If RERAs are so bad, why aren't they a part of the AHI?

jnk wrote:A home-machine-reported "RERA" is not a real lab/center-reported RERA. A home-machine "RERA" is only a maybe-possibly-could-be-perhaps so-called "RERA." So to keep yourself from chasing ghosts the rest of your life, go by how rested you feel instead.

Just to oversimplify dial-wingin' a bit: Choosing a CPAP pressure as a home dial-winger is mostly a matter of trying either (1) a higher pressure or (2) a lower pressure. Once you have found the pressure (or range of pressures, in the case of APAP) that consistently gives you the lowest home-machine-reported average AHI, you are through with phase one of dial wingin'. Phase two is not to start chasing other ghostly info that a home machine may report, which is given only for trending info. Phase two is to tweak based solely on how rested you feel in the mornings as averaged over weeks of time. You tweak for feeling rested without increasing AHI, if possible.

Dr. K. was talking about REAL RERAs. NOT home-machine-reported maybe-possibly-could-be-perhaps so-called "RERAs." And he is talking about the people he treats--people who don't feel better once their AHI is down, not all people everywhere.

Get your sleep as good as you can get it, but no better.

Nice explanation! Are you suggesting that the AHI numbers -- as reported by a home-machine -- are more accurate than the RERA and CAs?

pikov22 wrote:

jnk wrote:A home-machine-reported "RERA" is not a real lab/center-reported RERA. A home-machine "RERA" is only a maybe-possibly-could-be-perhaps so-called "RERA." So to keep yourself from chasing ghosts the rest of your life, go by how rested you feel instead.

Just to oversimplify dial-wingin' a bit: Choosing a CPAP pressure as a home dial-winger is mostly a matter of trying either (1) a higher pressure or (2) a lower pressure. Once you have found the pressure (or range of pressures, in the case of APAP) that consistently gives you the lowest home-machine-reported average AHI, you are through with phase one of dial wingin'. Phase two is not to start chasing other ghostly info that a home machine may report, which is given only for trending info. Phase two is to tweak based solely on how rested you feel in the mornings as averaged over weeks of time. You tweak for feeling rested without increasing AHI, if possible.

Dr. K. was talking about REAL RERAs. NOT home-machine-reported maybe-possibly-could-be-perhaps so-called "RERAs." And he is talking about the people he treats--people who don't feel better once their AHI is down, not all people everywhere.

Get your sleep as good as you can get it, but no better.

Nice explanation! Are you suggesting that the AHI numbers -- as reported by a home-machine -- are more accurate than the RERA and CAs?

I'd like to hear the answer to this as well.

Home machines are pretty good at identifying obstructive apneas, as long as the non-intentional leak isn't too high at the time.

Other than that, home macines lack the sensors to use the same definitions that labs/centers do for hypopneas and below as far as effect on sleep.

A lab/center gives a sleep study. A home machine gives you a nightly breathing study. It doesn't know when you are asleep or exactly how your breathing is affecting your sleep.

Sorry. I didn't see the question earlier.

Apneas are bleedingly obvious. You stop breathing. The consequences are obvious.

Hypopneas are a little less obvious. You slow down breathing. They're a little less clear cut.

CPAP machines are pretty good at detecting the above, especially when they're severe.

Central apenea is a little more mysterious, but they do show up as apneas. They're harder to treat. CPAP machines are getting better at telling central apneas apart from obstructive.

RERA/UARS are less obvious and not as well understood, and are even less easy to detect. Even if the machine can accurately detect them, the doctors are not quite as sure about how to treat them. Insurance companies often deny coverage. I suspect this is mostly to save money, no matter what the cost to the patient, but they appear to be able to get away with it.

Hopefully things will improve in the future, in both the medical sense and the insurance coverage sense.

archangle wrote:RERA/UARS are less obvious and not as well understood, and are even less easy to detect.

I am going to disagree here. "IMHO", they/it are easy to detect for a number of reasons:

• Since the signal from an xPAP machine comes from a closed (or at least, as closed as you can get from a system that is leaking at about 35 L/M)(but this leak is a known value) system, it may be a little cleaner than from a spontaneously breathing patient, where the system is "open";
• Algorithms today are pretty accurate (that said, they still can't tell if one is asleep);
• TS2, one can look at the breath-by-breath waveforms and still use AASM criteria for the respiratory definition:

  Increasing... flattening of the waveform.. leading to...

  but, unfortunately leaving out "effort channels, EEG and oximetry"; and
• As much as everybody hates to do that, the HST initiative, which, rather than doing in-lab xPAP titration, sticks them on wide-open APAP for 2 weeks to 30 days and takes 95th percentile, forces one to "bend the rules" in order to effectively treat.

Therefore, I will maintain they are "easy to detect", as long as somebody is actually making an "increased effort" (see RERA definition) to detect them.

And further, if someone is stuck with the above HST scenario (Oxford be damned!), it's not like there's a choice in the matter. You gotta make do with what you have to work with.

mollete,

Do you find large variations in the significance of the flattening, across the spectrum of patients? I mean, do you find that the more minor breathing disturbances affect the sleep of one patient much more than another? And whenever the arousals and fragmentation remain undocumented, couldn't that be a reason, maybe, to speak of RERAs/UARS as unclear, less understood, less easy to detect, for an individual, in the context of a discussion of home-machine data? Or am I asking really stupid questions again?

-jeff

As an aside to the last several immediately preceding posts, would our "home" machines also be considered marginally effective at properly detecting and scoring Periodic Breathing events?

By the way, many informed opinions have turned this into an enormously informative thread for me anyway-thanks to all. I love learning this stuff!

The following info is long in the tooth (2001) but still kinda interesting, in that it sorta makes both points, I think:

"In many clinical laboratories . . . it is assumed that subtle changes in respiratory pattern (building respiratory effort and/or cascading snoring) terminated by EEG arousal represent a respiratory event (RERA). An alternative used by some clinical laboratories is to demonstrate that the repetitive arousals (or movements) are reduced in a patient when nasal CPAP is applied. . . . The use of . . . pressure based technique for assessing airflow and upper airway resistance changes . . . reliably detect apnea, hypopnea, and the subtle flow limitation observed in the 'Upper Airway Resistance Syndrome.' . . . During inspiration, the collapsibility of the upper airway causes a Starling resistor-like behavior and results in a maximum flow, regardless of increases in effort. The normal “sinusoidal” inspiratory airflow becomes flattened (develops a plateau). The incomplete airway obstruction also causes inspiratory time to increase. Overall, this appears as a flattening of the waveform and is typically seen in breaths of decreased amplitude. These events are usually associated with increased respiratory effort and may represent either hypopneas or RERAs. "-- http://www.aastweb.org/resources/focusg ... rotech.pdf

Color added by me.

Of course, they aren't really discussing home machines, since they are talking about being able to document arousals and actual effort, which home treatment machines alone can't do well, since they don't have effort belts or EEG (although arousals may be implied in the breathing waveform). But the principles are similar, I believe.

Getting back to the original question in the title of the thread, I believe the real answer to be this: "Because insurance companies don't want to agree to pay for a CPAP machine for every single person they cover." A "disorder" that everyone has is no "disorder" at all, from their point of view. And everyone on the planet gets sleepy and tired now and then, and no one breathes perfectly at night. Thus, eveyone would qualify to get a CPAP machine if "sleepy and an imperfect breather" were enough.

If you use nonsubjective measurements to prove someone needs treatment, you choose nonsubjective measurements that most often point to something being out of the ordinary. The choice made was AHI. It is imperfect, but is something in the middle ground beyond someone saying "I don't sleep so good." That sort of imperfect measure is the pitfall of a system that refuses to use simple response to therapy as the yardstick to prove the need for the treatment.

jnk wrote:Do you find large variations in the significance of the flattening, across the spectrum of patients? I mean, do you find that the more minor breathing disturbances affect the sleep of one patient much more than another? And whenever the arousals and fragmentation remain undocumented, couldn't that be a reason, maybe, to speak of RERAs/UARS as unclear, less understood, less easy to detect, for an individual, in the context of a discussion of home-machine data? Or am I asking really stupid questions again?

Thanks for that hanging curve there, jeff, but since baseball season is over (and has been for a while)(for us, anyway) I'll just head back to the dugout.

Anyway, while it may be interesting (although probably not) to look at single breaths and sort them into one of the Nine Different Types of Flow Limitations which somehow identifies where the source of the limiting factor is (Aha! The left nostril had a protuberating turbinate in the power of smegma!), in practice, one has to (or least, this one) look at a trend window of ~about 5 minutes. That said, one has to consider the monitor and resolution one has (i.e., if you're trying to do this with an iPhone, or even a GalS4 sideways, you won't see a lot).

old dude wrote:... I've come across articles that say RERAs are about as bad as any other SDB event. In particular, a doctor named Barry Krakow says that they are but one event on the continuum of SDB events and should be treated as such.

Yeah, well ol' Barry tends to make up stuff as he goes along. His "Expiratory Intolerance" proposal was soundly discredited by board members here such that his image examples were pulled from his website (although they live on in The Cloud). The treatment for that was supposed to be PB420E and dropping the EPAP, which made no sense.

Presently, his scheme is to use ASV. He's still touting "Expiratory Intolerance", but sheepishly says "Yeah, well could be ballistocardiographic effect", a concept he was also introduced to here. Interestingly, a recent bench test article of ASVs says they aren't all that hot for hypopnea (hold that thought).

Anyway, Barry's article, dismissed by the major sleep publications, eventually showed up in a circular. Epoch examples were embarrassing in their technical quality, and again, totally misinterpreted:

Figure 1: Thirty second epochs from titration polysomnography performed on a 43 y.o female (BMI 31.0; diagnostic sleep breathing indexes: AHI 9.7 events/hr, RDI 43.7 events/hr, and CAI 3.8 events/hr) showing expiratory intolerance manifesting as irregular deflections* and variability of expiratory duration on the expiratory limb of the airflow curve (Figure 1a), central-like pauses manifesting as extended end-expiratory phase pauses of the airflow curve lasting less than 10 seconds (Figure 1b), and central apneas (Figure 1c) in patients experiencing difficulty adapting to CPAP pressure. Also note the subtle variations in expiratory duration in Figure 1a, somewhat similar to but less overt than that seen in opiate-induced/associated sleep apnea. *A ballistocardiogenic effect may be a factor in these irregularities, but they disappear with ASV therapy.
a) Expiratory pressure intolerance. b) Central-like pauses. c) Central apnea.

So, to encapsulate a bit and at the risk of over generalizing would it be reasonable to say the following?

1. So called "home machines" are pretty good at returning an accurate AHI number (as long as they aren't overwhelmed by large leaks), but not so good at accurately detecting SDB events downstream of OAs and Hypopneas, i.e., RERAs, Periodic Breathing, Centrals and Clear Airway events.

2. A layman level patient (like myself) should then focus his or her efforts at improving AHI numbers and daytime somnolence, and barring some unusual repetitive numbers in the "downstream" events largely disregard them.

old dude wrote: 2. focus his or her efforts at improving AHI numbers and daytime somnolence

Without specifying what those "efforts" are, this statement is meaningless.

Cereal Killer wrote:

old dude wrote: 2. focus his or her efforts at improving AHI numbers and daytime somnolence

Without specifying what those "efforts" are, this statement is meaningless.

It wasn't a statement, it was a question.

old dude wrote:So, to encapsulate a bit and at the risk of over generalizing would it be reasonable to say the following?

1. So called "home machines" are pretty good at returning an accurate AHI number (as long as they aren't overwhelmed by large leaks), but not so good at accurately detecting SDB events downstream of OAs and Hypopneas, i.e., RERAs, Periodic Breathing, Centrals and Clear Airway events.

2. A layman level patient (like myself) should then focus his or her efforts at improving AHI numbers and daytime somnolence, and barring some unusual repetitive numbers in the "downstream" events largely disregard them.

Well, since the new technologies allow one to see breath-by-breath waveforms, one does not have to rely on the algorithm at all to correctly identify events, PB, etc. anywhere during the night. They can take a look and challenge the scoring (or lack therof) if they want.

Further, "IMHO", people are getting obsessed with "The Number". It seems to me that people would get a lot more bang for the buck if they spent more time on all the other factors that surround sleep.