What is bronchiolitis?

Bronchiolitis is an infection of the lower respiratory tract that usually affects infants. There is swelling in the smaller airways or bronchioles of the lung, which causes obstruction of air in the smaller airways.

What causes bronchiolitis?

The most common cause of bronchiolitis is a virus, most frequently the respiratory syncytial virus (RSV). However, many other viruses have been involved, including:

  • parainfluenza virus

  • adenovirus

  • influenza

  • human metapneumovirus

Some bacteria can also cause bronchiolitis. These include:

Initially, the virus causes an infection in the upper respiratory tract, and then spreads downward into the lower tract. The virus causes inflammation and even death of the cells inside the respiratory tract. This leads to obstruction of airflow in and out of the child's lungs.

Facts about bronchiolitis:

  • Bronchiolitis usually occurs in the winter and early spring.

  • The most common age group affected by bronchiolitis is 3 to 6 months of age.

  • More boys are usually affected than girls.

  • The following risk factors increase the likelihood that a child will develop bronchiolitis:

    • exposure to smoke

    • day care attendance

    • having older children in the home

    • an infant that is not breastfed

  • Seventy-five percent of bronchiolitis occurs in the first year of life.

What are the symptoms of bronchiolitis?

The following are the most common symptoms of bronchiolitis. However, each child may experience symptoms differently. Symptoms may include:

  • common cold symptoms, including:

    • runny nose

    • congestion

    • fever

    • cough (the cough may become more severe as the condition progresses)

  • changes in breathing patterns (the child may be breathing fast or hard; you may hear wheezing, or a high-pitched sound)

  • decreased appetite (infants may not eat well)

  • irritability

  • vomiting

The symptoms of bronchiolitis may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.

How is bronchiolitis diagnosed?

Bronchiolitis is usually diagnosed solely on the history and physical examination of the child. Many tests may be ordered to rule out other diseases, such as pneumonia or asthma. In addition, the following tests may be ordered to help confirm the diagnosis:

  • chest x-rays - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.

  • blood tests/blood gases

  • pulse oximetry - an oximeter is a small machine that measures the amount of oxygen in the blood. To obtain this measurement, a small sensor (like a Band-Aid) is taped onto a finger or toe. When the machine is on, a small red light can be seen in the sensor. The sensor is painless and the red light does not get hot.

  • nasopharyngeal swab - for respiratory syncytial virus (RSV) and other respiratory viruses. These tests yield rapid results for presence of RSV or other viruses.

Treatment for bronchiolitis:

Specific treatment for bronchiolitis will be determined by your child's physician based on:

  • your child's age, overall health, and medical history

  • extent of the disease

  • your child's tolerance for specific medications, procedures, or therapies

  • expectations for the course of the disease

  • your opinion or preference

Most cases are mild and can be treated at home. Because there is no cure for the disease, the goal of treatment is supportive of the symptoms. Antibiotics are ineffective in the treatment of bronchiolitis. Some infants, if they are having severe breathing problems, may be treated in the hospital. While in the hospital, treatment may include:



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