ASV as a Non-ASV device - an experiment

JDS74 · Post by **JDS74** » Sun Aug 10, 2014 2:29 pm

igdoc wrote:When breath holding (without physically obstructing the airway) which is by definition a central event, the machine will probably register an 'obstructive' apnea because there will be no flow change in response to the small 2cm H2O pressure pulses. In a way this is an example of a falsely classified event but can occur when awake and turning over in bed.

With regard to the different machine responses for the two different breath holds, my only thought is whether the first breath hold occurred soon after the machine had been activated and there will probably be a short lead in time of a minute or two before it starts responding. It might be worth repeating the experiment to see if this is the case. My guess is that both the different breath holds will register as 'obstructive'.
Ian

Ian:
Refer to the original post. The second definitely registered as a central. The first didn't register as anything.
I will repeat the experiment and allow for more time after starting up to see if that makes any difference. Perhaps two minutes may be enough time??? Perhaps repeating the obstructive breath hold three times follow by the central hold another three times.???
Interesting that BPM is disabled by PSMax=0. I missed that detail in the providers manual. Looks like I should read it again to see what else I might have missed.
James

palerider · Post by **palerider** » Sun Aug 10, 2014 4:07 pm

JDS74 wrote: If I were the firmware developer for this machine and I intended it to be usable as a CPAP, Auto BiPap, or an ASV machine, I would make those menu choices and not depend on mode selection by guessing from the other settings.

there's no mode setting on the 960?

I'd have thought there would be, since the 560 has a mode setting to pick from cpap and auto.

interesting.

buran · Post by **buran** » Sun Aug 10, 2014 6:46 pm

JDS74 wrote:Interesting that BPM is disabled by PSMax=0. I missed that detail in the providers manual.

I also did not find this in the manual. It only says that BPM is not displayed (in the setup screen) if PSmax=0. Logically if PSmax=0, than all what ASV can do is to create a “machine triggered breath” with pressure of zero amplitude, which is equivalent to BPM=”Off”. However, it is possible that the machine still flags the event, even though it cannot respond.

JDS74 · Post by **JDS74** » Sun Aug 10, 2014 7:41 pm

Just repeated the experiment. I'll post the details tomorrow when I download all the data.
Ran the machine for two minutes before starting.
But, it felt just the same - no reaction at all with simulated obstructives.
Pressure pulses with simulated centrals.

Since the pressure was 10 cm H2O and I am used to much higher, it was hard to be certain.
So I'll wait until morning when I have actual data.

Cheers

Corrected typo changed prior 20 to 10.

palerider · Post by **palerider** » Sun Aug 10, 2014 8:11 pm

JDS74 wrote:Just repeated the experiment. I'll post the details tomorrow when I download all the data.
Ran the machine for two minutes before starting.
But, it felt just the same - no reaction at all with simulated obstructives.
Pressure pulses with simulated centrals.

Since the pressure was 20 cm H2O and I am used to much higher, it was hard to be certain.
So I'll wait until morning when I have actual data.

Cheers

that doesn't make any sense, it wouldn't know the difference in an obstructive and a central without the pressure pulse.

can you rig up a makeshift manometer, maybe with some o2 tubing, and see if it bounces?

JDS74 · Post by **JDS74** » Sun Aug 10, 2014 9:04 pm

Go back to the OP.
It didn't notice the first simulated obstructive apnea even though the wave data shows no flow.
Its still very curious. I expect the new data to show the same thing.
We'll know in the morning when I process the data one way or the other.

JDS74 · Post by **JDS74** » Mon Aug 11, 2014 12:59 am

Well, now it seems that the ability to notice / report an event correctly is a function of how long into the session the event takes place. Waiting 2 minutes instead of about 15 seconds make all the difference.

On the fifth try, my simulation of a central event seemed to be detected as an obstructive event.
Compare with the much shorter experimental interval from the first experiment.

My suspicion is that this difference is related to the internal algorithm that computes breathing rate. It looks as if that computation takes the better part of one minute.
Notice the little black dots out at 3 1/2 minutes and 5 1/2 minutes. Those seem to indicate that the pressure is being slowly raised to fix the obstructive event problem. So Auto mode it is and not CPAP mode.

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