rested gal wrote:
This, though, I do understand and agree with
absolutely:
Pugsy wrote:When it really comes down to it though, 5 L/min variable in leak is really insignificant. The reports and software were never designed to be an exact reporting medium. Designed for trends and patterns to see what is going on in general. We are trying to fit a square peg in a round hole. Nit picking is time consuming, prone to give headaches and when all the nits are picked we still are left with imprecise numbers. They are close and really close enough to give the general idea as to what is going on and that is all it was really supposed to do.
My problem with the "numbers" is not that they are fuzzy. My problem (as a mathematician) is that this critical information about how
to interpret those fuzzy numbers is far too deeply buried for the average, but curious and moderately numerically-inclined patient/user to actually find.
For example: The graphs and verbal information provided about my Swift FX for Her's intentional leak rate include NO mention of +/- error rate---although I know (as a mathematician) that there is one---and the figure Pugsy cites sounds like it's a very reasonable guesstimate. Personally, I've been assuming all along that my "negative" unintentional leak rates are caused by nothing more than the fact that my real unintentional leak rate is pretty darn close to 0 and within the margin of error for the mask. Hence, factoring in the margin of error means:
- -5 L/m <= My real unintentional leak rate <= 5 L/m
which implies
15 L/m <= My total leak rate <= 25 L/m (at 4cm of pressure much of the time)
And even though I've not yet had such a night, this bit of arithmetic means that I'd not be worried (at all) if I started seeing
flattish total leak rate lines up around 25 instead of my more typical 17 to 18. Shape of the curve is more important here than what the exact
y-value is. Oddly enough I've found such +/- margin of error figures in reading OTHER Resmed mask user manuals, just not the Swift FX's.
But the BIGGER problem for users of the PR S1 is that the phrase Large Leak is NOT defined!
The documentation that came with my PR System One BiPAP Auto (both the user AND clinical manuals!), mentions that "large leaks" will show up in the 7 and 30 day averages in the on-screen data and says absolutely NOTHING about what constitutes a "large leak." My Encore Viewer and Encore Pro help browsers say nothing more than Large Leaks are flagged by a change in the Green Bar in the leak graph from darker, bright Green to a ligher, fuzzier green. And without (even a fuzzy) definition, there is no way to meaningfully interpret even the fuzzy data is provided by the machine either on its LCD or in Encore.
For example, I have
NEVER, EVER been flagged with a "Large Leak" in some 100+ days of using the PR S1. Is my mask fit really that good that I've NEVER, EVER had even a short Large Leak in 100+ days of use?
Well, in the roughly 90 days of using the Resmed S9 AutoSet, there were isolated times where my unintentional leak rate went above the RedLine at 24 L/min for as long as 5 to 20 minutes or so. Not on a daily or weekly basis, but certainly a couple of times a month I'd have a brief large leak. Not important from a therapy point of view, but a large leak nonetheless. So this establishes a baseline that at least rarely I have leaks large enough to make the S9 flag them in ResScan as "large leaks."
In the 100+ days using the PR S1, my largest leak was a 20 minute leak with a total leak rate at about 50L/min (twice the intentional leak rate of my mask at my pressures). I've also seen total leak rates this large for somewhat shorter periods several other times---maybe two times a month on average, which is about the same rate as "large leaks on the S9". And none of these leaks on the PR S1 has been flagged as a "Large Leaks" either on the PR S1 LCD or in Encore. So is it really possible that an
unintended leak rate that is as large as the intended leak rate is really NOT a large leak on a PR machine?
That's the mathematician's question that bugs me: To properly interpret how much a patient/user needs to worry about the maxes in their leak rate curve ("Do I have Large Leaks that might affect the quality of my therapy?"), we need to know how PR defines "Large Leak. On the PR S1:
- Is Large Leak defined as a leak exceeding an absolute number---like the 24 L/min RedLine in ResScan? If so, what's the magic number?
Or is Large Leak defined in some kind of relative way? If so:
- Must the unintentional leak be x-percent of the intentional leak rate? And what is x?
Or must the total leak rate be x-percent higher than the baseline leak rate for y minutes? And what are x and y?
