cough asthma
Introduction
Introduction to cough asthma Cough type asthma (coughtype asthma), also known as cough variant asthma, is a type of asthma with chronic cough as the primary or only clinical manifestation. When bronchial asthma begins to develop, about 5% to 6% are persistent coughs, mainly in the night or in the early morning, often irritating cough, which is often misdiagnosed as bronchitis. In recent years, this problem has attracted the attention of many scholars at home and abroad, and found that among the single causes of chronic cough, asthma accounts for 24%, ranking second, while 28% of asthma patients have cough as the only clinical symptom. basic knowledge The proportion of illness: the incidence rate is about 0.003% - 0.005% Susceptible people: no specific population Mode of infection: non-infectious Complications: pneumothorax mediastinal emphysema acute pulmonary edema
Cause
Causes of cough asthma
Genetic (35%):
The etiology of cough asthma is complicated, the quality and quantity of external sensitization and/or non-sensitizing stimulating substances are not consistent, and the body has individual differences due to genetic quality, which leads to the body's incomplete response to stimulation. The main pathological changes of asthma are chronic non-specific inflammation of the airway, which causes bronchial smooth muscle spasm, airway mucosal edema and hypertrophy, increased mucus secretion, mucociliary dysfunction and bronchial mucus embolism, etc. due to various pathological changes of different organisms. Different, therefore, different body or the same body will produce different clinical manifestations at different times and occasions. If the patient has significant bronchial smooth muscle spasm, it can be expressed as wheezing. If mild bronchospasm occurs, it can be clinically manifested. Chest tightness is the main cause. If the bronchial mucosa is mainly swollen, it can be clinically manifested as cough.
Cough receptor (18%):
Cough is a self-protection mechanism for removing foreign substances or mucus and secretions in the airway. Cough receptors include two major categories: mainly concentrated in the carina, which are stimulated by slight touch or inhalation of dust. C fiber, its tip Located in the pharynx, bronchial tree and alveoli, mainly reacting to chemical irritants such as captopril, certain inflammatory mediators (such as bradykinin), and also by some mechanical forces, including C fibers. The release of neuropeptides (such as substance P) can enhance the activation of A fibers. After the receptors are stimulated, they are transmitted to the medulla cough center through the vagus nerve, and then the efferent nerves are used to make the diaphragm, intercostal muscles, and pharynx corresponding. Coughing action, Simosson et al found that there is a similar composition between the reflex arc causing cough and the reflex arc of bronchoconstriction, which are composed of receptors under the epithelial submucosa, afferent nerves, medullary center, efferent nerves and muscles. Increased responsiveness and increased cough frequency are caused by stimulation of the same receptor. During the pathogenesis of bronchial asthma, certain pathogenic factors stimulate the airway epithelium. The cough receptor directly causes coughing through the vagus pathway, or indirectly causes cough reflexes by causing local bronchoconstriction.
Wheezing threshold (15%):
Mc Fadden pointed out that cough asthma is mainly caused by airway stenosis. Because of the abundant cough receptors in the airway, cough is the main manifestation. However, typical bronchial asthma acts on the airway and acts on the surrounding airway due to inflammation. In addition to cough, there is still wheezing and difficulty in breathing. In asthma patients, due to persistent airway inflammation, the surface of the bronchial epithelium is damaged, and the vagus nerve receptors under the tight junction site between epithelial cells are exposed and easily provoked, and the threshold of excitation is low. In normal people, the sensitivity to various stimuli is increased, so it can cause intractable cough. By using different concentrations of acetylcholine bronchial provocation test in children with typical bronchial asthma, it is pointed out that the wheezing threshold of children with cough asthma is higher than typical. In the asthma group, it may be one of the reasons for coughing and not breathing.
The cause of cough asthma is the same as that of nocturnal asthma. In addition to the subjective factors such as the patient's own "genetic quality", immune status, mental state, endocrine and health status, allergens, viral infections, occupations Environmental factors such as factors, climate, drugs, exercise and diet are also important causes of asthma development.
Prevention
Cough asthma prevention
Avoid contact with allergens, pay attention to it during the season of good hair, and avoid inhaling smoke, odor or irritating gas, which has a good preventive effect on preventing asthma attacks.
Complication
Cough asthma complications Complications, pneumothorax, mediastinal emphysema, acute pulmonary edema
Can be combined with hypoxemia, pneumothorax, mediastinal emphysema, severe acute pulmonary edema.
Symptom
Cough asthma symptoms Common symptoms Chronic cough bronchial smooth muscle airway hyperresponsive emotional asthma persistent cough and eczema
1. In adults with cough asthma, the age of onset is higher than that of typical asthma. About 13% of patients are older than 50 years old. Middle-aged women are more common. In childhood, cough may be the only symptom of asthma. It even developed into a precursor to bronchial asthma.
2, more clear family history of allergies or other parts of the history of allergic diseases, such as allergic rhinitis, eczema.
3, most of the attacks have a certain seasonality, with more spring and autumn.
4, the clinical manifestations are mainly long-term intractable dry cough, often in exercise, inhaled cold air, induced by upper respiratory tract infection, intensified at night or in the early morning, no wheezing during physical examination, lung function damage between normal and typical asthma The skin allergen test can be positive.
5, bronchial provocation test is positive, when a positive reaction occurs, there may be a irritating cough similar to the onset of the disease, suggesting the presence of airway hyperresponsiveness; the reversibility test of airway obstruction is positive.
6, the general cough and phlegm and antibiotic treatment is not effective, but with antihistamines, 2-receptor agonists, theophylline or adrenocortical hormone can be alleviated.
Examine
Cough asthma test
The bronchial provocation test was positive.
1. Chest X-ray examination is normal.
2, most of the lung function tests are normal, a small number of patients may have mild obstructive ventilatory dysfunction, FEV1/FVC (forced expiratory volume per second / forced vital capacity) <70% or <80% of the normal expected value.
Diagnosis
Diagnosis and diagnosis of cough asthma
Diagnostic criteria
In the case of patients who only complain of long-term cough (time greater than 2 weeks), the possibility of asthma should be considered. Based on detailed medical history, careful physical examination, and summary of clinical characteristics, the following methods can be used to confirm the diagnosis:
1. If the FEV1 or PEFR measured at the time of the patient's visit is less than 70% of the normal value, the bronchodilator, such as 2% albuterol 200g, may be inhaled. After 15 minutes, the above indicators are retested, such as the improvement rate of FEV1 and PEFR 15%. Can diagnose the disease.
2. If the patient is expected to have a normal FEV1 and PEFR 70% at the time of the visit, the bronchial provocation test may be performed cautiously.
3. Determination of PEFR day and night changes within 24 hours for 3 consecutive days is a simple and effective screening method for diagnosing such bronchial asthma. If the PEFR mutation rate is 20%, the disease can be diagnosed.
Although the measurement of lung function indicators is an effective means of early detection of such asthma, it has been found that the frequency of day and night cough is not related to the degree of lung function damage.
4, experimental treatment
For suspicious patients, you can try bronchodilators, including 2 receptor stimulants, theophylline, such as cough significantly reduced or disappeared, support the diagnosis of bronchial asthma; if the effect is not significant, you can use prednisone (30 ~ 40mg) /d), most cough asthma can be significantly relieved within 1 week, a small number of patients need to be treated for 2 weeks to be effective.
5. Exclude other diseases that can cause chronic cough.
Differential diagnosis
Because cough is a non-specific symptom of many diseases, it is necessary to ask the medical history in detail when making a diagnosis. Comprehensive physical examination, chest X-ray, electrocardiogram, fiberoptic bronchoscopy and some special examinations can exclude chronic and intractable cough. Other diseases, chronic bronchitis, gastroesophageal reflux, bronchial asthma, and postnasal drip are the most common causes of chronic cough, and some patients with gastroesophageal reflux can coexist with bronchial asthma; in addition, chronic heart failure, esophageal hiatus, allergies Rhinitis, hypertension, airway inflammation, tumors, tuberculosis, foreign bodies and smoke stimuli, anxiety, etc. can lead to chronic cough.
