COUGH

ESSENTIAL INQUIRIES

• Age.

• Duration of cough.

• Dyspnea (at rest or with exertion).

• Tobacco use history.

• Vital signs (heart rate, respiratory rate, body temperature).

• Chest examination.

• Chest radiography when unexplained cough lasts more than 3–6 weeks.

General Considerations 

Cough adversely affects personal and work-related interactions, disrupts sleep, and often causes discomfort of the throat and chest wall. Most people seeking medical attention for acute cough desire symptom relief; few are worried about serious illness. Cough results from stimulation of mechanical or chemical afferent nerve receptors in the bronchial tree. Effective cough depends on an intact afferent–efferent reflex arc, adequate expiratory and chest wall muscle strength, and normal mucociliary production and clearance.

Clinical Findings 

A. Symptoms

Distinguishing acute (< 3 weeks), persistent (3–8 weeks), and chronic (> 8 weeks) cough illness syndromes is a useful first step in evaluation. Postinfectious cough lasting 3–8 weeks has also been referred to as subacute cough to distinguish this common, distinct clinical entity from acute and chronic cough.

1. Acute cough—In healthy adults, most acute cough syndromes are due to viral respiratory tract infections. Additional features of infection such as fever, nasal congestion, and sore throat help confirm the diagnosis. Dyspnea (at rest or with exertion) may reflect a more serious condition, and further evaluation should include assessment of oxygenation (pulse oximetry or arterial blood gas measurement), airflow (peak flow or spirometry), and pulmonary parenchymal disease (chest radiography). The timing and character of the cough have not been found to be very useful in establishing the cause of acute cough syndromes, although cough-variant asthma should be considered in adults with prominent nocturnal cough, and persistent cough with phlegm increases the patient’s likelihood of chronic obstructive pulmonary disease (COPD). The presence of post-tussive emesis or inspiratory whoop modestly increases the likelihood of pertussis, and the absence of paroxysmal cough decreases the likelihood of pertussis in adolescents and adults with cough lasting more than 1 week. Uncommon causes of acute cough should be suspected in those with heart disease (congestive heart failure [CHF]) or hay fever (allergic rhinitis) and those with environmental risk factors (such as farm workers).

2. Persistent and chronic cough—Cough due to acute respiratory tract infection resolves within 3 weeks in the vast majority of patients (over 90%). Pertussis infectionshould be considered in adolescents and adults who present with persistent or severe cough lasting more than 3 weeks. In selected geographic areas, the prevalence of pertussis approaches 20% when cough has persisted beyond 3 weeks, although the exact prevalence of pertussis is difficult to ascertain due to the limited sensitivity of diagnostic tests. 

When angiotensin-converting enzyme (ACE) inhibitor therapy, acute respiratory tract infection, and chest radiograph abnormalities are absent, the majority of cases of persistent and chronic cough are due to or exacerbated by postnasal drip, asthma, or gastroesophageal reflux disease (GERD). A history of nasal or sinus congestion, wheezing, or heartburn should direct subsequent evaluation and treatment, though these conditions frequently cause persistent cough in the absence of typical symptoms. Dyspnea at rest or with exertion is not commonly reported among patients with persistent cough. The report of dyspnea requires assessment for other evidence of chronic lung disease, CHF, or anemia.

Bronchogenic carcinoma is suspected when cough is accompanied by unexplained weight loss and fevers with night sweats, particularly in persons with significant tobacco or occupational exposures. Persistent and chronic cough accompanied by excessive mucus secretions increases the likelihood of COPD, particularly among smokers, or bronchiectasis in a patient with a history of recurrent or complicated pneumonia; chest radiographs are helpful in diagnosis.

B. Physical Examination

Examination can direct subsequent diagnostic testing for acute and persistent cough. Pneumonia is suspected when acute cough is accompanied by vital sign abnormalities (tachycardia, tachypnea, fever). Findings suggestive of airspace consolidation (rales, decreased breath sounds, fremitus, egophony) are significant predictors of communityacquiredpneumonia but are present in the minority of cases. Purulent sputum is associated with bacterial infections in patients with structural lung disease (eg, COPD, cystic fibrosis), but it is a poor predictor of pneumonia in the otherwise healthy adult. Wheezing and rhonchi are frequent findings in adults with acute bronchitis and do not represent adult-onset asthma in most cases.

Physical examination of patients with persistent cough should look for evidence of chronic sinusitis, contributing to postnasal drip syndrome or asthma. Chest and cardiac signs may help distinguish COPD from CHF. In patients with cough and dyspnea, a normal match test (ability to blow out a match from 25 cm away) and maximum laryngeal height > 4 cm (measured from the sternal notch to the cricoid cartilage at end expiration) substantially decrease the likelihood of COPD. Similarly, normal jugular venous pressure and no hepatojugular reflux decrease the likelihood of biventricular CHF.

  C. Diagnostic Studies

1. Acute cough—Chest radiography should be considered for any adult with acute cough who shows abnormal vital signs or in whom the chest examination is suggestive of pneumonia. The relationship between specific clinical findings and the probability of pneumonia is shown in Figure 2–1. In patients with dyspnea, pulse oximetry and peak flow help exclude hypoxemia or obstructive airway disease. However, a normal pulse oximetry value (eg, > 93%) does not rule out a significant alveolar–arterial (a–a) gradient when patients have effective respiratory compensation. During documented influenza outbreaks, the positive predictive value of the clinical diagnosis of influenza approaches 70% and usually obviates the usefulness of rapid diagnostic tests.

2. Persistent and chronic cough—Chest radiography is indicated when ACE inhibitor therapy–related and postinfectious cough are excluded by history or further diagnostic testing. If pertussis infection is suspected, testing should be performed using polymerase chain reaction on a nasopharyngeal swab or nasal wash specimen—keeping in mind that the ability to detect pertussis decreases as the duration of cough increases. When the chest film is normal, postnasal drip, asthma, and GERD are the most likely causes. The presence of typical symptoms of these conditions directs further evaluation or empiric therapy, though typical symptoms are often absent. Definitive procedures for determining the presence of each are available (Table 2–1). However, empiric treatment with a maximum-strength regimen for postnasal drip, asthma, or GERD for 2–4 weeks is one recommended approach since documenting the presence of postnasal drip, asthma, and GERD does not mean they are the cause of the cough illness. Alternative approaches to identifying patients who have corticosteroidresponsive cough include examining induced sputum for increased eosinophil counts (> 3%); measuring increased exhaled nitric oxide levels; or providing an empiric trial of prednisone, 30 mg daily for 2 weeks. Spirometry may help identify large airway obstruction in patients who have persistent cough and wheezing and who are not responding to asthma treatment. When empiric treatment trials are not helpful, additional evaluation with pH manometry, endoscopy, barium swallow, sinus CT or high-resolution chest CT may identify the cause.

Differential Diagnosis

A. Acute Cough

Acute cough may be a symptom of acute respiratory tract infection, asthma, allergic rhinitis, and CHF, as well as a myriad of other less common causes.

B. Persistent and Chronic Cough

Causes of persistent cough include environmental exposures (cigarette smoke, air pollution), pertussis infection, postnasal drip syndrome (or upper airway cough syndrome), asthma (including cough-variant asthma), GERD, COPD, bronchiectasis, eosinophilic bronchitis, tuberculosis or other chronic infection, interstitial lung disease, and bronchogenic carcinoma. COPD is a common cause of persistent cough among patients > 50 years of age. Persistent cough may also be psychogenic.

Treatment

A. Acute Cough

Treatment of acute cough should target the underlying etiology of the illness, the cough reflex itself, and any additional factors that exacerbate the cough. When influenza is diagnosed, treatment with amantadine, rimantadine, oseltamivir, or zanamivir is equally effective (1 less day of illness) when initiated within 30–48 hours of illness onset, although treatment is recommended regardless of illness duration when patients present with severe illness requiring hospitalization. Furthermore, in the setting of H1N1 influenza, neuraminidase inhibitors are the preferred treatment due to resistance to amantadine/rimantidine. In the setting of Chlamydia or Mycoplasma-documented infection or outbreaks, first-line antibiotics include erythromycin, 250 mg orally four times daily for 7 days, or doxycycline, 100 mg orally twice daily for 7 days. In patients diagnosed with acute bronchitis, inhaled b2-agonist therapy reduces severity and duration of cough in some patients. Evidence supports a modest benefit of dextromethorphan, but not codeine, on cough severity in adults with cough due to acute respiratory tract infections. Treatment of postnasal drip (with antihistamines, decongestants, or nasal corticosteroids) or GERD (with H2-blockers or proton-pump inhibitors), when accompanying acute cough illness, can also be helpful. There is good evidence that vitamin C and echinacea are not effective in reducing the severity of acute cough after it develops; however, evidence does support vitamin C (at least 1 g daily) for prevention of colds among persons with major physical stressors (eg, post-marathon) or malnutrition. Treatment with zinc lozenges, when initiated within 24 hours of symptom onset, reduces the duration and severity of cold symptoms.

B. Persistent and Chronic Cough

Evaluation and management of persistent cough often requires multiple visits and therapeutic trials, which frequently lead to frustration, anger, and anxiety. When pertussis infection is suspected, treatment with a macrolide antibiotic (azithromycin 500 mg on day 1, then 250 mg once daily for days 2–5; clarithromycin 500 mg twice daily for 7 days; erythromycin 250 mg four times daily for 14 days) is appropriate to reduce shedding and transmission of the organism. When pertussis infection has lasted more than 7–10 days, antibiotic treatment does not affect the duration of cough, which can last up to 6 months. Early identification and treatment of patients who work or live with persons at high-risk for complications from pertussis is encouraged (pregnant women, infants [particularlyyounger than 1 year], and immunosuppressed individuals). There is no  evidence to guide how long treatment for persistent cough due to postnasal drip, asthma, or GERD should be continued.

 When to Refer

• Failure to control persistent or chronic cough following empiric treatment trials. The small percentage of patients with idiopathic persistent cough should be managed in consultation with an otolaryngologist or a pulmonologist; treatment options include nebulized lidocaine therapy and morphine sulfate, 5–10 mg orally twice daily.

• Patients with recurrent symptoms should be referred to an otolaryngologist or a pulmonologist.  

 When to Admit

•  Patient at high risk for tuberculosis for whom compliance with respiratory precautions is uncertain.
• Need for urgent bronchoscopy, such as suspected foreign body.
• Smoke or toxic fume inhalational injury.

• Intractable cough despite treatment, when cough impairs gas exchange or in patients at high risk for barotraumas (eg, recent pneumothorax).