Definition

Bronchiolitis is a sudden and rapid inflammation of the airways, resulting in the blockage of one of the lower airway branches, known as bronchioles, due to infection. Bronchiolitis is often caused by viruses and primarily affects infants and children under 2 years old.

Bronchiolitis is the most common reason for hospitalization in infants under 12 months old. Approximately 75,000–125,000 infants under 1 year old in America are hospitalized due to bronchiolitis each year.

Causes

About 50% of bronchiolitis cases are caused by respiratory syncytial virus (RSV) infection, commonly affecting the respiratory tract. Parainfluenza and adenoviruses follow. RSV often targets infants under 2 years old and spreads quickly through droplet transmission (when someone coughs, talks, or sneezes). The virus can also spread through shared items like towels, toys, or utensils. There is no strong evidence that bacteria can cause bronchiolitis.

Bronchiolitis occurs when a virus infects the bronchioles (minor branches of the respiratory tract). This infection leads to inflammation and swelling of the bronchioles. The inflammatory process causes increased mucus production, leading to the blockage of the airways, making it difficult for air to enter and exit the lungs. This can result in trapped air in the lungs, obstructing the exchange of oxygen and carbon dioxide within the lungs, leading to respiratory distress in infants.

Risk factor

Bronchiolitis commonly occurs in infants and children under 2 years old. Due to their underdeveloped lungs and immune systems, infants aged 3 months or less are at a higher risk of bronchiolitis.

Factors that can increase the risk of a child experiencing severe bronchiolitis include:

• Premature infants <30 weeks gestational age
• Males are more likely to experience bronchiolitis (1.7:1 ratio)
• Not receiving breastfeeding; approximately 81% of malnourished infants and 72% of adequately nourished infants who do not receive exclusive breastfeeding experience bronchiolitis
• Living in crowded environments
• Young maternal age
• Having other medical conditions (heart or lung disease)
• Experiencing immunodeficiency (weakened immune system)
• Exposure to cigarette smoke
• Having siblings in daycare or school

Symptoms

In the first few days, the signs and symptoms of bronchiolitis resemble those of a common cold, a viral infection affecting the nose and throat, including:

• Runny or stuffy nose
• Nasal congestion
• Cough
• Low-grade fever (not always present)

Around several days to one week after experiencing these symptoms, the child will have difficulty breathing, with audible wheezing sounds heard with each breath. The child may also experience wheezing breaths, coughing to the point of vomiting, fussiness, and decreased appetite.

Diagnosis

The doctor will clinically diagnose bronchiolitis by considering the emerging symptoms, primary complaints, the child's risk factors, and the physical examination results. The doctor will inquire about when the symptoms appeared, the severity of respiratory distress experienced, history of contact with sick relatives or family members, breastfeeding history, and immunization history.

The doctor will examine the child's breathing to look for signs of respiratory distress and listen to the child's lung sounds. The doctor will also ensure signs of dehydration in the child if they experience decreased appetite and refusal to drink. The doctor needs to confirm that the symptoms experienced by the child are bronchiolitis and not other conditions such as asthma, pneumonia, lung inflammation, or foreign body aspiration (environmental object entering the airway and causing obstruction).

Some additional tests that the doctor may perform as indicated include:

• Chest X-ray to evaluate the child's lungs using a plain film to rule out pneumonia. However, this is rarely needed if the child has uncomplicated bronchiolitis.
• Blood tests to confirm the presence of infection.
• Arterial blood gas analysis is not routinely performed but can be done if the child experiences severe respiratory distress.

Management

Bronchiolitis generally lasts 2–3 weeks and improves thereafter. Children are usually treated at home and given medications only to relieve symptoms. Children who are hospitalized are those with severe symptoms or complications. Parents should remain vigilant for changes in their child's breathing patterns during home care.

Because bronchiolitis is caused by a virus, antibiotics do not benefit it. However, the doctor may prescribe antibiotics if the child has other infections, such as bacterial ear infections or pneumonia, concurrently with bronchiolitis. Other medications, such as bronchodilators (to relieve symptoms of airway narrowing) and corticosteroids (which have anti-inflammatory effects), do not significantly benefit bronchiolitis.

If a child needs to be hospitalized due to severe symptoms, the doctor may perform nebulization (therapy with vaporized medication) to assist the child's breathing. Additionally, the child may receive fluids through intravenous infusion if there are signs of dehydration or fluid deficiency.

Complications

Complications that may arise from severe bronchiolitis include:

• Bluish skin due to oxygen deficiency in body tissues
• Breathing cessation (apnea), which occurs more frequently in premature infants or infants under two months old
• Dehydration or fluid deficiency
• Respiratory failure

If the above occurs, the infant should be promptly treated at the hospital. In severe cases, infants may require respiratory assistance using a tube inserted into the airway. Prematurely born infants, those with certain medical conditions (heart and lung abnormalities), or those with weakened immune systems are more often hospitalized due to severe bronchiolitis.

Prevention

Because the viruses that cause bronchiolitis are easily spread, the primary prevention is always washing hands before touching your baby. If you have the flu, wear a mask when in close contact with your baby. If your baby has bronchiolitis, avoid taking your baby outside temporarily to prevent spreading the virus to others. Currently, there is no specific vaccine to prevent bronchiolitis in infants.

Some other preventive measures include:

• Limiting contact with sick individuals
• Avoid excessive contact between your baby and others to prevent the baby from being exposed to viruses. This is especially important if your baby is less than 2 months old or born prematurely.
• Regularly clean the baby's environment. Items around the baby, such as toys and doorknobs, should be cleaned daily, especially if there are other sick family members.
• Covering your nose and mouth when coughing. Always cover your nose and mouth when coughing with the inside of your elbow or a tissue. Dispose of your tissue immediately and wash your hands before touching the baby.
• Providing exclusive breastfeeding. Bronchiolitis is less likely to occur in babies who receive exclusive breastfeeding.

When to see a doctor?

If your baby experiences decreased appetite, refuses to eat or drink, breathes rapidly, or has difficulty breathing, immediately consult your pediatrician. This condition needs to be addressed promptly, especially if your child is under 12 weeks old or has bronchiolitis risk factors, such as being born prematurely or having other medical conditions.

Bronchiolitis rarely causes babies to appear seriously ill. However, if your baby shows some of the signs below, promptly go to the hospital for immediate treatment.

• Your baby's breathing sounds wheezy
• Your baby breathes very rapidly and shallowly (more than 60 breaths per minute)
• Your baby appears to have difficulty breathing (the baby's rib bones appear to retract inward when breathing)
• Your baby looks weak and apathetic
• Your baby refuses to eat or drink
• Your child's skin turns blue, especially around the mouth and fingertips