The definition of chronic cough is currently considered to be a cough lasting ≥8 weeks or more, with no obvious evidence of pulmonary disease on X-ray chest radiographs, and cough is often the only symptom for which the patient is seen. Chronic cough is one of the common clinical symptoms of the respiratory system, and Chinese medicine treatment has great advantages.
Etiology
1. Various nasal, pharyngeal and laryngeal diseases cause cough
Nasal diseases cause secretions to back up behind the nose and throat, which directly or indirectly stimulate cough receptors, resulting in a syndrome with cough as the main manifestation is called postnasal drip syndrome (PNDS). Because it is not clear whether the cough is caused by upper airway cough receptors, the 2006 U.S. Cough Guidelines recommend replacing PNDS with upper airway cough syndrome (UACS).
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, pharyngeal neoplasia, and chronic tonsillitis. It is characterized by episodic or persistent cough, predominantly during the day and less frequently after sleep, postnasal drip and/or a sense of mucus attachment to the posterior pharyngeal wall, a history of rhinitis, sinusitis, nasal polyps, or chronic pharyngitis, and an examination that reveals a mucus-attached, cobblestone-like view of the posterior pharyngeal wall. Imaging of chronic sinusitis reveals thickening of the sinus mucosa and the presence of fluid planes in the sinuses. Cough caused by the common cold may also be caused by secretions irritated along the postnasal drip. Since 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, the incidence of this disease has been increasing due to climate change, increased atmospheric pollution, and the stacking of cold medications and abuse of antibiotics by patients.
2. Gastroesophageal reflux cough
GERD is a special type of gastroesophageal reflux disease (GERD) that is caused by reflux of stomach acid and other gastric contents into the esophagus, resulting in a prominent clinical manifestation of cough. there are two views on the mechanism associated with the appearance of extraesophageal manifestations of GERD, one being microaspiration and the other being neurogenic inflammation of the airway caused by the esophageal-bronchial reflex, both of which can cause airway hyperreactivity. Typical reflux symptoms manifest as heartburn (burning sensation behind the sternum), acid reflux, and belching. Some GERD-induced coughs are accompanied by typical reflux symptoms, but a number of patients have cough as the only manifestation.
Cough is one of the most common extraesophageal symptoms of GERD, followed by pharyngeal bulb sensation and/or foreign body sensation in the throat, burning pain in the throat, and hoarseness. The cough is mostly irritating and dry, but can also be characterized as a cough with sputum. Most of the coughs are daytime coughs, and some of them are nocturnal coughs, often accompanied by heartburn, acid reflux, chest pain, nausea and other digestive symptoms. However, there are many patients who have no reflux symptoms at all, and cough is their only clinical manifestation. 24-hour esophageal Ph monitoring is diagnostic. The mechanism is unclear and may be related to the stimulation of cough receptors in the pharynx, larynx and trachea by reflux. The use of acid-suppressants or gastrointestinal stimulants or H2 receptor blockers or proton pump inhibitors can rapidly reduce symptoms, and the duration of treatment requires more than 3 months, usually 2-4 weeks to show efficacy.
3. Cough caused by “asthma” – cough variant asthma (CVA)
If the cough has been present for more than 2 months, the possibility of variant asthma should be considered. It is a special type of asthma in which cough is the only or main clinical manifestation without obvious signs or symptoms such as wheezing and shortness of breath, but with airway hyperresponsiveness. The diagnostic criteria are: chronic cough often accompanied by significant nocturnal irritant cough; positive bronchial excitation test or peak expiratory flow rate (PEF) diurnal variability >20%; effective bronchodilator treatment; exclusion of other causes of chronic cough.
4. Eosinophilic bronchitis (EB)
Cough caused by a non-asthmatic bronchitis characterized by airway eosinophil infiltration. The clinical manifestations lack characteristics and are mostly chronic irritating dry cough or cough with little mucus sputum, which can be coughing during the day or at night. Some patients are sensitive to fumes, dust, odors or cold air, which are often triggering factors for coughing. Eosinophilia in induced sputum, normal pulmonary ventilation, no airway hyperresponsiveness, and normal day-to-day variability of PEF. Sputum cytology with eosinophil ratio ≥2.5%; other eosinophilic diseases were excluded; oral or inhaled glucocorticoids were effective and bronchodilator therapy was ineffective. Most of the patients had been ill for more than 3 months or even for more than several years prior to consultation. Some patients are associated with inhalation of allergens, such as dust mites, pollen, mushroom spores, etc., and also with occupational exposure to chemicals or chemical products, such as rubber gloves and acrylic salts. Usually treated with ICS, beclomethasone propionate or equivalent doses of other glucocorticoids, applied twice daily for more than 4 weeks, and dry powder inhalers are recommended; initial treatment can be combined with oral prednisone.
5. Allergic cough (AC)
There are no accepted criteria; the following criteria are for reference.
(1) chronic cough, mostly irritating dry cough; (2) normal pulmonary ventilation and negative bronchial excitation test; (3) one of the following indications: (1) history of allergic disease or exposure to allergic substances; (2) positive allergen skin test; (3) increased total serum IgE or specific IgE; (4) increased cough sensitivity. Antihistamine medication is effective, and if necessary, inhaled or short-term (3-7 days) oral glucocorticoids are added.
The above-mentioned 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 a dry cough as the main symptom in the early stages, in which case pulmonary function tests can help with early detection; drug-induced cough is commonly associated with ACEI and beta-blockers, with an incidence of about 15%. It occurs 24 hours or months after taking the drug, more in women than men, and may be related to increased sensitivity of cough receptors. It resolves after several days to 4 weeks of drug discontinuation; after excluding these factors, psychogenic cough can be considered and is associated with negative emotions such as stress, anxiety, and sadness. It is characterized by a barking or goose cough, an irritating dry cough, often accompanied by clear throat sounds. The cough is not associated with food or water intake. Infectious cough can gradually evolve into a psychogenic cough.
Clinical manifestations can be seen in combination with the different causes of the cough.
Examination
1. Increased airway reactivity, mostly mild to moderate. The test procedure may induce an irritating cough similar to that at the onset.
2. Lung function impairment is between normal and typical asthma.
3, Skin allergen test may be positive.
4.Serum IgE level is increased.
5.Bronchodilator test may be positive in some patients. When there is a positive reaction, it indicates the presence of certain spasm and obstructive state of airway.
6. The peripheral blood eosinophil count is increased and the serum ECP level is increased.
Diagnosis attaches importance to medical history, including history of medications taken, history of otorhinolaryngological and digestive system examination; selection of relevant tests according to medical history, with tests ranging from simple to complex; common diseases first, followed by rare diseases; diagnosis and treatment should be carried out simultaneously or sequentially; when conditions are not available, diagnostic treatment is carried out according to clinical features and morbidity ratio; partly effective consideration of the multiplicity of cough etiology.
The etiology of chronic cough is complex, with CVA, UACS, GERC, AC, and EB being the most common; the use of diagnostic procedures for the etiology of chronic cough allows more than 80% of patients to obtain an etiological diagnosis and achieve good treatment results; the disease should be diagnosed in a practical manner according to the “Guidelines for the diagnosis and treatment of cough”.
Commonly used therapeutic drugs include: glucocorticoids, β2 agonists, antihistamines, anti-reflux drugs, antibiotics, etc.
1. Glucocorticoids are anti-inflammatory drugs that mainly reduce airway epithelial inflammation and airway hyperreactivity, and are used for the treatment of cough variant asthma, eosinophilic bronchitis, upper airway cough syndrome and allergic cough.
2, β2 receptor agonists β2 receptor agonists mechanism of action includes excitation of airway smooth muscle and mast cell membrane surface β2 receptors, diastole airway smooth muscle, reduce mast cell and basophil degranulation and their mediator release, reduce the permeability of microvessels, increase the oscillation of airway epithelial cilia, etc.