Pulmonary function tests are a group of test that measure how well the lungs take in and release air and how well they move oxygen into the blood.(it is a non invasive)
In a spirometry test, you breathe into a mouthpiece that is connected to an instrument called a spirometer. The spirometer records the amount and the rate of air that you breathe in and out over a period of time.
Lung volume measurement can be done in two ways:
-The most accurate way is to sit in a sealed, clear box that looks like a telephone booth (body plethysmograph) while breathing in and out into a mouthpiece. Changes in pressure inside the box help determine the lung volume.