Wheezing

Overall, the most common causes are

• Asthma

• COPD

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 table Some Causes and Features of Wheezing).

In people with wheezing, the following symptoms are of particular concern:

• Labored breathing, weakening efforts to breathe, or a decreased level of consciousness

• Swelling of the face and tongue

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.

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 table 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

• Whether the wheezing started suddenly or gradually

• Whether it comes and goes

• Whether any conditions (such as an upper respiratory infection, exposure to an allergen, particular seasons of the year, cold air, exercise, or feeding in infants) trigger it or make it worse

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 people who smoke may be due to lung cancer. Doctors also examine the heart, nose and throat, limbs, hands, feet, and skin.

Tests are done to assess severity, determine diagnosis, and identify complications. They usually include the following:

• Measurement of oxygen levels in the blood with a sensor placed on a finger (pulse oximetry)

• A chest x-ray (if the diagnosis is unclear)

• Sometimes measurement of gases (oxygen and carbon dioxide) and acidity (pH) in an artery (arterial blood gas analysis)

• Sometimes tests to evaluate how well the lungs are functioning (pulmonary function testing)

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 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 medication 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.