A spirometer is a device used for measuring lung function. This test evaluates the amount of air that you can inhale and exhale, and the speed at which you can exhale the air out of your lungs. It is performed to diagnose chronic lung conditions.


Spirometry is indicated for conditions such as chronic obstructive pulmonary disease or COPD (damaged lungs), asthma (inflammation of airways), pulmonary fibrosis (excessive development of fibrous tissue in the lungs) and chronic bronchitis (inflammation of the air sacs in the lungs). Spirometry also helps in periodic monitoring of lung function during ongoing treatment for lung disorders.


Steps involved in performing the procedure include:

  • Your doctor will place a clip over your nose to seal the nasal airway.
  • You will be asked to take a deep breath, seal the spirometer’s mouth piece with your mouth, and breathe out fast and forcefully into a tube attached to the spirometer. This may take several seconds until your lungs are fully empty.
  • You may have to repeat the test; this time, exhaling slowly until you get all the air out.
  • You may have to take the test at least 3 times for consistent results.
  • In order to compare results, your doctor may repeat the test by first asking you to inhale a bronchodilator (medication to open up your lungs) to check if it improves your air flow.


Spirometry measures the Forced Vital Capacity (FVC) and the Forced Expiratory Volume (FEV-1) to determine lung function.

  • FVC is the measurement of the amount of air forcefully exhaled after breathing deeply. Lowered FVC value indicates restricted breathing. Pulmonary fibrosis and physical deformities can be diagnosed with a restrictive pattern on spirometry.
  • FEV-1 is the measurement of the amount of air that can be forced out of your lungs in a second. Lowered FEV-1 value indicates severe obstruction during breathing. Asthma and COPD can be diagnosed by an obstructive pattern on the spirometry.