ozij wrote:While in Ptherapy mode, if flow limitation occurs during the last 4 breaths or over several minutes, the algorithm begins a Popt search.
My emphasis.
I understand this to mean that after 5 minutes the algrithm actively analyses the data for indications of small degrees for flow limitation.
Ozij, I think your interpretation above is correct. But I think that routine you have highlighted happens on a non-scheduled detection basis---regarding the spontaneous detection of slight FL precursors. I also agree with Snoredog that a scheduled or routine Pcrit/Popt/Pther search happens as well. However, that latter scheduled or routine search is for the purpose of finding the lowest feasible pressure---and it starts with an intentional downward pressure probe to ascertain Pcrit's value. Then it probes upward. The upward pressure search you have highlighted is for the purpose of reacting to FL precursors. In summary, one search wants to see just how low the machine can safely take the patient---and routinely attempts just that by first looking downward for Pcrit. The other extremely similar search is not scheduled, and that pressure-response routine wants to escape spontaneous FL precursors by immediately going to higher pressures in search of Popt. In this case a spontaneously generated Pcrit condition is presented; that spontaneous Pcrit condition obviates the need for the algorithm to first probe for a Pcrit value. The algorithm goes straight to an upward Popt search in this case. Of course, that's only my interpretation.
However, what Ozij has highlighted at the top of my post is what I think is probably occurring in Bev's case. Specifically, I think that subtle preliminary indicators of FL likely occur spontaneously---and that precursor presence triggers this particular upward-pressure sequence. These upward probe-triggering flow signal events are not frank FL events. They are some insufficient subset of the individual FL probability criteria. As an example, slight amplitude reduction is one of the FL probability-based scoring parameters that Respironics tracks. It's one of several.
Let's pretend that Bev shows only slight or marginal periodic breathing. In fact, that flow-amplitude up and down action would be so slight, that it wouldn't even be noticed or scored as periodic breathing in the PSG. Recall CompSA/CSDB was just classified in a 2005 Harvard study. Right? And at that point only full-blown respiratory-controller oscillations were delineated. Since that point in time, slight and moderate CSDB/CompSA diagnostic criteria have been developed, albeit not yet fully explored or delineated.
Anyway, let's say that Bev experiences only slight respiratory-controller oscillation. Fairly steady at times, fairly periodic, but ever so slight regarding the ups and downs of amplitude. Not dramatic enough to score as frank periodic breathing (thus not warranting treatment by Respironics' Variable Breathing part of the algorithm). And not an adequately sustained amplitude reduction that might score as one or more hypopneas. But just wobbly enough for the detection algorithm to think that it sees the makings of a slightly collapsing airway (as opposed to a slightly wobbly respiratory controller). And that's pretty much the only precursor sign of FL that the algorithm sees in Bev's case.
So the algorithm doesn't score FL, for lack of all the other probability components of frank FL scoring criteria. But it decides that it needs to pressure probe upward until that flow wobble goes away. And by, golly, pressure goes up and up quite a ways before that flow-amplitude wobble spontaneously subsides.
In general it would be possible for the algorithm to commence that same upward search routine for any subset of probability-based FL precursors---not just the amplitude parameter. That means slight obstruction or transluminal airway collapse (as opposed to respiratory controller oscillation) is a more likely case across the obstructive patient population. Regardless, Bev's not at all out of the running for a slight respiratory-controller issue with all the biologic discomfort and characteristic cyclic alternating pattern (CAP) that goes with slight CompSA/CSDB in my opinion.
Science is still trying to get a handle on the various complex SDB presentations of one
very challenging phenotype IMO.
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Bev, have you been evaluated for the likes of connective tissue and autoimmune disorders---such as fibromyalgia and chronic fatigue syndrome?
