Spirometry

Spirometry is a commonly used lung test to evaluate the functioning of the lungs. Spirometry is done to measure the airflow in and out of the lungs, and it also measures the amount of air exhaled and how quickly the person can exhale the same amount of air. Spirometry is a test performed to measure the lung capacity along with its functioning. Spirometry is helpful in diagnosing some medical conditions like chronic pulmonary obstructive disorder (COPD), restrictive lung disease (e.g. interstitial pulmonary fibrosis), asthma and other problems that affect the breathing cycle. This test also assists the doctor to evaluate the response of treatment of chronic lung condition. Spirometry is an effective test that helps in identifying any blockages in the airways, which can be treated by giving medication to the patient to open the airways. These medications are also known as bronchodilator. After few minutes of administering the bronchodilator, the spirometry test is performed again to check if the bronchodilator has helped the patient or not in improving the symptoms or the disease condition. 

 


Why it's done Risks How you prepare What you can expect Results

Your doctor may suggest a spirometry test if he or she suspects your signs or symptoms may be caused by a chronic lung condition such as:

  • Asthma
  • 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.

Spirometry is generally a safe test. You may feel short of breath or dizzy for a moment after you perform the test.

Because the test requires some exertion, it isn't performed if you've had a recent heart attack or some other heart conditions. Rarely, the test triggers severe breathing problems.

Follow your doctor's instructions about whether you should avoid use of inhaled breathing medications or other medications before the test. Other preparations include the following:

  • Wear loose clothing that won't interfere with your ability to take a deep breath.
  • Avoid eating a large meal before your test, so it will be easier to breathe.

A spirometry test requires you to breathe into a tube attached to a machine called a spirometer. Before you do the test, a nurse, a technician or your doctor will give you specific instructions. Listen carefully and ask questions if something is not clear. Doing the test correctly is necessary for accurate and meaningful results.

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

  • You'll likely 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 breathe out as hard as you can for several seconds into the tube. It's important that your lips create a seal around the tube, so that no air leaks out.
  • You'll need to do the test at least three times to make sure your results are relatively consistent. If there is too much variation among the three outcomes, you may need to repeat the test again. The highest value among three close test results is used as the final result.
  • The entire process usually takes less than 15 minutes.

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

  • The report of the spirometry test is discussed with the patient in detail.
  • The normal values in the test report vary from one person to the other. This usually depends upon height, age, gender and race. The normal value of the test is calculated as by ATS-ERS guidelines 2005. The doctor then compares the patient's test values to the predicted normal value.
  • The spirometry test measures the 2 main factors- the expiratory forced vital capacity (FVC) and forced expiratory volume in one second (FEV1). These combined values are read by the doctor as FEV1/FVC ratio. If the patient has any blockage in the airways, then the ability to quickly exhale the air out of the lungs decreases. This is seen as a lowered FEV1 and FEV1/FVC ratio.
  • Forced vital capacity (FVC) – This refers to the amount of air exhaled by the patient after taking in a deep breath. A patient is diagnosed with restricted breathing if the value of the FVC is less than the normal value calculated by the doctor.
  • Forced expiratory volume in one second (FEV1) – This refers to the amount of air and capacity of the lungs to exhale the air out of the lungs with force, in one second. This value assists the doctor to determine the severity of the respiratory problems. If the test value of the patient is less than the normal value, then it indicates that the blockage or obstruction is quite severe.

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