I’ll start by saying that I am not associated with Hans Rudolph Incorporated in any way. I just think they make a bunch of good products, and more specifically in this case, a DLCO simulator.
For as long as I can remember I have always had intermittent problems with DLCO testing and I suspect that every PFT Lab has had them at some time. One of my current concerns has to do with how our test system’s software is calculating exhaled CO and CH4 concentrations from calibration data, but I’ve had other concerns at other times too. One way around to verify that your test system is actually performing the way it should is biological QC but a more precise way is to use a DLCO simulator.
Every PFT Lab should be performing biological QC (self-testing) regularly (and if you aren’t, why aren’t you?). This is the simplest way to check a test system but it does have limited accuracy. My personal experience for DLCO tests is that there was usually a range of about 1.5 ml/min/mmHg (roughly 5%) within the results from a single testing session and 2.5 ml/min/mmHg within session-averaged results over the course of a year. This is good enough to get a general sense of how well a test system is working but not precise enough to pinpoint specific problems. Used correctly a DLCO simulator can produce highly reproducible and accurate test results.