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What the spirometry?

Spirometry is a common test used to assess how well your lungs are working by measuring how much air you breathe in, how much you breathe out, and how quickly you breathe out.

Spirometry is used to diagnose asthma, chronic obstructive pulmonary disease (COPD), and other diseases that affect breathing. Spirometry can also be used periodically to monitor the condition of your lungs and see if treating chronic lung disease is helping you breathe better.

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Why is it done?

Your treating doctor may suggest a spirometry test if they suspect that your signs or symptoms may be due to chronic lung disease, such as:

  • Asthma

  • Chronic obstructive pulmonary disease (COPD)

  • chronic bronchitis

  • Emphysema

  • Pulmonary fibrosis

If you've already been diagnosed with a chronic lung disorder, spirometry may be used periodically to check how well your medications are working and whether your breathing problems are under control. You may be ordered to have a spirometry test before you have elective surgery to check if your lung function is adequate to withstand the rigors of an operation. In addition, spirometry can be used to detect work-related lung disorders.



Spirometry is generally a safe test. You may feel short of breath or dizzy for a few moments after taking the test.

Because the test requires physical exertion, it can't be done if you've had a recent heart attack or other heart disease. Rarely, the test triggers serious breathing problems.

How to prepare

Follow your doctor's instructions to see if you should avoid using inhaled medications or other medications before the test. Other preparations include the following:

  • Wear loose clothing that does not interfere with your ability to breathe deeply.

  • Avoid eating a large meal before the test to make it easier for you to breathe.

what you can expect

A spirometry requires you to breathe into a tube connected to a machine called a spirometer. Before you take the test, a nurse, technician, or doctor will give you specific instructions. Pay attention and ask questions if something is not clear to you. You need to perform the test correctly to get accurate and meaningful results.

In general, you can expect the following during a spirometry:

  • You will probably be seated during the test.

  • A clip will be placed on your nose to keep your nostrils closed.

  • You will take a deep breath and exhale as hard as you can for several seconds into the tube. It is important that your lips form a seal around the tube so that no air escapes.

  • You'll need to take the test at least three times to make sure the results are relatively consistent. If there is too much difference between the three results, you may need to repeat the test. The highest value among the three similar test results will be used as the final result.

  • The entire process usually takes less than 15 minutes.

Your doctor may give you an inhaled medication to open up your lungs (bronchodilator) after the initial round of tests. You will have to wait 15 minutes and then do another set of measurements. The doctor can then compare the results of the two measurements to see if the bronchodilator improved airflow.


Key spirometry measurements include the following:

  • forced vital capacity.  This is the maximum amount of air you can forcefully exhale after inhaling as deeply as you can. A reading below normal forced vital capacity indicates restricted breathing.

  • Forced respiratory volume.  This indicates how much air you can force out of your lungs in one second. This reading helps your doctor assess the severity of your breathing problems. Lower forced expiratory volume readings indicate a more significant obstruction.

Source: Mayo Clinic

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