Pulmonary Function Test (PFT) System machines perform body plethysmography, a noninvasive type of lung function testing known as a pulmonary function test, which can determine how much air is in lungs... Pulmonary Function Test (PFT) System machines perform body plethysmography, a noninvasive type of lung function testing known as a pulmonary function test, which can determine how much air is in lungs after inhalation and how much air is in lungs exhalation. The system also includes accessories, software, installation and training for clinical users.