I'm Flying blind: about pressure，the higher the better?

iricoboy · Post by **iricoboy** » Fri Mar 13, 2009 2:30 am

Hi, everyone,

i'm iricoboy from beijing, i got my s8 weeks ago, and i've trying to use it to make me feel better. it worked, but as one said in a thread: u can get better,but you will never get well, i felt just that way!!

i've in this forum for about a week, and since then i've been adjusting my pressure, (before i used autoset mode (4-20,without change), my ahi indicates good figures (always lower than 5)), now i use autoset mode, but with moderated pressure from 10-16, o 12-18, ranges like that, what happens is that the higher pressure i set, i got higher ahi figures, so i wanna ask why this happens (i always think that the higher the pressure set, the airway flow will be more fluent, so i'll get less chance of apnea, is it like what i thought??), leak level is normal, from 0.00-0.12
who can explain this??
many thanks

bdp522 · Post by **bdp522** » Fri Mar 13, 2009 3:42 am

Too high a pressure could cause centrals. What was your titrated pressure? Do you know what your 95% pressure is? You want the pressure to be just enough to splint the airway open, making it too high has no benefit.

Brenda

ozij · Post by **ozij** » Fri Mar 13, 2009 5:19 am

One possibility is Brenda's reason: when your pressure is too high, you brain can get confused by that, and not instruct you to breathe again after you've exhaled. This is called a pressure induced or central apnea.

A second possible reason is that the Resmed behaves differently when the pressure is above 10. Below 10 it will respond to snores, flow limitations, or apnesa. Above 10, if you don't snore, if you don't have flow limitations, but you do have an apnea - the Resmed won't respond to it - because it can't tell if its central or not; it needs the snore and flow limitations to indicate that the apnea is obstructive. Snores and flow limitations are sometimes an inicator your airway may collapse - and the Resmed will respond immediately, because it is forewarned. Once thing settle down, it drops to the mimumu again.
If your minimum pressure is just enough above 10 to cancel the warnings but not enough to avoid apneas entirely - then on a Resmed you're in trouble.

It would be best to take the minimum pressure back to where your results, and how you felt, were best.

O.

iricoboy · Post by **iricoboy** » Fri Mar 13, 2009 6:25 am

bdp522 wrote:Too high a pressure could cause centrals. What was your titrated pressure? Do you know what your 95% pressure is? You want the pressure to be just enough to splint the airway open, making it too high has no benefit.

Brenda

yes,i think u r totally right, i took a nap today in the noon, and just felt an apnea during sleep(i heard the machine is increasing its pressure, motor rotating and noise of rapid airflow, indications it has found an apnea, at that time i'm half asleep, in my conscience i felt my heart is beating fast, telling me i'm out of oxygen again, my nap just took 1 hour and half, but i felt terribe, high blood pressure again, and sleepy all the afternoon, terrible,terrible.. )

i've been using s8 for nearly 3 weeks and it's the first time that i set my minimum pressure at 12,( automode, 12-18, before it was 9/10- 16/17, ranges in which i felt good), and my ahi increases instantly, up to 12.9, and i felt terrible, it has caused a central apnea, i won't set it that high again. many thanks to u

i set my pressure at that high, because i want to lower my ahi down to 1 or 2, as many forum friends are trying to do, is there any way else that make me get that point?? i hope so, but with 9-16 or 10-17, i felt good, what i'm trying is feeling better. jeje

thanks again for your quick instruction!!!

mountainlvr · Post by **mountainlvr** » Fri Mar 13, 2009 6:27 am

Thanks for asking this question! I had the exact same scenario and question! After reading the response, I may bump mine back down to nine, as I saw the same thing happening with the higher pressure and higher AHI. So thankful for this forum!!!!!

Good luck to you, post back what you end up doing and how it works, I'd like to know.

iricoboy · Post by **iricoboy** » Fri Mar 13, 2009 6:55 am

ozij wrote:One possibility is Brenda's reason: when your pressure is too high, you brain can get confused by that, and not instruct you to breathe again after you've exhaled. This is called a pressure induced or central apnea.

A second possible reason is that the Resmed behaves differently when the pressure is above 10. Below 10 it will respond to snores, flow limitations, or apnesa. Above 10, if you don't snore, if you don't have flow limitations, but you do have an apnea - the Resmed won't respond to it - because it can't tell if its central or not; it needs the snore and flow limitations to indicate that the apnea is obstructive. Snores and flow limitations are sometimes an inicator your airway may collapse - and the Resmed will respond immediately, because it is forewarned. Once thing settle down, it drops to the mimumu again.
If your minimum pressure is just enough above 10 to cancel the warnings but not enough to avoid apneas entirely - then on a Resmed you're in trouble.

It would be best to take the minimum pressure back to where your results, and how you felt, were best.

O.

many thanks to u, i've learned a new professional phrase, pressure induced apnea, u r more professional than our beijing doctors!!!
for the second possible reason: i think it has responded, i heard the machine working harder, or maybe the highest pressure 18cm is not enough to save me from that apnea? why can't it tell from central o obstructive? why above 10cm? what will happen if my apnea is central, while my pressure is set from 8-16 ,for example? does it can tell from central o obstructive?

ozij · Post by **ozij** » Fri Mar 13, 2009 7:45 am

iricoboy wrote:<snip>for the second possible reason: i think it has responded, i heard the machine working harder, or maybe the highest pressure 18cm is not enough to save me from that apnea?

Because everything is possible, it would be best to relay the way you felt and the results you had when the minimum pressure was lower. If you snore - the machine may be getting into a vicious cycle, adding pressure evern though too much pressure stops you from breathing.

why can't it tell from central o obstructive?

The machine only know you stop breathing, it can't tell if you stopped because your airway was obstructed, and you need more pressure, or if your airway is open, and your brain is not expecting you to breathe.

why above 10cm?

Because research has shown that when pressure gets too high above 10, more people have pressure induced apneas than they do beneath it. Resmed's way of avoiding pressure induced apneas is to be much more selective about its pressure response above 10 cms. Its called Resmed's A10 algorithm

what will happen if my apnea is central, while my pressure is set from 8-16 ,for example?

Once you cross 10, the machine will respond to an apnea only if it is accompanied by snores or flow limitations. Otherwise, it will ignore it. On the other other hand, if you snore and have flow limitations, the machine will continue raising pressure till it reaches the top of the range. If you don't snore or have flow limitations, above 10, but still have apneas, the machine will do nothing. Beneat 10, it will be treated as an apnea - and pressurr will be raised in response.

does it can tell from central o obstructive?

It can never tell what kind apnea you're having. Since you had such excellent results, and were feeling so well, I would say the chances you had pressure induced apneas below 10 are negligible.
Cental Sleep Apnea - (where your sleeping brain does not instruct you to breathe) - as the main sleep disorder is very rare. You've responded so well to the Resmed APAP that you can be rest assured that you have Obstructive Sleep Apnea
O.

mountainlvr · Post by **mountainlvr** » Fri Mar 13, 2009 1:09 pm

ozij....

This subject has me interested. Thanks for your detailed answers to iricoboy. My machine is a Remstar M Series APAP Auto with C Flex... do you know if mine does the same thing at a range beginning at 10?? It's set right now at 10 - 18, but my SC just told me a few days ago that my apneas were mostly central in my last study. Sure wish they had told me that months ago!

Anyway, my other question is... When the machine jacks up the pressure to interrupt an event, does it go back to the minimum pressure when the event is over, or does it stay at the new, higher pressure??

Thanks so much! I don't mean to hijack iricoboys thread!!!

Wulfman · Post by **Wulfman** » Fri Mar 13, 2009 4:22 pm

mountainlvr wrote:ozij....

This subject has me interested. Thanks for your detailed answers to iricoboy. My machine is a Remstar M Series APAP Auto with C Flex... do you know if mine does the same thing at a range beginning at 10?? It's set right now at 10 - 18, but my SC just told me a few days ago that my apneas were mostly central in my last study. Sure wish they had told me that months ago!

Anyway, my other question is... When the machine jacks up the pressure to interrupt an event, does it go back to the minimum pressure when the event is over, or does it stay at the new, higher pressure??

Thanks so much! I don't mean to hijack iricoboys thread!!!

Here's some reading material from the Respironics site about how the REMstar Autos respond to events.

Den

From the Event Responses section:

Flow Limitation response:
While in Ptherapy mode, if flow limitation occurs during the last 4 breaths or over several minutes, the algorithm begins a Popt search

Vibratory snoring:
In Ptherapy mode, if 3 vibratory snores are detected within 1 minute, with less than 30 seconds between snores, the algorithm increases pressure by 1 cmH2O over 15 seconds.
Re-initiate Ptherapy for 5 minutes.
Further vibratory snoring-related increases are limited to 1 cmH2O per minute.

Apnea/Hypopnea:
While in Ptherapy mode, if 2 apneas/hypopneas are detected within 3 minutes, the algorithm increases pressure by 1 cmH2O
Re-initiate Ptherapy for 5 minutes

In Popt search mode, if 2 apneas/hypopneas are detected within 3 minutes, the algorithm increases pressure by 1 cmH2O.
Re-initiate Ptherapy for 5 minutes.

Non-Responsive:
Above 8 cmH2O pressure, the pressure increase for sustained apneas/hypopneas is limited to 3 cmH2O above the pressure setting at the onset of the apnea/hypopnea sequence.
The pressure setting at the onset of the sequence is called the "Onset Pressure".
The pressure 3 cmH2O above the "Onset Pressure" is called the "NRAH Threshold".
"NRAH" is an acronym for "Non-Responsive Apnea/Hypopnea".

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Exception Condition:
The persistence of large leaks, particularly when the patient's breath have small tidal volumes, could potentially induce false apnea and hypopnea detection. Therefore the REMstar Auto monitors the patient's flow over several minutes.
The patient's flow is compared to "expected leak". "Expected leak" is a value that has been determined through testing of various mask and tubing combinations.

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Above 8 cmH2O pressure, the pressure increase for sustained apneas/hypopneas is limited to 3 cmH2O above the pressure setting at the onset of the apnea/hypopnea sequence. The pressure setting at the onset of the sequence is called the "Onset Pressure." The pressure 3 cmH2O above the "Onset Pressure" is called the "NRAH Threshold." "NRAH" is an acronym for "Non-Responsive Apnea/Hypopnea."

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When the device encounters a non-responsive apnea or hypopnea, it will decrease pressure by 2 cmH2O and hold the pressure for 15 minutes. During this 15-minute "NRAH-hold" period, the pressure will be changed only in response to detection of a sequence of vibratory snore events. The reason for this increase in pressure followed by a decrease in pressure when an apnea/hypopnea is not responsive is to allow the device to respond appropriately to an event that is not treatable by increases in pressure, such as a central apnea.

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After seeing two Hypopneas, the algorithm increases the pressure by 1 cmH2O, and the Onset Pressure resets to this new pressure level.

However, the Onset Pressure can not be raised above 12 cmH2O by a sustained string of Hypopnea-only events. This does not imply that the Onset Pressure value can not be set above 12 cmH2O. It only states that the Onset Pressure can not be <b>RESET</b> above 12 cmH2O due to a string of Hypopnea-only events. The maximum NRAH Threshold due to a sustained string of Hypopnea-only events will be 3 cmH2O above 12 cmH2

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ozij · Post by **ozij** » Fri Mar 13, 2009 8:47 pm

mountainlvr wrote:ozij....

This subject has me interested. Thanks for your detailed answers to iricoboy. My machine is a Remstar M Series APAP Auto with C Flex... do you know if mine does the same thing at a range beginning at 10??

Yes I do, and the answer, as you can see from Den's quote is "No". Different machines have different ways of attempting to avoid pressure induced apneas. The Respironics technique is very different from the Resmed.

Anyway, my other question is... When the machine jacks up the pressure to interrupt an event, does it go back to the minimum pressure when the event is over, or does it stay at the new, higher pressure??

The machines don't really jack up the pressure to interupt a single apnea. They jack up the pressure when they figure an apnea (or other breathing disturbance) has happened - and they keep it higher for while, then they go back down - again, Den's quote gives you the numeric details.

O.

iricoboy · Post by **iricoboy** » Sat Mar 14, 2009 5:29 am

ozij wrote:
iricoboy wrote:<snip>for the second possible reason: i think it has responded, i heard the machine working harder, or maybe the highest pressure 18cm is not enough to save me from that apnea?
Because everything is possible, it would be best to relay the way you felt and the results you had when the minimum pressure was lower. If you snore - the machine may be getting into a vicious cycle, adding pressure evern though too much pressure stops you from breathing.
why can't it tell from central o obstructive?
The machine only know you stop breathing, it can't tell if you stopped because your airway was obstructed, and you need more pressure, or if your airway is open, and your brain is not expecting you to breathe.
why above 10cm?
Because research has shown that when pressure gets too high above 10, more people have pressure induced apneas than they do beneath it. Resmed's way of avoiding pressure induced apneas is to be much more selective about its pressure response above 10 cms. Its called Resmed's A10 algorithm
what will happen if my apnea is central, while my pressure is set from 8-16 ,for example?
Once you cross 10, the machine will respond to an apnea only if it is accompanied by snores or flow limitations. Otherwise, it will ignore it. On the other other hand, if you snore and have flow limitations, the machine will continue raising pressure till it reaches the top of the range. If you don't snore or have flow limitations, above 10, but still have apneas, the machine will do nothing. Beneat 10, it will be treated as an apnea - and pressurr will be raised in response.
does it can tell from central o obstructive?
It can never tell what kind apnea you're having. Since you had such excellent results, and were feeling so well, I would say the chances you had pressure induced apneas below 10 are negligible.
Cental Sleep Apnea - (where your sleeping brain does not instruct you to breathe) - as the main sleep disorder is very rare. You've responded so well to the Resmed APAP that you can be rest assured that you have Obstructive Sleep Apnea
O.

i'm full of admiration for your professional knowledge, i think u r my saver, thank you very much. let's keep in touch, u r really a master of apap

ozij · Post by **ozij** » Sat Mar 14, 2009 5:59 am

Thoser are very kind words, iricoboy. I'm far from being the only expert on this board - I came here knowing nothing. But lots an lots of forum reading - and many kind people on this forum have taught me. They shared their knowledge, and also shared links to their sources.

If you search in the company sites, or look at their patents (http://www.google.com/patents) you learn a lot.

O.

roster · Post by **roster** » Sat Mar 14, 2009 6:38 am

Iricoboy,

Ozij is giving you some great information and advice.

I would like to make you aware of "positional sleep apnea" (PSA). Maybe 40% or more of patients have PSA.

PSA means the apnea is much worse in one sleeping position (on the back) compared to other sleeping positions. For example, my sleep apnea is very severe when I am sleeping on my back.

For people with PSA, the sleeping position can have a big effect on CPAP pressure requirements. For example, I have been titrated in a sleep lab and at home have confirmed my pressure requirements for different positions. On my back I require a pressure of 19 cm (Yow!). On my side or stomach, a pressure of 8.5 cm is sufficient. So I have some devices and train myself to sleep only on side or stomach and use pressure of 8.5 cm.

You may want to make some observations about the possibility of PSA in your case.

BTW, many of the sleep labs and doctors in the U.S. are also of low quality. This sleep business is in its infancy and will take some time to develop effective and efficient diagnosis and treatment. Big changes are coming.

Good luck,

I'm Flying blind: about pressure，the higher the better?

I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?

Re: I'm Flying blind: about pressure，the higher the better?