Bronchiolitis is a viral infection that affects the lower respiratory tract of infants and young children under 24 months of age.
Bronchiolitis usually is caused by viruses.
Symptoms include runny nose, fever, cough, wheezing, and difficulty breathing.
The diagnosis is based on symptoms and a physical examination.
Treatment is primarily supporting the child through the illness with fluids and occasionally with oxygen.
Most children do well at home and recover in a few days, but some need to be hospitalized.
The airways resemble an upside-down tree. The trunk is the windpipe (trachea), which branches into large airways called bronchi. The bronchi themselves branch many times into smaller airways, ending in the smallest airways, which are called bronchioles. Bronchioles are as small as 1 half of a millimeter (or 2/100 of an inch) across. Their walls have a thin, circular layer of smooth muscle that can relax or contract, thus changing airway size.
Bronchiolitis typically affects children younger than 24 months of age and is most common among infants 2 to 6 months of age. Each year, 150 million children worldwide are diagnosed with bronchiolitis. Some of these children are hospitalized.
Bronchiolitis often occurs during epidemics and usually in the winter. In the northern hemisphere, most cases occur from December to February. In the southern hemisphere, most cases occur from May to July.
Causes of Bronchiolitis
Bronchiolitis is most often caused by infections with
Common cold virus (rhinovirus)
Parainfluenza and other viruses
Infection with any of these viruses can cause inflammation of the airways. The inflammation causes the airways to narrow, obstructing the flow of air into and out of the lungs. In severe cases, children have a low level of oxygen in their bloodstream.
Infection may be more common or more severe among infants whose mothers smoke cigarettes, particularly those who smoked during pregnancy.
Parents and older siblings can be infected with the same virus, but for them the virus usually causes only a mild cold.
Symptoms of Bronchiolitis
Bronchiolitis starts with symptoms of a cold—runny nose, sneezing, mild fever, and some coughing. After several days, some children develop difficulty breathing, with rapid breathing and a worsening cough. Usually children make a high-pitched sound when breathing out (wheezing). In most infants, the symptoms are mild. Even though infants may breathe somewhat rapidly and be very congested, they are alert, happy, and eating well.
More severely affected infants breathe rapidly and shallowly, use a lot of their respiratory muscles to breathe, and have flaring of their nostrils. They seem fussy and anxious and can become dehydrated because of vomiting and difficulty with drinking. A fever usually is present but not always. More than half of children 3 to 18 months old also develop an ear infection.
Premature infants and infants younger than 2 months old sometimes have episodes where they stop breathing briefly (apnea). In very severe and unusual cases, children in these groups may develop a bluish or grayish discoloration around their mouth (cyanosis) because of a lack of oxygen.
Diagnosis of Bronchiolitis
A doctor's evaluation
Pulse oximetry
Sometimes mucus swab or chest x-ray
Doctors base the diagnosis of bronchiolitis on the symptoms and the physical examination. Doctors measure oxygen levels in the blood by placing a sensor on a finger (pulse oximetry).
For severe cases, doctors sometimes swab mucus from deep inside the nose to try to identify the virus in the laboratory. A chest x-ray or other laboratory tests may be done.
Treatment of Bronchiolitis
At home, fluids by mouth
In the hospital, oxygen therapy and fluids by vein
Home treatment
Most children can be treated at home with fluids and comfort measures.
During the illness, frequent small feedings of clear fluids may be given. Increasing difficulty in breathing, bluish or grayish skin discoloration, fatigue, and dehydration indicate that the child should be hospitalized. Children who have congenital heart disease or lung disease or an impaired immune system may be hospitalized sooner and are far more likely to become quite ill from bronchiolitis.
Hospital treatment
In the hospital, oxygen levels are monitored with a sensor attached to a finger or toe, and oxygen is given by an oxygen tent, nasal tube (cannula), or face mask (see Oxygen administration). Rarely, a ventilator (a breathing machine that helps air get in and out of the lungs) may be needed to assist breathing.
Fluids are given by vein if the child cannot drink adequately.
Inhaled medications that open the airways (bronchodilators) may be tried. Although these medications relieve wheezing and airway narrowing caused by asthma, their effectiveness in treating bronchiolitis is questionable. Corticosteroids (to suppress inflammation) may be beneficial for some children.
Doctors no longer use the antiviral medication ribavirin (given by nebulizer) except for children whose immune system is extremely weak and whose infection is severe. Antibiotics are not helpful unless the child also has a bacterial infection.
Prevention
prevent RSV in infants and young children.
Prognosis for Bronchiolitis
Most children recover at home in 3 to 5 days. However, wheezing and coughing may continue for 2 to 4 weeks. With proper care, the chance of developing serious consequences due to bronchiolitis is low, even for children who need to be hospitalized.
Some children have repeated episodes of wheezing after having had bronchiolitis in early childhood.
