With GERD, is BiPAP superior to APAP reducing aerophagia?

[elliejose]

It works for me. I had terrible aerophagia. Now I have a bipap auto and NO aerophagia. I know what works for one may not for another, but that is just my experience.

[-SWS]

If you are 9cm on cpap to clear apnea, you will need to be on 13/9 on Bipap

That Respironics algorithmic strategy of increasing EPAP for apneas is driven by an issue in physics addressing "timeliness of airway inflation". I believe you know this, Snoredog, but others don't. So I'll mention it here. The highly common need for EPAP pressures to be equivalent to CPAP pressures does not say that human physiology is incapable of generating apneas during inspiration. And that highly common pressure need (EPAP=CPAP) does not say that everyone's apneas occur at precisely the same relative moment in a respiratory cycle.

Apnea occurs during inhalation, hence the IPAP value would seem to be the most important for minimizing apnea. On exhale, physics would seem to dictate that a lower EPAP pressure would help clear any obstruction... we all know that individual physiology can mix things up quite a bit

I think that all depends on each person's time-domain based mechanics of airway closure, Bill. When EPAP pressure requirements approach CPAP pressure requirements for any one obstruction, any of these three scenarios in physics might force that higher EPAP pressure requirement: 1) the obstruction has started at some point during expiration (endpoint likely), 2) sudden obstructive onset occurs during that pause in between inspiration and expiration, or 3) sudden obstructive onset and peak-pressure-requirement both occur during inspiration (and before a lowered EPAP-to-IPAP pressure transition, also known as "rise time", has the chance in physics to properly inflate the airway).

But truth be told, physiology just isn't the same for everyone. It's not like everyone is having apneas from just the base of the tongue falling back into the pharynx, cookie-cutter style. Quite a few patients and doctors report being able to get away with EPAP pressure requirements being less than that of CPAP. You seem to be one of those, Bill.

[blarg]

If EPAP=CPAP, and IPAP is even greater, then there is no pressure relief.

I don't fully agree with either of you, but on a BiPAP it's the DIFFERENCE between the pressures provides the pressure relief, not an actual lower pressure.

Now, that doesn't say whether everyone needs EPAP at CPAP or not, and personally I don't think one answer works for everyone here, but the reason BiPAP is nice at higher pressures is for the difference in pressures, not actually lower pressures.

[Snoredog]

If you are 9cm on cpap to clear apnea, you will need to be on 13/9 on Bipap

That Respironics algorithmic strategy of increasing EPAP for apneas is driven by an issue in physics addressing "timeliness of airway inflation". I believe you know this, Snoredog, but others don't. So I'll mention it here. The highly common need for EPAP pressures to be equivalent to CPAP pressures does not say that human physiology is incapable of generating apneas during inspiration. And that highly common pressure need (EPAP=CPAP) does not say that everyone's apneas occur at precisely the same relative moment in a respiratory cycle.

Apnea occurs during inhalation, hence the IPAP value would seem to be the most important for minimizing apnea. On exhale, physics would seem to dictate that a lower EPAP pressure would help clear any obstruction... we all know that individual physiology can mix things up quite a bit

I think that all depends on each person's time-domain based mechanics of airway closure, Bill. When EPAP pressure requirements approach CPAP pressure requirements for any one obstruction, any of these three scenarios in physics might force that higher EPAP pressure requirement: 1) the obstruction has started at some point during expiration (endpoint likely), 2) sudden obstructive onset occurs during that pause in between inspiration and expiration, or 3) sudden obstructive onset and peak-pressure-requirement both occur during inspiration (and before a lowered EPAP-to-IPAP pressure transition, also known as "rise time", has the chance in physics to properly inflate the airway).

But truth be told, physiology just isn't the same for everyone. It's not like everyone is having apneas from just the base of the tongue falling back into the pharynx, cookie-cutter style. Quite a few patients and doctors report being able to get away with EPAP pressure requirements being less than that of CPAP. You seem to be one of those, Bill.

[-SWS]

If EPAP=CPAP, and IPAP is even greater, then there is no pressure relief.

I don't fully agree with either of you, but on a BiPAP it's the DIFFERENCE between the pressures provides the pressure relief, not an actual lower pressure.

Now, that doesn't say whether everyone needs EPAP at CPAP or not, and personally I don't think one answer works for everyone here, but the reason BiPAP is nice at higher pressures is for the difference in pressures, not actually lower pressures.

To Bill's comment in the nested quote above: There is no exhalation pressure relief in that EPAP=CPAP scenario above, but patients are very often stuck with EPAP=CPAP to achieve an adequately low AHI.

To Blarg's comment about the IPAP-to-EPAP pressure transition itself somehow yielding comfort over CPAP: Amazingly quite a few message board posters have reported just that. In physics, however, that particular anecdote seems completely counterintuitive.

Yet in biophysics, you at least have these two BiLevel-related possibilities that do not occur with static CPAP alone: 1) some degree of ventilatory assistance occurs (by virtue of those IPAP/EPAP pressure transitions), and 2) BiLevel pressure transitions may even stimulate the respiratory-related vagus nerve via rhythmic IPAP/EPAP stretch-receptor input.

That first possibility speaks of pressure transitions and airflow. That second possibility speaks of rhythmic pressure-based pulsations on stretch-receptor cells. Sleep science is relatively young and modern medicine is hammering away at the details as we speak.

[Snoredog]

If EPAP=CPAP, and IPAP is even greater, then there is no pressure relief.

I don't fully agree with either of you, but on a BiPAP it's the DIFFERENCE between the pressures provides the pressure relief, not an actual lower pressure.

Now, that doesn't say whether everyone needs EPAP at CPAP or not, and personally I don't think one answer works for everyone here, but the reason BiPAP is nice at higher pressures is for the difference in pressures, not actually lower pressures.

To Bill's comment in the nested quote above: There is no exhalation pressure relief in that EPAP=CPAP scenario above, but patients are very often stuck with EPAP=CPAP to achieve an adequately low AHI.

To Blarg's comment about the IPAP-to-EPAP pressure transition itself somehow yielding comfort over CPAP: Amazingly quite a few message board posters have reported just that. In physics, however, that particular anecdote seems completely counterintuitive.

Yet in biophysics, you at least have these two BiLevel-related possibilities that do not occur with static CPAP alone: 1) some degree of ventilatory assistance occurs (by virtue of those IPAP/EPAP pressure transitions), and 2) BiLevel pressure transitions may even stimulate the respiratory-related vagus nerve via rhythmic IPAP/EPAP stretch-receptor input.

That first possibility speaks of pressure transitions and airflow. That second possibility speaks of rhythmic pressure-based pulsations on stretch-receptor cells. Sleep science is relatively young and modern medicine is hammering away at the details as we speak.

[-SWS]

I'm going by what the manufacturer says happens

The manufacturer never stated that significant numbers of patients cannot get away with EPAP pressures being less than CPAP. Don't confuse a manufacturer's probability-based pressure strategy with any sort of universalism in physiology.

The probability-based strategy of Resmed's A10 algorithm, for instance, does not mean everyone's obstructive apneas can be addressed by 10 cm of pressure or less. Respironics strategically hikes EPAP in response to apneas based on strategy alone and not universalisms in physiology. And either manufacturer's algorithmic strategy alone is not sufficient observational basis for anyone to derive epidemiological breakdowns (let alone 100 percent probability deductions). Rather from a manufacturer's pressure strategy alone you can safely deduce: that particular pressure-response strategy serves some significant number of patients if not a majority. I'll go along with some unknown majority until I see hard numbers. That pressure response definitely does not make for epidemiological universalisms.

Speaking of hard numbers, if you somehow managed to get the manufacturer's own epidemiological findings (better yet add independently verified findings), then you'd be able to interpret a pressure-response strategy with more than a guess. Looking at that pressure response alone, and then deriving an epidemiological pressure-response probability of 100% is not at all sound extrapolation. It's like that issue where two choices do not necessarily entail a 50-50 chance. Here, one pressure-based strategy does not equal a 100% epidemiological breakdown. Numbers, algorithms, facts, extrapolations, and logical deductions all make for tricky bed fellows.

.

[CheezWiz]

Snoredoog,

Since you seem to have all the inside info on how the Respironics Autos work, can you explain to me the following event?

I woke to the machine pulsing me like a machine gun with very high pressure bursts. I have OSA and CSA so I am curious if the machine's algorithm was simply trying to clear an OSA event or detected an excessively bad CSA and was trying to wake me?

I have awoke to this several times in the year since I started on the machine.

[Snoredog]

[quote="CheezWiz"]Snoredoog,

Since you seem to have all the inside info on how the Respironics Autos work, can you explain to me the following event?

I woke to the machine pulsing me like a machine gun with very high pressure bursts. I have OSA and CSA so I am curious if the machine's algorithm was simply trying to clear an OSA event or detected an excessively bad CSA and was trying to wake me?

I have awoke to this several times in the year since I started on the machine.

[blarg]

To Blarg's comment about the IPAP-to-EPAP pressure transition itself somehow yielding comfort over CPAP: Amazingly quite a few message board posters have reported just that. In physics, however, that particular anecdote seems completely counterintuitive.

I'm no physics expert but it didn't seem counterintuitive to me. If you inflate a balloon at a higher pressure than surrounding atmosphere, and then open it, the pressure equalizes. Because of the actual change in pressures, the higher pressure is in effect inflating the lungs. When you start to breathe out, EPAP kicks in and the extra air rushes out. That would make the exhale seem easier, no?

What am I missing?

[-SWS]

To Blarg's comment about the IPAP-to-EPAP pressure transition itself somehow yielding comfort over CPAP: Amazingly quite a few message board posters have reported just that. In physics, however, that particular anecdote seems completely counterintuitive.

I'm no physics expert but it didn't seem counterintuitive to me. If you inflate a balloon at a higher pressure than surrounding atmosphere, and then open it, the pressure equalizes. Because of the actual change in pressures, the higher pressure is in effect inflating the lungs. When you start to breathe out, EPAP kicks in and the extra air rushes out. That would make the exhale seem easier, no?

What am I missing?

Try comparatively plugging any one or two pressure-specifics into one particular time-domain point, and you can get a much better feel for that counter-intuitiveness I referred to:

Perform two sets of muscular-effort comparisons with identical lung volumes (waiting to be expelled at the same point in time, at the beginning of expiration) : 1) lung volume X, just on the verge of being expelled against 14 cm of fixed CPAP, and 2) that same lung volume of X, waiting to be expelled at that same comparative point in time, against 14 cm of EPAP.

Same atmospheric pressure, same 14 cm of positive air pressure, same lung volume, same relative moment in the respiratory cycle. Yet at least some patients report feeling noticeably less expiratory effort at 17/14 cm BiLevel compared to 14 cm CPAP. In physics alone that's counterintuitive. But in biophysics (and perhaps even the psychology of perception)yet additional physiologic factors cloud the comfort equation.

[NightHawkeye]

While you guys are puzzling all this expiration pressure relief stuff, maybe someone would like to take a stab at explaining how/why ResMed's EPR works the way that it does.

According to the prevailing theories being espoused here, one's EPAP needs to be equal to CPAP, while IPAP must necessarily go higher. Yet, that is not at all how ResMed expects their machine to be set up. (Do they?) My understanding is that EPR simply reduces pressure on exhale while leaving the inhalation pressure or IPAP unchanged.

EPR is simply a BiPAP function, is it not? Should we tell everyone who uses EPR to raise their CPAP pressure to offset the EPR reduction, which can be as much as 3 cm?

Regards,
Bill

[blarg]

Same atmospheric pressure, same 14 cm of positive air pressure, same lung volume, same relative moment in the respiratory cycle. Yet at least some patients report feeling noticeably less expiratory effort at 17/14 cm BiLevel compared to 14 cm CPAP. In physics alone that's counterintuitive. But in biophysics (and perhaps even the psychology of perception)yet additional physiologic factors cloud the comfort equation.

Ok, so 14 is 14 is 14 is what you're saying. That's true, but I think there's a noticible ventilator effect on BiPAP. On the IPAP, the lungs inflate further with the higher pressure. On the EPAP they contract. The muscles can be much lazier if they want because they're largely just triggering the inhale and exhale, while the machine is doing the work of actually breathing.

Exagerated I know, but I would be surprised if one actually used the same amount of muscle effort to breathe on BiPAP as a whole when compared to CPAP as a whole. Sure, same pressures, but you're breathing differently. It's not happening in a vacuum if you'll pardon the pun.

[CheezWiz]

[quote]I'm no expert on Respironics machines, but that pulsing like a machine gun doesn't sound normal to me. If your machine is the Auto, I don't think it will flip IPAP with EPAP when it sees a central event like a ST machine would do.

The Auto Bipap would just log that Central as a NRAH event. If it was a ST it would try flipping IPAP with EPAP and if things went wrong I could see it could hang in that mode for a number of reasons or a firmware issue.

If it was me, I would note the firmware level and contact Respironics or your provider about it, it shouldn't be doing that.

There are certain rules that need to be adhered to when setting up that machine, if some combination got input incorrectly I could see where it wouldn't function properly, but the machine programming is supposed to prevent that. Those machines are usually pretty good at self diagnosing themselves, so I would think you should have gotten some kind of an error.

First thing I would do is go through programming and make sure everything was set correctly, if it was I would contact Respironics about it.

With CHF I would think they would have given you at least a ST machine since CSR and CHF are usually found together.

[blarg]

EPR is simply a BiPAP function, is it not? Should we tell everyone who uses EPR to raise their CPAP pressure to offset the EPR reduction, which can be as much as 3 cm?

EPR and C-Flex only lower the pressure at the beginning of the exhale, which is not a place we're generally concerned about apneas occuring. This is why it feels as though they "cut you off" before you're actually done exhaling, so that the end of the exhale can be treated by your CPAP pressure.

BiPAP pressure v time graph looks like a square wave.
C-Flex pressure v time graph looks like a line with dips in it.