Bronchial asthma, asthma is a reversible, obstructive respiratory disease that manifests recurrent episodes of cough, wheezing and dyspnea with airway hyperresponsiveness. Asthma is a common chronic respiratory disease that seriously endangers the health of children, with a high incidence and often manifests itself as a chronic course of recurrent attacks, which seriously affects the learning, life and activities of children and adolescents, and affects the growth and development of children and adolescents. Many children with asthma eventually develop into adults with asthma due to untimely treatment or improper treatment and persist, with impaired lung function, and some patients even completely lose physical Severe asthma attacks can be fatal if not treated promptly and effectively.
The definition, etiology, pathogenesis, immunology, pathophysiology and principles of diagnosis and treatment of asthma are basically similar in children and adults, but there are still differences in some aspects of asthma in children and adults. Children with asthma are in the process of continuous intellectual, physical, psychological and immune system growth and development, especially in the aspects of immunology and pathophysiology, children with asthma have their own special aspects.
I. Causes of morbidity
The prevalence of asthma around the world varies between 0.1% and 32%, with a variation of nearly 300 times, and its causes may be related to genetics, age, geographic location, climate, environment, race, industrialization, urbanization, interior decoration, standard of living, dietary habits, etc.
The factors that trigger bronchial asthma are multiple and common factors include the following.
1.Allergy (10%)
Allergic substances are roughly divided into three categories.
(1) pathogens causing infections and their toxins, pediatric asthma attacks are often closely related to respiratory infections, more than 95% of infant asthma is due to respiratory infections, the main pathogens are respiratory viruses, such as syncytial virus (RSV), adenovirus, influenza, parainfluenza virus, etc. Syncytial virus infection can occur due to the occurrence of specific IgE-mediated type I metaplasia and wheezing, others such as sinusitis Other local infections such as sinusitis, tonsillitis, dental caries, etc. may also be triggering factors.
(2) Inhalants: usually inhaled from the respiratory tract, domestic application of skin tests show that the most important allergens causing asthma are dust mites, house dust, mold, polyvalent pollen (Artemisia, ragweed), feathers, etc. There are also reports of contact with silkworms to develop asthma, especially mites as inhalation allergens, occupy an important position in respiratory allergic diseases, childhood allergy to mites is more than adults, spring and autumn is the most suitable season for the survival of mites. In addition, asthma attacks caused by inhalation allergens are often related to the season, region and living environment, and the symptoms can be reduced or disappeared once the exposure is stopped.
(3) Food: mainly heterogeneous proteins, such as milk, eggs, fish and shrimp, spices, etc. Food allergy is common in infancy and gradually decreases after 4-5 years of age.
(2) Non-specific irritants (20%)
Such as dust, smoke (including cigarettes and mosquito incense), odor (industrial irritant gas, cooking oil smell and oil knee taste), etc., these substances are non-antigenic substances, can stimulate the bronchial mucosa sensory nerve endings and vagus nerve, causing reflex cough and bronchospasm, long-term persistence can lead to airway hyperresponsiveness, sometimes inhalation of cold air can also induce bronchospasm, some think that air pollution is becoming more and more serious. may also be one of the important reasons for the increased prevalence of bronchial asthma.
3.Climate factors (5%)
Children are sensitive to climate change, such as the sudden cold temperature or lower air pressure, can often trigger an asthma attack, therefore, generally in spring and autumn, the onset of children increased significantly.
4.Psychological factors(5%)
Although the mental factors in children’s asthma cause asthma attack is not as obvious as adults, but children with asthma are often affected by emotions, such as crying and laughing or anger and fear can cause asthma attacks, some scholars have proved that when emotional or other mental activity disorders are often accompanied by vagal excitation.
5, genetic factors (10%)
Asthma is hereditary and the prevalence of family and personal history of allergies, such as asthma, infantile eczema, urticaria, allergic rhinitis, etc., is higher than that of the general population.
6.Exercise (40%)
Foreign reports about 90% of children with asthma, exercise can often stimulate asthma, also known as exercise asthma (EIA), mostly in older children, strenuous sustained (5-10 minutes or more) after running is most likely to trigger asthma, the mechanism of its occurrence is a hundred immune.
7.Drugs (10%)
Drug-induced asthma is also more common, and there are two main types of drugs.
(1) a class of aspirin and similar antipyretic and analgesic drugs, can cause the so-called endogenous asthma, such as accompanied by sinusitis and nasal polyps, is called aspirin triad, other similar drugs are anti-inflammatory pain, methotrexate, etc. The mechanism of asthma caused by aspirin may be the inhibition of prostaglandin synthesis, resulting in a decrease in cAMP content, the release of chemical mediators cause asthma, this type of asthma often decreases with age. This type of asthma often decreases with age, and the onset of asthma after puberty is seen to be rare.
(2) Another class of drugs is the role of the heart drugs, such as the heart, such as the heart can block the β receptors and cause asthma, in addition to many spray inhalants can also stimulate the throat reflexive cause bronchospasm, such as sodium cromoglycate, sputum easy net, etc. Other such as iodine oil imaging, sulfa drug allergy can also often trigger asthma attacks.
Second, the pathogenesis
Bronchial asthma is a complex disease caused by a variety of factors, the pathogenesis is still unknown, the following three mechanisms are recognized.
1, type I allergic reaction and IgE synthesis regulation disorder
After the antigen (allergen) enters the body for the first time, it acts on B lymphocytes, which become plasma cells and produce IgE, which is adsorbed on mast cells or basophils, and its Fc segment binds to the specific receptor on the surface of cell membrane, so that IgE is firmly adsorbed on the cell membrane, causing the body to be in a sensitized state. These bioactive substances can lead to capillary dilation, increased permeability, smooth muscle spasm and glandular hypersecretion, which cause bronchial asthma.
In recent years, many studies have shown that the increase of IgE is also related to cellular immune dysfunction, and a large number of studies have proved that T cells not only have quantitative changes, but also may have functional defects, in addition, high IgE may also be related to delayed maturation of suppressor T cells.
2. Airway inflammatory changes
Biopsies of animal models of asthma and asthmatic patients by fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) techniques demonstrated that airway tissues showed varying degrees of inflammatory changes.
3.Airway hyperresponsiveness
Airway hyperresponsiveness is the abnormal increase of airway reactivity to various specific or non-specific stimuli. The severity of the disease in children with croup is parallel, and these in turn are associated with neuromodulation disorders, especially phytonadic dysfunction.
It is known that bronchial smooth muscle is under dual sympathetic and parasympathetic innervation and is dynamically balanced under brain-hypothalamus-pituitary regulation, and that in normal subjects bronchial smooth muscle tone depends on the excitatory state of cholinergic receptors, whereas in children with asthma it does not, with increased parasympathetic tone, enhanced α-adrenergic nerve activity and hypo- or partially blocked β-adrenergic nerve function, due to these abnormalities hyperreactivity of the airways in children with asthma is one of the pathophysiological bases of asthma attacks.
The main pathological changes in asthma are bronchial smooth muscle spasm, inflammatory cell infiltration, thickening of the upper basement membrane and airway mucosa edema, epithelial shedding and mixed cell debris, increased mucus secretion, mucosal cilia dysfunction, which in turn causes bronchial mucosal hypertrophy and endobronchial mucus embolism, and the result of the above pathological changes causes narrowing of the airway lumen, resulting in increased airway resistance and the appearance of asthma.
Diagnosis
Detailed medical history (including the trigger, the number of attacks, the duration of each attack, the time pattern and seasonality of attacks, previous treatment measures and response to treatment, etc.), the family history of allergy, combined with the exhalation dyspnea, prolonged expiratory phase of lung auscultation, and expiratory phase croup sounds during the attack, the diagnosis is not difficult. Pulmonary ventilation function tests, airway reactivity measurements or bronchodilatation tests can help to diagnose asthma and determine its severity.
In addition, skin allergen test can also assist in diagnosis.
1.Diagnostic criteria of asthma in children
(1) Diagnostic criteria of asthma in infants and children.
① Age <3 years, asthma attacks ≥3 times.
(ii) Exhalation phase croup is heard in both lungs during the attack and the expiratory phase is prolonged.
③ having atopic constitution, such as allergic eczema, allergic rhinitis, etc.
④ parents with a history of allergy such as asthma.
⑤ Excluding other diseases that cause wheezing.
If you have ①, ②, ⑤ above, you can diagnose asthma. If you have 2 episodes of wheezing and ②, ⑤, you can diagnose suspected asthma or wheezing bronchitis, and if you have ③ and/or ④ at the same time, you can consider giving therapeutic diagnosis of asthma.
(2) Diagnostic criteria for asthma in children.
(i) Age ≥ 3 years, with recurrent episodes of wheezing (or traceable to some allergen or irritant).
(ii) wheezing sounds predominantly in the expiratory phase are heard in both lungs during the attack, with prolonged expiratory phase.
(iii) significant efficacy of bronchodilators.
(④Excluding other diseases causing wheezing, chest tightness and cough.
(3) Diagnostic criteria for cough variant asthma (CVA).
(① persistent or recurrent cough attacks >1 month, often at night and/or early in the morning, with little sputum, associated with smelling irritating odors, climate change, exercise, etc.
(ii) No clinical signs of infection, or ineffective with longer-term antibiotic therapy.
③ personal history of allergy or family history of allergy, positive allergen skin test may assist in the diagnosis.
④ the presence of airway hyperresponsiveness (positive bronchial excitation test), positive bronchodilator test or PEF daily or weekly variability ≥ 15%.
⑤ Bronchodilators and/or glucocorticoid therapy can bring about relief of coughing attacks (basic diagnostic condition).
2. Staging and severity grading of asthma Staging of asthma.
The course of asthma can be divided into acute exacerbation and remission. Acute exacerbation of asthma refers to the sudden onset or aggravation of symptoms such as shortness of breath, cough and chest tightness, often with dyspnea and wheezing, accompanied by reduced expiratory flow; remission refers to the disappearance of treated or untreated symptoms and signs, and the return of pulmonary function to the level before the acute exacerbation, which is maintained for more than 4 weeks.
3.Evaluation of asthma condition: The evaluation of the condition of asthma patients should be divided into 2 parts.
(1) Total evaluation of non-acute exacerbation condition: Many asthma patients always have symptoms (wheezing, cough, chest tightness) at different frequencies and/or degrees for a considerable period of time even though they do not have acute exacerbation at the time of consultation, so it is necessary to make a total evaluation of their condition based on the frequency of exacerbation, severity, medication needed and lung function for a period of time before consultation.
When the patient is already in standardized treatment, the severity of asthma should be graded according to the current clinical manifestations and the level of the current daily treatment regimen.
(2) Evaluation of the severity of acute asthma attack: making a correct assessment of the severity of acute asthma attack is the basis for giving timely and effective treatment, and the recognition of severe asthma is the key to avoiding death caused by asthma.
IV. Differential diagnosis
Since the clinical manifestations of asthma are not unique to asthma, it is necessary to exclude wheezing, chest tightness and cough caused by other diseases while establishing the diagnosis.
1, cardiogenic asthma: cardiogenic asthma is commonly associated with left heart failure, and the symptoms during the attack are similar to those of asthma, but cardiogenic asthma mostly has a history and signs of rheumatic heart disease and congenital heart disease, paroxysmal cough, often coughing up pink foamy sputum, extensive vesicular sounds and rales can be heard in both lungs, the left heart border is enlarged, the heart rate is increased, the apical part of the heart can be heard in gallop rhythm, and the enlarged heart and pulmonary stasis signs can be seen on chest X-ray examination If it is difficult to distinguish, nebulized inhalation of selective β2 agonists or injection of small doses of aminophylline can be used to relieve symptoms after further examination.
2, pulmonary tuberculosis: can be manifested as recurrent cough, cough, shortness of breath, such as airway endothelial tuberculosis can appear obvious shortness of breath, need to be distinguished from bronchial asthma, the main differentiation points are: TB exposure history; TB chronic toxicity symptoms; positive PPD test; negative bronchial excitation test or PEF variability <15%; sputum smear to find antacid bacilli, sputum TB-PCR positive, chest X-ray, chest CT examination, if necessary Fibroscopy can be performed when necessary to clarify the diagnosis.
3, capillary bronchitis: mostly caused by respiratory syncytial virus, mostly seen in infants and children under 3 years of age, especially under 6 months of age, no previous history of recurrent episodes, this time the onset of acute, first with symptoms of upper respiratory tract infection, gradually appearing wheezing, expiratory dyspnea, the main signs: prolonged expiration, expiratory phase wheezing sound and fine wet stalls good to court pattern quasi-saddle smack wrestling shuttlecock 2 receptor agonists and systemic use of hormone efficacy is inaccurate The diagnosis can be confirmed by viral pathogenetic testing.
4, Mycoplasma pneumoniae pneumonia: lung inflammation caused by Mycoplasma pneumoniae, the main clinical manifestations of irritant dry cough, generally no significant dyspnea, symptoms can continue for 2-3 months, mainly with CVA, the main differentiation point: no previous history of recurrent cough, shortness of breath, this time often with nasal congestion, runny nose, fever, cough and other respiratory tract infection symptoms, and then the cough is prolonged, chest X-ray can be seen patchy or Cloudy shadows, which can be wandering, positive condensation set test ≥1/64 or positive antibodies to Mycoplasma pneumoniae, and effective treatment with macrolide antibiotics.
5, airway foreign body: no previous history of recurrent coughing and wheezing, before the onset of the disease, there is often a history of choking and coughing during the process of eating or clear foreign body aspiration, physical examination is often asymmetric respiratory sounds, reduced breath sounds on the sick side, reduced tactile fibrillation and local croup and other signs, chest X-ray, chest CT can assist in the diagnosis, fibrinoscopy can clarify the diagnosis and foreign body removal at the same time.
Gastro-oesophageal reflux (GOR): GOR is an episodic or persistent cough caused by stimulation of the receptors in the lower esophagus due to the reflux of gastric contents into the esophagus, and GOR can be the only or main cause of chronic cough. PEF variability is <15%, anti-asthma treatment is ineffective, 24h esophageal pH monitoring shows Demeester's score of esophageal electrodes ≥14.72, the probability of symptom correlation between reflux and cough is ≥95%, and anti-reflux treatment is effective to help the diagnosis.
7, postnasal drip syndrome (PNDs): can manifest as episodic or persistent cough, is one of the common causes of chronic cough, should be differentiated from CVA, PNDs often have a history of rhinitis, sinusitis, a sense of postnasal drip and/or mucus adhesion to the posterior pharyngeal wall, examination reveals mucus adhesion to the posterior pharyngeal wall, cobblestone-like view, sinus film or sinus CT in sinusitis can be seen as sinus mucosal thickening >6 mm or Sinus cavity blurred or with liquid flat, cough symptoms relieved after treatment (such as nasal inhalation of glucocorticoids, nasal vasoconstrictors, sinusitis with additional antibiotics).
8, eosinophilic bronchitis (EB): it is not clear whether EB is a separate disease or an early manifestation of asthma, its main clinical manifestations are chronic cough, no special findings on chest X-ray, normal pulmonary ventilation function test, negative bronchial excitation test, normal PEF variability, eosinophils > 3% in induced sputum, and effective oral or inhaled corticosteroid treatment can help the diagnosis.
9, allergic alveolitis: is due to inhalation of organic dust and other allergens caused by the granulomatous inflammatory disease of the lung, can be manifested as recurrent cough, dyspnea, etc., chest X-ray examination is not specific, mainly manifested by infiltrative changes in both lower lungs, decreased pulmonary diffusion function, negative bronchial excitation test or diastolic test, normal PEF variability, no eosinophil and IgE increase, special environment or A history of occupational exposure and positive serum antibodies specific for the corresponding allergens may help in the diagnosis.
10, diffuse bronchiectasis: is a diffuse disease mainly involving respiratory bronchi, can be caused by inhalation injury (toxic gases, smoke, mineral particles, etc.), infection, drugs, etc. Some patients are idiopathic, clinically manifested as cough, coughing, wheezing, shortness of breath, symptoms are often more persistent, extensive croup and twanging sounds in both lungs, negative bronchodilator test or PEF variability < 15%, the effect of antiasthmatic therapy is not effective. The effect of asthma treatment is inaccurate.
11, hysteria (hysteria): is a functional disease caused by temporary dysfunction of the cerebral cortex, often with “hysterical” character (strong and variable emotions, self-centered, strong desire for expression, rich fantasy, exaggerated speech and behavior, often with dramatic colors), women are common, with a variety of clinical manifestations, including mental and (or The clinical manifestations are varied, including mental and/or physical symptoms, with sudden onset and stop, and may be manifested as episodes of “shortness of breath” or “shortness of breath”, often after mental stimulation. Bronchial excitation test negative or PEF variability <15%, can be relieved by suggestive treatment.
12, bronchiectasis: in the presence of secondary infection, increased secretion and blockage at the bronchiectasis can also appear asthma-like dyspnea and hear croup, which can generally be differentiated based on the history of previous severe lung infection, recurrent pulmonary atelectasis, and copious pus-forming sputum, and can be diagnosed by chest X-ray and bronchography or CT examination if necessary.
The diagnosis of pediatric asthma generally does not require special laboratory tests, but it is necessary to further distinguish exogenous, endogenous or mixed asthma and to further understand its etiology and pathogenesis, as well as to assess the efficacy and evaluate the prognosis, so some laboratory tests are necessary for targeting.
1.Sensitive eosinophilometer
Most children with allergic rhinitis and asthma have an eosinophil count of more than 300×106L (300/mm3) in the blood, and eosinophilia, Kussman’s spirochetes and Charcot’s crystals can also be found in the sputum.
2.Blood routine
Erythrocytes, hemoglobin, total leukocytes and neutrophils are generally normal, but the total leukocyte count can increase after the application of beta-agonists, and both increase if combined with bacterial infection.
3. Chest X-ray examination
Most of the children in remission are normal, and most of them may show simple hyperinflation or increased vascular shadows in the hilum during the exacerbation period; when there is co-infection, pulmonary infiltrates may appear, and there may be different images when other complications occur, but chest X-ray helps to exclude other causes of asthma.
4.Skin allergens examination
The purpose of allergen examination is to understand the factors of asthma and to select specific desensitization therapy for children with asthma.
(1) patch test: used to identify allergens for exogenous contact dermatitis.
(2) Scratch test: mainly used to detect allergens for rapid reactions, a drop of testing agent on the test site, and then scratch, the depth of the scratch to not bleed, 20 minutes later to observe the reaction, a positive reaction manifested as redness and wind, the advantage of this method is safe, does not cause a violent reaction, but the disadvantage is not as sensitive as the intradermal test.
(3) intradermal test: higher sensitivity, easy to operate, does not require special equipment, is the most commonly used method of specific test, generally used to observe the rapid reaction, can also observe the delayed reaction, intradermal test injection of allergen infusion amount of 0.01-0.02ml, the general concentration of infusion with 1:100 (W/V), but the pollen class more with 1:1000-1:10000 concentration.
The purpose of the skin test is to clarify the allergens causing asthma, so the use of sympathomimetic, antihistamine, theophylline and corticosteroid drugs should be stopped 24-48 hours before the skin test to avoid interference with the results.
5.Pulmonary function test
Pulmonary function tests are important for estimating the severity of asthma and judging the efficacy of asthma, and generally include lung volume, pulmonary ventilation, diffusion function, flow-volume diagram and respiratory mechanics test. More important changes are changes in respiratory flow rate, as evidenced by changes in exertional lung volume (FVC), a lesser exertional expiratory flow rate (FEF25-75%) and maximum expiratory flow rate (PF).
It is recommended to measure the maximum expiratory flow rate (PEFR) only with the miniature type flow rate to monitor the change of asthmatic children’s condition at any time, the method is to take the standing position of the examined person, hold the peak flow rate instrument in the right hand, take a deep breath immediately the instrument bite mouth wheeze into the mouth, the mouth lips should contain the mouthpiece tightly, not in the leakage of air, exhale the air with the maximum force and the fastest speed, repeat 3-4 times, choose its highest value to record the evaluation, when checking, the child in During the test, the child should not hold his breath between inhalation and exhalation, which should be repeatedly demonstrated to the child before the test, while the height should be measured and then compared with the standard value of normal children in the region, if it is lower than normal and the value can be increased by 15% by inhalation of bronchodilators such as albuterol aerosol, it has diagnostic significance. The most important feature is that it can be carried around with the child, so that parents and children can monitor their own condition, record it in the asthma diary and adjust the treatment plan to achieve the purpose of controlling asthma attacks for a longer period of time, but in critically ill children, the test is often not suitable for repeated testing because of systemic failure or a rapid decrease in airway ventilation.
6.Blood gas analysis
Blood gas analysis is an important laboratory test to measure asthma, especially in severe cases of combined hypoxemia and hypercapnia, and can be used to guide treatment.
(1) Mild: normal or slightly high pH, normal PaO2 and slightly low PaCO2, suggesting that asthma is at an early stage, with mild hyperventilation and less severe bronchospasm, which can be relieved by oral or aerosol inhalation of asthma calming drugs.
(2) Moderate: normal pH, low PaO2 and normal PaCO2, suggesting that the patient is hyperventilating, with more pronounced bronchospasm, and the condition is getting worse, and intravenous asthma medication can be added if necessary.
(3) Severe: lower pH, significantly lower PaO2 and higher PaCO2 suggest severe hyperventilation, bronchospasm and severe obstruction, mostly occurring in the persistent state of asthma, requiring active treatment or supervised resuscitation.
7.Other laboratory tests
In vitro tests such as radioimmunosorbent assay, enzyme-linked immunosorbent assay, histamine release assay, basophil degranulation assay, etc. are used to detect allergens, and zinc deficiency has been reported in children with asthma.