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Use CPAP machine to get a new baseline AHI?
#1
I am thinking that down the road a little bit, I might want to have a follow up to know what my AHI is when not under treatment.

My AHI on my October home sleep study was 15. However in addition to APAP treatment, I am trying to get into better shape by exercising regularly and eating better, to lose weight. I don't know if that will make any difference, but I would be interested to find out.

Can I use my APAP to simulate a sleep study, instead of going back to the clinic?

My treatment pressure is 4 to 20.

If I was to set the machine to put out a very low flow for one night (non-auto), is that a potential way to get a new baseline AHI? I guess that even with any flow it is not quite a simulation of what it would be with no treatment. But maybe it would be close enough to use as an estimate.
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#2
(11-08-2016, 02:25 PM)blueelement2016 Wrote: If I was to set the machine to put out a very low flow for one night (non-auto), is that a potential way to get a new baseline AHI? I guess that even with any flow it is not quite a simulation of what it would be with no treatment. But maybe it would be close enough to use as an estimate.

Will not work. You cannot control flow, only pressure. If you try to set a low, fixed pressure ( 4 cm is the lowest it will go) you put yourself at risk. It will not give you an untreated AHI baseline.

There is always a subset of hoseheads who think they can beat the machine and get off PAP. They'll try anything; and for the most part, nearly all fail.

You want a new untreated baseline; you have to set up at a minimum a new home test.
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#3
(11-08-2016, 02:42 PM)justMongo Wrote:
(11-08-2016, 02:25 PM)blueelement2016 Wrote: If I was to set the machine to put out a very low flow for one night (non-auto), is that a potential way to get a new baseline AHI? I guess that even with any flow it is not quite a simulation of what it would be with no treatment. But maybe it would be close enough to use as an estimate.

Will not work. You cannot control flow, only pressure. If you try to set a low, fixed pressure ( 4 cm is the lowest it will go) you put yourself at risk. It will not give you an untreated AHI baseline.

I want to disagree with the statement that setting the machine at 4cm will "put the user at risk". There are a small number of people who do just fine at very low pressures and 4cm can and does provide therapeutic value in some people.

And that's the real reason you can't really use your APAP to determine that you no longer need PAP therapy at all. It is possible that after the weight loss that you might only need 4-7cm of pressure to fully control your OSA, and sleeping with the machine set at 4cm on a good night might still control almost all of your apneas. In other words you might see a bit of an increase in your treated AHI by using the machine at 4cm, but even with the increase, the machine AHI might be less than 5 and you still might have moderate to severe OSA if you chose to not sleep with the machine at all.

Now there's also this side as well: For many people the amount of pressure that is needed to control their OSA is higher, and maybe significantly higher than 4-7cm. And if your OSA needs something like 12cm or more of pressure, there's just a chance that if you tried to use the machine at 4cm, you might just have an AHI that is almost as bad as your untreated AHI was. But you're just as likely to be very uncomfortable at 4cm simply because you are used to having so much air blowing through your mask.

In the end, there's no reliable way to tell if the weight loss has been enough to properly control your OSA without a formal diagnostic sleep test.

I'll end by saying this: While weight loss can help (or even eliminate) mild OSA in some people, the correlation between OSA and obesity is not a simple one. There are studies that indicate that people with normal weight and OSA are at higher risk of becoming obese than people of normal weight who do not have OSA. So what this means is that in many people, the OSA causes the weight gain rather than the other way round. And if you happened to have undiagnosed OSA before you gained the weight, losing the weight is probably not going to eliminate the OSA or free you from the CPAP.
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#4
(11-08-2016, 02:25 PM)blueelement2016 Wrote: Can I use my APAP to simulate a sleep study, instead of going back to the clinic?

How do you determine from ONLY flow data and algorithmic adjustments that you are asleep and that your sleep is beneficial?

In addition, how do you account for sleep/wake junk and re-compute a more "correct" AHI?

Or, from observing breathing pattern waveforms, how do you determine if the machine is correctly scoring hypopneas, apneas, and RERA information?

There is a reason that sleep labs use a variety of sensors and multi-channel recorders.

Perhaps, you should discuss this matter with your sleep doctor for a more definitive answer and how to estimate the information you need to insure that your therapy is progressing satisfactorily. I would suggest a multi-sensor at home sleep re-test.
"The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane." -- Marcus Aurelius
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#5
First, to get a new baseline, you have to do without your cpap for 3-4 nights. My sister didn't have the money for a new lab test to confirm that she no longer needed a cpap. So, the doc gave her a recording oximeter for 7 nights for her to use WITHOUT the cpap. This confirmed that she no longer had desats and was able to discontinue using the cpap. Now, does this mean that she will NEVER need a cpap again? No. Just doesn't need it now.
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#6
(11-10-2016, 03:19 PM)robysue Wrote: I want to disagree with the statement that setting the machine at 4cm will "put the user at risk". There are a small number of people who do just fine at very low pressures and 4cm can and does provide therapeutic value in some people.

And that's the real reason you can't really use your APAP to determine that you no longer need PAP therapy at all. It is possible that after the weight loss that you might only need 4-7cm of pressure to fully control your OSA, and sleeping with the machine set at 4cm on a good night might still control almost all of your apneas. In other words you might see a bit of an increase in your treated AHI by using the machine at 4cm, but even with the increase, the machine AHI might be less than 5 and you still might have moderate to severe OSA if you chose to not sleep with the machine at all.

Now there's also this side as well: For many people the amount of pressure that is needed to control their OSA is higher, and maybe significantly higher than 4-7cm. And if your OSA needs something like 12cm or more of pressure, there's just a chance that if you tried to use the machine at 4cm, you might just have an AHI that is almost as bad as your untreated AHI was. But you're just as likely to be very uncomfortable at 4cm simply because you are used to having so much air blowing through your mask.

In the end, there's no reliable way to tell if the weight loss has been enough to properly control your OSA without a formal diagnostic sleep test.

I'll end by saying this: While weight loss can help (or even eliminate) mild OSA in some people, the correlation between OSA and obesity is not a simple one. There are studies that indicate that people with normal weight and OSA are at higher risk of becoming obese than people of normal weight who do not have OSA. So what this means is that in many people, the OSA causes the weight gain rather than the other way round. And if you happened to have undiagnosed OSA before you gained the weight, losing the weight is probably not going to eliminate the OSA or free you from the CPAP.


Thanks. I was just flirting with the idea of "how can I self-diagnose to see if what I am doing (weight loss) is making a difference or not." I'm already addicted to reading my data and tweaking my machine Smile I guess I just have that independent, stubborn streak.

And I get that the lifestyle changes I make, might not make a difference at all. Judging by what I've learned about sleep apnea, my symptoms have probably matched up with this diagnosis for years, even back when I weighed 120 pounds. From everything I'm reading, the causation can be very complex. It's definitely not certain if I will ever be able to do anything to get off CPAP. Which is fine.

But I'm definitely the kind that will never stop learning / never stop trying.

Thanks all, for the input!

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