Cough is a reflex action of the throat or trachea, which can remove foreign bodies or secretions from the respiratory tract. Cough is one of the common symptoms of respiratory diseases.
Based on the duration of a cough, it can be classified as acute cough (＜3 weeks), subacute cough (3 to 8 weeks) and chronic cough (＞8 weeks).
Acute cough is mostly caused by the common cold, acute tracheobronchitis or the acute attacks of chronic respiratory diseases such as chronic bronchitis, bronchial asthma and bronchodilatation, or by exposure to environmental or occupational factors.
Subacute cough is most commonly a post-infection symptom, or the early stage of chronic cough. A prolonged infectious cough is also another cause of subacute cough, which needs antimicrobial treatment.
Cough after novel coronavirus infection is a subacute cough. The cough with a small amount of sputum after a novel coronavirus infection (for a patient with mild symptoms, not one with COVID-19) can last for three to eight weeks.
Infection-caused cough occurs after the upper respiratory tract becomes infected, and shows symptoms of irritant dry cough or cough with a small amount of white mucus sputum. The patient’s chest x-ray shows no abnormalities and the lung function is also normal. Subacute cough is self-limiting and requires only supportive treatment.
The causes of chronic cough
The main causes of chronic cough include cough variant asthma, upper airway cough syndrome, eosinophilic bronchitis, gastroesophageal reflux and allergic reaction. These conditions account for 70 to 95 percent of chronic cough causes.
In addition, chronic bronchitis, bronchiectasis, tracheobronchial tuberculosis, drug-induced cough, bronchogenic cancer and psychogenic cough can also cause chronic cough.
To find the cause of chronic cough is of great importance in clinical diagnosis and treatment.
The doctor will inquire about the patient's medical history, including conditions of the ear, nose, throat and pharynx, symptoms of digestive disorders, exposure to occupational and living environments, and so on.
Diseases causing chronic cough and their treatment
1.Upper airway cough syndrome is a chronic cough caused by nasitis, nasosinusitis, pharyngo-laryngitis chronica, chronic tonsillitis, nasal polyp and other upper airway diseases. Postnasal drip syndrome refers to the syndrome with cough as the main manifestation due to secretions flowing back to the back of the nose and throat, and even into the glottis or trachea caused by nasal diseases.
The symptoms of the upper airway cough syndrome and postnasal drip syndrome include chronic cough or cough without sputum, discomfort with throat itching or nasal itching at the upper end of the trachea, nasal congestion, runny nose, sneezing or sinusitis symptoms, and so on. Most patients have a history of upper respiratory tract infection before developing these symptoms.
Treatment: The treatment should mainly target nasopharyngeal diseases.
2.Cough variant asthma is a special type of asthma, and cough is its only or at least its main symptom. The patient has no obvious wheezing, shortness of breath and other symptoms but has airway hyperreactivity with symptoms of irritant dry cough, nocturnal cough and aggravated cough caused by cold, cold air, dust and oil smoke.
Treatment: The first option is inhalation of corticosteroid or a combination of corticosteroid/long-acting bronchodilators. The leukotriene receptor antagonist is effective against mild cough variant asthma.
3. Eosinophilic bronchitis is a non-asthmatic bronchitis characterized by acidogenic granulocytic infiltration in the airways and is also an important cause of chronic cough. The patients usually have chronic irritant cough, dry cough, and less phlegm; most cough in daytime and few cough at night. Cough among some patients arises from their sensitivity to oil smoke, dust, odor or cold air.
Treatment: Glucocorticoids are effective in the treatment of eosinophilic bronchitis. Patients have the option of using inhaled corticosteroid (use for more than eight weeks) or oral corticosteroid (Prednisone 10 ~ 20 mg/day, for three to five days) for treatment.
4. Gastroesophageal reflux cough is caused by stomach acid and other stomach contents flowing back into the esophagus and even up to the throat, which is also one of the common causes of chronic cough.
Patients with gastroesophageal reflux cough may have a burning sensation behind the sternum, sour regurgitation and chest distress, or may not show any of these gastrointestinal symptoms except for cough. Chronic cough may be the only symptom of the gastroesophageal reflux cough. Diagnosis of this disease requires gastroscopy and a gastroesophageal reflux test.
Treatment: The patients can take acid suppressors combined with gastric motility agents for more than eight weeks. Additionally, the patients should avoid eating too much, eating before bed time, eating acidic, spicy and greasy foods, drinking coffee and acidic beverages, smoking and strenuous exercise.
Allergic cough is caused by the response of patients’ allergic constitution to certain substances. The symptoms are usually irritant dry cough, mostly paroxysmal cough. Exposure to smoke, dust and cold air or speaking usually induces cough and throat itchiness. These patients have a normal pulmonary function and a low proportion of eosinophilic cells, while positive allergens can be detected in allergen tests.
Treatment: Anti-allergy and supportive treatment for cough should be taken. Patients with severe allergic cough need to undergo inhaled corticosteroid therapy for more than four weeks. In the early stage of cough, patients can also receive short-term oral glucocorticoid therapy for three to five days.
Since the causes of chronic cough are all chronic diseases, patients with chronic cough should be regularly reviewed and given standardized treatment.