Overview
Definition:
Wheezing in infancy is a high-pitched whistling sound produced during respiration, most commonly heard during exhalation
It signifies airflow obstruction in the lower airways
Differentiating between episodic viral bronchiolitis and multi-trigger wheeze is crucial for appropriate management and prognosis.
Epidemiology:
Episodic viral bronchiolitis is extremely common, affecting up to one-third of infants within their first year of life, with a peak incidence at 3-6 months
Multi-trigger wheeze, often associated with atopy or recurrent viral infections, can present similarly but has a higher likelihood of persistence into later childhood and may affect a significant percentage of infants with recurrent wheezing episodes.
Clinical Significance:
Accurate differentiation is vital to guide investigations, management strategies, and parental counseling
Misdiagnosis can lead to unnecessary antibiotic use for viral infections or delayed intervention for conditions requiring specific therapies like inhaled corticosteroids or early allergen avoidance.
Clinical Presentation
Symptoms:
Common symptoms include noisy breathing, primarily expiratory wheezing
Other symptoms can include cough, tachypnea, increased work of breathing (nasal flaring, retractions), and reduced feeding
In viral bronchiolitis, symptoms are typically preceded by upper respiratory tract infection (URTI) symptoms like rhinorrhea and low-grade fever
Multi-trigger wheeze may be associated with a history of allergies, eczema, or a family history of asthma.
Signs:
Physical examination may reveal diffuse or localized wheezing on auscultation, tachypnea, intercostal or subcostal retractions, and nasal flaring
Hypoxemia (SpO2 <90%) indicates more severe disease
In viral bronchiolitis, crackles may also be heard
Signs of atopy (eczema) or other allergic manifestations may be present in multi-trigger wheeze.
Diagnostic Criteria:
There are no definitive diagnostic criteria for differentiating the two conditions solely on clinical presentation, especially in the acute phase
Diagnosis is often retrospective based on the pattern of recurrence, response to therapy, and presence of risk factors
A diagnosis of viral bronchiolitis is usually made based on typical clinical presentation during a presumed viral epidemic
Persistent or recurrent wheezing beyond the typical viral season or unresponsive to standard supportive care may suggest multi-trigger wheeze.
Diagnostic Approach
History Taking:
Key history points include the age of onset, frequency and duration of episodes, presence of preceding URTI symptoms, triggers (viral, allergens, irritants), birth history (prematurity, congenital anomalies), feeding difficulties, and family history of atopy or asthma
Red flags include recurrent severe episodes, failure to thrive, persistent hypoxemia, and focal chest findings.
Physical Examination:
A thorough respiratory examination is essential
Auscultate for the presence, timing (inspiratory vs
expiratory), and distribution of wheezing
Assess for signs of increased work of breathing and accessory muscle use
Examine for signs of atopy (eczema) and evaluate general well-being, hydration, and feeding
Palpate for hepatosplenomegaly and listen for cardiac murmurs.
Investigations:
In most cases of suspected viral bronchiolitis, investigations are not required
Chest X-ray is usually not indicated but may be considered in severe cases or if alternative diagnoses are suspected to rule out pneumonia or atelectasis
Pulse oximetry is crucial for assessing oxygenation
For recurrent or persistent wheezing suggestive of multi-trigger wheeze, investigations like complete blood count (CBC) to rule out infection, and possibly allergy testing (skin prick tests or specific IgE) later in infancy or childhood may be considered
Viral respiratory panel (PCR) can confirm specific viral etiologies in bronchiolitis.
Differential Diagnosis:
Other causes of wheezing in infancy include foreign body aspiration, congenital anomalies (tracheomalacia, bronchomalacia, vascular rings), gastroesophageal reflux disease (GERD) with aspiration, cystic fibrosis, immunodeficiency, and early-onset asthma
Persistent wheezing unresponsive to initial management warrants investigation for these differentials.
Management
Initial Management:
For episodic viral bronchiolitis, management is primarily supportive
This includes ensuring adequate hydration, monitoring for respiratory distress and hypoxemia, and providing humidified air
Saline nasal drops and suction can help clear nasal secretions
Hospitalization is indicated for significant respiratory distress, hypoxemia, or dehydration.
Medical Management:
Bronchodilators (e.g., albuterol) are generally NOT recommended for typical viral bronchiolitis as they have shown minimal benefit and can even exacerbate symptoms
However, they may be considered in infants with a strong suspicion of reactive airway disease or a history of asthma
Inhaled corticosteroids are generally not indicated for acute viral bronchiolitis but may be used for infants with recurrent wheezing and suspected atopy, particularly after viral infections have resolved.
Supportive Care:
Adequate fluid intake is paramount to prevent dehydration, which can worsen respiratory effort
Monitor vital signs closely, including heart rate, respiratory rate, and oxygen saturation
Frequent small feeds may be better tolerated
Chest physiotherapy (percussion and vibration) is generally not recommended as it is not proven to be effective and can increase distress.
Long Term Management:
For multi-trigger wheeze, long-term management may involve inhaled corticosteroids, particularly if symptoms are persistent or recurrent
Identification and avoidance of specific triggers (e.g., allergens, irritants like smoke) are important
Management of associated atopic conditions like eczema is also crucial
Parents should be educated on recognizing early signs of exacerbations and managing them at home.
Complications
Early Complications:
Complications of severe bronchiolitis include respiratory failure requiring mechanical ventilation, secondary bacterial infections (e.g., pneumonia, otitis media), and apnea
Dehydration due to poor feeding is also common.
Late Complications:
Recurrent wheezing episodes may persist, leading to a diagnosis of early-onset asthma in later childhood
Some infants may develop persistent airway hyperresponsiveness.
Prevention Strategies:
Preventing viral infections through good hand hygiene and avoiding close contact with sick individuals is key
Smoking cessation in the household and avoiding exposure to environmental irritants (e.g., smoke, strong perfumes) can also help
For infants at high risk, palivizumab prophylaxis may be considered for RSV prevention.
Prognosis
Factors Affecting Prognosis:
Factors influencing prognosis include the severity of the initial episode, the presence of underlying risk factors (prematurity, congenital heart disease, genetic conditions), and the presence of atopy
Most infants with episodic viral bronchiolitis recover fully with no long-term sequelae.
Outcomes:
The majority of infants with uncomplicated viral bronchiolitis experience a full recovery within 1-2 weeks, though cough may persist for several weeks
Infants with multi-trigger wheeze may have a more protracted course with recurrent episodes, but with appropriate management, many achieve symptom control.
Follow Up:
Follow-up is generally not required for typical viral bronchiolitis unless symptoms are prolonged or there are concerns for complications
Infants with recurrent wheezing or suspected multi-trigger wheeze should have regular follow-up with their pediatrician or a pediatric pulmonologist to monitor their condition, adjust management, and assess for the development of asthma.
Key Points
Exam Focus:
Differentiate between transient viral bronchiolitis and persistent/recurrent multi-trigger wheeze
Recognize that bronchodilators are generally ineffective for viral bronchiolitis
Understand supportive care as the cornerstone of management
Identify risk factors for more severe disease and recurrence.
Clinical Pearls:
Always consider foreign body aspiration in unilateral wheezing or sudden onset of symptoms
Palpate the abdomen for hepatosplenomegaly in the context of recurrent respiratory issues to consider conditions like cystic fibrosis
Educate parents about the self-limiting nature of viral bronchiolitis and potential triggers for recurrent wheeze.
Common Mistakes:
Overuse of bronchodilators and antibiotics in viral bronchiolitis
Failure to consider foreign body aspiration or other underlying conditions in non-resolving or recurrent wheezing
Inadequate hydration or failure to monitor oxygen saturation in moderately to severely ill infants.