Cough

Essentials of Diagnosis

• Inquire about

  • Age; tobacco, e-cigarette vaping, or cannabis use history; duration of cough

  • Occupational history and environmental and infection exposures

  • Dyspnea (at rest or with exertion)

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

  • Chest examination findings

General Considerations

• Cough results from stimulation of mechanical or chemical afferent nerve receptors in the bronchial tree

• Cough illness syndromes are defined as acute (< 3 weeks), persistent (3–8 weeks), or chronic (> 8 weeks)

• Postinfectious cough lasting 3–8 weeks also called subacute cough to distinguish this distinct clinical entity from acute and chronic cough

• The prevalence of pertussis infection in adults with a cough lasting > 3 weeks is 20%, although exact prevalence is difficult to ascertain due to the limited sensitivity of diagnostic tests

Symptoms and Signs

• Timing and character of cough are not very useful in establishing cause

• However, 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)

• Acute cough syndromes

  • Most due to viral respiratory tract infections (eg, influenza, SARS-CoV-2)

  • Presence of post-tussive emesis or inspiratory whoop in adults modestly increases the likelihood of pertussis, and absence of paroxysmal cough and the presence of fever decreases its likelihood

  • Less common causes include heart failure (HF), hay fever (allergic rhinitis), and occupational factors

• Search for additional features of infection such as fever, nasal congestion, and sore throat

• Dyspnea (at rest or with exertion) may reflect a more serious condition

• Persistent cough is usually due to

  • Angiotensin-converting enzyme (ACE) inhibitor therapy

  • Postnasal drip

  • Asthma

  • Gastroesophageal reflux disease (GERD)

• Less common causes of persistent cough

  • Bronchogenic carcinoma

  • Chronic bronchitis

  • Bronchiectasis

  • Other chronic lung disease

  • HF

• Chronic cough

  • Accompanied by dry eyes may suggest Sjögren syndrome

  • If dry, it may be the first symptom of idiopathic pulmonary fibrosis

• Signs of pneumonia

  • Tachycardia

  • Tachypnea

  • Fever

  • Crackles

  • Decreased breath sounds

  • Fremitus

  • Egophony

• Signs of acute bronchitis: wheezing and rhonchi

• Signs of chronic sinusitis: postnasal drip

• Signs of COPD

  • Abnormal match test (inability to blow out a match from 10 inches away)

  • Maximum laryngeal height < 4 cm (measured from the sternal notch to the cricoid cartilage at end expiration)

• Signs of HF

  • Symmetric basilar rales

  • Abnormal jugular venous pressure

  • Positive hepatojugular reflux

Differential Diagnosis

Acute cough

• Acute respiratory tract infection

• Asthma

• Allergic rhinitis

• HF

• ACE inhibitor therapy

Persistent cough

• Environmental exposures (cigarette smoke, air pollution)

• Occupational exposures

• Pertussis, SARS-CoV-2

• Postnasal drip

• Asthma (including cough-variant asthma)

• GERD

• COPD

• Chronic aspiration

• Bronchiectasis, eosinophilic bronchitis

• Tuberculosis or other chronic infection

• Interstitial lung disease

• Bronchogenic carcinoma

Laboratory Tests

• Pulse oximetry or arterial blood gas measurement

• Peak expiratory flow rate or spirometry

• Serum C-reactive protein levels > 30 mg/dL seem to improve diagnostic accuracy for pneumonia in adults with acute cough

Imaging Studies

• Acute cough: obtain chest radiograph if abnormal vital signs or chest examination; higher index of suspicion in elderly and immunocompromised persons

• Persistent cough: obtain chest radiograph if unexplained cough lasts more than 3–6 weeks

Diagnostic Procedures

• Sinus CT scan for cough with postnasal drip (Table 2–2)

• Spirometry

  • Consider methacholine challenge if normal spirogram (Table 2–2)

  • May help identify large airway obstruction in patients who have persistent cough and wheezing who are not responding to asthma treatment

• Esophageal pH monitoring for cough with GERD symptoms (Table 2–2)

• Reserve procedures for patients with persistent cough who do not respond to therapeutic trials

• Pertussis detection by culture and polymerase chain reaction test of nasopharyngeal swab

Medications

Acute cough

• Treatment should target

  • The underlying cause of the illness

  • The cough reflex itself

  • Any additional factors that exacerbate the cough

• Oseltamivir and zanamivir are equally effective (1 less day of illness) when initiated within 30–48 hours of onset of influenza

• Erythromycin or doxycycline are first-line antibiotics for documented Chlamydia or Mycoplasma infection

• In patients with bronchitis or wheezing, inhaled β₂-agonist therapy reduces severity and duration of cough

• Dextromethorphan produces a modest benefit on the severity of cough due to acute respiratory tract infections

• In patients with acute cough, treating accompanying postnasal drip (with antihistamines, decongestants, saline nasal irrigation, or nasal corticosteroids) or asthma (with β₂-agonist) can also be helpful (see Table 2–2)

• Zinc lozenges > 75 mg/day, when initiated within 24 hours of symptom onset, may reduce the duration and severity of cold symptoms

• Vitamin C and echinacea are not effective in reducing the severity of acute cough illness after it develops

Persistent cough

• If due to pertussis, macrolide antibiotic therapy can reduce transmission

  • 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

• 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

• For idiopathic persistent cough, lidocaine nebulized or morphine sulfate (5–10 mg twice daily) orally

When to Refer

• Failure to control persistent cough following empiric treatment trials

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

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

• When cough impairs gas exchange or in patients at high risk for barotrauma (eg, recent pneumothorax)