autopaps

I just finished reading the larger threads on autopap and cpap. I don't mean to start another long topic, but this question didn't seem to fit in the thread.

My doc gave me a cpap with a pressure of 10. I wanted to collect my own data, felt my therapy deteriorated over time, etc so I bought my own autopap.

There was a lot of discussion of which machine is better - not really concerned with that right now - but a question I have, is this if I can make it sound sensible.

If the prescribed pressure is 10, why would a doc or a patient want to have an autopap with the minimum pressure set to the prescribed level of 10. That way you are operating at the prescribed pressure unless the autopap determines it needs to increase to control the apneas. If the sleep study, doc, patient, etc were "spot-on" then there would be little variation for the minimum pressure. If things have changed or were inaccurate then you'd see that the minimum prescribed pressure was/wasn't sufficient.

Is my thinking skewed or does that make sense?

It seems with the minimum pressure set at the prescribed level that one would benefit the most because the doc has determined this pressure level to be the "right" setting, but the equipment can adjust higher if required.

I was prescribed 11cm and had a cpap set at 10cm for the first month of treatment. I then decided to go the apap route and began with it set at the widest range, ie 4cm to 20cm. By monitoring the results, I have gradually narrowed that range to the one that suits me best and now have it set for a range of 6cm to 10cm. I discovered that I spend most of the night at 6cm or 7cm and only rarely go above that range. Over six months, I went above 10cm only a couple of times, for a matter of minutes.

The point is that the prescription is based on a snapshot, perhaps of only one night, and often in circumstances that don't match your normal sleeping situation. Other circumstances, such as weight, can also change over time.

By definition, a cpap is set at a pressure that deals with the higher end of your pressure needs, as it based on dealing with events for 90% of the time. For most people, the minimum is likely to be lower than the prescribed pressure and the higher setting at or just above the prescribed pressure.

MaskedMan wrote:...If the prescribed pressure is 10, why would a doc or a patient want to have an autopap with the minimum pressure set to the prescribed level of 10. .... If things have changed or were inaccurate then you'd see that the minimum prescribed pressure was/wasn't sufficient.

Is my thinking skewed or does that make sense?

Your thinking is very wise! You'll find many cases on this forum where the individual's PSG titrated pressure ends up being higher than what they actually use on a nightly basis with their auto.

If your titrated pressure is 10, drop the low end to 7 for a week and examine your data. Maybe you'll discover your needs never require the pressure to drop below 7, you spend most of your night at 8, and occasionally hit 9. In the weeks that follow, you may want to continue experimenting with your range until you've found the optimum treatment with the least resultant events. (You'll want to experiment with straight CPAP pressures as well, bearing in mind it is possible you'll learn your best treatment is obtained in CPAP vs APAP mode.)

Just one bit of advice: there is the possibility the low end pressure can feel too low to the user, and he/she feels starved starved for air. (I am one of them! Anything less than 8 and I feel like I'm not getting enough air!)

Keep us posted on what you learn!

Definately will, I am used to evaluating data and such. Different thread, but I'd sure like to find much more detail surrounding the data figures and expected typicals.

I've only used the APAP one night so this certainly is not anything conclusive - because of my personal sleep pattern I just found the following info interesting and I am interested in seeing it over the long term:

I noticed right in the area of when I would be waking up that the "acoustical vibrations" went way up, had a few apneas, the pressure shot up, and then I woke up and got ready for work. The thing that grabbed my interest was that the rest of the night was a fairly smooth curve of pressures and events, but that "waking hour" really stood out. For me, I am an enormously hard sleeper and I almost have to shock myself into waking up, so I am interested to see the trend for that "waking hour" over time.

I noticed right in the area of when I would be waking up that the "acoustical vibrations" went way up, had a few apneas, the pressure shot up, and then I woke up and got ready for work. The thing that grabbed my interest was that the rest of the night was a fairly smooth curve of pressures and events, but that "waking hour" really stood out.

I'm not a doctor, nor am I good at interpretating data results. But it's my understanding that as the night progresses, our intermittent REM periods also get longer. The longest time spent in REM is normally during our last sleep time before waking up in the morning - or so I've read.

Since most "events" (apneas/hypopneas) happen while in REM, that might account for the increased pressure activity by the machine (and account for the increased number of events slipping through despite the machine's efforts) before it was time for you to get up.

Many find that an autopap set with the low considerably lower than their "prescribed" pressure works great for them...letting them spend most of their night at more comfortable lower pressures, just above the "air-starved" low.

Others (I'm one) find they do best if the low pressure is set at or very close to the titrated pressure. In those cases, the events (likely in REM) probably hit so suddenly and continue so hard and heavy that the titrated pressure (or perhaps even more than the one-night sleep study titration found) is needed as the "low".

It becomes a trade-off with a lot of examining many nights in a row, making a tweak, examining more nights in a row...to arrive at the range (or perhaps even a single setting) that gives best results. Sometimes it even takes changing to a different autopap for a few people. Most of the modern autopaps work fine for most people, but occasionally there can be a person for whom only one particular brand of autopap (or even another type of machine altogether) is needed to get the job done.

Thanks for the info. This probably sounds nutty but I'm anxious to collect enough data to analyze!

Rested Gal wrote:

nor am I good at interpretating data results.

Rubbish! I think you are da' bomb! Your anlaysis of my data was exceptionally helpful.

No, it doesn't sound nutty! I originally bought the software for my auto with the intention of conducting self-titration experiments to zero in on the best treatment. But I didn't stop there! I still check my stats every morning and notice the fluctuations depending on the mask I'm using, the machine I'm using, etc. But WillSucceed and rested gal are really into it!! Read this:

Nightly Files

Maybe I should qualify my answer.... It doesn't sound nutty to equally nutty cpap-users......