Pressure, O2 desats & AHi relationship -

Had first xpap follow up appt with md (pulmonologist / sleep specialist) last week. Didn't know what to expect in terms of his being open to my participating in my own care. I was very pleased and surprised. I am a "cpaptalk addict" and have learned so much thanks to the generosity of all who share information here!! I had purchased an oximeter and had a few days of reports with me. When he started to discuss O2 I pulled out my reports (with some trepidation) and his response was great. At the end of the appointment he said he thought I should be hired by my dme to help others out. I am pretty techy, have a nursing background and am very tenacious. This has made my initial experience with xpap quite good.

I have mild osa and UARS. MD explained UARS a bit more and explained that although my "stats" are low, other factors showed up on PSG that would explain my symptoms (very poor sleep, frequent awakenings, tired).

Now to my question - MD gave me "full go-ahead" to titrate pressure to see if I improve on O2 desats. He said that my goal should be to get desats down to where I only go below 88% for a minute or less and to increase pressure to see if I can accomplish that.

I started out CPAP at 5, then ran APAP wide open (4/20) a couple of nights and it maxed just under 10 and averaged in the 7-8 range. So, I have gradually increased to 7, then 7.6 and then 8 over the course of a week or so. What I am not seeing is any relationship between increase in pressure and decrease in O2 desats. AHI and HI and CA remain (as they always have) pretty low AHI being mostly 1.0 or lower.

Last night I ran CPAP at 8, AHI 0.9, CA 0.4 and O2 under 88% for 5.7 minutes. And I feel pretty crappy today.

Previous night CPAP at 7.6, AHI 2.4, CA 0.7 and O2 under 88% minutes for 2.5 minutes. And so on... I just am not seeing any correlation. Am I rushing things, is there something else going on? Any comments would be greatly appreciated. I am wondering at what point is supplemental O2 added to therapy. Thanks in advance!

ps - btw, leaks are under quite good control for the past week with Quattro fx ffm - pretty much show up as zero.

Hi, check this conv about Oxygen and CPAP:

http://s7.zetaboards.com/Apnea_Board/topic/8294024/2/

First of all, check your SpO2 graphs for artifacts or lost signal episodes. If you find any, block them out then review your data again.

You might want to consider giving this a try. Set your machine to APAP with the low setting of 7 and then review the data after a few nights to see where you stand. This may help you dial things in a little closer.

Also, you need to consider that the machine is giving you accurate information and there is something else that is responsible for the low O2 levels rather than attributing them to air flow obstructions while you sleep. A good way to check this is to wear your pulse oximeter during the day while doing various activities and see where you stand.

Another consideration is to check the accuracy of your pulse oximeter. Sometimes they can be off.

Finally, I disagree with your doctor. It is good to set an intermediate goal of minimizing desaturations below 88%, but I feel that the ultimate goal is to have no desaturations below 90%. If you live at a high altitude, ignore this. 2% may not seem like much, but over a long period of time its significance can increase.

In my case my average O2 levels did not change when I started xPAP, but the swings below 90% have pretty much been completely eliminated.

As I think more on this, something isn't adding up. However, perhaps an AHI of 2.4 on the S9 is significantly higher than what many people are reporting with many having an AHI under 1. Well, I just re-read what you posted and you are also seeing AHI values below 1.

I am having second thoughts about my earlier recommendation to run APAP. If the machine is not seeing any obstructions, it is not going to give you different information. Perhaps you could consider working your way up to 9 or 10 on CPAP over a period of time and watch what happens...

Sorry for being so wishy washy, but something isn't adding up.

HoseCrusher wrote:First of all, check your SpO2 graphs for artifacts or lost signal episodes. If you find any, block them out then review your data again.

I had one night with the gray line which I believe is lost signal - I had the finger probe on upside down. Otherwise, I am not sure how to identify artifacts. It seems that the data is correct - it correlates with low SpO2's on overnight oximetry from md's office and during psg.

Perhaps you could consider working your way up to 9 or 10 on CPAP over a period of time and watch what happens...

I'm trying that. Last night had 3 hours at 8, 2.6 ahi during that time, headache, felt crummy, fewer desats; then 6 hours at 7, no events but more desats - huh?

You need to consider that the machine is giving you accurate information and there is something else that is responsible for the low O2 levels rather than attributing them to air flow obstructions while you sleep. A good way to check this is to wear your pulse oximeter during the day while doing various activities and see where you stand.

I agree. I'll check daytime O2 - I've never seen it low. I live at altitude of 6200 feet and ski 3-4 times a week at 8,000 to 10,000 feet with no respiratory problems. I assume then that altitude consideration is why md says keep above 88% at night...

Sorry for being so wishy washy, but something isn't adding up.

I agree. Does this have something to do with UARS? MD explained it as something that does not quite score as a hypoxia but can create problems. Would Rescan "flow limitation" graph indicate anything. I don't know how to interpret that.
I read avi123's link about oxygen and cpap. Interesting. They mentioned that bipap might be a solution for o2 problems. I'm not well versed on bipap.

OK, at over 6000' 88% is a good goal...

After thinking about this more, it appears that the xPAP machine is not recognizing the problem, so if it is pressure related you will have to use CPAP instead of APAP.

Your problem is compounded by at least 2 issues. 1. You are not a machine and don't sleep the same every night. and 2. SpO2 values are not very accurate below 90%.

This means that as you "inch" up your pressure, you should spend something like 3 nights at each increment to get an average of the results. I would also recommend, if you aren't doing this already, that you keep a sleep log. When you wake up, assess how you feel and how you think the night went. Then jump out of bed and write these thoughts down. Now you can log in your data and see if there is any comparison with how you think things went.

The issue of the accuracy of the SpO2 readings below 90% should not be a concern unless you decide to add oxygen. It is my understanding that there are formulas that predict the amount of oxygen to add to increase blood oxygen by a certain amount. If you are basing the amount of oxygen needed on blood gas test results, the formulas are very good, but when basing the amounts on SpO2 readings, you have to go in steps because of the inaccuracies of the SpO2 at lower levels.

This means that depending upon how far below 88% you desaturate, you may want to consider dropping the pressure slightly after attaining your goal just to make sure you didn't end up over pressurizing yourself. This is most likely a "non-issue," but when dealing with complex conditions I like to throw all the cards down on the table so the limitations of the technology are disclosed and understood. The non invasive SpO2 measurements are far better, even with its limitations, to having a "vampire" draw blood from you all night in hopes of catching the lowest desaturation moment.

HoseCrusher wrote:After thinking about this more, it appears that the xPAP machine is not recognizing the problem, so if it is pressure related you will have to use CPAP instead of APAP.

Good point. I have been using straight CPAP - and am keeping a pretty detailed log (thanks for that suggestion). I have kept CPAP at same pressure for a number of nights. I do not see any relationship between SPO2 and pressure. The number of minutes below 88% are either high (4.8 - 5.4 minutes) or low (0.2 last night) but are not pressure related (running either 7 or 8 ). Also, they are not related to "events" - when I look at graphs for low SPo2 and events (oa, ca etc) on Rescan, they to not correspond with each other.

I seem to feel pretty crummy the next am if # of Min >88% is greater than 1 minute.

This means that depending upon how far below 88% you desaturate, you may want to consider dropping the pressure slightly after attaining your goal just to make sure you didn't end up over pressurizing yourself.

I'd love to get to that point. I just haven't figured out relationship between pressure and desats.

Thanks so much for your input.

HoseCrusher wrote:Sorry for being so wishy washy, but something isn't adding up.

Here's an update, with a special thanks to HoseCrusher for being "spot-on" with "something isn't adding up".

Looks i started this thread in February, soon after starting with S9 autoset. I have had some real progress since then and thought that I would share. After starting to use my S9 autoset and reading a lot here on cpaptalk, I began to realize that I wasn't falling into the category of "high AHI, use xpap, get low AHI". What I was experiencing was a very low, almost non existent hypopnea/obstructive index. 98% of my events were centrals and they did not seem to disappear after weeks/months on cpap. I also had a very consistent number of desats with spo2 dropping below 88% for 4-6 minutes per night.

1st doc said "not to worry, everyone has some centrals". But, I was not feeling good. I ended up getting a 2nd opinion, a repeat psg and titrations with a really good sleep clinic. And now, that I have been treated by two doctors and two sleep clinics I am so aware of the difference between an "ok" and really excellent experience with md's and labs.

I went from a diagnosis of "mild apnea in the form of upper airway resistance" to Complex Sleep Apnea. New doc prescribed S9 vpap adapt which I have been using now for 2 weeks. I love it! It is so comfortable to use and I am doing much better. The centrals have disappeared, 100%. My AHI is consistently zero, ok well maybe I have had 4 hypopneas in 2 weeks. I no longer have any desats. The number of minutes <88% is always zero. My spo2 runs 91-92%. In the lab I averaged 95% during the asv titration but the altitude was about 1000 feet lower than where I live, so maybe the 91-92% is ok. I will check on that during my follow-up as I'd like to see it higher.

I am posting this in the hopes that it may help someone. I also want to give a special shout-out to HoseCrusher who so kindly checked in with me to see how I was doing. Thanks HC for that!

Excellent news. I love it when the puzzle finally gets solved.