Change in flow rate - what's going on?

[Dormeo]

Cathyf, we can also always zoom in on the flow rate to look at the shapes for inspiration. It’s tedious, but it gives what is probably the clearest read on FLs.

[cathyf]

Cathyf, we can also always zoom in on the flow rate to look at the shapes for inspiration. It’s tedious, but it gives what is probably the clearest read on FLs.

right -- I'm talking about looking at the zoomed-in view -- being able to look at the OSCAR pressure graph and see that the machine took the pressure setting from 7.95 to 7.96 vs 7.95 to 7.94 tells you what the machine algorithm thinks is going on. If you have min=max=8 you are not going to see that.

[Geer1]

right -- I'm talking about looking at the zoomed-in view -- being able to look at the OSCAR pressure graph and see that the machine took the pressure setting from 7.95 to 7.96 vs 7.95 to 7.94 tells you what the machine algorithm thinks is going on. If you have min=max=8 you are not going to see that.

If zero flow limitations are present the machine won't increase pressure unless there is apnea, hypopnea or snore present.

[multicast]

If zero flow limitations are present the machine won't increase pressure unless there is apnea, hypopnea or snore present.

Definitely not.  Once an event happened and then reacting by an increase would be closing the stable door after the horse has bolted.

[Dormeo]

ResMed machines will increase pressure in response to the FLs their algorithms detect, though I don't know how quickly. Their algorithms don't detect all FLs, however, which is why looking at the inspiration traces in the flow rate is the best way to understand flow limitation.

[cathyf]

If zero flow limitations are present the machine won't increase pressure unless there is apnea, hypopnea or snore present.

Exactly -- if the flow limit curve shows zero but the pressure is not coming down, then that gives you the information that you need to go looking at other curves to see why the machine isn't lowering the pressure. Especially if it's raising the pressure.

But if you have min set equal to max (true constant pressure) then you won't have that additional piece of information.

My argument here is that if you want a "constant pressure" you should set your machine to a min and max slightly below and above that pressure. So if you want 10.1, set the machine to min=10, max=10.2.

1) the pressure arriving at your mask is not that exact, so 10/10.2 is constant pressure to the tolerances of your machine.

2) the way that the machine wants to change the pressure setting is valuable information, even if you don't allow it to change the setting. This information is in addition to all of the other information, which you still have.

[Geer1]

Or you could just look at event log, flow limitation graph and snore graph and know that if you are seeing events in any of these that pressure would be rising if you were in APAP mode.

Fixed pressure has advantages and one of the main ones is knowing if pressure makes a difference.

[Gideon]

The algorithms wait to lower pressure, I forgot how long but the wiki has examples of this. I may have included them in OSCAR - The Guide, most likely under the flow Limits or pressure discussion.