Bronchiolitis

Introduction

Bronchiolitis is a common viral infection of the small airways (bronchioles) in infants and young children, typically under two years old. It often kicks off with a runny nose and mild cough, but can progress to wheezing and difficulty breathing. This condition impacts daily life for both the little one and their families, leading to sleepless nights, frequent pediatrician visits, and sometimes hospital stays. In this article, we’ll dive into symptoms, causes, treatment options, and outlook, so you know what to expect and when to seek help.

Definition and Classification

Medically, bronchiolitis refers to inflammation of the bronchioles—the tiny air passages in the lungs—most often caused by a viral infection. It’s classified as an acute respiratory infection, usually peaking in the winter months. Unlike chronic conditions such as asthma, bronchiolitis is typically self-limited over a few weeks. There aren’t benign versus malignant forms here; it’s an acute, sometimes severe, viral condition. Subtypes include RSV bronchiolitis (respiratory syncytial virus), human metapneumovirus bronchiolitis, and less commonly rhinovirus or parainfluenza-induced.

Organs/systems involved:

• Lower respiratory tract (bronchioles and alveoli)
• Upper respiratory tract (initial entry point)
• Immune system response

Causes and Risk Factors

Bronchiolitis is most often triggered by viruses, with RSV (respiratory syncytial virus) accounting for roughly 50–80% of cases. Other culprits include:

• Human metapneumovirus
• Rhinovirus (more common in older infants)
• Parainfluenza viruses
• Influenza viruses (seasonal overlaps)

Risk factors can be split into non-modifiable and modifiable:

• Non-modifiable: Age under 12 months (especially under 6 months), prematurity (<37 weeks gestation), congenital heart disease, chronic lung disease of prematurity (bronchopulmonary dysplasia), genetic immune deficiencies
• Modifiable: Exposure to tobacco smoke, crowded daycare environments, older siblings in school, lack of breastfeeding, poor hand hygiene in caregivers

For many, bronchiolitis is a “one-off” viral illness, but some may have recurrent wheezing episodes later, occasionally mislabeled as asthma. The exact reason why some infants get severe disease and others mild is not fully understood—likely a mix of viral load, immune system differences, genetic susceptibility, and environmental exposures.

Pathophysiology (Mechanisms of Disease)

When a virus (most often RSV) infects the nose or throat, it migrates down to the bronchioles. There, it invades the epithelial cells lining these tiny airways, causing cell death and sloughing. This triggers:

• Edema (swelling) of airway walls
• Excess mucous production
• Cell debris accumulation

Combined, these factors lead to narrowing or complete obstruction of bronchioles, especially during exhalation when airway diameter naturally decreases. The result is air-trapping, wheezing sounds, and increased work of breathing. The body mounts an immune response—recruiting white blood cells and releasing cytokines—which further increases inflammation. Oxygen exchange in alveoli can be impaired, so blood oxygen saturation may drop. In severe cases, carbon dioxide retention may develop, signaling respiratory failure risk.

Symptoms and Clinical Presentation

Bronchiolitis typically starts with non-specific upper respiratory signs:

• Runny, stuffy nose
• Low-grade fever (up to 38.5 °C / 101.3 °F)
• Mild cough

After 2–3 days, lower airway involvement leads to:

• Wheezing (high-pitched whistling on exhale)
• Rattly breathing or crackles
• Increased work of breathing (nasal flaring, grunting, chest retractions)
• Rapid breathing (tachypnea)—over 60 breaths/min in infants can signal distress
• Poor feeding or dehydration (due to fatigue and nasal congestion)

Symptoms vary by individual; some babies snore and nap a lot, others are more overtly distressed. Warning signs demanding immediate medical care include:

• Lethargy or unresponsiveness
• Persistent refusal to feed
• Signs of severe dehydration (dry diapers, sunken fontanelle)
• Blue lips or cyanosis
• Marked chest wall retractions or apnea (pauses in breathing)

Bronchiolitis generally peaks around day 5–7 of illness and slowly improves by days 10–14, but cough can linger several weeks.

Diagnosis and Medical Evaluation

Bronchiolitis is primarily diagnosed clinically—meaning by history and physical exam. Key steps include:

• History: Onset of nasal congestion, cough, feeding issues, wheezing
• Physical exam: Listening for wheezes/crackles, observing respiratory effort, measuring oxygen saturation (pulse oximetry)
• Laboratory tests: Rarely needed—viral panels (nasal swabs) can identify RSV or other pathogens but don’t always change management
• Chest X-ray: Reserved for atypical presentations suspecting pneumonia or complications
• Blood tests: Not routine, though may check blood gases or electrolytes in severe cases

It’s important to consider differential diagnoses:

• Asthma (older toddlers, recurrent episodes)
• Congenital heart disease (murmur, poor perfusion)
• Bronchial foreign body (sudden onset, unilateral wheeze)
• Cystic fibrosis (failure to thrive, recurrent infections)

Most infants with moderate bronchiolitis are managed as outpatients, but hospitalization is recommended for those with significant respiratory distress, hypoxia (SpO₂ < 90–92%), dehydration, or at high-risk (premature, chronic lung/heart disease).

Which Doctor Should You See for Bronchiolitis?

If you suspect bronchiolitis—especially in a baby under 2—you’d typically start with your pediatrician or family doctor. They can assess symptoms, listen to the lungs, and decide if further tests or hospitalization are needed. For more severe cases or specialized care, a pediatric pulmonologist or pediatric infectious disease specialist may be consulted.

Wondering “which doctor to see” or “specialist for bronchiolitis”? Here’s a quick guide:

• Primary care provider: First assessment, initial supportive care, and advice on home management.
• Emergency physician: For urgent evaluation if baby shows respiratory distress, dehydration, or high fever.
• Pediatric pulmonologist: For severe or recurrent cases, or if chronic lung disease is suspected.
• Telemedicine consultations: Great for second opinions, interpreting test results, or clarifying persistent cough concerns—but remember, they can’t replace hands-on exams or emergency interventions.

Online care complements in-person checkups: you can use telehealth to ask follow-up questions (“Should I return if wheezing worsens?”), review oxygen readings, or decide if an ER visit is warranted. But if you spot blue lips, pausing breathing, or feeding refusal—go to the ER immediately.

Treatment Options and Management

Currently, there’s no cure-all antiviral for bronchiolitis, so management focuses on supportive, evidence-based measures:

• Hydration: Frequent small feeds or breastfeeds; consider oral rehydration solutions if baby tolerates.
• Oxygen therapy: For hypoxia; delivered via nasal cannula or face mask in hospital.
• High-flow nasal cannula: For moderate to severe distress; provides warmed, humidified oxygen at higher flows to ease breathing.
• Bronchodilators: A single trial of albuterol or salbutamol may be attempted in older infants; continued use only if clear benefit documented.
• Nebulized hypertonic saline: Occasionally used to thin secretions—mixed evidence on its routine use.
• Ribavirin: An antiviral sometimes reserved for high-risk infants (congenital heart disease, severe immunodeficiency), but used rarely due to cost and limited proven benefit.

Supportive treatments like chest physiotherapy, corticosteroids, or antibiotics are not routinely recommended unless there’s a specific indication (e.g., concurrent bacterial infection). Home care tips include humidified air, saline nose drops, and upright positioning to ease breathing. Monitor for dehydration—wet diapers at least every 6–8 hours in young infants is a good sign.

Prognosis and Possible Complications

Most infants fully recover from bronchiolitis within 1–2 weeks, though cough can persist for several weeks. Good prognostic factors include:

• Age over 6 months
• No underlying cardiac or pulmonary disease
• No prematurity
• Mild initial presentation

Possible complications, particularly if untreated or in high-risk babies, include:

• Respiratory failure requiring mechanical ventilation
• Secondary bacterial pneumonia or otitis media
• Apnea episodes (especially in premature infants)
• Persistent wheezing or reactive airway disease later in childhood

Long-term outcomes are generally good, though some children with severe bronchiolitis may have recurrent wheezing or increased asthma risk by school age. Regular follow-up ensures timely intervention if chronic issues emerge.

Prevention and Risk Reduction

You can’t completely prevent viral exposure, but risk reduction strategies help lower severe bronchiolitis rates:

• Hand hygiene: Frequent hand-washing by caregivers and visitors; alcohol-based sanitizer as an adjunct.
• Breastfeeding: Provides passive immunity; breastfed infants have lower hospitalization rates.
• Avoid smoke exposure: Tobacco smoke irritates infant airways and increases severity.
• Palivizumab: A monoclonal antibody given monthly during RSV season to high-risk infants (e.g., extreme prematurity, significant congenital heart disease).
• Limit crowds: During RSV peak season, reduce daycare or public gathering time if baby is very young or high-risk.

Early detection via pulse oximetry at home isn’t standard, but being aware of rapid breathing or feeding troubles helps prompt earlier medical advice. Annual vaccination for influenza in household contacts also reduces risk of flu-associated bronchiolitis.

Myths and Realities

There’s a lot of home remedies and myths around bronchiolitis—let’s bust some:

• Myth: Chest physiotherapy (percussing chest) cures bronchiolitis.
  Reality: No strong evidence supports routine chest PT; may even cause distress.
• Myth: All babies with wheeze have asthma.
  Reality: Bronchiolitis wheezing is viral, usually one-time; asthma is chronic and variable over months.
• Myth: Antibiotics help bronchiolitis.
  Reality: It’s viral; antibiotics aren’t indicated unless there’s bacterial superinfection.
• Myth: Cough syrups speed recovery.
  Reality: No proven benefit in infants; some can be harmful by causing sedation or choking risks.
• Myth: A humidifier in the room will “kill RSV.”
  Reality: Humidifiers ease congestion but don’t eradicate the virus; cleaning them improperly may even foster mold.

Popular belief sometimes suggests vitamin C or zinc prevents bronchiolitis—evidence is lacking in infants. Focus on proven methods: handwashing, breastfeeding, and palivizumab for eligible babies.

Conclusion

Bronchiolitis is a self-limited, viral inflammation of the small airways in infants, peaking around day 5–7 and resolving over 1–2 weeks. It presents with upper respiratory signs transitioning to wheezing and increased work of breathing. Diagnosis is mostly clinical, with supportive care as the mainstay of treatment. Most little ones bounce back fully, though high-risk infants may develop severe complications. Prevention hinges on hygiene, smoke avoidance, and targeted prophylaxis like palivizumab. If your baby shows severe distress—blue lips, lethargy, lack of feeding—seek immediate medical attention. Remember, professional evaluation and timely care are key to smooth recovery.

Frequently Asked Questions (FAQ)

• Q1: What age is most affected by bronchiolitis?
  A: Babies under one year—especially 2–6 months—are most prone due to small airways and immature immunity.
• Q2: Is bronchiolitis contagious?
  A: Yes, it spreads via droplets and direct contact. Hand hygiene reduces transmission.
• Q3: How long does bronchiolitis last?
  A: Typically 1–2 weeks; cough may linger up to 3–4 weeks post-infection.
• Q4: Can adults get bronchiolitis?
  A: Rarely—adults have larger airways and stronger immunity; they might get a cold instead.
• Q5: When should I go to the ER?
  A: If baby isn’t feeding, shows blueish skin, has pauses in breathing, or extreme lethargy.
• Q6: Are antibiotics needed?
  A: No, because bronchiolitis is viral. Antibiotics only if a secondary bacterial infection is confirmed.
• Q7: Is a nebulizer useful?
  A: Nebulized saline might ease congestion; bronchodilators are tried once but only continued if helpful.
• Q8: Does RSV always cause hospitalization?
  A: No, most RSV bronchiolitis cases are mild and managed at home. Hospitalization reserved for severe distress or high-risk infants.
• Q9: How can I help my child breathe easier at home?
  A: Use saline nose drops, suction small noses, keep hydrated, and elevate the head slightly during feeds or sleep.
• Q10: Can siblings bring RSV home?
  A: Yes, older siblings in school can transmit RSV; encourage them to wash hands often.
• Q11: Do vitamin supplements prevent bronchiolitis?
  A: There’s no strong evidence supporting vitamins like C or D in preventing viral bronchiolitis in infants.
• Q12: Is wheezing same as asthma?
  A: Not always. Viral wheeze from bronchiolitis is usually one-time; asthma is a chronic airway hyperreactivity.
• Q13: Can RSV infection recur?
  A: Yes, RSV re-infections happen, but subsequent episodes are often milder as immunity builds.
• Q14: Does bronchiolitis affect long-term lung health?
  A: Most children recover fully, though a subset may develop recurrent wheezing or mild airflow issues later.
• Q15: Should I use a home oximeter?
  A: Home pulse oximetry isn’t standard but can flag low oxygen; however, readings vary by device and handling, so use it only alongside clinical signs and provider guidance.