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Sierra

Sierra
Joined Jul 2018
Bio

CPAP: AirSense 10 AutoSet

Set to CPAP Fixed Mode

Pressure 11 cm

Ramp: Auto

Ramp Start: 9 cm

EPR: 2, Full Time

Mask: ResMed AirFit P10 Nasal Pillow

Canada

Sierra
Joined Jul 2018
Bio

CPAP: AirSense 10 AutoSet

Set to CPAP Fixed Mode

Pressure 11 cm

Ramp: Auto

Ramp Start: 9 cm

EPR: 2, Full Time

Mask: ResMed AirFit P10 Nasal Pillow

Canada

EPR is a ResMed term for Expiratory Pressure Relief. It is simply a reduction in the mask pressure when you exhale compared to when you inhale. In theory the setting refers to the number of cm of water pressure difference. To the CPAP user it usually feels subjectively good. The higher pressure on inhalation helps you get air in, while the lower pressure on exhalation makes it easier to get air out. It sounds like a good thing, so why wouldn't you always use it? This is where it starts to get complicated, but my resolution of it is that for most, but potentially not all people, obstructive apnea occurs on the exhale side of the cycle, not the inhale. So, if you have your machine set at 12 cm for example, and the EPR at 3 cm, you are only getting 9 cm pressure on the exhale cycle and that is your effective treatment pressure preventing obstructive apnea on exhale. And, at the same time your mask has to seal against the 12 cm pressure. Now if your machine is in APAP or AutoSet mode it will increase pressure to compensate for the EPR providing your maximum is high enough. If it is not, then treatment is going to be limited, and your AHI is likely to go up.

I use the AirSense 10 Autoset machine, and this is how I use EPR. I have found that I can run about 1.5 cm lower pressure and get the same effectiveness with the EPR off compared to having EPR set at 3. But, I still use EPR set at 3 during the Ramp cycle of use. I find the EPR of 3 makes the CPAP more comfortable when I am awake and trying to go to sleep. I set the Ramp start pressure fairly high (8.4 cm currently for myself), so it cycles between 8.4 cm on inhale to 5.4 cm on exhale during the ramp period. I use the A10 Auto Ramp feature, which holds the pressure at that level until it senses you are asleep, instead of the gradual ramp up for a set period of time. And, there is a setting to make EPR effective on Ramp Only in the Clinical Menu.

This said, is turning EPR off effective for everyone? Well for my wife not so much. She seems to get less benefit than I do from turning it off. Must have something to do with when/how she gets apnea. She seems to gain less than 1 cm by turning it off.

What about A-FLEX or C-Flex used by Dreamstation. Well, it seems they don't really reduce the pressure on expiry although they use the same 1, 2, 3 setting scheme. They just shape the pressure response a bit on expiry, but the average pressure is not really reduced any significant amount. So, while I have not used those machines, I kind of think the setting may be a bit of a comfort perception thing. If you try it and like it, then use it. But, it probably does not change the treatment effectiveness like it does on the ResMed machines. Those are just my conclusions. Here is a link to an article on the differences between the machines in this feature.

Comparing expiratory relief in different CPAP machines