Pulmonary Function Tests Discussed at ILD Meeting

This month’s Interstitial Lung Disease meeting featured Pulmonary Function Tests (PFT). The wonderful Dr. Eunice Kim walked us through the maze of numbers and alphabet soup.

She began with the reason for PFT:

            Shortness of breath

            Determine severity of the damage

            Progression of the disease

            Pre-op evaluation

Spirometry is usually the first test given. People with emphysema and COPD are also commonly given this test. It begins with regular breathing, then instructed to exhale all the air from the lungs that one can, then told to inhale as much as one can, then exhale as hard and fast as possible.

If you are diagnosed with an Interstitial Lung Disease, the most important numbers to know pertain to Volume Capacity (VC) and Diffusion (DLCO).

Lung Volumes are usually determined using a test called plethysmography, or as we call it, the clear box. The patient is locked into a clear box and measuring the changing pressure and a fantastic math formula, one can get a very accurate measurement of lung capacity using this method.

Diffusing Capacity  measures the exchange of gasses from carbon dioxide to oxygen. During the test, a small amount of carbon monoxide is inhaled then held for a few seconds, then exhaled hard. The computer measures the amount of carbon dioxide exhaled.

The transference of gasses is probably what will kill all of us with an ILD. We will not be able to clear the carbon dioxide from our blood and gently fall asleep – or that is how I am hoping it happens!

So, first ask for a copy of your latest PFT. Learn what all the numbers mean and follow your own progressions. These numbers will vary because of different machines, lab personal conducting the test and the general well being of the patient, though it should not be a huge fluxuation.

Another thing I forgot to mention is that what is most important is the numbers in percentages. They studied a group of well people of all different heights, ages, weights and races to determine what is “normal.” That is 100%. When the results of the tests are read, pay attention to the percentages more than the actual numbers. 

For example, my DLCO may be 13.4 and for my age, weight, height and race, that is 51% of expected. My VC is often in the low 60% of expected. It is easier to compare apples to apples using the percentages.

So, your job is to learn what your numbers are and follow the progress of your disease.

Another note:  There were several people at the meeting whom I had yet to meet. As I spoke with each of them, it was rather interesting when I realized that each had an ILD and also Rheumatoid Arthritis. So interesting that the two seem to go together.