The etiology of chronic cough is relatively complex, and clarifying the cause is the key to successful treatment. When the cause of cough is unknown or infection cannot be excluded, glucocorticoids should be used with caution.
(i) Cough variant asthma (CVA)
CVA is a special type of asthma in which cough is the only or main clinical manifestation without obvious symptoms or signs such as wheezing and shortness of breath, but with airway hyperresponsiveness. The main manifestation is a prickly dry cough, usually more violent, with nocturnal cough as its important feature. Cold, cold air, dust and fumes can easily trigger or aggravate the cough. Conventional anti-cold and anti-infection treatment is ineffective, and bronchodilator treatment can effectively relieve cough symptoms, and this point can be used as the basis for diagnosis and differential diagnosis. Pulmonary ventilation function and airway hyperresponsiveness examination are the key methods to diagnose CVA. the principles of CVA treatment are the same as those of asthma treatment. Most patients can be treated with low-dose glucocorticoids plus beta agonists, and oral glucocorticoid therapy is rarely required. The duration of treatment is not less than 6~8 weeks.
(ii) Postnasal drip syndrome (PNDs)
PNDs are syndromes in which secretions flow backwards into the postnasal and pharyngeal areas, or even backflow into the vocal cords or trachea due to nasal diseases, resulting in cough as the main manifestation.
In addition to cough and sputum, patients with PNDs usually complain of flu dripping from the throat, adherence of oropharyngeal mucus, frequent throat clearing, throat itching discomfort or nasal itching, nasal congestion, runny nose, and sneezing. Sometimes patients complain of hoarseness and speech induced cough, but other causes of cough itself also have such complaints. Often the onset is preceded by a history of upper whistle disease (e.g., cold). The underlying diseases causing PNDs include seasonal allergic rhinitis, perennial allergic rhinitis, perennial non-allergic rhinitis, vasodilatory rhinitis, infectious rhinitis, fungal rhinitis, common cold, and paranasal sinusitis. Those with large amounts of sputum are mostly due to chronic sinusitis. Vasodilatory rhinitis is characterized by large amounts of thin, watery nasal secretions sometimes produced in response to changes in temperature. Treatment: Depends on the underlying disease causing the PNDs. By (1) non-allergic rhinitis. (2) vasodilatory rhinitis. (3) Year-round rhinitis. (4) Common cold. First-generation antihistamines (representative drug is chlorpheniramine maleate) and decongestants (representative drug is pseudoephedrine hydrochloride) are preferred for PNDs caused by. Antibacterial drug therapy is the main drug for acute bacterial sinusitis, and nasal inhalation glucocorticoids and decongestants can be used to reduce inflammation when the effect is poor or the secretion is high.
For the treatment of chronic sinusitis, the following primary treatment regimen is recommended: application of antibacterial drugs effective against gram-positive, gram-negative and anaerobic bacteria for 3 weeks; oral first-generation antihistamines and decongestants for 3 weeks; nasal decongestants for 1 week; and nasal inhaled glucocorticoids for 3 months. Negative pressure drainage, puncture drainage or surgery is feasible when internal treatment is ineffective.
(iii) Eosinophilic bronchitis (EB)
The main symptom is a chronic irritant cough, often the only clinical symptom, usually dry, occasionally with a little mucous sputum, which can be coughed during the day or at night. Some patients are sensitive to fumes, dust, odors or cold air, which are often triggers for coughing. Patients have no symptoms such as shortness of breath or dyspnea, normal pulmonary ventilation function and peak whistle flow rate variability (PEFR), and no evidence of airway hyperresponsiveness. Treatment: EB responded well to glucocorticoid therapy, and the cough disappeared or was significantly reduced after treatment. Bronchodilator therapy is ineffective.
Treatment is usually with inhaled glucocorticoids, beclomethasone dipropionate (250-500 μg per dose) or equivalent doses of other glucocorticoids, applied twice daily for more than 4 weeks. Dry powder inhalers are recommended. Initial treatment can be combined with prednisone orally at 10-20 mg per day for 3-7 d.
(iv) Gastro-esophageal reflux cough (GERC)
GERC is a common cause of chronic cough, due to reflux of gastric acid and other gastric contents into the esophagus, resulting in cough as the prominent clinical manifestation. Typical reflux symptoms manifest as burning sensation behind the sternum, acid reflux, belching and chest tightness. GER patients with trace aspiration are more likely to have cough symptoms and throat symptoms in the early stage. There are also many patients with GERC who have no clinical symptoms of reflux, and cough is their only clinical manifestation. The cough mostly occurs in the daytime and in the upright position, with a dry cough or a small amount of white mucous sputum.
Diagnosis: The patient’s cough with reflux-related symptoms or cough after eating is of some significance in suggesting the diagnosis. 24h esophageal pH monitoring is currently the most effective method to diagnose GERC. Treatment: (1) Lifestyle modification: lose weight, eat less and more often, avoid oversaturated bedtime meals, avoid acidic and greasy foods and beverages, avoid coffee and smoking. High pillow position and elevated bed head. (2) acid control drugs: often choose proton pump inhibitors (such as omeprazole or other similar drugs) or H2 receptor antagonists (ranitidine or other similar drugs). (3) Gastric stimulants: such as domperidone, etc. (4) Any patient with underlying gastroduodenal disease (chronic gastritis, gastric ulcer, duodenitis or ulcer) with H. pylori infection should be treated accordingly. (5) The duration of medical treatment should be more than 3 months, usually 2 to 4 weeks to show the effect. In a small number of patients with severe reflux who fail medical treatment, anti-reflux surgery may be considered.
Other causes and treatment of chronic cough
(i) Chronic bronchitis
For cough and sputum for more than 2 consecutive years, accumulating or persisting for at least 3 months each year, and excluding other causes of chronic cough. The cough and sputum are usually obvious in the morning, with white foamy sputum or mucus sputum, and nocturnal cough is also present during the exacerbation period. Antibiotic therapy is usually required.
(ii) Bronchiectasis is caused by the destruction of the airway wall due to chronic inflammation, resulting in non-reversible bronchial dilatation and luminal deformation, with sub-segmental bronchi as the main lesion site. The clinical manifestations are cough, coughing up pus sputum and even hemoptysis. The diagnosis is not difficult for those with a typical medical history, while mild bronchiectasis without a typical medical history is easily misdiagnosed. x-ray chest changes (e.g., curly hair-like) are suggestive of the diagnosis, and when bronchiectasis is suspected, the best diagnostic method is high-resolution CT of the chest. antibacterial and sputum treatment are required.
(iii) Allergic cough (AC)
Irritating dry cough, mostly paroxysmal, daytime or nighttime cough, easily induced by fumes, dust, cold air, speech, etc., often accompanied by a tickling throat. Ventilation is normal, and the percentage of eosinophils on induced sputum cytology is not high. Treatment: Antihistamine drug therapy is effective, with the addition of inhaled or short-term (3-7d) oral glucocorticoids if necessary.
(iv) Post-cold cough is clinically referred to as post-cold cough when the cough remains persistent after the symptoms of the acute phase of the cold itself have disappeared. In addition to whistling viruses, other whistling infections may also cause this type of cough, which is collectively referred to as post-infectious cough in the literature. Patients present with an irritating dry cough or a small amount of white mucus sputum that may persist for 3-8 weeks or longer, with no abnormalities on chest X-ray.
Post-cough is often self-limiting and usually resolves on its own. Antibacterial medication is not effective. Short-term application of antihistamine H1 receptor antagonists and central cough suppressants can be used for some chronic prolonged coughs. For a few patients with persistent severe post-cold cough, a short-term trial of inhaled or oral glucocorticoid therapy, such as 10-20 mg of prednisone (or equivalent amount of other hormones) for 3-7 d, can be used if general treatment is ineffective.
(v) Endobronchial tuberculosis: The proportion of endobronchial tuberculosis in the etiology of chronic cough is not clear, but it is not uncommon in China, and most of them are combined with intrapulmonary tuberculosis. There is no obvious abnormal change in the X-ray chest film, so it is easy to misdiagnose and miss the diagnosis clinically.
Patients suspected of endobronchial tuberculosis should first undergo a general sputum smear to look for antacid bacilli. The direct signs of X-ray chest radiograph are not many, but can reveal lesions such as wall thickening, lumen narrowing or obstruction of trachea and main bronchus, etc. CT, especially high-resolution CT, is more sensitive than X-ray chest radiograph in showing signs of bronchial lesions, especially the lesions of sublobular bronchus, which can indirectly suggest the diagnosis. Fibronectomy is the main means to confirm the diagnosis of endobronchial tuberculosis, and the positive rate of routine microscopic brushing and tissue biopsy is high.
(vi) Angiotensin-converting enzyme inhibitor (ACEl)-induced cough: cough is a common adverse effect of taking ACEI-type antihypertensive drugs, with an incidence of about 10% to 30%, accounting for 1% to 3% of the etiology of chronic cough. Cough relief after discontinuation of ACEI can confirm the diagnosis. The cough usually disappears or is significantly reduced after 4 weeks of discontinuation. Angiotensin II receptor antagonists can replace ACEIs.
(vii) Psychogenic cough Psychogenic cough is caused by serious psychological problems or intentional throat clearing in patients, and is also referred to by some authors as habitual cough and psychogenic cough. It is relatively common in children, accounting for 3% to 10% of cough causes in children over 1 month of age. The typical presentation is a daytime cough that disappears when focused on something and when resting at night, often accompanied by anxiety symptoms.
The diagnosis of psychogenic cough is exclusive and can be considered only after other possible diagnoses have been excluded. The main treatment for psychogenic cough in children is suggestive therapy, which can be supplemented by short-term application of cough suppressants. In older patients, psychological counseling or psychiatric intervention can be supplemented with appropriate anti-anxiety medication.
(viii) Other rare etiologies such as bronchopulmonary cancer, interstitial lung fibrosis, bronchial microlithiasis, left heart insufficiency, etc.