Wheezing, Emergency Medicine

Basics

Description

Result of turbulent airflow:
- High-pitched sound with dominant frequency at 400 Hz:
  - Gas flowing through constricted airways analogous to a vibrating reed
- Resonant vibration of the bronchial walls when airflow velocity reaches critical values
Caused by airway narrowing between 2 " 5 mm:
- Wheezing is very low pitched with airway diameters of 5 mm.
- Airways of <2 mm are unable to transmit sound because the energy is lost as friction heat.
Airway narrowing is caused by a combination of ≥1 of the following:
- Constriction (as with reactive airway disease)
- Peribronchial interstitial edema
- Inflammation
- Obstruction

Etiology

Pulmonary (small airway):
- Asthma
- Acute respiratory distress syndrome
- Anaphylaxis
- Aspiration pneumonia:
  - Wheezing occurs early in the disease due to intense bronchospasm following the event.
- Byssinosis:
  - Occupational lung disease of textile workers exposed to cotton dust
- Drugs:
  - Can precipitate angioedema or allergic reaction
  - ACE inhibitors
  - ²-blockers
  - Aspirin and NSAIDs
- Forced exhalation in normal patients
- Hyperventilation
- Chronic obstructive pulmonary disease
- Chronic cor pulmonale
- Chemical pneumonitis
- Carcinoid tumors
- Paroxysmal nocturnal dyspnea
- Pulmonary edema
- Pulmonary embolism:
  - Rarely associated with wheezing
  - Focal
- Pneumonia
- Sleep apnea
Pulmonary (large airway):
- Vocal cord dysfunction (paralysis, paradoxical movement)
- Foreign body
- Epiglottitis:
  - Wheezing associated with stridor in 10% of cases
- Diphtheria
- Smoke inhalation
- Bronchial tumor
- Tracheal tumor

Viral bronchiolitis in patients <3 yr of age
Asthma
Infection:
- Croup
- Rhinovirus
Foreign-body aspiration
Congenital abnormalities:
- Tracheomalacia
- Tracheal stenosis
Cystic fibrosis
CHF

Diagnosis

Signs and Symptoms

A whistling sound made while breathing:
- Diffuse:
  - As with reactive airway disease or pulmonary edema
- Focal:
  - As with pneumonia or pulmonary embolism
Dyspnea
Respiratory distress
Chest pain
Cough
Sputum production:
- Frothy (pulmonary edema)
Stridor
Fever
Cyanosis
Tachypnea
Tachycardia

History

Current URI:
- Rhinoviruses implicated in reactive airways
Recent exercise:
- Exercise-induced asthma, vocal cord dysfunction

Physical Exam

Mental status:
- Lethargy, confusion, and fatigue in the setting of respiratory distress are the primary reasons for airway management.
Presence of muscle retractions
Lung auscultation

Essential Workup

Pulse oximetry:
- Useful for assessing severity, but not for predicting hospital admission
Peak flow:
- Useful in assessing need for hospitalization
CXR

Diagnosis Tests & Interpretation

Lab

ABG:
- Sometimes used to determine whether patient is fatiguing by noting falling oxygenation, rising CO2, and acidosis
- Clinical assessment is a more reliable indicator of the need for airway management.
WBC:
- Elevated WBC does not distinguish infection from other disorders, as stress causes demargination.
- WBC is also elevated in noninfected patients taking steroids.
- A normal WBC does not rule out an underlying pneumonia.

Imaging

Peak expiratory flow (PEF):
- To assess function of small airways
- Use to determine severity and track the progress of therapy in patients with reactive airway disease.
CXR:
- Assess for diagnosis of pulmonary conditions:
  - Pneumonia
  - Foreign-body aspiration
- Assess for pulmonary edema.
EKG:
- Useful when patient is at risk for cardiac ischemia
- Indicated in all cases in which wheezing is caused by pulmonary edema
Soft-tissue neck:
- Used to assess for foreign body or obstructing mass

Diagnostic Procedures/Surgery
Laryngoscopy/bronchoscopy:

Indicated when obstruction is thought to be causal
Used to retrieve an inhaled foreign body or diagnose an underlying tumor

Differential Diagnosis

See Etiologies.

Treatment

Pre-Hospital

Supplemental oxygen
Initiate pulse oximetry and cardiac monitoring.
Initiate therapy for underlying condition when indicated:
- Asthma
- Pulmonary edema
Intubate for respiratory failure or anticipated respiratory failure.

Initial Stabilization/Therapy

ABCs
Intubation for impending airway failure:
- Prepare for possible foreign body in airway.
- Anticipate difficult airway.

Ed Treatment/Procedures

Correct hypoxemia: Supplemental oxygen
Initial assessment of severity:
- PEF >40%: Mild " moderate
- PEF <40%: Severe
Treat the underlying condition.
Rapid reversal of airflow obstruction:
- Bronchodilators:
  - Reversibility following the use of short-acting ²-agonists such as albuterol or terbutaline suggests reactive airway disease.
- Anticholinergics: Ipratropium bromide:
  - Add to ²-agonist therapy for severe disease
Reduce likelihood of relapse:
- Trial of steroids indicated if wheezing is caused by bronchospasm or noninfectious inflammation.
Adjunctive agents:
- Heliox:
  - Less dense than air or oxygen alone
  - Decreases work of breathing
  - More efficacious in large-airway disease
  - Not as effective for small-airway disease
- Magnesium sulfate:
  - Evidence for benefit only in moderate to severe asthmatics
- Ketamine:
  - For intubation of the asthmatic patient

Medication

First Line

Albuterol: 2.5 " 5 mg in 2.5 mL NS q20min inhaled 3 doses (peds: 0.15 mg/kg/dose q20min 3 doses; min. dose 2.5 mg)
Levalbuterol: 0.63 mg q8h (peds: 6 " 12 yr 0.31 mg q8h; >812 yr 0.63 mg q8h) via nebulizer
Prednisone: 40 " 80 mg PO (peds: 1 mg/kg/d in 2 div. doses; max. 60 mg/d)
Prednisolone: Peds 1 " 2 mg/kg/d in 2 div. doses PO; ipratropium insert in peds dose (peds: >12 yr 0.25 " 0.5 mg)
Racemic epinephrine: Peds 0.25 " 0.5 mL nebulized for croup

Second Line

Ipratropium bromide: 0.5 mg q20min 3 doses (peds: 0.25 " 0.5 mg q20min 3 doses); may mix with albuterol
Methylprednisolone: 40 " 80 mg IV (peds: 1 " 2 mg/kg/d IV or PO in 2 div. doses, max. 60 mg/d) for patients who cannot tolerate PO
Terbutaline: 0.25 mg SC q0.5h for 2 doses (peds: 0.01 mg/kg up to 0.3 mg SC):
- No proven advantage over aerosol therapy
Magnesium sulfate: 0.1 mL/kg of 50% solution IV over 20 min, then 0.06 mg/kg/h

Follow-Up

Disposition

Admission Criteria

Hypoxia
Persistent or worsening wheezing
Underlying condition requires hospital admission

Discharge Criteria

Improvement or resolution of wheezing
PEF >70% predicted
Adequate oxygenation

Issues for Referral
Asthma:

Referral should be made for a written asthma action plan.

Followup Recommendations

The patient should be instructed to return to the ED with shortness of breath, fever, hemoptysis, or chest pain.

Pearls and Pitfalls

Be prepared to manage the airway if administering an anxiolytic.

Additional Reading

Bacharier LB. Evaluation of the child with recurrent wheezing. J Allergy Clin Immunol. 2011;128(3):690.e1 " e5.
Fernandes RM, Bialy LM, Vandermeer B, et al. Glucocorticoids for acute viral bronchiolitis in infants and young children. Cochrane Database Syst Rev. 2013;6:CD004878.
Krafczyk MA, Asplund CA. Exercise-induced bronchoconstriction: Diagnosis and management. Am Fam Physician. 2011;84(4):427 " 434.
Mellis C. Respiratory noises: How useful are they clinically? Pediatr Clin North Am. 2009;56(1):1 " 17, ix.
Weinberger M, Abu-Hasan M. Pseudo-asthma: When cough, wheezing, and dyspnea are not asthma. Pediatrics. 2007;120(4):855 " 864.

Codes

ICD9

493.90 Asthma, unspecified type, without mention of status asthmaticus
519.11 Acute bronchospasm
786.07 Wheezing
496 Chronic airway obstruction, not elsewhere classified
478.25 Edema of pharynx or nasopharynx

ICD10

J45.909 Unspecified asthma, uncomplicated
J98.01 Acute bronchospasm
R06.2 Wheezing
J44.9 Chronic obstructive pulmonary disease, unspecified
J39.2 Other diseases of pharynx

SNOMED

56018004 Wheezing (finding)
991000119106 Reactive airway disease (disorder)
4386001 Bronchospasm (finding)
13645005 Chronic obstructive lung disease (disorder)
18197001 Asthmatoid wheeze (finding)
2129002 Edema of pharynx (disorder)
31572008 inspiratory wheezing (finding)
9763007 expiratory wheezing (finding)

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