The common causes of chronic cough are: cough variant asthma (CVA), postnasal drip syndrome (PNDs), eosinophilic bronchitis (EB) and gastro-oesophageal reflux cough (GERC), which account for 70% to 95% of chronic cough in respiratory medicine outpatient clinics.
I. 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.
2. Clinical manifestations: The main manifestation is a prickly dry cough, usually violent, with nighttime 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 a pronounced nocturnal irritant cough.
(2) Positive bronchial excitation test or diurnal variability of maximal expiratory flow (PEF) >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 be treated with small doses of glucocorticoids plus beta agonists, and oral glucocorticoid therapy is rarely needed. The duration of treatment should be at least 6-8 weeks.
PNDs
1. Definition: PNDs are syndromes in which the main manifestation is cough due to nasal diseases that cause secretions to flow backwards into the postnasal area and throat, or even backwards into the voice box 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. Usually there is a history of upper respiratory tract disease (e.g., cold) before the onset.
3. Diagnosis: The underlying diseases that cause 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 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 the paranasal sinuses of more than 6 mm, 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 feasible 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 a feeling of mucus adherence to the posterior pharyngeal wall.
(3) History of rhinitis, sinusitis, nasal polyps or chronic pharyngitis.
(4) Examination reveals mucus adherence and cobblestone-like view of the posterior pharyngeal wall.
(5) Relief of cough after targeted treatment.
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 a diagnosis. In recent years, some scholars have directly adopted rhinitis/sinusitis as the etiological diagnosis of chronic cough, without using the terminology of 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
(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 have an effect within a few days to 2 weeks after the initial treatment.
Various antihistamines are effective in the treatment of allergic rhinitis, and second-generation antihistamines without sedative effects are preferred.
Nasal inhalation glucocorticoid is the drug of choice for allergic rhinitis, 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, applied at a dose of 20 mg/dose, 3-4 times a day. Improving the environment and avoiding allergenic stimuli 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 poor or the secretion is high.
For the treatment of chronic sinusitis, the following primary treatment regimen is recommended: 3 weeks of antibacterial drugs effective against gram-positive, gram-negative and anaerobic bacteria; 3 weeks of oral first-generation antihistamines and decongestants; 1 week of nasal decongestants; and 3 months of nasal inhalation of glucocorticoids. Negative pressure drainage, puncture drainage or surgery is feasible when internal treatment is not effective.
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 coughing up 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: The clinical manifestations of EB are not characteristic, some of them are similar to CVA, and there are no abnormal findings on physical examination. The 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 function, negative airway hyperresponsiveness test, and normal PEF inter-day variability.
(4) Sputum cytology with eosinophil ratio ≥0.03.
(5) Exclude other eosinophilic diseases.
Oral or inhaled glucocorticoids are effective.
4. Treatment: EB responds well to glucocorticoid therapy and the cough disappears or is significantly reduced after treatment. Bronchodilator treatment is not effective.
Usually inhaled glucocorticosteroids are used, such as beclomethasone dipropionate (250~500μg each time) or equivalent doses of other glucocorticosteroids, twice a day 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. GERC
1.Definition: GERC is a common cause of chronic cough due to reflux of stomach acid and other gastric contents into the esophagus, resulting in a prominent clinical manifestation of 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: 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 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)24h 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) Pro-gastric motility drugs: 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 few patients with severe reflux who fail medical treatment, anti-reflux surgery can be considered.