What are pulmonary function tests?

Pulmonary function tests (PFTs) are non-invasive tests that show how well the lungs are working. The tests measure lung volume, capacity, rates of flow, and gas exchange. This information can help your healthcare provider diagnose and decide the treatment of certain lung disorders.

There are 2 types of disorders that cause problems with air moving in and out of the lungs:

• Obstructive. This is when air has trouble flowing out of the lungs due to resistance. This causes a decreased flow of air.

• Restrictive. This is when the chest muscles can’t expand enough. This creates problems with air flow.

PFT can be done with 2 methods:

• Spirometry. 

• A spirometer is a device with a mouthpiece hooked up to a small electronic machine.

• Spirometry is an essential pulmonary function tests. This examination is carried out using spirometer – a device that records the patient’s breathing. The result is a graph showing the volume of exhaled air with time. Examination is usually done because of breathlessness, longer cough, before thoracic surgery and to follow the effectiveness of lung diseases treatment. Basic examination can be done by general practitioner (family doctor),

Spirometry is the standard method for measuring most relative lung volumes; however, it is incapable of providing information about absolute volumes of air in the lung. Thus a different approach is required to measure residual volume, functional residual capacity, and total lungcapacity. Two of the most common methods of obtaining information about these volumes are gasdilution tests and body plethysmography

• Gasdilation & Plethysmography Tests.

•  You sit or stand inside an air-tight box that looks like a short, square telephone booth to do the tests.

PFT measures:

• Tidal volume (VT). This is the amount of air inhaled or exhaled during normal breathing.
• Minute volume (MV). This is the total amount of air exhaled per minute.
• Vital capacity (VC). This is the total volume of air that can be exhaled after inhaling as much as you can.
• Functional residual capacity (FRC). This is the amount of air left in lungs after exhaling normally.
• Residual volume. This is the amount of air left in the lungs after exhaling as much as you can.
• Total lung capacity. This is the total volume of the lungs when filled with as much air as possible.
• Forced vital capacity (FVC). This is the amount of air exhaled forcefully and quickly after inhaling as much as you can.
• Forced expiratory volume (FEV). This is the amount of air expired during the first, second, and third seconds of the FVC test.
• Forced expiratory flow (FEF). This is the average rate of flow during the middle half of the FVC test.
• Peak expiratory flow rate (PEFR). This is the fastest rate that you can force air out of your lungs.

Normal values for PFTs vary from person to person. The amount of air inhaled and exhaled recorded in your test are compared to the average for someone of the same age, height, sex, and race. Results are also compared to any of your previous test results. If you have abnormal PFT measurements or if your results have changes, you may need other tests.