Bronchitis is inflammation of the large airways that branch off the trachea (bronchi), usually caused by infection but sometimes caused by irritation from inhaling gases, smoke, dust particles, or some types of pollution.
Symptoms lasting up to 90 days are usually classified as acute bronchitis; symptoms lasting longer, sometimes for months or years, are usually classified as chronic bronchitis. When chronic bronchitis occurs with decreased expiratory airflow, it is considered a defining characteristic of chronic obstructive pulmonary disease (see see Chronic Obstructive Pulmonary Disease (COPD)). This chapter discusses acute bronchitis only.
Acute bronchitis can be caused by infection or by exposure to irritants.
Infectious bronchitis occurs most often during the winter and is most often caused by viruses. Viral bronchitis may be caused by a number of common viruses, including the influenza virus. Even after a viral infection has resolved, the irritation it causes can continue to cause symptoms for weeks.
Infectious bronchitis may also be caused by bacteria. Often bacterial bronchitis follows a viral upper respiratory infection. Acute bronchitis is more likely to be caused by bacteria in people who smoke. Mycoplasma pneumoniae and Chlamydia pneumoniae are the bacteria that often cause acute bronchitis in young adults. In rare cases, Bordetella pertussis infection (whooping cough) may cause acute bronchitis.
Smokers and people who have chronic lung diseases may have repeated attacks of acute bronchitis. These episodes may be caused by bacteria, viruses, irritation from inhaling smoke, or a combination of factors. Undernutrition increases the risk of upper respiratory tract infections and subsequent acute bronchitis, especially in children and older people. Chronic sinus infections, bronchiectasis (see see Bronchiectasis), and allergies also increase the risk of repeated episodes of acute bronchitis. Children with enlarged tonsils and adenoids may have repeated episodes of bronchitis.
Irritative bronchitis (also called industrial or environmental bronchitis) may be caused by exposure to various mineral and vegetable dusts as well as cigarette smoke and smog. Exposure to fumes from strong acids, ammonia, some organic solvents, chlorine, hydrogen sulfide, sulfur dioxide, and bromine can also cause irritative bronchitis.
Infectious bronchitis generally begins with the symptoms of a common cold: runny nose, sore throat, fatigue, and chilliness. Back and muscle aches together with a slight fever (100° to 101° F, or 37.5° to 38° Celsius [C]) may be present, particularly if the infection is due to influenza. The onset of cough (usually dry at first) signals the beginning of acute bronchitis. With viral bronchitis, small amounts of white mucus are often coughed up. This mucus often changes from white to green or yellow. The color change does not mean there is a bacterial infection. Color change means only that cells associated with inflammation have moved into the airway and are coloring the sputum.
With severe bronchitis, fever may be slightly higher at 101° to 102° F (38° to 39° C) and may last for 3 to 5 days, but higher fevers are unusual unless bronchitis is caused by influenza. Cough is the last symptom to subside and often takes several weeks or even longer to do so. Viruses can damage the epithelial cells lining the bronchi, and the body needs time to repair the damage. Airway hyperreactivity, which is a short-term narrowing of the airways with impairment or limitation of the amount of air flowing into and out of the lungs, is common with acute bronchitis. The impairment of airflow may be triggered by common exposures, such as inhaling mild irritants (for example, perfume, strong odors, or exhaust fumes) or cold air. If the impairment of airflow is severe, the person may be short of breath. Wheezing, especially after coughing, is common.
Serious complications, such as acute respiratory failure (see see Respiratory Failure) or pneumonia (see see Overview of Pneumonia), usually occur only in people who have advanced underlying chronic lung disease (such as chronic obstructive pulmonary disease), who are older, or who have problems with immune defenses.
Doctors usually make a diagnosis of bronchitis based on the symptoms. Fevers that are high or prolonged or both could indicate the presence of pneumonia. Doctors may hear wheezing during the physical examination. A chest x-ray is sometimes done to exclude pneumonia, mainly when doctors hear wheezing or congestion in the lungs or when the person is short of breath.
A sample taken from the throat can be used to detect influenza. Sputum is generally only examined if doctors find evidence of pneumonia on a chest x-ray or during the examination. If a cough persists for more than 2 months, a chest x-ray is done to exclude an underlying lung disease, such as lung cancer.
Cough medicines (see Cough suppressants) can be used to suppress a dry, disturbing cough, particularly when it interferes with sleep. However, a cough that produces a lot of sputum usually should not be suppressed. Expectorants may help to thin secretions and make them easier to cough up, but whether this is helpful is not clear. Adults may take aspirin, acetaminophen, or ibuprofen to reduce fever and general feelings of illness, but children should take only acetaminophen or ibuprofen, not aspirin. People with acute bronchitis, especially those who have a fever, should drink plenty of fluid.
Antibiotics are not used to treat bronchitis except for people whose infection is caused by Bordetella pertussis or for some people with chronic obstructive pulmonary disease. Antibiotics do not help people with viral bronchitis. However, if influenza is the suspected cause, treatment with an antiviral drug may be helpful if given within 48 hours of onset of symptoms.
In children, very mild symptoms of limited airflow can be helped with cool-mist humidifiers or steam vaporizers. In more severely affected children and adults who are wheezing, inhaled bronchodilators, which widen the bronchi, can be used to open the airways and reduce wheezing. Corticosteroids, usually given by means of a metered-dose inhaler (see Fig. 2: How to Use a Metered-Dose Inhaler), are also sometimes used to diminish cough and inflammation and hyperreactivity of the airways, especially when the cough persists after the infection has resolved.
Last full review/revision April 2008 by John G. Bartlett, MD