Runaway pressure increase with resmed auto S8

[JimW]

I haven't connected the humidifier yet. Didn't take it with when I first got the machine for a test while traveling and I really don't like the warm air feel in the summer. But perhaps I should because last night, I woke with a very dry mouth - so dry that I was dreaming that it was hard to talk.

Unless you live in a very humid area, you will likely, at least eventually, need the humidifier. Your very dry mouth may indicate mouth leaking, which would negate any treatment benefits while it is occurring. You may want to do a search for "mouth leak".

[GoofyUT]

[quote="dsm"]This post follows on Chuck's comments re why the Remstar Classic machine suited him better than a Resmed S8 machine. Chuck, please feel free to comment on or to correct any of my comments below. What I am posting below is just my own impressions & observations.

When Chuck 1st made this comment re the difference between Remstar & S8 Vantage (IIRC back in 2006) I wondered what he could be meaning. In one sense a cpap machine is an air pump & how could a simple air pump be so different for one person vs another. I thought masks yes, but how could the cpap unit itself vary so much that one brand is going to pump air better than another ?.

The main challenge I had was trying to figure out in mechanical/technical terms what Chuck was saying about the Resmed being 'aggressive' & the Remstar being 'softer'. I asked myself at the time "how can air flow be 'aggressive' or 'soft'". What was he really saying.

I had started out my cpap life on a Remstar classic tank & have in many many posts sung its praises as one of Respironics great products. I also have tried the Resmed S6, the S7 Elite (cpap) the S7 Spirit (auto) S8 Escape (cpap) and S8 Vantage (Auto) as well as several Vpap III Bilevels. The Vpap IIIs have exactly the same blower assembly as the S7 models whereas the S8 has a newly designed blower.

The more I tried different machines, the more I believe I began to understand what Chuck was conveying re aggressive vs soft.

Apart from the Auto algorithms that drive the pressure raising aspect of the Auto, there are other elments that can and do make a difference to the comfort for one cpap user versus another. When it comes to debating algorithms, the debates can get quite 'religious' and I am not into going down that theme in this thread (not without my best armour on )

What can and does make a noticable difference between one brand and even models within brands are things like how fast the machine's blower can accelerate & how quickly the motor can be slowed combined with how quickly the sensors can report the changes (pressure & airflow) & respond to them. What seemed to come through to me is that with the Resmed models the blower could accelerate fast but the pressure sensing circuits in the machine seemed to lag the motor enough that the pressure would 'overshoot' and in time this effect struck me as what Chuck was describing as 'aggressive'.

The Remstar classic has a biggish motor in it. The newer M series motor is tiny by comparison. The Remstar classic seemed to be a better tuned unit when it came to motor performance and sensor synchronisation. This gave what I believe Chuck calls the softer feel of the Remstar classic.

On the algorith side of the debate, the speed with which the various machines, *increase CMS* when events are detected is so slow over all that I can't really see that being a problem to anyone. If anyone does find that a problem they shouldn't be on an Auto as future Autos may do it even faster. The C-Flex debate makes far more sense in that C-Flex offers great comfort to some people but causes some problems for others (aerophagia, breath stacking etc:). C-Flex has everything to do with how an individual person reacts to breath by breath changes occuring when transitioning from inhale to exhale.

The Resmed machines do seem to raise pressure a bit quicker in response to obstructions and snore vibrations. Am satisfied from conducting various tests re this. But that is a minor issue compared to how well a particular machine transitions from inhale to exhale. I am convinced that this is the point where people vary greatest & thus react most to a particular model of machine.

One issue I had with the Resmed S7 blowers (& thus Vpap IIIs as well) is the whine they make as they change speed in response to breathing in and out. Interestingly, Respironics now have this problem with their M series machines. The Bipaps & Classic models don't behave that way.

So in summary, am saying that there are many factors that can make one brand of machine seem better than another and then this can vary between models within brands. I am now of the opinion that getting the 'perfect' cpap machine has little to do with 'brands' but a lot to do with individual designs & combinations & that finding whats best for oneself is still a hit and miss exercise.

Hppy searching (for that perfect machine )

DSM

[Snoredog]

well barbara after you get through reading all those unrelated smoke and mirrors from frick and frack,

do a search for "Sleep onset centrals". Here is a link, read SWS's explanation of them, you can also Google search for them.

viewtopic.php?t=1301

Bottom line is you can use that Settling feature to avoid those at the onset of sleep. I suggest setting it to maximum 30 minutes, you have no idea how long they are lasting and can hit the button just like Ramp as many times as you wish and it will reset the timer for another 30 minutes.

That will get you past the sleep onset events, but if you have post-arousal centrals as well which sometimes occur after an obstructive apnea you will have the exact same problem all over again if they are beyond that period like when you are asleep.

The S8's only "avoidance" and/or differentiation of those events is either by use of Settling (i.e. doing nothing until time period elapses) and/or use of its patented A-10 algorithm.

But the A-10 algorithm is a dinosaur compared to technologies found other machines. They are limited on what they can now do by their own patent and patents held by others such as Respironics, Puritan Bennett and others.

The 420e uses its main sensor and cardiac oscillations to avoid those same events. It also has adjustable parameters you can set to avoid those situations.

So the S8 is still using their old primitive A-10 function set to avoid those central events, that function set basically says it won't respond to any apnea at or above 10 cm pressure, that is all it has for avoidance or differentiation. It will still respond to Flow limitation and snore with the A-10 limit active. Now what you have to cross your fingers and hope for is you don't start snoring, because that can cause pressure to increase and with the increased pressure from snore it can trigger more of those central events and you have a runaway machine.

It is not real hard to figure out, all you have to understand (from the machine's perspective) is the difference in flow from a obstructive apnea and a central one lasting the same duration. Then it is pretty easy to grasp.

You should also drag out your original PSG and look for those onset events, look for CA or MA events for a starting place. You might also check with the Sleep lab, they will tell you if they were present, but they should be in your report. But onset centrals are generally not scored (depends on the tech it seems).

Many medical disturbances cause insomnia, such as asthma and its treatment, pain, neurologic degenerative disorders, allergies. Also included here are the restless legs syndrome (RLS) and periodic limb movements. To evaluate RLS, ask whether a patient's legs are comfortable when trying to fall asleep. If the patient reports disagreeable but not painful paresthesias, "creepy-crawly" feelings in the legs (and occasionally in the arms), disappearance of these feelings when the legs are moved (e.g., walking), and a circadian rhythm to these paresthesias (worst at night), then restless legs is a likely diagnosis (43). Also included here are sleep onset central apneas, often associated with hyperventilation before sleep in anxious patients, then resulting in central apneas when the patient falls asleep and respiration becomes automatic. These sleep onset centrals often awaken the sleeper. There is then frequent alternating between wake with hyperventilation and sleep with central apneas causing arousal, until more solid sleep is established.

You can find the original text here:
http://www.talkaboutsleep.com/sleep-dis ... manual.htm

and here are how other people describe them:
http://www.apneasupport.org/about6965.html

[ozij]

And here:

http://www.resmed.com/en-us/products/fl ... u=products

The AutoSet Algorithm

The efficacy of the AutoSet algorithm is due to its ability to increase pressure in response to the severity of the three parameters: (flow limitation, snore, and apnea):

*The greater the flow limitation, the more pressure delivered
*The louder the snoring, the more pressure delivered
*The longer the apnea, the greater the increase in pressure

By responding to these three separate parameters, AutoSet devices effectively normalize sleep while delivering a mean pressure typically 37% lower than fixed pressure therapy.1

Upper Airway Status and Flow Curves

The most effective way to assess flow limitation is through analyzing the shape of the inspiratory flow-time curve, as shown in the diagrams below.

       
A rounded inspiratory flow contour is the monitoring event that best predicts upper airway patency and a transition to deeper sleep stages without arousals. Studies recommend that this inspiratory flow contour characteristic be routinely used to achieve an optimal pressure level and is preferable to responding to apneas and hypopneas directly. 2,3

All well and fine, and long as your normal non-obstructed breathing has this rounded flow contour characterisitic. If it doesn't and it looks more like the one of the right -- the machine will never consider your pressure low enough, and will be fighting you all night long, trying to normalize what it consider abnormal, even though it is normal for you.

Beyond theorising - base your decicions on how you feel after sleeping with a machine.

O.

[dsm]

Chuck

Am interested in how you can speak of waveform when using a cpap is a matter of breathing which is (as you rightly say, how you feel). I can't 'see' the waveform on my Resmed or PB or Remstar ?.

Also, if you are asleep and have an event how can you tell that the speed of the response to the event did anything ? If you are asleep, at best you become aware of something when aroused, but well after the event. There has to be a better explanation.

In regard to speed of response to events - it seems to me that the Vpap Adapt is the ultimate in responding to an event & yet everyone who has one says how effective it is ? In fact they really are the pattern of the future. The Bipap SV is another example.

What I am saying is I can't understand how the speed of response to an OSA event can be in any way dramatic (when it occurs comparatively slowly (taking seconds)) and while someone is asleep, that they can say it was aggressive or soft.

I can understand how people can report obvious symptoms such as "with C-Flex on 3 I seem to get greater aerophagia" or "with c-Flex my breaths seem to get out of sync" or "with straight cpap I struggle to breathe out at 15 cms" or "on my bilevel the pressure rises too fast after I breathe out" or "on my bilevel the machine seems to cut me off before I have finished breathing" etc: etc:.

I can understand how the transition between breathing in and breathing out whether on plain cpap or BiLevel, can have all sorts of side effects, as explained earlier. But, can't see how the speed of response to an OSA event, allowing for how slow all Autos currently respond, can be identified in the way you are describing it. Can you clarify further ?

Thanks

DSM

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): resmed, bipap, C-FLEX, CPAP, aerophagia

[ozij]

Chuck
<snip...>
but am interested in how you can speak of waveform when using a cpap is a matter of breathing. I can't 'see' the waveform on my Resmed or PB or Remstar ?. What waveform can there be with an air pump ?.

Also, if you are asleep and have an event how can you tell that the speed of the response to the event did anything ? If you are asleep, at best you become aware of something when aroused, but well after the event. There has to be a better explanation.

It's been demonstrated more than once, at least in the "iron lung" studies that ResMed autotitrating machines increase pressure much more sharply in the face of a scored event (though not DURING a scored event, when they are designed to do NOTHING, presumably to avoid centrals and not arouse you) than do the Respironics machines which increase pressure on a more gradual, step-wise basis.

With blowers of the same mechanical capabilities, when a machine increases pressure, and how sharply the pressure is decreased or increased are software depenedent.

If you put air pressure on the Y axis of the graph, and time on the X axis you will get a graph of the machine's response over time. Add different events and you'll get different forms.

For an event - e.g. flow limitation - imagine one machine (same mechanical properties) is instructed to raise pressure by (this is a made up example!) 0.2cms every two seconds, while the other is instructed to raise pressure by 0.5 cms every two seconds till the flow limitation disappears. Assume than in both cases, the flow limitation needs an addition of 1 cm pressure to disappear. Both machines will clear the flow limitation, the second one's graph will be steeper the flow limitation will disappear in the time it takes to raise the pressur in .5 cm. increments: that is 4 secs. The other machine will need 10 seconds to arrive at the same added pressure - it's graph will not so steep, the changes not so abrupt.

For some people, the more abrupt change in pressure will be bothersome.

O.

[dsm]

Chuck
<snip...>
but am interested in how you can speak of waveform when using a cpap is a matter of breathing. I can't 'see' the waveform on my Resmed or PB or Remstar ?. What waveform can there be with an air pump ?.

Also, if you are asleep and have an event how can you tell that the speed of the response to the event did anything ? If you are asleep, at best you become aware of something when aroused, but well after the event. There has to be a better explanation.

It's been demonstrated more than once, at least in the "iron lung" studies that ResMed autotitrating machines increase pressure much more sharply in the face of a scored event (though not DURING a scored event, when they are designed to do NOTHING, presumably to avoid centrals and not arouse you) than do the Respironics machines which increase pressure on a more gradual, step-wise basis.

With blowers of the same mechanical capabilities, when a machine increases pressure, and how sharply the pressure is decreased or increased are software depenedent.

If you put air pressure on the Y axis of the graph, and time on the X axis you will get a graph of the machine's response over time. Add different events and you'll get different forms.

For an event - e.g. flow limitation - imagine one machine (same mechanical properties) is instructed to raise pressure by (this is a made up example!) 0.2cms every two seconds, while the other is instructed to raise pressure by 0.5 cms every two seconds till the flow limitation disappears. Assume than in both cases, the flow limitation needs an addition of 1 cm pressure to disappear. Both machines will clear the flow limitation, the second one's graph will be steeper the flow limitation will disappear in the time it takes to raise the pressur in .5 cm. increments: that is 4 secs. The other machine will need 10 seconds to arrive at the same added pressure - it's graph will not so steep, the changes not so abrupt.

For some people, the more abrupt change in pressure will be bothersome.

O.

[GoofyUT]

Chuck
<snip...>
but am interested in how you can speak of waveform when using a cpap is a matter of breathing. I can't 'see' the waveform on my Resmed or PB or Remstar ?. What waveform can there be with an air pump ?.

Also, if you are asleep and have an event how can you tell that the speed of the response to the event did anything ? If you are asleep, at best you become aware of something when aroused, but well after the event. There has to be a better explanation.

It's been demonstrated more than once, at least in the "iron lung" studies that ResMed autotitrating machines increase pressure much more sharply in the face of a scored event (though not DURING a scored event, when they are designed to do NOTHING, presumably to avoid centrals and not arouse you) than do the Respironics machines which increase pressure on a more gradual, step-wise basis.

With blowers of the same mechanical capabilities, when a machine increases pressure, and how sharply the pressure is decreased or increased are software depenedent.

If you put air pressure on the Y axis of the graph, and time on the X axis you will get a graph of the machine's response over time. Add different events and you'll get different forms.

For an event - e.g. flow limitation - imagine one machine (same mechanical properties) is instructed to raise pressure by (this is a made up example!) 0.2cms every two seconds, while the other is instructed to raise pressure by 0.5 cms every two seconds till the flow limitation disappears. Assume than in both cases, the flow limitation needs an addition of 1 cm pressure to disappear. Both machines will clear the flow limitation, the second one's graph will be steeper the flow limitation will disappear in the time it takes to raise the pressur in .5 cm. increments: that is 4 secs. The other machine will need 10 seconds to arrive at the same added pressure - it's graph will not so steep, the changes not so abrupt.

For some people, the more abrupt change in pressure will be bothersome.

O.

[ozij]

Than you both!

I am still wondering how someone determines if it is the response to an apnea that bothers them (allowing they are asleep) vs the response that anyone deals with in the way a machine transitions from one breath to another.

I think it's a moot point. When you try two machines at the same pressure range, and, all other thing being equal, you feel better, and sleep better, with one of them, then obviously that's the one you should use.

If you have a lower AHI, then that could be the reason - the technically curious might want to know why their AHI is higher on one machine that on the other - but that's of theoretical, technical (as opposed to clinical, personaly applicable) interest. But if your AHI is the same on both machines, and you sleep better with one, then something else makes the difference. Since some poeple are disturbed by pessure changes (and do better on straight PAP) I suppose fast transitions could be an explanation.

Be that as it may, I wouldn't lose sleep over it....

Ma shlomcha

I'm a female, Chuck, so the question should be "ma shlomech?".... The answer is metsuyan, toda! (Excellent, thank you).

O.

[GoofyUT]

Ozij-

Once again, your point above is EXCELLENT and of critical importance for folks here to understand. Ultimately, what matters is to find the auto-titrating PAP (if the decision to auto-titrate is thoughtfully made in consultation with a doctor one trusts) that provides the BEST SLEEP and the lowest AHIs for each individual, REGARDLESS of the brand or manufacturer.

I was simply trying to explain my speculations about why I happen to respond better to the Respironics algorithm than I do to that contained in ResMed machines. I believe that the shape of the Resprionics algorithm waveform matches the flow-dynamics for my particular SDB better than does ResMed's. Others will find that to be true of ResMed's, P-B's, Devilbiss's, Somnotech's or Invacare's algorithms. Just like, depending on the infection, some will respond better to zithromycin than Biaxin or Augmentin, and not everyone will respond well to penicillin no matter how well known it is.That's why I believe that its so important to insist on trials of different machines until you find the one that works FOR YOU. And, its why I find it to be so abhorrent to witness the pro-Respironics proselytizing that often appears on this site.

But, my speculations aside, the wisdom of your point about finding the machine that allows one to simply SLEEP THE BEST, is of PARAMOUNT importance here and should be heeded by all!!!!

Toda Raba!

Chuck

[Guest]

I was simply trying to explain my speculations about why I happen to respond better to the Respironics algorithm than I do to that contained in ResMed machines.

I believe that the shape of the Resprionics algorithm waveform matches the flow-dynamics for my particular SDB better than does ResMed's. Others will find that to be true of ResMed's, P-B's, Devilbiss's, Somnotech's or Invacare's algorithms.

since you are so good at knowing those algorithms, I wasn't aware Invacare even made a autopap to HAVE an algorithm? Did they just add one to their CPAPs?

Maybe you can help me with that one, because I can't seem to find it on their website, since it appears they don't make one, I go back to my original assumption, you have no idea about how they function much less wave forms.

[dsm]

[quote="GoofyUT"]Ozij-

Once again, your point above is EXCELLENT and of critical importance for folks here to understand. Ultimately, what matters is to find the auto-titrating PAP (if the decision to auto-titrate is thoughtfully made in consultation with a doctor one trusts) that provides the BEST SLEEP and the lowest AHIs for each individual, REGARDLESS of the brand or manufacturer.

I was simply trying to explain my speculations about why I happen to respond better to the Respironics algorithm than I do to that contained in ResMed machines. I believe that the shape of the Resprionics algorithm waveform matches the flow-dynamics for my particular SDB better than does ResMed's. Others will find that to be true of ResMed's, P-B's, Devilbiss's, Somnotech's or Invacare's algorithms. Just like, depending on the infection, some will respond better to zithromycin than Biaxin or Augmentin, and not everyone will respond well to penicillin no matter how well known it is.That's why I believe that its so important to insist on trials of different machines until you find the one that works FOR YOU. And, its why I find it to be so abhorrent to witness the pro-Respironics proselytizing that often appears on this site.

But, my speculations aside, the wisdom of your point about finding the machine that allows one to simply SLEEP THE BEST, is of PARAMOUNT importance here and should be heeded by all!!!!

Toda Raba!

Chuck

[GoofyUT]

Doug-

I don't think that it is a moot point at all to consider the varying characteristics of the different algorithms and attempt to learn how tio match them best with each individual patient's presentation. I do believe that it is a serious shortcoming of the science in the new field of sleep medicine that this hasn't been undertaken in any more rigorous fashion as of yet.

For example, from my own experiences trialing different alogorithms, I would speculate that those with more "brittle" responses to PAP treatment, that is, those who experience more rapid and deeper desats in the face of flow degradations, would do better with the sharp attack of the ResMed algorithm, while those more susceptible to cortical arousals (light sleepers who are bothered by lights, sounds, the unnatural feel of the mask or the pressure, etc.) would do best with Respironics' more temperate, step-wise algorithm. But, that is simply my anecdotal impression based on a sample with a N=1. I couldn't imagine what to suggest to someone who is "brittle" AND a light sleeper!

I think that your curiosity about the different characteristics of the different manufacturer's autotitrating algorithms, and their electromechanical implementation is SPOT ON, and I wish that the science would embrace your curiosity in this area more earnestly, and quickly too! This hit and miss business is NONSENSE that we shouldn't have to tolerate. We wouldn't and don't when it comes to pharmaceuticals.

Chuck

[dsm]

[quote="GoofyUT"]Doug-

I don't think that it is a moot point at all to consider the varying characteristics of the different algorithms and attempt to learn how tio match them best with each individual patient's presentation. I do believe that it is a serious shortcoming of the science in the new field of sleep medicine that this hasn't been undertaken in any more rigorous fashion as of yet.

For example, from my own experiences trialing different alogorithms, I would speculate that those with more "brittle" responses to PAP treatment, that is, those who experience more rapid and deeper desats in the face of flow degradations, would do better with the sharp attack of the ResMed algorithm, while those more susceptible to cortical arousals (light sleepers who are bothered by lights, sounds, the unnatural feel of the mask or the pressure, etc.) would do best with Respironics' more temperate, step-wise algorithm. But, that is simply my anecdotal impression based on a sample with a N=1. I couldn't imagine what to suggest to someone who is "brittle" AND a light sleeper!

I think that your curiosity about the different characteristics of the different manufacturer's autotitrating algorithms, and their electromechanical implementation is SPOT ON, and I wish that the science would embrace your curiosity in this area more earnestly, and quickly too! This hit and miss business is NONSENSE that we shouldn't have to tolerate. We wouldn't and don't when it comes to pharmaceuticals.

Chuck

[GoofyUT]

In a few words Doug, here's what I mean when I describe ResMed machines as demonstrating a "sharp attack." Again, in the "iron lung" studies, ResMeds using the A10 algorithm (either the AutoSet "T" or the AutoSet Spirit), demonstrated a rise time of pressure MUCH shorter than did either Respironics or P-B machines, often rising to the maximum they were set for within 60-90 seconds, as I recall (but don't quote me on that). And, they demonstrated a much more gradual decay from their peak pressure than did Respironics REMstar Autos, which demonstrated a longer rise time since their increases were step-wise, but with a quicker, step-wise decay as well. So, the waveform for ResMed machines resembled a sinus wave skewed to the left dramatically with a slow decay, whereas Respironics resembled a more normal sinus wave.

How do I know that this accounted for my disrupted sleep architecture and poor sleep, if I was asleep while it was happening? I don't, but I do know that I slept for shiite when using a ResMed S8 AutoSet Vantage, but this resolved almost immediately when I switched to the REMstar Auto. So, I'm guessing that the ResMed's sharp attack was what caused my lack of successful response to APAP therapy, and I'll credit the Respironics algorithm with my successful response and sound nights sleep since I switched to it.

Again, please note that this is true ONLY for me, and others may profit from the quick rise times of ResMed machines and do far better on them. I wasn't one of them though.

Chuck