Your Complete Guide to Pulmonary Function Tests


The term Pulmonary Function Tests (PFTs) must sound familiar and some of you must also have gone through them at some point in your life. If you have already done these tests you must be pretty aware of the procedure as well as the risks, but for those who have doubts and want to educate yourselves more about them, here is your complete guide for Pulmonary Function Tests (PFTs), their risks and benefits.

What are Pulmonary Function Tests?

Pulmonary function Tests (PFTs) are noninvasive tests performed by doctors in patients with chronic lung diseases and sometimes in healthy people to check lung function and capacity. PFTs can measure lung capacity, rate of airflow, lung volume and gas exchange. A few conditions in which doctors use Pulmonary Function tests are Chronic obstructive pulmonary disorder (COPD), emphysema, pulmonary fibrosis, asthma, etc. These tests are also used in healthy individuals to determine their lung health and function

Types of Pulmonary Function Tests and Procedure:

There are two different methods in which pulmonary function tests are performed — Spirometry and Plethysmography. Knowing about these methods in detail will also help us understand the procedure of PFTs.


  • This test is one of the most commonly performed Pulmonary function tests and uses a device called a spirometer.
  • Spirometry test measures the amount of airflow that goes in and out of your lungs when you breathe in and breathe out.
  • This test is mainly useful for the diagnosis of conditions like COPD and asthma.
  • During this test you are asked to breathe in as much air as possible and then quickly breathe out the inhaled air.
  • Spirometry measures two important things— Forced vital capacity (FVC) i.e the most air you can breathe out after inhaling and Forced expiratory volume in one second (FEV1) i.e. the amount of air exhaled in one second.


  • Plethysmography or body plethysmography test takes place with you sitting or standing in a square box like a phone booth with a nose clip. This test requires you to breathe through your mouth into a specially designed mouthpiece.
  • This test measures the amount of air in your lungs after inhalation i.e Total lung capacity (TLC) and the amount of air that remains in your lungs after exhalation i.e. Residual Volume (RV).
  • Similar to spirometry, plethysmography also helps to diagnose conditions like COPD, asthma and emphysema. In addition to that it also helps the doctor to decide on the type of medications that might help you.

Other than these two most commonly used methods there are a few other tests performed as well. They are — bronchial provocation test, exercise tolerance tests, Pulse oximetry test, arterial blood gas test.

  1. Bronchial provocation test: This test helps in the diagnosis of asthma. In this test you inhale medicine that narrows your airways followed by a spirometry test.
  2. Exercise tolerance test: This test helps to measure and determine your cardiopulmonary health. This test is usually performed on a treadmill while your heart rate is monitored.
  3. Pulse oximetry test: This test is performed using an oximeter which helps to measure the level of oxygen in your blood.
  4. Arterial blood gas test: This test is used to measure the levels of oxygen and carbon dioxide in the blood that flows through your arteries.

Preparation for PFTs

Your doctor will usually guide you on all the measures you need to follow before the procedure and also guide you throughout the procedure. You will be asked to sign a consent form, make sure to read it carefully and clear all your doubts before signing.A few points you should keep in mind while preparing for PFTs are:

  • Follow the instructions given by your doctor and healthcare professional carefully.
  • If you have habits of drinking or smoking, talk to your doctor about the possible risk and how long before the test you are not supposed to indulge in such habits.
  • If you are taking any medications, inform your healthcare professional and stop taking them if advised.
  • Make sure you follow the instructions about your meals and if advised avoid heavy meals before the test.

Some common risks of PFTs are:

  • Dizziness
  • Coughing
  • Shortness of breath
  • Asthma attack

In certain cases performing PFTs should be avoided:

  • Recent right eye surgery
  • Recent heart surgery or a recent heart attack
  • Chest pain
  • Active tuberculosis

This guide is to help you understand pulmonary function tests better but the bottom line is to follow your healthcare professional’s instructions and clear all your doubts before going for the procedures. Remember these procedures are to help you and for the better diagnosis of your conditions. If you are still skeptical, talk to your doctor about the possible risks and benefits.