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The Basics of Pulmonary Function Testing


One of the topics that I see talked about a lot in support groups is pulmonary function tests. There are questions that swirl around like, “What do all those tests mean on my pulmonary function test?” and “What can I expect when I get my pulmonary function test.” Most patients that have a lung condition at some time or another are scheduled for these tests. A pulmonary function test or PFT is actually a series of tests to show how well the lungs are working. A PFT is painless (although for some people with certain lung conditions state that it is exhausting) and consists of being coached by a pulmonary function technologist or respiratory therapist to perform certain breathing exercises to achieve measured results. The measurements that are taken during a PFT show a person’s lung volume, capacity, rates of flow, and gas exchange. The information obtained from these tests will help your physician diagnose and determine the course of treatment they are to provide. As you can imagine, the information gathered from these tests are invaluable and if done routinely can show your physician the rate in which your condition is progressing.


For the purposes of today’s blog, I am going to give you “the basics” of PFTs. The information contained in this blog will help you to prepare for you pulmonary function test and know what to expect during the test. I am also going to give you an idea of some of the data that they are going to collect from the PFT. For all intent of purpose, you need to let the evaluation of those numbers be up to the physician who is interpreting the results. However, maybe after reading my blog you will be able to see which areas that you may have deficits. Remember, PFT interpretation is up to the “pros.” The results from these tests in conjunction with other assessments will allow your physician to adequately diagnose and treat you.


What to Expect Before Your PFT


You can usually count on the test lasting anywhere from 45 minutes to an hour. I recommend you follow all pretesting recommendations prior to your PFT. In many cases, the test requires that you refrain from using certain breathing medications 12-24 hours prior to your testing time. The reason for this is so that when you are performing the PFT, the clinicians can find out just how well your lungs are functioning on their own and they also have the option of giving you a breathing treatment during the test to see if there are any improvements in your functionality by using breathing medications. You will not be given any medications during the test to impair operating a vehicle so there is no need to schedule someone to drive you to the test unless you need moral support or you aren’t currently driving. I recommend that you also refrain from eating a large meal prior to the test (but don’t go hungry either). A huge belly full of food can prevent your lungs from inhaling fully. Dress comfortably. If you are a smoker, refrain from smoking at least an hour before the PFT however, the longer, the better.


What to Expect During the Test


Basic Spirometry is typically the first test your respiratory therapist or pulmonary function technologist will perform. Spirometry measures the amount of air you breathe in and out. This will have you sitting in front of a machine and being fitted with a mouthpiece. The mouthpiece will fit snuggly in your mouth and you will be required to breathe in and out through the mouthpiece. A nose clip will be put on your nose to ensure that all the air flowing in and out of your lungs is going directly through the mouthpiece. During this test the therapist or technician will have you breathe normally and then will coach you to take deep breaths and blow hard. Pay close attention to their instruction. Their job is (like any good coach) to get the best performance they can from your lungs. I have known some coaches to be very “peppy” with their coaching and others to really be animated with their tone. Trust me. It’s for your benefit that they get the best results for your physician to interpret. Try not to get frustrated if you are asked to repeat a breathing test multiple times. The technician or therapist running the test wants to get the most accurate measurements possible and this can take repeated attempts at getting the best result. After these tests are done, you may then repeat them after getting a breathing treatment.


The Plethysmography test (say that 5 times really fast) measures the volume of gas in your lungs. You will be asked to sit or stand in a small booth and breathe into a similar mouthpiece and you again will have nose clips. If you are claustrophobic let your technician know and they will do their best to leave the door open to the booth as much as possible when they aren’t gathering data. While in the booth your will be asked to do a series of breathing tests.


The Diffusion Capacity test lets your physician know how well the alveoli (tiny air sacs in your lungs) are working. In this test, we can find out how well your lungs are able to move oxygen in and carbon dioxide out. In this test you will use that same mouthpiece and nose clips from earlier.


So, What Does All This Info Collected Mean?


The information gathered from performing spirometry is compared to predicted values based on your gender, height, and age. When you receive your test results it will give you measured values, predicted values, and percentage of predicted values. As I said before, we are going to let the interpretation lay on the hands of the physicians, however, here are some of the measurements collected.



Patterns seen in Respiratory Diseases


I found that the University of Iowa Health Care had great information on patterns that are seen with the information collected by pulmonary function tests.


Obstructive Patterns:

Decreased FEV1, normal or decreased FVC, and decreased FEV1/FVC

Classically, these are the patients with asthma, chronic bronchitis, or emphysema


Restrictive Patterns:

Decreased TLC, FEV1, and FVC with a normal FEV1/FVC, and a low DLCO

Typically, these are patients with interstitial lung disease, severe skeletal abnormalities, or diaphragmatic paralysis


Last Tidbits


Hopefully you found this information helpful and I didn’t bombard you all too much with clinical jargon. My final thoughts are that if you do have a PFT performed, ask to have a follow up meeting with your physician for the sole purpose of reviewing your results. This way you can get clarity on areas of deficit or concern. Many people wait for a call from their physician to let them know if there was an issue with your testing however, as a patient it is your right to know your results and what they mean. Your physician will be happy to review these results with you but make sure when you are scheduling the appointment that the receptionist knows that you will need the time with your doctor for this discussion.


Thanks for Reading!


If you enjoyed this blog, I invite you to check out some of the topics I have covered in the past


Take Control of Your Lung Condition

From Setup to Use. Feeling Confident with Oxygen Tanks

Rise and Shine. Tips on How to Start Your Day When You Have a Lung Condition


Remember: We are in this TOGETHER!


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:) Christina


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