POLL: Typical AHI for ResMed Users

[-SWS]

In my mind, this begs the question, what is the best therapy for hypoventilation?

It's probably worth distinguishing a sustained hypoventilatory disorder from the incidental and occasional hypoventilation/hypopneas that sometimes accompany ordinary obstructive SDB.

None of these APAP machines are targeted for treating sustained hypoventilatory disorders. They are intended to treat ordinary obstructive SDB---including hypopneas. However, BiLevels and ventilators are targeted for treating various sustained hypoventilatory disorders.

Regardless, a typical hypopnea for someone with OSA might be thought of as short-duration hypoventilation. I think of those rather ordinary hypopneas as a short-duration based subset of all possible types of hypoventilation. But the point in my above post is that clinics and manufacturers must draw a line between what they score as a hypopnea and what they call (sustained) hypoventilation instead. Respironics and Resmed may draw that line a little differently---accounting for at least some differences in APAP-scored HI.

* * * *

Maybe Muffy can help us with how AASM certified sleep centers score sustained hypoventilation versus typical short-duration hypopneas. As it stands I don't have a clue...

[Muse-Inc]

Thanks for the info!

...Maybe Muffy can help us with how AASM certified sleep centers score sustained hypoventilation instead of typical short-duration hypopneas. As it stands I don't have a clue...

Muffy?

[Muffy]

Thanks for the info!

...Maybe Muffy can help us with how AASM certified sleep centers score sustained hypoventilation instead of typical short-duration hypopneas. As it stands I don't have a clue...

Muffy?

Hypoventilation is scored when there is > or = 10 mmHg increase in PaCO2 during sleep in comparison to awake supine value.

Muffy

[Muse-Inc]

Hypoventilation is scored when there is > or = 10 mmHg increase in PaCO2 during sleep in comparison to awake supine value.

Ah, PaCO2 = patient's level of CO2??? I thought this was a blood test?

[-SWS]

Right, Muse-Inc. PaCO2 denotes the "pressure" or "gas tension" of arterial CO2 in a patient.

Well, the xPAP machines can't measure CO2 to accurately measure hypoventilation according to AASM definition. But I think since they are comparing mean volumes against predicted supine awake volumes, they are at least attempting to estimate hypoventilation occurrences.

Thanks for the scoring definition, Muffy.


Better forward twokatmew's poll question to this page as well, so we don't lose track:

As a new PAPper and ResMed user, I know that medical professionals claim AHI < 5.0 is "normal." Still most of what I initially read on this forum is about Respironics users seeking (and often getting) AHIs of 1.5 or less. Eventually I found posts by Rested Gal about ResMed machines over-scoring hypopneas and her reasoning for cutting the HI in half. (Velbor has weighed in on this interesting topic also.) Even so, my numbers have been consistently depressing. In recent polls and threads, I'm starting to read about ResMed users "doing just fine" (or not!) with significantly higher numbers. So I decided to start a new POLL/thread to hopefully encourage ResMed newbies (or oldsters) who may be struggling with higher AHIs.

I know there are ResMed users with near-Respironics AHIs, but I'm also realizing there are probably more ResMed users with significantly higher numbers, and this can be OK.

Anyway, off we go....

[-SWS]

I thought this was a blood test?

Sorry, Muse-Inc... I forgot to mention that CO2 can be monitored in the breath, in the blood, or even on the skin. That last method, transcutaneous CO2 monitoring, is probably the most commonly employed during a PSG sleep study. However, an ordinary PSG seldom includes CO2 monitoring of any kind.


Hmmm...

So an alternate or perhaps even additional theory regarding why Respironics scores fewer hypopneas than Resmed just may emerge with this hypothetical explanation:
Respironics is considering some of those events to be sustained hypoventilation instead of hypopneas-----whereas Resmed may be scoring them as hypopneas.

According to that theory Resmed may be scoring some long-duration flow reductions as "hypopneas" whereas the Respironics Hypoventilation detection circuit rather prematurely pulls the plug on hypopnea scoring and calls them "hypoventilation" instead.

If so, there's Muffy's hypopnea "exclusionary criteria" albeit based in the hypopoventilation control layer rather than the VB control layer. Both breathing conditions may have been present---with the H-layer in algorithmic control---when Muffy noticed Respironics not scoring hypopneas that should have been.

If that's what's happening, we should notice a pattern of significantly longer hypopneas showing up in the Resmed reports---and a comparative pattern of long hypopneas remiss from the Encore reports.

Velbor, et al-- do you score higher HI's on the Resmed reports? If so, does Resmed ever reflect long hypopneas that don't seem to show up on the Encore reports?

[Velbor]

Velbor, do you score higher HI's on the Resmed reports? If so, does Resmed ever reflect long hypopneas that don't seem to show up on the Encore reports? :?:

Under comparable circumstances, the ResMed HI is ALWAYS HIGHER for me than the Respironics HI:

Average of individual readings for 20 nights:

Fixed CPAP pressure of 11.0 (so ALGORITHM issues are not involved, only event definitions):
ResMed Activa nasal mask:

ResMed: AHI = 5.2 (AI = 0.2, HI = 5.0)
Respironics: AHI = 1.2 (AI = 0.5, HI = 0.7)

The same information, but with the ResMed UltraMirage Full Face mask:

ResMed: AHI = 9.3 (AI = 0.8, HI = 8.6)
Respironics: AHI = 3.3 (AI = 2.0, HI = 1.3)

The same information, but AutoPAP with UNOPTIMIZED pressures of 6.0 - 20.0:
ResMed Activa nasal mask:

ResMed: AHI = 5.7 (AI = 0.2, HI = 5.5)
Respironics: AHI = 6.5 (AI = 1.8, HI = 4.7)

and similarly, AutoPAP with UMFF mask:

ResMed: AHI = 9.7 (AI = 0.8, HI = 8.9)
Respironics: AHI = 6.3 (AI = 2.7, HI = 3.5)

I am currently compiling data at a more OPTIMIZED AutoPAP setting of 10.0 - 20.0.
An interim look (20 days for ResMed, 9 days so far for Respironics) shows:

for the Activa nasal mask:

ResMed: AHI = 7.0 (AI = 0.3, HI = 6.6)
Respironics: AHI = 1.1 (AI = 0.4, HI = 0.8)

and for the UMFF mask:

ResMed: AHI = 9.1 (AI = 0.5, HI = 8.5)
Respironics: AHI = 2.4 (AI = 1.4, HI = 0.9)

At the same time, it should be noted that the ResMed AI is ALWAYS LOWER than the Respironics AI under the same conditions.

Also, in all but one of these six comparisons, the ResMed AHI is HIGHER.

As to "long hypopneas", neither machine provides duration data for hypopneas.

Regards, Velbor

[Muse-Inc]

...As to "long hypopneas", neither machine provides duration data for hypopneas...

What a shame! Wonder if they record it but just don't report...if so, maybe one of our resident geeks can analyze the output files from the software and extract the salient data. Would be interesting to know .

[Muffy]

A while ago, some guys were tossing around a definition of >120 seconds for hypoventilation event, but I don't know the basis for that or where they got that from.

Anyway, if we believe the RIC 7168429 Patent, the maximum allowable time for a hypopnea is 60 seconds.

Muffy

[Muffy]

Now, while I think "hypoventilation" is simply talking about "hypopneas", since this algorithm is also looking for flattening characteristics, it would seem that there would still be a few "rounded" waveforms left over that still end up stalling the algorithm and go unreported (I imagine these would be central hypopneas).

Well, I'm not so sure that the Respironics term "hypoventilation" speaks exclusively of what Respironics calls "hypopneas". Here is the definition of "hypoventilation" taken from the above patent description:

hypoventilation is defined as five (5) consecutive breaths with Vm less than 40 percent of the predicted awake supine Vm

Vm refers to "mean inspiratory airflow" here.

Well again, even the most generous definitions for "hypoventilation" were >120 seconds, and since the cutoff for hypopnea in the Respironics algorithm is 60 seconds, everything between 5 breaths and 60 seconds would be a hypopnea.

There are no flattening requirements for those "hypoventilation" events according to Respironics.

"Flatness" has many references in the Remmers patent (the Psearch portion of the algorithm), but it is in the 7168429 patent that some hypopnea events may be discarded:

In a presently preferred embodiment, the A/H control layer does not discriminate between obstructive/restrictive and central apnea/hypopnea event unless the pressure being delivered to the patient is above a certain threshold. This threshold ensures that a pressure treatment is provided if the patient is being treated with a relatively low pressure regardless of whether the apnea/hypopnea was central or obstructive. If the pressure is below this threshold, the system performs the pressure treatment as discussed above in Section G. If, however, the patient is being treated with a relatively high pressure, i.e., a pressure above the pressure threshold, it is preferable to determine whether the apnea/hypopnea is central or obstructive,because, as noted above, increasing the pressure for a central apnea provided no therapeutic effect.

In a preferred embodiment, the pressure threshold is set at 8 cmH2O, which has been determined from analysis of clinical data to be a pressure level that provides a moderate degree of pressure support for most patients, but is not too high as to cause unduly high pressures to be delivered should the patient be experiencing a central apnea/hypopnea. It is to be understood that this threshold can have other values and can be adjustable depending on the characteristics of the patient or the patient's history.

Muffy

[Muffy]

There's always the possibility Respironics went with a proprietary data structure---perhaps even as an interdiction measure in part.

Well, I tried the basic stuff and all I get is hieroglyphics. There are some protections geared toward HIPPA compliance, so I wonder if the data itself is encrypted.

Muffy

[-SWS]

At the same time, it should be noted that the ResMed AI is ALWAYS LOWER than the Respironics AI under the same conditions.

Thanks, Velbor. Other posters have commented on that slight ratio-inversion tendency as well.

My hunch is the HI scoring differences between those two manufacturers likely boil down to not one but a variety of proprietary algorithmic differences.

Not necessarily right or wrong in either case... But "different" as so many posters on this message board have aptly said.

There are no flattening requirements for those "hypoventilation" events according to Respironics.

"Flatness" has many references in the Remmers patent (the Psearch portion of the algorithm), but it is in the 7168429 patent that some hypopnea events may be discarded:

I think we may have three unique Respironics event types sailing along at the same time: 5-breath & longer hypoventilation, obstructive hypopneas (w/flattening), and presumed central hypopneas (w/out flattening).

The Respironics definition of "hypoventilation" from our first patent under discussion talks about: 1) comparing against predicted supine volumes while awake, and 2) needing a 40% volume reduction for five consecutive breaths. Because they require a long string of breaths, and compare against supine awake versus a recent baseline during sleep, I don't think they're talking about hypopneas.

By contrast that Remmers patent description describes more typical hypopnea criteria: 1) it compares flow against a sleep-established baseline, and 2) it scores highly typical short-duration hypopneas---not just the 5-breath Godzilla hypopneas. But the hypopnea flattening recognition becomes very important since the round (presumed central) hypopneas can become exacerbated by pressure increases.

There's always the possibility Respironics went with a proprietary data structure---perhaps even as an interdiction measure in part.

Well, I tried the basic stuff and all I get is hieroglyphics. There are some protections geared toward HIPPA compliance, so I wonder if the data itself is encrypted.

Muffy

Was it a card from the new PR Auto?

[Muffy]

There's always the possibility Respironics went with a proprietary data structure---perhaps even as an interdiction measure in part.

Well, I tried the basic stuff and all I get is hieroglyphics. There are some protections geared toward HIPPA compliance, so I wonder if the data itself is encrypted.

Muffy

Was it a card from the new PR Auto?

The card, the download, the export, the SQL file, everything.

Muffy

[-SWS]

The whole kit-and-kaboodle... Bummer!

No real surprise I guess.

[Greybeard]

Why is this poll relevant? We all know that different machines register apneas differently. Never lose sight of the fact that the objective of this therapy is to make you sleep better and feel better! Those who chase low numbers without this objective in mind will probably fail. The numbers that your machine records are guidelines, not absolutes.

Good Luck.