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Different pressure for breathing out

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ReliableCarmineQuetzal8749 +0 points · over 6 years ago Original Poster

I did this a couple years ago, so am a little fuzzy on the details. My CPAP was originally set at 15. I felt I was fighting the machine to breathe out. I found out how to go into the settings and lowered the pressure for the exhale by several pounds which solved the problem. I assume that the throat closure is an issue on inhaling but not on exhaling. Is that assumption correct and is there any downside to the adjustment I made and why are they not all set that way?

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wiredgeorge +0 points · over 6 years ago Sleep Enthusiast

Since you didn't bother let us know what machine you have, specifics are not possible. I am on a Bipap machine which has a set inhale pressure and set exhale pressure. The idea is to allow easier breathing and in my case this is because #1 my inhale pressure is 25 (exhale 21) and #2, the Bipap is the only machine capable of 25 pressure; Cpap machines are typically 20. I needed 25. In my case, do I need the lower exhale pressure which was set to allow more comfortable exhale? Not really, as I have played with the number to see what happened and have set the exhale to 25. I have a Resmed Aircurve 10 which has Bipap mode (and several others and is more expensive than their Airsense 10). I doubt there is any downside to decreasing the exhale to comfort level but your machine may or may not be able to do this function unless it has a Bipap mode. Unless your prescribed Cpap pressure is over 20, you may not have a Bipap capable machine. What machine do you have?

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sleeptech +1 point · about 6 years ago Sleep Enthusiast

I know this sounds counter-intuitive, but a lower pressure on exhalation DOES have an impact on your treatment. If your pressure on inhalation is 15 and exhalation is 13, you only get the effect of CPAP of 13. This is backed up by plenty of research and my years of experience in using CPAP and BiPAP. Exactly why this is the case is something that I'll let others try to explain, but there is no doubt if you have a higher pressure on inhalation an da lower pressure on exhalation (such as in BiPAP, C-Flex, EPR etc) it is the lower pressure that is your effective EPAP pressure.

This is one of the reasons why I don't like C-Flex, EPR and similar pressure relief features. Suppliers and retailers are told by the manufacturers that they can turn them on whenever they like without worrying about it, but I've seen them cause so many problems. Someone with a CPAP of 10 who has C-Flex on 3, is only actually getting a CPAP of something between 7 and 8 , and this will largely get ignored while the patient struggles with poor control of symptoms and high residual AHI that no one can explain. The other problem is that that small pressure change can be enough to hyperventilate someone and induce Cheyne-Stokes respiration. I have seen this happen with my own eyes.

In short, features like this can cause all sorts of problems unless they are used appropriately by a trained professional. They certainly can be used to good effect if used appropriately, but too often the appropriate amount of care an attention is not taken. It doesn't help that manufacturers never tell anyone about any of the problems that can result.

Sorry, that was a tangential rant.

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