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AHI higher on CPAP than without.

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wandafeb02 +0 points · 14 days ago Original Poster

My study report showed 8 ahi events per hour. On my CPAP which is auto adjust, my events average 15 per hour. My pressure level is set at 4 minimum. We've tried maximum pressure of 20, 16, 15, 14, and 13. Has anyone else had this problem?

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Sierra +0 points · 14 days ago Sleep Innovater

It did not happen to me in exactly that way. My AHI at diagnosis was about 37. It was mostly obstructive apnea but there was a small component that was central apnea. What happened to me on CPAP treatment was that the obstructive apnea went way down, but unfortunately the central apnea increased. CPAP pressure treats obstructive apnea because the pressure opens the airway. With central apnea the airway is already open, but the person simply stops breathing. The reasons for stopping breathing are complex, but the increased pressure can upset the oxygen and carbon dioxide balance that regulates breathing automatically. The upset can increase the frequency of central apnea. In about 3/4 of people that have this treatment onset of central apnea, the increase goes away in 6-8 weeks. It unfortunately did not for me.

So, the first thing you need to know is the breakdown of the apnea AHI you are now having. What portion is obstructive apnea, what is central apnea, and how much is hypopnea. You may be able to get that from your machine. What make and model do you have? However the best way to get more information is to display your data in a software called SleepyHead or OSCAR. You need a PC or Mac with a SD card reader, and a machine that is compatible with this software. Most ResMed and DreamStation machines are compatible.

The solution is most likely to be a reduction in pressure to a trade off point where obstructive apnea is not too high, and central apnea is not too high either. Also when you find that pressure, you may be better off with a single fixed pressure, rather than an auto range of pressure. However finding the ideal pressure is easier with the machine in auto. Using SleepyHead you can tell when obstructive events are happening, and when central events are happening and what the pressure is at each event.

Hope that helps some,

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wandafeb02 +0 points · 13 days ago Original Poster

Thank you so much! I don't have a PC or MAC but will check to see if my respriratory therapist can find out about the central apnea possibility. If not, may just have to check into getting a PC. I very much appreciate your help.

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Sierra +0 points · 13 days ago Sleep Innovater

If you have a ResMed machine there is another option to get a little more information. If you hold the Home key (near the bottom) down and at the same time hold down the round set knob for about 5 seconds, it wills switch into the Clinical Menu. Then when you rotate the Set knob you can scroll down to a menu item called "Essentials". The default position is "On", but if you press the round knob and go into it you can set it to "Plus". Then exit out to the User Menu with the Home key. With Essentials set to Plus you will get a more detailed Sleep Report from the User Menu. Near the bottom you can select the time interval, and then get a breakdown of the type of AHI events you are having. It is not nearly as informative as SleepyHead, but it is better than nothing. The key is determining how much of the AHI is central apnea.

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wandafeb02 +0 points · 11 days ago Original Poster

I will try that although my RT said the reports don't show Central Apnea. I noticed that your minimum pressure is set at 12. Mine is set at 4. I wonder if the minimum can be a factor. I so appreciate your help. Thank you.

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bonjour +0 points · 11 days ago Sleep Commentator

Many find 4 to be too low. I'd suggest setting Flex/EPR to On full-time and your min pressure to 6 and see if that feels better. This will leave your therapeutic pressure either the same or close to it depending on the brand of your machine.

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Sierra +0 points · 11 days ago Sleep Innovater

A minimum pressure of 4 cm in my opinion is almost always too low, unless you are getting central events at a very low pressure. If there is a normal setup for a ResMed AutoSense machine, I would suggest a minimum of 7 cm, with the AutoRamp turned on, EPR turned on and set at 3 cm, and EPR set for Ramp Only. This will maximize comfort for going to sleep.

Raising the minimum pressure can be effective for reducing AHI if it is obstructive in nature. A high minimum pressure will start preventing obstructive events earlier without waiting for them to occur first, and then letting the machine increase pressure.

Hope that helps some,

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sleeptech +0 points · 13 days ago Sleep Enthusiast

What kind of study did you have? Home-based studies often over estimate AHI, and if this is what happened in your case you may not have OSA at all. That could explain why CPAP has caused an increase in events.

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wandafeb02 +0 points · 11 days ago Original Poster

That's very interesting I did have a in-home study and it registered 8 per hour. The machine keeps me from snoring which is nice for my husband 😀. The RT says my reports don't show Central Apnea. Thank you so much for your input.

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Sierra +0 points · 11 days ago Sleep Innovater

Depending on how the home study is done it can also UNDERestimate the AHI. Sometimes it includes all time in bed instead of just sleeping time. In any case an AHI of 15 with the machine is too high and needs attention. However it is critical to know how much of that AHI of 15 is obstructive and how much is central.

Edit: I said it backward. If they use all time in bed for the denominator it makes the AHI appear lower.

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sleeptech +0 points · 8 days ago Sleep Enthusiast

I have seen home studies both under- and overestimate AHI, in some cases massively so, but overestimation is far more common in my experience. Home studies use fewer sensors and therefore measure fewer things which would otherwise stop an event from being counted as an apnoea or hypopnoea. Also, as you mentioned, if they cannot tell when you are asleep or awake they will often count events that happen in wake which would otherwise be discounted, especially after sleep onset. Wake respiration is usually much more irregular than health sleep respiration.

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Frank01945 +0 points · 10 days ago

Great forum, thanks. My home study showed AHI of 31, just in the "severe" range. Over 10 months, using SleepyHead for data, I was never able to get my average AHI below 10, trying every mask and a range of settings in the process. I just had surgery to correct my deviated septum, and can now breathe thru my nose, for the first time. But this has thrown my CPAP treatment off. Where I used to get my best results with max pressure set to 18 (I would have gone to 20 but could not stop mask leaks), post surgery it was difficult for me to exhale, even at 14. I tried using EPR = 1, but started getting irregular heart beats, indicating distress. My PCP told me to stop using CPAP until a new, in lab sleep test is done in 6 weeks. I have had to figure out things on my own, with help from a friend in the US, and from a friend in Amsterdam. My Pulmonologist was not helpful, and I will get a new one in two weeks. It's been almost a year! Thanks for listening.

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Sierra +0 points · 10 days ago Sleep Innovater

What is your ratio of central apnea to obstructive apnea? Pressure most often is not helpful in reducing central apnea.

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bonjour +0 points · 9 days ago Sleep Commentator

With pressure at 18, consider a BiLevel such as the VAuto which can provide a much greater difference between Inhale and exhale pressures which should make it easier to exhale. With your CPAP, setting EPR to 3 should help with exhaling but I do not know what to make of your irregular heartbeats. Since your situation is more complex than normal I'd suggest posting daily SleepyHead charts to assist others in advising you. Events, Flow Rates, Flow Limits, Pressure, Leaks, and Snores

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sleeptech +0 points · 8 days ago Sleep Enthusiast

It is risky to use BiPAP without it being set up by an experienced tech and with an in-lab study, especially if there is a significant difference between the IPAP and EPAP pressures. This can hyperventilate the patient and induce hypocapnia and Cheyne-Stokes respiration.

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bonjour +0 points · 7 days ago Sleep Commentator

I am fully aware that one doesn't apply high PS on a whim. I've never, outside of an ASV, suggested a PS higher than a 6, and I've never started there.

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Frank01945 +0 points · 8 days ago

thanks. I have not been using mask, awaiting titration study in 6 weeks. But I am considering trying the mask again at low pressure - like 12 and no EPR. If that does not work, I will have to wait for study.

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