Why is it done?

These tests are used to evaluate lung mechanics, gas exchange, pulmonary blood flow, and blood gases and pH. They are useful to evaluate patients in the diagnosis of pulmonary disease, assessment of disease development, or evaluation of the risk of pulmonary complications from surgery. PFT is quite often advised for patients suspected to have diseases like asthma, emphysema or other conditions with low reserves. They are also very useful to monitor the progress or improvement of the disease process that affects lungs and response to certain medications. They however do not assess infection tumors or birth defects of lungs.