Pediatric Respiratory Distress
Introduction
Respiratory distress is one of the most common reasons for pediatric emergency department visits in Canada. For the MCCQE1, candidates must demonstrate the Medical Expert role by rapidly recognizing the signs of respiratory distress, distinguishing it from respiratory failure, and initiating age-appropriate management.
Understanding the anatomical and physiological differences in the pediatric airway is crucial. Children have higher metabolic rates, smaller functional residual capacities, and more compliant chest walls, making them prone to rapid desaturation.
Critical Concept: The transition from respiratory distress to respiratory failure can be abrupt in children. Early recognition of impending failure is a key objective for the MCCQE1.
Pathophysiology and Epidemiology
The etiology of respiratory distress varies significantly by age. A structured approach based on age group is essential for the differential diagnosis.
Neonates (<28 days)
Common Etiologies:
- Transient Tachypnea of the Newborn (TTN): Most common, especially after C-section.
- Respiratory Distress Syndrome (RDS): Prematurity, surfactant deficiency.
- Meconium Aspiration Syndrome.
- Sepsis/Pneumonia: Group B Streptococcus, E. coli.
- Congenital Heart Disease: Cyanotic lesions presenting upon ductal closure.
Clinical Presentation: Distress vs. Failure
Differentiation between respiratory distress (compensatory mechanisms intact) and respiratory failure (compensatory mechanisms failing) is a high-yield MCCQE1 topic.
Comparison Table
| Feature | Respiratory Distress | Respiratory Failure |
|---|---|---|
| Mental Status | Alert, irritable, anxious | Lethargic, decreased LOC, unresponsive |
| Work of Breathing | Increased (retractions, nasal flaring) | Decreased (fatigue) or paradoxical |
| Respiratory Rate | Tachypnea | Bradypnea (ominous sign) |
| Skin Colour | Pale, normal | Cyanotic, mottled, grey |
| Air Entry | Normal or wheeze/stridor | Silent chest, poor air movement |
| O2 Saturation | Maintainable >92% (often with O2) | Hypoxemia despite O2 (<90%) |
| Heart Rate | Tachycardia | Bradycardia (pre-arrest) |
🚩 MCCQE1 Red Flags
Silent Chest: In a severe asthmatic, the disappearance of wheezing without clinical improvement indicates insufficient air movement and impending arrest.
Bradycardia: In a hypoxic child, bradycardia is a sign of impending cardiac arrest. Start CPR if HR <60 bpm with signs of poor perfusion despite oxygenation and ventilation.
Approach to Evaluation
For MCCQE1 preparation, follow a systematic approach. The Pediatric Assessment Triangle (PAT) is the standard initial assessment tool in Canadian emergency medicine.
1. Pediatric Assessment Triangle (PAT)
- Appearance: Tone, interactiveness, consolability, look/gaze, speech/cry (TICLS).
- Work of Breathing: Abnormal sounds, positioning (tripod), retractions, flaring.
- Circulation to Skin: Pallor, mottling, cyanosis.
2. Detailed Evaluation Steps
Step 1: Rapid Primary Survey (ABCDE)
Assess Airway patency, Breathing (rate, effort, saturation), and Circulation (pulse, capillary refill). Intervene immediately if any life threats are identified.
Step 2: Focused History
Utilize the SAMPLE mnemonic tailored for pediatrics:
- Signs/Symptoms (Stridor vs. Wheeze is the key branching point).
- Allergies.
- Medications.
- Past medical history (Prematurity? Previous intubation? Asthma?).
- Last oral intake (Important for aspiration risk or dehydration).
- Events leading up to illness (Choking episode? Fever?).
Step 3: Physical Examination
- Inspection: Nasal flaring, tracheal tug, intercostal/subcostal retractions, grunting.
- Auscultation:
- Inspiratory Stridor: Upper airway obstruction (Croup, Epiglottitis, Foreign Body).
- Expiratory Wheeze: Lower airway obstruction (Asthma, Bronchiolitis).
- Crackles: Parenchymal disease (Pneumonia, Pulmonary Edema).
- ENT: Visualize posterior pharynx (Caution: Avoid if epiglottitis is suspected).
Step 4: Investigations (Selective)
- Pulse Oximetry: Continuous monitoring.
- CXR: Not routine for classic bronchiolitis or mild croup (Choosing Wisely Canada). Indicated for focal findings, suspected foreign body, or severe distress.
- Blood Gas: Capillary or Venous usually sufficient. Arterial is painful and rarely necessary unless precise pCO2/pO2 is required.
- Nasopharyngeal Swab: For respiratory viruses (RSV, Influenza, COVID-19) if it alters management or for infection control.
Management Principles
Management is dictated by the underlying cause and severity.
Common Canadian Treatment Protocols
1. Viral Croup (Laryngotracheobronchitis)
- Mild (Barking cough, no stridor at rest):
- Single dose oral Dexamethasone (0.6 mg/kg usually, max 10-16 mg).
- Discharge with education.
- Moderate/Severe (Stridor at rest, retractions):
- Nebulized Epinephrine (5 mL of 1:1000).
- Oral/IM Dexamethasone.
- Observe for at least 2-4 hours after epinephrine for “rebound phenomenon”.
2. Bronchiolitis
- Pathogen: Usually RSV.
- Mainstay: Supportive care (Hydration + Oxygen).
- Canadian Guidelines: Do NOT routinely use bronchodilators (salbutamol), steroids, or hypertonic saline in typical cases.
- Oxygen: Target saturation >90% while awake, >88% while asleep (CPS Guidelines).
3. Asthma Exacerbation
- PRAM Score: Use the Pediatric Respiratory Assessment Measure to grade severity.
- Mild/Moderate: Salbutamol (MDI with spacer) + Oral Steroids (Dexamethasone or Prednisone/Prednisolone).
- Severe: Oxygen + Continuous Salbutamol + Ipratropium Bromide + IV Steroids + Magnesium Sulfate (IV).
4. Anaphylaxis
- First line: IM Epinephrine (1:1000) into the anterolateral thigh.
- 0.15 mg for <25 kg (EpiPen Jr).
- 0.30 mg for >25 kg (EpiPen).
- Adjuncts: Antihistamines and steroids (second line, do not delay epinephrine).
Canadian Guidelines & “Choosing Wisely”
Familiarity with these guidelines is essential for the MCCQE1.
- Choosing Wisely Canada:
- Don’t order chest radiographs for children with uncomplicated asthma or bronchiolitis.
- Don’t use bronchodilators or corticosteroids for uncomplicated bronchiolitis.
- Canadian Paediatric Society (CPS):
- Recommends Dexamethasone for all severities of Croup.
- Recommends against over-investigation of febrile seizures associated with respiratory illness.
Key Points to Remember for MCCQE1
- Stridor vs. Wheeze: Stridor = Upper Airway; Wheeze = Lower Airway.
- Epiglottitis: Rare due to HiB vaccine. “Thumbprint sign” on lateral X-ray. Do not agitate the child. Secure airway in the OR.
- Foreign Body: Suspect in a toddler with sudden onset cough/choking. Inspiratory/expiratory films or lateral decubitus films may show air trapping (hyperinflation) on the affected side.
- Hypotension: A late and ominous sign in pediatric shock. Do not wait for hypotension to treat shock.
- Fluids: In respiratory distress, children are at risk of dehydration due to insensible losses and poor intake. However, avoid fluid overload in pneumonia/bronchiolitis as it may worsen pulmonary edema (SIADH risk).
Important Formulas
# Estimated Weight (if unknown):
Weight (kg) = (2 x Age in years) + 8
# Endotracheal Tube Size (Uncuffed):
Size (mm) = (Age in years / 4) + 4Sample Question
Case Scenario
A 2-year-old male is brought to the Emergency Department by his parents at 02:00. He has a 2-day history of low-grade fever and coryza. Tonight, he woke up with a harsh, barking cough and noisy breathing. On examination, he is alert but anxious. There is audible inspiratory stridor at rest and mild suprasternal retractions. His respiratory rate is 40 breaths/min, heart rate is 130 bpm, and oxygen saturation is 94% on room air. He has no known allergies and is fully immunized.
Question
Which one of the following is the most appropriate initial pharmacotherapy?
- A. Nebulized salbutamol
- B. Oral amoxicillin
- C. Oral dexamethasone
- D. Nebulized budesonide
- E. Intravenous ceftriaxone
Click to reveal the answer and explanation
Explanation
The correct answer is:
- C. Oral dexamethasone
Rationale: This patient presents with a classic picture of moderate viral croup (laryngotracheobronchitis), characterized by a barking cough, inspiratory stridor at rest, and retractions.
- Option C (Oral dexamethasone): According to Canadian Paediatric Society (CPS) guidelines, corticosteroids are the mainstay of treatment for croup of all severities. A single oral dose of dexamethasone (0.6 mg/kg) reduces the severity of symptoms, the need for nebulized epinephrine, and hospital admissions. It is the preferred initial pharmacotherapy.
- Option A (Nebulized salbutamol): Salbutamol is a beta-agonist used for lower airway obstruction (e.g., asthma, wheezing). It is ineffective for the upper airway edema seen in croup.
- Option B & E (Antibiotics): Croup is viral (usually Parainfluenza). Antibiotics are not indicated unless there is bacterial superinfection (e.g., bacterial tracheitis), which presents with high fever and toxic appearance, not seen here.
- Option D (Nebulized budesonide): While nebulized steroids can be effective, oral dexamethasone is preferred in the Canadian context due to ease of administration, lower cost, and equivalent efficacy. Nebulized budesonide is an alternative if the child vomits the oral medication.
Note: If the patient had severe distress or impending failure, nebulized epinephrine would be indicated concurrently with steroids, but dexamethasone remains the fundamental anti-inflammatory treatment.
References
- Canadian Paediatric Society. (2022). Acute management of croup in the emergency department. Retrieved from cps.ca
- Canadian Paediatric Society. (2021). Bronchiolitis: Recommendations for diagnosis, monitoring and management of children one to 24 months of age.
- Choosing Wisely Canada. (2023). Paediatrics: Ten Things Physicians and Patients Should Question. Retrieved from choosingwiselycanada.org
- Medical Council of Canada. (2023). MCCQE Part I Objectives: Respiratory System.
- Ortiz-Alvarez, O. (2023). Assessment of the child in acute respiratory distress. In: Canadian Paediatric Society Practice Points.