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, and the extensive use of antibacterial drugs is ineffective. Many patients have been misdiagnosed as “chronic bronchitis” or “bronchiectasis” for a long time.
As people become more concerned about cough, various studies on the causes of cough and its treatment have been conducted in Europe and the United States in the past 20 years, which have basically clarified the common causes of chronic cough and established guidelines for the diagnosis and treatment of cough in recent years. In China, clinical studies on the etiology and treatment of cough have been conducted in recent years, and preliminary results have been obtained.
In order to further standardize the diagnosis and treatment of acute and chronic cough in China and to strengthen clinical and basic research on cough, the Asthma Group of the Chinese Medical Association’s Division of Respiratory Diseases organized relevant experts to formulate the Guidelines for the Diagnosis and Treatment of Cough (draft) with reference to clinical research findings on cough at home and abroad, in order to provide scientific diagnosis and effective treatment for different types of cough.
Classification and etiology of cough
Cough is usually classified into 3 categories according to the duration: acute, subacute and chronic cough. Acute cough lasts < 3 weeks, subacute cough 3-8 weeks, and chronic cough > 8 weeks.
Other causes include acute bronchitis, acute sinusitis, allergic rhinitis, acute attacks of chronic bronchitis, bronchial asthma (asthma), etc. The most common cause of acute cough is the common cold.
The most common causes of subacute cough are post-cold cough (also known as post-infectious cough), bacterial sinusitis, and asthma.
Chronic cough Chronic cough has many causes and is usually divided into two categories:
One category is those with definite lesions on initial X-ray chest radiographs, such as pneumonia, tuberculosis, and lung cancer. The other group 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 etiology (chronic cough for short).
The common causes of chronic cough are cough variant asthma (CVA), postnasal drip syndrome (PNDs), eosinophilic bronchitis (EB), and gastroesophageal reflux cough (GERC), which account for 70% to 95% of chronic cough in respiratory medicine clinics. Other etiologies are less common, but have a wide spectrum, such as chronic bronchitis, bronchiectasis, endobronchial tuberculosis, allergic cough (AC), and psychogenic cough.
History and ancillary examinations
Careful history taking is important for etiologic diagnosis and can narrow down the diagnosis of chronic cough and allow for preliminary diagnosis and treatment or selection of relevant tests based on the clues provided by the present history.
Pay attention to the nature, sound, rhythm and duration of coughing, triggering or aggravating factors, postural effects, and concomitant symptoms. Understanding the quantity, color, odor and properties of coughing sputum is of great value for diagnosis. In cases of high sputum volume and purulent sputum, respiratory tract infections should be considered first. The diagnosis of asthma is suggested when the exhalation croup is detected on examination, and if the inspiratory croup is detected, the diagnosis of central lung cancer or endobronchial tuberculosis should be alerted.
Related ancillary tests
Induced sputum examination was first used for the diagnosis of bronchial lung cancer. Induced sputum cytology examination can significantly increase the positive rate of cancer cells, and is even the only diagnostic method for some early stage lung cancers. Eosinophil elevation in cytology is the main indicator for the diagnosis of EB. Sputum induction is often performed by ultrasonic nebulization of hypertonic saline.
The hypertonic saline induced sputum test is performed as follows.
Patients are induced to cough up sputum by ultrasonic nebulized inhalation of hypertonic saline to detect the degree and type of airway inflammation. The gradient hypertonic saline method is commonly used.
Reagent preparation: 3%, 4%, 5% hypertonic saline, 011% dithiothreitol (DTT), etc.
Apparatus: Ultrasonic nebulizer.
Methods of operation:
(1) Patients were allowed to inhale 400 μg of salbutamol 10 min before induction.
(2) Rinse mouth and blow nose with water before nebulization.
(3) Ultrasonic inhalation of 3% hypertonic saline for 15 min, and cough up sputum vigorously into the culture dish.
(4) If the patient has no sputum or insufficient sputum, switch to 4% hypertonic saline and continue nebulization for 7 min.
(5) If the patient has no sputum or insufficient sputum, continue nebulization with 5% hypertonic saline for 7 min and then terminate the induction procedure.
(6) Sputum treatment: Sputum was weighed, added 4 times the volume of 011% DTT and mixed thoroughly, water bath at 37℃ for 10 min, centrifuged to precipitate the cells, and counted the total number of cells. Smear the sediment, stain with hematoxylin eosin (HE), and count the cells.
Caution:
(1) Hypertonic saline sputum induction is not recommended for patients with severe asthma Chinese Journal of Practical Internal Medicine, Vol. 26, No. 13, July 2006・977・. When the percentage of forceful expiratory volume in the first second (FEV1, % of expected value) is < 70%, the patient should be treated with natural coughing sputum or isotonic saline induction.
(2) Relevant resuscitation equipment and drugs must be prepared before induction, and the patient’s performance should be closely observed during induction, and pulmonary function should be monitored if necessary.
X-ray chest radiographs can determine the location, extent and morphology of the lung lesion, and even its nature, and make a preliminary diagnosis to guide empirical treatment and correlative examinations. X-ray chest radiographs are recommended as a routine examination for chronic cough, and if an organic lesion is found, the relevant tests are selected according to the characteristics of the lesion; if there is no obvious lesion on the X-ray chest radiograph, the examination is performed according to the chronic cough diagnostic procedure (see Chronic Cough Diagnostic Procedure). Chest CT is useful for detecting anterior and posterior mediastinal lung lesions, small intrapulmonary nodules, enlarged mediastinal lymph nodes and smaller masses in the marginal lung fields. High-resolution CT is helpful in diagnosing early interstitial lung disease and atypical bronchiectasis.
Pulmonary function tests Ventilation and bronchodilatation tests can help diagnose and identify airway obstructive diseases such as asthma, chronic bronchitis and large airway tumors. If routine lung function is normal, CVA can be diagnosed by an excitation test.
Fiberoptic bronchoscopy can be used to diagnose lesions in the tracheal lumen, such as bronchopulmonary cancer, foreign bodies, and endotracheal tuberculosis.
Esophageal 24-h pH monitoring is the most effective way to diagnose GERC. By dynamically monitoring the change of esophageal pH, six parameters such as the number of times of 24-h esophageal pH < 4, the longest reflux time, and the percentage of esophageal pH < 4 in the monitoring time are obtained, and finally the degree of reflux is expressed by Demeester score. During the examination, reflux-related symptoms were recorded in real time to obtain the correlation probability (SAP) between reflux and cough symptoms, and to clarify the relationship between reflux phase and cough.