Wheezing is a whistling sound that occurs during breathing when the airways are partially blocked.

Causes

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).

Common causes: Overall, the most common causes are

• Asthma
• COPD

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 Symptoms of Lung Disorders: Some Causes and Features of Wheezing).

Evaluation

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.

Warning signs: 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 Symptoms of Lung Disorders: 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 smokers may be due to lung cancer. Doctors also examine the heart, nose and throat, limbs, hands, feet, and skin.

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Some Causes and Features of Wheezing Cause Common Features* Tests† Acute bronchitis Cough Sometimes symptoms of an upper respiratory infection (such as a stuffy nose) Usually no known history of a lung disorder A doctor's examination Allergic reactions Wheezing that starts suddenly, usually within 30 minutes of exposure to a known or potential allergen such as pollen Often a stuffy nose, hives, itchy eyes, and sneezing A doctor's examination Asthma Usually a history of asthma Wheezing that starts spontaneously or after exposure to specific stimuli (such as pollen or another allergen, an upper respiratory infection, cold, or exercise) A doctor's examination Sometimes one or more of the following tests: Tests to evaluate how well the lungs are functioning (pulmonary function tests) Measurement of peak air flow (how fast air can be exhaled) Measurement of lung function before and after exercise or administration of methacholine (a drug that narrows airways) Sometimes use of bronchodilators (drugs that widen airways) to see whether symptoms go away Bronchiolitis (infection of the lower respiratory tract) In children under 18 months old Usually occurring from November to April in the Northern Hemisphere Usually symptoms of an upper respiratory infection (such as a stuffy nose and fever) and rapid breathing A doctor's examination A chronic obstructive pulmonary disease (COPD) flare-up In middle-aged or older people In people who already have COPD Usually a history of extensive smoking Labored breathing A chest x-ray Pulmonary function tests Drugs (such as ACE inhibitors, beta-blockers, aspirinSome Trade Names BAYER , and other NSAIDs) In people who have recently started using a new drug, most often in those with a history of airway obstruction (as occurs in asthma) A doctor's examination Lung tumors Wheezing while inhaling and exhaling, especially in people with risk factors for or signs of cancer (such as a history of smoking, night sweats, weight loss, and coughing up blood) A chest x-ray or CT of the chest Bronchoscopy A foreign object that has been inhaled High-pitched wheezing or cough that starts suddenly in people (typically infants or young children) without any symptoms of an upper respiratory infection, fever, or other symptoms of illness A chest x-ray or CT of the chest Bronchoscopy GERD with repeated reflux of stomach contents into the lungs (chronic aspiration) Chronic or recurring wheezing Often burning pain in the chest (heartburn) or abdomen that tends to worsen after eating certain foods, while exercising, or while lying flat A sour taste, particularly after awakening Hoarseness A cough that occurs in the middle of the night or early morning No symptoms of an upper respiratory infection or allergy Sometimes only a doctor's examination Sometimes use of drugs that suppress acid, such as a histamine-2 (H2) blocker or proton pump inhibitor, to see whether symptoms go away Sometimes insertion of a flexible viewing tube into the esophagus and stomach (endoscopy) Sometimes placement a sensor in the esophagus to monitor acidity (pH) for 24 hours Heart failure Usually swelling (edema) of the legs Shortness of breath that worsens while lying flat or that appears 1–2 hours after falling asleep Sounds suggesting fluid in the lungs, heard through a stethoscope A chest x-ray Sometimes a blood test to measure a substance that is produced when the heart is strained called brain natriuretic peptide (BNP) Sometimes echocardiography Irritants that are inhaled Wheezing that starts suddenly after exposure to irritants at work (occupational exposure) or inappropriate use of cleaning products A doctor's examination *Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present. †Doctors usually measure the oxygen level in blood with a sensor placed on a finger (pulse oximetry). A chest x-ray is usually taken unless the person's symptoms are clearly a flare-up of an already diagnosed chronic disorder. ACE = angiotensin-converting enzyme; COPD = chronic obstructive pulmonary disease; CT = computed tomography; GERD = gastroesophageal reflux disease; NSAIDs = nonsteroidal anti-inflammatory drugs. Some Causes and Features of Wheezing Cause Common Features* Tests† Acute bronchitis Cough Sometimes symptoms of an upper respiratory infection (such as a stuffy nose) Usually no known history of a lung disorder A doctor's examination Allergic reactions Wheezing that starts suddenly, usually within 30 minutes of exposure to a known or potential allergen such as pollen Often a stuffy nose, hives, itchy eyes, and sneezing A doctor's examination Asthma Usually a history of asthma Wheezing that starts spontaneously or after exposure to specific stimuli (such as pollen or another allergen, an upper respiratory infection, cold, or exercise) A doctor's examination Sometimes one or more of the following tests: Tests to evaluate how well the lungs are functioning (pulmonary function tests) Measurement of peak air flow (how fast air can be exhaled) Measurement of lung function before and after exercise or administration of methacholine (a drug that narrows airways) Sometimes use of bronchodilators (drugs that widen airways) to see whether symptoms go away Bronchiolitis (infection of the lower respiratory tract) In children under 18 months old Usually occurring from November to April in the Northern Hemisphere Usually symptoms of an upper respiratory infection (such as a stuffy nose and fever) and rapid breathing A doctor's examination A chronic obstructive pulmonary disease (COPD) flare-up In middle-aged or older people In people who already have COPD Usually a history of extensive smoking Labored breathing A chest x-ray Pulmonary function tests Drugs (such as ACE inhibitors, beta-blockers, aspirinSome Trade Names BAYER , and other NSAIDs) In people who have recently started using a new drug, most often in those with a history of airway obstruction (as occurs in asthma) A doctor's examination Lung tumors Wheezing while inhaling and exhaling, especially in people with risk factors for or signs of cancer (such as a history of smoking, night sweats, weight loss, and coughing up blood) A chest x-ray or CT of the chest Bronchoscopy A foreign object that has been inhaled High-pitched wheezing or cough that starts suddenly in people (typically infants or young children) without any symptoms of an upper respiratory infection, fever, or other symptoms of illness A chest x-ray or CT of the chest Bronchoscopy GERD with repeated reflux of stomach contents into the lungs (chronic aspiration) Chronic or recurring wheezing Often burning pain in the chest (heartburn) or abdomen that tends to worsen after eating certain foods, while exercising, or while lying flat A sour taste, particularly after awakening Hoarseness A cough that occurs in the middle of the night or early morning No symptoms of an upper respiratory infection or allergy Sometimes only a doctor's examination Sometimes use of drugs that suppress acid, such as a histamine-2 (H2) blocker or proton pump inhibitor, to see whether symptoms go away Sometimes insertion of a flexible viewing tube into the esophagus and stomach (endoscopy) Sometimes placement a sensor in the esophagus to monitor acidity (pH) for 24 hours Heart failure Usually swelling (edema) of the legs Shortness of breath that worsens while lying flat or that appears 1–2 hours after falling asleep Sounds suggesting fluid in the lungs, heard through a stethoscope A chest x-ray Sometimes a blood test to measure a substance that is produced when the heart is strained called brain natriuretic peptide (BNP) Sometimes echocardiography Irritants that are inhaled Wheezing that starts suddenly after exposure to irritants at work (occupational exposure) or inappropriate use of cleaning products A doctor's examination *Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present. †Doctors usually measure the oxygen level in blood with a sensor placed on a finger (pulse oximetry). A chest x-ray is usually taken unless the person's symptoms are clearly a flare-up of an already diagnosed chronic disorder. ACE = angiotensin-converting enzyme; COPD = chronic obstructive pulmonary disease; CT = computed tomography; GERD = gastroesophageal reflux disease; NSAIDs = nonsteroidal anti-inflammatory drugs.

Testing: 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 (see Diagnosis of Lung Disorders: 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.

Treatment

The main goal of treatment is to treat the underlying disorder.

Bronchodilators (which widen the airways), such as inhaled albuterolSome Trade Names
PROVENTIL-HFA VENTOLIN HFA
, 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 Asthma: Drugs for Preventing or Treating Attacks).

Histamine-2 (H₂) blockers (such as diphenhydramineSome Trade Names
BENADRYL
) given intravenously, corticosteroids (such as methylprednisoloneSome Trade Names
MEDROL
), albuterolSome Trade Names
PROVENTIL-HFA VENTOLIN HFA
taken through a nebulizer, and epinephrine injected under the skin (subcutaneously) are given to people with anaphylaxis.

Key Points

• 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.

Last full review/revision July 2012 by Noah Lechtzin, MD, MHS