The Pulmonary function test (PFT) measures the functioning of the lungs.

Why is a PFT performed?

Pulmonary function tests are done to:

  • Diagnose certain types of lung disease, such as asthma, bronchitis, and emphysema
  • Find the cause of shortness of breath whether it is obstructive or restrictive.
  • Measure whether exposure to chemicals at work affects lung function.
  • Check lung function before surgery.
  • Measure progress in disease treatment.
  • If already diagnosed with asthma or COPD spirometry, it can determine if the current treatment is effective.

What happens during a PFT?

You will be asked to blow (out & in) through a tight-fitted mouthpiece. The values will be recorded in the system.


Spirometry indicates the functioning of the lungs through the most common measurements that include:

  • Forced Vital Capacity (FVC) – The largest amount of air one can blow out after you take the biggest breath in.
  • Forced Expiratory Volume (FEV1) – The amount of air one can blow out of one’s lungs in the first second.
  • If the amount of air one can blow out in the first second is low then, lung disease such as asthma or COPD is suspected.

How to prepare for PFT

  • Don’t eat a heavy meal right before the test,
  • Avoid caffeinated foods or drinks.
  • Don’t smoke or exercise strenuously for six hours before the test.
  • On the day of the test, wear loose clothing that won’t restrict your breathing, and wear dentures to the testing if you normally wear them.