What Is Bronchiolitis?

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Bronchiolitis is inflammation of the tiniest airways of the lungs, called the bronchioles. It typically affects infants and children less than 2 years of age and is almost always caused by a respiratory virus. Symptoms include cough, wheezing, and mild fever. Bronchiolitis can usually be diagnosed based on the symptoms. There are no specific treatments for bronchiolitis, although hospitalization with oxygen therapy may be needed for severe cases.

Also Known As

Bronchiolitis is sometimes referred to as pediatric bronchiolitis to differentiate it from bronchiolitis obliterans, a distinct disease entity in adults mainly caused by the inhalation of toxic fumes or complications of a lung transplant.

Bronchiolitis Symptoms

The symptoms of bronchiolitis are related to the obstruction of the bronchioles caused by a lower respiratory infection.

Bronchiolitis typically starts with symptoms similar to a common cold, but then progresses as the bronchioles are affected.

Common symptoms of bronchiolitis include:

  • Runny nose
  • Nasal congestion
  • Mild fever
  • Cough
  • Wheezing
  • Loss of appetite
  • Poor feeding

Even after acute symptoms pass, coughing and wheezing can persist for several weeks. Most cases are bronchiolitis are self-limiting and do not cause any long-term harm or injury.

Some children with bronchiolitis may experience otitis media (middle ear infection), manifesting with ear pain and dizziness, or a urinary tract infection (UTI), recognized by crying during urination and cloudy, foul-smelling urine.

In rare instances, bronchiolitis can progress, leading to severe dehydration (due to poor feeding), respiratory distress (the inability to catch one's breath), or respiratory failure (the inability to keep up with the body's oxygen demands).

When to Call 911

Call 911 or go to your nearest emergency room if your child develops signs of severe bronchiolitis, including:

  • Rapid breathing (tachypnea)
  • Nasal flaring or grunting when breathing
  • Brief gaps in breathing (apnea)
  • Wheezing when exhaling and inhaling
  • Audible crackling sounds when breathing (crepitus)
  • Refusal to eat or inability to eat due to breathing problems
  • Sluggishishness or weakness
  • Bluish skin or nails (cyanosis), caused by the lack of oxygen

Death is rare with pediatric bronchiolitis, affecting only five of every 100,000 children who have the condition in the United States. Even if hospitalization is needed, there is less than a 1% chance of death. Deaths tend to occur if severe symptoms are left untreated.

Causes

Bronchiolitis is almost always caused by one of these respiratory viruses:

The condition starts with an acute infection of the epithelial cells that line the smaller airways of the lungs.

Respiratory Syncytial Virus Symptoms
 Verywell / Gary Ferster

In adults and older children, these common viruses will generally only affect the upper respiratory tract because the immune system is able to limit their spread. But because infants and younger children don't yet have a strong or robust immune response, viruses like these can more readily infiltrate the lower respiratory tract.

When this occurs, the infection will trigger an inflammatory response that causes the bronchioles to constrict (narrow). The inflammation, in turn, causes goblet cells in the airways to release excess mucus, causing obstruction and characteristic wheezing.

Bronchiolitis should not be confused with bronchitis, which can affect adults and children and be caused by an acute infection or a long-term respiratory illness like chronic obstructive pulmonary disease (COPD).

Risk Factors

There are a number of risk factors that can predispose a child to bronchiolitis:

  • Preterm birth
  • Being under 3 months of age at the time of the infection
  • Exposure to secondhand smoke
  • Maternal smoking during pregnancy
  • Congenital heart disease
  • Primary immunodeficiency disease (PIDD)
  • Chronic lung disease and other chronic illnesses

Diagnosis

Bronchiolitis is typically diagnosed with a clinical exam. This would include a physical examination along with a review of the child's symptoms and medical history.

The physical exam would involve listening for breathing sounds with a stethoscope to detect crackles and high-pitched purring or whistling sounds characteristic of lower respiratory infections. Rapid breathing and nasal flaring are other tell-tale signs.

Rapid tests are available to detect specific viruses. But, as the results have little impact on how the infection is managed, they usually aren't performed unless the symptoms are severe or recurrent.

Moreover, certain rapid tests, like those used for RSV, have relatively low specificity and sensitivity, meaning that false-positive or false-negative results are possible. The only exception may be RSV testing during local outbreaks to identify and isolate children to prevent community spread.

Chest X-rays may be ordered but also have their limitations. While they can help identify early respiratory failure in children with severe illness, their usefulness in mild to moderate cases is less certain.

It is not uncommon for children with bronchiolitis to develop a secondary bacterial infection. Because cases of UTI can be treated, a urinalysis may be ordered to check for this.

Otitis media can often be diagnosed with a visual examination of the ear.

Differential Diagnoses

Wheezing and coughing in children can be caused by any number of things. If the diagnosis of bronchiolitis is uncertain, a doctor may perform additional tests to rule out other possible causes. These may include:

Treatment

The treatment of bronchiolitis is mainly supportive. Unless a secondary bacterial infection is identified, antibiotics are not prescribed as they only treat bacteria, not viruses.

With the exception of flu, there are no antiviral drugs able to treat a viral respiratory infection.

The drug Tamiflu (oseltamivir) may reduce the severity of flu in infants and toddlers if taken within 48 hours of the first symptoms. With that said, acute symptoms of bronchiolitis tend to develop within three to five days of exposure, meaning that the drug may be better able to prevent bronchiolitis than treat it once it occurs.

Mild to moderate cases of bronchiolitis tend to resolve fully within two to three weeks without treatment. Most guidelines recommend bed rest with sufficient fluids and nutrition. The avoidance of smoke is also important.

If your child has a fever, ask your pediatrician if you can use Children's Tylenol (acetaminophen) or Children's Motrin (ibuprofen), both of which are available as syrups. Aspirin is not recommended in children due to the risk of Reye's syndrome, a rare but potentially life-threatening condition.

Some parents like using steam inhalation or cool mist humidifiers to relieve respiratory symptoms, although there is little evidence to support their use.

The same applies to inhaled steroids or inhaled bronchodilators (available by prescription); unless there is respiratory distress, these interventions will do little, if anything, to alter the course of the infection.

Hospitalization

As many as 3% of infants in the United States require hospitalization as a result of bronchiolitis. Severe cases often demand more aggressive interventions to avoid or treat respiratory failure, including:

  • Oxygen therapy (typically if oxygen saturation is less than 90%)
  • Intravenous (IV) fluids to treat dehydration
  • Nebulized saline inhalation to aid in mucus clearance
  • Upper airway suctioning to clear airway mucus
  • Mechanical ventilation

As with mild to moderate cases, inhaled bronchodilators or steroids do little to relieve symptoms or aid in recovery.

Prevention

There is no vaccine currently available to prevent RSV, cold viruses, or parainfluenza viruses.

The prevent flu, the Centers for Disease Control and Prevention (CDC) recommends annual flu shots for anyone 6 months of age or older. For people between the ages of 2 and 49, a nasal flu vaccine is also available. Flu vaccination for the entire household is of the utmost importance in families where there are infants, elderly adults, or others at high risk of flu complications.

During cold or flu season, the risk of infection can be reduced with dedicated handwashing, the avoidance of mouth-to-face contact, and the isolation of anyone with a suspected or active infection.

If there is a local outbreak of RSV in daycare or preschool, it is important to pull your child out until health officials tell you that it is safe to return.

Infants at high risk of RSV complications, including preterm babies and those with congenital heart disease, are often given the drug Synagis (palivizumab) to reduce the risk of an RSV infection or the severity of symptoms should an infection occur.

Note, however, that Synagis is not approved for the treatment of RSV. A study published in the journal Pediatrics in 2019 concluded that the drug had no effect, either good or bad, when used in 420 infants with an acute RSV infection.

A Word From Verywell

Bronchiolitis is babies and toddlers can be very distressing to them and their parents. Even though the condition is relatively common and usually resolves on its own, it is important to see your child's pediatrician to confirm the diagnosis. In some cases, wheezing may be a sign of a more serious condition, such as pneumonia.

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