Lung function test is used to see how well your lung work by looking at how much air volume it can hold and how fast you can move air out of your lung. It is used to diagnose several types of lung diseases including asthma and COPD, and the severity of it so effective medication doses and strength could be used. It is also used to monitor how well the current treatment is so appropriate and timely treatment adjustment can be made. It takes only a few minutes to do the test. Sometimes, your physician may proceed to ask you do a second lung function test after giving you an albuterol or bronchodilatator inhaler to help diagnose and differentiate different types of lung diseases.