Identical Machines Show Vastly Different Numbers

[ranman]

I have two identical Tank Style Respironics REMstar Auto c/w C-flex blowers. Both machines are set in auto mode with pressure set at minimum 12cm maximum 16cm with a C-flex setting of 3. I use a Resmed Ultra Mirage Full Face mask and the stand alone F&P HC150 humidifier.

I have used the machines for the last four months. During this time I have alternated between each machine every 3 weeks. Here is what I have seen for numbers. Keep in mind that both machines are set up identical with the same mask and humidifier.

On machine "A" my stats have averaged as follows:
AHI 0.4
OHI/HI 0.2/0.2
Large Leak 0
Avg Leak 43.5
V Snore 18.5
Percentage of night at each pressure: 12cm/50.2% 13cm/15.9% 14cm/12.7% 15cm/7.4% 16cm/13.8% = 100%

On machine "B" my stats have averaged as follows:
AHI 0.3
OHI/HI 0.2/0.1
Large Leak 0
Avg Leak 46.55
V Snore 39.1
Percentage of night at each pressure: 12cm/5.03% 13cm/1.45% 14cm/6.55% 15cm/35.08% 16cm/51.8% = 100%


I realize that both machines show pretty good numbers overall. It bothers me though that on machine "B" I spend way more time at the higher pressures of 15cm & 16cm to achieve roughly the same numbers as machine "A" where I spend the majority of my time at the lower pressures of 12cm & 13cm.

Any ideas as to why there is such a large variance here?

ranman

[Pugsy]

Do your machines respond to snores like the newer models? Only thing I see different in the data is snores. Roughly twice as many snores with the B machine. Now why more snores? I have no idea. Newer APAPs will increase pressure in response to snores if the snores also have flow limitations with them or some other event precursor. I know my M Series APAP would.

[ranman]

I have not seen any events or flow limitations shown in the numbers. Machine "B" can jump the pressure up almost immediately when I start up. These machines will up the pressure based on the VS numbers just as the M-Series units do.

I was thinking that maybe the "B" machine is off on the pressure setting. Such that when set at a minimum of 12cm it is really not supplying that pressure but maybe something less. Because I think I need that starting pressure of 12cm it could be that the machine senses that it needs to increase pressure thus the increase chasing snores.

My overall numbers appear to be about the same with both machines. My question is "Is using machine "B" and spending the majority of my night at 15cm/16cm versus using machine "A" and spending the majority of my night at 12cm/13cm a bad thing?

ranman

[Pugsy]

My question is "Is using machine "B" and spending the majority of my night at 15cm/16cm versus using machine "A" and spending the majority of my night at 12cm/13cm a bad thing?

I wouldn't think it is a bad thing. I think people get hung up on a "number" sometimes.
We do tend to wonder "why" though. Perfectly understandable.

[Perrybucsdad]

Is the hose the same on both units? Slightly elevated avg leak, but not by much. Could this be causing the elevated pressure? It would be interesting to see what a pressure gauge shows at the mask end of the hose.

[ranman]

The setup for each machine is identical. When switching one machine is simply unplugged and the second unit plugged in. The location,height and hose is the same for both and nothing changes.

ranman

[guestagain]

Using a water gauge can you check that the pressure in each machine is correct ?

[ranman]

guestagain!! Thanks for the advice!

I was checking out a CPAP website that talked about "Building Your Own Water Manometer". This looks like a fairly easy thing to construct. I'm going to try to put one together and do some testing on all of my blowers and see what pressure it shows for them.

ranman

[davelikesbeer]

guestagain!! Thanks for the advice!

I was checking out a CPAP website that talked about "Building Your Own Water Manometer". This looks like a fairly easy thing to construct. I'm going to try to put one together and do some testing on all of my blowers and see what pressure it shows for them.

ranman

I just searched online for this and it looks dead simple. I will have to try this at home.

Although, the site I found showed them connecting the CPAP hose directly to the manometer, I think I'd like to rig it to a CPAP mask. The machine should be able to maintain pressure even though the mask is venting. That's kind of the point.

And what would really be cool is to be able to breath through it and watch what happens during each breath. I think this could be done by connecting the CPAP hose to a T connector, with one going to the mask, and the other to the manometer.

Dave.

[MidnightOwl]

It looks like one sensor may be slightly more sensitive than the other. All cpap numbers are just approximations of reality anyway. Do you feel equally well on both? If so, then I wouldn't worry. If there's a difference pick the machine that makes you feel better and stick with it.

Why are you rotating machines anyway?

[6PtStar]

Is the Firmware the same on both? On that machine it is the first number that flashes on the LCD screen after you plug it in, Only stays for a few seconds. Manufacturers often change/upgrade the program within the same machine which effects how it sees and collects the data. Upgrades are suposed to be to make things better but I am not sure this is the case always. I have a couple of machines that have the same firmware that still reports minor differences. The one with different firmware does report more of a difference than the ones with the same firmware. These differences are why some doctors say ther data is not reliable. Most will find that using the data to establish a base line and then looking for variations does as much as anything else.

Jerry