Exhale Pressures

Hi ya,

I had a conversation with my doctor yesterday and a question came up, which neither of us knew the answer for..

Anyone know what the actuall pressure applied to exhale with a respironics m series CPAP? Is it the total set pressure or is it the set pressure minus your natural exhale pressure?

i.e. if I exhale natually at 4cm, and the machine is set for 10cm, will the machine pressure reduce to 6cm for a total of 10cm? Or is the total exhale pressue 14cm?

Thanks in advance!

kest874 wrote:Hi ya,

I had a conversation with my doctor yesterday and a question came up, which neither of us knew the answer for..

Anyone know what the actuall pressure applied to exhale with a respironics m series CPAP? Is it the total set pressure or is it the set pressure minus your natural exhale pressure?

i.e. if I exhale natually at 4cm, and the machine is set for 10cm, will the machine pressure reduce to 6cm for a total of 10cm? Or is the total exhale pressue 14cm?

Thanks in advance!

Unless you have a BIPAP (which it doesn't appear you have), with a CPAP you have one straight pressure for both inhale and exhale *except* if you are using the C-Flex "comfort" feature. There used to be graphs on the Respironics web site showing how the different C-Flex settings lowered pressures but I kept getting bad link messages when I tried to find them. As I recall, a C-Flex setting of 3 provides the biggest change and 1 the least. If your machine is set for 10 cm, it will drop a little while exhaling with C-Flex.

APAP (Auto) machines work differently and BIPAP machines are set with both and inhale and exhale pressure.

Hope that helps.

Mindy

That's the concusion we came up with!

If your pressure is set at 10cmh2o and you are on CPAP, the machine will blow at 10cmh2o when you exhale. Ofcourse there is always the momentary drop in pressure at the beginning of exhalation if you have a machine with some type of exhalation relief, ie. CFLEX, EPR etc. Your intrathoracic pressures however may be higher due to anatomical abnormalities.

Fwiw - 0cm would be the atmospheric pressure you exhale against at your altitude. My doc didn't know that either. So it's all above atmosphere.

No wonder I could NOT exhale at 17cm and the expert doc I saw at that time told me to have the DME extend the ramp time - which I had already set to 45 min. The expert had no idea that 45 min was max. She said to make my straps tighter cuz I have Severe OSA. The leaks I had helped me breathe, lmao.

So if you can't exhale aqgainst 17cm and you wear the machine for 7hrs just how many apneas will YOU have? Yea, I had to fire her.

I have the resporonic with c-flex. I played with it till I got the right setting. Too much relief caused my airway to close up some. But the right pressure made it really nice. You have to try them all and find what is right for you. There can't be a formula. It is based on your personal anatomy and how much pressure relief you can tolerate before your airway starts to close.

So Gumby, I don't know anything about atmospheric pressures, etc, so what is the answer to your own question?? Would love to know what pressure settings and flex you arrived at after you fired the "expert".