The cough reflex serves a protective function by preventing foreign material from entering the respiratory tract and by facilitating the expulsion of mucus from the airways. Cough is triggered by stimulation of sensory receptors within the respiratory tract, whose afferent impulses activate a brain stem cough center.1 Persistent cough with no apparent benefit is a maladaptive response that results in significant discomfort.
Cough is the most common complaint for which outpatients seek medical attention in the United States.2 Acute cough, commonly caused by a viral upper respiratory tract infection, is usually self-limited. Other causes, such as congestive heart failure, pneumonia, pulmonary embolism, and endobronchial foreign body or malignancy, may need to be considered in the appropriate clinical setting. Cough of 3 to 8 weeks' duration is termed "subacute." Chronic cough is defined as cough that persists for more than 8 weeks.3
In this article, we will review the evaluation and treatment of chronic cough in adults. We will focus on its most common causes: postnasal drip syndrome, recently renamed upper airway cough syndrome (UACS); asthma; non-asthmatic eosinophilic bronchitis; and gastroesophageal reflux disease (GERD).4
Multiple prospective studies have demonstrated that a systematic evaluation of chronic cough leads to successful diagnosis in most cases.3,5-7 In the vast majority of patients who are nonsmokers, are not receiving angiotensin-converting enzyme (ACE) inhibitors, and have normal or stable chest radiographic findings, chronic cough can be explained by 4 causes, either alone or in combination: UACS, asthma, non-asthmatic eosinophilic bronchitis, and GERD.3-7 If a specific cause is determined, treatment is usually very effective.
In at least 25% of patients, multiple causes of chronic cough exist simultaneously, and a partial response to specific therapy may indicate that only one of the causes has been addressed. The American College of Chest Physicians (ACCP) has recently published updated guidelines for the management of cough, which include a diagnostic algorithm.4 We provide a simplified Algorithm for evaluating chronic cough, as well as a summary of highlights from the new ACCP guidelines (Table 1).
It is essential to perform a meticulous history taking and physical examination. Because UACS, asthma/ non-asthmatic eosinophilic bronchitis, and GERD may all present with cough as the sole symptom, a high index of suspicion is required. In the absence of associated symptoms, an empiric drug trial is often indicated in the evaluation of chronic cough. A chest radiograph should be considered in any adult who presents with chronic cough.
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•Irwin RS, Baumann MH, Bolser DC, et al. Diagnosis and management of cough: ACCP evidence-based clinical practice guidelines. Chest. 2006;129 (suppl):1S-292S.