One More Time: Bi-level Pressure Support Question

I would have sworn I bookmarked or copied and pasted the information on just what Pressure Support does with a bi-level but .... my apologies.

Original IPAP 13 cms, EPAP 8 cms
With permission of sleep pulmo changed to IPAP 12 cms, EPAP 7 cms
Greatly reduced leaks and improved AHI somewhat.

At original settings of 13/8, pressure never went over 12 cms
At new settings of 12/7, pressure settings never go over 11 cms

Am considering changing settings to IPAP 13 cms again and leaving EPAP at 7 cms plus changing Pressure Support to 5 just to see what maximum pressure results are.

But I might not have Pressure Support reasoning straight in my head. (Save the wise arse comment's SnoreDog!! )

Don't know about in the ResMed machine you have, Slinky, but that setting is called "Max Press Sup" in the setup menu of the M series BiPAP Auto. It's called "PS" in the setup menu of the older non-M series BiPAP Auto.

My explanation, as I understand it, of the Pressure Support setting in the Respironics BiPAP Auto...like having two dogs yoked together on a leash:

viewtopic.php?t=15666
Dec 08, 2006 subject: Question for BiPap users - UPDATED 12/14/2006

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Jul 14, 2007 subject: What is 'Max Press Sup'

What has your AHI been running?

Does that machine give you individual AI and HI or just AI?

You have COPD, not sure but I think what you are asking is if you lower EPAP leaving IPAP where it is thereby increasing PS you increase tidal volume (as in alveolar hypoventilation, or if you had alveolar hypoventilation: you would want to lower EPAP to increase tidal volume.

They have a specific protocol for titrating with COPD, I was trying to find it, but no luck so far, will update if I find it.

Thanks, RestedGal, I knew I could count on you!

SnoreDog, you ole coot! I tried to yank your chain, sure you would come up w/a good smart arse remark to enjoy and instead you come up w/some helpful info! You never cease to surprise me!

I had no idea there might be a specific protocol for titrating for COPD available and sure would appreciate it if you can find it! I'm working blind and ignorant here.

I'm going to go finish reading the links RG has given me. Then do a download. But I'm thinking my timing is off and that a bit of an exacerbation of the COPD is starting up just to mess this current experiment up. I was a bit SOB yesterday morning when I got up and again this morning in addition to which this morning I'm bringing up some phlegm. *sigh* Dang, Murphy!!

By the way, RG. THAT is what I DID remember about the previous discussion: "like two dogs yoked together on a leash". I wonder why?? It was a great analogy for me given my "history".

The two dogs yoked on a leash were the reason I had thought of changing the Pressure Support to 5, but leaving the EPAP at 7. That would allow my IPAP to get back up to where it was running at my original settings if needed, but still allow for the EPAP relief that cuts down on my "lip flutters" as that lowering EPAP to 7 did reduce my Leak Rate and slightly improve my AHI for the past 2 weeks as compared to the previous 3 months at original settings.

One cautious step at a time. Patience is a virtue, patience is a virtue, patience is ..... I'm doing good so we are in the close ball park range and I could just leave things well enough alone now as the sleep lab's RPSGT suggested - but what else COULD he say, anyway? He's not the doctor. And there were other staff present.

Have GOT to get this S8 ResLink on my VPAP Auto today. I have the XPod oximeter and sensor for it now. The last couple days have been too hectic w/granddaughters here getting the horses and tack, etc. ready for competition this weekend and the gut acting up a bit.

Slinky, I will do what I can to expain it from my point of view. Hopefully that will give a starting point for the more experienced and technical-minded ones to work from. I have read and reread the manual until I have come to the following conclusions in layman's terms. . . .

On the VPAP Auto, you use the "Pressure Support" (PS) setting to set the difference between the inspiratory and expiratory pressures. Standard protocol for OSA patients would make that number at least a 4, but less than 10, but that is recently decided by the OSA gods, and so that fact is not reflected in the way the manual for the VPAP Auto was written.

You restrict the range of pressures in which the machine operates by using the "Min EPAP" and "Max IPAP" settings. Those aren't IPAP and EPAP settings, they are MAXIMUM IPAP and MINIMUM EPAP settings, the floor and ceiling numbers for the machine to bounce between.

The so-called "AutoSet pressure" is merely a fancy way of saying "the midpoint between the inspiratory pressure and the expiratory pressure." At least that's how I think of it. The problem is that it is the "AutoSet pressure" that is reported to you in data management and efficacy results as your "pressure" isn't a pressure you ever experience. VERY confusing. One way to think of it is that you are experiencing half your "pressure support" number above what the machine reports as your "pressure" and half your pressure support number below that. If the machine says your "pressure" was 14 for the night, it means your 95 centile maximum IPAP was half your pressure support number above that and your 95 centile maximum EPAP was half your pressure support number below that.

ResMed speaks of the "AutoSet pressure" only because "AutoSet" is ResMed's name for their algorithm, which was originally written for auto CPAPs, not auto bilevels. That is the crucial point, and therein lies the confusion everyone is experiencing as they read the manual, I believe.

When speaking in terms of a bilevel, the "AutoSet" pressure is an imaginary point (or, as the manual says, a "conceptual value") between the breathe-in pressure and the breathe-out pressure. The machine reports that pressure to you as if it were a real pressure, but it isn't. It would be a real pressure if it were running as an auto CPAP, but it isn't. In fact, ironically enough, the VPAP Auto CAN'T be run as an outo CPAP! But that's the algorithm inside it that it is using anyway. Thus the confusion people are experiencing on top of the other confusion.

But the important point in practice is that if your "Pressure Support" is set to 4 cm (minimum protocol for OSA), your experienced pressures will always be 4 cm apart, within the range of pressures set by Min EPAP and Max IPAP. That range is the floor and ceiling your experienced pressures are limited by, but your breathe-in pressure and breathe-out pressure will always remain 4 cm apart inside that range. If you know that, you're good, really.

The confusing thing about it, as far as reading your data, is that your reported "pressure," instead of being a number you experience, is the blasted imaginary (or as the manual says "conceptual") number that in practice will always be 2 less (if your PS is 4) than the 95 centile maximum inspiratory pressure you experienced. And, then, natuarally, that also means the "pressure" reported will always be 2 more than the maximum expiratory pressure you experienced.) That is very, very confusing to anybody but an engineer, I think, because you have to take the number the machine reports and then either add or subtract half of whatever your pressure support number is in order to extrapolate a useful number that represents reality.

What finally helped me to wrap my mind around it was when it clicked in my head that what ResMed did was to use the same algorithm of an auto CPAP in its auto bilevel. In an auto CPAP, all you do is give the machine a range to work in as it provides a single pressure. Right? Well, the added complication for an auto bilevel like the VPAP Auto is that it doesn't provide a single pressure but two alternating pressures. So intead of completely rewriting the algorithm, the engineers decided to take that simple algorithm of an auto CPAP and then add the dual-pressure part on top of it. So just think of the "AutoSet pressure" in the VPAP Auto as being what the auto CPAP pressure would be if the machine was providing one pressure as an auto CPAP. The way the machine is thinking is that the dual pressure part of what it does is merely a variation above and below what it would be doing as an auto CPAP. So the setting you use to get the machine to do its work as a bilevel, beyond what it would do as an Auto CPAP, is the "Pressure Support" setting. That is telling the machine how far above and below that midway pressure to alternate.

That is why if you have your Max IPAP at 13, your reported pressure will never go above 11 if your Pressure Support is set to 4--the machine has to have enough room to keep 4cm of pressure between your inspiratory pressure and your expiratory pressure, and the "pressure" being reported in the efficacy menu is the midway point between the 95th centile maximum pressures.

I hope I haven't made a total and complete mess of it all above. If I have, hopefully someone with a better and more educated brain than mine, and a better talent for explanation, can tackle your question. But I think that's the best I can do. Sorry. It is a confusing set of concepts, though, and it isn't your fault ResMed has the thing so darn counter-intuitive. So please keep asking your questions on it until it is crystal clear for you. I need you to understand all that stuff, though, so that I can begin asking you questions about what I should be doing in practice!

jnk

YOU can keep asking ME questions,jnk?? Pardon me whilst I choke on my laughter! That would be like the blind leading the near sighted!

Actually, I was able to follow your line of reasoning and explanation. Whether it would stick or not is the moot point, but, RestedGal got the point across quite clearly w/her analogy of two dogs yoked together on a leash since that was so easy for me to relate to. I raised and showed dogs for many years, as did RG. Once I could relate to that it became very clear!! And the concept is what I remembered even tho I forgot about the dogs, but I just wasn't sure. Now that the dogs have been mentioned again I know I did remember correctly. When in doubt, better safe than sorry, ask again.

One correction to what I said earlier (I reedited the document) about the OSA gods. Here is the protocal for difference beteen ipap and epap . . .

1: J Clin Sleep Med. 2008 Apr 15;4(2):157-71.Links
Clinical guidelines for the manual titration of positive airway pressure in patients with obstructive sleep apnea.
Kushida CA, Chediak A, Berry RB, Brown LK, Gozal D, Iber C, Parthasarathy S, Quan SF, Rowley JA; Positive Airway Pressure Titration Task Force; American Academy of Sleep Medicine.
Stanford University Center of Excellence for Sleep Disorders, 401 Quarry Road, Suite 3301, Stanford, CA 94305-5730, USA.
Positive airway pressure (PAP) devices are used to treat patients with sleep related breathing disorders (SRBDs), including obstructive sleep apnea (OSA). After a patient is diagnosed with OSA, the current standard of practice involves performing attended polysomnography (PSG), during which positive airway pressure is adjusted throughout the recording period to determine the optimal pressure for maintaining upper airway patency. Continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BPAP) represent the two forms of PAP that are manually titrated during PSG to determine the single fixed pressure of CPAP or the fixed inspiratory and expiratory positive airway pressures (IPAP and EPAP, respectively) of BPAP for subsequent nightly usage. A PAP Titration Task Force of the American Academy of Sleep Medicine reviewed the available literature. Based on this review, the Task Force developed these recommendations for conducting CPAP and BPAP titrations. Major recommendations are as follows: (1) All potential PAP titration candidates should receive adequate PAP education, hands-on demonstration, careful mask fitting, and acclimatization prior to titration. (2) CPAP (IPAP and/or EPAP for patients on BPAP) should be increased until the following obstructive respiratory events are eliminated (no specific order) or the recommended maximum CPAP (IPAP for patients on BPAP) is reached: apneas, hypopneas, respiratory effort-related arousals (RERAs), and snoring. (3) The recommended minimum starting CPAP should be 4 cm H2O for pediatric and adult patients, and the recommended minimum starting IPAP and EPAP should be 8 cm H2O and 4 cm H2O, respectively, for pediatric and adult patients on BPAP. (4) The recommended maximum CPAP should be 15 cm H2O (or recommended maximum IPAP of 20 cm H2O if on BPAP) for patients < 12 years, and 20 cm H2O (or recommended maximum IPAP of 30 cm H2O if on BPAP) for patients > or = 12 years. (5) The recommended minimum IPAP-EPAP differential is 4 cm H2O and the recommended maximum IPAP-EPAP differential is 10 cm H2O (6) CPAP (IPAP and/or EPAP for patients on BPAP depending on the type of event) should be increased by at least 1 cm H2O with an interval no shorter than 5 min, with the goal of eliminating obstructive respiratory events. (7) CPAP (IPAP and EPAP for patients on BPAP) should be increased from any CPAP (or IPAP) level if at least 1 obstructive apnea is observed for patients < 12 years, or if at least 2 obstructive apneas are observed for patients > or = 12 years. (8) CPAP (IPAP for patients on BPAP) should be increased from any CPAP (or IPAP) level if at least 1 hypopnea is observed for patients < 12 years, or if at least 3 hypopneas are observed for patients > or = 12 years. (9) CPAP (IPAP for patients on BPAP) should be increased from any CPAP (or IPAP) level if at least 3 RERAs are observed for patients < 12 years, or if at least 5 RERAs are observed for patients > or = 12 years. (10) CPAP (IPAP for patients on BPAP) may be increased from any CPAP (or IPAP) level if at least 1 min of loud or unambiguous snoring is observed for patients < 12 years, or if at least 3 min of loud or unambiguous snoring are observed for patients > or = 12 years. (11) The titration algorithm for split-night CPAP or BPAP titration studies should be identical to that of full-night CPAP or BPAP titration studies, respectively. (12) If the patient is uncomfortable or intolerant of high pressures on CPAP, the patient may be tried on BPAP. If there are continued obstructive respiratory events at 15 cm H2O of CPAP during the titration study, the patient may be switched to BPAP. (13) The pressure of CPAP or BPAP selected for patient use following the titration study should reflect control of the patient's obstructive respiration by a low (preferably < 5 per hour) respiratory disturbance index (RDI) at the selected pressure, a minimum sea level SpO2 above 90% at the pressure, and with a leak within acceptable parameters at the pressure.) (14) An optimal titration reduces RDI < 5 for at least a 15-min duration and should include supine REM sleep at the selected pressure that is not continually interrupted by spontaneous arousals or awakenings. (15) A good titration reduces RDI < or = 10 or by 50% if the baseline RDI < 15 and should include supine REM sleep that is not continually interrupted by spontaneous arousals or awakenings at the selected pressure. (16) An adequate titration does not reduce the RDI < or = 10 but reduces the RDI by 75% from baseline (especially in severe OSA patients), or one in which the titration grading criteria for optimal or good are met with the exception that supine REM sleep did not occur at the selected pressure. (17) An unacceptable titration is one that does not meet any one of the above grades. (18) A repeat PAP titration study should be considered if the initial titration does not achieve a grade of optimal or good and, if it is a split-night PSG study, it fails to meet AASM criteria (i.e., titration duration should be > 3 hr).
PMID: 18468315 [PubMed - in process]

Slinky,

My understanding is that the ResMed may be different from the Respironics in one important way. The Respironics may have soft leashes that allow the dogs to wander together and apart a variable distance throughout the night. (I think it has a max and min for pressure support.) But ResMeds use a stick to yoke the IPAP and EPAP together by their collar so that the pressure support "distance" doesn't vary. The dogs walk together inside the ResMed, but they can't get any closer or farther apart from each other as they march across the carpet.

jnk

Gotcha, jnk. The Respironics allow for a brace collar and the Resmeds allow for a yoke.

Ha, ha!! Reading that article you just posted (by the way, thanks for posting it):

1) All potential PAP titration candidates should receive adequate PAP education, hands-on demonstration, careful mask fitting, and acclimatization prior to titration.

What a joke!!!! Like is that EVER done? Adequate? Careful? Acclimatization? Prior? *snort*

MANY thanks for this article, jnk! Youse a peach.

Thanks, Slinky. Your help has changed my life, so I'm working hard to do what I can to help.

Snoredog may be thinking of something similar to slide 24 in the power-point presentation posted by the Oregon Clinic, as far as COPD protocol, although I think it represents only one doctor's opinion:

http://www.osrcnw.org/NIPPVOSRC-2008.ppt

Not that I understand it, but it says:

Management Strategies:

COPD

Main goal to decrease work of breathing (decreasing V/Q mismatch) and provide adequate ventilation

Relatively low EPAP: 5-8cm H20 (assuming no obesity or sleep disordered breathing)

Relatively moderate IPAP+EPAP: 10-14cm H20

Goal to have at least a 4cm H20 differential between EPAP and and IPAP+EPAP,; may need to go higher depending on ventilation requirements

--ie BiPAP 14/10 or 9/5