I. Overview of cough
Cough is a common symptom of respiratory diseases and facilitates the removal of respiratory secretions and harmful factors, but frequent and severe coughing can have a serious impact on patients’ work, life and social activities. Many patients are misdiagnosed as “chronic bronchitis” or “bronchiectasis” for a long time. Many patients are misdiagnosed as “chronic bronchitis” or “bronchiectasis” for a long time and are treated ineffectively with a large number of antimicrobial drugs or undergo repeated tests due to unclear diagnosis.
II. Definition of chronic cough
Chronic cough refers to a cough lasting ≥8 weeks, which has more causes and can usually be divided into two categories: one category is those with clear lesions on initial X-ray chest radiographs, such as pneumonia, tuberculosis and lung cancer. The other category is those who have no obvious abnormalities on X-ray chest radiographs and whose cough is the main or only symptom, which is usually referred to as chronic cough of unknown origin (chronic cough for short).
III. Common causes of chronic cough
The common causes of chronic cough are: cough variant asthma (CVA), postnasal drip syndrome (PNDs), eosinophilic bronchitis (EB), gastroesophageal reflux cough (GERC), and long-term oral intake of certain specific types of medications, which account for 70%-95% of chronic cough in respiratory medicine outpatient clinics. Other etiologies are less common but are widely involved, such as chronic bronchitis, bronchiectasis, endobronchial tuberculosis, allergic cough (AC), and psychogenic cough.
IV. Tests often required for chronic cough
1. Chest X-ray or chest CT: Its main purpose is to observe the presence of substantial lesions in the lungs.
2. Pulmonary function tests: including ventilation function, reversibility test and excitation test. The main purpose is to observe whether there is airway obstruction, elevated airway resistance and restricted airflow exhalation. Also observe how the airway reacts after giving bronchodilators or constrictors.
V. Clinical manifestations and treatment of different types of cough
1. 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.
(2) Clinical manifestations: The main manifestation is an irritating dry cough, usually more intense, with nocturnal cough as its important feature. Cold, cold air, dust and fumes can easily trigger or aggravate the cough.
(3) Diagnostic criteria: chronic cough often accompanied by obvious irritating cough at night; positive bronchial excitation test or maximal expiratory flow (PEF) diurnal variability >20%; effective treatment with bronchodilators and glucocorticoids; exclusion of 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 β2 agonists, and oral glucocorticoid therapy is rarely required.
(5) Course of treatment: The duration of treatment is not less than 6-8 weeks, i.e. 1.5-2 months.
2.Postnasal drip syndrome (PNDs)
(1) Definition: Postnasal drip syndrome refers to a syndrome in which secretions flow backwards into the postnasal and pharyngeal regions due to nasal diseases, or even backwards into the vocal cords or trachea, resulting in a cough as the main manifestation.
(2) Clinical manifestations: cough, coughing sputum, throat drip, oropharyngeal mucus attachment, frequent throat clearing, throat itching discomfort or nasal itching, nasal congestion, runny nose, sneezing, etc. Sometimes patients complain of hoarseness and speech induced cough. Often the onset is preceded by a history of upper respiratory tract illness (e.g., cold).
(3) Diagnostic criteria: episodic or persistent cough, mainly during the day and less often after sleep; postnasal drip and/or a feeling of mucus adhesion to the posterior pharyngeal wall; history of rhinitis, sinusitis, nasal polyps or chronic pharyngitis; examination reveals mucus adhesion and cobblestone-like view of the posterior pharyngeal wall; cough relief after targeted treatment.
(4) Treatment: Depending on the underlying disease causing postnasal drip syndrome.
First-generation antihistamines and decongestants are preferred for the treatment of postnasal drip syndrome caused by the following etiologies.
(i) non-allergic rhinitis.
(ii) vasodilatory rhinitis.
(iii) year-round rhinitis.
(iv) Common cold.
The representative first-generation antihistamine is paracetamol, and the commonly used decongestant is pseudoephedrine hydrochloride. Most patients develop efficacy within a few days to 2 weeks after initial treatment.
For the treatment of postnasal drip syndrome due to allergic rhinitis, second-generation antihistamines without sedation are preferred, commonly loratadine or cetirizine hydrochloride, and nasal inhaled glucocorticoids, commonly beclomethasone propionate (50 μg/dose per nostril) or equivalent doses of other inhaled glucocorticoids, 1-2 times 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. Improvement of the environment and avoidance of allergenic stimuli are effective measures to control allergic rhinitis. Allergen immunotherapy may be effective, but has a long onset of action.
For the treatment of postnasal drip syndrome due to acute bacterial sinusitis, antimicrobial drug therapy is the main drug, and nasal inhalation of glucocorticoids and decongestants may be used to reduce inflammation when the effect is poor or the secretion is high.
For the treatment of postnasal drip syndrome due to chronic sinusitis, the following primary treatment regimen is recommended: application of antimicrobial 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 + nasal inhaled glucocorticoids for 3 months. Negative pressure drainage, puncture drainage or surgery is feasible when internal treatment is not effective.
3.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 a chronic irritant cough, usually dry, with occasional little mucous sputum, which may be present 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 or dyspnea. Pulmonary ventilation function and peak expiratory flow rate variability (PEFR) are normal, and there is no evidence of airway hyperresponsiveness.
(3) Diagnostic criteria: chronic cough, mostly irritating dry cough, or with a small amount of mucus sputum; normal X-ray chest radiograph; normal pulmonary ventilation function, negative airway hyperresponsiveness test, normal PEF inter-day variability rate; sputum cytology examination eosinophil ratio ≥ 0.03 (3%); exclusion of other eosinophilic diseases; effective oral or inhaled glucocorticoids.
(4) Treatment: Eosinophilic bronchitis responds well to glucocorticoid therapy, and the cough disappears or is significantly reduced after treatment. Bronchodilator therapy is ineffective. It is usually treated with inhaled glucocorticoids, beclomethasone dipropionate (250-500 μg per dose) or equivalent doses of other glucocorticoids twice daily, and dry powder inhalers are recommended. Initial treatment can be combined with prednisone orally at 10-20
mg for 3-7 d.
(5) Course of treatment: continuous application for more than 4 weeks.
4.Gastroesophageal reflux cough (GERC)
(1) Definition: Reflux of gastric acid and other gastric contents into the esophagus, resulting in cough as the prominent clinical manifestation.
(2) Clinical manifestations: Typical reflux symptoms are burning sensation behind the sternum, acid reflux, belching, chest tightness, etc. Gastroesophageal reflux patients with trace aspiration are more likely to have cough symptoms and throat symptoms in the early stage. There are also many patients with gastroesophageal reflux cough who have no reflux symptoms and whose cough is the only clinical manifestation or who present with a post-feeding cough. 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) Diagnostic criteria: chronic cough, predominantly daytime cough; 24
h esophageal pH monitoring showed the presence of significant esophageal reflux; diseases such as cough variant asthma, eosinophilic bronchitis, and postnasal drip syndrome were excluded; the cough was significantly reduced or disappeared after anti-reflux treatment.
For patients with chronic cough in units without esophageal pH monitoring or with limited financial resources, diagnostic treatment may be considered for those with the following indications: the patient has significant feeding-related cough, such as postprandial cough, feeding cough, etc.; the patient has associated gastroesophageal reflux symptoms, such as acid reflux, belching, and retrosternal burning; cough variant asthma, eosinophilic bronchitis, and postnasal drip syndrome are excluded and other diseases, or the effect of treatment according to these diseases is poor.
(4) Treatment.
(1) Lifestyle adjustment: lose weight, eat less and more often, avoid oversaturated bedtime meals, avoid acidic and oily foods and beverages, avoid coffee and smoking. High pillow position and elevated bed head.
(ii) Acid suppressants: often proton pump inhibitors (such as omeprazole or other similar drugs) or H2 receptor antagonists (ranitidine or other similar drugs).
(iii) Gastric stimulants: such as domperidone, etc.
(iv) Any patient with underlying gastroduodenal disease (chronic gastritis, gastric ulcer, duodenitis or ulcer) with H. pylori infection should be treated accordingly.
(5) Course of treatment: the duration of medical treatment requires more than 3 months, and generally requires 2 to 4 weeks to show efficacy. A small number of patients with severe reflux who fail medical treatment can be considered for anti-reflux surgery.
5. Drug-induced cough
The most common drug causing chronic cough is a class of antihypertensive drugs, namely angiotensin-converting enzyme inhibitors (ACEI), commonly known as captopril and fosinopril. The mechanism lies in the ability of such drugs to cause the aggregation of substances such as kinins and prostaglandins in the pulmonary vascular bed.
Treatment: Switch to other types of antihypertensive drugs.
6. Allergic cough (AC)
(1) Definition: Certain patients with chronic cough with certain characteristic clinical manifestations and effective treatment with antihistamines and glucocorticoids, but who cannot be diagnosed with asthma, allergic rhinitis or eosinophilic bronchitis, define this type of cough as AC.
(2) Clinical manifestations: irritating dry cough, mostly paroxysmal, daytime or nighttime cough, easily induced by fumes, dust, cold air, and speech, often accompanied by a tickling throat. Ventilation is normal, and the percentage of eosinophils on induced sputum cytology is not high.
(3) Diagnostic criteria (for reference): chronic cough; normal pulmonary ventilation function and negative airway hyperresponsiveness test; one of the following indications.
(i) history of exposure to allergic substances.
② Positive skin allergen skin test.
(iii) elevated serum total IgE or specific IgE.
(4) Increased cough sensitivity; exclusion of chronic cough caused by cough variant asthma, eosinophilic bronchitis and postnasal drip syndrome; effective treatment with antihistamines and/or glucocorticoids.
(4) Treatment: second-generation antihistamines and/or inhaled glucocorticoids may be considered.