-SWS wrote:patrissimo wrote:Code: Select all
Obstructive
Apnea Index 0.4±0.9 0±0.2 -0.3±0.7 0.044
so p = 0.04.
Certainly far weaker than the strength of the evidence for reduction of central apneas, but also far stronger than the claim you and some others seem to be making that there is no evidence ASVs are better for purely obstructive events.
Of course you're welcome to interpret that data as you see fit. In my view, interpreting how well ASV treats obstruction in a centrally-dysregulated population says nothing of how well or poorly ASV might treat the OSA population. What are the pathogenic differences in those two populations with respect to cause and mitigation?
Your following analysis assumes that obstructive apneas in a central population are of the same pathogenesis and treatment requirement as OSA. Ignoring that there are multiple pathogenic types of airway obstruction---with some types responding better to volumetric treatments while others respond better to static pressure---seems more specious than parsimonious to me.
I believe you have a technical background, but you don't seem very familiar with statistics. What you say would make perfect sense in the world of, say, mathematical proofs. In the world of statistical associations, however, it is incorrect. The fact that A != B does not mean you cannot infer anything about B from A. For example, let us suppose that half of obstructive events in plain OSA are the same as obstructive events in ComplexSAS, while the other half are unique to plain OSA and have a different pathogenesis. You would say "Hey, they aren't the same! Stop trying to make claims about one population from results on the other!"
But statistically, this means that any evidence we have on, say, the performance of ASV vs. CPAP on one population applies 50% to the other. If ASV is twice as good as CPAP at reducing the OAI in ComplexSAS, we would expect it to be 1.5x as good on OSA. That is basic statistics. Of course, if we tested it, it probably wouldn't turn out to be 1.5x as good, because the two treatments likely wouldn't be exactly equal at the 50% of events that are unique to plain OSA. But the most accurate guess we can make using that information is 1.5x - that ASV will do twice as well on the half of events that are the same, and that the two will perform equally well on the events that are different (that's our best guess when we have no other information about relative performance on this sample).
In order for ASV vs. CPAP performance on obstructive apneas in ComplexSAS to tell us *absolutely nothing* about ASV vs. CPAP performance on obstructive apneas in OSA, it would have to be the case, not merely that they are somewhat different, not merely that the populations aren't identical, but that there was
absolutely no similarity. If there is
any overlap in pathogenesis between the events in the two populations, then we can statistically infer that a treatment that is better on one is, before testing, more likely than not to be better on the other.
And in this case, I don't think it is anywhere close to "no similarity". After all, the ComplexSAS population is not some totally different group of people with a totally different condition. It is simply the set of OSA sufferers who cannot splint their airway with enough pressure without inducing central apneas. If we take a large population of untreated OSA sufferers, and begin splinting their airways with CPAP at 1mm, 2mm, 3mm, etc, we will see the AHIs (presumably) decrease, and at some point, for some people, the CAI will start to rise above zero. We stop titrating each individual when either a) the AHI has reached a local minimum (we call this "Plain OSA"), or b) CAI > 1 (we call this "Complex SAS"). Will there be differences between these two populations? Absolutely! Will there be similarities between them? Absolutely!
Will all treatments (Breathe-rite strips, sleeping on their side, weight loss, BiPap) work equally well on both groups? Of course not! If a treatment works on one group, does that tell us that it is more likely than not to work on the other group? For sure!
And all of this is ignoring the data point that ASV reduced the OAI to 0.0 (+/- 0.0) in the opioid study, while CPAP did not. This contradicts your claim that "there are multiple pathogenic types of airway obstruction---with some types responding better to volumetric treatments while others respond better to static pressure". Clearly every single type of airway obstruction in every patient in that opioid study responded to ASV, and a few of the types of airway obstruction in a few of the patients did not respond to CPAP (while most did). We are not left simply guessing, we have data. And the data says "there are two kinds of obstructions in this population, those that respond to CPAP or ASV, and those that respond only to ASV. There are no obstructions that responded only to CPAP". In the other studies, the AHI from ASV was not zero, but it was lower. So either there are some obstructions that respond to neither, or there are some that respond only to CPAP, but not very many.
It's certainly possible that we could find a population where there are more "CPAP-treatable only events" than "ASV-treatable only events", and hence that CPAP would be better for that population. But the fact that it is possible does not mean that it is more likely to be true than to not be true. Based on the data we have, in all the populations that have been sampled, ASV eliminated more obstructive events than CPAP. So if we are making a guess about a new population, then unless we have specific information which demonstrates that the new population has more of the "CPAP-treatable only events"events than the populations we have previously sampled, our most accurate guess is that ASV will perform better. Just like if one baseball player has a higher batting average than another in their rookie season, we should bet that the same player will have a higher batting average in year 2, unless we have specific info ("he got injured") to the contrary. It isn't a sure thing, but if you have to bet on one side or the other, there is a clear favorite.
Sorry for the long rant, I'm frustrated that what seems like such a simple statistical argument is not clear, and I'd like to hash this one out in detail, both because it is important in and of itself (ASV vs. CPAP for plain OSA seems to be a topic of much interest on this board), and so that when I make similar statistical arguments in the future, y'all accept and understand them.
patrissimo wrote: Well, the data is starting to get scanty, but...
All argumentation aside, good luck with your quest to treat your residual EDS. I see nothing wrong in trying ASV.[/quote]
Thank you! I'm going to keep cranking up the pressure on my APAP for now, and if I continue to show SDB in the data, as I have so far, I will rent a BiPap or an ASV.
