Cough is a protective reflex that prevents aspiration and expels particles and irritants from the airway. However, it can become uncontrolled or disabling and is one of the most common symptoms prompting physician visits. (See also Cough in Children.)
Likely causes of cough (see table Some Causes of Cough) differ depending on whether the symptom is acute (present < 8 weeks) or chronic (1, 2).
In acute cough, the most common causes are
In chronic cough, the most common causes are
Postnasal drip
COPD (chronic obstructive pulmonary disease)
Airway hyperresponsiveness after resolution of a viral or bacterial respiratory infection (ie, postinfection cough)
Angiotensin-converting enzyme (ACE) inhibitors and, less often, angiotensin II receptor blockers
The causes of cough in children are similar to those in adults, but asthma may be more common in children. Foreign body aspiration, uncommon in adults except in those with impaired development, dementia, or swallowing dysfunction, is more common in children.
Purely psychogenic cough is rare and is a diagnosis of exclusion. However, patients with chronic cough may develop a secondary reflex or psychogenic component to their cough. Also, protracted coughing may injure the bronchial mucosa, which may trigger more coughing.
General references
1. Iyer VN, Lim KG: Chronic cough: an update. Mayo Clin Proc 88(10):1115–1126, 2013. doi:10.1016/j.mayocp.2013.08.007
2. Morice AH, Millqvist E, Bieksiene K, et al: ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. Eur Respir J 55(1): 1901136, 2020. doi: 10.1183/13993003.01136-2019
Evaluation of Cough
History
History of present illness should cover the duration and characteristics of the cough (eg, whether dry or productive of sputum or blood, and whether it is accompanied by dyspnea, chest pain, or both). Asking about precipitating factors (eg, cold air, strong odors) and the timing of the cough can be revealing (eg, cough occurring primarily when recumbent may suggest gastroesophageal reflux or heart failure as a cause).
Review of systems should seek symptoms of possible cause, including runny nose and sore throat (upper respiratory infection [URI], postnasal drip); fever, chills, and pleuritic chest pain (pneumonia); night sweats and weight loss (tumor, tuberculosis [TB]); heartburn (gastroesophageal reflux); and difficulty swallowing or choking episodes while eating or drinking (aspiration).
Past medical history should note recent respiratory infections (ie, within previous 1 to 2 months); history of allergies, asthma, COPD (chronic obstructive pulmonary disease), and gastroesophageal reflux disease; risk factors for (or known) TB or HIV infection; and smoking history. Drug history should specifically include use of angiotensin-converting enzyme (ACE) inhibitors. Patients with chronic cough should be asked about exposure to potential respiratory irritants or allergens and travel to or residence in regions with endemic fungal illness.
Physical examination
Vital signs should be reviewed for the presence of tachypnea and fever.
General examination should look for signs of respiratory distress and chronic illness (eg, wasting, lethargy).
Examination of the nose and throat should focus on appearance of the nasal mucosa (eg, color, congestion) and presence of discharge (external or in posterior pharynx). Ears should be examined for foreign bodies, masses, or signs of infection.
The cervical and supraclavicular areas should be inspected and palpated for lymphadenopathy.
A full lung examination is done, particularly including adequacy of air entry and exit; symmetry of breath sounds; and presence of crackles, wheezes (diffuse or localized), or both. Signs of consolidation (eg, egophony, dullness to percussion) should be sought.
Red flags
The following findings are of particular concern:
Dyspnea
Hemoptysis
Weight loss
Persistent fever
Risk factors for TB or HIV infection
Interpretation of findings
Some findings point to particular diagnoses (1—see table Some Causes of Cough).
Other important findings are less specific. For example, the color (eg, yellow, green) and thickness of sputum do not help differentiate bacterial from other causes. Wheezing may occur with several causes. Hemoptysis in small amounts may occur with severe cough of many etiologies, although larger amounts of hemoptysis suggest bronchitis, bronchiectasis, TB, or primary lung cancer. Fever, night sweats, and weight loss may occur with many chronic infections as well as with cancer.
Testing
Pulse oximetry and chest x-ray should be done in patients with red flag findings of dyspnea or hemoptysis and patients in whom suspicion of pneumonia or other parenchymal lung disease is high. A chest x-ray and testing for TB and HIV infection should be done in patients with weight loss or risk factors for those infections.
For many patients without red flag findings, clinicians can base the diagnosis on history and physical examination findings and begin treatment without testing. For patients without a clear cause but no red flag findings, many clinicians empirically begin treatment for postnasal drip (eg, antihistamine and decongestant combinations, nasal corticosteroid sprays, or nasal muscarinic antagonist sprays), airway hyperreactivity (eg, inhaled corticosteroid or short-acting beta-adrenergic agonist), or gastroesophageal reflux disease (eg, proton pump inhibitors, H2 blockers). An adequate response to these interventions usually precludes the need for further evaluation.
A chest x-ray should be done in patients with chronic cough in whom presumptive treatment is ineffective. If the x-ray findings are unremarkable, many clinicians sequentially test for asthma (pulmonary function tests with methacholine challenge if standard spirometry is normal), sinus disease (sinus CT), and gastroesophageal reflux disease (esophageal pH monitoring).
Sputum culture is helpful for patients with a possible indolent infection, such as pertussis, TB, or nontuberculous mycobacterial infection.
Chest CT and possibly bronchoscopy should be done in patients in whom lung cancer or another bronchial tumor is suspected (eg, patients with a long smoking history, nonspecific constitutional signs) and in patients in whom empiric therapy has failed and who have inconclusive findings on preliminary testing.
Evaluation reference
1. Morice AH, Millqvist E, Bieksiene K, et al: ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. Eur Respir J 55(1): 1901136, 2020. doi: 10.1183/13993003.01136-2019
Treatment of Cough
Treatment is management of the cause (1).
There is little evidence to support the use of cough suppressants or mucolytic agents. Coughing is an important mechanism for clearing secretions from the airways and can assist in recovery from respiratory infections. Therefore, although patients often expect or request cough suppressants, such treatment should be given with caution and reserved for patients with a URI and for patients receiving therapy for the underlying disorder for whom cough is still troubling. Cough suppressants may help some patients with chronic cough who have a reflex or psychogenic component to their cough or who develop bronchial mucosal injury.
AntitussivesDextromethorphan, a congener of the opioid levorphanol, is effective as a tablet or syrup. CodeineBenzonatate, a congener of tetracaine that is available in liquid-filled capsules,.
Expectorantsbronchiectasis or cystic fibrosis. Ensuring adequate hydration may facilitate expectoration, as may inhalation of steam, although neither technique has been rigorously tested.
Topical treatments,
Protussives, which stimulate cough, are indicated for such disorders as cystic fibrosis and bronchiectasis, in which a productive cough is thought to be important for airway clearance and preservation of pulmonary function. DNase or hypertonic saline is given in conjunction with chest physical therapy and postural drainage to promote cough and expectoration. This approach is beneficial in cystic fibrosis but not in most other causes of chronic cough.
Bronchodilators,
Treatment reference
1. Morice AH, Millqvist E, Bieksiene K, et al: ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. Eur Respir J 55(1): 1901136, 2020. doi: 10.1183/13993003.01136-2019
Key Points
Danger signs include respiratory distress, chronic fever, weight loss, and hemoptysis.
Clinical diagnosis is usually adequate.
Occult gastroesophageal reflux disease should be remembered as a possible cause.
Antitussives and expectorants should be used selectively.
