Experience with Adaptive Flow Hybrid

mecocosm · Post by **mecocosm** » Thu May 10, 2007 5:15 am

The exhaust leak rate of the Adaptive Flow Hybrid is around 33 liters/minute at 10 cm and 42 liters/minute at 15 cm

roster · Post by **roster** » Thu May 10, 2007 5:15 am

My mistake.

DreamStalker · Post by **DreamStalker** » Thu May 10, 2007 5:42 am

So the "Adaptive" in the new Adaptive Flow Rate technology is basically a "1/3 reduction" in the flow rate relative to the original flow rate?

The flow rate is plotted on a graph on the cover of the owners manual.

I'm just wondering if there is anything else to the "Adaptive" technology other than a reduction in flow. For example, are the exhuast ports different in shape in addition to being of smaller size?

What I mean is: are the ports cylindrical (same diameter on the inner surface of shell as diameter on outer surface of shell)? ... or is the diameter larger on inside than on outside?

roster · Post by **roster** » Thu May 10, 2007 6:48 am

DreamStalker wrote:So the "Adaptive" in the new Adaptive Flow Rate technology is basically a "1/3 reduction" in the flow rate relative to the original flow rate?

...........

Well my sleep-deprived brain is not working well this morning, but wouldn't a reduction in the exhaust vent area make it more difficult to exhale and also clear out co2 more slowly? Straighten me out please.

DreamStalker · Post by **DreamStalker** » Thu May 10, 2007 6:59 am

rooster wrote:
DreamStalker wrote:So the "Adaptive" in the new Adaptive Flow Rate technology is basically a "1/3 reduction" in the flow rate relative to the original flow rate?

...........
Well my sleep-deprived brain is not working well this morning, but wouldn't a reduction in the exhaust vent area make it more difficult to exhale and also clear out co2 more slowly? Straighten me out please.

Yes that would be my logical assessment too ... that is why I asked about the "shape" of the exhaust ports which may compensate for that somehow.

If someone with the revision C Hybrid manual could post the leak rate plot (graph), we could compare to the original from perspective of "what" exhaust flow rates to pressure differences there are rather than "how" they changed the shell to make those differences (although that is what I am more interested in).

WearyOne · Post by **WearyOne** » Thu May 10, 2007 7:30 am

I just wanted to post an interesting observation in my own treatment with the Hybrid.

I have the old style shell. Someone else posted that the adaptive flow has a vent rate of 33L/m for 10 CM. In comparison, the old style's rate for 10 cm is 48L/m.

For my pressure of 8.5, the vent rate on my old shell is 45.0L/m. My vent/leak number was running about 46 to 46.5 at one point. Then I cut the chin flap off. AFTER cutting the chin flap off (about three weeks ago, I think, maybe more), I have consistently run at 40.0 to 41.0 vent rate at 8.5 cm. Again, this is the old shell with the chip flap removed.

Anybody want to guess what's happening on this, what caused my rate to drop about 5L/m below the vent rate for the old shell after I cut the flap off?

Also, someone asked about buying just the shells. Not for the Hybrid, but I did see someone on eBay selling two shells only for another mask (don't remember which one), so that might be an option at some point.

I like the large venting on the old shell. Glad I have two old shells (after buying two whole sets).

Pam

oldgearhead · Post by **oldgearhead** » Thu May 10, 2007 8:25 am

The exhaust leak rate of the Adaptive Flow Hybrid is around 33 liters/minute at 10 cm and 42 liters/minute at 15 cm

Now we are getting somewhere. I guess I need two toothpicks.
I still think it was a runaway pressure problem with ResMed Autos..

Two toothpicks tonight. If I get a headache, I'll let you know..

DreamStalker · Post by **DreamStalker** » Thu May 10, 2007 8:56 am

oldgearhead wrote:
The exhaust leak rate of the Adaptive Flow Hybrid is around 33 liters/minute at 10 cm and 42 liters/minute at 15 cm
Now we are getting somewhere. I guess I need two toothpicks.
I still think it was a runaway pressure problem with ResMed Autos..

Two toothpicks tonight. If I get a headache, I'll let you know..

Again, if someone like mecocosm could post the plot from their manual, we can compare the curves. If the curves have the same shape and are simply shifted down relative to original ... then "Adaptive" means simple reduction of exhaust port cross-sectional area (ie. same as plugging up 1/3 of port holes). However, if the curves have different shapes or slopes, then there is something else going on with the new shell design.

BTW - I tried plugging up a couple of port holes way back when there was first talk of a revised shell in development ... I did get a headache.

WearyOne wrote:...
For my pressure of 8.5, the vent rate on my old shell is 45.0L/m. My vent/leak number was running about 46 to 46.5 at one point. Then I cut the chin flap off. AFTER cutting the chin flap off (about three weeks ago, I think, maybe more), I have consistently run at 40.0 to 41.0 vent rate at 8.5 cm. Again, this is the old shell with the chip flap removed.

Anybody want to guess what's happening on this, what caused my rate to drop about 5L/m below the vent rate for the old shell after I cut the flap off? ...

I have no explanation for that one

nate124 · Post by **nate124** » Thu May 10, 2007 12:54 pm

When I called their technical support, they said that the exhaust holes are now optimum for the dead space of the mask since the deadspace on the Hybrid is less than a standard Full Face mask and hence less CO2 build-up. Apparently the holes of the original Hybrid were designed assuming a higher deadspace.

That partially answers your question, Rooster. Since the dead space and CO2 build-up is less, I guess the vent flow rate can be lower?

- Nathan

roster · Post by **roster** » Thu May 10, 2007 2:14 pm

nate124 wrote:When I called their technical support, they said that the exhaust holes are now optimum for the dead space of the mask since the deadspace on the Hybrid is less than a standard Full Face mask and hence less CO2 build-up. Apparently the holes of the original Hybrid were designed assuming a higher deadspace.

That partially answers your question, Rooster. Since the dead space and CO2 build-up is less, I guess the vent flow rate can be lower?

- Nathan

Thanks Nate, I was thinking about calling them myself.

I am using straight cpap and am quite happy with the old Hybrid shell. In the near future I may have another sleep study and want to be titrated with the new shell.

My new shell should be here in a few days but I am afraid to use it for a whole night unless I get titrated with it. My concern is that the flow rate reduction will allow apneas that are not now happening with the old shell. Or the co2 will not be cleared out as well.

Last week my doc lowered my pressure to 8 from 10. This seems to be working well with the Hybrid. I occasionally use my F&P 432 for short naps and when I tried it with pressure 8, I had some bad apneas (My assumption, since I woke up with heart beating fast and feeling like crap).

I hope we hear back from OldGearHead after his latest toothpick adjustment.

rooster

cpapnewby · Post by **cpapnewby** » Thu May 10, 2007 3:50 pm

Rooster,

Are you saying that you are having apneas at 8 cm pressure using F&P HC432 but no apneas with the older version of Hybrid?

Then, it is either the higher vent flow rate of the old Hybrid or the less dead space (so, less resistance) of the Hybrid compared to a conventional FF mask like the F&P HC432. If it is the latter reason, you'll do fine even with the Adaptive Flow Hybrid because it has the same dead space as the older Hybrid version.

Jim