Wheezing

Wheezing is a high-pitched, continuous respiratory sound due to narrowing of the airways below the thoracic inlet. Causes of wheezing can be infectious (e.g., URTIs, bronchiolitis), allergic or inflammatory (e.g., anaphylaxis, bronchopulmonary dysplasia), structural (e.g., lower airway foreign body aspiration), or other (e.g., pulmonary edema, neuromuscular disorders). The initial management of wheezing includes airway management, treating rapidly reversible causes of wheezing, etiology-specific diagnostics, and managing the underlying cause. Stridor, stertor, and rales may mimic wheezing but are separate entities that imply an alternative pathology.

See also “Dyspnea,” “Airway obstruction,” and “Respiratory failure and arrest.”

Infectious ^[1][2]

• Children and adults
  • URTIs (e.g., influenza, RSV)
  • Pneumonia
  • Tuberculosis
• Adults primarily: acute bronchitis
• Children primarily
  • Bronchiolitis
  • Croup
  • Bacterial tracheitis

Allergic or inflammatory ^[1][2]

Acute

• Children and adults
  • Asthma exacerbation
  • Anaphylaxis
  • Smoke inhalation injury
  • Exposure to irritants and asphyxiants
• Adults primarily
  • Acute exacerbation of chronic obstructive pulmonary disease (AECOPD)
  • Medication-induced (e.g., NSAID hypersensitivity, ACE inhibitors)
  • Allergic bronchopulmonary aspergillosis

Chronic

• Children and adults
  • Asthma
  • Gastroesophageal reflux disease
  • Bronchiolitis obliterans
• Adults primarily
  • COPD
  • Granulomatosis with polyangiitis
• Children primarily: bronchopulmonary dysplasia

Structural ^[1][2]

• Adults and children
  • External compression by mediastinal masses or lymphadenopathy
  • Lower airway injury from blunt or penetrating trauma
  • Postintubation tracheal stenosis
• Adults primarily
  • Endobronchial tumors (e.g., lung cancer)
  • Bronchiectasis
• Children primarily
  • Lower airway foreign body aspiration (FBA)
  • Congenital anomalies, e.g.:
    • Bronchial or tracheal stenosis
    • Vascular ring
  • Tracheomalacia
  • Disorders of secretion clearance, e.g.:
    • Cystic fibrosis
    • Primary ciliary dyskinesia

Other ^[1][2]

The following occur commonly in adults and children.

• Cardiogenic pulmonary edema
• Noncardiogenic pulmonary edema
• Functional respiratory disorders (e.g., vocal cord dysfunction)
• Neuromuscular disorders, e.g.:
  • Myasthenia gravis
  • Guillain-Barré syndrome

• ABCDE survey
• For signs of impending respiratory failure:
  • Basic airway management
  • Consider noninvasive positive-pressure ventilation.
  • If indicated, perform endotracheal intubation with caution (see “High-risk indications for mechanical ventilation”).
  • Ventilation strategies for obstructive lung disease
• Treat rapidly reversible causes of wheezing, e.g.:
  • Treatment of anaphylaxis (e.g., epinephrine )
  • Acute management of obstructive lung disease
    • E.g., bronchodilators, steroids
    • For dosages, see “Pharmacotherapy for asthma exacerbation” and “Pharmacotherapy for AECOPD.”
  • Maneuvers to dislodge an aspirated FB
• Obtain etiology-specific diagnostics and manage the underlying cause.

Immediately manage central airway obstruction, if present.

Respiratory failure due to obstructive lung disease is a high-risk indication for mechanical ventilation associated with peri-intubation mortality. Anticipate and treat hypoxia and dynamic hyperinflation. ^[3][4]

Focused history ^[1]

• Age: infant, child, or adult
• Onset: acute or chronic
• Prior events
  • Asthma triggers
  • Exposure to allergens
  • URTI or febrile illness
  • Choking episode or aspiration event
  • Exercise or strenuous activity
  • Previous intubation and/or airway trauma or surgery
• Exacerbating factors
  • Feeding
  • Worsening of symptoms at nighttime
  • Positional changes
• Associated symptoms
  • Recurrent URTIs
  • Cyanosis
  • Cough
  • Urticaria
  • Constitutional symptoms

Focused physical examination ^[1]

• Clinical features of partial airway obstruction
• Clinical features of respiratory distress
• Clinical features of respiratory failure
• Lung auscultation
  • Focal or diffuse wheezing
  • Inspiratory or expiratory wheezing
• Head and neck examination, including:
  • Common features of upper respiratory tract infections
  • Tonsillar and/or adenoid hypertrophy
  • Lymphadenopathy
  • Goiter
• Skin examination, including:
  • Atopic dermatitis
  • Urticaria
  • Cyanosis
  • Nail clubbing

Differentiating wheezing from stridor is difficult. Wheezing is a musical sound produced primarily during expiration, whereas stridor is typically a single harsh, high-pitched sound during inspiration or expiration. ^[5]

Approach

Distinguish wheezing from mimics (e.g., stridor, stertor, rales) in all patients.

Unstable patients

Consider the following concurrently with the initial management of wheezing in patients with respiratory distress or respiratory failure:

• Immediate evaluation of undifferentiated respiratory failure
  • Bedside imaging: lung POCUS, portable CXR
  • Laboratory studies: CBC, blood gas analysis
• Urgent studies based on clinical suspicion
  • Obstructive lung disease: peak expiratory flow rate (PEFR)
  • Cardiac disease: ECG, troponin, BNP
  • URTI: respiratory viral panel
  • Neuromuscular disease: negative inspiratory force
  • Foreign body aspiration: bronchoscopy

Stable patients ^[1]

• PFTs: all patients ≥ 5 years of age with suspected obstructive lung disease
• CXR
  • Adults
    • Consider for first-time wheezing and/or suspected structural lung disease.
    • Not routinely indicated for exacerbations of obstructive lung disease ^[6][7]
  • Children ^[1]
    • Consider for suspected pneumonia or lower airway FBA.
    • Not routinely indicated otherwise (See “CXR in children with wheezing” for details.)
• Laboratory studies: Consider according to clinical suspicion.
• Advanced imaging (e.g., CT chest) or invasive studies (e.g., bronchoscopy): Consider in patients with recurrent or refractory unexplained wheezing.

Consider a trial of inhaled corticosteroids and bronchodilators as a dual diagnostic-therapeutic step in children < 5 years of age with URTI-triggered wheezing who cannot reliably undergo PFTs. ^[8]

Pulmonary function testing (PFTs) ^[9][10]

• Indications
  • Suspected obstructive lung disease (asthma, COPD)
  • See “PFT indications” for others.
• Modalities
  • Respiratory distress: Measure PEFR.
  • Stable patients ≥ 5 years of age: spirometry ^[1]
  • Uncertain diagnosis in stable patients: Consider adding bronchial provocation tests. ^[1]
• Findings
  • ↓ FEV₁
  • ↓ FEV₁/FVC ratio
  • Improvement in FEV₁ and/or FVC during bronchodilator responsiveness testing
  • See “PFT interpretation” for further details.
  • See “Diagnosis of asthma” and “Diagnosis of COPD” for disease-specific spirometry findings.

Imaging ^[1]

Imaging can be helpful to assess for anatomical abnormalities, foreign bodies, or infection.

• CXR (lateral and AP views)
  • CXR findings of bronchiolitis
  • CXR findings of COPD
  • CXR findings of pneumonia
  • CXR findings of pulmonary edema
  • Radiolucent foreign bodies may be visible in any view.
  • Asymmetrical lung inflation suggests an FB in a bronchus.
  • Situs inversus and dextrocardia suggest primary ciliary dyskinesia. ^[11]
• CT or MRI chest may confirm CXR findings and identify anatomical abnormalities.
• Barium swallow may identify vascular rings or esophageal compression.

CXR in children with wheezing ^[1]

• Not routinely indicated for children with first-time wheezing or typical manifestations of asthma, bronchiolitis, or croup ^[12]
• Consider in children with:
  • Wheezing refractory to therapy
  • Recurrent wheezing of unclear etiology
  • Suspected pneumonia ^[13][14]
    • Fever
    • Hypoxia
    • Signs of increased work of breathing (e.g., grunting)
    • Focal auscultation abnormalities
    • Abdominal pain
  • Suspected lower airway FBA (e.g., sudden onset without environmental or infectious trigger) ^[15]

Laboratory studies ^[1][9]

Routine testing is not recommended for wheezing, but studies may confirm the cause and guide management.

• Respiratory viral panel: to identify a causative virus
• Blood gas analysis: to assess for hypoxemia and/or hypercarbia
• CBC: to evaluate for eosinophilia, leukopenia, and/or leukocytosis
• In vivo allergy skin testing: to evaluate for type I hypersensitivity reactions (e.g., anaphylaxis)
• BNP: to evaluate for cardiogenic pulmonary edema
• Sweat test to diagnose cystic fibrosis
• Microbiological testing for active TB (e.g., acid-fast bacilli smear microscopy)

Airway endoscopy ^[1]

Direct visualization of the airway can provide a definitive diagnosis. Endoscopy may also be used for definitive management (e.g., removal of an FB or excision of an airway mass).

• Fiberoptic laryngoscopy
• Video laryngoscopy
• Rigid bronchoscopy
• Flexible bronchoscopy

Acute

Acute asthma exacerbation, URTI, anaphylaxis, and pulmonary edema also commonly cause acute wheezing in children; see “Causes of wheezing in all ages” and “Upper respiratory tract infection.”

Chronic or recurrent

Asthma is the most common cause of recurrent wheezing in children ≥ 5 years of age (see “Causes of wheezing in all ages”).

Vascular ring can be associated with wheezing but more commonly manifests with stridor; see “Congenital structural causes of airway obstruction.”

Asthma, asthma exacerbation, anaphylaxis, and pulmonary edema are also common causes of wheezing in adults (see “Causes of wheezing in all ages”).

• Inspiratory stridor
• Expiratory stridor
• Stertor
• Rales

• Perform an ABCDE survey.
• Signs of impending respiratory failure: Provide respiratory support.
• Treat rapidly reversible causes of wheezing, e.g.:
  • Treatment of anaphylaxis
  • Pharmacological treatment for acute asthma exacerbation
  • Pharmacological treatment for AECOPD
  • Maneuvers to dislodge an aspirated FB
• Narrow the differential diagnosis by performing a focused clinical evaluation.
• Obtain diagnostics based on the suspected cause, e.g.:
  • PEFR for asthma exacerbation
  • PFTs with bronchodilator responsiveness testing for asthma and/or COPD
  • CXR for anatomical abnormalities, foreign bodies, or infection
  • Sweat chloride testing for cystic fibrosis
• Initiate disease-specific management.