(06-17-2014, 06:17 AM)readyforsleep Wrote: I have reset my pressure to 11-20. My leaks are under contro and my AHI is under
3. I just had to be patient and not monkey around with the low pressure. The higher
I made the low pressure, the higher my pressure needs became. No bipap
needed, I could probably even sleep on my back. I wish I understood why 11 is the magic number....
First to explain something: No matter what pressure you start out with, it's not uncommon that an event or two is going to sneak through the defenses. And if you're using an APAP, the machine is going to respond. It's just that not all of an APAP's increases in pressure are genuinely warranted.
It may help to understand what goes on during a titration study. In a titration study in the lab, there are strict guidelines for when the tech is supposed to increase the pressure. Each time the pressure is increased, the increase is pretty minor: Most of the time the tech will only increase the pressure by 1 cm (2 cm at most). And after a pressure increase the tech will wait for five full minutes
before increasing the pressure again. The reason for that waiting period is that it can take the breathing a while to stabilize after a pressure increase. So the five minute waiting period is to determine whether the current pressure seems fine or whether another 1cm increase in pressure is really warranted because the obstructive events keep coming.
And another reason for waiting before increasing the pressure is to give the tech a chance to see if the increased pressure creates
additional breathing instability, most often caused by the PAP pressure causing the patient to blow off too much CO2, which can trigger central apneas in some unlucky PAPers.
And then some people are also super sensitive to pressure increases, and the higher pressure can simply trigger more spontaneous arousals.
If certain kinds of breathing instability are noted by the tech after a pressure increase OR if there's a substantial uptick in the number of spontaneous arousals, the tech will lower
the pressure by 1cm to see if the breathing stabilizes and/or the number of spontaneous arousals goes down.
Now consider what can
happen on a bad night when you are using a Resmed S9 AutoSet. The AutoSet responds pretty aggressively to clusters of events that the FOT algorithm scores as OAs. As long as the OAs continue to be scored, the machine continues to increase the pressure. And the S9 can increase the pressure pretty rapidly: I've seen posts by users where the pressure goes up by 8-10 cm in as little as 8-10 minutes. When this happens, the S9 is NOT allowing any time for the breathing to stabilize. And under some circumstances, that rapid increase in pressure leads to further breathing instability and more "restlessness" or arousals. The restlessness/arousals can lead to some sleep/wake/junk (SWJ) patterns of breathing that can easily be mis-scored by the S9's FOT algorithm as hyponeas and OAs, and so the S9 continues to increase pressure (if there's still room to increase the pressure) or the S9 continues to keep the pressure at the maximum pressure setting.
The net result is that the overall AHI goes up (sometimes substantially), the events may look like clusters of OAs, and both the median and 95% pressure levels go up.
And, unfortunately, there is a tendency of people on forums like this to look at that kind of data and say: "Whoa---there's a whole bunch of clusters of OAs in your data. That means you need more pressure. Try increasing the pressure up to within 1-2 cm of the 95% pressure and see if that helps." When the pressure increase does not help (because the problem is NOT real OAs, but SWJ breathing and/or some mis-scored centrals sneaking in), the person decides to increase the pressure some more ....
And add to this: A lot of people who are in the active dial winging mode have a tendency to change the pressure settings every couple of days: Every time they have a bad night, they respond by increasing the pressure. But we're all going to have a few bad nights now and then. And there really is some truth to the adage that sleep docs keep telling us: It takes time for the body to fully adjust to PAP therapy.
And a lot of the time AHI's that are a bit too high at the start of PAP will come down without any dial winging as the person's body really and truly learns the ins and outs of sleeping with a PAP.
All that said: I don't think all dial winging is bad. I do think knowledgeable PAPers can indeed optimize their PAP therapy over time with little or no help from their sleep docs. But for that to happen, the PAPer really does need to understand what the problem they're trying to fix is and why pressure changes might actually do some good. And successful dial winging also takes patience: You really do need to give each new increase in pressure a reasonable amount of time before deciding that more pressure is indeed needed.
Quote:People like me are the reason doctors prescribe bricks.
In my opinion, your take is NOT a valid reason for prescribing a brick. After all, when a patient has a brick, the doc is flying blind if/when the patient does NOT respond as expected to PAP therapy.