis During secondary infections, increased secretions and blockages in the bronchiectatic areas can also cause asthma-like dyspnea and wheezing. Generally, it can be differentiated based on a history of severe lung infections, recurrent atelectasis, and expectoration of large amounts of purulent sputum. If necessary, chest X-ray, bronchography, or CT scans can be used for diagnosis.
5. Respiratory Tract Foreign Body There is a history of sudden severe coughing after inhaling a foreign body, followed by persistent asthma-like dyspnea, which worsens or improves with changes in body position. However, since foreign bodies usually block the trachea or larger bronchi, the main manifestation is inspiratory dyspnea, whereas asthma presents with expiratory dyspnea. Additionally, children with respiratory tract foreign bodies do not have a history of recurrent wheezing. If the foreign body is in one side, wheezing and other signs are limited to the affected side, and sometimes a special flapping sound can be heard, which is significantly different from the bilateral signs of asthma. X-ray and bronchoscopy can not only confirm the diagnosis but also remove the foreign body.
6. Tropical Eosinophilia Some cases have clinical manifestations similar to asthma. The main distinguishing feature is the presence of a large number of eosinophils in the sputum, with peripheral blood eosinophil counts exceeding 10% or more. Chest X-ray shows cloud-like shadows that are migratory. The child has a clear history of Chinese Taxillus Herb infection and responds to treatment with drugs like diethylcarbamazine and chloroquine.
7. Cardiac Asthma This is more common in the elderly, mostly caused by left heart failure. Common predisposing conditions include hypertension, coronary artery disease, and mitral stenosis. In children, rheumatic heart disease causing mitral stenosis and insufficiency can also lead to left heart failure. The clinical presentation during an attack is similar to an acute asthma attack, often occurring paroxysmally at night. The patient cannot lie flat and often coughs up large amounts of thin or frothy bloody sputum. Fine moist rales can be heard at the lung bases, the heart is enlarged to the left, and there are valvular murmurs. In severe cases, gallop rhythm and arrhythmias may occur, making differentiation generally not difficult.
In addition, pediatric bronchial asthma also needs to be differentiated from congenital laryngeal stridor, retropharyngeal abscess, and gastroesophageal reflux.
