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What is Spirometry Test, Its Uses and How is it Done?

What is Spirometry?

Pulmonary function tests are done to assess the function of the lungs(4). Spirometry is a form of pulmonary function test, which measures the amount of air an individual exhales or breathes out and at what speed(3). Spirometry is a common and simple test that can be done on an outpatient basis(1, 3). A spirometry test can be done for diagnosis of asthma, cystic fibrosis and COPD.

The Uses of a Spirometry Test

The Uses of a Spirometry Test

Spirometry test is used by the physician to monitor the patient’s progress when treating a chronic lung disease. A Spirometry test helps in determining the effect of the medications and how they are managing and controlling the lung disease.

A Spirometry test is done for diagnosing various lung diseases, such as:

Chronic Obstructive Pulmonary Disease (COPD)(1): This is a class of lung conditions where there is narrowing of the airways that leads to difficulty in expelling the air from the lungs.

Asthma(1): Asthma is a chronic inflammatory condition where there is narrowing and swelling of the airways.

Cystic Fibrosis(1): This is a hereditary disease where the digestive organs along with the lungs become blocked or congested with sticky and dense mucus.

Pulmonary Fibrosis(1): Pulmonary Fibrosis is a medical condition consisting of accumulation of scar tissue in the lungs’ air sacs resulting in poor oxygenation of the blood(2).

What is the Procedure of a Spirometry Test?

A spirometry test is quite common and is a simple diagnostic test where the patient needs to breathe into a tube that is attached to the spirometer, which will be recording the results.

The patient will be asked whether they are taking any breathing medications, such as bronchodilators. Bronchodilators are the medicines that widen and relax the airways, thus making breathing easier for the patient. If the patient is taking these medicines, then the doctor advises the patient to stop these medicines before the spirometry test to assess the effectiveness of these medicines.

Before doing the Spirometry test, the patient may also be recommended to wear loose clothing and avoid consuming a heavy meal before a Spirometry test to help with the breathing.

Before Undergoing A Spirometry Test The Patient Is Required To Do The Following(1):

  • Avoid smoking at least 24 hours before the Spirometry test.
  • Avoid consuming alcohol before the Spirometry test.
  • Patient should also not do any rigorous or strenuous exercise before the Spirometry test.

The Steps Taken During The Spirometry Test Are(1):

  • The doctor places a clip on the patient’s nose to close the nostrils. The patient is told to inhale or breathe in as much air as possible to fill the lungs.
  • The patient then encloses the tube opening with their mouth and breathes out into the tube as forcefully and as quickly they can for many seconds.
  • The Spirometry test is often repeated minimum three times to ensure the result is accurate and consistent. The highest value among the three Spirometry test is usually taken as the final result.
  • The patient can also be given a bronchodilator via inhalation and then perform the Spirometry test again to assess the effect of the bronchodilator on the patient’s capacity to breathe.
  • A lung specialist or a pulmonologist need to see the results to give the right interpretation of the results.

What Do The Results of the Spirometry Test Indicate?(1, 5)

The results of the spirometry test helps in determining the treatment plan for the patient. The Spirometry test helps in assessing the airflow over a period of time. The results of the Spirometry test gives two values, which are useful for monitoring and assessing patients having an impaired lung function. These 2 values from a Spirometry test are:

Forced Vital Capacity (FVC), which is the total quantity of air which can be expelled or exhaled completely.

Forced Expiratory Volume measured over 1 second (FEV1) is the air flow occurring in the first second of the Forced Vital Capacity. The FVC divides the FEV1 to find the amount of air in the patient’s lungs, which can be exhaled in a single second.

If the FVC reading is low, then it indicates that the patient is suffering from restricted breathing. The FEV1 test result helps in gauging severity of the patient’s breathing problem. Decreased FEV1 readings indicate severe breathing obstruction.

All the results of these tests help the doctor in determining what steps to take in the patient’s treatment. The normal value of the spirometry test differs from patient to patient. The average result of Spirometry test is determined by different factors, such as patient’s age, sex, height and race.

Obstructive or Restrictive Lung Disease(4)

If the patient is suffering from an obstructive lung disease, then there is narrowing of the airways that affects the patient’s ability to exhale quickly during the Spirometry test; however, the patient is still able to hold a normal quantity of air in their lungs. Patients suffering from COPD and asthma will experience this.

If the patient is suffering from restrictive lung disease, then the patient’s air intake will be reduced because the lungs will not be able to expand completely when a person is suffering from restrictive lung disease.

The changes in FVC/FEV1 results after the patient is given a bronchodilator will determine if the disease of the patient can be reversed or not. If there is an increase of about 12% in the test’s results, then this indicates the effectiveness of the bronchodilator in reversing the disease; e.g. asthma. There are some symptoms in certain lung disease, such as COPD that cannot be reversed.

If patient is found to have restrictive pattern of lung disease, then a complete range of pulmonary function tests need to be done to confirm that the patient is indeed suffering from restrictive lung disease and the type the patient is suffering from.

Other Tests to Assess the Lung Function

Other than the Spirometry test, there are different tests that can also be done to arrive at the correct diagnosis and these include: lung volume tests; pulse oximetry test; arterial blood gas tests; fractional exhaled nitric oxide tests; CT scan and x-ray of the chest.


Sheetal DeCaria, M.D.
Sheetal DeCaria, M.D.
Written, Edited or Reviewed By: Sheetal DeCaria, M.D. This article does not provide medical advice. See disclaimer
Last Modified On:August 2, 2021

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