Spirometry is the measurement of an individual’s ability to inhale and exhale. A spirometry test is a simple and short examination. During the test, a patient inhales and exhales through a mouthpiece into a device called a spirometer, which records the patient’s breathing capabilities.

The spirometry test is one of three pulmonary function tests. The spirometer is used to assess different values involving respiration. These include:

• Speed at which an individual can exhale
• Amount of air the lungs can hold (lung capacity)

A physician can use the data obtained during the test to evaluate the patient’s breathing ability and diagnose certain conditions (e.g., asthma, lung disease). The test can also gauge the progression of respiratory diseases and help determine effective forms of treatment. Spirometry is a useful diagnostic tool for patients 5 years of age and older.

Spirometry measures lung function by testing the patient’s ability to inhale and exhale. The test is the most common of the three pulmonary function tests used to assess the health of the patient’s lungs and airways. Spirometry tests are usually carried out in children over 5 years of age, because of the testing requirements involved, but can be done on cooperative younger children. Although there is a lack of “normal” testing values for younger children, physicians can still obtain important information from the test. The ability to complete spirometry tests is often dependent on the individual.

The spirometry test uses a device called a spirometer to evaluate three pulmonary functions. The spirometer uses the data acquired during the test to fill in certain values. These values include:

• Maximum volume ventilation (MVV). Measures the complete volume an individual exhales in a 15-second period. This number is multiplied by four to find the value for one minute.
  
  
• Forced vital capacity (FVC). Measures the volume of air exhaled over a continuous six-second period. This helps provide an indication of how much air the lungs can hold.
  
  
• Forced expiratory capacity (FEV1). Measures the speed of air exhaled in one second.

The recordings of the information obtained from the test are known as spirograms. The information provides a good evaluation of the health of an individual’s respiratory system. Spirometry is also useful for the diagnosis of several types of respiratory conditions. These include:

• Reactive airway diseases (e.g., asthma)

• Chronic obstructive pulmonary disease (COPD, including chronic bronchitis and emphysema)
  
  
• Respiratory diseases (e.g., cystic fibrosis)
  
  
• Abnormal blood flow to the lungs (e.g., pulmonary hypertension)

Besides diagnosis, spirometry is useful for comparing the progression of respiratory conditions. Many types of conditions (e.g., asthma, COPD) are characterized by steadily deteriorating lung function. Spirometry can be used to gauge how quickly and severely a patient’s airways are becoming obstructed. Spirometry measurements repeated over several years can determine the development and extent of airway obstruction.

Spirometry can also be used to determine the effectiveness of therapy. A patient who achieves better spirometry numbers after using a bronchodilator, for instance, has a respiratory condition that is responsive to drug treatments. Conversely, the failure of a patient to respond to bronchodilators may suggest permanent respiratory damage. In addition, a physician may use spirometry to monitor the effectiveness of therapy. For instance, a physician may increase or decrease a patient’s medication dosage after reviewing their spirometry results. Spirometry also can be used to evaluate the risk of operations for a patient.

For several hours prior to the spirometry test, a patient should refrain from exercise, eating a heavy meal and smoking. These can interfere with respiration during testing. A patient’s physician may also have specific instructions on the use of bronchodilators or inhaler medications prior to the test. Patients should always check with their physician before suspending the use of any medications.

Wearing loose-fitting clothes to the test is a good idea, as it allows the patient to breathe without restriction. Patients who wear dentures should keep them in for the test, as the dentures will make it easier for the patient to create a tight seal on the mouthpiece of the spirometer.

If the patient being tested is a child, parents are encouraged to review the testing procedure with them in advance so they are not overly frightened by the testing itself.

Spirometry testing is quick, painless and noninvasive. The test is usually performed on a simple spirometer machine located at a physician’s office, hospital or clinic. Though some spirometers are small enough to be portable, the devices are not capable of producing highly accurate results.

The test is usually administered by a physician or qualified technician. The test procedure is as follows:

1. Patients place the mouthpiece of the spirometer in their mouth, while standing or sitting up as straight as possible. If they are unable to create a tight seal around the mouthpiece, patients should notify the person conducting the test of the problem. This is important because a poor seal can lead to poor results that do not permit interpretation.
   
   
2. Nose clips are applied to the patient, preventing them from breathing through their nose.
   
   
3. The physician or technician may have patients go through several breathing exercises or tests, which will be explained to patients during the procedure.
   
   
4. Patients are instructed to inhale as much air into the lungs as possible, then exhale that air as fast and for as long as possible.
   
   
5. Patients remove the mouthpiece and breathe normally.

Some physicians will perform the test once under normal circumstances, and then administer a bronchodilator to the patient before repeating the test. This allows the physician to see whether the patient’s breathing can be improved with the use of bronchodilators. Some doctors will perform the test several times in a short period of time in order to achieve more accurate results.

Because the test involves heavy breathing it can make some patients temporarily short of breath. Patients should inform the person conducting the test if breathing difficulties persist or if they begin to feel dizzy. Testing will cease and treatment to resolve symptoms will immediately be given.

A physician or healthcare provider will often explain the spirometry test results to patients immediately after the test is complete. In some cases, a follow-up conversation or office visit may be scheduled to go over the results.

Although spirometry results can identify restrictive or obstructive disease patterns, the results are not disease specific. As a result, a physician may need to perform additional tests (e.g., chest x-ray) to determine whether asthma, emphysema or another disease is causing the abnormality.  

It is also important to note that while spirometry can detect obstructive diseases in their early stages, it is not always sensitive enough to detect restrictive diseases (e.g., silicosis, pneumonoconiosis) before extensive and irreversible damage has occurred.

A spirometry test is generally considered a safe and simple test; however, it can offer increased risks to some patients. People with certain conditions should make sure their physician is aware of the condition before testing begins. These include:

• Asthma. Condition in which the airways become blocked or narrowed, causing shortness of breath and difficulty breathing. The prolonged heavy breathing that is sometimes required during a spirometry test can induce an asthma attack in individuals with severe asthma.
  
  
• Other lung diseases (e.g., COPD, cystic fibrosis). Some diseases of the lungs can cause the lungs to weaken, increasing the risk of a collapsed lung occurring during a spirometry test.
  
  
• Recent heart attack or heart disease. Impaired heart function as the result of a recent heart attack or heart disease can become exacerbated during a spirometry test.

If a spirometry test finds that a patient’s lung function is lower than the values that are considered normal for the patient’s age, height, ethnicity and sex, it may indicate the presence of chest or lung disease (e.g., asthma). Further testing may be recommended by the physician to confirm or rule out certain conditions. For example, to diagnose asthma a physician might suggest one or more of the following tests:

• Chest x-ray. Allows the physician to see some types of airway or lung damage.
  
  
• Allergy tests (e.g., skin test, RAST). A susceptibility to allergies can cause complications for someone with even a mild asthma condition. Allergy tests can detect sensitivity to certain allergens.
  
  
• Exercise challenge test. Most appropriate for individuals with a history of exercise-induced symptoms. The test is capable of detecting decreased lung function caused by exercise.
  
  
• Bronchoprovocation test. This test involves a patient being exposed to irritating substances and subsequent measurement of their lung function. It is not frequently used and should be conducted only in controlled labs by experienced physicians or specially trained personnel.

If the presence of asthma or another lung disease is confirmed, the physician will recommend appropriate treatments or medications. Treatments commonly associated with the treatment of asthma include:

• Bronchodilators (e.g., beta-agonists, anticholinergics). Medications that relax constricted muscles in the airways, allowing the user to breathe and cough up mucus more easily.
  
  
• Mast cell stabilizers (e.g., cromolyn, nedocromil). Medications that reduce inflammation in the airways, making it easier to breath and lowering the chance of a severe asthma attack.
  
  
• Corticosteroids. Medications that reduce the swelling in nasal passages during an asthmatic reaction, reducing or avoiding asthma symptoms. Though effective, these drugs can have many side effects.
  
  
• Leukotriene modifiers. Medications that prevent inflammation in the airways, halting the process that often leads to an asthma attack.

A new test to evaluate lung function has been approved by the U.S. Food and Drug Administration. The nitric oxide diagnostic test can successfully measure the amount of nitric oxide in the lungs. Patients with asthma and/or chronic bronchitis have increased levels of nitric oxide, although patients with COPD do not. This test can also indicate whether current asthma treatment is successful in a patient.  

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions regarding spirometry:

1. Will I need to go to a hospital for the test? Can I take the test at home?
   
   
2. Can you explain the testing procedure to me in detail?
   
   
3. How long will the test take?
   
   
4. Will I experience any pain or discomfort during the test?
   
   
5. Are there special preparations I need to make prior to the test?
   
   
6. Can I drive myself to and from the test?
   
   
7. When will my results be available? Who will explain them to me?
   
   
8. Are there any risks associated with the test?
   
   
9. What will happen if I have trouble breathing during the test?
   
   
10. How accurate is this test? Can I trust the results?
    
    
11. Will you be prescribing medication based on the results?
    
    
12. Do I require additional testing?