[Treatment] Shouldn't the goal of PAP treatment be to minimize Obstructive Apnea?

[Netskier]

At this point, I think we should advise people to first reduce OSA asap because it is dangerous, and because PAP can reduce OSA, and then to examine the other components of the AHI.

If there is no (or reduced) OSA, then, by definition, isn't there no (or reduced) AHI? I don't mean to belittle your point, I'm just not sure I understand it. Regardless of whatever other events may occur, if you reduce OSA, you must reduce AHI. After all, OSA refers only to apneic events.

Which would you prefer: OA = 0 and AHI = 5,
or OA = 5.0 and AHI = 5.0?

OA= 1 and AHI = 5 vs OA = 5 and AHI = 5?

[greatunclebill]

At this point, I think we should advise people to first reduce OSA asap because it is dangerous, and because PAP can reduce OSA, and then to examine the other components of the AHI.

If there is no (or reduced) OSA, then, by definition, isn't there no (or reduced) AHI? I don't mean to belittle your point, I'm just not sure I understand it. Regardless of whatever other events may occur, if you reduce OSA, you must reduce AHI. After all, OSA refers only to apneic events.

Which would you prefer: OA = 0 and AHI = 5,
or OA = 5.0 and AHI = 5.0?

OA= 1 and AHI = 5 vs OA = 5 and AHI = 5?

i still don't understand how you can target portions of the ahi which is a combination number. if you are targeting oa how would you specifically try to lower oa and how would it not affect ahi? i still think its splitting hairs because if oa goes down, by definition, ahi should lower. we all want all of our numbers lower. its not like somebody is trying to lower ahi and not worrying about oa. they go together. i must be missing something here. i would prefer oa = 0.0 ahi = 0.0

[Netskier]

At this point, I think we should advise people to first reduce OSA asap because it is dangerous, and because PAP can reduce OSA, and then to examine the other components of the AHI.

If there is no (or reduced) OSA, then, by definition, isn't there no (or reduced) AHI? I don't mean to belittle your point, I'm just not sure I understand it. Regardless of whatever other events may occur, if you reduce OSA, you must reduce AHI. After all, OSA refers only to apneic events.

Which would you prefer: OA = 0 and AHI = 5,
or OA = 5.0 and AHI = 5.0?

OA= 1 and AHI = 5 vs OA = 5 and AHI = 5?

i still don't understand how you can target portions of the ahi which is a combination number. if you are targeting oa how would you specifically try to lower oa and how would it not affect ahi? i still think its splitting hairs because if oa goes down, by definition, ahi should lower. we all want all of our numbers lower. its not like somebody is trying to lower ahi and not worrying about oa. they go together. i must be missing something here. i would prefer oa = 0.0 ahi = 0.0

We can target both OA and Hypopneas with PAP therapy, but PAP therapy does not seem to affect either Clear Airway events nor Unspecific apneas. Lowering OA and Hypopneas with PAP will decrease AHI provided that it does not increase the other two components: Clear Airway events and Non-specific apneas.

HTH.

[SuperSleeper]

I would tremendously prefer having zero OA, and I submit that it is common sense to do so, and that focussing on AHI is a distraction from clinical significance.

Howdy again, Netskier...

The AHI is a "distraction from clinical significance"? How so? If we're to focus solely on "clear airway events" we need to also realize that no CPAP in the world can accurately determine whether these "clear airway events" are real centrals or something else.

Certainly we can utilize a mix of criteria, but if you dismiss AHI as a "clinically insignificant", then what do you suggest we use instead?

Maybe I'm missing your point here?

Thanks for any clarification you can offer.

[shanzlik]

Is there evidence that PAP can reduce Central Apneas? PAP should be able to reduce hypopneas.

There's some evidence that PAP at pressures over 10 can induce some central apneas, according to one of the articles in an early issue of ResMedica I was reading the other day. However, the article stated that the addition of the central apneas was usually far better than leaving the obstructive events untreated or less fully treated (if the pressure were reduced too much). The same article said that PAP wasn't inteded to treat central apneas specifically because you would wind up raising the pressure too often while people were awake, or you would begn "treating" peoples' sighs, which are perfectly normal, etc. I believe the article was from 2002-2003, so things could have changed.

[Netskier]

[quote=Netskier]I would tremendously prefer having zero OA, and I submit that it is common sense to do so, and that focussing on AHI is a distraction from clinical significance.

Howdy again, Netskier...

The AHI is a "distraction from clinical significance"? How so? If we're to focus solely on "clear airway events" we need to also realize that no CPAP in the world can accurately determine whether these "clear airway events" are real centrals or something else.

Howdy Supersleeper,

1. Re distraction, from what it seems, PAP can treat two clinically significant components of the AHI, namely OSA and Hypopneas, but PAP can NOT treat the two other components, namely Clear Airway Events (which might or might not be "Central [Nervous System]" Events), and Unspecified Apnea (from Sleepyhead's classification, and who knows what they are, and whether they are clinically significant). So the AHI aggregates these four components together, two of which clearly are clinically significant (OSA and Hypopneas), and two which are apparently not clinically significant (Clear Airway Events and Unspecified Apneas). I submit that mixing insignificant events with significant events distracts from the significant events. Therefore, the AHI is a distraction from clinical significance.

Yesterday, you wrote that higher pressures may or may not increase central events, and that this was a controversay, but evidently no one asserts that higher pressures reduce central events. So maybe higher pressures are hurting you by causing central events while the higher pressures are helping you by reducing OSA and Hypopneas.

If central events can hurt you, then they are clinically significant, and I am unsure at this point if central events can hurt you. Blood oxygenation is the appropriate metric of this.

2. I am suggesting ignoring Clear Airway events, not focussing on them at all, unless they are large enough to decrease the partial pressure of O2. I suspect that short Clear Airway events are insignificant, and would like to know how long they must be before they become clinically significant. Blood oxygen would seem to be the appropriate metric of this.

Certainly we can utilize a mix of criteria, but if you dismiss AHI as a "clinically insignificant", then what do you suggest we use instead?

I suggest using OSA and Hypopneas instead, and perhaps combining those two into a "Obstructive Index". I also suggest using blood pressure, as Rappaport suggested in the article Zonk posted yesterday. I also suggest using blood oxygenation. We should find ways of combining these significant metrics into some new indexes.

Maybe I'm missing your point here?

Thanks for any clarification you can offer.

Only that I am not currently very concerned about Clear Airway Events, and wonder how long they have to be before they become clinically significant.

I hope this helps.

[Netskier]

Is there evidence that PAP can reduce Central Apneas? PAP should be able to reduce hypopneas.

There's some evidence that PAP at pressures over 10 can induce some central apneas, according to one of the articles in an early issue of ResMedica I was reading the other day. However, the article stated that the addition of the central apneas was usually far better than leaving the obstructive events untreated or less fully treated (if the pressure were reduced too much). The same article said that PAP wasn't intended to treat central apneas specifically because you would wind up raising the pressure too often while people were awake, or you would begn "treating" peoples' sighs, which are perfectly normal, etc. I believe the article was from 2002-2003, so things could have changed.

Why would the article even suggest that PAP might treat central apneas when the same article just said that PAP over ten can induce, i.e., cause, central apneas?

This makes sense to me: "the addition of the central apneas was usually far better than leaving the obstructive events untreated or less fully treated (if the pressure were reduced too much)."

[SuperSleeper]

Thanks Netskier... good thought-provoking info.. I'll have to digest this when I get more time.. might have some more questions for you too, if that's okay.

[zonk]

The interview with Dr Michael Berthon-Jones was some time ago before the introduction of the S9 which can detect central apnea and distinguish between obstructive and central apnea and also does treat obstructive apnea above 10 unlike the older machines.
Dr.Michael Berthon-Jones interview, page 5:
http://www.resmed.com/au/assets/document...0906r1.pdf

[Netskier]

Thanks Netskier... good thought-provoking info.. I'll have to digest this when I get more time.. might have some more questions for you too, if that's okay.

You're welcome.

You also wrote elsewhere, in the Clear Airway Definition thread, that

But in CPAP therapy, for better or worse, sleep apnea severity and effectiveness is generally measured in AHI, and increasing pressures to combat obstructive events, even though it may slightly raise clear airway events, still can cause a net decrease in the overall AHI. For each individual, (on constant-pressure CPAP) there is a "sweet spot", or best range of pressures (for autos) that will result in the lowest AHI levels, while still maintaining clear airway events within an "acceptable" range.

My point is that it is worse, not better, to measure efficacy of PAP therapy with the AHI, and that it would be better to measure PAP efficacy with an "Obstructive Index" which would simply sum OSA and Hypopneas. Ideally one would want to combine this Obstructive Index with both blood pressure and blood oxygenation. It would be better to minimize the Obstructive Index than the AHI, up to the point where central events begin to decrease the partial pressure of oxygen.

That is why making small, incremental adjustments to pressure over time, noting the effects on AHI (and looking at obstructive and 'central' events also) can result in lowering AHI levels. It's basic scientific analysis.

This approach is ok, but could be improved by using the Obstructive Index instead of the AHI.