Respiratory Wave Form correction, Bilevel vs EPR advantages - OSCAR data UK user

Hi all,

I have a question regarding my father and his respiration wave form and whether Bilevel would provide any advantage to normalize his breathing waveform. His monthly average AHI figures are around 3 AHI and with pressure setings of 13-17 has nights with AHI's below 1. There are times where the machine sits on maximum pressure and there are no apneas but there are flow limitations. Increasing max pressure further just seems to result in a worsening of performance figures.

He has clear inhalation phase and exhalation phase, but when breating in the daytime normally, during the inhalation phase its almost like he inhales in small steps. He has scoliosis and I believe that due to his small chest cavity and smaller lung capacity it causes a bit of physical limitation and weak muscles dont help to control his inspiration well. When using his CPAP machine, this is much less pronounced but still present a little bit which I believe is reflected in his OSCAR Data. You can see the uneven respiratory waveform and on the odd occasion during the inspiration phase, the breath goes below the zero line briefly. Only on very rare occasions does he have something that looks like a normal waveform.

I enabled EPR to see if that made a difference but when activated it makes his performance figures worse.EPR doesnt seem to help nor does it improve the respiratory wave form. I'm wondering if the reason for that is that machine registers some of the inspirations that go below the zero line as exhalations and therefore drops pressure for a very short moment within each breath in. Would these drops below the zero line be registered as expirations?

I read some other posts on here about Bilevel which suggest it is just a stronger form of EPR, however on other posts I see there are ways to adjust the duration and sensitivity settings relating to inhalation and exhalation on Bilevel machines.

My question is, with a bilevel machine is it possible to adjust the settings/sensitivity so it does not consider these "fake exhalations" and keeps a steady pressure going during the inspiration phase?

If suitable I would also like to find a UK bilevel supplier as I can see from reading posts on here, its not so easy to do.

Apologies in advance if any of my terminology is wrong as I am new to the board. Thanks.


Full night view


Respiration waves dropping below zero line


Most common respiration waves for a nights sleep


brief periods with some more normal looking respiration waves


another period with slightly more normal looking waves


Respiration waves examples


flow limitation and more erratic pattern


Flow limitation and typical breathing wave


a few normal waves

The primary purpose/aim of PAP for sleep is to lower AHI.

In this case, that may already be optimized to the extent that bilevel may not improve that significantly or at all.

However, two possible side-benefits of bilevel/autobilevel are added comfort and lessening the work of breathing.

You mentioned "weak muscles," so in my layman's opinion there is at least a possibility of some added benefit for added comfort and further optimizing quality of sleep and breathing. A ResMed autobilevel can have a set unvarying distance between IPAP and EPAP at a level that could make a real difference.

ResMed bilevel/autobilevel does have valuable customization features that can be dialed in for following breathing patterns. On the other hand, it may be impossible to know how likely it is that those parameters can be effectively optimized for an individual patient with a unique pattern of breathing unless that is tested with a trial. And it might sort of be considered an off-label-type approach for bridging between a sleep-treatment machine and a full-time breathing machine. Furthermore, the shape of the waveform alone, without specific accompanying quality-of-life symptoms, might make it a difficult argument for medical necessity.

My gut says it is worth a shot to see if autobilevel would be helpful. But that is just a guess by one untrained guy on the Internet, and it isn't my money and effort.

In the U.S., I would recommend that the expert eyes of an experienced Registered Respiratory Therapist be involved in (1) estimating possible benefits and (2) customizing the settings for the distance between IPAP and EPAP and the other settings. That level of help isn't always easy to get in any country, though. I am aware of only one set of eyes on this board that may have special insights on that deeper level. But others may also have some relevant opinions as well.

Thank you for the exemplary interest in providing good care for your father. May it go well.

A couple of footnotes to the excellent reply from lazarus.

If an expert can weigh in, I'd be curious whether there's an argument for trying an ASV machine rather than a vanilla bilevel machine.

I see that the median respiration rate is high; this leads me to think that the machine's algorithms do treat those dips below the zero line as exhalations.

Since it's a chart, describing the flow of air any flow under the zero line is, by definition an exhalation.
What we are seeing is exactly:

Egg Yolkeo wrote: ↑

Sat Sep 09, 2023 2:11 am

when breathing in the daytime normally, during the inhalation phase its almost like he inhales in small steps.

I don't know if this is a description of what the OP see when watching his dad, or when looking at the air flow on OSCAR while his dad is awake.

Either way, it seems to me that this is an issue for a thorough pulmonological workup. Not for dial winging.

lazarus wrote: ↑

Sat Sep 09, 2023 9:00 am

The primary purpose/aim of PAP for sleep is to lower AHI.

In this case, that may already be optimized to the extent that bilevel may not improve that significantly or at all.

You mentioned "weak muscles," so in my layman's opinion there is at least a possibility of some added benefit for added comfort and further optimizing quality of sleep and breathing. A ResMed autobilevel can have a set unvarying distance between IPAP and EPAP at a level that could make a real difference.

Thank you for the exemplary interest in providing good care for your father. May it go well.

Thanks for the helpful and kind comments lazarus.

His AHI is quite well managed on his current settings and in general it seems flow limitations seem to be the main thing that remains. I believe that is probably due to his postural issues due to his neck and curved back and small chest due to the scoliosis.

I think improving comfort and therefore quality of sleep would help, as like many people he doesnt find it the most enjoyable experience but is consistent in using it.

I am looking for a respiratory/sleep specialist who can assist/potentially prescribe a Bilevel machine along with any other advice.

Miss Emerita wrote: ↑

Sat Sep 09, 2023 12:03 pm

A couple of footnotes to the excellent reply from lazarus.

If an expert can weigh in, I'd be curious whether there's an argument for trying an ASV machine rather than a vanilla bilevel machine.

I see that the median respiration rate is high; this leads me to think that the machine's algorithms do treat those dips below the zero line as exhalations.

Thanks for your reply Miss Emerita. Going back through Oscar I can see his Median respiration rate is always around 26 to 27, with occasional nights at 25 at the lowest and 28 at the highest. I had seen the ASV machine on the Resmed Aircurve page and was wondering about that too.

ozij wrote: ↑

Sat Sep 09, 2023 9:50 pm

Egg Yolkeo wrote: ↑

Sat Sep 09, 2023 2:11 am

when breathing in the daytime normally, during the inhalation phase its almost like he inhales in small steps.

I don't know if this is a description of what the OP see when watching his dad, or when looking at the air flow on OSCAR while his dad is awake.

Either way, it seems to me that this is an issue for a thorough pulmonological workup. Not for dial winging.

Thanks for your reply Ozij.

To clarify my description is based on physically looking at my Dad sitting in a chair during the day time. When he is breathing the best way I cant describe is as follows:

Daytime breathing, unassisted:
Inhalation starts
Chest starts to expand
Pauses extremely briefly (fraction of a second)
Expands a little more
Pauses extremely briefly (as above) chest almost looks like it goes back in
expands a little more
Exhalation starts
process repeats.

Nightime breathing, CPAP assisted:
Looks much better than the above with a much more clear and noticable expansion and contraction of the chest cavity

If you ask him to take an big inhalation on his own, he really cant, its just one short breath lasting 1 second and thats him at his limit. He cant do one long slow and steady inhalation.

For reference he had heart surgery a couple of years ago and prior to his surgery they did a pulmonary assessment to see that he had sufficient lung capacity to undergo the surgery. The surgeon said there might be issues due to his scoliosis, but the test would clarify. I got him to use a breathing exerciser and do some posture work and he passed the test successfully. The surgery was successfuly and all his cardiac parameters are perfect.

Despite him passing those tests, having had Asthma and my own breathing problems in the past I can only make a layman's assessment but I believe is that due to his scoliosis combined with a kyphosis and associated poor neck posture and hunched over shoulders, his lung capacity/function is posturally limited in some way. The only other theory is that he may have had a mini stroke during the period when he developed heart problems.

Unofrtunately my dad is very resistant to investigations or treatment and it was a massive task to get him using his CPAP regularly, which thankfully he does. Other than doing postural work/exercise to improve lung function, I dont see there being any other avenue of treatment other than using some kind of machine to further stabilise/improve his breathing.

I'm no professional and no expert, and I too was wondering, like Ms. Emerita, whether an ASV would be a better solution.

Egg Yolkeo wrote: ↑

Sun Sep 10, 2023 1:51 am

I am looking for a respiratory/sleep specialist who can assist/potentially prescribe a Bilevel machine along with any other advice.

Good. I hope you find a good one soon!

Or maybe even an Aircurve 10 ST-A, with iVAPS and iBR, if CSA isn't involved--depending on experienced pro assessment and recommendations, of course.

https://www.resmed.com/en-us/ventilatio ... e-10-st-a/

lazarus wrote: ↑

Sun Sep 10, 2023 11:02 am

Or maybe even an Aircurve 10 ST-A, with iVAPS and iBR, if CSA isn't involved--depending on experienced pro assessment and recommendations, of course.

https://www.resmed.com/en-us/ventilatio ... e-10-st-a/

When he had his sleep study, there was no mention of Central sleep apnea, the conclusion was that he had moderate positional sleep apnea.

I did look at the Aircurve ST-A also, but not 100% clear on all the different funtions as I see there are various different versions of the Aircurve available. I looked at the functionality matrix from Resmed which helped to clarify, however I was slightly confused as for the Aircurve ST-A it says it doesn have Auto-adjust pressure for OSA events, but the product page refers to auto adjusting of pressure. I'm wondering if they dont show that as a tick on the grid because the pressure adjustment functionality is built into the iVAPS feature?

Egg Yolkeo wrote: ↑

Mon Sep 11, 2023 2:26 am

doesn have Auto-adjust pressure for OSA events,

It adjusts pressure to normalize other aspects of breathing, prioritizing those needs, while using CPAP, not Autoset, to address obstruction.

The good thing is that the pulmonologist and therapist would have a range of ResMed products to choose from once the "thorough pulmonological workup" that Ozij mentioned has been done. And traditional autobilevel, iVAPS, ASV, or other choices may all be possible contenders, depending on patient's priority needs. And if daytime breathing is also an issue, there might even be other choices for consideration, depending.

lazarus wrote: ↑

Mon Sep 11, 2023 6:01 am

Egg Yolkeo wrote: ↑

Mon Sep 11, 2023 2:26 am

doesn have Auto-adjust pressure for OSA events,

It adjusts pressure to normalize other aspects of breathing, prioritizing those needs, while using CPAP, not Autoset, to address obstruction.

I was reading about Scoliosis and CPAP and Resmed recommend the iVAPS function for this as they consider it a restrictive lung issue. My father is initiating his own breathing so it seems to suggest iVAPS would be more appropriate than ASV.

https://www.resmed.com/en-us/healthcar ... disorders/

Regarding the point the ST-A using CPAP and not Autoset, I'm not sure if I am understanding this correct, is pressure and pressure support two different things?

If you look in the iVAPS literature for the ST-A it Auto adjusts pressure support and lists that it increases and decreases pressure to meet requirements. This looks the same as what is in the Aircurve 10 Vauto Manual.

In the Titration settings for iVAPS mode you can only set EPAP but not IPAP, but you can set a minimum and maximum PS range. You can only set IPAP in the other operating modes.

The comparison of modes also shows no fixed IPAP but a varying range. To me this looks like iVAPS essentially works in an Auto Bilevel way in terms of adjusting pressures but with other more advanced functionality?

Is my understanding correct? I am trying to learn and understand the different technologies and terms so appreciate your patience.

Egg Yolkeo wrote: ↑

Wed Sep 13, 2023 12:37 am

pressure and pressure support two different things?

Pressure support (PS) is the distance between IPAP and EPAP.

In a ResMed autobilevel machine, you set PS as a constant. IPAP (breathing-in pressure) and EPAP (breathing-out pressure) can be thought of as locked together as those two pressures, always the same distance apart, vary together, according to the indications of what set of pressures best address the need to keep the airway stable.

On the other hand, with iVAPS, as I understand it as an untrained layman, you set EPAP for what the patient needs for comfort and stability, but IPAP varies so that the PS varies according to what the patient needs for the most effective breathing possible.

I have used a ResMed autobilevel; I have no experience whatsoever with iVAPS or ASV, other than being aware of the fact that they exist as modes of PAP that are particularly helpful to some with specific medical needs.

Figuring out how to prioritize the needs of your father in order to ascertain which mode of PAP would be most helpful to him would, in my opinion, require a pulmonologist-and-therapist team who could properly evaluate the present state of his breathing and what his future needs are likely to be if his condition and needs are likely to change over time. Specialized knowledge, diagnostic skills, and titration skills may come into play in a way that is beyond the sort of self-titration we help patients do here in this forum using OSCAR reports and the like for optimizing simple, everyday prevention of upper-airway narrowing and obstruction.

Restrictive lung issues and iVAPS are a completely different arena, one far beyond simple airway stability and good sleep.

lazarus wrote: ↑

Wed Sep 13, 2023 3:45 am

Figuring out how to prioritize the needs of your father in order to ascertain which mode of PAP would be most helpful to him would, in my opinion, require a pulmonologist-and-therapist team who could properly evaluate the present state of his breathing and what his future needs are likely to be if his condition and needs are likely to change over time. Specialized knowledge, diagnostic skills, and titration skills may come into play in a way that is beyond the sort of self-titration we help patients do here in this forum using OSCAR reports and the like for optimizing simple, everyday prevention of upper-airway narrowing and obstruction.

Restrictive lung issues and iVAPS are a completely different arena, one far beyond simple airway stability and good sleep.

Well said, indeed.
I’ve had two friends that wanted to self experiment with Cpap to address breathing problems that they felt were interrupting their sleep. Eventually both were determined to have varying degrees of pulmonary fibrosis. One of these friends is recently deceased.
This experience reinforces my preference that my friends work with their specialists to clearly determine that underlying causes of suboptimal breathing.
That experience

Tec5 wrote: ↑

Wed Sep 13, 2023 5:51 am

lazarus wrote: ↑

Wed Sep 13, 2023 3:45 am

Figuring out how to prioritize the needs of your father in order to ascertain which mode of PAP would be most helpful to him would, in my opinion, require a pulmonologist-and-therapist team who could properly evaluate the present state of his breathing and what his future needs are likely to be if his condition and needs are likely to change over time. Specialized knowledge, diagnostic skills, and titration skills may come into play in a way that is beyond the sort of self-titration we help patients do here in this forum using OSCAR reports and the like for optimizing simple, everyday prevention of upper-airway narrowing and obstruction.

Restrictive lung issues and iVAPS are a completely different arena, one far beyond simple airway stability and good sleep.

Well said, indeed.
I’ve had two friends that wanted to self experiment with Cpap to address breathing problems that they felt were interrupting their sleep. Eventually both were determined to have varying degrees of pulmonary fibrosis. One of these friends is recently deceased.
This experience reinforces my preference that my friends work with their specialists to clearly determine that underlying causes of suboptimal breathing.
That experience

Thanks to you both and appreciate your concerns,I come from a technical background and have a inquisitive mind so like to learn and understand things. I do realise however this is an incredibly complex subject. Its not really possible to experiment with IVAPS or ASV as these units are not sold or available on the UK market without direct supply via the national health service or a private sleep specialist (probably to stop people experimenting) Only CPAP machines can be bought directly and only with a sleep study report which my father has.

As it can take years to get access to sleep specialists on the national health the private route will be the only option.