What does mask setting actually change (on resmed machines)

[Wonderbrah]

In my Airsense 10 settings page, it asks what type of mask you're using: pillows, nasal, full face mask. I'm wondering what if anything this setting changes. Is it just for data purposes so the type of mask is listed for clinician's awareness maybe, or does it actually change something related to pressure output?

[palerider]

In my Airsense 10 settings page, it asks what type of mask you're using: pillows, nasal, full face mask. I'm wondering what if anything this setting changes. Is it just for data purposes so the type of mask is listed for clinician's awareness maybe, or does it actually change something related to pressure output?

mask setting is not recorded in the data.

as to what it does, that depends on who you ask. the two main theories are
"it has something to do with leak calculations" (which to me, doesn't hold water, due to the variances of intentional leak among masks of the same type)
or,
it helps to compensate for differences in air flow resistance (which increases from ffm, to nasal to pillow masks) to allow the machine to more accurately deliver the intended pressure.

[Jay Aitchsee]

Here it comes. You knew it would
viewtopic.php?f=1&t=105637#p1000814

I've never seen that from resmed, (I'm sure there's a lot of stuff I haven't seen, I'd be interested in seeing any references.

Here's a couple:

DEFINITIONS
Leak: This refers to unintentional leak,
which is the leak value after deduction
of the intentional mask leak.emphasis added

ResMed devices calculate unintentional leak:
Unintentional leak = Total leak – Intentional leak from mask CO2 washout
You have to set the mask type. emphasis added

Interface selection
ResMed offers an exceptional selection of vented masks designed to ensure adequate washout of carbon dioxide while minimizing leak and maintaining patient comfort. All of these benefits are extremely important for patients utilizing NIV therapy.

Many ResMed devices offer an interface selection menu. Selecting the suitable interface enables the device to factor in the intentional leak emitting from the mask vent, which allows for more accurate unintentional leak reporting and alarm accuracy. emphasis added

Additionally, here's a paper you may find interesting:

http://scholar.google.com/scholar_url?u ... i=scholarr

Monitoring of Noninvasive Ventilation by
Built-in Software of Home Bilevel Ventilators
A Bench Study

In this study,we first realized that data provided by ventilator software were not measured in the same way in all devices; this is not always explicitly stated by the manufacturers. One device estimated leaks only under expiratory positive airway pressure (device E) (these results are thus misleading and cannot be compared with those of other devices); furthermore, some devices subtract from their estimation of leaks the intentional leaks expected for a given type of mask at a given pressure setting (devices F and G), while others report the sum of intentional and unintentional leaks. Once this was taken into account, the reliability of leak assessment was shown to be highly variable from one device to another. emphasis added

Devices F & G are ResMed which were found to be among the most accurate in leak reporting.

[Pugsy]

Here it comes. You knew it would

Glad you dug it up and saved me the time...and I knew you would. Thank you for saving me some work.

I think that a generic intentional value per each setting is used as a starting point at whatever pressure and excess leak is calculated from that starting point. It's going to be close but it's never going to be 100% accurate because of the small variations in vent rates among the masks in the same class.
It's going to be close enough though to get well within the ball park for determining if excess leak is bad enough to cause a problem.

[palerider]

Here it comes. You knew it would

well, actually no, I'd forgotten

thanks!

I admit that I still have problems with the concept, because of the published vent rates of the various masks, it just doesn't make any sense. :scratching head: add in the fact that the manuals all state "As a result of manufacturing variations, the vent flow rate may vary." which really makes it a "why bother" situation if it's just for making a good guess at excess leak rate.

I don't know, what I'd like to find is a patent that discusses it, something *technical*, not just an aside in a manual.

I note that the paper refers to the VPAP III ST and VPAP IV ST-A machines, which are both older tech, and, as a result, dumber tech. (earlier ASV machines had to have a sensing tube to measure mask pressure, because either the processor wasn't fast enough, or the software smart enough, to model the mask pressure out of the flow and pressure data in the unit itself... obviously this has been overcome with more advanced processing power in the S9 and later machines). I can see that with older, dumber machines, having to have these things set would make more sense in calculating leak, especially with fewer masks available, and probably different leak profiles among them.

I've seen two mask vent rate profile charts, from resmed, that were published at different times, and they show *different* leak amounts... implying that either one or both of the charts are wrong, or resmed has changed the mask vent rates..... well, of course I can't find one of them now, but I did find another one, and put them here..

some things of interest, looking at Resmed_pressure_vs_flow_rates.pdf, there's three different flow rates for nasal masks, and two for pillows. compared to 1016852_pressure-vs-flow_amer_eng.pdf however, the rates for the swift LT are different, but still nasal.

in mask-comp-list_amer_eng.pdf, it says that airfit N10 masks should use the pillow setting. interestingly enough, if you look at the *resistance* values in the manual, the n10 looks more like a pillow mask, than a nasal mask...
the following are some pillow masks (and the n10) the numbers are pressure drop at 50 and then 100lpm pressure

p10 .4 - 1.4
n10 .4 - 1.2
swiftfx .4 - 1.4

and some other nasal masks, pressure drop at 50 and 100lpm.
mirage activa .1 - .7
mirage fx : .2 - 1.0
mirage softgel .3 - .9

you see that generally, the pressure drop for a nasal mask (except the n10) is much less than the drop for a pillow mask.

anyway.. *shrug* I dunno.

[Jay Aitchsee]

I admit that I still have problems with the concept, because of the published vent rates of the various masks, it just doesn't make any sense. :scratching head: add in the fact that the manuals all state "As a result of manufacturing variations, the vent flow rate may vary." which really makes it a "why bother" situation if it's just for making a good guess at excess leak rate.

I'm not saying you're wrong. I've just posted the only things I have found published on it. I suppose it's possible the setting could do both, used for establishing unintentional leak and for setting resistance values. And the function could have changed over the years as more masks were developed. I'm pretty sure the settings definition themselves have changed. The patent relied on for the current machines probably goes back to the S6 or the S7, or maybe even earlier. Without trying to dig out the info, I think the last major change, was the with the S9 and the FOT used to detect CA, I know the S8 had an interface selection setting, which is the vintage of most of the quotes above re: unintentional leak, and I "think" the S7 did too, but I don't want to look it up tonight. There are probably some old threads about it from circa 2006- 2005 that should make some interesting reading - if there was nothing better to do - probably a link to some patent material, too.

I think the VPAP series references some "advanced leak detection" or something like that, again without looking it up, so maybe that series does use a little different methodology.

I think it reasonable to say something like, "The ResMed interface setting is used by the machine to compensate for the differences in flow resistance of the various masks and in the calculation of unintentional leak". Someone will find this quote with Google, repost it and it will become so. And then we can just use it to answer the next time the question comes up. Whaddya think?

[palerider]

I'm not saying you're wrong. I've just posted the only things I have found published on it. I suppose it's possible the setting could do both, used for establishing unintentional leak and for setting resistance values. And the function could have changed over the years as more masks were developed. I'm pretty sure the settings definition themselves have changed. The patent relied on for the current machines probably goes back to the S6 or the S7, or maybe even earlier. Without trying to dig out the info, I think the last major change, was the with the S9 and the FOT used to detect CA, I know the S8 had an interface selection setting, which is the vintage of most of the quotes above re: unintentional leak, and I "think" the S7 did too, but I don't want to look it up tonight. There are probably some old threads about it from circa 2006- 2005 that should make some interesting reading - if there was nothing better to do - probably a link to some patent material, too.

I think the VPAP series references some "advanced leak detection" or something like that, again without looking it up, so maybe that series does use a little different methodology.

I think it reasonable to say something like, "The ResMed interface setting is used by the machine to compensate for the differences in flow resistance of the various masks and in the calculation of unintentional leak". Someone will find this quote with Google, repost it and it will become so. And then we can just use it to answer the next time the question comes up. Whaddya think?

sounds like a plan.

also, note, I'm not saying that the 'used in leak calculations' is wrong, because I have no proof, but it doesn't make sense to me... at least, not with modern equipment, with older stuff, I could see it being needed for that.

speaking of the vpaps, on the treament screen, on the LCD, there's a 'leak' number... and you can see the leak amount, in real time. when you first start the machine, it registers each breath as a leak, until it calculates what the baseline should be, then it settles down to showing zero leak.
https://www.youtube.com/watch?v=1eeDtO-k47c
breathing, then after it settled down to zero, pulled one of the o2 port caps to create a leak... then plugged up up... back to zero leak, then removed the mask.

maybe the vpaps have to dynamically calculate baseline leak, because of the varying pressure?