Overview
Definition:
Bronchiolitis is a common viral lower respiratory tract infection that affects infants and young children, typically under two years of age
It is characterized by inflammation and obstruction of the bronchioles, leading to increased mucus production, edema, and cell necrosis.
Epidemiology:
It is the leading cause of infant hospitalization and is most common in infants between 3 to 6 months old
Respiratory Syncytial Virus (RSV) is the most frequent causative agent, accounting for up to 80% of cases
Other viruses include human metapneumovirus, adenovirus, and rhinovirus.
Clinical Significance:
Bronchiolitis is a significant cause of morbidity in infants, leading to hospitalization, respiratory failure, and in severe cases, death
Understanding evidence-based inpatient guidelines, particularly regarding oxygenation and respiratory support like HFNC, is crucial for optimal patient outcomes and efficient resource utilization, a key area for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Typically begins with upper respiratory tract symptoms such as rhinorrhea, cough, and mild fever
Within a few days, lower respiratory tract symptoms emerge, including worsening cough, wheezing, tachypnea, and respiratory distress
Feeding difficulties and irritability are common.
Signs:
Physical examination may reveal tachypnea, retractions (subcostal, intercostal, suprasternal), nasal flaring, grunting, diffuse wheezing, and crackles on auscultation
Hypoxia may be present, indicated by cyanosis
Signs of dehydration or significant work of breathing requiring advanced support are critical indicators.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on characteristic symptoms and signs in an infant less than 2 years of age, especially during the peak season for RSV
Laboratory or imaging confirmation is usually not required for typical cases
Criteria for hospitalization include significant respiratory distress, hypoxia, dehydration, feeding intolerance, or underlying risk factors.
Diagnostic Approach
History Taking:
Key history points include age of onset, duration of symptoms, nature of cough (dry vs
productive), presence of fever, feeding status, fluid intake and output, exposure to sick contacts, and any prior episodes of wheezing or respiratory illness
Red flags include sudden worsening of breathing, apnea, lethargy, or inability to feed.
Physical Examination:
A systematic examination should focus on the respiratory system: assess respiratory rate, pattern of breathing (presence of retractions, nasal flaring, grunting), auscultate lung fields for wheezing, crackles, and air entry, and assess for signs of dehydration, cyanosis, and altered mental status
Assess for cardiac murmurs to rule out congenital heart disease.
Investigations:
Routine investigations are generally not indicated for uncomplicated bronchiolitis
Chest X-ray may show hyperinflation, peribronchial thickening, or atelectasis, but it is not usually necessary for diagnosis and can be normal
Viral studies (e.g., RSV antigen detection or PCR) can confirm the etiology but do not typically alter management
Arterial blood gas (ABG) or venous blood gas (VBG) may be used to assess oxygenation and ventilation in severely ill patients.
Differential Diagnosis:
Other conditions that can mimic bronchiolitis include pneumonia, asthma exacerbation, foreign body aspiration, pertussis, and congenital anomalies of the airway
Distinguishing features include abrupt onset with cyanosis (aspiration), prominent focal findings on auscultation (pneumonia), or recurrent episodes of wheezing (asthma).
Management
Initial Management:
The cornerstone of inpatient management is supportive care
This includes close monitoring of respiratory status, oxygen therapy, and ensuring adequate hydration
Humidified oxygen is administered to maintain oxygen saturation
Intravenous fluids may be required for children unable to maintain oral intake.
Medical Management:
There is no specific antiviral treatment for RSV bronchiolitis
Bronchodilators (e.g., albuterol) are generally NOT recommended in typical bronchiolitis unless there is a clear history of reactive airway disease or if there is significant wheezing unresponsive to initial therapy
Corticosteroids are also not routinely recommended
Antibiotics are only indicated if a co-existing bacterial infection is suspected.
Supportive Care:
Key supportive measures include vigilant monitoring of oxygen saturation (SpO2), respiratory rate, and work of breathing
Adequate hydration is essential, often requiring intravenous fluids if oral intake is poor
Nasal suctioning can help clear secretions and improve feeding and breathing
If respiratory failure progresses, mechanical ventilation may be necessary.
Oxygen Targets:
Current guidelines recommend aiming for an oxygen saturation of ≥90% (some sources may advocate for ≥92%)
Titrate oxygen therapy to maintain the target saturation while minimizing oxygen requirements
Avoid excessive oxygen concentrations as they may lead to hyperoxia
Regular reassessment of oxygen needs is vital.
Hfnc Use:
High-Flow Nasal Cannula (HFNC) is increasingly used for infants with moderate to severe bronchiolitis who require supplemental oxygen and are experiencing significant work of breathing but do not require invasive ventilation
HFNC provides warmed, humidified air at higher flow rates (e.g., 2-8 L/min, depending on infant weight and tolerance), which can reduce dead space, improve oxygenation, facilitate secretion clearance, and reduce the work of breathing
It is considered an alternative to conventional nasal oxygen or non-invasive positive pressure ventilation (NIPPV) in select patients.
Complications
Early Complications:
Apnea, particularly in infants younger than 2 months or those with a history of prematurity, is a significant early complication
Respiratory failure requiring mechanical ventilation and secondary bacterial pneumonia are also possible
Dehydration can occur due to poor oral intake and increased fluid losses.
Late Complications:
Recurrent wheezing and an increased risk of asthma development in later childhood have been associated with severe bronchiolitis
Prolonged respiratory sequelae are rare but can occur in very ill infants.
Prevention Strategies:
Preventive strategies include hand hygiene, avoiding exposure to cigarette smoke, and prompt identification and management of early symptoms
For high-risk infants, palivizumab prophylaxis may be considered for RSV prevention
Careful monitoring of hydration and respiratory status in hospitalized infants can prevent progression to severe complications.
Prognosis
Factors Affecting Prognosis:
Factors associated with a poorer prognosis include young age, prematurity, underlying chronic lung disease or congenital heart disease, neurological impairment, and severe respiratory distress at presentation
The presence of apnea is also a concerning sign.
Outcomes:
The majority of infants with bronchiolitis recover fully with supportive care
Hospitalization typically lasts for 3-5 days
Infants requiring mechanical ventilation may have longer hospital stays
Long-term outcomes are generally good, although some may experience recurrent wheezing.
Follow Up:
Follow-up is recommended for infants who required hospitalization, especially those with risk factors, to monitor for recurrent wheezing or the development of asthma
A follow-up visit typically occurs 4-6 weeks after discharge
Infants discharged home should have clear instructions on when to seek medical attention.
Key Points
Exam Focus:
Understand the typical clinical presentation, diagnostic approach, and supportive management for bronchiolitis
Key areas for DNB/NEET SS include oxygen targets (≥90%), indications and benefits of HFNC, and when to consider other interventions like bronchodilators or steroids (generally not recommended)
Recognize risk factors for severe disease and complications like apnea.
Clinical Pearls:
Prioritize supportive care: oxygen saturation monitoring, hydration, and nasal suctioning
HFNC is a valuable tool for infants with significant work of breathing but without impending respiratory failure
Always consider apnea, especially in younger infants and those with risk factors
Reassess patients frequently for changes in respiratory status.
Common Mistakes:
Over-reliance on unproven treatments like routine bronchodilators or steroids
Failing to adequately monitor fluid balance and respiratory status
Incorrectly titrating oxygen, leading to either hypoxia or unnecessary high concentrations
Not considering apnea in at-risk infants.