Bronchiolitis

Why is this topic important?

Bronchiolitis is the commonest lower respiratory tract infection in infancy and one of the most frequently tested respiratory conditions in MRCPCH examinations. Candidates are expected to recognise the typical clinical presentation, understand risk factors for severe disease and know current evidence-based management.

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Definition

Bronchiolitis is an acute viral infection of the lower respiratory tract affecting the bronchioles, resulting in airway inflammation, oedema, increased mucus production and airway obstruction.

It primarily affects infants under 12 months of age.

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Key MRCPCH Facts

• Most common cause of hospital admission in infants.

• Respiratory Syncytial Virus (RSV) is the commonest cause.

• Peak incidence occurs during winter months.

• Most commonly affects infants aged 2–6 months.

• Premature infants are at increased risk of severe disease.

• Management is predominantly supportive.

• Bronchodilators are not routinely recommended.

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Pathophysiology

Viral infection leads to:

• Inflammation of bronchiolar epithelium

• Increased mucus production

• Airway oedema

• Airway obstruction

This results in:

• Air trapping

• Atelectasis

• Ventilation-perfusion mismatch

• Increased work of breathing

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Risk Factors for Severe Disease

Infant Factors

• Prematurity

• Chronic lung disease

• Congenital heart disease

• Neuromuscular disorders

• Immunodeficiency

Environmental Factors

• Tobacco smoke exposure

• Crowded living conditions

• Older siblings attending school

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Clinical Features

Early Symptoms

• Coryza

• Nasal congestion

• Mild cough

• Low-grade fever

Progressive Symptoms

• Tachypnoea

• Increased work of breathing

• Nasal flaring

• Recession

• Wheeze

• Crackles

Severe Disease

• Apnoea

• Cyanosis

• Exhaustion

• Poor feeding

• Dehydration

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Investigations

Usually Not Required

Bronchiolitis is primarily a clinical diagnosis.

Consider

Oxygen Saturation

Assess severity.

Blood Gas

If severe respiratory distress.

Viral Testing

May assist cohort nursing but usually does not alter management.

Chest X-Ray

Not routinely indicated.

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Management

Supportive Care

Mainstay of treatment.

Includes:

• Oxygen therapy if required

• Adequate hydration

• Nasogastric feeding when feeding is poor

• Monitoring respiratory status

Escalation of Respiratory Support

If worsening:

• High-flow nasal cannula oxygen

• CPAP

• Mechanical ventilation (rare)

Treatments Not Routinely Recommended

• Salbutamol

• Antibiotics

• Steroids

• Nebulised adrenaline

unless another indication exists.

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Complications

Short-Term

• Apnoea

• Respiratory failure

• Dehydration

Long-Term

• Recurrent wheeze

• Increased risk of later childhood wheezing disorders

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Common Exam Traps

Trap 1

RSV is the commonest cause.

Trap 2

Crackles are often more prominent than wheeze.

Trap 3

Routine antibiotics are not indicated.

Trap 4

A normal chest X-ray is common.

Trap 5

Young infants may present with apnoea before obvious respiratory symptoms.

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One Minute Revision

• RSV = most common cause.

• Peak age 2–6 months.

• Coryza → cough → wheeze/crackles.

• Clinical diagnosis.

• Supportive management.

• No routine bronchodilators.

• Watch for apnoea in young infants.

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Related Question of the Day

A 5-month-old infant presents with coryza, cough, wheeze and crackles. Which organism is the most likely cause?

A. Adenovirus

B. Respiratory Syncytial Virus

C. Streptococcus pneumoniae

D. Influenza B

E. Mycoplasma pneumoniae

Answer

B. Respiratory Syncytial Virus

Explanation

RSV is the commonest cause of bronchiolitis and accounts for the majority of hospital admissions due to bronchiolitis.

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Related Topics

• Asthma

• Pneumonia

• Apnoea of Prematurity

• Respiratory Distress Syndrome

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Suggested References

1. NICE Guideline NG9: Bronchiolitis in Children

2. RCPCH Guidance

3. BNF for Children

4. Nelson Textbook of Pediatrics

5. Illustrated Textbook of Paediatrics

6. Kendig's Disorders of the Respiratory Tract in Children

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Disclaimer

These notes are intended for MRCPCH revision and educational purposes only. They do not replace local, national or institutional guidelines. Clinical decisions should always be based on current guidance, senior advice and individual patient circumstances.