Bronchiolitis

Overview

Bronchiolitis is often a viral cause mainly Respiratory Syncytial Virus (RSV). Bronchiolitis is the most common respiratory tract infection of neonates and is usually self-limiting. A major source of confusion of treatment is differentiating a viral bronchiolitis to asthma. In summary bronchiolitis is usually seen in infants <2yo. Asthma is seen in older children.

Respiratory Physiology

Aetiology & Risk Factors

Aetiology

Winter Respiratory Syncytial Virus (RSV)

Others

• Mycoplasma
• Parainfluenza
• Adenovirus

Risk factors for severe bronchiolitis

• Young, especially < 6weeks
• Ex-premature infants
• Congenital Heart disease
• Neurological conditions
• Chronic respiratory illness
• Pulmonary hypertension

Pathophysiology

An RSV infection begins with replication of the virus in the nasopharynx. The virus spreads to the small bronchiolar epithelium lining the small airways within the lungs, and a lower respiratory tract infection can begin in one to three days. If a lower respiratory tract infection occurs, it causes edema, increased mucus production, and eventual necrosis and regeneration of these epithelial cells. This leads to small airway obstruction, air trapping, and  increased airway resistance.

Clinical Manifestation

• Nasal obstruction +/- rhinorrhea
• Apnoea
• Irritating cough
• Tachypnoea
• Respiratory distress
• Fever
• Poor feeding

Examination

• Auscultation (variable): fine inspiratory crackles, expiratory wheeze
• Fever
• Decreased oxygen saturation
• Signs of dehydration

Diagnosis

Diagnosis is clinical

Investigations

In most children with bronchiolitis no investigations are required unless severe.

• PCR for RSV
• Chest X-Ray – hyperinflation
• Blood gases – Oxygen status
• Full Blood Count – signs of infection

Differential diagnosis

• Acute asthma, associated with viral LRTI
• Pneumonia
• Congestive heart failure
• Pertussis
• Pneumothorax
• Bronchial foreign body

Classification

Mild bronchiolitis

• Manage at home
• little or no respiratory distress
• SaO2 >95%

Moderate bronchiolitis

• admit to hospital
• Increased work of breathing, chest wall retraction, nasal flaring
• Decreased feeding
• SaO2 90-95%

Severe bronchiolitis

• Usually require transfer to a tertiary paediatric ICU
• Moderate to serve respiratory distress, with marked chest wall retraction, nasal flaring and grunting
• Very poor feeding, feeding may worsen the cough, tachycardia
• SaO2 >90% room air, or <92 with O2 therapy

High Risk Group

• Infants with chronic lung disease
• infants with congenital heart disease
• Premature or low-weight for gestation age
• Full-term infants up to three months of age

Treatment

Oxygen if saturation drops to 95%

Mild bronchiolitis

• Manage at home
• little or no respiratory distress
• SaO2 >95%

Moderate bronchiolitis

• admit to hospital
• Increased work of breathing, chest wall retraction, nasal flaring
• Decreased feeding
• SaO2 90-95%

Severe bronchiolitis

• Usually require transfer to a tertiary paediatric ICU
• Moderate to serve respiratory distress, with marked chest wall retraction, nasal flaring and grunting
• Very poor feeding, feeding may worsen the cough, tachycardia

Fluids

• Oral feeding OR
• Nasogastric tube for infants with poor feeding OR
• Intravenous fluids if previous do not work and if infant have severe bronchiolitis

Pharmacological Therapy

• Generally no bronchodilators <6months of age
• Corticosteroids or ipratropium only in older infants, if asthma is considered, or infants with chronic lung disease
• Antibiotics if bacterial cause is suspected

Discharge

• Minimal respiratory distress
• During the recovery phase, SaO2 92 or above room air
• Provide education, support and follow up with GP

Complication & Prognosis

Complications

• Most resolve without complications
• Dehydration – fluid needs, oral intake, vomiting
• Apnoea – particularly in infants born prematurely & those <2/12, risk for respiratory failure & need for mechanical ventilation
• Secondary bacterial infection

Prognosis 

40 percent of children with bronchiolitis will develop further wheezing episodes through five years of age, and 10 percent will have wheezing episodes beyond this age.

References

1. Caswell, MD & Muncie, HL 2011, Repiratory Syncytial Virus Infection in Children, American Family Physician, vol. 15, no. 2, pp 141-146.
2. Ralston, SL, Lieberthal, AS, Meissner, HC, et al. 2014, Clinical Practice Guideline: The Diagnosis, Management, and Prevention of Bronchiolitis, vol. 123, no. 5.
3. Royal Children Hospital Melbourne Clinical Guidelines