Leak rate differences FFM and Pillows

This is a question I've been meaning to ask for a while. I've attached two leak graphs with the first being when using P10 nasal pillows and the second being when using an F30 FFM. The only difference between the two (other than the mask itself) is I change the "mask type" to pillows or full-face respectively. My AHI is the same and pressure is consistent when switching between the two mask types.

I understand the P10 has a vent rate of 29 L/min at 8 cmH2O and the F30 is at 36 L/min at 8 cmH2O, so the 6-7 cmH2O difference is expected. However, I have a number of leak rate graphs that show a leak rate of 0.0 for the P10 and F30 at similar pressures.

My question is whether something changed in OSCAR with a recent release when displaying leak rates. I've dug through the OSCAR documentation and don't see a mention of it, but wanted to check if anyone is aware or has seen anything similar. I wanted to be sure before digging in deeper with the F30 FFM to try and figure out what is going on.

Jlfinkels wrote: ↑

Tue Nov 29, 2022 9:53 am

I understand the P10 has a vent rate of 29 L/min at 8 cmH2O and the F30 is at 36 L/min at 8 cmH2O, so the 6-7 cmH2O difference is expected. However, I have a number of leak rate graphs that show a leak rate of 0.0 for the P10 and F30 at similar pressures.

One of the things the "mask type setting" does is that it tells a Resmed machine's on-board software how much "leak" to subtract in order to calculate the excess leak rate, which is what is posted in the leak graph.

To make this clearer: If you are using the P10 and mask setting is set to Pillows AND your total leak rate is 32 L/min, the calculated excess leak is 32-29=3L/min, and that's what will be plotted on the Leak graph.

If you are using the F30 and mask setting is set to Full face AND your total leak rate is 39 L/min, the calculated excess leak is 39-32=3L/min, and that's what will be plotted on the Leak graph.

In other words, if the mask type is set correctly and your total leaks are at or below the expected total leak rate for the mask type, the leak graph in Oscar (and ResScan) is going to basically be a horizontal line at 0 L/min.

robysue1 wrote: ↑

Tue Nov 29, 2022 11:24 am

One of the things the "mask type setting" does is that it tells a Resmed machine's on-board software how much "leak" to subtract in order to calculate the excess leak rate, which is what is posted in the leak graph.

To make this clearer: If you are using the P10 and mask setting is set to Pillows AND your total leak rate is 32 L/min, the calculated excess leak is 32-29=3L/min, and that's what will be plotted on the Leak graph.

If you are using the F30 and mask setting is set to Full face AND your total leak rate is 39 L/min, the calculated excess leak is 39-32=3L/min, and that's what will be plotted on the Leak graph.

In other words, if the mask type is set correctly and your total leaks are at or below the expected total leak rate for the mask type, the leak graph in Oscar (and ResScan) is going to basically be a horizontal line at 0 L/min.

Thanks. Mask type is set correctly and I understand how leaks are calculated. The question is what changed in OSCAR or in the setup that caused the graph to change. For example, below is the leak rate graph from the same F30 mask, same machine, same hose, same settings, from about 6 months ago before upgrading OSCAR and note the consistent leak rate of 0.0.

It is consistent, so the leak graph is either a leak has occurred with my FFM/hose or something changed in how it is calculated in OSCAR (or possibly the CPAP). Given that the P10 leak graphs are still showing 0.0 as the baseline and F30 is showing 6ish, I am assuming the machine and hose are fine. Just trying to understand what else has changed before I get too far down that rabbit hole.

Jlfinkels wrote: ↑

Tue Nov 29, 2022 11:43 am

The question is what changed in OSCAR or in the setup that caused the graph to change. For example, below is the leak rate graph from the same F30 mask, same machine, same hose, same settings, from about 6 months ago before upgrading OSCAR and note the consistent leak rate of 0.0.

Um.... your mask is 6 months older and it no longer seals properly?

ozij wrote: ↑

Tue Nov 29, 2022 11:48 am

Jlfinkels wrote: ↑

Tue Nov 29, 2022 11:43 am

The question is what changed in OSCAR or in the setup that caused the graph to change. For example, below is the leak rate graph from the same F30 mask, same machine, same hose, same settings, from about 6 months ago before upgrading OSCAR and note the consistent leak rate of 0.0.

Um.... your mask is 6 months older and it no longer seals properly?

Quite possibly, but it is only used maybe once or twice a month, so while possible it may not be probable. Also the leak is far too deterministic to be random, which leads me to wonder what else may have changed.

Jlfinkels wrote: ↑

Tue Nov 29, 2022 11:55 am

Quite possibly, but it is only used maybe once or twice a month, so while possible it may not be probable. Also the leak is far too deterministic to be random, which leads me to wonder what else may have changed.

I've been alternating an F30 with a P10 or a Bleep - installed OSCAR 1.4 about 6 months ago, and I have seen nothing like you have.

I did have a previous F30 in which part of the silicon worked itself out of the frame and gave me terrible leaks -- eventually they started waking me up and I finally realized it wasn't' the way the mask fit my face, it was the silicone coming out the plastic frame. A new mask solved the problem. Granted, I had been using the older mask almost nightly for a year - but I don't think it was normal wear and tear. I attributed it to pressure from a weighted duvet it must have slipped under one day when I got up.
Take a good look at the circumference where the silicone meets the road, sorry, the plastic....

This was all on older OSCAR versions, nothing changed when I installed 1.4

ozij wrote: ↑

Tue Nov 29, 2022 8:30 pm

I did have a previous F30 in which part of the silicon worked itself out of the frame and gave me terrible leaks -- eventually they started waking me up and I finally realized it wasn't' the way the mask fit my face, it was the silicone coming out the plastic frame. A new mask solved the problem. Granted, I had been using the older mask almost nightly for a year - but I don't think it was normal wear and tear. I attributed it to pressure from a weighted duvet it must have slipped under one day when I got up.
Take a good look at the circumference where the silicone meets the road, sorry, the plastic....

Thanks for the good advice. I’ve checked all the connection points but never thought of checking where the silicon met the mask. I’ll give it a good once over tonight. Tomorrow I plan on testing the hose as well just to be sure.

Jlfinkels wrote: ↑

Tue Nov 29, 2022 8:53 pm

I’ve checked all the connection points but never thought of checking where the silicon met the mask.

And while you're at it - connect and disconnect the elbow from the mask -- if you haven't considered that a "connection point" already.

robysue1 wrote: ↑

Tue Nov 29, 2022 11:24 am

One of the things the "mask type setting" does is that it tells a Resmed machine's on-board software how much "leak" to subtract in order to calculate the excess leak rate, which is what is posted in the leak graph.

All you have to do is look at the Resmed mask vent rate charts falsify that theory.

There's no correlation between the expected vent rates of pillows, nasal and full face masks, certainly nothing that would require a setting on the machine.

Just look at the wild variations in nasal masks, from 45 to 53lpm at 20cmh2o, There's an older page that has older masks out there (somewhere) that shows even more variation in the FFMs.

https://document.resmed.com/documents/p ... ow_eng.pdf

The mask selections are there for the differing *flow resistance* of the different types of mask, if you dig through a bunch of the manuals, you'll find the flow resistance numbers to be pretty similar between all the FFM masks (at least the ones I looked at), and then similar among the nasal masks, and then among the pillow masks, as you get smaller interfaces, there's more flow resistance, so the machine needs to up the pressure a little (not much, I've measured about 1cm pressure at the machine difference between the FFM setting and the pillow setting).

The machine calculates the baseline vent rate mathematically as you start breathing, you can *see* it doing it on the S9 VPAP Auto. I don't know if you can do that on the AC10 VAuto, I couldn't figure out how in the couple minutes I played with it just now, it's been dumbed down from the S9 display.

Here's a video of it doing it on the S9 VPAP Auto: https://www.youtube.com/watch?v=1eeDtO-k47c The first part of the video is just starting to breathe, then I introduced a leak, then stopped it, then took the mask off.

ozij wrote: ↑

Tue Nov 29, 2022 8:57 pm

Jlfinkels wrote: ↑

Tue Nov 29, 2022 8:53 pm

I’ve checked all the connection points but never thought of checking where the silicon met the mask.

And while you're at it - connect and disconnect the elbow from the mask -- if you haven't considered that a "connection point" already.

Well played mate for pointing me in the right direction. Turns out there was a leak in my heated hose where the mask bib connects into it. Apparently my habit of draping the mask over the end table side put enough stress on the hose connector such that over time it has widened the opening enough such that air escapes even when connected to the mask. Putting on a spare hose solved the problem.

Thanks again!