Cough is an important defense mechanism and is also the most common respiratory symptom. Frequent coughing may cause a variety of complications. In the United States (1991), 24 million cough patients visited internal medicine clinics, and the prevalence of chronic cough among nonsmokers ranged from 14 to 23%, with an average of 7.4 physician visits per patient with chronic cough and an average of 8.5 examinations per patient.
Clinically, the causes of cough are numerous and wide-ranging, especially in patients with chronic cough with no obvious abnormalities on chest imaging. Many patients are misdiagnosed as “chronic bronchitis” or “bronchiectasis” for a long time and are treated ineffectively with a large number of antibacterial drugs, and often undergo various tests repeatedly due to unclear diagnosis, which not only increases patients’ pain but also aggravates their financial burden. This not only increases the pain of patients, but also increases their economic burden. Due to unclear diagnosis, these patients are either repeatedly treated with various antibiotics or repeatedly undergo various meaningless tests, resulting in a great waste of medical resources.
Overseas clinical studies and guidelines on the management of cough
In 1981, Irwin et al. first developed a protocol for the diagnosis and management of chronic cough based on the anatomical mechanism of the cough reflex, which was clinically effective and included history, physical examination, chest and sinus films, and pulmonary function. Since the establishment of the Irwin diagnostic protocol, it has played an important role in the study of the etiology of chronic cough and has basically clarified the common causes of chronic cough.
With the increased emphasis on the diagnosis and management of cough, guidelines for cough-related diagnosis and management have been developed in the United States, Japan and Europe in 1998, 2001 and 2004. The American College of Chest Physicians published the 1998 and 2006 revised guidelines for the management of cough. Compared with other national cough guidelines, the ACCP cough guidelines are more evidence-based, rich in content and extensive, and provide very detailed descriptions of cough defense mechanisms, cough causes, pathogenesis, diagnosis, treatment management, and complications of cough, making them ideal for use by respiratory physicians and researchers. Modifications.
1. The focus is mainly on the diagnosis and treatment of cough in children and adults, with little discussion on the defense mechanisms of cough.
2. The description and narrative of the evidence-based approach is more rigorous in the different sections on cough.
3. All chapters are expanded and updated as appropriate. New content has been added, including: non-asthmatic eosinophilic bronchitis (NAEP), acute bronchitis, airway disease, and aspiration cough secondary to pharyngeal disease. Cough-related occupational and environmental factors, tuberculosis and other infections, cough in dialysis patients, rare causes of cough, unexplained cough, which is referred to as idiopathic cough, fast cough management programs, evaluation of cough severity and efficacy in clinical studies. and directions for further research.
The committee recommended this approach because the relative probability of most causes of chronic cough (both single and compound) is known, and the sensitivity and specificity of most tests are known. It is also well understood what treatment is appropriate for what cause and when it is effective. Prospective studies and strategic theoretical analyses suggest that empirical treatment of the common causes of chronic cough is the key to successful diagnosis and management.
Since cough is often not caused by a single cause, a continuous holistic evaluation is essential. Therefore, a continuous holistic evaluation is necessary. Significant relief of cough is often a necessary sign of successful treatment. This protocol, recommended by the committee, is also applicable to acute or subacute cough.
5. To reduce confusion in the diagnosis of cough, some of the commonly used terms have been added and modified, such as upper respiratory cough syndrome (UACS) instead of postnasal drip syndrome (PNDS).
Postnasal drip syndrome (PNDS) is caused by lesions of the nose, nasopharynx and sinuses, whose secretions flow back into the posterior pharyngeal wall, epiglottis or even the trachea, resulting in cough. It can be a major cause of both acute cough due to the common cold and chronic cough. PNDS secondary to various sinus infections is considered the most common cause of chronic cough, but according to the literature and in actual clinical work, the diagnosis of postnasal drip syndrome is low and varies widely among hospitals, analyzing the reasons for.
1) Although postnasal drip lesions involve the anatomical sites of the nose, sinuses, and throat and belong to otorhinolaryngology, patients with cough mostly consult internal medicine and respiratory specialties, and specialists lack sufficient experience and awareness for the diagnosis and treatment of this type of cough;
2) Clinically, postnasal drip syndrome relies heavily on the patient’s description, such as the sensation of something dripping into the throat, pronounced nasal sounds, and frequent throat-clearing movements. Signs suggestive of PND are the presence of mucous or mucopurulent secretions in the nasopharynx or oropharynx, sometimes with localized cobblestone changes in the mucosa. However, unlike cough variant asthma, which can be diagnosed by pulmonary ventilation or provocation tests, there is no specific way to confirm the diagnosis of PND, to quantify postnasal drip, or to directly prove whether it is the cause of the cough. The diagnosis of PNDS-associated cough is currently based on a combination of clinical features, including symptoms, physical examination, imaging, and response to specific treatments.
Improvement and relief of cough symptoms after specific treatment is required to confirm the diagnosis of PNDS-associated cough. Approximately 20% of patients with PNDS-associated cough are unaware of the presence of PND and its relationship to cough, and approximately 50% of patients with PNDS have no symptoms of postnasal drip, making PNDS even less diagnostic as a cause of chronic cough and difficult to differentiate from pharyngitis;
3) In different patients with cough, symptoms associated with rhinitis are often more frequent than those of postnasal drip, which can cause cough not only through post-secretory drip, but also through vagal reflexes and physical effects of airway inflammation. The key question is whether the mechanism of this type of cough is a direct effect of PND or whether PND causes inflammation and hyperreactivity in the upper airways and stimulates cough receptors and other multiple factors. Therefore, the ACCP Cough Guidelines Committee has proposed the concept of upper respiratory cough syndrome (UACS).
The term upper respiratory cough syndrome is more appropriate than PNDS in cases where cough is combined with the above mentioned conditions. Thus, UACS will henceforth replace PNDS.
The ACCP Cough Guidelines Committee recommends that for patients with cough associated with upper airway abnormalities, the committee considers upper airway syndrome (UACS) to be more accurate and an alternative to postnasal drip syndrome (PNDS). (Degree of evidence, expert recommendation; helpfulness, true; recommendation, E/A)
Domestic clinical studies on cough and related diagnosis and treatment guidelines
Clinical studies on the diagnosis and management of cough etiology have also been conducted in China 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 strengthen clinical and basic research on cough, the Asthma Group of the Chinese Medical Association’s Respiratory Diseases Branch organized relevant experts to jointly develop the Guidelines for the Diagnosis and Treatment of Cough (draft), taking into account the results of domestic and foreign clinical studies on cough.
Common causes of chronic cough
Cough variant asthma (CVA), postnasal drip syndrome (PNDs), eosinophilic bronchitis (EB), and gastroesophageal reflux cough (GERC). These causes account for 70% to 95% of chronic cough in respiratory medicine internal medicine clinics.
Other causes of chronic cough
Other etiologies are less common but are widely involved, such as chronic bronchitis, bronchiectasis, endobronchial tuberculosis, allergic cough (AC), and psychogenic cough.
History and physical examination
Careful history taking plays an important role in etiologic diagnosis. A detailed history and physical examination can narrow the diagnosis of chronic cough and lead to a preliminary diagnosis for treatment or selection of relevant tests based on the clues provided by the present history. Pay attention to the nature, tone, rhythm and duration of coughing, as well as triggering or aggravating factors, postural influences, and concomitant symptoms, etc. 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 bronchial asthma is suggested when exhalation croup is detected on physical examination, and if inspiratory croup is detected, central lung cancer or endobronchial tuberculosis should be alerted.
Related auxiliary tests
1. Induced sputum cytology: elevated eosinophils on cytology is the main indicator for the diagnosis of eosinophilic bronchitis. The induction of sputum is performed by ultrasonic nebulized inhalation of hypertonic saline.
2.Imaging: X-ray chest radiographs can determine the site, extent and morphology of lung lesions, and even their nature, yielding a preliminary diagnosis to guide empirical treatment and relevant chamber examinations. X-ray chest radiographs can be used as a routine examination for chronic cough, and if organic lesions are found, relevant examinations are selected according to the characteristics of the lesions.
3. Chest CT examination: It helps to detect anterior and posterior mediastinal lung lesions, small nodules in the lungs, enlarged lymph nodes in the mediastinum and smaller masses in the marginal lung fields. High-resolution CT helps to diagnose early interstitial lung disease and atypical bronchiectasis.
4. Ventilation function and bronchodilatation test: It can help to diagnose and identify airway obstructive diseases such as asthma, chronic bronchitis and large airway tumors. Routine lung function is normal and a positive excitation test helps to diagnose CVA .
5.Fiber bronchoscopy: It can effectively diagnose lesions in the tracheal lumen, such as bronchopulmonary carcinoma, foreign body, and endotracheal tuberculosis.
6.Esophageal 24-h pH monitoring: to determine the presence of gastro-esophageal reflux is currently the most effective method for diagnosing GERC. The change of esophageal pH is monitored dynamically to obtain 24 h esophageal pH.