What Are the Causes Of Chronic Cough?

The definition of chronic cough is that the cough lasts more than 8 weeks, and the cough with no evidence of lung disease on the chest X-ray is called chronic cough. Cough is often the only symptom for patients. Chronic cough is one of the common clinical symptoms of the respiratory system.

Basic Information

English name

chronic cough

Visiting department

Respiratory Medicine

Common causes

Various nasal, pharyngeal, and larynx diseases, gastroesophageal reflux, asthma, eosinophilic bronchitis, etc.

Common symptoms

cough

Causes of chronic cough

1. Cough due to various nose, throat, and throat diseases

Nasal diseases cause backflow of secretions, such as behind the nose and throat, which directly or indirectly stimulate cough receptors, and the syndrome that mainly results in cough is called postnasal drip syndrome (PNDS). Because it is currently unclear whether it is caused by upper respiratory cough receptors, the 2006 US Cough Diagnosis and Treatment Guidelines recommended the use of Upper Airway Cough Syndrome (UACS) instead of PNDS.

UACS is one of the most common causes of chronic cough. In addition to nasal diseases, UACS is often associated with diseases of the throat, such as allergic or non-allergic pharyngitis, laryngitis, new organisms in the throat, chronic tonsillitis, etc. . It is characterized by paroxysmal or persistent cough, mainly during the day, and less coughing after falling asleep, nasal drip and / or mucous adhesion of the posterior pharyngeal wall, rhinitis, sinusitis, nasal polyps or chronic pharyngitis In other medical history, the examination revealed mucus adhesion and cobblestone-like views in the posterior pharyngeal wall. Chronic sinusitis imaging showed thickening of the sinus mucosa and fluid level in the sinuses. Cough caused by the common cold may also be caused by irritation of secretions trickling down the nose. Because the common cold is the most common disease in humans, postnasal drip syndrome is one of the most common causes of cough. In recent years, with the climatic changes, air pollution has become worse, patients have been caught cold medicine, abused antibiotics, etc., which has caused the disease to increase.

2. gastroesophageal reflux cough

Cough is the most prominent clinical manifestation due to reflux of gastric acid and other gastric contents into the esophagus, which is a special type of gastroesophageal reflux disease (GERD). There are two perspectives on the relevant mechanism of GERD's appearance of extraesophageal manifestations, one is microinhalation, and the other is airway neurogenic inflammation caused by esophageal-bronchial reflex, both of which can cause airway hyperresponsiveness. Typical reflux symptoms are heartburn (burning sensation behind the sternum), acid reflux, and belching. Cough caused by some gastroesophageal reflux is accompanied by typical reflux symptoms, but cough is the only manifestation in many patients.

Cough is one of the most common extraesophageal symptoms of gastroesophageal reflux, followed by pharyngeal sensation and / or foreign body pharyngeal sensation, sore throat, and hoarseness. Most of the coughs are irritating dry coughs, but also coughs with phlegm. Most of them are coughing during the day, and some are coughing at night, often accompanied by heartburn, acid reflux and digestive symptoms such as chest pain and nausea. However, many patients are clinically free of reflux symptoms, and cough is the only clinical manifestation. 24-hour esophageal Ph monitoring can diagnose. The mechanism is unclear and may be related to the stimulation of cough receptors in the throat, throat, and trachea by reflux. The use of antacids or gastrointestinal motility drugs or H2 receptor blockers and proton pump inhibitors can quickly alleviate symptoms. The treatment time requires more than 3 months, and it usually takes 2 to 4 weeks for obvious effects.

3. "Asthma" Causes Cough-Cough Variant Asthma (CVA)

If you have a cough for more than 2 months, you should consider the possibility of variant asthma. It is a special type of asthma. Cough is the only or main clinical manifestation. It has no obvious symptoms or signs of wheezing and shortness of breath, but it has high airway responsiveness. The diagnostic criteria are: chronic cough is often accompanied by obvious nocturnal irritating cough; positive bronchial challenge test or peak expiratory flow rate (PEF) diurnal variation rate> 20%; bronchodilator treatment is effective; chronic cough caused by other reasons is excluded.

4. Eosinophilic bronchitis (EB) causes cough

It is a non-asthmatic bronchitis characterized by airway eosinophil infiltration. The clinical manifestation lacks characteristics. Most of them are chronic irritating dry cough or a little sticky sputum. They can cough during the day or at night. Some patients are more sensitive to oil fume, dust, odor or cold air. They are often the cause of cough. Induced sputum increased eosinophils, normal pulmonary ventilation, no airway hyperresponsiveness, and normal day-to-day variability of PEF. The ratio of eosinophils in sputum cytology is 2.5%; other eosinophilic diseases are excluded; oral or inhaled glucocorticoids are effective, and bronchodilator treatment is ineffective. The majority of patients had a disease course of more than 3 months or even several years before the consultation. Some patients are related to inhaled allergens, such as dust mites, pollen, mushroom spores, etc., but also to occupational exposure to chemical agents or chemicals, such as rubber gloves, acrylates, and so on. Usually treated with ICS, beclometasone propionate or other equivalent glucocorticoids, 2 times a day, continuous application for more than 4 weeks, dry powder inhalation is recommended; initial treatment can be combined with prednisone orally.

5. Allergic cough (AC)

There are currently no recognized standards. The following standards are for reference:

(1) chronic cough, mostly irritating dry cough;

(2) The pulmonary ventilation function is normal, and the bronchial provocation test is negative;

(3) One of the following indications: history of allergic disease or history of contact with allergic substances; positive allergen skin test; increased serum total IgE or specific IgE; increased cough sensitivity. Antihistamine treatment has some effects, if necessary, add inhalation or short-term (3-7 days) oral glucocorticoids.

The above conditions are the most common causes of chronic cough. In addition to the above, there are several other causes of cough. Many interstitial lung diseases often have dry cough as the main symptom in the early stage. In this case, pulmonary function tests are helpful for early detection; drug-induced coughs are common in ACEI and blockers, and the incidence is about 15%. . It occurs 24 hours or several months after taking the medicine, and there are more women than men, which may be related to increasing the sensitivity of the cough sensor. Relieve after several days to 4 weeks of drug withdrawal; after excluding these factors, psychogenic cough can be considered, which is related to negative emotions such as tension, anxiety, and sadness. It is characterized by a cough that is bark-like or goose-like, irritating dry cough, and often accompanied by clear throat. Cough has nothing to do with eating or drinking. Infectious cough can gradually develop into psychogenic cough.

Clinical manifestations of chronic cough

The clinical manifestations can be seen by combining the clinical manifestations with different etiologies leading to cough.

Chronic cough test

1. Increased airway reactivity, mostly mild-moderate increase. The test procedure can induce an irritating cough at a similar onset.

2. Lung function impairment is between normal and typical asthma.

3. Skin allergen test can be positive.

4. Increased serum IgE levels.

5. Bronchodilation test may be positive in some patients. When a positive reaction occurs, it indicates that the airway has a certain state of spasm and obstruction.

6. Peripheral blood eosinophil count increased and serum ECP level increased.

Diagnosis of chronic cough

Attach importance to medical history, including history of medication, ENT, and digestive system examinations; select relevant examinations based on medical history, from simple to complex examinations; common diseases followed by rare diseases; diagnosis and treatment should be performed simultaneously or sequentially; when conditions are not available, according to The clinical features and incidence of the disease were diagnosed; some of them had effects to consider the multiple causes of cough.

The causes of chronic cough are complex, most commonly CVA, UACS, GERC, AC, and EB. The use of chronic cough etiology diagnostic procedures allows more than 80% of patients to obtain a causative diagnosis and obtain good treatment results. The "cough diagnosis and treatment guidelines" "Diagnose the disease.

Chronic cough treatment

Commonly used therapeutic drugs include: glucocorticoids, ₂ receptor agonists, antihistamines, antireflux drugs, antibiotics, etc.

Glucocorticoid

It is an anti-airway inflammation drug, mainly manifested as reducing airway epithelial inflammation and reducing airway hyperresponsiveness, and is used for the treatment and cough variant asthma, eosinophilic bronchitis, upper airway cough syndrome and allergic cough. .

2. ₂ receptor agonist

The mechanism of action of ₂ receptor agonists includes exciting ₂ receptors on the surface of airway smooth muscle and mast cell membranes, relaxing airway smooth muscle, reducing the release of mast cells and basophil granulocytes and their mediator release, and reducing microvascular permeability Sex, increase the swing of airway epithelial cilia and so on.