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Cough is an explosive expiratory maneuver that is reflexively or deliberately intended to clear the airways. Coughing is a normal response to the presence of mucus or other foreign material in the airway or upper airway, but persistent coughing is annoying and generally indicates irritation of the pulmonary airways. It is the 5th most common symptom prompting patients to visit their physician. Awareness of cough varies considerably. A cough that appears suddenly, interferes with sleep, or causes musculoskeletal chest wall pain can be distressing. A cough that develops over decades (eg, in a smoker with mild chronic bronchitis) may be hardly noticeable or may be considered normal by the patient.
Etiology
Likely etiologies of cough differ depending on whether the symptom is acute (< 3 wk) or chronic.
Acute cough is most often caused by a URI, especially the common cold. Other causes include pneumonia; postnasal drip resulting from rhinitis or sinusitis that can be allergic, viral, or bacterial in origin; and COPD exacerbations. Cough may rarely be the only presenting symptom of pulmonary embolus. In the elderly, acute cough may signify aspiration or heart failure.
Chronic
cough in smokers is most often caused by chronic bronchitis, defined as the presence of productive cough over ≥ 3 mo for > 2 yr consecutively. Compression of upper airways by tumor is much less common but should always be considered. The most common causes regardless of smoking history include postnasal drip syndrome, gastroesophageal reflux disease (GERD), asthma (cough-variant asthma), and use of ACE inhibitors. Less common causes include eosinophilic bronchitis (characterized by sputum eosinophilia without airway hyperresponsiveness) and bronchiectasis. The causes of chronic cough in children are similar to those of adults, but aspiration and pertussis must also be considered. Tracheobronchitis after a URI is a common cause of cough but rarely lasts > 3 mo after the infection. Rarely, impacted cerumen or a foreign body in the external auditory canal triggers reflex cough through stimulation of the auricular branch of the vagus nerve. Psychogenic cough is even rarer and is a diagnosis of exclusion.
Evaluation
History:
URI and sinus symptoms suggest postnasal drip syndrome, but postnasal drip often causes cough without other symptoms. Heartburn, hoarseness, and chronic nocturnal or early morning cough, especially if no other symptoms are present, suggests GERD. Cough after exposure to dusts or allergens suggests cough-variant asthma. Chronic cough with production of purulent sputum in smokers suggests chronic bronchitis. A change in cough in these patients may, however, be an early manifestation of lung cancer. Cough productive of gritty sputum may signify broncholithiasis. Copious volumes of sputum suggest alveolar cell carcinoma.
Physical examination:
Physical examination should focus on signs of sinusitis, rhinitis, and postnasal drip. Lung auscultation during cough may help detect lung sounds suggestive of asthma (wheezing) or bronchiectasis (rhonchi). Examination of the ears can detect triggers of reflex cough.
Testing:
Most patients with acute or chronic cough without clear etiology by history and examination can be treated empirically for postnasal drip syndrome, GERD, or asthma based on clinical judgment; an adequate response to these therapeutic interventions precludes the need for further testing. A chest x-ray can be performed but usually is not helpful. Patients with chronic cough and inadequate responses to interventions can undergo more extensive testing for asthma (pulmonary function tests with methacholine challenge, sinus disease [sinus CT], or GERD [esophageal pH monitoring]). Bronchoscopy should be performed in selected patients in whom lung cancer or other bronchial tumor is suspected.
Treatment
Treatment is management of the underlying cause. Little evidence exists to support the use of cough suppressants or mucolytic agents for cough, but patients often expect or request such treatment, and multiple options exist. Coughing is an important mechanism for clearing secretions from the airways and can assist in treating respiratory infections. Therefore, cough suppression in infectious conditions should be done with caution. Nonspecific treatments for cough should be reserved as much as possible for patients with a URI and for those receiving therapy for the underlying cause but for whom cough is still troubling.
Antitussives depress the medullary cough center ( dextromethorphan and codeine ) or anesthetize stretch receptors of vagal afferent fibers in bronchi and alveoli ( benzonatate ). Dextromethorphan , a congener of the narcotic levorphanol , is effective as a tablet or syrup at a dose of 15 to 30 mg 1 to 4 times/day for adults or 0.25 mg/kg qid for children. Codeine has antitussive, analgesic, and sedative effects, but dependence is a potential problem, and nausea, vomiting, constipation, and tolerance are common adverse effects. Usual doses are 10 to 20 mg po q 4 to 6 h as needed for adults and 0.25 to 0.5 mg/kg qid for children. Other opioids (eg, hydrocodone, hydromorphone , methadone , morphine ) have antitussive properties but are avoided because of high potential for dependence and abuse. Benzonatate , a congener of tetracaine in liquid-filled capsules, is effective at a dose of 100 to 200 mg po tid. Inhaled ipratropium is not generally considered an antitussive but may be of use in some patients with acute cough due to URI.
Expectorants are thought to decrease viscosity and facilitate expectoration, or coughing up, of secretions, but are of limited benefit. Guaifenesin (200 to 400 mg po q 4 h in syrup or tablet form) is most commonly used because it has no serious adverse effects, but multiple expectorants exist, including bromhexine, ipecac, saturated solution of potassium iodide (SSKI), and domiodol. Aerosolized expectorants, which include isoproterenol , beclomethasone , N- acetylcysteine , and deoxyribonuclease (DNase), are generally reserved for hospital-based treatment of cough in patients with bronchiectasis or cystic fibrosis. Ensuring adequate hydration may facilitate expectoration, as may inhalation of steam, although neither has been rigorously tested.
Topical treatments, such as acacia, licorice, glycerin, honey, and wild cherry cough drops or syrups (demulcents), are locally and perhaps emotionally soothing but are not supported by scientific evidence.
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 seems to be beneficial in cystic fibrosis but not in most other causes of chronic cough.
Bronchodilators, such as albuterol and ipratropium or inhaled corticosteroids, can be effective for cough after URI and in cough-variant asthma.
Last full review/revision November 2005
Content last modified November 2005
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