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[CPAP] flow limit,csas,aircurve asv
#1
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flow limit,csas,aircurve asv
Hi

I have been using a CPAP machine for more than a year. The first machine I used was an airsense 10 autoset. During using this machine, my AHI index was generally less than 1. However, I still felt tired after waking up. The pressure set at the time was 8-20H2O, EPR3, and the ramp time was 45min. In the last month, I changed the aircurve 10 asv. The current problem is the CSAS and obvious flow limitation caused by the machine. What is the reason for my airflow limitation? Whenever CSAS occurs, the machine stops and I wake up. What should I do next, can anyone help me? Thank you very much.


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#2
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RE: flow limit,csas,aircurve asv
(05-20-2020, 04:28 AM)zhaoyi9205 Wrote: Hi

I have been using a CPAP machine for more than a year. The first machine I used was an airsense 10 autoset. During using this machine, my AHI index was generally less than 1. However, I still felt tired after waking up. The pressure set at the time was 8-20H2O, EPR3, and the ramp time was 45min. In the last month, I changed the aircurve 10 asv. The current problem is the CSAS and obvious flow limitation caused by the machine. What is the reason for my airflow limitation? Whenever CSAS occurs, the machine stops and I wake up. What should I do next, can anyone help me? Thank you very much.
I am not an American, and the posts I post are all translated using translation software, and may have grammatical problems. Please excuse me.
Considering that PSmin may be set too large, which may lead to central apnea. I lowered the PSmin value to 3.4 and increased the EPAP to 8, I didn't notice any obvious CSAS during sleep, the number of waking times decreased, and the AHI value decreased significantly. I still have problems that bother me when I wake up and I feel tired and feel short of breath. OSCAR can see obvious airflow restrictions. Who can tell me what causes airflow restrictions In addition, I added that I have no underlying diseases, I haven't taken any medicines in my daily life, and my weight is basically normal. I have a history of snoring for more than 10 years. I did sleep monitoring last year. The AHI value was around 15, mainly with Hypopnea. I only used CPAP machines in the last year.
Thanks


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#3
RE: flow limit,csas,aircurve asv
I'm not really certain, but I'd guess it may have something to do with the high leak rate? I believe ASV, even more so than regular PAP modes, really needs leaks to be controlled to work correctly.

Also, I suggest turning off ramp.

What's CSAS?
Caveats: I'm just a patient, with no medical training. And my first experience with xPAP was fairly recent. So I'm somewhere along the path of a steep learning curve.
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#4
RE: flow limit,csas,aircurve asv
Nevermind; got confused.
Caveats: I'm just a patient, with no medical training. And my first experience with xPAP was fairly recent. So I'm somewhere along the path of a steep learning curve.
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#5
RE: flow limit,csas,aircurve asv
Zhaoy, welcome to Apnea Board. When I saw your first charts it was immediately apparent the settings were way off with too much PS min and a low EPAP min, based on your prior CPAP experience. This was made worse with the use of Ramp and a lot of leaks. Your revised settings of EPAP min 8.0, PS min 3.4, PS Max 15.0 are far more appropriate, and seem to be achieving good results.

I recommend that you consider changing PS min to 3.0. The machine is active in providing relatively high pressure support and I don't know why it is so high. Your results on CPAP were very good and I think it might be helpful to see some of those results. Since your AHI was low with CPAP, I suspect you only needed to have more pressure support to resolve flow limitation, but with ASV it appears pressure support may be needed to mitigate central apnea caused by the increased ventilation. Your tidal volume is quite high at 750 mL and is offset by a low respiration rate of only 10.6 bpm. As we explore your therapy, we may want to see some graphs with flow rate, Pressure, tidal volume and respiration rate so we can see if the variations are related to pressure support.

We tend to disregard flow limitations with ASV because when breaths are initiated by the machine, they become flow limited without spontaneous effort. This is very common because the machine is inflating your lungs rather than your muscular effort, and this results in a flatter or more flow-limited ispiratory peak.
Sleeprider
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#6
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RE: flow limit,csas,aircurve asv
Sorry, my posts are all translated into English using translation software, so there may be grammatical errors.
I used CSAS instead of central apnea, which is my mistake.
There was indeed a lot of air leaks on May 19th. On May 20th(see the attachment on the second floor), I adjusted the minPS and turned off the ramp time. This night's sleep feeling is not much different from the past, there is basically no air leakage, and no central apnea. The AHI index is 0.1, but the Flow limit is obvious.
This phenomenon is the same as when I used Airsense 10 autoset. The AHI index is less than 1, but the Flow limit is more obvious. I do n’t wake up with a refreshing feeling, and I still feel tired.
The current problem is mainly airflow limitation, what are the reasons for the original airflow limitation, and what are the countermeasures.
Many thanks.
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#7
RE: flow limit,csas,aircurve asv
(05-21-2020, 08:19 AM)Sleeprider Wrote: Zhaoy, welcome to Apnea Board.  When I saw your first charts it was immediately apparent the settings were way off with too much PS min and a low EPAP min, based on your prior CPAP experience. This was made worse with the use of Ramp and a lot of leaks. Your revised settings of EPAP min 8.0, PS min 3.4, PS Max 15.0 are far more appropriate, and seem to be achieving good results.

I recommend that you consider changing PS min to 3.0.  The machine is active in providing relatively high pressure support and I don't know why it is so high.  Your results on CPAP were very good and I think it might be helpful to see some of those results.  Since your AHI was low with CPAP, I suspect you only needed to have more pressure support to resolve flow limitation, but with ASV it appears pressure support may be needed to mitigate central apnea caused by the increased ventilation.  Your tidal volume is quite high at 750 mL and is offset by a low respiration rate of only 10.6 bpm.  As we explore your therapy, we may want to see some graphs with flow rate, Pressure, tidal volume and respiration rate so we can see if the variations are related to pressure support.

We tend to disregard flow limitations with ASV because when breaths are initiated by the machine, they become flow limited without spontaneous effort. This is very common because the machine is inflating your lungs rather than your muscular effort, and this results in a flatter or more flow-limited ispiratory peak.

Thank you very much. Your answer helped me a lot.

This is my Oscar chart, including airflow rate, pressure, tidal volume, etc. 
Don't know if you need to zoom in on the picture.


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#8
RE: flow limit,csas,aircurve asv
The new chart is very helpful because it shows a direct relationship of pressure support to tidal volume, accompanied by an inverse relationship to respiration rate. When pressure support increases, tidal volume increases and respiration rate decreases. The end result is that minute vent (Liters of air respired in one minute) remains constant. Your ASV is designed to maintain minute vent, and that goal is being achieved.

We need to tame the reactions of the ASV that results in distortions of your tidal volume, and suppression of respiration rate to determine if you still maintain a spontaneous rate of respiration in breaths per minute. The objective is to make your respiratory volume and rate more consistent. To do this, keep the machine in ASVauto mode without changing the EPAP min or EPAP max settings. I want you to contnue with PS min 3.4 and reduce PS max to 5.0. These settings are as close as we can get to a simple bilevel like the Vauto, and assumes you do not have central apnea based on your CPAP experience. This will give you a bilevel therapy with PS from 3.4 to 5.0 which should not disrupt your tidal volume as much. If you find these settings result in CA events, you can return PS max to 15, however I would like to see the results of the reduced PS max in a chart like you posted above.
Sleeprider
Apnea Board Moderator
www.ApneaBoard.com

____________________________________________
Download OSCAR Software
Soft Cervical Collar
Optimizing Therapy
Organize your OSCAR Charts
Attaching Files
Mask Primer
How To Deal With Equipment Supplier


INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#9
RE: flow limit,csas,aircurve asv
I too would like to see the result of reducing PS as Sleeprider suggests. It may be helpful as well to view a PS range of 3-5, but hold off on that. Let us see if reducing PS Max has the result expected.

If CA return, maybe taking PS Max up but not back to 15 may work, something like 10. That may still cap the PS from modifying tidal volume as much.
Dave

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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEBSITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#10
RE: flow limit,csas,aircurve asv
(05-22-2020, 07:51 AM)Sleeprider Wrote: I want you to contnue with PS min 3.4 and reduce PS max to 5.0.  

Is that possible? My understanding is the Resmed ASV modes enforce a min delta of 5 between PS min and max?
Caveats: I'm just a patient, with no medical training. And my first experience with xPAP was fairly recent. So I'm somewhere along the path of a steep learning curve.
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