Quick - How low can you go on BiPAP exhalation pressure?

I was planning on picking up an old cheap BiPAP Auto M Series to 10am this morning, thinking that the exhalation pressure can be set to zero or near zero (as opposed to 4cm, which I can already get to with my current machine with an EPR of 3 and a inhalation pressure of 7). But the manual seems to be saying the minimum pressure setting is 4cm. Can a newer/different model go lower than that?

I want zero resistance to breathing out, so is there a BiPAP machine in existence that can set that low of an exhalation pressure? Or am I not clear on the limitations or purpose of BiPAP.

Wow. Even for a small, elderly woman, (like me) 4 cm is barely perceptible on exhale.

What's going on that you have such a problem with exhale?

phopap wrote:

I want zero resistance to breathing out, so is there a BiPAP machine in existence that can set that low of an exhalation pressure? Or am I not clear on the limitations or purpose of BiPAP.

Zero resistance = turn the machine off

4 cm is pretty much as low as any of the cpap/apap/bipap machines can go.
There is one machine that might do 3 cm but that's it and I forget which brand it is.

Pugsy wrote:4 cm is pretty much as low as any of the cpap/apap/bipap machines can go.
There is one machine that might do 3 cm but that's it and I forget which brand it is.

That's the DeVilbiss IntelliPAP AutoBiLevel.

To the OP: 3 or 4 cm is as low as an xPAP machine goes. That much positive air pressure is needed to ensure that the CO2 you exhale is properly vented.

It's the difference in IPAP and EPAP pressure that can make it easier to exhale with a bilevel. You may find using a PS = 4 or 4.5 cm (which can't be done on an APAP) is enough of a drop in pressure that exhaling is easier than with a Resmed APAP with EPR = 3.

Pugsy:

DeVilbiss Intellipap DV57 Auto Bi-level may be the one you remember.
Bilevel Pressure Range.......................................................................................................3-25 cmH2O
But even setting the min to 3 cm H2O might not feel all that different from 4 cm H2O.

Exhaling pressure of 5 cm H2O in a CPAP is similar to using a straw to blow bubbles in a glass with less than 2 inches of water in it.
Try it out.

avi123 wrote:Exhaling pressure of 5 cm H2O in a CPAP is similar to using a straw to blow bubbles in a glass with less than 2 inches of water in it.

Only if you put the farthermost end of the straw at the bottom of the glass.

ChicagoGranny wrote:Wow. Even for a small, elderly woman, (like me) 4 cm is barely perceptible on exhale.

What's going on that you have such a problem with exhale?

I wish I knew. Right now I wish I was a small, elderly woman At the end of my exhales I observe that I'm not finished breathing out and the pressure from the machine is preventing the completion of my exhalation, and my physical response is that I'm suffocating.

robysue wrote:

Pugsy wrote: To the OP: 3 or 4 cm is as low as an xPAP machine goes. That much positive air pressure is needed to ensure that the CO2 you exhale is properly vented.

It's the difference in IPAP and EPAP pressure that can make it easier to exhale with a bilevel. You may find using a PS = 4 or 4.5 cm (which can't be done on an APAP) is enough of a drop in pressure that exhaling is easier than with a Resmed APAP with EPR = 3.

Terms: Does "xPAP" mean "any of the various types of CPAP"? "PS" means what?

Is the machine reversing pressure from exhale to the higher inhale pressure, like it's not following your breathing?

klv329 wrote:Is the machine reversing pressure from exhale to the higher inhale pressure, like it's not following your breathing?

By "reversing", I guess you mean "switching" the pressure back to the higher inhale pressure. That's a good question - if, hypothetically, it's not following my breathing, how would I confirm that is occurring, and how would I fix the problem?

3cmh2o is the lowest i've seen on a bi-level machine. The Resmed AirCurve 10 vAUTO can be set that low.

Hypothetically, you would check it against a backup machine or two.

At this point it would be helpful if you could use the User Control Panel to fill in your equipment profile.
Some CPAP's are quicker to turn around from exhale to inhale than others and that may be what is happening to you.
Most users are not sensitive to this effect but, rarely, some are. Because of commentary on this forum concerning this issue, I chose a Respironics machine instead of a ResMed because I felt that it might be an issue for me.

PS generally refers to Pressure Support, or the difference between exhale pressure and inhale pressure. The exact definition depends on the manufacturer and on the exact model of machine. On my machine, it tells the firmware (software controlling the machine) what the minimum difference it must maintain between the two. The maximum difference is the pressure difference between minimum EPAP value and the maximum IPAP value (or maximum pressure whichever is lowest).

ResMed machines do it differently and also take into account a function called EPR. I'm not up to speed on the ins and outs of that line of machine.