Pulmonary Function Tester (PFT) machine also known as a "Spirometer" is a device used to measure changes in air volume and can only measure lung volume compartments that exchange gas with the atmosphere. Spirometers with electronic signal outputs (pneumotachs) also measure flow (volume per unit of time). A PFT device is usually always attached to the spirometer which measures the movement of gas in and out of the chest and is referred to as a spirograph. Sometimes the spirograph is replaced by a printer like the unit used in this laboratory. The resulting tracing is called a spirogram. Many computerized systems have complex spirographs or printouts that show the predicted values next to the observed values (the values actually measured). The unit will have in memory all of the prediction t