A Forum For All Things CPAP
https://www.cpaptalk.com/
It is debatable whether these machines can be said to do a "good job" detecting whether you're asleep if they cannot be accurate. Apparently, ResMed and F&P do not trust their sleep detection enough to provide an index of sleep efficiency or to use this information when calculating the AHI. However, I was only challenging the assertion that it is "common knowledge" that these machines are incapable of accurately detecting whether or not the user is sleeping.Dog Slobber wrote: ↑Thu Apr 06, 2023 3:39 pmSounds like you're not aware that the following two statements:Can both be true.
- Sleep/awake cannot be accurately determined without EEG, and
- ResMed's Auto-Ramp feature can do a good job detecting whether you're asleep or awake based on breathing pattern
Thank you for this useful information! Luckily, it appears I can control my apnea with a minimum air pressure setting that I find tolerable. My CPAP struggles have been mostly caused by an ill-fitting noisy and leaky face mask and F&P's overly heated air tube with no temperature setting control.robysue1 wrote: ↑Thu Apr 06, 2023 3:29 pm
[snip]
Information about Resmed's AutoRamp was pulled from https://www.resmed.com/en-us/sleep-apne ... -pressure/
In the case of Resmed's AutoRamp, the machine is looking for one of the following three things before it starts to ramp the pressure up:
[snip]
- 30 breaths of stable breathing (roughly 3 minutes)
- 5 consecutive snore breaths
- 3 obstructive apneas or hypopneas within 2 minutes
- 30 minutes have passed since the machine was turned on
]You seem to be reading what you want to hear into simple statements.
Could it be that I am interpreting simple statements in a straight forward manner the way a typical lay person would, and you are reading in nuances and caveats based on your knowledge of this field and what you want to hear?billbolton wrote: ↑Thu Apr 06, 2023 10:15 pmYou seem to be reading what you want to hear into simple statements.
The Resmed alogrithm is only useful for the gross purpose of commencing or ceasing treatment. It will not reliably "score" anything but autonomous sleep breathing. The "auto" ramp sensing is solely to determine whether autonomous sleep breathing has commenced, and has no other useful purpose.
andMJS_ wrote: ↑Thu Apr 06, 2023 7:28 pmIt is debatable whether these machines can be said to do a "good job" detecting whether you're asleep if they cannot be accurate. Apparently, ResMed and F&P do not trust their sleep detection enough to provide an index of sleep efficiency or to use this information when calculating the AHI. However, I was only challenging the assertion that it is "common knowledge" that these machines are incapable of accurately detecting whether or not the user is sleeping.Dog Slobber wrote: ↑Thu Apr 06, 2023 3:39 pmSounds like you're not aware that the following two statements:Can both be true.
- Sleep/awake cannot be accurately determined without EEG, and
- ResMed's Auto-Ramp feature can do a good job detecting whether you're asleep or awake based on breathing pattern
Not contradictory at all: An EEG is needed to determine precisely when you first fall asleep, as well as precisely when you wake up in the middle of the night and precisely how long each wake lasts. And this stuff is important for accurately determining the AHI value for a diagnostic sleep test.MJS_ wrote: ↑Fri Apr 07, 2023 1:05 amCould it be that I am interpreting simple statements in a straight forward manner the way a typical lay person would, and you are reading in nuances and caveats based on your knowledge of this field and what you want to hear?billbolton wrote: ↑Thu Apr 06, 2023 10:15 pmYou seem to be reading what you want to hear into simple statements.
The Resmed alogrithm is only useful for the gross purpose of commencing or ceasing treatment. It will not reliably "score" anything but autonomous sleep breathing. The "auto" ramp sensing is solely to determine whether autonomous sleep breathing has commenced, and has no other useful purpose.
Thank you for your detailed explanation. I'm sticking with my assertions that this knowledge is not "common", and it is not reasonable to expect a lay person to deduce much of this from simple statements like: "When set to Auto, your device will ramp up to your prescribed pressure only when it detects that you've fallen asleep" or "the machine does a good job detecting whether you are asleep or awake."robysue1 wrote: ↑Fri Apr 07, 2023 7:11 amandMJS_ wrote: ↑Thu Apr 06, 2023 7:28 pmIt is debatable whether these machines can be said to do a "good job" detecting whether you're asleep if they cannot be accurate. Apparently, ResMed and F&P do not trust their sleep detection enough to provide an index of sleep efficiency or to use this information when calculating the AHI. However, I was only challenging the assertion that it is "common knowledge" that these machines are incapable of accurately detecting whether or not the user is sleeping.Dog Slobber wrote: ↑Thu Apr 06, 2023 3:39 pmSounds like you're not aware that the following two statements:Can both be true.
- Sleep/awake cannot be accurately determined without EEG, and
- ResMed's Auto-Ramp feature can do a good job detecting whether you're asleep or awake based on breathing pattern
Not contradictory at all: An EEG is needed to determine precisely when you first fall asleep, as well as precisely when you wake up in the middle of the night and precisely how long each wake lasts. And this stuff is important for accurately determining the AHI value for a diagnostic sleep test.MJS_ wrote: ↑Fri Apr 07, 2023 1:05 amCould it be that I am interpreting simple statements in a straight forward manner the way a typical lay person would, and you are reading in nuances and caveats based on your knowledge of this field and what you want to hear?billbolton wrote: ↑Thu Apr 06, 2023 10:15 pmYou seem to be reading what you want to hear into simple statements.
The Resmed alogrithm is only useful for the gross purpose of commencing or ceasing treatment. It will not reliably "score" anything but autonomous sleep breathing. The "auto" ramp sensing is solely to determine whether autonomous sleep breathing has commenced, and has no other useful purpose.
But once sound sleep is, in fact, established, it's pretty easy to just look at a person and say with some confidence, "that person is asleep" even though we can't tell precisely when that sleeping person's consciousness changed from Wake to Sleep just by looking at them.
Same thing with the flow rate from our CPAPs: Statistics combined with shape of inhalations in the flow rate can be used to determine that there is a high probability that the person using the machine is asleep.
In the best (and easiest) scenario, once sound sleep is, in fact, established, the person's breathing should even out and become very stable and very regular with inhalations that are both more regular and smaller than waking inhalations. With decent programming, a APAP machine can be programmed to start ramping up the pressure from the starting Ramp pressure to the Min pressure setting once it is clear that very stable and very regular inhalations have been going on for a long enough time for it to be reasonable to assume the person is, in fact, asleep. And that's exactly what Resmed's programmers use for the first criterium for ending the auto ramp: Three minutes (30 breaths) of stable breathing has a high probability of being associated with the onset of sustained sleep; hence it's reasonable to start increasing the pressure from Ramp pressure to Min pressure.
Two of the other criteria that Resmed's programmers use to decide there is a high probability the person is asleep are based on the fact that in developing the Auto algorithm, they've already discovered ways to use the flow rate data to flag certain anomalies in the flow rate data as "snoring" and "OAs" and "Hs". Because the device is designed to treat sleep disordered breathing, Resmed's programmers have made decision to assume that if enough of those particular breathing patterns are detected during the AutoRamp period, the person is likely asleep and the bad breathing should be treated by ending the ramp and increasing the pressure. Notably, for both snoring and OAs/Hs, the Resmed programmers require more than one such event---5 consecutive snores or 3 OAs/Hs within a two minute period---specifically because some people's wake breathing can contain flow patterns that resemble the flow pattern of sleep disrupted breathing events, and they don't want the machine to prematurely start raising the pressure before the person using the machine is asleep. (The whole idea behind the auto ramp is that increasing the pressure while a person is awake may make it (much) harder for the person to fall asleep.)
The final criteria that Resmed uses to end the auto ramp is based on statistics: Most people have a latency to sleep that is between 10 and 20 minutes long. So statistically speaking, most people should be asleep by the time 30 minutes have elapsed since the machine was turned on. And because problems with sleep disordered breathing can start any time after a person falls asleep, they don't want the machine to be sitting a Ramp pressure for extended periods of time when it is likely the person is asleep, but their breathing has not yet been regular enough to meet the first criterium or irregular enough to meet the second or third criteria for the machine to meet the second or third criteria to end auto ramp.
Now it's also important to understand something else about what we mean when we say these machines can't really tell if we are awake or asleep without an EEG: Part of sleep disordered breathing is the body's response to the OAs and Hs: For many people, events come with arousals and mini-wakes that last 3-30 seconds. To further complicate matters, some people have spontaneous arousals that are not related to sleep disordered breathing, and these also can be as short as 3-10 seconds. These arousals and mini-wakes can be picked up by an EEG, but any change in the breathing pattern is too short to pick up (on the fly) and label as "Wake" with a high probability of certainty. People who look at lots of flow rate data can make intelligent guesses about what kinds of patterns in flow rate might be related to an arousal of some sort, but the auto algorithms and event tracking algorithms in APAP/CPAP machines don't label these as "wakes" because they're not programmed to try to tease out every arousal or mini-wake from just the flow rate data: Teasing them out with a reasonable amount of accuracy on the fly requires some additional data.
Now I don't have any personal experience with the F&P SensAwake algorithm to understand what it actually does. But from what's been posted by Rubicon and from what I have read, SensAwake is looking for at least a minute of what Rubicon called "Troubled Wakefulness", which is just another way of saying the breathing is clearly not good quality sleep breathing AND the breathing is not typical sleep disordered breathing. So there's a high probability that the person is either awake or drifting between wake and sleep without being able to establish real, continuous sleep. Again, if you look at lots of flow rate patterns, it's easy to make intelligent guesses about when a person is not sleeping well and the problem is not sleep disordered breathing. Around here, such periods are often called "sleep-wake-junk" of SWJ for short. But without the EEG data, you can't tell from the flow rate whether the person is awake for the whole period of time or is bouncing back and forth between wake and stage 1 sleep without making it to stage 2 sleep.
So my best guess is that SensAwake does a decent, but not fully accurate, job of realizing that something other than restful sleep is going on and that the "something" is not likely to be sleep disordered breathing. But whether the "something" is a real, genuine prolonged wake or whether the "something" is a restless period where the person is bouncing back and forth between wake and sleep is beyond what SensAwake is designed to do. Regardless of what that "something" is, the programmers of the SensAwake algorithm have made a decision that lowering the pressure (slightly?) should allow the person using the machine to more easily get back to a real, continuous, sleep rather than being stuck in a period of SWJ if that's what is happening at the time the "troubled wake" breathing has been going on long enough for SensAwake to kick in.
Finally, I will add this: CPAP/APAP manufacturers repeatedly say that machine reported AHI numbers are most important as trending data. They don't claim the overnight AHI is totally accurate every single night specifically because they know that the CPAP/APAP cannot determine the total sleep time (TST) with sufficient accuracy (as compared to a PSG). And they also know that the machine can flag certain events when a person is, in fact, awake. But the overall statistics indicates that there is sufficient accuracy in the data that for a typical PAPer if the long term machine reported AHI is substantially below 5.0, then the actual, real AHI (if it could be accurately computed) would also be substantially below 5.0. Likewise, there is sufficient accuracy in the data for a typical PAPer if the long term machine reported AHI is above 5.0, there is a high probability that the sleep disordered breathing is not yet being well treated by PAP. The assumption is that a typical PAPer does not spend exceptionally long periods of being awake while using the machine. In other words, the assumption is that a typical PAPer's sleep with the machine looks reasonably close to decent sleep in a person without sleep disordered breathing.
You've got to admire people who double down after being proven to be full of crap...ChicagoGranny wrote: ↑Fri Apr 07, 2023 2:35 pmStick with 'em. Too much emotional investment to back down now.
Very true. Unfortunately, medical and public health agencies and professionals often discourage patients from researching beyond surface level ad copy. [And quite a few doctors are content to rely on surface-level ad copy themselves.] In fact, during a recent pandemic we witnessed medical and public health agencies cooperating with federal espionage agencies, law enforcement agencies, big tech companies, big media companies, and even medical journal publishers in an effort to deny the public access to scientific research and debate that could have helped them gain perspective and make informed decisions.