ASV Leak Graphs-Impossible to be Horizontal?

I decided to make this subject into a separate Topic, because it is sort of lost when mixed in with leak discussions on straight CPAP and bi-Pap.

I am wondering whether my thinking on this subject is correct, or incorrect. I am on ASV. I recently posted a leak graph in another discussion (see below) showing that my leaks were consistently under the red ResScan line, thinking out loud that maybe this rules out leaks as being the cause of my dry mouth and that I should look elsewhere for the cause, wherein a discussion ensued about individual differences in what provides satisfaction, quality sleep and waking refreshed or not, etc.

One person on bi-pap posted a comment that, while my very jagged up-and-down line under the red line might have been fine for me, she would have been miserable with all those jumps up and down, even though all were under the red line.

This got me thinking - how is it even possible to have a straight horizontal Leak line on ASV (unless of course you have absolutely ZERO leaks which would admittedly produce a "flat" line)?

Except for ZERO, isn't a leak a fixed percentage of pressure, lost either because of a mask leak or mouth-breathing? Let's say that my leak is a constant 5% loss of pressure. (A purely arbitrary example with a number picked out of thin air.) Now, on ASV, my pressure is constantly jumping up and down, breath by breath. Therefore, since the Leak graph measures QUANTITY of Leak, not PERCENTAGE of Leak, wouldn't my leak line in my Leak graph ALSO have to be jagged? As the percentage of leak stayed constant, wouldn't the quantity of the leak have to vary with the changes in pressure?

Straight CPAP and bi-PAP users have horizontal lines in their Pressure graph because their pressure is constant (except for the difference in inhaling and exhaling for bi-PAP), so if their leak is a constant percentage, their Leak Graph would also be horizontal, not jagged. It would only be jagged if their percentage of leak was constantly changing.

But so long as an ASV machine is set to ASV, wouldn't a constant percentage of leak have to be displayed as a jagged line? How could it possibly be a horizontal line?

Or am I way off base here?

Regards, Nate

NateS wrote: But so long as an ASV machine is set to ASV, wouldn't a constant percentage of leak have to be displayed as a jagged line? How could it possibly be a horizontal line?

Your assumptions seem correct to me since your PS varies and tends to run high (at least much higher than mine) and thus the IPAP is constantly changing (jagged) which effects the leak line.

One thing to consider is that the PS pulses (at least on the PR machine I have) are very short so they perhaps don't skew the average IPAP as much as we think but they do skew the average IPAP and mask flow rate to some degree.

NateS wrote:... How is it even possible to have a straight horizontal Leak line on ASV (unless of course you have absolutely ZERO leaks which would admittedly produce a "flat" line)? ...

Nate, that's one reason I say it's impossible to have a leak free setup with ASV therapy. Instead you try to manage the sound and amount of leaks. All that pressure changing stiffens up the silicone mask cushion. It also tends to blow out the seal. A mask liner seems to help, but it mostly just deadens the sound rather than eliminate the leaks.

JohnBFisher wrote:

NateS wrote:... How is it even possible to have a straight horizontal Leak line on ASV (unless of course you have absolutely ZERO leaks which would admittedly produce a "flat" line)? ...

Nate, that's one reason I say it's impossible to have a leak free setup with ASV therapy. Instead you try to manage the sound and amount of leaks. All that pressure changing stiffens up the silicone mask cushion. It also tends to blow out the seal. A mask liner seems to help, but it mostly just deadens the sound rather than eliminate the leaks.

Thanks, John.

It's very reassuring to hear that from you, as I think you are the resident Dean of ASV therapy here!

Regards, Nate

However, just for the fun of it, the challenge is still open! Anyone having a horizontal line for their Leak graph (other than zero) on ASV therapy, please put up your Leak, Events, and Pressure Graph for all to admire!

In fact, even a flat Zero Leak line on ASV would be very interesting to see.

And tell us how you did it!

Nate, that's a very persuasive argument regarding leaks and pressure, but I'm not sure of the correlation in the example you posted. In fact, there seems to be areas where the opposite is occurring, i.e., lower pressures with higher leaks and vice versa. But I do agree that all things being equal, higher pressure should yield a greater leak and, therefore, one could expect some variation in the leak line corresponding to pressure changes.

A change of scale on the leak graph, like with 40 as a max, might be interesting.

Jay

Jay Aitchsee wrote:Nate, that's a very persuasive argument regarding leaks and pressure, but I'm not sure of the correlation in the example you posted. In fact, there seems to be areas where the opposite is occurring, i.e., lower pressures with higher leaks and vice versa. But I do agree that all things being equal, higher pressure should yield a greater leak and, therefore, one could expect some variation in the leak line corresponding to pressure changes.

A change of scale on the leak graph, like with 40 as a max, might be interesting.

Jay

Jay,

Yes, I agree that a fixed percentage of leak rate was presented as a hypothesis. A more precise hypothesis would require sufficient knowledge of the varying efficiency of the mask seal and mouth seal with which to construct an algorithm relating percentage of lost pressure to applied pressure. My hunch is that such an adjustment would still not produce a horizontal leak line, because the range of efficiency between highest and lowest pressures would be in a much narrower band than the range of pressures applied. And yes increased pressure could sometimes cause a drop in lost pressure, but in any such series of events IMHO you are not going to get a horizontal leak line while on ASV, except through a miracle of a most dramatic series of mathematical coincidences over a night's sleep.

As for changing the scale on the Leak graph, that's probably temporarily doable within ResScan, but I'm not sure that would change anything. I'll try it when I have time, and post the resulting graph.

Regards, Nate

Here is a look at my stats.

Excellent, letsride!

And also proof that you don't necessarily need a FFM with ASV in all cases.

Regards, Nate

I usually shoot for a median leak of 0 for the night, which tells me that there was enough 0 (a ResScan leak of 0 *smile*) leak for me. That's about as good as it gets for me, along with having as much under the red line as possible. I usually have two or three spikes above the red line any given night, but not too bad. ASV is a whole different world with the rapid pressure swings you guys get *smile*. I get pressure swings, but not nearly as rapid or as large in magnitude.

The only time I can see that you would be able to get a flat 0 leak (or just the normal mask vent flow rate for non-ResMed) is if you were a sleeper that didn't move much and where either on straight cpap or apap with a fairly narrow range. My main problem is that I'm an active side sleeper and move around a *lot* at night. I'm not kicking anyone, but I'm changing positions a lot more than most people (including my wife *smile*).

NateS wrote: And also proof that you don't necessarily need a FFM with ASV in all cases.

And also that letsride probably doesn't suffer mouth leaks