BILEVEL PAP Therapy Pearls: Clearing the First Hurdle

One of the most important myths to dispel about bilevel is that it is not a ventilator (unless specifically programmed to function in the Timed mode). In other words, bilevel relies on the individual to initiate each breathing aspect, whether breathing in or breathing out. If for example, you were to hold your breath while breathing out on bilevel, the device will simply continue to blow out the current EPAP setting until you start breathing again. If you were to suddenly hold your breath to terminate your inspiration, it would also switch to EPAP and stay there until you breathe again. THIS WAS PARA EDITED PER RESTED GAL'S CORRECTION ABOUT BREATH HOLDING REVERTING TO EPAP ONLY, NOT IPAP!

This last point is the key to understanding how the transition points, I to E or E to I, are critical to finding both comfortable and optimal settings for the device, because it is the transition where many people have difficulties adjusting to this two tiered system of higher IPAP and lower EPAP.

And, as I've indicated previously, all of these points are relevant in your perceptions of your waking breathing compared to your sleeping breathing simply because they will confuse you in trying to interpret what bilevel is doing.

In the recent post, the sleeper alleges a difference between waking and sleeping breathing. Everyone should realize that everyone breathes differently while awake than while asleep, because the respiratory system functions differently during these distinctly different states of consciousness. For example, everyone's oxygen baseline drops to some lower level during sleep; and, you will see this drop among normal sleepers as well.

Most people would show better breathing while awake than while asleep on a titration, but there are those who will struggle with PAP therapy in various ways while awake that will make the breathiing look more erratic. Once asleep, this awareness of the machine diminishes (but I don't think it disappears) and the pressurized airflow can, if properly titrated, normalize breathing. For those, however, who maintain some anxiety about pressurized airflow in their sleep, the titration goes much less smoothly.

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CPAPopedia Keywords Contained In This Post (Click For Definition): Titration

Thank your for the explanations, Dr. Krakow.

I agree that a regular bilevel ("regular" being not an S/T type of machine with a timed bpm rate set) relies on the person's own breathing (inhale/exhale) to signal when the machine will deliver IPAP or EPAP.

I'm a little confused though, about this statement:

BarryKrakowMD wrote:If for example, you were to hold your breath while on bilevel, the device will simply continue to blow out in whichever phase it's in, IPAP or EPAP, but it will not transition to the next phase because your change in breath did not occur.

I agree that if I hold my breath at any point during or after exhalation, the machine does continue blowing at the lower EPAP pressure. It does not transition to IPAP until I start to inhale. Exactly as would be expected with any "regular" (not set for a timed backup rate) bilevel.

However, I thought all bilevels (again, just a "regular" bilevel -- not an S/T with a backup rate turned on) delivered IPAP only while the person was actively inhaling.

I've not used a PB bilevel, so perhaps you've had a different experience with your personal machine. With the Respironics and resmed bilevel machines I've used, IPAP always switches to EPAP in any of these scenarios if I:

1. start to exhale.
2. inhale steadily for longer than about 4 seconds.
3. inhale unsteadily - as in experimentally interrupting my inhalation for even the briefest split second before continuing the inhalation.

Having read what you said about the machine continuing to blow out in whatever phase it's in, IPAP or EPAP if a person holds their breath, I added one more experiment...today...LOL:

4. If I suddenly hold my breath in the middle of an inhalation, the bilevel switches to EPAP. Not only can I feel that happen, I watched the pressure display on the LCD. The instant I hold my breath during an inhalation, the IPAP pressure drops immediately to EPAP.

Unless the PB machine behaves quite differently during inhalation, I don't quite understand how (or even why) a regular (non S/T) bilevel machine would continue blowing inhalation pressure (IPAP) if a person held his/her breath.

Holding the exhalation pressure (EPAP) indefinitely until an inhalation starts, yes.

Holding the inhalation pressure (IPAP) in place if a person holds their breath? None of mine do that. Mine switch to EPAP if inhalation is not actively occurring.

I'd be very interested to know if the Puritan Bennett bilevel behaves differently in that respect.

Mea culpa!

Rested gal, nice analysis, you are correct. It only reverts to EPAP, not IPAP pressure during breath holding. I edited that paragraph to correct the information.

Thanks much for your attention to detail.

Thanks to all who have demystified the various bilevel devices, but I think I'm missing a major point.

For me, clearing the first bilevel hurdle will involve convincing a doctor that I could benefit from this type of machine in the first place. From what I have learned so far, it seems like a better option than my straight CPAP, but how will it respond to my central apneas? (I suspect that my frequent awakenings are due to central apneas which were found to outnumber the obstructive apneas in my diagnostic sleep study.)

What I mean is, if the bilevel depends on user-initiated breathing events, how does it help when someone stops breathing? Does it mean that I am forever doomed to waking up every hour or so, even with a bilevel?

Not to worry.
S/T machines can be set to start the inhalation phase after a certain time if nothing happens, and then there are the SV machines, that treat complex SDB (the kind that has centrals appearing once the obstructives disappear) very well. You're no way near doomed.

You just have to convice the doc that the presesnt therapy isn't good enough.

O.

Central apneas are a very tricky issue, because it could be reasonably argued that few people actually suffer from true central sleep apnea.

Years ago, the thinking was that central apneas often had an obstructive component, which meant they might respond to CPAP. Some clearly did respond to conventional CPAP. Over time, bilevel therapy was employed more frequently for centrals even without using the Timed mode.

Now with the clarifying research on the "complex sleep apnea" diagnosis, which means the emergence of central apneas in the context of PAP therapy, it is indisputable that some central events are actually being triggered by pressurized airflow.

This point is crucial to my previous discussion on pressure intolerance, which shows up most apparently during end-expiration on the airflow curve. By using bilevel in this situation, the drop off in expiratory pressure (EPAP) frequently results in a decrease of central apneas.

Now, some people will benefit from the new ASV (adapto-servo-ventilation) devices, and those with the diagnosis of "complex sleep apnea" seem to be the most suited for this volume-sensitive device. However, we have seen first hand in our lab, numerous patients who showed signs of central apneas when exposed to CPAP, which then disappeared with the introduction of bilevel and lower EPAP pressures.

Last, and not least, if the patient shows a great deal of central apneas on their diagnostic study, then most "bets are off" because the patient likely does have some central component to their SDB. One caveat though are the so-called sleep onset centrals. This type is somewhat more benign, and again, we have seen these patients respond more to bilevel than to CPAP. Whereas, a patient with classic centrals during sleep may prove more receptive to the ASV devices.

Bilevel Pearls #2

One of the most pressing and practical questions about Bilevel is whether or not you could start on this system without undergoing a titration. The short answer is “no” in my opinion, because the titration is much more likely to provide definitive information or at least start you down the path in the right direction.

Nonetheless, for those who may have a difficult time accessing a sleep lab that will provide a Bilevel titration or for those who may have access to loaner Bilevel machines, there are two big points to keep in mind.

Auto-Bilevel. The easiest way to start Bilevel, when a titration is not available, would be to have your physician prescribe a trial of auto-bilevel. The device allegedly works through a range of pressures, and then through data downloads you can find the predominant IPAP and EPAP settings triggered by your particular SDB. This sounds like a reasonable option and certainly does work for some people.

Our clinical experience, however, with auto-bilevel by the Respironics device has been unsatisfactory. We have seen few patients who report a positive response to the device. To be fair though we only use the device with a patient who has already undergone 1 or more Bilevel titrations and failed to respond well at home. We then switch them to Bilevel, not to find new pressures, but rather to see whether an auto-bilevel device would provide them with a better clinical response. Less than one-third of these patients report dramatic improvement compared to fixed Bilevel pressures, so for these patients were delighted for their sake.

Could auto-bilevel be used more routinely for various patients to give them a short trial of Bilevel and attempt to find their definitive settings. I think the general answer to the question is “yes.” But, I doubt the technology is precise enough in its algorithms at this point to be effective consistently.

Estimating Bilevel Based on CPAP. This approach would seem to be the most obvious, given that everyone seems to think that a “successful” titration with CPAP would at minimum supply you with the correct EPAP pressure, and then you would simply experiment with the IPAP setting by raising or lowering it to give various gaps or boosts a trial (the difference between IPAP and EPAP) at home.

The above paradigm fits with the conventional wisdom about how titrations are completed with Bilevel, that is, titrate the lower setting (EPAP) to a level that eliminates apneas and gross hypopneas, then use IPAP to titrate the remaining flow limitations (upper airway resistance). In another post, I’ll explain why this approach is too coarse to produce a definitive titration, but the pearl at this point is that the real goal of a titration with Bilevel is to completely normalize the airflow signal on inspiration and on expiration with whatever turns out to be the best IPAP and EPAP respectively for the 2 phases of breathing.

Now, the take home message from the points above are that we do not find that the “estimate Bilevel from CPAP settings” to be very effective. In fact, the most remarkable thing you will find is that EPAP pressure often turns out to be dramatically lower or higher than what the CPAP setting had been. Rarely, the EPAP is equal to what the CPAP setting had been.

Thus, most commonly, if a person were to estimate Bilevel EPAP, depending upon what had transpired at the their CPAP titration, then we would predict that EPAP should be somewhat to markedly lower than CPAP. In a patient with a high degree of pressure intolerance on the CPAP titration, it is also not unusual to find out that a much higher EPAP setting than original CPAP can be initiated; and, it seems this finding may in part be related to the noticeably improved ease of inspiratory breathing with higher IPAP pressures. Thus, in our experience, you are very much out on a limb when trying to guess Bilevel settings based on CPAP pressure.

Bilevel Fine-Tuning for UARS. This is the final but key point of this pearl post. Whether you try an auto-bilevel or work from the basis of CPAP, the chances are very low that you can fine tune your settings to eliminate all or most UARS events to eventually normalize the airflow signal. The auto-bilevel algorithms as far as I know do not aggressively and effectively titrate out UARS (even if they allege that they do). And, trying to guess IPAP and EPAP levels based on current CPAP pressure is also not likely to resolve UARS.

The final caveat of course would be whether or not you could monitor certain symptoms to help you figure out the best settings. Does dry mouth dissipate? Do nocturia episodes decrease? Is daytime fatigue or sleepiness markedly decreased? In my personal and professional experience, these symptoms can be monitored most effectively by first having the full night Bilevel titration, and then at that point, if more tweaking is needed for IPAP or EPAP or both, you can usually work from a basis that is much closer to the final settings, which means trial and error from that point is much more feasible.

So, if a titration is not feasible, and you can figure out another way to get close to IPAP and EPAP with the assistance of sleep specialist, then you may be able to work with Bilevel in that manner. But, I still recommend a titration as the best first step.

Thanks for all the interesting information, Dr. Krakow. How many sleep doctors work with UARS? What does a person look for in finding a local sleep doctor who knows about this and understands about titrating it out, with a bipap if need be? I don't have a sleep doctor, but have been working with my GP. I've been thinking about getting a specialist, but would like one who does the kind of work that you describe. I live in Michigan.

(I had 20+ "spontaneous arousals" that were unresolved in my titration study, though I was (mis)titrated by a very poorly trained tech, and have sinced raised my pressure and lowered my AHI considerably).

The question on how many docs work with UARS is of course relevant and interesting, but sometimes what's even more important is whether an experienced sleep tech is working in the lab the night you undergo your titration. For a very long time, many sleep techs intuitively or pragmatically understood the need to try to normalize the airflow signal to eliminate UARS.

As the best example of the above, one clear distinction among techs were those who understood that a relatively normal looking airflow curve in the presence of snoring likely meant the airflow curve was not normal and more PAP was needed.

Another pearl for titrations is to find a tech who appreciates the potential to titrate IPAP and EPAP separately, seeking to normalize both the inspiratory and expiratory curves, as opposed to following some lockstep rule that says IPAP and EPAP must be changed in tandem.

Now, back to the sleep docs. Obviously, the sleep doc greatly influences what the sleep tech will do, and therefore, if the sleep doc is receptive to bilevel titrations and willing to give the sleep tech some additional slack on how to handle the reins, then you would likely be in very good hands. Which is not to say that sleep lab protocols designed by sleep docs are not useful. Many develop these protocols to guide the techs, but when experienced sleep techs are permitted to work slightly "out of the box," they often discover optimal settings on an individualized basis, which sometimes would never have been arrived at or even anticipated if only a strict protocol were followed.

Dr. Ron Chervin's group in Ann Arbor (I think, but in Michigan for sure) is a terrific sleep center. Dr. Chervin and I trained together for a short spell during my mini-fellowship with Dr. Guilleminault at Stanford. They know all about UARS.

Thank you so much, Dr. Krakow! I've located Dr. Chervin and plan to make an appointment to see him. I currently don't have a sleep doctor and was singularly unimpressed with the report from the one who oversaw my sleep and titration studies.

I also found an interesting article by him about childhood SBD and hyperactivity that I've posted separately.

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The more I read Dr. Krakow’s posts and “pearls,” the more under-served I feel about my own diagnosis and care. (Pardon me, doctor. This is not a complaint about you, but about the options available to me. My insurance limits my care to the doctors and facilities within my region.)

Although I do have insurance (which cost me nearly $20,000 last year) and I live in a state known for quality medical care (Massachusetts), I feel like I live in a third world country when it comes to sleep apnea diagnosis, treatment, and patient education.

For example, my first sleep study was conducted in a hospital sleep lab. The room was furnished with a hospital bed, a bedside table, and an aqua vinyl chair oozing its stuffing. The mattress was so worn out that it offered no back support. When I complained, the technician laughed and said, “At least you’re not heavy. These beds are a joke.” To make matters worse, I was allergic to the tape used to secure the snore mic to my neck. That irritation, together with the bed discomfort, made my diagnostic sleep study so torturous that I barely slept. The interpreting physician wrote that I spent 48% of the time in stage 1 sleep, had 46 awakenings, and “there was constant oscillation between the wake and stage 1 sleep, probably due to conditions in the sleep lab.” And for this my insurer was charged over $4,000. It was supposed to be a split-night study, but conditions did not allow me to sleep long enough to qualify.

When discussing a follow-up titration study with my doctor, I said that I needed a more comfortable bed. He called me unreasonable. Imagine what he would have said if I had demanded a qualified sleep tech, a bilevel titration, and a protocol that titrates for UARS events!

Thanks to this forum, I’m getting the patient education I need. But I’m also becoming aware that I lack access to effective treatment and the means to demand it.

The wide variation in standards at various sleep centers is very disturbing, and the American Academy of Sleep Medicine is pushing very hard to mandate higher quality benchmarks through the process known as accreditation.

Accreditation directly impacts not only logistics, environment and convenience issues for patients, but there is also an expectation that practitioners adhere to practice parameters established by the AASM.

For example, one practice parameter clearly mandates that Bilevel therapy should be considered in a patient who reports difficulty breathing out against pressurized airflow. So, what's ironic is that we're having this discussion about the value of bilevel, and most readers are reporting that they would anticipate difficulties in communicating about a bilevel trial with their sleep providers; and, yet, the AASM has already indicated a practice parameter supporting such a need for select patients.

Thus, we can see that the dissemination of very good information has not yet made it into many sleep facilities for whatever reasons, but I don't think this problem is going to last much longer for the following reason: There is a move afoot to push accreditation to the point that no sleep facility will receive insurance contracts without it. No accreditation, no reimbursement. Money issues move things very quickly, and within a few years, the issue of accreditation should lead to much greater standards at a much larger proportion of sleep centers.

Our facility was created to provide a "B & B" feel, although we've not quite figured out the breakfast angle. Most patients love the cozy layout with no TVs, no phones, no hospital look, and lots of artwork. We invest a lot in very comfortable beds, linens, comforters and bedside lamps and armoires. We even designed special "holding" areas for our insomnia patients who we sometimes insist on practicing good sleep hygiene by leaving the bedroom in the middle of the night to work on imagery techniques, reading, or other relaxation approaches before returning to sleep.

While these logistical elements are a real plus, the strength of our sleep medical center is our sleep techs as we invest an enormous amount of time and training in developing their skills to interact at an extremely high level with our patients. The vast majority of our sleep techs have either completed, entered, or plan to enroll in a graduate program in a health-related field, and all are highly motivated to learn key elements of our Sleep Dynamic Therapy model.

I think one of the most exciting developments in the field of sleep medicine is the recognition among nearly all my colleagues of how much more training and skills are going to be needed for sleep techs. I think as sleep tech advancement catches on, it's going to have the largest impact on patient satisfaction.

BarryKrakowMD wrote:Our clinical experience, however, with auto-bilevel by the Respironics device has been unsatisfactory.

What about the Respironics auto-bilevel machines do you not like, specifically? I had unsuccessful UPPP surgery and my pressure went from 12cm pre-surgery to 20cm post-surgery, so I am going to ask my neurologist to prescribe an auto-bilevel for me (I am currently using a Remstar Pro with C-Flex and it's just not enough exhalation relief). I have loved my Remstar and was looking at the Respironics auto-bilevel due to the BiFlex feature.

Which machine do you prefer for auto-bilevel? I have also looked at the Resmed VPAP Malibu, which looks like a good machine.

Thanks so much for all of your valuable input! You are such a wonderful resource to cpaptalk.com!

I'd be interested to know what pressure settings the clinic usually puts in when trying the BiPAP Auto on some patients? In particular, what the min EPAP is usually set for, and what the Max Press Sup is set at.

Perhaps Dr. Kracow could give a couple of "real patient" examples (without names, of course!)

With people who had failed regular bipap, what was the BiPAP Auto set for (IPAP/EPAP -- compared to their previous IPAP/EPAP settings) and what was the Max Press Sup set for when they were given a BiPAP Auto to try?

I"m not impressed with auto-bilevel, because I question the validity of the algorithm. I'm not suggesting it won't work for some people; I've seen it work very well for a small minority of patients (very complex patients), but if the algorithm were really well perfected, I would expect it to be more favorably received by more patients.

By way of analogy, when we used to switch more patients from CPAP to auto-CPAP, a greater majority stated that it was easier to use and they thought their response was better than with straight CPAP. At that time (3 years ago), we looked at PB 420E data and believed that the UARS scale was useful in indicating patient responsiveness. Since then, we switch patients to standard bilevel.

I would guess that the auto-bilevel algorithm to deal with flow limitation simply is not adequate, or perhaps that the patient adjustment to the auto device requires a longer period for some reason. I'm not sure; I just don't see consistently positive results, and I've not heard much different from other sleep docs.

I'm supposedly getting some training on the RESMED Malibu auto-bilevel soon, and I will look to pass along any guidelines that seem useful; and if I find a recent patient on the Respironics auto-bi, I'll look to see if I can describe the settings. May be awhile, though.

Let me close by saying that we are big fans in theory of auto-bilevel, and we have repeatedly discussed the concept with the leading industry groups about our desire to see it perfected. So, I have no inherent negativity towards it; I just don't see great results yet, based on my previous posts about "normalized" vs "optimized" responses.

On another bilevel note, the Journal of Clinical Sleep Medicine just published an interesting study about non-compliant CPAP users. In one phase of the study, they looked at a group of what presumably was an extremely difficult subset of non-compliers and randomly divided them into CPAP and bilevel groups. By a ratio of about 2 to 1, the bilevel group was clearly more likely to become compliant.