Asthma (Asthma) is a heterogeneous disease characterized by chronic airway inflammation and airway hyperresponsiveness. Allergic asthma (allergic asthma) is the most common phenotype of asthma, accounting for more than 50% of adult asthma, and even more than 80% of children's asthma. Patients often present with symptoms such as recurrent wheezing, shortness of breath, chest tightness, or coughing.
Epidemiology
Worldwide, 1 to 18 out of every 100 people suffer from asthma. In my country, about 4 to 5 people per 100 adults suffer from asthma, but there is no authoritative report on the incidence of allergic asthma.
Basic cause
The pathogenesis of allergic asthma is complex, influenced by both heredity and environment. After the patient inhales a certain allergen for the first time, the immune system in the body is activated to make B lymphocytes produce specific IgE, which binds to IgE receptors on the surface of mast cells and basophils.
When exposed to the allergen again, the allergen binds to specific IgE, causing the above-mentioned cells to synthesize and release inflammatory mediators, resulting in airway smooth muscle contraction, increased mucus secretion, and inflammatory cell infiltration, resulting in clinical symptoms of asthma.
Predisposing factors
Common allergens include indoor allergens (dust mites, house pets, cockroaches), outdoor allergens (pollen, grass pollen), occupational allergens (paints, reactive dyes), food (fish, shrimp, egg drugs, milk), medications (aspirin, antibiotics), etc.
Symptom
The clinical symptoms of allergic asthma and non-allergic asthma are basically similar. The aura symptoms may include sneezing, runny nose, coughing, etc. The typical symptoms are recurrent panting and shortness of breath, with or without chest tightness or coughing, a large amount of frothy sputum, cyanosis, presenting status asthmaticus.
Typical symptoms
Before the attack: There are aura symptoms before the attack of allergic asthma, such as sneezing, runny nose, cough, chest tightness, etc. If not treated in time, an asthma attack may occur.
Onset: Expiratory dyspnea with wheezing, which may be accompanied by shortness of breath, chest tightness, or cough.
Severe cases: Severe cases may be forced to sit or breathe orthopnea, cough dryly or cough up a large amount of white foamy sputum, and even appear blue and purple.
Accompanying symptoms
May be accompanied by expectoration, and occasionally chest pain.
Seek medical attention
When symptoms such as wheezing, shortness of breath, with or without chest tightness or coughing occur, you should seek medical attention in time.
Diagnostic criteria
It meets the diagnostic criteria of the Global Initiative for Asthma (GINA) and my country's "Guidelines for the Diagnosis and Treatment of Bronchial Asthma", that is, there are variable symptoms such as wheezing, shortness of breath, chest tightness, and coughing, and there is objective evidence of variable airflow limitation.
Exposure to allergens can trigger or worsen symptoms.
Allergen skin prick test or serum-specific IgE test positive for at least one allergen.
Medical department
Respiratory medicine, severe patients should go to the emergency department for treatment.
Doctor's checkup
Auscultation of the lungs usually reveals scattered or diffuse wheezing sounds when the patient breathes, but if no wheezing sounds are heard, asthma cannot be ruled out, because in very severe asthma attacks, the wheezing sounds weaken or even disappear completely.
Peripheral blood eosinophil count
An increase in peripheral blood eosinophil count > 3% or 300 cells/µL indicates an asthmatic phenotype with increased eosinophils, and can also be used as one of the indicators to judge whether anti-inflammatory treatment is effective.
Induced sputum eosinophil count
Increased eosinophil count in induced sputum of asthmatic patients (≥3%) can be judged as eosinophilic inflammation and can predict the effect of glucocorticoid therapy.
Exhaled Nitric Oxide (FeNO)
FeNO increases when asthma is not controlled and decreases after glucocorticoid treatment, which can be used as an index to evaluate airway inflammation and asthma control level, and can also be used to judge the effect of inhaled corticosteroid therapy.
Pulmonary function tests
bronchodilation test
Used to measure reversible changes in the airway. Diastolic test diagnostic criteria are to meet one of the following:
After inhaling bronchodilators for 15 to 20 minutes, FEV 1 increased by >12% compared with before administration, and its absolute value increased by >200ml.
Peak expiratory flow (PEF) increased by 60L/min or 20% compared with before treatment.
special inspection
Allergen Testing
The types of allergens to be checked should be determined according to age, positive family history and symptom characteristics. Allergen detection is an important method to distinguish allergic asthma from non-allergic asthma, including in vivo test and in vitro test. In vitro test mainly detects peripheral blood total IgE and specific IgE. In vivo test includes skin prick test and intradermal test .
Differential diagnosis
This disease has similarities with dyspnea caused by left heart failure, chronic obstructive pulmonary disease, upper airway obstructive disease, non-allergic asthma and other diseases. Doctors will conduct detailed examinations from multiple aspects to judge.
Dyspnea due to left heart failure
The symptoms of this disease are similar to those of severe asthma, but patients with left heart failure often have a history of hypertension, heart disease, paroxysmal, orthopnea, and severe cases may be accompanied by coughing pink foamy sputum, wheezing or extensive wetness. Rale.
Imaging examination may show pulmonary congestion, pulmonary edema, and enlarged heart shadow, which can be differentiated from allergic asthma without obvious relief after taking bronchodilators.
Chronic obstructive pulmonary disease
It is more common in middle-aged and elderly people. Most of them have a medical history of long-term smoking or exposure to harmful gases and dust. They have wheezing, exertional dyspnea, and dry and wet lungs coexist. Imaging examination shows increased lung markings. Asthma phase identification.
Upper airway obstructive disease
There may be a history of foreign body inhalation, inspiratory dyspnea, and inspiratory wheezing. Imaging examinations may show airway stenosis, which cannot be significantly relieved by bronchodilators, which can be differentiated from allergic asthma.
Treatment
It is the most effective way to prevent and treat allergic asthma by searching for allergens as much as possible and keeping patients out of contact with these risk factors for a long time. When a patient has an acute attack, the airway spasm should be relieved as soon as possible, the hypoxemia should be corrected, and the lung function should be restored.
Acute treatment
The goals of treatment for acute attacks are to relieve airway spasm as soon as possible, correct hypoxemia, restore lung function, and prevent further deterioration or recurrence.
General treatment
Instruct patients to use inhalation devices correctly and take medication regularly, teach patients the relevant knowledge and precautions of allergic asthma, and guide patients in self-management and self-monitoring of allergic asthma.
Medical treatement
Due to large individual differences, there is no absolute best, fastest, or most effective medication. Except for commonly used over-the-counter drugs, you should choose the most appropriate drug based on your personal situation under the guidance of a doctor.
Therapeutic drugs are divided into controlling drugs and relieving drugs. Controller drugs are drugs that require long-term use to maintain clinical control of asthma, including inhaled glucocorticoids, leukotriene regulators, sustained-release theophylline, cromolyn sodium, and anti-IgE monoclonal antibodies (such as omalizumab); Relief medications are on-demand medications used to relieve asthma symptoms and include short-acting inhaled anticholinergics, short-acting theophylline, and systemic corticosteroids. Inhaled drugs are the first choice for the treatment of allergic asthma.
Glucocorticoids
It is currently the most effective drug for controlling asthma and can effectively inhibit airway inflammation. There are three ways: inhalation, oral administration, and intravenous administration.
Beta 2 agonist
Can dilate bronchi and relieve asthma symptoms. There are many such drugs, which can be divided into short-acting and long-acting β 2 -receptor agonists.
short-acting beta 2 agonists
For example, salbutamol and terbutaline are generally administered by inhalation and oral administration, and injection administration is not recommended. Inhalation administration includes aerosol, solution, etc. It is the drug of choice for relieving mild to moderate acute symptoms of asthma. Adverse reactions include skeletal muscle tremor, hypokalemia, etc.; oral administration is more convenient, but heart palpitations, skeletal Adverse reactions such as muscle tremors are more obvious than when inhaled.
Long-acting beta2 - agonist (LABA)
For example, salmeterol, formoterol, etc., can last for more than 12 hours, but they cannot be used alone for the treatment of asthma.
Anti-IgE therapy
Recombinant humanized anti-IgE monoclonal antibodies such as omalizumab were the first targeted therapy in the field of asthma. Omalizumab specifically binds to a specific region of IgE to form a heterotrimer-based complex, reduces the level of free IgE, and inhibits the high level of IgE on the surface of effector cells (such as mast cells and basophils). The affinity FcεRI binding reduces the activation of these inflammatory cells and the release of inflammatory mediators, thereby blocking the inflammatory cascade reaction that induces allergic asthma.
Omalizumab is an effective drug for the treatment of allergic asthma, which can significantly improve the symptom control of allergic asthma, reduce asthma exacerbations, emergency room and hospitalization rates, and can also reduce inhaled corticosteroids (ICS), oral corticosteroids and Use of emergency medicine.
Omalizumab, which was approved by the State Food and Drug Administration of China in 2019, can be used for moderate to severe persistent allergic asthma that cannot be effectively controlled after ICS/LABA treatment for 6 years and older. After treatment with omalizumab, patients cannot stop systemic glucocorticoids or ICS abruptly immediately, and they need to follow the principles of asthma treatment and assess the level of control to decide whether to downgrade the treatment. The overall safety profile of omalizumab was good.
Allergen-specific immunotherapy (AIT)
It means that on the basis of identifying the main allergen, let the patient repeatedly contact, gradually increase the dose of allergen extract (standardized allergen preparation), so that the immune system can develop tolerance to this type of allergen, thereby reducing or Treatments to control allergy symptoms.
As a "causal treatment", the World Health Organization calls it "the only" therapy that can block or reverse the natural process of allergic diseases. Intermediate curative effect), long-term curative effect (continuous curative effect after the course of treatment) and preventive curative effect (prevent rhinitis from developing to asthma, and prevent new allergens from appearing).
Currently, less than 10% of people with allergic rhinitis or asthma receive AIT worldwide. The administration methods of AIT include subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT). In view of adverse effects and risk management, SCIT must be performed in a certified treatment center by highly trained physicians and nurses.
Leukotriene modulator
It has anti-inflammatory and relaxing bronchial smooth muscle effects. Adverse reactions are usually mild, mainly gastrointestinal symptoms, and a few have rash, angioedema, and elevated transaminases, which can return to normal after stopping the drug.
Theophylline
It has bronchial and airway anti-inflammatory effects, and is currently one of the effective drugs for the treatment of asthma. The main adverse reactions of theophylline include nausea, vomiting, cardiac arrhythmia, blood pressure drop and polyuria, which can occasionally excite the respiratory center, and severe cases can cause convulsions and even death.
Anticholinergic drugs
It has the effect of dilating bronchus and reducing mucus secretion, and is divided into short-acting inhaled anticholinergic drugs and long-acting inhaled anticholinergic drugs. A small number of patients may have adverse reactions such as bitter mouth or dry mouth after the use of anticholinergic drugs.
Surgical treatment
Bronchial thermoplasty (bronchialthermoplasty, BT) is a radiofrequency ablation of airway smooth muscle through a bronchoscope to reduce bronchoconstriction and airway hyperresponsiveness. For severe uncontrolled allergic asthma, bronchial thermoplasty is an option, but the benefits and risks need to be fully evaluated.
Asthma cannot be cured, let alone "self-healing", but it can be completely controlled and will not recur. Patients with allergic asthma have a high control rate after long-term standardized treatment. Mild patients are easy to control, but severe patients or those with other allergic diseases are not easy to control. If it recurs for a long time, it can develop into chronic obstructive pulmonary disease and chronic cor pulmonale.
Prevention
According to individual conditions, guide patients to effectively control various factors that can induce allergic asthma attacks:
Avoid foods that cause allergies;
Avoid strong mental stimulation and strenuous exercise;
Avoid continuous shouting and other hyperventilation actions;
Do not keep pets, avoid exposure to irritating gases and prevent respiratory infections;
Wear a scarf or mask to avoid cold air stimulation;
During the remission period, physical exercise, cold-resistant exercise and endurance training should be strengthened to enhance physical fitness. Avoid indoor mold growth as exposure to mold can cause asthma attacks.
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