Pulmonary Function Tests - When To Opt It?

Pulmonary Function Tests or PFTs are a set of tests that are used to determine, measure or observe the functioning of the lungs. The most common pulmonary function tests used are spirometry, gas diffusion, and lung plethysmography.

Highlights of pulmonary function tests

1. A spirometry test is used to measure the amount of air inhaled and exhaled. It also measures the amount of time taken to complete a respiration cycle.
2. Lung plethysmography measures the amount of air in the lungs after the patient has taken a deep breath. It also measures the amount of air that remains in the lungs after the patient has exhaled as much air as possible.

What does a Pulmonary Function Test measure?
Pulmonary function tests would not only check how well the person is breathing but also how effectively the lungs are able to conduct oxygen to the rest of the body. In addition to airflow, these tests would measure the size and volume of the lung and lung diffusion.

These tests can also be used to measure

1. Total Lung Capacity – the amount of air present in the lungs after breathing in deeply
2. Forced Vital Capacity – the amount of air that can be exhaled after breathing in deeply
3. Minute Volume – the amount of air exhaled per minute
4. Vital Capacity – the total volume of air that can be breathed out after inhaling as much as possible
5. Tidal Volume – the amount of air inhaled or exhaled when breathing normally
6. Maximum voluntary ventilation – the amount of air that can be inhaled and exhaled in one minute
7. Functional Residual Capacity – the amount of air that remains in the lungs when breathing normally
8. Forced Expiratory Flow – the flow or volume of air during exhalation. Forced expiratory flow 25-75 is early marker of small airway impairment.
9. Peak Expiratory Flow Rate –  PEFR is the maximum flow rate generated during a forceful exhalation after a full inspiration.

When are Pulmonary Function Tests recommended?
A physician might recommend a patient undergo a PFT as part of a routine physical check-up. This test would be advised if the patient is experiencing any symptoms associated with lung problems or disorders such as asthma, respiratory infections, chronic obstructive pulmonary disease, COPD. A doctor would also use these tests to monitor and check whether a certain treatment prescribed for lung disease or condition is working effectively.

Pulmonary function tests are safe as they are non-invasive but it is important to follow the instructions of the doctor or technician before, after and during the test. It is important to make your doctor aware of any surgeries, respiratory infections, chest pains or heart attacks that you might have experienced before the test. If you are taking any medications you might need to follow the advice of the doctor as to whether you can take them before the test.

Your doctor would also advise you on how to prepare for the test such as not eating a large meal, avoiding caffeine and wearing loose-fitting clothes. If you have any doubts, concerns or queries discuss them with your doctor.