Pulmonary function tests (PFTs) are a series of different breathing tests led by a trained pulmonary function technologist, usually done at a hospital or clinic. There are national standards and guidelines that help make sure that everyone does and interprets pulmonary function tests in the same way. To learn about your lung health, your doctor may want you to have several pulmonary function tests done including spirometry, lung volumes, diffusing capacity, and airway resistance. Most of these breathing tests are done by blowing into a tube while sitting in a chair.
A doctor will look over the results of your PFTs and see how you are doing by comparing them to predicted values normal for a person your age, height, sex and ethnicity. Height is important because taller people may have bigger lungs. There are many things that can change the results in PFTs. A medical diagnosis is not likely to be made from PFTs alone.