Wheezing is a high-pitched, whistling sound that occurs during breathing when the airways are partially blocked. (See also Wheezing in Infants and Young Children Wheezing in Infants and Young Children Wheezing is a relatively high-pitched whistling sound that occurs during breathing when the airways are partially blocked or narrowed. Wheezing is caused by a narrowing of the airways. Other... read more .)
Causes of Wheezing
Wheezing results from a narrowing or partial 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 Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more , a severe allergic reaction ( anaphylaxis Anaphylactic Reactions Anaphylactic reactions are sudden, widespread, potentially severe and life-threatening allergic reactions. Anaphylactic reactions often begin with a feeling of uneasiness, followed by tingling... read more ), and inhalation of a toxic substance Gas and Chemical Exposure Symptoms depend on which gas or chemical is inhaled and how deeply and for how long it was inhaled. Symptoms may include irritation of the eyes or nose, cough, blood in the sputum, and shortness... read more . Wheezing caused by heart failure is called cardiac asthma.
Sometimes, otherwise healthy people wheeze during a bout of acute bronchitis Acute Bronchitis Acute bronchitis is inflammation of the windpipe (trachea) and the airways that branch off the trachea (bronchi) caused by infection. Acute bronchitis is usually caused by a viral upper respiratory... read more . In children, wheezing may be caused by bronchiolitis Bronchiolitis 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... read more (infection of the lower respiratory tract) or inhalation (aspiration) of a foreign object (see table Some Causes and Features of Wheezing Some Causes and Features of Wheezing ).
Evaluation 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:
Labored breathing, weakening efforts to breathe, or a decreased level of consciousness
Swelling of the face and tongue
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 table Some Causes and Features of Wheezing 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 Shortness of Breath Shortness of breath—what doctors call dyspnea—is the unpleasant sensation of having difficulty breathing. People experience and describe shortness of breath differently depending on the cause... read more , fever, cough Cough in Adults Cough is a sudden, forceful expulsion of air from the lungs. It is one of the most common reasons people see a doctor. The function of a cough is to clear material from the airways and to protect... read more , 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.
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 Arterial Blood Gas (ABG) Analysis and Pulse Oximetry Both arterial blood gas testing and pulse oximetry measure the amount of oxygen in the blood, which helps determine how well the lungs are functioning. Arterial blood gas tests are invasive... read more )
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 Pulmonary Function Testing (PFT) Pulmonary function tests measure the lungs' capacity to hold air, to move air in and out, and to absorb oxygen. Pulmonary function tests are better at detecting the general type and severity... read more 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 Bronchoscopy Bronchoscopy is a direct visual examination of the voice box (larynx) and airways through a viewing tube (a bronchoscope). A bronchoscope has a camera at the end that allows a doctor to look... read more ) into the airway to identify the problem and, if it is an object, remove it.
Treatment of Wheezing
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, leukotriene modifiers, or immunomodulators (drugs that affect the immune system—see table Drugs Commonly Used to Treat Asthma Drugs Commonly Used to Treat Asthma ).
Antihistamines (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.
Asthma is the most common cause, but not all wheezing is caused by asthma.
Wheezing that starts suddenly in people without a lung disorder may be due to inhalation of a foreign object or a toxic substance, an allergic reaction, or heart failure.
Pulmonary function tests can identify and measure airway narrowing.
Inhaled bronchodilators can help relieve wheezing, but the disorder causing wheezing must also be treated.