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distance between IPAP and EPAP

PostPosted: Wed Oct 29, 2003 10:44 am
by sleepnerd
Hello everyone,

I would like some feedback re: the distance to keep IPAP and EPAP. Thinking it through, it makes sense to only increase EPAP to keep the airway open (for OA only) and to increase IPAP for everything else, such as OH and snoring. I have seen a text that recommends keeping them no more than 4 cm apart however (Principles of Polysomnography by Will Spriggs) and have been taught both ways. What do you think and please explain why? Is it true that some machines automatically increase EPAP when the difference is greater than 4 cm?

Thanks a bunch!

PostPosted: Wed Oct 29, 2003 4:34 pm
by SCNVsleep
I prefer to keep them no LESS than 4 cm apart and try not to go much more than 7 cm apart.

As far as machines go. I am only familiar with units that default to CPAP if you try to increase EPAP higher than IPAP. I am unaware of any that do not allow for more than 4 cm differential.

PostPosted: Thu Oct 30, 2003 2:35 am
by RayMeece
I hvae found that 3-4cm apart is most comfortable. I have gone as high as 7cm apart. But I do follow the protocol that if I see OSA, increase EPAP, for hypopneas, and desats, increase IPAP. This almost always gives a comfortable separation. And I don't know of any machine that requires a certain separation, just that EPAP can never be higher than IPAP.

PostPosted: Thu Oct 30, 2003 3:50 am
by stars
From RESMED manual /NPPV IN SLEEP LAB/ :shock:
Basic set up for titration patient with OSA,HYPERCAPNIA,OVERLAP Syndroim
IPAP -8 cm
EPAP 4 cm
set up Ipap max (60:rr:2)
Set up S/T mode
Set up RR 4-6 lower as patients spontaneous rate
Leave rise time at list 150ms.
Titration for patient with Neuromuscular,lung,Chest wall Disorder
Same,but if patient finds flow of air from machine uncomfortable
a/call to much pressure change rise time >150- but <400
b/patient breathing rapidly"air hungry/
rise time decrease to min as possible
Also for some of group of patient with SEVERE COPD and post poly patient level from IPAP to EPAP maybe more as 7-8 cm different.
NB To Raymeece You not return answer to my mail to you. :?: :?: :shock:

PostPosted: Wed Nov 05, 2003 7:23 pm
by sleep101
I think the "4 cmH2O" rule is mainly used in Respiratory. Some people think this is the rule for sleep, but really, whatever it takes to eliminate the problem is what should be used.

IPAP/EPAP relationship

PostPosted: Thu Nov 06, 2003 8:15 pm
by Ted the Sleep Guy
Keep in mind when you are using Bilevel pressures you are no longer simply stabilizing the airway. You are now actively enganged in ventilation. The difference between IPAP and EPAP represents the level of pressure support you are using for ventilation. In other words the difference in pressues is inversely proportional to the level of ventilation and the PaCO2. Therefore, if you are using more than 4 cm difference, the PaCO2 will fall. If you are beginning to see central events think about hyperventilation as a consequence of your IPAP-EPAP. A difference of 4 cm is not law. My opinion is that if you need more than a 6 cm differential, you should be monitoring end tidal CO2 as well. It is just safe practice.


PostPosted: Thu Nov 06, 2003 9:48 pm
by Ted the Sleep Guy
I would like to ammend my previous reply. Any bilevel use with a pressure differential greater than 3 cm should be accompanied by end tidal CO2 measurement. RCPs use bilevel ventilation in the ICUs and have the luxury of a variety of cardiopulmonary monitoring systems. This ranges from bedside ABGs to Swan Ganz measurements. To use the same bilevel modality, without at least some measurement of PACO2 is negligent. This modality should only be used by those thoroughly versed in the cardiopulmonary sciences.

Re: IPAP/EPAP relationship

PostPosted: Thu Nov 06, 2003 10:52 pm
by SCNVsleep
Ted the Sleep Guy wrote:Keep in mind when you are using Bilevel pressures you are no longer simply stabilizing the airway. You are now actively enganged in ventilation.

I disagree. Simple bilevel is not ventilation. When you add a back up rate, THEN you start getting in support ventilation.

Ventilation implies that at some point, the machine breathes for the patient, or spurs the take a breath. Simple bilevel is triggered by the patients own organic inspiration and expiration.

What stars referenced with NPPV is NOT bilevel. It is noninvasive pressure support ventilation and as such, should have measurement of CO2, and preferably be administered by an RT.

But it doesn't take an RT to titrate a patient on straight bilevel.

PostPosted: Fri Nov 07, 2003 12:03 am
by sleepadmin
I have long been frustrated when labs do things without a reason other than the sole purpose of following a policy. I'm curious why labs "dumbify" their titration protocol by requiring a flat 4 cm difference in pressures. This takes the "tech" out of sleep tech.

Sleepnerd... be carefull where you get your citations, that text is unedited and has been shown to have glaring mistakes. Peer reviewed publications are usually a bit nicer to use to justify your argument.

Also don't forget to check out this thread

thank you!

PostPosted: Fri Nov 07, 2003 8:34 am
by sleepnerd
Thank you for all of the excellent feedback! I appreciate it immensely!


Reply to SCVN

PostPosted: Fri Nov 07, 2003 1:09 pm
by Ted the Sleep Guy
You are mistaken my friend. Ventilation does not imply the pt initiates or does not initiate a breath. Ventilation implies that a volume of gas will be moved from point A to point B. Weather or not the pt initiates the breath is not the point. One assumes that pts in a sleep center are all breathing spontaneously!!!!! In terms of bilevel pressures and titrations, the greater the pressure differential the larger the volume of gas moved into and out of the lung. Therefore more CO2 will be removed. Capnography is to bilevel what Pulse Oxymetry is to CPAP. It is an important means of measuring the effect of what we are doing. Without it, we are shooting in the dark.

PostPosted: Fri Nov 07, 2003 1:56 pm
by stars
Ted you right and may be not same time .I have't time right now and need torun.May we can chat about this to night' stars

Reply to Stars

PostPosted: Fri Nov 07, 2003 7:48 pm
by Ted the Sleep Guy
Feel free to contact me. You can e-mail me anytime.

We're both right...and wrong...?

PostPosted: Sat Nov 08, 2003 1:10 am
by SCNVsleep
A laboratory study that compared a number of bilevel ventilators with a critical care ventilator found that triggering, cycling and leak compensatory mechanisms were superior in several of the bilevel ventilators (320). However, other laboratory studies have found that some bilevel ventilators have less inspiratory flow acceleration than do critical care ventilators, contributing to an increase in inspiratory work (321). Also, because they utilize a single tube for both inspiration and expiration, bilevel ventilators contribute to CO2 rebreathing unless used with a nonrebreathing expiratory valve that increases expiratory resistance and expiratory work of breathing (65, 322). Comparisons of bilevel and critical care ventilators in intubated patients have demonstrated that gas exchange is equivalent, but work of breathing is increased during bilevel ventilation if minimal expiratory pressure levels (2 to 3 cm H2O) are used (323). However, if expiratory pressures of 5 cm H2O are used, the two types of ventilators perform equally well in supporting gas exchange and reducing work of breathing (324), presumably because of counterbalancing of auto-PEEP. Credit: American Journal of Respiratory and Critical Care Medicine

So it would seem, that while I may not be 100% correct in my terminology, that if anyone is using less than 5 cm difference should be doing CO2 monitoring as there appears to be a decrease in gas exchange efficiency at lower pressure differentials.

Back to you SCVN

PostPosted: Sat Nov 08, 2003 5:01 am
by Ted the Sleep Guy
Aren't we saying the same thing? Or am I not understanding? First, most bilevel vents have lesser flow capabilities and allow for rebreathing of CO2. This imposes an increased work of breathing. Second, if the IPAP-EPAP differential is 2-3 cm, gas exchange is not enhanced. Third, use of pressure differentials greater than 5cm does enhance gas exchange. It seems to me all of the above SCREAMS-----MONITOR CO2!!!!!!!!