Bronchiolitis is a generic term applied to varied inflammatory processes that affect the bronchioles, which are small conducting airways less than 2 mm in diameter. Disorders associated with bronchiolitis include organ transplantation, connective tissue diseases, and hypersensitivity pneumonitis.
Inhalational injuries as well as postinfectious and drug-induced causes are identified by association with a known exposure or illness prior to the onset of symptoms. Idiopathic cases are characterized by the insidious onset of dyspnea or cough.
Bronchiolitis starts out with symptoms similar to those of a common cold, but then progresses to coughing, wheezing and sometimes difficulty breathing. Symptoms of bronchiolitis can last for several days to weeks.
Bronchiolitis occurs when a virus infects the bronchioles, which are the smallest airways in your lungs. The infection makes the bronchioles swell and become inflamed. Mucus collects in these airways, which makes it difficult for air to flow freely in and out of the lungs.
Most cases of bronchiolitis are caused by the respiratory syncytial virus (RSV). RSV is a common virus that infects just about every child by 2 years of age. Outbreaks of RSV infection occur every winter, and individuals can be reinfected, as previous infection does not appear to cause lasting immunity. Bronchiolitis also can be caused by other viruses, including those that cause the flu or the common cold.
The viruses that cause bronchiolitis are easily spread. You can contract them through droplets in the air when someone who is sick coughs, sneezes or talks. You can also get them by touching shared objects — such as utensils, towels or toys — and then touching your eyes, nose or mouth.
Acute bronchiolitis can be seen seen following viral infections.
Constrictive bronchiolitis (also referred to as obliterative bronchiolitis, or bronchiolitis obliterans) is relatively infrequent although it is the most common finding following inhalation injury. It may also be seen in rheumatoid arthritis; medication reactions; and chronic rejection following heart-lung, lung, or bone marrow transplant.
Patients with constrictive bronchiolitis have airflow obstruction on spirometry; minimal radiographic abnormalities; and a progressive, deteriorating clinical course.
Proliferative bronchiolitis is associated with diverse pulmonary disorders, including infection, aspiration, ARDS, hypersensitivity pneumonitis, connective tissue diseases, and organ transplantation. Compared with constrictive bronchiolitis, proliferative bronchiolitis is more likely to have an abnormal chest radiograph.
Cryptogenic organizing pneumonitis (COP) formerly referred to as bronchiolitis obliterans with organizing pneumonia (BOOP) affects men and women between the ages of 50 and 70 years, typically with a dry cough, dyspnea, and constitutional symptoms that may be present for weeks to months prior to seeking medical attention. A history of a preceding viral illness is present in half of cases. Pulmonary function testing typically reveals a restrictive ventilatory defect and impaired oxygenation. The chest radiograph frequently shows bilateral patchy, ground-glass or alveolar infiltrates, although other patterns have been described.
Follicular bronchiolitis is most commonly associated with connective tissue disease, especially rheumatoid arthritis and Sjögren syndrome, and with immunodeficiency states.
Respiratory bronchiolitis usually occurs without symptoms or physiologic evidence of lung impairment.
Diffuse panbronchiolitis is most frequently diagnosed in Japan. Men are affected about twice as often as women, two-thirds are nonsmokers, and most patients have a history of chronic pansinusitis. Patients complain of dyspnea, cough, and sputum production, and chest examination shows crackles and rhonchi. Pulmonary function tests reveal obstructive abnormalities, and the chest radiograph shows a distinct pattern of diffuse, small, nodular shadows with hyperinflation.
When to see a doctor
If it’s difficult to get your child to eat or drink and his or her breathing becomes more rapid or labored, call your child’s doctor. This is especially important if your child is younger than 12 weeks old or has other risk factors for bronchiolitis — including premature birth or a heart or lung condition.
The following signs and symptoms are reasons to seek prompt medical attention:
- Audible wheezing sounds
- Breathing very fast — more than 60 breaths a minute (tachypnea) — and shallowly
- Labored breathing — the ribs seem to suck inward when the infant inhales
- Sluggish or lethargic appearance
- Refusal to drink enough, or breathing too fast to eat or drink
- Skin turning blue, especially the lips and fingernails (cyanosis)
Constrictive bronchiolitis is relatively unresponsive to corticosteroids and is frequently progressive. Corticosteroids are effective in two-thirds of patients with proliferative bronchiolitis, and improvement can be prompt. Therapy is initiated with prednisone at 1 mg/kg/day orally for 1–3 months. The dose is then tapered slowly to 20–40 mg/day, depending on the response, and weaned over the subsequent 3–6 months as tolerated.
Relapses are common if corticosteroids are stopped prematurely or tapered too quickly. Most patients with COP recover following corticosteroid treatment. Diffuse panbronchiolitis is effectively treated with azithromycin.
Complications of severe bronchiolitis may include:
- Blue lips or skin (cyanosis), caused by lack of oxygen
- Pauses in breathing (apnea), which is most likely to occur in premature babies and in babies within the first two months of life
- Low oxygen levels and respiratory failure
If these occur, your child may need to be in the hospital. Severe respiratory failure may require that a tube be inserted into the windpipe (trachea) to help the child’s breathing until the infection has run its course.
If your baby was born prematurely, has a heart or lung condition, or has a depressed immune system, watch closely for beginning signs of bronchiolitis. The infection can quickly become severe. In such cases, your child will usually need hospitalization.
Because the viruses that cause bronchiolitis spread from person to person, one of the best ways to prevent it is to wash your hands frequently — especially before touching your baby when you have a cold or other respiratory illness. Wearing a face mask at this time is appropriate.
If your child has bronchiolitis, keep him or her at home until the illness is past to avoid spreading it to others.
Other commonsense ways to help curb infection include:
- Limit contact with people who have a fever or cold. If your child is a newborn, especially a premature newborn, avoid exposure to people with colds, especially in the first two months of life.
- Clean and disinfect surfaces. Clean and disinfect surfaces and objects that people frequently touch, such as toys and doorknobs. This is especially important if a family member is sick.
- Cover coughs and sneezes. Cover your mouth and nose with a tissue. Then throw away the tissue and wash your hands or use alcohol-based hand sanitizer.
- Use your own drinking glass. Don’t share glasses with others, especially if someone in your family is ill.
- Wash hands often. Frequently wash your own hands and those of your child. Keep an alcohol-based hand sanitizer handy for yourself and your child when you’re away from home.
- Breast-feed. Respiratory infections are significantly less common in breast-fed babies.