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Cough

Last updated: September 23, 2021

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A cough is a protective mechanism that forcefully expels air from the lungs to clear secretions, foreign bodies, and irritants from the airway, and can be triggered by various conditions. A cough can be classified as acute, subacute, or chronic, in addition to productive (with sputum expectoration) or dry. The most common causes of acute cough are upper respiratory tract infections (URTIs), exacerbations of chronic conditions, and pneumonia. Subacute cough is often a sequela of a URTI (postinfectious cough) but can also be caused by upper airway cough syndrome (UACS) or pertussis. Common causes of chronic cough in adults include UACS, asthma, gastroesophageal reflux disease (GERD), nonasthmatic eosinophilic bronchitis (NAEB), and certain medications (e.g., ACE inhibitors, sitagliptin). The cause of an acute cough can often be determined clinically with a thorough medical history and physical examination. Chronic cough or the presence of red flag symptoms (including dyspnea, fever, hemoptysis, and weight loss) indicate that further investigation is required. Treatment depends on the underlying etiology and often includes symptomatic therapy.

See also “Dyspnea” and “Chest pain.”

  • Cough: a protective mechanism that forcefully expels air from the lungs to clear secretions, foreign bodies, and irritants from the airway
  • Upper airway cough syndrome (UACS): also known as postnasal drip [1][2]
    • The drainage of mucus down the back of the throat due to increased nasal mucus production; various causes, such as allergic rhinitis and chronic sinusitis
    • Symptoms include coughing, a feeling of obstruction in the throat, and throat clearing.
  • Protracted bacterial bronchitis [1]
    • Chronic bacterial infection that causes a productive cough
    • Clinical diagnosis requires all of the following:
      • Daily cough for > 4 weeks
      • Resolution within 2–4 weeks of antibiotic treatment
      • Absence of alternate diagnosis
  • Triggers: cough may be voluntary or a reflex to airway irritants/triggers
  • Cough reflex arc
  • Mechanism of cough reflex: initiation of the cough reflex arc leads to
    • Rapid inspiration, closure of the epiglottis and vocal cords (which traps inhaled air in the lungs), and contraction of the diaphragm, expiratory, and abdominal muscles → rapid increase of intrathoracic pressure
    • A sudden opening of the vocal cords and forceful expulsion of air from the lungs

References:[3][4][5][6][7][8]

Cough is usually classified by duration.

  • Adults and adolescents > 14 years of age [2]
    • Acute cough: < 3 weeks
    • Subacute cough: 3–8 weeks
    • Chronic cough: > 8 weeks
  • Children and adolescents ≤ 14 years of age [1][9][10][11]
    • Acute cough: < 2 weeks
    • Subacute cough: 2–4 weeks
    • Chronic cough: at least daily cough for > 4 weeks [11][12][13]
Causes of cough
Adults [2][13][14] Children [1][12][13]
Acute cough
Subacute cough
Chronic cough

In endemic areas, consider pulmonary tuberculosis in all patients with a cough of any duration. [2]

Consider pertussis in patients with risk factors, e.g., underimmunization and/or contact with an infected individual. [12]

Initial management [2][15]

Subsequent management [2][15]

  • If specific cough etiology is identified:
    • Order additional or confirmatory testing as directed by clinical suspicion (see “Diagnostics”).
    • Begin targeted therapy and consider adding symptomatic therapy as needed (see “Treatment”).
  • If the cause remains uncertain after initial evaluation:
    • Follow the recommended approach for cough by duration (see “Acute and subacute cough” and “Chronic cough”).
    • Consider empiric symptomatic therapy (see “Treatment”).
    • Consider observation and follow-up vs. a trial of empiric therapy based on the duration of symptoms.
    • Consider expedited specialist referral (e.g., pulmonology) for:
      • Suspected serious underlying conditions
      • Chronic cough of unclear etiology

Acute and subacute cough is most commonly due to self-limiting viral illnesses. Routine diagnostic studies are typically unnecessary unless red flags for cough are present or required for specific suspected cough etiologies.

A detailed history and physical examination are essential to help narrow down the possible causes of cough and guide initial investigations and management. [2][15]

History of present illness

  • Duration of cough (weeks): Ascertaining the symptom duration is a recommended first step in evaluating adults presenting with cough (see “Classification”). [2][15]
  • Other cough characteristics
    • Presence of sputum
      • Productive cough
      • Nonproductive cough
    • Onset
      • Sudden
      • Gradual
    • Quality: classic cough presentations in children [1][12]
  • Aggravating factors
    • Symptom variation depending on the weather and/or season
    • Supine position
    • Exercise
    • Daytime or nighttime worsening of symptoms
  • Associated symptoms

Cough exacerbated by exercise and at nighttime is characteristic of cough-variant asthma.

Coughing paroxysms, inspiratory whoop, and posttussive emesis are characteristic of pertussis. [16]

Other key historical features

Red flags for cough [2][13]

These red flag features may indicate a life-threatening cause of cough and typically warrant rapid evaluation and treatment.

An abnormal screening chest x-ray in a patient with cough is also a red flag (see “Diagnostics”).

The following recommendations apply to adults and are consistent with the 2006 and 2018 CHEST guidelines on diagnosis and management of cough. [2][15]

  • Suspected life-threatening causes of cough: Begin immediate empiric therapy and expedite targeted diagnostics and treatment.
  • Suspected self-limiting infectious (e.g., URTI, acute bronchitis) or postinfectious cause: Consider conservative approach. [19][20]
  • Suspected non-self-limiting infection (e.g., pneumonia, TB, pertussis): Confirm diagnosis and begin targeted therapy. [16]
  • Newly diagnosed chronic condition or exacerbation thereof (e.g., UACS, asthma, GERD, NAEB, COPD, bronchiectasis): Begin targeted management.
  • Suspected environmental or occupational lung disease: Limit exposure to the presumed trigger, refer to a specialist for targeted therapy. [15]
  • Subacute cough of suspected noninfectious origin: See “Chronic cough.”
  • Consider tailored symptomatic therapy and supportive care in all patients in addition to targeted therapy (see “Treatment”).
  • Monitoring
    • Adults [2]
      • Routine follow-up 4–6 weeks after cough onset
      • Use validated cough severity and quality of life measurement tools if available.
    • Children: Reassess if cough becomes chronic, i.e., lasts ≥ 4 weeks. [12]

Diagnostic studies for acute or subacute cough are not routinely indicated in patients without red flags for cough. [2][13][15]

Postinfectious cough is the most common cause of subacute cough and often resolves without treatment. If it is interfering with the patient's sleep and/or daily activities, consider the use of antitussives.

The following recommendations apply to adults and are consistent with the 2006 and 2018 CHEST guidelines on diagnosis and management of cough. [2][13][15]

  • Follow the diagnostic and therapeutic approach for suspected causes of cough based on detailed clinical evaluation for cough.
  • Obtain CXR as part of the routine evaluation (if not already performed). [2][12]
  • Eliminate any known modifiable triggers , e.g.:
    • Recommend smoking cessation and avoiding second-hand smoke.
    • Stop or substitute offending medications (e.g., ACE inhibitors, NSAIDs, beta blockers).
    • Recommend avoiding environmental and/or occupational exposures.
  • Focus the evaluation on the most common causes of chronic cough in adults and consider sequential diagnostics and/or empiric treatment. [15]
  • Reassess 4–6 weeks after the treatment is initiated. [2]
  • If symptoms persist despite evaluation and treatment for the most common causes:
    • Consult or refer to a specialist, e.g., pulmonology, otolaryngology.
    • Consider further diagnostic testing for less common causes (see “Diagnostics”).
Most common causes of chronic cough in adults
Initial management
UACS
Asthma
NAEB
GERD

In endemic areas, screen all patients with cough for tuberculosis regardless of cough duration. [12]

Also consider new-onset COPD, interstitial lung disease, and lung cancer, especially in patients with red flags for cough.

The following conditions should be considered in all adults who present with a cough accompanied by signs of respiratory distress, hemodynamic instability, and/or red flags for cough (see also “Dyspnea”):

If the patient is unstable, follow the ABCDE approach and consider immediate oxygen therapy, airway management, and/or mechanical ventilation.

A large proportion of malignancies are first diagnosed following an emergency presentation of illness, more often in vulnerable and marginalized patients. Maintain a high index of suspicion for lung cancer in patients with red flags for cough and consider expedited referral for definitive diagnosis, staging, and treatment to prevent poor outcomes. [21]

Diagnostic studies for acute or subacute cough are not routinely indicated in patients without red flags for cough. [2][13][15]

Initial investigations [2][22][23][24][25]

Additional investigations [2][22][23][24][25]

Consider the following on a case-by-case basis depending on clinical evaluation for cough, duration, and results of initial investigations.

Approach

  • Treat specific underlying cough etiologies.
  • Evaluate the patient's response with routine follow-up.
  • Reconsider the working diagnosis if treatment is unsuccessful.
  • Consider supportive measures and symptomatic treatment, e.g., in acute viral cough.
  • Consider referral to a specialist such as pulmonology or otolaryngology if chronic cough fails to improve or recurs despite adequate treatment.

Antibiotics are not recommended for the routine treatment of cough unless there is a proven indication, e.g., in pneumonia or acute bacterial sinusitis.

Supportive measures

  • Recommend rest and adequate hydration.
  • Advise patients to avoid lung irritants, e.g., smoke, incense. [26][27]
  • Nonpharmacological measures may be beneficial, e.g.: [14]
    • Nasal saline for nasal congestion
    • Honey [28][29][30]
    • A humidifier

Symptomatic treatment for cough [19][20][31][32]

  • Expectorants, e.g., guaifenesin (immediate release or extended release; )
    • Increases bronchial fluid content to loosen mucus (no cough suppression)
    • May be considered for productive coughs
  • Cough suppressants (antitussives)
    • Generally not effective [19][20]
    • May be considered for nonproductive coughs that interfere with sleep
    • Centrally acting: Suppress the cough reflex arc at the level of the central nervous system (see “Opioids“ for more information).
    • Peripherally acting: Suppress peripheral triggers of the cough reflex arc by anesthetizing respiratory stretch receptors, e.g., benzonatate

Antitussive medications decrease coughing and, therefore, should only be used in nonproductive cough, as coughing is needed for the expectoration of mucus. They are not indicated in productive coughs or coughs caused by an infection.

Avoid prescribing opioids as antitussive medication in patients with risk factors for or a history of substance use disorders.

Symptomatic treatment for specific types of cough

Treatment of associated symptoms

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