Pulmonary Function Testing is a painless procedure that usually takes about 30-45 minutes or less.   You will be asked to breathe into a computerized machine that measures how fast you can breathe in and out and how big your lungs are.  As part of the procedure you may be given some inhaled medication to test your response to this form of treatment.  No special preparation is required, but you should not use any inhaled medication on the day of the test, if possible, and refrain from smoking.