Dumb Question - APAP vs. BiPap

General Discussion on any topic relating to CPAP and/or Sleep Apnea.

Dumb Question - APAP vs. BiPap

Post by Spektor » Fri Sep 07, 2012 8:37 am

OK this is a dumb question, but I still can't figure out what is the big difference between BiPaps and APAPS with exhalation relief systems?

I know that BiPaps have MD-set pressures for inhalation and exhalation, but is it just that the difference is much bigger than what APAPs with exhalation relief offer or that the numbers are fixed by the physician? Do you feel the difference much more?

When would one use a bi-pap vs. a machine with exhalation relief?

And does a bi-pap sound wierd when its running? Does the motor go up and down up and down when its on or does it regulate pressure some other way?

User avatar
Posts: 43907
Joined: Thu May 14, 2009 9:31 am
Location: Missouri, USA

Re: Dumb Question - APAP vs. BiPap

Post by Pugsy » Fri Sep 07, 2012 9:38 am

Bipap is Respironics brand name for their bilevel pressure machines. Their exhale relief is called BiFlex.
VPAP is ResMed brand name for their bilevel pressure machines. They don't have a special exhale relief
unless using CPAP mode and then you get EPR.
So same animal called different names. BiPap has become sort of a generic name though.

Bilevel pressure machines offer 2 separate pressures. One for inhale and one for exhale. In straight bilevel mode these pressures are fixed. In Auto adjusting mode these pressures will auto adjust as needed.
Bilevel machines also offer straight CPAP mode.
There are bilevel machines that are strictly fixed pressures (so 2 machines in one straight cpap mode and fixed bilevel mode) and there are Bilevel Auto machines that offer auto adjusting pressures along with the other modes (so like 3 machines in one...cpap mode, fixed bilevel mode and auto adjusting mode)

APAP/CPAP machines offer a single pressure and the associated exhale relief with those machines.
Respironics calls their exhale relief "Flex"... it is a flow based relief and not a dramatic per cm drop in pressure. It doesn't feel the same as EPR in a ResMed machine. Hard to describe how it feels but for me it was more of a rhythm thing. A setting of 3 seemed "fast" to me...made me feel like it was trying to make me breathe too fast.
You can read about Flex here...http://aflex.respironics.com/ upper right lets you see each individual Flex explanation. To be honest, kinda hard to understand.

ResMed calls their exhale relief EPR... pretty simple relief, just a drop in pressure during exhale and a per cm drop for each setting with the setting of 3 being the greatest drop.
One can sort of get an idea what a Bilevel machine will feel like with EPR of 3. It isn't the same timing but it is a close feeling. I tested my ResMed VPAP in CPAP mode with EPR of 3...pressure 10...so 10 inhale and 7 exhale.
Pretty darn comfortable. I then tested it in straight bilevel mode with 10 IPAP (inhale) and 7 EPAP (exhale) so that gives a PS (pressure support..which is the difference between IPAP and EPAP) of 3 which is essentially what using cpap mode with 3 EPR is. For me it felt "close" but not quite the same...when using bilevel mode the machine actually waits longer if it needs to before changing from EPAP to IPAP. It will wait till I want to actually start the inhale before it increases to IPAP.
CPAP mode with EPR...the machine didn't wait. There is an option to change the response time for EPR if the timing is a problem. For me it wasn't a problem. I could tell the difference but it was every so slight of a difference and not a big deal. Just a minor "difference" in how something "feels" or is perceived by someone.
For this reason we sometimes refer to the use of ResMed with EPR of 3 a sort of "poor man's" bilevel. Technically it isn't but it is close in how it feels.

Now of course true bilevel machines offer more than 3 cm difference or what we call PS. It is this difference that actually offers the comfort. Believe it or not but using bilevel with PS of 4 is more comfortable than PS of 2.
I tried it by setting EPAP at 9 and IPAP at 11...so PS of 2 and EPAP at 9 and IPAP at 13 so PS of 4...and PS of 4 is much more comfortable than PS of 2 (for me).

Bilevel machines do produce a bit of a different sound because of the dramatic change in pressures so the motor or fan noise will change. How it is perceived is going to depend on the person's hearing and sensitivity to various tones and sounds. My husband says that maybe a teeny tiny bit of more "noise" with the bilevel machine when compared to my APAP PR S1 machine. He says he has to strain really hard to hear it and it is not a big deal. I can't hear any difference because I only "hear" the inhale and exhale. This has always been the way for me. It is more of a conducted hearing...if I plug up my ears with my fingers I still "hear" the inhale and exhale pretty much the same. It only takes me 2 or 3 minutes for my brain to tune it out and then I don't hear anything.

I happen to own both brands of bilevel machines...the S9 VPAP Auto and the Respironics PR S2 BiPap auto.
I have a thread where I discussed how I came to use the bilevel machine here. It may also answer some questions a person might have.
viewtopic/t71442/viewtopic.php?f=1&t=71 ... te#p656179

When to use Bilevel pressures...who might do better? Well, remember that there are "plain" bilevel machines that mainly do just the exhale relief thing and people who have aerophagia problems or simply problems exhaling against the pressures (could be high or low really) usually do well with those "plain" machines and there are bilevel machines that are used for people with a problem with centrals these are the ASV type of machines and there are many models in that line. My machines are what I call "plain" bilevel because I am comparing them to the high dollar ASV type of bilevel machines that are used for people with problems with centrals and such and that is a whole different discussion. Sometimes a plain bilevel machine is sufficient to keep centrals low enough to not be a problem...sometimes it isn't and someone has to move on to the high dollar ASV models.
I don't have a problem with centrals. When I used APAP machine I would see 18 cm at times during the night and I never had any more centrals than what would be considered normal and sometimes never had any centrals.
Higher pressures don't automatically create centrals. Some people will have centrals pop up at low pressures of 7 or 8...

Why do I sleep better and feel better using a bilevel machine over the APAP? Don't really know. I had no aerophagia issues to speak of and no problems exhaling against my APAP pressures. All I know is that I noticed a difference in how I felt and how long I slept and for me it works and that is all that I really care about.
I have recently began to wonder if maybe I had a UARS component to my OSA and wondered if maybe the higher IPAP has helped. There is no way to know for sure. Maybe my body and brain just like the "comfort".

Before anyone asks...which brand do I prefer? It really is a toss up but in my thread above I explain why I lean towards the VPAP. If I was prone to aerophagia issues I suspect I would like the roaming PS of the PR S1 BiPap over the fixed PS of the VPAP. The VPAP can also be set to mimic APAP..so not an official APAP mode IPAP and EPAP can be set the same and still allow auto adjusting. The BiPap won't let you set IPAP and EPAP the same...there is minimum default 2 cm PS...still very close to APAP if someone wanted to go that way.
Roaming PS and fixed PS is discussed in my thread above. I have no idea when or where one might be preferred over another based on medical needs. I have looked but never found the answer to that question.
I may have to RISE but I refuse to SHINE.

User avatar
Posts: 106
Joined: Thu Jun 07, 2012 10:08 pm

Re: Dumb Question - APAP vs. BiPap

Post by cherylgrrl » Fri Sep 07, 2012 5:06 pm

I've been on an auto VPAP for about 5 days now. I'm one of those people with too many centrals. My old APAP was completely silent, but I can hear a slight sound now with each breath cycle if I pay close attention. It's like a little "sigh". I love the machine, though, as it's gotten my AHI down to 0.

Mask: SleepWeaver Advance Nasal CPAP Mask with Improved Zzzephyr Seal
Humidifier: S9™ Series H5i™ Heated Humidifier with Climate Control
Additional Comments: Machine is S9 VPAP Adapt

User avatar
Posts: 17
Joined: Sun Jul 22, 2012 10:59 am
Location: Florida, USA

Re: Dumb Question - APAP vs. BiPap

Post by vze2363v » Sat Sep 08, 2012 5:15 am

I had a lot of centrals, but my local distributor for my HMO gave me the wrong machine so I have the BiFlex model. When I went in for compliance, the doctor's office looked over my reports and said they felt since I only had a couple of central events I no longer needed the $40 more per month ST model (which they said was like a ventilator). While the BiFlex was prescribed due to my centrals, my asthma made it really hard for me when they tried to use automatic settings. I had to have specific numbers to tolerate it at all.

I always thought my BiPAP was completely quiet until you said that. I have environmental noises and I usually have the weather channel on very low when I sleep. I turned everything off and put my ear next to the machine and realized it did actually make a noise on inhale. You learn something new every day.

Mask: ComfortGel Original Nasal CPAP Mask with Headgear
Humidifier: PR System One 50 Series Heated Humidifier
Additional Comments: It says EncoreAnywhere - Version on the report.

User avatar
Posts: 9286
Joined: Sun Mar 27, 2011 11:55 am

Re: Dumb Question - APAP vs. BiPap

Post by archangle » Sun Sep 09, 2012 2:06 pm

I THINK the technical/legal/insurance differences are:

Bilevel can give more than 3cm difference between inhale and exhale.
Bilevel can go over 20 cmH2O pressure.

Originally, bilevel was the only machine with difference between inhale and exhale. Manufacturers started adding this capability to CPAP/APAP, but made an artificial restriction of 3 cm in order to justify a higher price for bilevel.

More and more complicated features were added to both CPAP and bilevel machines, which blur the distinction of which is which. Fancy things like ASV and AVAPS were lumped into the "bilevel" category for classification and billing purposes.

The point is that the CPAP/bilevel distinction is somewhat arbitrary in terms of what they do. There are also vast differences in what one bilevel machine will do compared to another bilevel.

BiPAP and VPAP are trademarks for a particular manufacturer's bilevel machiens.

Machine: S9 AutoSet™ CPAP Machine
Mask: Swift™ FX Nasal Pillow CPAP Mask with Headgear
Humidifier: S9™ Series H5i™ Heated Humidifier with Climate Control
Additional Comments: Also SleepyHead, PRS1 Auto, Respironics Auto M series, Legacy Auto, and Legacy Plus
Please enter your equipment in your profile so we can help you.
Click here for information on the most common alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check for yourself.

Useful Links.