APNEA -v- HYPOPNEA

For me, personally, this thread had been the most useful since I have been reading this forum (12/05).

Everyone who contributed - thank you!

David

Snoredog wrote: SWS: ...it is what I would call pressure induced hypoapnea... It is the only name I can give it since it only seems to appear with too much pressure...

Well, that's a very fascinating working theory in its own right, Snoredog. A hypopnea is either central or obstructive. Can you expand that working theory just a bit more? What do you suspect the physiologic mechanism might be whereby an increase in pressure might cause an even greater anatomical airway obstruction? I was eventually able to come up with a theoretical case in biophysics to support your theory. However, to the best of my knowledge this particular etiological scenario has never been discovered or published. So I'm very interested in how you perceive a case for this bio-physic scenario might be constructed. I'm not throwing your theory out the window since I've kind of come up with a case to support it.

Snoredog wrote: ...Where I've seen this happen, said pressure was 10cm or less or well below where you typically see pressure induced centrals.

Well, now you've really piqued my curiosity. Can you expand just a bit about the observation methods employed and even the central apnea determination methods? Yup, your long time apnea bud's extremely fascinated by this whole topic of pressure induced SDB events.

Snoozin' Bluezzz, I'm with you. This thread has been quite a topic!

Yoga, I take "Daily for Life Total" by a company called Melaleuca. It reduced my LDL, but my cholesterol had been only marginally high for five years prior to taking that daily vitamin pack. Phytomega is supposed to be the active ingredient in that vitamin pack that helps with high cholesterol.

http://www.melaleuca.com/ps/index.cfm?f=ps.mainPage

I'm also curious about how increased pressures could enhance a physiological obstruction. But, I could see how it could inhibit CO2 venting, and affect respiration in that way.

Just a thought.

This thread has really interested me because since I started on an S8 auto a month ago I have not felt as good during the day as when I was on CPAP. I also am not dreaming especially in the AM as Chuck described.
My numbers on auto have looked OK to me (HI around 3 AI less than 1) but I am going to try straight CPAP again and see how that feels. I have a few questions:
1. Do pressure induced central apneas show up as HI's the next day on the menu?
2. If my one month ave pressure on auto was 8.8 what pressure should I set the straight CPAP on for the "experiment".
Thanks very much,
Kurt

ResMed machines don't score apneas as obstructive versus central as do Respironics. The Remstars will titrate pressure in the face of a flow interuption, until a certain point is reached (I believe that this point is a 3 cm increase). It will then score a "Non-responsive (NR)" apnea, which is another way of saying that its a central, and then will back the pressure back down.

ResMeds are designed to DO NOTHING in the face of a flow interuption it detects, and wait for it to clear on its own. It'll then begin increasing pressure to "pre-empt" any further flow interuption.

Now, Snoredog suggests that ResMeds are very sensitive to snore and will detect and titrate to stop snores even though the software doesn't score them. And he further reasons that in so doing, the increase in pressure may cause central HYPOPNEAS. However, the pathophysiology of this remains questionable. So, i wouldn't on the basis of this thread, be sweating centrals with my S8 AutoSet, if I were you. In answer to your question though; NO, pressure induced centrals don't get translated into hypopneas in your stats the next day. The S8 doesn't know what a central is, and even if it did, its trained to sit and do nothing until ANY apnea clears by itself, rather than increasing pressure which might make a central worse, and which might WAKE you. It may lean heavily on scoring hypops either because of wakeful artifacts or by its definition of what the flow degradation associated with hypopnea looks like, as opposed to what other manufactureres think a hypop looks like in terms of waveform. And, the hypops it IS scoring may be clinically innocuous.

Regarding a good pressure to set for a CPAP trial, I'd start with your titrated pressure from your PSG myself, and then slowly and gradually decrease the pressure by a centimeter every couple of days, and keep good records to see what the results are in terms of how you feel. If lowering it makes you feel worse, I'd go in the opposite direction till you find a pressure that makes you feel the best.

Just a thought.

Chuck

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): respironics, resmed, CPAP, Hypopnea

-SWS wrote:

Snoredog wrote: SWS: ...it is what I would call pressure induced hypoapnea... It is the only name I can give it since it only seems to appear with too much pressure...

Well, that's a very fascinating working theory in its own right, Snoredog. A hypopnea is either central or obstructive. Can you expand that working theory just a bit more? What do you suspect the physiologic mechanism might be whereby an increase in pressure might cause an even greater anatomical airway obstruction? I was eventually able to come up with a theoretical case in biophysics to support your theory. However, to the best of my knowledge this particular etiological scenario has never been discovered or published. So I'm very interested in how you perceive a case for this bio-physic scenario might be constructed. I'm not throwing your theory out the window since I've kind of come up with a case to support it.

Snoredog wrote: ...Where I've seen this happen, said pressure was 10cm or less or well below where you typically see pressure induced centrals.

Well, now you've really piqued my curiosity. Can you expand just a bit about the observation methods employed and even the central apnea determination methods? Yup, your long time apnea bud's extremely fascinated by this whole topic of pressure induced SDB events.

Snoozin' Bluezzz, I'm with you. This thread has been quite a topic!

man the login timer on this site sucks, that was my post above.

[quote="GoofyUT"]ResMed machines don't score apneas as obstructive versus central as do Respironics. The Remstars will titrate pressure in the face of a flow interuption, until a certain point is reached (I believe that this point is a 3 cm increase). It will then score a "Non-responsive (NR)" apnea, which is another way of saying that its a central, and then will back the pressure back down.

ResMeds are designed to DO NOTHING in the face of a flow interuption it detects, and wait for it to clear on its own. It'll then begin increasing pressure to "pre-empt" any further flow interuption.

Now, Snoredog suggests that ResMeds are very sensitive to snore and will detect and titrate to stop snores even though the software doesn't score them. And he further reasons that in so doing, the increase in pressure may cause central HYPOPNEAS. However, the pathophysiology of this remains questionable. So, i wouldn't on the basis of this thread, be sweating centrals with my S8 AutoSet, if I were you. In answer to your question though; NO, pressure induced centrals don't get translated into hypopneas in your stats the next day. The S8 doesn't know what a central is, and even if it did, its trained to sit and do nothing until ANY apnea clears by itself, rather than increasing pressure which might make a central worse, and which might WAKE you. It may lean heavily on scoring hypops either because of wakeful artifacts or by its definition of what the flow degradation associated with hypopnea looks like, as opposed to what other manufactureres think a hypop looks like in terms of waveform. And, the hypops it IS scoring may be clinically innocuous.

Regarding a good pressure to set for a CPAP trial, I'd start with your titrated pressure from your PSG myself, and then slowly and gradually decrease the pressure by a centimeter every couple of days, and keep good records to see what the results are in terms of how you feel. If lowering it makes you feel worse, I'd go in the opposite direction till you find a pressure that makes you feel the best.

Just a thought.

Chuck

[quote="kurtr"]This thread has really interested me because since I started on an S8 auto a month ago I have not felt as good during the day as when I was on CPAP. I also am not dreaming especially in the AM as Chuck described.
My numbers on auto have looked OK to me (HI around 3 AI less than 1) but I am going to try straight CPAP again and see how that feels. I have a few questions:
1. Do pressure induced central apneas show up as HI's the next day on the menu?
2. If my one month ave pressure on auto was 8.8 what pressure should I set the straight CPAP on for the "experiment".
Thanks very much,
Kurt

[quote="BetterBreathinBob"]Very interesting reading all the posts about the data downloaded from the machines, pressure changes and folks always trying to get the low numbers.

The software programs only detect snoring or flow limitations or a combination of the 2. Some people feel better sleeping on a lower pressure or the fixed cpap machines and wonder why! The reason is that a mild hypopnea or apneic event, while being counted in the software may or may not be causing an arousal in your sleep stages. The whole goal behind CPAP therapy is to stop the fragmentation of your sleep and allow the body to spend as much time as possible in the deep restorative stages called delta or stages 3 and 4.

Many times in the sleep lab where I work I'll see mild hypops without arousals and sometimes with oxygen desats.

The bottom line is how do you feel during the day. More rested then before using the theray or still tired? Don't go crazy over the numbers, your subjective feeling of your alertness is more important.

CPAP user for 3 years, sleep tech for 7 years and Respiratory therapist for 20 years.

Keep up the great communication here, it helps everyone.

Bob

Continuing CPAP trial at 8cm/noEPR/30 min. ramp

Slept OK with no awakenings, but I awoke for the day fairly early (bummer on a holiday!!!) after 7.65 hours.

AHI=1.4, AI=0, HI=1.4.

Gonna go down to 7.6cm tonite.

C

[quote="Snoredog"][quote="GoofyUT"]ResMed machines don't score apneas as obstructive versus central as do Respironics. The Remstars will titrate pressure in the face of a flow interuption, until a certain point is reached (I believe that this point is a 3 cm increase). It will then score a "Non-responsive (NR)" apnea, which is another way of saying that its a central, and then will back the pressure back down.

ResMeds are designed to DO NOTHING in the face of a flow interuption it detects, and wait for it to clear on its own. It'll then begin increasing pressure to "pre-empt" any further flow interuption.

Now, Snoredog suggests that ResMeds are very sensitive to snore and will detect and titrate to stop snores even though the software doesn't score them. And he further reasons that in so doing, the increase in pressure may cause central HYPOPNEAS. However, the pathophysiology of this remains questionable. So, i wouldn't on the basis of this thread, be sweating centrals with my S8 AutoSet, if I were you. In answer to your question though; NO, pressure induced centrals don't get translated into hypopneas in your stats the next day. The S8 doesn't know what a central is, and even if it did, its trained to sit and do nothing until ANY apnea clears by itself, rather than increasing pressure which might make a central worse, and which might WAKE you. It may lean heavily on scoring hypops either because of wakeful artifacts or by its definition of what the flow degradation associated with hypopnea looks like, as opposed to what other manufactureres think a hypop looks like in terms of waveform. And, the hypops it IS scoring may be clinically innocuous.

Regarding a good pressure to set for a CPAP trial, I'd start with your titrated pressure from your PSG myself, and then slowly and gradually decrease the pressure by a centimeter every couple of days, and keep good records to see what the results are in terms of how you feel. If lowering it makes you feel worse, I'd go in the opposite direction till you find a pressure that makes you feel the best.

Just a thought.

Chuck

I did my first test last night and went straight CPAP at a pressure of 9. I slept very well and woke feeling rested for the first time since I started APAP a month ago.
My numbers were down significantly; AI down from a 1.0 ave to a 0.2 and HI down from a 3.0 ave to a 1.2. Even thought they were low originally I was waking up feeling terrible which was my main issue.
I will stay at 9 for a while then try a lower pressure and see how that feels.
Questions:
1. Does this mean the auto mode was causing centrals?
2. Before I had a Respironics and tried the cflex and it made me feel terrible also, was it creating the same thing?
3. Are we the exception to the rule, people feeling worse on auto?

Thanks for the info on this forum. I would not have figured this out....

Kurt

Congrats on the good night you had,I hope that they continue, and I can certainly understand your intent to continue on a CPAP trial given your results last nights. Do be careful though; One swallow DOESN'T make a summer.

I'd be reluctant to believe that you were experiencing centrals with your AutoSet. But who knows? Some folks (me included) just do better on CPAP than APAP. There was a recent thread here in which a lot of long-tiem users on this forum posted that they had returned to CPAP after APAP trials since they felt and slept better with constant pressure. So, are we the exception to the rule? Probably since many, many people have found Auto to be a wonderful relief. But, there are certainly many folks who ahve had the same experience as you and I. And, I for one, intend to continue to experiment before I rule out APAP all together, since I have had only six days with a CPAP trial. However, its looking good so far.

Did C-flex do the same thing? Don't know, but there are also lots of folks who report doing better without C-flex. I suspect in my case that the newness of it all was making me very sensitive to ANY changes and was causing cortical arousals. Switching to constant pressure minimized this for me. Thought he pressure reduction in CPAP is only momentary, maybe the same thing was happening to you.

Hope this helps.

Chuck