Signs and Symptoms of Bronchiolitis
Bronchiolitis presents as a viral upper respiratory infection that progresses to lower respiratory tract involvement, characterized by tachypnea, wheezing, crackles, cough, and signs of increased respiratory effort in children under 2 years of age. 1, 2
Initial Presentation (Days 1-3)
The illness begins with typical cold symptoms before progressing to more severe respiratory manifestations:
- Nasal congestion and rhinorrhea are the initial symptoms 1, 3
- Mild fever commonly occurs in the first 1-3 days 3, 4
- Coryza (runny nose) serves as the prodromal phase lasting 1-3 days 5, 4
Progressive Lower Respiratory Signs (Days 3-5)
Symptoms typically worsen over several days, peaking around days 3-5 of illness:
- Tachypnea (fast breathing) is a hallmark finding, with rates ≥70 breaths/minute indicating severe disease 1, 2
- Wheezing or whistling sounds when breathing are common 1, 2
- Crackles (rales) heard throughout both lung fields on auscultation 1, 2, 4
- Persistent cough that may worsen before improving 1, 4
Signs of Increased Respiratory Effort
These physical examination findings indicate respiratory distress and require careful assessment:
- Intercostal and subcostal retractions (chest wall pulling in) 2, 4
- Nasal flaring 2, 4
- Grunting 2, 4
- Head bobbing 4
- Tracheal tug 4
Feeding and Hydration Effects
- Difficulty feeding due to nasal congestion and fast breathing 1
- Poor feeding or reduced intake occurs in approximately 30% of cases 6
- Dehydration may develop from reduced oral intake 5
- Children may tire easily during feedings 1
Mental Status Changes
- Lethargy should be evaluated as a sign of severity 2
- Irritability is associated with more severe disease (statistically significant predictor) 6
Severe Disease Indicators
These red flags require immediate medical attention:
- Apnea (breathing pauses), particularly in very young infants 5, 4
- Central cyanosis (blue discoloration) 4
- Oxygen saturation <90-92% 5
- Respiratory rate ≥70 breaths/minute 1, 2
- Extreme difficulty feeding or complete refusal to eat or drink 1
High-Risk Patient Characteristics
Certain infants are predisposed to more severe presentations:
- Age <12 weeks (3 months) 1, 2, 7
- Prematurity 2, 7, 5
- Chronic lung disease or bronchopulmonary dysplasia 1, 2, 7
- Hemodynamically significant congenital heart disease 2, 7, 5
- Immunodeficiency 2, 7, 5
Clinical Course
- Most children recover at home with supportive care over 8-15 days 1
- Symptoms resolve over days to weeks after peaking 3
- Nearly 90% of children get RSV in their first 2 years of life, with up to 40% developing lower respiratory tract infection during first infection 1
Important Clinical Pitfalls
- Count respiratory rate for a full 60 seconds to ensure accuracy, as rates can vary 2
- Serial observations over time are necessary since the disease state varies throughout the illness 2
- The diagnosis is entirely clinical based on history and physical examination—routine chest radiographs, laboratory studies, or RSV testing are not recommended as they do not alter management 2, 7