Pulmonary function tests are really — pulmonary is lung, and pulmonary function testing is breathing tests. What are they for? What they’re for is to tell us how much lung capacity a patient has. How are these tests done? You’ll be asked to go in a small room and a respiratory therapist will tell you to take deep breaths in and out, and they’ll tell you to take a big, big deep breath, and blow it all the way out — blow, blow, blow, and that tells us how much total air is in the lung and then they’ll do all kinds of calculations.
What you should know is about 40 years ago, they took 1,000 patients, your same height, weight, age, sex and race that never smoked cigarettes, that never complained of a lung problem like asthma or something else, and they did that same test, then they averaged those findings together to come up with what’s called a predicted or a reference value. The beauty of that is, that’s what normal is for someone just like you, and then when you do the test, they compare you to that normal reference value and come up with a percentage of the predicted value. Maybe you’re 80% or better, that’s considered normal; maybe you’re 60% of what a normal person is, maybe you’re 50%, 40%, etc. What that tells your doctors is a few things — one, can you tolerate taking out a piece of your lung for surgery? What we wouldn’t want to do is take out the tumor and the good lung around it if you didn’t have enough reserve to breathe normally or without oxygen or not be really disabled in the future. Surgeons are willing to operate on you but they have to know that you have enough reserve, so we get pulmonary function studies to know whether you have enough reserve to tolerate an operation.
Another reason to get pulmonary function studies is if you’re having radiation treatments and were, for example, to get short of breath afterwards, we may want to know: is the radiation affecting the lung? Having a baseline set of breathing tests for a pulmonologist is incredibly important — for us, it’s like the EKG that a cardiologist reads, it tells us how you are, how closely you compare to a normal person, and then we can follow you over time. So for example, before lung surgery we can get breathing tests, and then six months or so after lung surgery we might get a new baseline to know how much lung you’ve lost and how well you’re tolerating the procedure of having a piece of your lung taken out. We can also then hopefully sometimes use medications to help improve the lung function, sometimes even before surgery, but certainly after surgery if you're having difficulty breathing.
They’re very simple tests, they don’t hurt, and their information is incredibly useful.