Chronic cough is defined as a cough that is the only or main symptom, lasts more than 8 weeks and does not show any significant abnormalities on chest X-ray. It is present in up to 10-40% of the non-smoking adult population and is a common reason for visits to respiratory clinics. Probably more than 30% of my own specialist clinics are for chronic or subacute cough. Chronic cough negatively affects patients’ psychological and social functioning, quality of life, and in severe cases, sleep and even urinary incontinence. Therefore, it is important to make a timely diagnosis to effectively control cough symptoms and relieve patients’ suffering.
Chronic cough has a relatively complex etiology, and identifying the cause is the key to successful treatment. Most chronic coughs are not associated with infections and do not require antimicrobial therapy. The following are some common causes and treatment options.
(i) Cough variant asthma (CVA)
1. Definition: 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, i.e. positive bronchial excitation test.
2. Clinical manifestations: The main manifestation is an irritating dry cough, which is usually violent and has a nocturnal cough as its important feature. Cold, cold air, dust and oil smoke can easily trigger or aggravate the cough.
3. Diagnosis: Conventional anti-cold and anti-infection treatment is ineffective, and bronchodilator treatment can effectively relieve cough symptoms, which can be used as a basis for diagnosis and differential diagnosis. Pulmonary ventilation function and airway hyperresponsiveness examination are the key methods to diagnose CVA. Diagnostic criteria: ( 1) Chronic cough often accompanied by significant nocturnal irritant cough. (2) Positive bronchial excitation test or maximal expiratory flow (PEF)
(2) Positive bronchial excitation test or maximum expiratory flow volume (PEF) diurnal variability > 20%. ( 3) Effective treatment with bronchodilators and glucocorticoids. ( 4) Exclude other causes of chronic cough.
4. Treatment: The principles of CVA treatment are the same as those of asthma treatment. Most patients can receive small doses of inhaled glucocorticoids plus beta agonists, and oral glucocorticoid therapy is rarely required. The duration of treatment is not less than 6-8 weeks, and some patients require more than half a year of treatment.
(ii) Upper airway cough syndrome (UACS)
1. Definition: UACS is a syndrome in which cough is the main manifestation due to nasal diseases that cause secretions to flow backward into the postnasal and pharyngeal regions, or even backward into the vocal cords or trachea.
2. Clinical manifestations: In addition to cough and sputum, patients with PNDs usually complain of flu drip in the throat, mucus adhesion in the oropharynx, frequent throat clearing, throat itching or nasal itching, nasal congestion, runny nose, sneezing, etc. Sometimes patients may complain of hoarseness. Sometimes patients complain of hoarseness, and speech can trigger coughing, but other causes of coughing themselves also have such complaints. Often the onset is preceded by a history of upper respiratory tract disease (e.g., cold).
3. Diagnosis: The underlying diseases causing UACS 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 a large amount of thin, watery nasal discharge that sometimes occurs in response to changes in temperature. Imaging signs of chronic sinusitis are mucosal thickening of more than 6 mm in the paranasal sinuses, air-fluid planes, or sinus cavity obscuration. SPT can be helpful if the cough is seasonal or if the history suggests exposure to specific allergens (e.g., pollen, dust mites). Skin tests for Aspergillus and other fungi and specific IgE tests are indicated when allergic fungal sinusitis is suspected.
Diagnostic criteria: (1) Episodic or persistent cough, predominantly during the day and less frequently after sleep. ( 2) Postnasal drip and/or pharyngeal
(2) Postnasal drip and/or mucus adhesion sensation in the posterior pharyngeal wall. (3) History of rhinitis, sinusitis, nasal polyps or chronic pharyngitis. ( 4) Examination reveals mucus adhesion and pebble-like view of the posterior pharyngeal wall. (PNDs involve a variety of underlying diseases, and their diagnosis is mainly based on a combination of history and relevant examinations, so other common causes of chronic cough should be excluded before establishing the diagnosis. In recent years, some scholars have directly adopted rhinitis/sinusitis as the etiological diagnosis of chronic cough, instead of using the term PNDs.
4. Treatment: It depends on the underlying disease causing the PNDs. First-generation antihistamines and decongestants are preferred for PNDs caused by the following etiologies
Decongestants: ( 1) Non-allergic rhinitis. ( 2) Vasodilatory rhinitis. ( 3) Year-round rhinitis. ( 4) Common cold. The first generation of antihistamines is represented by chlorpheniramine maleate, and the commonly used decongestant is pseudoephedrine hydrochloride. The majority of patients develop efficacy within a few days to 2 weeks after initial treatment. All antihistamines are effective in the treatment of allergic rhinitis,
The first choice is a second-generation antihistamine without sedative effects, such as loratadine or asmizole. Nasal inhalation glucocorticoids are the first choice for allergic rhinitis, usually beclomethasone propionate (50 μg/dose per nostril) or equivalent doses of other inhaled glucocorticoids.
Inhaled glucocorticoids are usually beclomethasone propionate (50 μg/dose per nostril) or equivalent doses of other inhaled glucocorticoids once or twice daily. Sodium cromoglycate inhalation also has a good preventive effect on allergic rhinitis and is applied at a dose of 20 m g/dose 3-4 times a day. Improving the environment and avoiding allergen stimulation are effective measures to control allergic rhinitis. Allergen immunotherapy may be effective, but it takes a long time to take effect. Antibacterial drug therapy is the main drug for acute bacterial sinusitis, and nasal inhalation of glucocorticoids and decongestants can be used to reduce inflammation when the effect is not good or there is a lot of secretion. 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 inhalation of glucocorticoids for 3 months. Negative pressure drainage, puncture drainage or surgery is feasible when internal treatment is ineffective.
(iii) Eosinophilic bronchitis (EB)
1. Definition: A non-asthmatic bronchitis characterized by airway eosinophil infiltration, which is an important cause of chronic cough.
2. Clinical manifestations: The main symptom is chronic irritant cough, which is often the only clinical symptom, usually a dry cough, occasionally with a little mucous sputum, either during the day or at night. Some patients are sensitive to fumes, dust, odors or cold air, which are often triggering factors for coughing. Patients do not have symptoms such as shortness of breath and dyspnea. Pulmonary ventilation function and peak expiratory flow rate variability (PEFR) are normal, and there is no evidence of airway hyperresponsiveness.
3.Diagnosis: EB clinical manifestations are not characteristic, some of them are similar to CVA, no abnormal findings on physical examination, and the diagnosis mainly relies on induced sputum cytology. Specific criteria are as follows: (1) Chronic cough, mostly irritating dry cough, or with a small amount of mucous sputum.
(2) Normal X-ray chest radiograph. (3) Normal pulmonary ventilation, negative airway hyperresponsiveness test, and normal PEF inter-day variability. ( 4) Sputum cytology with eosinophil ratio ≥ 0,03. ( 5) Exclude other eosinophilic diseases. ( 6) Oral or inhaled glucocorticoids are effective.
4. Treatment: EB responds well to glucocorticoid treatment, and the cough disappears or is significantly reduced after treatment. Bronchodilator therapy is not effective. Usually treated with inhaled glucocorticoids, beclomethasone dipropionate (250-500μg each time) or equivalent doses of other glucocorticoids, twice a day for more than 4 weeks. Dry powder inhalers are recommended. Initial treatment can be combined with oral prednisone at 10-20 m g per day for 3-7 d.
(iv) Gastroesophageal reflux cough (GERC)
1. Definition: GERC is a common cause of chronic cough.
2. Clinical manifestations: Typical reflux symptoms include burning sensation behind the sternum, acid reflux, belching, chest tightness, etc. GER patients with trace aspiration are more likely to have cough symptoms and throat symptoms in the early stage. There are also many GERC patients who do not have reflux symptoms and whose cough is the 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.
3. Diagnosis: Coughing with reflux-related symptoms or coughing after eating is of some significance in suggesting the diagnosis. 24-h esophageal pH monitoring is currently the most effective method to diagnose GERC by dynamically monitoring the changes of distal and proximal esophageal pH, and the results are expressed as Demeester score and SAP. Barium meal examination and gastroscopy have limited diagnostic value for GERC, and the correlation between reflux and cough cannot be determined.
4. Diagnostic criteria.
(1) Chronic cough, mainly daytime cough.
(2)24 h esophageal pH monitoring Demeester score ≥12.70, and/or SAP ≥75%.
(3) Exclude CVA, EB, PNDs and other diseases.
(4) Significant reduction or disappearance of cough after anti-reflux treatment.
For patients with chronic cough in units without esophageal pH monitoring or those with limited economic conditions, diagnostic therapy may be considered for the following indications
(1) The patient has a significant feeding-related cough, such as postprandial cough and feeding cough.
(2) Patients with GER symptoms, such as acid reflux, belching, and retrosternal burning sensation.
(3) Exclude diseases such as CVA, EB, PNDs, etc., or treat these diseases with poor results. The clinical diagnosis of GERC can be made if the cough disappears or is significantly relieved after anti-reflux treatment.
5. Treatment.
(1) Lifestyle adjustment: lose weight, eat less and more often, avoid oversaturated bedtime meals, avoid acidic and greasy foods and drinks, avoid coffee and smoking. High pillow position, elevate the head of the bed.
(2) acid medication: 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 requires more than 3 months, usually 2~4 weeks to show the effect. In a small number of patients with severe reflux who fail medical treatment, anti-reflux surgery may be considered.
(5) Other causes of cough: e.g., allergic cough (AC), ACEI-like drug-induced cough, psychological cough, etc.