Auto CPAP vs. Auto BiPAP

[vsheline]

I will probably get the auto BiPAP. Pay for it myself. What settings should I consider (max IPAP, min EPAP, max PS)? What flex settings should I consider?

Hi Apnea 1, welcome to the forum!

Your prescribed settings are:

On a straight bi-level machine (non-Auto):
EPAP: 12
IPAP: 18
Bi-Flex: 0 or 1 or 2 or 3
(Bi-Flex only affects the abruptness/gradualness of the pressure changes, it does not make the EPAP lower. Patient should adjust it to whatever is most comfortable.)

If Auto bi-level machine but adjusted to act like a straight bi-level:
Min EPAP: 12
Max EPAP: 12
Pressure Support: 6
Max IPAP (or Max Pressure): 18
Bi-Flex: 0 or 1 or 2 or 3

If Auto bi-level machine with EPAP adjusted for a range:
Min EPAP: 12 or lower (i.e., 10)
Max EPAP: 12 or higher (i.e., 14)
Pressure Support: 6
Max IPAP: Max EPAP plus Pressure Support (i.e., 14 + 6 = 20)
Bi-Flex: 0 or 1 or 2 or 3

The PRS1 BiPAP Auto and ResMed S9 VPAP Auto are both optimal machines for treating obstructive sleep apnea.

During bi-level titrations, the technician is supposed to increase Pressure Support until all RERAs are eliminated (but sometimes the technician does not know to do so, or sometimes does not have enough time to do so).

Respiration Effort Related Arousals (RERAs) are arousals which are not necessarily accompanied by hypopneas or apneas, so your AHI may be small or even zero but you may be having additional RERAs which are keeping you from achieving the stage of deep restful sleep.

So even though a CPAP at 14 may eliminate all or most hypopneas and apneas, your sleep quality may be much better with bi-level therapy with Pressure Support adjusted to 6, if the bi-level therapy is able to eliminate all RERAs.

I have appended below (from another forum) a very long post by Dr Barry Krakow concerning bi-level treatment.

Take care,
--- Vaughn



bilevel = two levels
PAP = Positive Airway Pressure therapy or machine
CPAP = constant PAP machine
APAP = automatically self-adjusting PAP machine
BiPAP = bilevel PAP machine or therapy
VPAP = name of ResMed brand of BiPAP machine
OSA = obstructive sleep apnea
SDB = sleep-disordered breathing, of which OSA is one type
AHI = apnea/hypopnea index (number of events per hour, of apnea (no-breathing) or hypopnea (too-little breathing)
UARS = Upper Airway Resistance eventS
RDI = number per hour of apneas + hypopneas + UARS
IPAP = pressure on Inhalation
EPAP = pressure on Exhalation (same or lower than IPAP)
titration = the process of finding the proper pressures for PAP


I read through some other posts on UARS, and frankly, I'm disturbed by a number of comments from individuals who may be inadvertently providing misinformation to this forum.

Having trained with the pioneer researcher Dr. Christian Guilleminault who discovered UARS, I wish to make a few comments that might help PAP therapy users optimize their responses to find high quality sleep.

A reminder that for all practical purposes, the following three terms are interchangeable:

· UARS (upper airway resistance)
· FL (flow limitation)
· RERAs (respiratory effort-related arousals)

UARS as Mini-Suffocations

First and foremost, let's look at an analogy in cardiology to put to rest the nonsense that UARS does not exist or is somehow not important. We all know that asystole (heart stops) is bad, just as we know apnea (breathing stops) is bad. But, in cardiology, for decades we've known there are many other cardiac arrhythmias producing irregular heart rhythms, and we don't sit back and say, "well it's not asystole, so it must be OK." For decades, unfortunately, that practice is in fact what many physicians were taught or conditioned to believe, "it's not apnea, so it must be OK." Indeed, to this very day, I still see patients who have been to sleep doctors who told them their sleep study was OK because it didn't show apneas.

But, as we like to say, “a little choking is still choking,” therefore I think it is reasonable to state that each of the various forms of sleep-disordered breathing (apneas, hypopneas, UARS) reflects some degree of “suffocation.” Apnea is the most concrete form as the patient awakens choking or gasping, whereas UARS is probably equivalent to a “mini-suffocation,” which while asleep I imagine produces an unpleasant sensation but not choking.

UARS is not Mutually Exclusive of Hypopneas or Apneas

Please appreciate then that UARS is simply on the continuum of breathing events. To complete our analogy, UARS represents a more subtle form of breathing irregularity (or as some say pulmonary dysrhythmia). It is not mutually exclusive of apneas or hypopneas. You can have all three types of events when you are diagnosed with sleep-disordered breathing (SDB). In fact, the most common type of SDB shows all 3 components in varying proportions during the sleep study.

You would think though that apneas are more important than UARS events, right? Well, maybe. Don’t forget that UARS events, like apneas, are also frequently associated with sleep fragmentation and therefore unequivocally associated with daytime sleepiness and fatigue. We have seen patients with severe UARS (e.g. RDI > 40), who unequivocally have more sleepiness than say a patient with a moderate degree of apneas and hypopneas (AHI =20). That is why RDI (apneas + hypopneas + UARS) is more valuable when diagnosing and treating your condition than AHI.

To repeat, it is critical to realize that nearly all patients with OSA also have a UARS component on their diagnostic sleep studies, but if the sleep lab doesn’t use the proper respiratory sensors, they will not see it: "what you don't look for, you will not see!"

UARS Assessment and Treatment is Critical to Titration Success

Still more importantly, when a titration is conducted, UARS is invariably present, because the pressurized airflow doesn’t work like a magic wand to suddenly make apneas disappear. Apneas are often turned into hypopneas as the pressure is increased. Then hypopneas turn into UARS or as more commonly called in the lab nowadays “flow limitation.” Remarkably, many sleep lab techs do not push forward with the titration at this point, believing that their job is done. Even some proportion of sleep medicine physicians do not mandate that their sleep techs increase pressure for flow limitation.

“Consensus Medicine” Covered up The Science of UARS

How anyone would think UARS doesn't exist or isn't important probably relates to the sometimes misguided concepts of "conventional wisdom" and "consensus medicine" and how such processes frequently retard scientific discoveries from finding their way into community medical practices. In the early 1980s, papers were published about sleep apnea, then Medicare got on board to accept and cover the condition, after which a new CW was born that's taken quite awhile to revisit.

Once physicians and patients became accustomed to hearing the words "sleep apnea," it was only natural that people would block out any other pictures about the nature of a sleep breathing disorder. A consensus formed: either you stop breathing or you don't! Black and white, eliminate the gray! Which is why we always return to the heart rhythm analogy to help people understand the need to monitor different breathing irregularities, not just apneas.

I have treated thousands of patients with UARS who had either no apneas or hypopneas or an AHI less than 5. Nearly all these patients suffered sleepiness or fatigue from their conditions, and many suffered from insomnia and nocturia. Among those who were able to successfully use an appropriate SDB treatment (e.g PAP therapy, oral appliances, nasal strips, nasal surgery, nasal hygiene and so on.), virtually all achieved clear-cut improvements in their symptoms.

What’s in a Name?

In most of my UARS cases, the patients would almost invariably start the discussion with, “so, you don’t mean I have sleep apnea do you?” Which is interesting, because if you follow the workings of the American Academy of Sleep Medicine, you’ll notice their strategy is to abandon the word UARS, and simply declare that UARS equals sleep apnea. In their lexicon, they would answer the UARS patient as follows, “yes, you have sleep apnea, oh but by the way, you don’t stop breathing.” See the problem? That’s why I continue to use the term UARS to make it clearer to the patient.

As an aside, I’ve seen cases where the UARS was ridiculously subtle (I was almost too embarrassed to call it UARS) or it only appeared in REM sleep. I had to inform these patients that I was skeptical about whether PAP therapy would make any difference. Although I still encouraged this particular subset of patients to give PAP therapy a chance, no more than 50% were willing to try it. Yet, in several cases, some of these patients reported dramatic and sustained (as in years) improvements in fatigue or sleepiness with PAP therapy. Undoubtedly, we find these events very perplexing, but the upshot appears to be that sleep assessment technology for measuring respiration and arousals has a long way to go….but then most of you knew that already!

Start Connecting Some Zzzzzots

Along these lines, let me mention a working theory we have developed about UARS and why bilevel might be the best option for its treatment.

The most salient factor during most titrations is how well the patient responds during expiration. Think about it: it sure feels a lot easier if not pleasurable to breathe in with pressurized airflow coming into your lungs. Many SDB patients are immediately hooked on PAP therapy because of this singular experience.

But breathing out against pressurized airflow is a completely different experience for a very large proportion of patients. After all, it’s downright weird to breathe out when pressurized air is coming in. And, that’s exactly how many people describe it and worse. It’s weird, anxiety-producing, claustrophobic, and triggers a sense of panic. Now, the biggest question is who are the types of UARS patients
that would feel so negatively about exhaling on PAP therapy?

In our clinical and research experience, it would be someone who already has some degree of anxiety, a lot or a little, it may not matter, because once they try to use fixed CPAP in particular, they quickly report that it’s very uncomfortable or worse, they report feeling more anxious.

In a large proportion of these patients, we switch them to bilevel during the pre-sleep desensitization/adaptation period, and remarkably, we have found that 90% of these patients report immediate relief by virtue of the lower expiratory pressure.

Note: Bilevel combines IPAP (pressure on Inhalation) and EPAP (pressure dropping on Exhalation).

Can You Feel Anxiety in your Sleep?

Although we have more recently discovered that most patients want to switch to bilevel during the desensitization, that is, before the formal titration begins, we didn’t really figure out this point until we watched UARS patients while asleep. That’s when we saw that they did not like CPAP, that is, a fixed pressure on exhalation. That’s when we saw the ratty looking signal suggesting they were having some kind of anxiety or otherwise unpleasant response to air coming in while they were trying to breathe out.

In my opinion, which I don’t think is shared by the majority of sleep docs, anxiety is experienced while you sleep. If you can experience anxiety in dreams, I don’t see why you can’t experience anxiety to pressurized airflow in your sleep. So, in a nutshell, I think that’s why CPAP doesn’t work well in UARS patients and for that matter, I don’t think it works well in most SDB patients except for truly classic hypersomnolent, anxiety-free, sleep apnea cases.

I think anxiety is already present in the majority of SDB cases, because it is an anxiety-producing experience to breath abnormally all night long. That is, anxiety and breathing are intimately connected, so most SDB patients are more or less conditioned to be more nervous in general by having spent the night not breathing well. Now, introduce a foreign stimulus, CPAP, which then triggers or worsens anxiety by the introduction of an extremely foreign sensation: pressurized airflow forced inward during exhalation.

Is Bilevel the Answer?

Why bilevel works so well is still a puzzle. But, what’s so intriguing is that the subjective and objective findings match. That is, nearly all patients who switch from CPAP to bilevel state that it is easier (subjectively) to breathe out with bilevel. And, during their titrations, the ratty airflow signal disappears on expiration (objectively) and is replaced by a smooth and rounded curve indicating normal expiration.

Should you be able to produce the same results with CFLEX, APAP, etc? Presumably so, except for one “large” difference. You cannot generate the same gradient or gap between IPAP and EPAP with any of the other devices. And, in our clinical and research experience, we are using gaps of 4 to 12 cm of water in our patients. My personal bilevel settings are 21/12.5 for a gap of 8.5.

In our prescriptions for bilevel, I would venture that the average gap is in the 5 to 6 range with tremendous variation, including some with a gap of only 2 or 3. Those with a lower gap requirement would likely do as well on FLEX or APAP, but to repeat, the large majority of our patients have a gap of 4 or greater.

Still, it would be nice to have a respiratory physiologist explain to us why the larger gap is so effective. As an internist and sleep medicine physician, there are only two obvious theories that stand out. First, what if we’ve always assumed, mistakenly, that airway pressure had to be constant for both inspiration and expiration? I think it has already been proven by other researchers that you actually need higher pressure to keep the airway pinned open on inspiration and a lower pressure on expiration. If that’s so, then is bilevel the best system because it provides the exact pressure you need (not too much and not too little) during expiration.

The second idea relates more to the psychophysiological response to PAP therapy. Maybe the larger gradient simply gives the patient a distinctly more comfortable feeling, because the lower pressure creates a feeling so much closer to breathing normally (without PAP). If this theory were accurate, though, it would imply that over time as you get used to any sort of PAP therapy, then perhaps the gap would narrow and eventually you could use fixed CPAP again. If this were true, I would expect more people to eventually adapt to fixed CPAP pressure, and I don’t believe that’s occurring.

UARS Diagnosis and Medicare

Last, insurance coverage for UARS is always a hot topic. This section is not relevant to titrations, because nearly everyone manifests UARS on the titration. Insurance questions revolve around the diagnostic study: does the patient “only” have UARS?

In Albuquerque, I have pushed back on this issue for more than a decade, and the results have been tangible and somewhat satisfying. At this point, there are only 3 insurance carriers in New Mexico who do not cover treatment (specifically, PAP therapy or oral appliances) for UARS. Even among these 3 carriers, we can always make an appeal on very specific comorbidities (e.g. a UARS patient who has had 2 car accidents in the last year), then Medicare might decide to cover such a UARS patient.

In the beginning of this particular journey, I found it frustrating at first, but it was also an opportunity to educate medical directors at insurance companies. We would routinely call these individuals, send them research publications, and explain how UARS was going to cost them more money in the long-run if they didn't cover it.

As an aside, I have to mention how frustrating and disappointing it is to hear about sleep physicians who might make their decisions about UARS based on insurance considerations. I was never trained to think that way in medical school, and it approaches unethical behavior in my opinion. If a patient is diagnosed with UARS, that's the diagnosis whether it's covered by insurance or not. Insurance companies don't tell me what I can diagnose and they don't tell me how to treat my patients!

Financial considerations are relevant and important, but they have nothing to do with my patient advocacy and my duty to inform the sleep patient of the diagnosis and treatment plan we recommend.

I am deeply perplexed by the notion that a sleep physician would withhold this information from a UARS patient because the insurance company wasn't going to cover it. As before, it borders on unethical behavior, in my opinion.

Summing Up

Last and not least, UARS is one of the primary reasons that many SDB patients do not achieve an optimal response. As I describe at length in my book, it is a human tendency to "normalize" behaviors, which over time prevents us from obtaining the best possible response to PAP Therapy. If you are so used to fatigue and sleepiness, having suffered for so many years, then how could you possibly discern what a normal level of sleepiness and fatigue should be? Instead, (and I know this from my own trials from CPAP to APAP and finally bilevel), when you experience some improvement, the tendency is to create a new "normal" and wrongly assume that this is "as good as it gets."

Well, it's not as good as it gets if the UARS component of the SD hasn't been treated, because there is still more to treat. Undoubtedly, most of the members of this forum recognize the fine-tuning and tweaking that's needed to manage mask leaks, mask comfort, mouth breathing, humidifier settings, and nasal congestion, just to name a few of the issues that must be regularly attended to enhance the PAP response.

Notwithstanding, in my clinical experience, I have found that resolving the UARS component of SDB is in the top tier of factors that frequently must be addressed to achieve optimal results, especially so among patients whose regular use of PAP therapy has not yielded the desired effects.

I've lived through this problem and I've breathed through it, and no other single factor enhanced my sleep quality to the level I currently enjoy and am eternally grateful for experiencing.

Surely, this is something to sleep on. I do, night after night.

P.S. Sorry for the long post; but it's not my fault, it's the bilevel. After 7 near perfect hours of sleep quality last night, I had to do something to burn up the energy.

Editor's note:
Here are Dr. Krakow's responses to posters:

Some Responses.

1. Correct Pressure. Great point. I don't think I've seen one patient in the last 3 years where I was convinced we found the "perfect" pressure on the first titration. At our center, the norm is retitrate patients at least two more times in the first year. And, among my colleagues at the annual sleep society meeting, I hear more sleep docs moving in the same direction.

2.Initial Response Followed by UARS Emergence. This was one of the first clues to the problem of titrations in general and UARS components in particular. Many patients reported this initial great response, lasting a few weeks or months, and then a gradual or sudden deterioration. When they returned to the lab, the pressure needed to be raised to eliminate "new" or "emerging" UARS. I'm of the belief that it is nearly impossible to get a perfect titration the first time, because the body needs to go through many adjustments. Having adjusted, the pressure almost always needs to be raised or lowered. At Stanford, the model in 1993 was full night diagnostic, followed by full night titration, and then retitration 30 days later.

3. Good FL numbers. It's not so much good numbers; it's normalized airflow, because it is not so easy to count UARS events. Still, you can find a way to count flow limitation events, and you certainly want to reduce them as much as possible. There are data from Rapoport's group that suggests that an RDI consisting only of UARS (FLs, RERAs) in the range of 15 to 20 is clinically significant, so a number lower than this level should be and usually is the minimum to shoot for. In our lab, we occasionally get some patients below 5, but it's the lab environment, which I think in and of itself prevents the "perfect" titration.

4. Ideally, zero. Yes, zero is ideal, and we certainly like to see patients approach "normal." Does everyone realize that a normal sleeper's airflow curve is identical to an SDB patient who is getting a great response on PAP Therapy?

5. Snoredog's Frustration. Please forgive me, but you're setting me up to say that the answers to most of your questions are provided in my new book, Sound Sleep, Sound Mind [commercial link URL removed per Apnea Board rules], so thanks for the plug (Ha! Ha!). However, let me add that if you think you're frustrated about this information not being disseminated, can you imagine how I feel? And, compared to the 2 of us, can you imagine how Dr. Guilleminault feels? It goes all the way back to 1982 when he discovered UARS in children.

As I indicated above, "conventional wisdom" and "consensus medicine" routinely retard the dissemination of information into the sleep medical community. If you haven't read Malcolm Gladwell's The Tipping Point, I think you'll get a big kick out of his perspective on how things stick and then spread.

For example, does everyone realize that "nocturia" will probably overtake "snoring" as the most meaningful marker of SDB and that once the nocturia connection [commercial link URL removed per Apnea Board rules] is appreciated by primary care doctors, the diagnosis rate of SDB will shoot through the penthouse.

6. Data Monitoring. Again, I should spell out that you must be very careful of the data you get from these machines; it's much more qualitative than quantitative, in my opinion. The best test is being with a sleep tech that knows how to use a pressure transducer system and knows that it is possible to achieve a rounded or elliptical airflow curve in most people.

7. Ignore the Snore. The real value in snoring is that during the titration, it would usually mean that the inspiratory flow curve is not rounded, so keep increasing pressure to see if it will round. There are exceptions in that there really are cases of primary snoring, but in my opinion they are much less frequent than commonly advertised.

Good night and sleep right!

Barry Krakow, MD
Blogging at [commercial link URL removed per Apnea Board rules]
Books at [commercial link URL removed per Apnea Board rules]
Center at [commercial link URL removed per Apnea Board rules]

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[Apnea 1]

What settings should I consider (max IPAP, min EPAP, max PS)? What flex settings should I consider?

If you go the auto-BiPAP route, go with what settings the sleep lab suggests - at least at first.

I believe the sleep lab's recommended settings 18/12 were for a non-auto (standard) BiPAP. Are you suggesting that, on an auto-BiPAP, I use 18 max for inhale and 12 min for exhale?

[Apnea 1]

I will probably get the auto BiPAP. Pay for it myself. What settings should I consider (max IPAP, min EPAP, max PS)? What flex settings should I consider?

If Auto bi-level machine with EPAP adjusted for a range:
Min EPAP: 12 or lower (i.e., 10)
Max EPAP: 12 or higher (i.e., 14)
Pressure Support: 6
Max IPAP: Max EPAP plus Pressure Support (i.e., 14 + 6 = 20)
Bi-Flex: 0 or 1 or 2 or 3

The PRS1 BiPAP Auto and ResMed S9 VPAP Auto are both optimal machines for treating obstructive sleep apnea.

I know how long it must have taken you to write your post and I thank you very much.

I have questions on the part excerpted above. I plan on getting the PRS1 BiPAP auto. The clinician's manual for this machine does not list both Min EPAP and Max EPAP settings. It lists only Min EPAP. Also, I don't understand what you meant by "EPAP adjusted for a range." I did not see anything in the manual about adjusting EPAP for a range.

[vsheline]

If you go the auto-BiPAP route, go with what settings the sleep lab suggests - at least at first.

I believe the sleep lab's recommended settings 18/12 were for a non-auto (standard) BiPAP. Are you suggesting that, on an auto-BiPAP, I use 18 max for inhale and 12 min for exhale?

Those settings are certainly worth consideration. They come well recommended, by your doctor and/or Sleep Lab. That's why I showed how a bi-level auto machine can be set to mimic a straight BiPAP, in case you decide to try that approach.

If Auto bi-level machine with EPAP adjusted for a range:
Min EPAP: 12 or lower (i.e., 10)
Max EPAP: 12 or higher (i.e., 14)
Pressure Support: 6
Max IPAP: Max EPAP plus Pressure Support (i.e., 14 + 6 = 20)
Bi-Flex: 0 or 1 or 2 or 3

The PRS1 BiPAP Auto and ResMed S9 VPAP Auto are both optimal machines for treating obstructive sleep apnea.

I have questions on the part excerpted above. I plan on getting the PRS1 BiPAP auto. The clinician's manual for this machine does not list both Min EPAP and Max EPAP settings. It lists only Min EPAP. Also, I don't understand what you meant by "EPAP adjusted for a range." I did not see anything in the manual about adjusting EPAP for a range.

Sorry, I was assuming the settings terminology for PRS1 would be similar to the S9 VPAP Auto, which I used in the past.

Conceptually, the EPAP and IPAP will always be 6 apart (PS apart) and in Auto mode the EPAP will start at Min EPAP and the EPAP will self-adjust as needed between Min EPAP and 6 less than (PS less than) the Max Pressure limit.

If the PRS1 has settings for Min EPAP, PS and Max IPAP (or Max Pressure limit), then the Min EPAP and PS would be same as above, and the Max Pressure limit or Max IPAP would be 6 higher (PS higher) than the highest EPAP you wanted to allow.

If Auto bi-level machine but adjusted to act like a straight bi-level:
Min EPAP: 12
Pressure Support: 6
Max IPAP (or Max Pressure): 18
Bi-Flex: 0 or 1 or 2 or 3

If Auto bi-level machine allowed to auto-adjust:
Min EPAP: 12 or lower (i.e., 10)
Pressure Support: 6
Max Pressure or Max IPAP: highest EPAP to be allowed, plus PS (i.e., 14 + 6 = 20, if you want the EPAP to be able to go as high as 14)
Bi-Flex: 0 or 1 or 2 or 3

Take care,
--- Vaughn

[SuperSleeper]

I believe the sleep lab's recommended settings 18/12 were for a non-auto (standard) BiPAP. Are you suggesting that, on an auto-BiPAP, I use 18 max for inhale and 12 min for exhale?

I meant if you're going to purchase an Auto-BiPAP, set it up the way the Vaughn described - using the settings the sleep lab gave you as a recommendation. If they intended you to go on non-Auto Bi-level, then set up the auto-BiPAP like a straight Bi-level (non-changing pressures of 18 IPAP and 12 EPAP).

You don't have to use the auto-function of the auto-BiPAP machine right away. I would just set it up as the lab prescribed and review the data after about 2 weeks. My guess is that after that two week period, your AHI might still not be optimal - and at that point you can start making small, incremental changes over time in adjustments of all the settings, including IPAP, EPAP, PS and turning on the auto mode if you think that might help (it probably will if you tweak things correctly). But if you decide to go the auto mode route, I would only slowly open up the upper and lower settings, instead of allowing the machine to operate in a wider range of pressures immediately. In other words, you probably should only change the pressures by about 1 cmH2O at a time, then give it time to work before you decide to make further changes.

Remember, you need to make any setting changes slowly over time and never make any large change all at once. You need to give your body time to react to the changes so that you'll be able to analyize the true effect of each small change. Also, don't change more than one variable at a time, because if you do, and your AHI changes, you'll have no clue which variable caused the AHI change.

Hope that made sense!

[Sleepster]

What would the auto CPAP do here? I had imagined that it would go down to whatever pressure it could go down to without producing an apnea. If it works this way, it would seem to be fine. But I really don't understand how the auto CPAP works.

The autoCPAP will not lower the pressure on each exhale like a BiPAP will. It's true that the autoCPAP will lower the pressure if you're not experiencing apneas, but this is a much slower process. You would have to take many many breaths over a period of several minutes before the autoCPAP would lower the pressure.

I've been thinking about the seemingly strange recommendations of either a BiPAP at 18/12 or a CPAP at 14. We tend to think of the lower EPAP pressure of 12 as having no effect on obstructive apneas, but this may not be the case. It may be that obstructions occur in the airway when we're exhaling and that results in apneas.

Since you have to pay for the machine out of pocket, and because the higher pressure of 18 may cause complications such as leaks, I would go for the autoCPAP at 14.

I have a BiPAP but I am slowly raising the EPAP pressure because doing so lowers my AHI. I'm now at 11/10 and will likely reach a CPAP pressure of 11 in the next few weeks or so. I will then experiment with higher CPAP pressures. My sleep study prescription was CPAP at 13 but due to complications my doctor had to make some changes.

[Apnea 1]

What would the auto CPAP do here? I had imagined that it would go down to whatever pressure it could go down to without producing an apnea. If it works this way, it would seem to be fine. But I really don't understand how the auto CPAP works.

The autoCPAP will not lower the pressure on each exhale like a BiPAP will. It's true that the autoCPAP will lower the pressure if you're not experiencing apneas, but this is a much slower process. You would have to take many many breaths over a period of several minutes before the autoCPAP would lower the pressure.

I've been thinking about the seemingly strange recommendations of either a BiPAP at 18/12 or a CPAP at 14. We tend to think of the lower EPAP pressure of 12 as having no effect on obstructive apneas, but this may not be the case. It may be that obstructions occur in the airway when we're exhaling and that results in apneas.

Since you have to pay for the machine out of pocket, and because the higher pressure of 18 may cause complications such as leaks, I would go for the autoCPAP at 14.

I have a BiPAP but I am slowly raising the EPAP pressure because doing so lowers my AHI. I'm now at 11/10 and will likely reach a CPAP pressure of 11 in the next few weeks or so. I will then experiment with higher CPAP pressures. My sleep study prescription was CPAP at 13 but due to complications my doctor had to make some changes.

Thanks, now I get it. It is mainly the speed of transitions of pressure that differentiates between auto cpap and auto bipap. Only the auto bipap changes pressure fast enough to provide distinctly different pressure between inhale and exhale.

Regarding my buying an auto cpap machine, many years ago I was given a (standard) cpap. I found it very uncomfortable. I really need a lower pressure for exhale to be comfortable. So I guess I will buy an auto bipap. Of the two major brands, ResMed and Respironics, I will buy Respironics. Other threads document funny exhale noises on S9 ResMed machines. Also, I tried a (standard) S9 bipap from ResMed. The exhale noise happened at the end of every exhale and it was irritating.

Thanks for your help.

[Sleepster]

Thanks, now I get it. It is mainly the speed of transitions of pressure that differentiates between auto cpap and auto bipap. Only the auto bipap changes pressure fast enough to provide distinctly different pressure between inhale and exhale.

Any BiPAP will change pressure as you exhale. The autoBiPAP will also make changes to the pressure as it detects apneas and other events.

I almost asked you if you had complained about exhaling against the CPAP pressure. The fact that you had that difficulty is likely why they offered the BiPAP alternative.

Note that you need a higher pressure when on BiPAP than when on CPAP. I'd heard of this before but this is the first time I've seen a confirmation of it. I think that the higher pressure is needed, like I said before, because the airway can also collapse on exhale. Everyone has a different airway anatomy.

[RonWessels]

Thanks, now I get it. It is mainly the speed of transitions of pressure that differentiates between auto cpap and auto bipap.

That may not be it, depending on what you meant by "auto CPAP". Both APAP and Auto BPAP will adjust the pressure dynamically but slowly to the minimum value that does not allow apneas. This is separate and distinct from the fast-acting pressure difference between inhale and exhale provided by a BPAP machine.

Modern CPAP machines have a feature to also reduce the pressure on exhale, making them almost identical to a BPAP machine. The difference is that BPAP machines can have the inhale and exhale pressures set to pretty much anything, whereas CPAP machines can only have an exhale pressure reduction of up to 3 cmH2O.

Respironics calls the feature CFlex (or AFlex for their APAP machine). ResMed calls the feature EPR. Respironics has also recently introduces CFlex+, which is CFlex with a smoother transition between the inhale and exhale pressures.