cpap pressure less than setting

DreamStalker · Post by **DreamStalker** » Sun Sep 17, 2006 1:27 pm

As part of my attempt to establish a reference baseline for the Swift interface, I switched my APAP over to CPAP mode.

A brief background:
My original Rx was for 10 cm on CPAP. I used CPAP for about 3 weeks before I went to follow-up visit w/ sleep doc. Thanks to the great folks here, I was encouraged to ask my doc to convert me over to APAP ... which he did. At that point I began collecting data and have been doing so for about 6 weeks.

I was getting fairly good AHI results of less than 4 on APAP/Swift. Last week I decided to collect some data in CPAP/Swift mode and because my APAP numbers suggested that my median pressure was 10.6 cm ... that is the value I set the CPAP to.

My AHIs have jumped up to about 10 for the past 4 nights. However, what is even more unusual is that the 95% pressure value is only 9.6 w/ a maximum of 9.8 ... should both of these values not be constant at my setting of 10.6?

- roberto

DreamStalker · Post by **DreamStalker** » Sun Sep 17, 2006 8:06 pm

So uhhh ... anyone else had this happen or is my machine in need of a checkup?

- roberto

NightHawkeye · Post by **NightHawkeye** » Sun Sep 17, 2006 8:17 pm

I wouldn't worry too much about the change, Roberto. I ran a poll some months back and the vast majority of respondents indicated that their pressure had changed since being titrated.

My hypothesis (and I have nothing concrete to back it up) is that many of us compensate for apnea to some degree, such as never sleeping on our backs for example. At any rate, your titration would have been for one night, done before your body had recovered from any of the effects of apnea. It's not too unreasonable to think that your sleep patterns have changed as well if you are, in fact, sleeping better, more deeply and perhaps longer (or shorter) now, that your pressure needs have likely changed as well.

Just my $0.02.

Regards,
Bill

GoofyUT · Post by **GoofyUT** » Sun Sep 17, 2006 8:23 pm

Roberto-

I've heard of others who have experienced this with their S8 Vantages in CPAP mode. Though I believe that all machines have an acceptable tolerance of +/- 1 cm, its still a mystery to me why an S8 set to deliver 10.6 should be indicating 95% pressures of 9.6. Let us know if you figure this one out!

Good luck!!

Chuck

DreamStalker · Post by **DreamStalker** » Sun Sep 17, 2006 8:28 pm

Yes, I realize that my sleep study was not representative of my true sleep patterns or OSA characteristics and that my OSA characteristics are subject to change over time.

My concern is that I set the machine to 10.6 ... but my efficacy data shows 95% at 9.6 and a max of 9.8 ... which would explain my increased AHI numbers.

I thought if I used the machine in CPAP mode and set it to 10.6 then at the very least, my max should read 10.6 ... maybe I need to calibrate my machine to make certain it is pumping out dialed pressure?

Thanks for the reply though ... just wondering how common it is for machine to be off dialed setting.

- roberto

DreamStalker · Post by **DreamStalker** » Sun Sep 17, 2006 8:30 pm

GoofyUT wrote:Roberto-

I've heard of others who have experienced this with their S8 Vantages in CPAP mode. Though I believe that all machines have an acceptable tolerance of +/- 1 cm, its still a mystery to me why an S8 set to deliver 10.6 should be indicating 95% pressures of 9.6. Let us know if you figure this one out!

Good luck!!

Chuck

Fortunately, I also have a mamometer on back order along with my Breeze ... So maybe I can check the pressure out of the machine this week ... not that I will have an answer for why it reads less then what it is set for.

Thanks guys!

- roberto

DreamStalker · Post by **DreamStalker** » Mon Sep 18, 2006 10:27 pm

Well ... my cpap.com order finally came in today ... yipee!

First thing I did was to set up the mamometer to check my S8 Vantage in CPAP mode.

Pumps out the pressure within 0.2 cm ... I got the following results.

set to 10.0 cm got about 10.1 cm
set to 10.6 cm got about 10.8 cm
set to 11.0 cm got about 11.2 cm

So it must be that the Vantage is reading the pressure about 1 cm less than it is actually pumping it out at?

Time to start fiddling with the Breeze now ... see y'all later.

- roberto

DreamStalker · Post by **DreamStalker** » Wed Sep 20, 2006 10:21 am

** UPDATE **

Cindy (AKA - preemiern) had notified me that she had talked to the ResMed technical support people and that they told her that the calculated pressure values reported on the LED and data downloads is lower than the straight CPAP pressure setting if EPR is used (ie. it incorporates pressures for both inhalation and exhalation).

When I first noticed the discrepancy, I thought I had set EPR off but actually only fooled myself into thinking it was off. Last night I made certain that EPR was off and I did get a pressure reading for both max and 95% equal to the value I set for straight CPAP.

Mystery solved thanks to Cindy's inquiry to the ResMed tech support.

- roberto
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hrc54 · Post by **hrc54** » Wed Sep 20, 2006 10:27 am

Is this because the data & LED averages the pressure settings on the IPAP & EPAP with EPR?

Thanks-Bob

DreamStalker · Post by **DreamStalker** » Wed Sep 20, 2006 10:29 am

hrc54 wrote:Is this because the data & LED averages the pressure settings on the IPAP & EPAP with EPR?

Thanks-Bob

Yep ... that is correct. Well actually, there is only one setting when using in CPAP mode ... but yes it does average both the inhalation and exhalation perssures while EPR is on.

- roberto

Stryker5777 · Post by **Stryker5777** » Wed Sep 20, 2006 10:38 am

Just wondering if your nightly AHI went down, since you turned off your EPR?

I think I read you saying that at straight pressure your AHI was 10. You also didn't mention what the breakdown to hypoapneas and obstructive apneas are. I've had some problems using my c-flex on my machine and had to turn it off too.

Stryker5777

DreamStalker · Post by **DreamStalker** » Wed Sep 20, 2006 11:13 am

Stryker5777 wrote:Just wondering if your nightly AHI went down, since you turned off your EPR?

I think I read you saying that at straight pressure your AHI was 10. You also didn't mention what the breakdown to hypoapneas and obstructive apneas are. I've had some problems using my c-flex on my machine and had to turn it off too.

Stryker5777

I went on APAP a few weeks ago and began establising a reference baseline with a Swift interface. As the last part of this trial I switched back over to CPAP mode to collect some data and try to identify differences in APAP vs CPAP. That is when I discovered the discrepancy between the CPAP setting and LED/data report.

I had not thought of trying to determine the difference between EPR on and EPR off. That is a great suggestion and I will check into it ... thanks.

As for EPR itself .... when I switched over to APAP, as you may already know -- EPR is not available. I did not notice much difference having the EPR unavailable while in APAP mode .... perhaps due to minimum base pressure setting of 8 for APAP. In other words, while in CPAP w/EPR ... 10 - 3 = 7 and while I was in APAP w/ no EPR ... min = 8 and max = 13.

- roberto

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