Three on Lung Function

The effect of errors in Inspiratory Volume on DLCO.

Sun, 19 Nov 2017 00:00:00 +0000

Yesterday while reviewing reports I ran across an interesting error in the Inspiratory Volume (VI) from a DLCO test. I’ve probably seen this before but this time I realized what effect it could have on DLCO. Specifically, what I saw was that at the start of the DLCO test the subject had not finished exhaling and although the technician had started the test, the subject continued to exhale.

What makes this interesting is that the software used the subject’s volume at the start of the test as the initial volume. This means that the software measured the VI from the initial volume to the end of inspiration, not from the point at which the subject stopped exhaling to the end of inspiration. This also means that the VI was underestimated by 0.20 L and this affects both VA and the calculated DLCO.

DLCO, de-constructed

Wed, 15 Nov 2017 00:00:00 +0000

My wife watches the Food Network a lot and I occasionally watch it with her but I can only take so much of it before I go off and read or work on one of my projects. I’ve noticed however in the various cooking contests that sometimes a chef will deconstruct a familiar recipe. This more or less means they break the recipe down into its components and present them as separate pieces or perhaps by putting what goes inside on the outside instead.

What’s wrong with an elevated DLCO?

Sun, 17 Sep 2017 00:00:00 +0000

Well, not necessarily anything, although as usual that depends on the circumstances. Recently I was contacted by an individual who was concerned that their DLCO had decreased from 120% of predicted to 99% of predicted. They also mentioned that their DLCO results have normally ranged from 117% to 140% of predicted over the last 9 months.

More interestingly however, they said that

“the technician told me before I even took the test that anything over 100% for DLCO is essentially a testing error.”

Some DLCO errors the 2017 standards will probably fix

Sun, 12 Feb 2017 00:00:00 +0000

Last week I ran across a couple errors in some DLCO tests that I don’t remember seeing before, or at least not as distinctly as they appeared this time. If I hadn’t been looking carefully I could have missed them but both sets of errors will be a lot more evident when the 2017 ERS/ATS DLCO standards are implemented.

The first error has to do with gas analyzer offsets. What alerted me was a set of irreproducible DLCO results.