Wheezing is a whistling sound that occurs during breathing when the airways are partially blocked.
Wheezing results from a narrowing or blockage (obstruction) somewhere in the airways. The narrowing may be widespread (as occurs in asthma, chronic obstructive pulmonary disease [COPD], and some severe allergic reactions) or only in one area (as may result from a tumor or a foreign object lodged in an airway).
Overall, the most common causes are
Less common causes:
Wheezing may occur in other disorders that affect the small airways, including heart failure, a severe allergic reaction (anaphylaxis), and inhalation of a toxic substance. Wheezing caused by heart failure is called cardiac asthma.
Sometimes, otherwise healthy people wheeze during a bout of acute bronchitis. In children, wheezing may be caused by bronchiolitis (infection of the lower respiratory tract) or inhalation (aspiration) of a foreign object (see see Table 4: Some Causes and Features of Wheezing).
A person with severe breathing problems (respiratory distress) is evaluated and treated at the same time.
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
In people with wheezing, the following symptoms are of particular concern:
When to see a doctor:
People with warning signs or shortness of breath should go to the hospital emergency department immediately, by ambulance if necessary. People who have wheezing that comes and goes and are not short of breath can usually wait a day or two.
What the doctor does:
Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What doctors find during the history and physical examination often suggests a cause and the tests that may need to be done (see see Table 4: Some Causes and Features of Wheezing).
Doctors determine whether the wheezing is occurring for the first time or has occurred before. If the person has had wheezing before, they determine whether current symptoms are different in nature or severity.
Important clues to a diagnosis are
Other symptoms that can provide clues to the diagnosis include shortness of breath, fever, cough, and sputum production. Doctors ask about the person's history of smoking and exposure to secondhand smoke.
During the physical examination, doctors check the person's temperature and heart and breathing rates. Doctors look for signs of respiratory distress and examine the lungs, particularly how well air moves in and out and whether wheezing seems to affect all of the lungs or only part. A doctor is usually able to detect wheezing by listening with a stethoscope as the person breathes. Loud wheezing can be heard easily, sometimes even without a stethoscope. To hear mild wheezing, doctors may need to listen with a stethoscope while the person exhales forcefully. A persistent wheeze that occurs in one location in smokers may be due to lung cancer. Doctors also examine the heart, nose and throat, limbs, hands, feet, and skin.
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Tests are done to assess severity, determine diagnosis, and identify complications. They usually include the following:
If wheezing has occurred for the first time, a chest x-ray may help in the diagnosis. In people with persistent, repeated, or undiagnosed episodes of wheezing, pulmonary function tests (see Pulmonary Function Testing (PFT)) may be needed to help measure the extent of airway narrowing and to assess the benefits of treatment. If asthma seems possible but is not confirmed by pulmonary function tests, people may be asked to exercise or be given a drug that triggers wheezing in people with asthma. If airway obstruction occurs, asthma can be confirmed.
If doctors suspect a tumor or a foreign object lodged in an airway, they can insert a flexible viewing tube (bronchoscope) into the airway to identify the problem and, if it is an object, remove it.
The main goal of treatment is to treat the underlying disorder.
Bronchodilators (which widen the airways), such as inhaled albuterol, can relieve wheezing. Corticosteroids, taken by mouth for a week or two, can often help relieve an acute episode of wheezing if it is due to asthma or chronic obstructive pulmonary disease. Long-term control of persistent wheezing due to asthma may require inhaled corticosteroids, mast cell stabilizers, and leukotriene inhibitors (see Drugs for Preventing or Treating Attacks).
Histamine-2 (H2) blockers (such as diphenhydramine) given intravenously, corticosteroids (such as methylprednisolone), albuterol taken through a nebulizer, and epinephrine injected under the skin (subcutaneously) are given to people with a severe allergic reaction.
Last full review/revision July 2012 by Noah Lechtzin, MD, MHS