Some DLCO errors the 2017 standards will probably fix

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.

Test 1: Test 2: Test 3: Test 4:
DLCO (ml/min/mmHg): 24.53 17.21 12.91 6.74
Inspired Volume: 1.99 2.06 2.32 2.26
VA (L): 3.83 3.52 3.63 2.60
Exhaled CH4: 43.27 49.19 54.80 74.14
Exhaled CO: 16.09 23.15 31.39 49.46

When I first looked at the graphs for each test, there wasn’t anything particularly evident until I pulled up the graph for the fourth DLCO test:

This graph showed that the baseline CH4 and CO readings were significantly elevated, but this hadn’t been evident in the previous tests.

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