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Thank you for the advice about setting the machine on straight cpap. I'm curious, though, about why you think that would be better. In either case, the dependent variable is still the AHI. We can vary the independent variable - min setting or cpap pressure - and get just as good a read on the ideal setting. The 90% score isn't an ideal measure but it seems like a good place to start. (I am worried that it might covary with the min score so you don't get true score if the min restrains it in some way). I don't know why he would prefer the straight cpap unless of course it repsonds to events differently in a way that I don't yet understand.

Also, do you have any thoughts about the pattern I described of raising the min pressure and getting a low AHI only to find that in the following days the AHI and the 90% begins to creep up again? It seems like a process of adaptation, but I would think that this shouldn't apply here otherwise we would all be up at the max pressure in fairly short order.

VicRob wrote:Thank you for the advice about setting the machine on straight cpap. I'm curious, though, about why you think that would be better. In either case, the dependent variable is still the AHI. We can vary the independent variable - min setting or cpap pressure - and get just as good a read on the ideal setting. The 90% score isn't an ideal measure but it seems like a good place to start. (I am worried that it might covary with the min score so you don't get true score if the min restrains it in some way). I don't know why he would prefer the straight cpap unless of course it repsonds to events differently in a way that I don't yet understand.

Also, do you have any thoughts about the pattern I described of raising the min pressure and getting a low AHI only to find that in the following days the AHI and the 90% begins to creep up again? It seems like a process of adaptation, but I would think that this shouldn't apply here otherwise we would all be up at the max pressure in fairly short order.

Do you have the software and card reader to download your data and see what happens in the reports?
If the answer is "No", then you need to stick with CPAP mode and fixed pressure.
If you're getting your data from the LCD screen, you need to clear it after recording each night's numbers.

Do you know what the "90% pressure" number signifies?
If you don't, then this is the answer: It's the pressure number that the machine spent 90% of the night AT or BELOW.
It is NOT the pressure at which the machine spent 90% of the night.
If you have leaking problems (mouth or mask), that 90% pressure number can become meaningless.

Like I've said, the 90% number is a moving target and in many cases meaningless.


Den

I'm aware of the limitations of not having a card reader and software. Unfortunately all I have access to right now is a MAC and the software is incompatible. I do clear the data every morning so the numbers I use are derived from a single night.

Sure, the 90% is a percentile score. It points the way to a solid setting for minimum pressure - the dependent variable is still the AHI score and a systematic approach to lowering it using the autominimum score should work. Really, there aren't that many other variables that we can control. The min and max settings, the c-flex, the ramp, the humidifier. I tape my mouth shut so I am able to reduce at least one source of leakage. The mask leakage is under control.

I am new to this material. If I am missing something please let me know. I would like to understand the way this device works.

Victor

VicRob wrote:I'm aware of the limitations of not having a card reader and software. Unfortunately all I have access to right now is a MAC and the software is incompatible. I do clear the data every morning so the numbers I use are derived from a single night.

Sure, the 90% is a percentile score. It points the way to a solid setting for minimum pressure - the dependent variable is still the AHI score and a systematic approach to lowering it using the autominimum score should work. Really, there aren't that many other variables that we can control. The min and max settings, the c-flex, the ramp, the humidifier. I tape my mouth shut so I am able to reduce at least one source of leakage. The mask leakage is under control.

I am new to this material. If I am missing something please let me know. I would like to understand the way this device works.

Victor

Here's a place to start:

http://sleepapnea.respironics.com/techn ... rithm.aspx


Den

I've spent some time studying the algorithm that you furnished to me in a link. I'm afraid I could use some help in understanding the chart and what the implications it holds for those of us trying to find the right setting using our autopaps. Wulfman, can you provide me with some direction?

Still struggling to find the right setting for my auto cpap. I have been raising it slowly from 8.5. Usually, when I raise the minimum, the AHI goes up for a day and then down for a few days and then----back up! I recently bumped it to 13 and my AHI went to 6.4 the first night to 8.2 the next night! I thought it was supposed to go down with increased pressure! The leakage is well within normal limits. I don't have a card reader or software because my computer won't support it. Can anyone give me a clue what's happening????

First, I have had the experience you have, of increasing the pressure, getting better scores, then slowly seeing an increase in AHI. I can't explain why it is happening, but I have moved from my titrated number of 7 to 10 as my minimum, pressure. At this point I am waiting to find out the results of some other pulmomary tests before I push it any higher. Most nights my AHI is under 3, so that seems fine for now.

A couple thoughts. How long do you leave the change in place? There is a natural variation from night to night. I find every 5-10 days I have 1-3 significantly worse nights, then things drop back to better numbers. It is possible that if you change your pressure too soon, you won't see what your pattern is.

Once you get to a certain point in pressure, increasing it more can cause central apneas. I understand this is most likely over a pressure of 10. Since they originally titrated you at 16, you may just need to go up very slowly, or it may be that 13 is going to be too high for you. Some people will have centrals when initially given a pressure, but over time your body adjusts, and you can tolerate the pressure.

Hope this helps a little.

mermer40 wrote: Also, my leak rate is not really a good barometer because I have the itchiest nose in the world an am always pulling the mask away to scratch! Anyone else have this problem or am I the only monkey with fleas?

Wulfman's advice (about rubbing your nose and face vigorously where the mask sits, prior to masking up) is good. I've also read about another helpful suggestion here: Some people who wear a nasal or full-face mask keep a popsicle stick handy, like on the nightstand. You can slide the popsicle stick up under the mask and scratch the itch without breaking the seal so much.

I started with CPAP in late March with an Auto range of 4 - 20 set by my Sleep Lab on my "loaner" AutoCPAP (same model that I bought online in early April). After trying UNSUCCESSFULLY in Auto Mode (I tried various pressure ranges) to figure out what caused my AHI, time-in-apnea, etc. numbers to move up or down, I took the advice of this Forum's pros like Wulfman and switched in late April to a constant pressure CPAP modality. With CPAP modality, I am able to figure out what changes that I make (sleep hygiene, different masks & mask fittings, controlling mouth breathing and mask leaks, sleeping positions, etc.) have a positive effect on my sleep therapy. In order to see my Flow Limitation #s, I am now running in AutoCPAP modality with Min Pressure = Max Pressure.

Now that I understand what external factors cause my sleep #s to go up or down and have achieved very good sleep results (feeling rested and AHI < 1), I raised my pressure from 7.5 for June to 8.0 for July to see if I can get more consistent AHI numbers and also reduce the number of flow limitations. If I don't experience any discomforting side effects AND my numbers become more consistent and with fewer Flow Limitations, I will raise my pressure to 8.5 for August.

Based on my recent CPAP therapy experiences in following Wulfman's and other Forum pro's advice to do CPAP first, I would recommend that new CPAP users start out with a constant CPAP pressure and, after figuring out their masks, controlling mouth breathing leaks, etc., switch to Auto CPAP with a pressure range IF they aren't getting restful sleep and good sleep #s at a constant CPAP pressure.

Thank you all for the recent suggestions. I have been having difficulty finding the right range - last night I bumped up to 14/20 and found it to be too much pressure. I am going to back down to 12/18 where I got the most consistent results - AHI around 5 plus or minus 2. Still not a great score.

I am taking into consideration a number of comments about returning to straight cpap mode. I don't know that I can do 16 - the score I was titrated to by the sleep doctor because it seemed like too much pressure. . (The chart they gave me with the study only went up to 13 so I don't know where he got 16). But I can start lower and try bumping up, I suppose. It is hard to be patient and give each setting a several night trial and not want to change it right away.

Are there distinct benefits to straight cpap mode? Intuitively it seems better to use a range of pressures that gives greater flexibility in responding to events.

VicRob wrote

Are there distinct benefits to straight cpap mode? Intuitively it seems better to use a range of pressures that gives greater flexibility in responding to events

After reading the manufacturer's published information on their Auto CPAP machines, I believe most people have the same intuitive feeling regarding Auto CPAP machines. I certainly did which is why I tried to use mine in Auto mode with a pressure range for nearly a month. As I learned more from reading this forum, I realized that an Auto was not the Holy Grail for me, and that I could try a simpler approach by switching to straight CPAP. Straight CPAP is working for me. I believe that my Sleep Apnea is less complicated than others on this Forum as my pressure is only 8 cmH2O and I have few centrals.

For some who need higher pressures to stop Apneas & Hypopneas, especially during REM sleep or when sleeping on their backs (not recommended), the Auto CPAP may be a good fit as it can stay most of the night at lower, more comfortable, less prone to leakage pressures, and only increase to the higher pressures for the REM or back sleeping times of the night. My sleep studies showed a much higher AHI during my REM sleep and when I slept on my back. I no longer sleep on my back - I trained myself using a middle-of-the-back tennis ball tied to my nightshirts and two pillows on either side. With straight CPAP, my Apneas and Hypopneas, when I have them, are randomly distributed during the night. I don't experience any clustering that would suggest that they are only occurring during my REM sleep. For these reasons, it appears that I am not the typical candidate for an Auto CPAP with a pressure range. One other fact that I learned from the experienced and often very technically proficient members of this forum is that Auto machines take time, sometimes a long time (many minutes), to reach a pressure that is needed to "stop" the Apneas and Hypopneas. They do not react immediately, an impression (false) that I had initially from reading the manufactures' marketing materials.

You have the final say as to what to try in your therapy. Whatever you decide, just keep learning and trying various changes and recommendations until you reach your sleeping goals.