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Emergency and Acute Medicine – Wheezing
Wheezing is a high-pitched, musical sound produced by turbulent airflow through narrowed airways, typically with a dominant frequency around 400 Hz. It occurs when airflow causes vibration of bronchial walls, similar to a reed instrument. Wheezing is most prominent when airway diameters are between 2–5 mm; larger airways produce lower-pitched sounds, while very small airways (<2 mm) may not transmit sound effectively due to energy loss. Airway narrowing may result from bronchoconstriction, inflammation, edema, or obstruction, and identifying the underlying mechanism is critical in acute care settings.
The causes of wheezing are broad and include both small-airway (pulmonary) and large-airway etiologies. Small-airway causes commonly include Asthma, Chronic Obstructive Pulmonary Disease, pulmonary edema, anaphylaxis, and aspiration. Certain drugs such as ACE inhibitors, β-blockers, aspirin, and NSAIDs may precipitate bronchospasm or allergic reactions. Less common causes include pulmonary embolism, carcinoid tumors, and occupational lung diseases like byssinosis. Large-airway causes include foreign body aspiration, vocal cord dysfunction, epiglottitis, tumors, and smoke inhalation. In pediatric populations, common causes include Bronchiolitis, asthma, croup, and congenital airway abnormalities such as tracheomalacia.
Clinically, wheezing presents as a whistling sound during breathing, often accompanied by dyspnea, cough, chest tightness, and respiratory distress. Diffuse wheezing suggests generalized airway disease such as asthma or pulmonary edema, while focal wheezing raises concern for localized obstruction such as pneumonia or foreign body. Associated findings may include tachypnea, tachycardia, cyanosis, and use of accessory muscles. A critical aspect of assessment is the patient’s mental status—fatigue, confusion, or lethargy may indicate impending respiratory failure and necessitate urgent airway management.
Evaluation begins with assessment of severity and oxygenation. Pulse oximetry is essential for monitoring oxygen saturation, while peak expiratory flow (PEF) helps quantify airway obstruction and response to treatment. Chest X-ray may be used to evaluate for pneumonia, pulmonary edema, or foreign body. Arterial blood gas (ABG) may be useful in severe cases to assess for rising CO₂ and acidosis, indicating respiratory fatigue. Additional investigations such as ECG or laryngoscopy may be indicated depending on suspected etiology.
Management focuses on rapid stabilization and reversal of airway obstruction. Initial treatment includes supplemental oxygen and airway support. Bronchodilators are first-line therapy, particularly Albuterol given as 2.5–5 mg nebulized every 20 minutes for 3 doses (pediatric: 0.15 mg/kg per dose, minimum 2.5 mg). Systemic corticosteroids such as Prednisone (40–80 mg PO; pediatric 1 mg/kg/day, max 60 mg) or Methylprednisolone (40–80 mg IV) are used to reduce airway inflammation and prevent relapse.
For moderate to severe cases, Ipratropium Bromide (0.5 mg nebulized every 20 minutes for 3 doses) can be added to β-agonist therapy. Additional therapies include magnesium sulfate (0.1 mL/kg of 50% solution IV over 20 minutes) in severe asthma, terbutaline (0.25 mg SC), and heliox in selected cases. In pediatric croup, racemic epinephrine (0.25–0.5 mL nebulized) may be used. Intubation is indicated for patients with impending respiratory failure, and Ketamine may be preferred due to its bronchodilatory properties.
Disposition depends on clinical response. Patients with persistent hypoxia, worsening symptoms, or underlying serious conditions require admission. Those who improve with treatment, achieve PEF >70% predicted, and maintain adequate oxygenation may be discharged with follow-up and clear return precautions. Patients with asthma should receive an action plan and appropriate outpatient referral.
A key clinical pearl is to always consider non-asthma causes of wheezing, especially in cases of focal findings or poor response to bronchodilators. Additionally, clinicians must be prepared for rapid airway deterioration, particularly when administering sedatives or managing severe respiratory distress.
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