Paediatrics chapters
Bronchiolitis
The common winter viral infection of the small airways in infants: who gets it, how it looks, which babies need admission, and why care is supportive.
- Bronchiolitis is a viral inflammation of the bronchioles in children under 2 (peak 2-6 months), caused mainly by RSV, in winter.
- After 1 to 2 days of coryza the infant develops cough, fast breathing, recession, hyperinflation, wheeze and crackles; X-ray (not routine) shows hyperinflation.
- Treatment is supportive: humidified oxygen, suction, fluids or tube feeds; antibiotics, steroids and sedatives have no routine role; palivizumab protects high-risk infants.
On this page
Overview
Acute bronchiolitis is a viral inflammation of the bronchioles in infants. It is a common disorder of infancy, affecting about 6-7% of children under 2 years, mostly in winter. Most infants recover with supportive care, but young, premature and sick babies can develop apnoea and respiratory failure.
Aetiology and risk factors
Viruses
- Respiratory syncytial virus (RSV): more than half of cases.
- Others: parainfluenza, adenovirus, rhinovirus, and Mycoplasma.
Epidemiology
- Affects about 6 to 7% of infants under 2 years; peak at 2-6 months of age (Nelson), because the airways are small.
- Boys more than girls.
- Winter and early spring (in our setting roughly December to March).
- Usually caught from an older family member with a cold; community outbreaks.
- More common with crowding; less common in breastfed babies.
Risk factors for severe disease
- Age under 12 weeks.
- Prematurity.
- Underlying heart disease (especially congenital heart disease), chronic lung disease, neurological disease or immunodeficiency.
Pathophysiology
- The virus infects the lining of the bronchioles, causing inflammation, oedema, excess mucus and shed cell debris.
- These block the small airways. Where a bronchiole is partly blocked, air enters but cannot leave, so that segment over-inflates (air trapping); where it is completely blocked, the air is absorbed and the area collapses (atelectasis).
- The result is a patchy mix of hyperinflation and collapse, with hypoxaemia; tiring infants develop respiratory acidosis.
The hyperinflated lungs push the diaphragm down, so the liver and spleen become palpable without being enlarged.
Clinical features
- 1 to 2 days of mild coryza, often with another ill family member.
- Then increasing cough, fast breathing, difficulty feeding, vomiting and irritability.
- Fever is mild (rarely above 39°C).
- Tachypnoea (often 60 to 80 per minute), shallow breathing, nasal flaring, subcostal and intercostal recession.
- Expiratory wheeze, prolonged expiration, grunting; Nelson describes diffuse wheezes and crackles throughout the breathing cycle.
- Hyperresonant chest, reduced breath sounds; in very severe cases breath sounds are hardly audible.
- Palpable liver and spleen (pushed down), tachycardia.
- Apnoea may be the first sign in young or premature infants.
Severity indicators
| Feature | Points to severe disease |
|---|---|
| Breathing | Very fast breathing, marked recession, grunting |
| Oxygen | Hypoxia, cyanosis |
| Feeding | Unable to feed by mouth, dehydration |
| Pauses | Apnoea |
| Behaviour | Lethargy, exhaustion |
| Host | Age under 12 weeks, preterm, heart or lung disease |
Investigations
The diagnosis is clinical: a previously healthy infant with a first episode of wheeze after a cold, during the winter season and a community outbreak.
| Test | Findings |
|---|---|
| Chest X-ray (not routine) | Hyperinflation: increased lucency, increased AP diameter, flat diaphragms; increased bronchovascular markings, mild infiltrates, patchy atelectasis |
| Blood count | White cell and differential counts usually normal |
| Viral studies | Rapid RSV antigen test, viral culture of nasopharyngeal secretions; viral antibody titres |
| Pulse oximetry | Guides need for oxygen |
| Blood gases | In severe cases: hypoxaemia, rising CO2, respiratory acidosis |
An X-ray is not indicated in every case (Akbar). Nelson adds that routine laboratory tests are not needed to confirm the diagnosis; pulse oximetry is enough to follow oxygenation.
Differential diagnosis
| Condition | Distinguishing points |
|---|---|
| Asthma | Rare under 1 year; family history of asthma; repeated attacks; good response to bronchodilators or adrenaline |
| Bronchopneumonia | High fever, toxic child, leucocytosis, focal signs |
| Pertussis | Bouts of paroxysmal cough, lymphocytosis, no X-ray findings |
| Cystic fibrosis | Repeated chest infections, malabsorption, raised sweat chloride |
| Heart failure | Enlarging liver, abnormal heart findings, murmur |
Bronchiolitis is the usual cause of a first wheezing episode in an infant; repeated wheezing with a family history points to asthma.
Management
Who should be admitted
Admit infants with severe respiratory distress, hypoxia, inability to feed by mouth, apnoea or extreme tachypnoea, and consider admission for those with risk factors (under 12 weeks, preterm, heart, lung, neurological or immune disease). Watch closely because deterioration is most likely in the first 48 to 72 hours.
Supportive care (the main treatment)
- Humidified oxygen for hypoxia.
- Gentle suction of nose and mouth secretions to ease distress and cyanosis.
- Prop the infant up at about 30 to 40 degrees.
- Fluids: oral if feeding well; nasogastric or IV if not, to prevent dehydration.
- Correct acidosis and electrolyte problems.
- CPAP or heliox by tight mask may help moderate to severe cases; ventilation for respiratory failure.
Drugs
| Drug | Role |
|---|---|
| Ribavirin (antiviral) | Can be used for severe RSV bronchiolitis in infants with heart or chronic lung disease; its use is controversial in healthy infants |
| Bronchodilators | At most brief benefit in some infants; not routine |
| Corticosteroids | Not effective |
| Antibiotics | Not indicated unless there is secondary bacterial infection |
| Sedatives | Avoid: they depress breathing |
Bronchiolitis is not treated like asthma. Steroids do not help, and antibiotics are only for proven or strongly suspected bacterial infection.
"Oxygen, Suction, Fluids, Watch" is the whole treatment for most babies.
Complications
- Secondary bacterial pneumonia.
- Pneumothorax.
- Dehydration (poor feeding plus fast breathing).
- Respiratory acidosis and respiratory failure.
- Heart failure, especially with congenital heart disease.
- Apnoea (young and premature infants) and death, in less than 1%.
Course and prognosis
- Most improve within days; symptoms can last up to 3 weeks (median about 14 days).
- Case fatality is below 1%; deaths come from apnoea, respiratory arrest or severe dehydration.
- Later recurrent wheezing and asthma are more frequent, especially with a family history of atopy.
Prevention
- Palivizumab: an intramuscular monoclonal antibody against the RSV F protein, given to high-risk infants (prematurity, chronic lung disease, significant congenital heart disease).
- RSV immunoglobulin (intravenous) was used before palivizumab.
- Careful hand washing to stop spread in hospital and at home.
- Bronchiolitis is less common in breastfed infants and commoner with crowding.
Expect: RSV as the commonest cause; age under 2 with peak at 2-6 months in winter; coryza then cough, tachypnoea, recession, wheeze and crackles; palpable liver from hyperinflation; X-ray hyperinflation with patchy atelectasis and a normal white count; admission for hypoxia, poor feeding, apnoea or extreme tachypnoea and for high-risk infants; humidified oxygen, suction and fluids as treatment; steroids ineffective; antibiotics only for secondary infection; ribavirin for high-risk infants; palivizumab for prevention; and the differences from asthma and bronchopneumonia.
Quick revision
- Viral (RSV over half), under 2 years, peak 2-6 months, winter, boys, crowding.
- Bronchiolar oedema, mucus, debris: air trapping and patchy collapse.
- Coryza then cough, fast breathing, recession, wheeze, crackles; mild fever.
- X-ray not routine: hyperinflation, patchy atelectasis; WBC normal.
- Admit: hypoxia, poor feeding, apnoea, severe distress, high-risk infant.
- Oxygen, suction, propped up, fluids; no steroids, no routine antibiotics, no sedatives.
- Ribavirin for high-risk; palivizumab prevents.
- Worst at 48 to 72 hours; mortality under 1%; later wheeze common.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Which virus causes most bronchiolitis?
Respiratory syncytial virus, responsible for more than half of cases; parainfluenza, adenovirus and rhinovirus cause most of the rest.
Do babies with bronchiolitis need a chest X-ray?
Not routinely. The diagnosis is clinical; an X-ray is kept for severe or unusual cases and typically shows hyperinflation with patchy collapse.
Are steroids or antibiotics useful?
Steroids are not effective, and antibiotics are only for secondary bacterial infection. Care is supportive with oxygen, suction and fluids.
How is bronchiolitis different from asthma in a wheezy infant?
Bronchiolitis is usually a first episode after a cold in winter in an infant; asthma is rare in the first year and shows repeated attacks, a family history and a clear response to bronchodilators.