Maybe I have apnea, maybe not, are all sleep doc jerks?

[Sleeprider]

ASV is for central and complex apnea. All you would want is the VPAP auto, which is a straight bilevel machine without backup rate, but all the PS you want. FWIW, there is a Resmed Aircurve 10 Vauto for sale in Berwyn (near Chicago) for $200. Note the seller advises the machine smells like room deodorizer which could be masking something else.

ResMed Aircurve 10 Auto BiPAP - $200
Selling a used ResMed Aircurve 10 Auto BiPAP with built in heated humidifier
Includes used clean water chamber. used clean heated hose, data card, power supply. Has a total of 1,137 hours. But does have an odor like room deodorizer or scented candles. Very clean works fine.

[SarcasticDave94]

Yeah ASV that is targeted for CA would not feel right or actually be right. If you don't care for variable air via EPR 3 you'd hate this.

Look up those used BPAPs. They sound much better suited.

[2SleepBetta]

cathyf,

Your skill set, interest and health concerns connected with UARS have motivated highly enlightening analyses, discussion and far more thinking about flow limited breathing than is evident in what we see from sleep medicine. Thank you for your presentations and discussions of detail and for your dogged persistence. 

Kudos to SleepRider, Gideon, Dave and others for their informative, on-target airflow diagnoses. My used VAuto that got rid of most all my high-density of FL is still set very close to how SR directed me to set it up  a couple of years ago. It was clear, reading here back then, that the VAuto was the way for me to go with flow limitations. Here's hoping it will do wonders treating you.

You have a good idea of what to do next. You (we with flow limited but--often?-- low AHI breathing) need to do all we can to save what health we have by overcoming our still flow-limited breathing as much as possible--that with little to no help from sleep medicine.

You wrote of trying to discern exactly what an indication of FL meant. Why is it positioned on the time line as it is, etc. I send you the image below as fodder for your consideration in studying flow limits in general.  There are two small isolated instances of FL and  seven fairly regular preceding breaths for each of the "M-tipped" inspiratory flows. Those tips are typically followed by a FL that begins during exhalation after the M-tip. I stared at the image a while and kept wondering (again as often) how many breaths or how much time is considered in the algorithm to determine the height and breadth (scale values) of the FL.  and its positioning on the time line.

Keeping it in mind that the highest flow rate is at the top of rounded tips, and keeping it in mind that a FL flag signifies a change in volume of air being delivered in a relative block of time, it's interesting to see that about three of the more normal tips just preceding each of the M-tips illustrate why the earliest FL marker is much larger than the second one; there was a much greater decline in volume. Lots of headscratching stuff here, not to mention wondering why it has always seemed to me that the total reduction in volume "chunk" was caused mainly by the rate reduction in the crotch of that one half wave.  

   

Anyway, if you care to, see if any of this can contribute anything to your effort to increase all our understanding ('am hoping it adds no confusion).

[cathyf]

2SB -- it's certainly a learning experience! I think that I'm only now really getting that my airway is simply narrow, and everything is less forgiving and less margin of error.

I'm still kind of mystified by how my machine works some of the time...

Here's an example of what I mean. This is a 5-minute little cluster on the night that I tried out the 2-1/2-inch high cervical collar, which is just not tall enough. Those 5 breaths leading into the first OA the FL goes 0.13, 0.14, 0.11, 0.20, 0.21. Then I crash into that first OA, which is 29 seconds long. The Flow Limitation value continues at 0.21 through the end of that first OA. Exit the OA with a little snore (0.11->0.14) that cuts out right where the machine takes the FL down to 0.00. While that snore is going on between the first 2 OAs, the FL score goes from 0.21 to 0.17 to 0.04 to 0.00. And the pressure drops with it. That next breath gets halfway up to the ~20 that the other breaths are getting to, the pressure turns around and rises again, and then the waveform collapses into a 39-second apnea. There is actually a 0.02 snore that starts right there at 23:11:17 and ends as the OA ends at 23:11:59. Exit the apnea with another little snore, and the pressure starts dropping. A couple of not-bad breaths later -- although there are tiny 0.02 snores popping in there -- the machine figures out that I'm still in trouble with that next apnea. That one is only 11 seconds long, it is not as completely obstructed, and, quite interestingly, the process of going in and out of that OA doesn't clear the FLs.

Note that I have made the Flow Rate graph quite tall in order to see detail. What I see that is so characteristic of my breathing is that -- except for the couple of breaths after the obstructions -- those inhales top out right about 20, and the exhales bottom out at about -30. When I've seen other people's pictures, their inhales and exhales just get more speed than that.

A couple of questions:

1. Are the big breaths/snores after those first two OAs microarousals?
   
2. With that third OA, that looks to me like an event that would be scored as a hypopnea using the 90% rule that my sleep lab uses, while the machine calls it an apnea because it's using an 80% rule. Does that look right?
   
3. While the first two OAs end with a bang, the third OA goes out with a whimper -- and a butt-ugly 0.39 FL. (I'm bemused by the last breath in the shot, where it looks like my airway is giving me the finger. Kinda sums it all up, eh?) Is the difference that there was NOT an arousal?
   

[attachment=31381]

And you see what I mean about how the machine's reporting of FLs skews the FL statistics to be much lower than they really are? It looks to me like a combination of factors. First the machine is way too optimistic about when it can stop reacting to events. But even more important, I think the machine just doesn't report some of what it's reacting to, which makes things rosier than they are.

Ok, that's enough questions for now... (I'm out of attachment space anyway!)

[Sleeprider]

A couple of questions:
Are the big breaths/snores after those first two OAs microarousals?
With that third OA, that looks to me like an event that would be scored as a hypopnea using the 90% rule that my sleep lab uses, while the machine calls it an apnea because it's using an 80% rule. Does that look right?
While the first two OAs end with a bang, the third OA goes out with a whimper -- and a butt-ugly 0.39 FL. (I'm bemused by the last breath in the shot, where it looks like my airway is giving me the finger. Kinda sums it all up, eh?) Is the difference that there was NOT an arousal?

Generally, an increased respiratory volume following increasing flow limitation is "RERA", respiratory effort related arousal. This is clearly recovery breathing and a signiificant arousal that kept you breathing. Based on history, I'm guessing positional.

The third OA actually qualifies as an OA. Even though there is still flow, it is less than 30% of the preceding 90 second tidal volume, so OA. We don't have oximetry data, and most clinical hypopnea is based on 3 or 4% O2 drop. It's a stupid criterial to serve insurance. The event is significant.

The graph is giving you the finger, but it is the airway resistance that won. Bilevel will change your life, and don't expect the doctors to understand.

[SarcasticDave94]

In cases like most CPAP therapy, the way to get what you need is either complain with symptoms until their ears and eyes bleed or you'll be forced to buy your own if you're financially able.

[2SleepBetta]

Good to see SR weigh in again, a learning opportunity for most all of us, certainly me. I checked, saw your questions and knew most all of them would fry my grey matter--hard stuff, but was wanting to think about it although committed to another matter now.

Still, many of your questions remain about what scored flow limits (FL) are exactly: their timing, durations, scale values, look back windows, etc., and, further and more importantly, how all those relate to the FR curve's messages. 

Additional good info might be gleaned from the ResMed patent application that is linked to my thread in Post 1. The ResMed goal is to raise the quality of FL detection and FL information, so the piece may put some light on how the Autoset handles FL.  There are helpful figures and a lot of relevant text after them, including info on how other manufacturers' and ResMed's other patents relate to the new approach.   

US020180272088A120180927 (storage.googleapis.com)

[cathyf]

Generally, an increased respiratory volume following increasing flow limitation is "RERA", respiratory effort related arousal.  This is clearly recovery breathing and a signiificant arousal that kept you breathing.  Based on history, I'm guessing positional.

Right, this was a night where I was wearing the small cervical collar, so it wasn't enough -- so chin tuck for sure.

Ok, can we come back and I can ask about RERAs? That pattern where I come out of an OA with a burst -- recovery breathing -- I do that probably 75-90% of the OAs that I have looked at in OSCAR. And I have a lot of them sprinkled along my Flow Rate graph even when I'm not having events. When I had my sleep study last November (the one where I had an AHI of 2 and they told me to stop using my CPAP) they recorded the numbers this way:

Code:

  Respiratory Index                #Events          Index
Apnea/Hypopnea Index (AHI):               12        2    
Respiratory Disturbance Index (RDI):           21        3
Obstructive Apnea/Hypopnea Index (OAHI):       11        2
Respiratory Effort Related Arousal Index (RERA):    9        1
Total Apnea Index:                    3        0
Central Apnea Index:                    1        0
Hypopnea Index:                        9        1

 Arousals Summary    Total #          Index
Arousals-Spontaneous       33        5    
Arousals-Resp Events        9        1
Arousals-Leg Movements        0        0
Arousals-Total           51        8
Total # of Awakenings       13        2

 Positional    Total       Supine      Lateral
AHI           2        7         2
nREM AHI      2        7         1
REM AHI           3        0         3
RDI           3       26         2
nREM RDI      3       26         2
REM RDI           3        0         3

While the one last week looked like this:

Code:

  Respiratory Index                #Events          Index
Apnea/Hypopnea Index (AHI):               106        18    
Respiratory Disturbance Index (RDI):           106        18
Obstructive Apnea/Hypopnea Index (OAHI):       106        18
Respiratory Effort Related Arousal Index (RERA):    0         0
Total Apnea Index:                    0         0
Central Apnea Index:                    0         0
Hypopnea Index:                       106        18

 Arousals Summary    Total #          Index
Arousals-Spontaneous        16         3    
Arousals-Resp Events       106        18
Arousals-Leg Movements         0         0
Arousals-Total           122        21
Total # of Awakenings         9         2

 Positional    Total       Supine      Lateral
AHI           18        13        39
nREM AHI      16        11        39
REM AHI           42        42         0
RDI           18        13        39
nREM RDI      16        11        39
REM RDI           42        42         0

I'm just confused as to how they are scoring what? How could I have 106 "Arousals-Resp Events" but zero RERAs in April? In November, the RERA was 9 events for an index of 1 per hour, and the "Arousals-Resp Events" was also 9 events for an index of 1. Is there some typo somewhere? Here are the technical specifications:

Apnea: A drop in the peak thermal sensor excursion by 90% or greater of baseline, a duration of at least 10 seconds, and at least 90% of the event's duration meets the amplitude reduction criteria.
  Classifications:

1. Obstructive apnea: Meets apnea criteria and is associated with a continued or increased inspiratory effort throughout the entire period of absent airflow.
   
2. Central apnea: Meets apnea criteria and is associated with absent inspiratory effort throughout the entire period of absent airflow.
   
3. Mixed apnea: Meets apnea criteria and is associated with absent inspiratory effort in the initial portion of the event, followed by resumption of inspiratory effort in the second portion of the event.
   

AASM Hypopnea rule 1A: A 50 % or greater fall (but less than 90%) in the nasal pressure signal excursion for at least 90% of the event duration from pre-event baseline, the duration of which lasts at least 10 seconds, and is associated with a 3% or greater desaturation or EEG arousal and continued or increased inspiratory effort throughout the entire period.
AASM Hypopnea rule 1B: A 30 % or greater fall (but less than 90%) in the nasal pressure signal excursion for at least 90% of the event duration from pre-event baseline, the duration of which lasts at least 10 seconds, and is associated with a 4% or greater desaturation with continued respiratory effort.
Respiratory Effort Related Arousals (RERA): A sequence of breaths lasting at least 10 seconds characterized by increasing respiratory effort or flattening of the nasal pressure waveform leading to an arousal from sleep when the sequence of breaths does not meet the criteria for hypopnea or apnea. With respect to scoring a RERA the preferred methods for assessing change in respiratory effort are nasal pressure and inductance plethysmography.
Apnea Hvpopnea Index (AHI): The mean number of apneas, hypopneas per hour of sleep
Respiratory Disturbance Index (RDI): The mean number of apneas, hypopneas and RERA's per hour of sleep.
Arousal: We score an arousal during sleep if there is an abrupt shift of the EEG frequency including alpha, theta and /or frequency greater than 16 hz (but not spindles) that lasts at least 3 seconds, with at least 10 sec of stable sleep preceding the change. Scoring of arousals during REM sleep requires a concurrent increase in chin EMG lasting at least 1 second.
Arousal Index: Mean number of arousals per hour of sleep calculated by the number of arousals X 60 divided by the total sleep time (TST). We may further specify what caused these arousal (e.g. respiratory events, periodic limb movements, etc.)
Awakening: When more than 50% of a 30-second epoch is scorable as wakefulness and was preceded by at least 10 seconds of sleep.

Color me confused? There is some odd relationship between arousals which are respiratory but not apneas/hypopneas? Looking at the April study, I had 106 Obstructive Hypopneas and NO other events? And I had 106 respiratory arousals -- presumably one for each hypopnea, but none of those counted as a RERA because it's not an RERA if it was already scored as an event.

Compare to November, when I had 1 Central, 2 OAs, 9 hypopneas, and 9 RERAs. But I only had 9 "Arousals-Resp Events" -- those had to be the nine RERAs, but that means that none of the hypopneas or apneas resulted in an arousal? And another thing that doesn't add up -- it says 33 spontaneous arousals, 9 resp arousals, but 51 total -- if the typo is that there are supposed to be 18 "Arousals-Resp Events" (9 from the 9 RERAs and another 9 from 9 of the 11 Obstructive apneas/hypopneas, then 33+18=51. (And the fact that the hypopneas equal the RERAs exactly is just a coincidence, and the coincidence is what caused the brain fart on the technicians part that resulted in the typo.)

So the November numbers would make sense with a correction to "Arousals-Resp Events" from 9/1 to 18/2 -- and looking at the AHI vs RDI it looks like those 9 RERAs all must have happened in my brief turn on my back. And that's believable -- 9 RERAs + 12 Ap/Hyp is the same order of magnitude.

But that makes the April numbers look really weird -- I had 106 instances of sleep-disordered breathing that progressed as far as an Obstructive Hypopnea, but not a single instance that fell short of a hypopnea but caused an arousal? AND ALSO -- not a single instance that went further than a hypopnea to get scored as an apnea?

In November, small numbers but sprinkled across all four categories -- 1 CA, 2 OA, 9 Hyp, 9 RERAS -- and most but not all caused arousals.
In April, a BIG number, but every single one in a single category -- hypopneas -- and every single one caused an arousal -- BUT there were no other respiratory arousals? That's just doesn't make sense...

[cathyf]

Bilevel will change your life, and don't expect the doctors to understand.

I don't have a huge data sample of sleep with EPR -- but what I do have suggests that pressure support of 3 doesn't really look different from no pressure support. Is it still possible that a larger pressure support will make a world of difference?

The thing that I have been struggling to understand over the last 6-1/2 years is that this is what I seem to see:

1) tuck my chin: moderate/severe apnea, with the events punctuating a background of continuous ugly flow limitations. It doesn't matter what pressures I use, what EPR, the machine just helplessly watches and can't help

2) keep my chin up: continuous ugly flow limitations and  arousals as long as I'm asleep. Again pressure and EPR don't seem to matter. The machine chases the flow limitations all night with pressure if I let it, or if I set the pressures low it pegs at whatever the max is. But whether I let the pressures change or not, lots of flow limitations but very low (under 0.5) AHI.

All along I thought I was just your pedestrian CPAP success story, but now I'm wondering if the machine can't do anything but watch. And yes while I can fix the AHI with the cervical collar, I'm still having continuous flow limitations. And with the flow limitations, it's worse than "nothing to do but watch" because it's not even very good at watching -- the machine actually misses half the FLs that I can see are there!

[happydreams]

As a relatively new Vauto user, (6 months) I have to agree with Sleeprider...  

PS helps a lot.  Especially in the parts that are not reflected in your "score".  Although, I'm still a "work in progress" I feel a lot better with the extra PS afforded by the VAuto.  I have lots of micro-arousals and unflagged flow limits.  And the truth be known, the VAuto doesn't always seem to do what I'd expect.  But on average, I am doing a lot better, in my overall well being.  Headaches way down, daytime drowsiness non-existent, motivation, way up, quality of life greatly improved.

In the end, it's not the score that counts, or even the flow limits, but how you feel.  I feel tons better with the VAuto, better than I have felt in 5 years.  The VAuto seems to have enough knobs to tweak in a therapy that seems to work for me.  If you can, I'd encourage you to somehow get a VAuto.