Someone 'splain this........Lars4life - ok to read!

[Pugsy]

Here is the same report I posted above but I changed the leak reported to Total Leak. Notice it is pretty darn straight and it reports Average leak of 25.00. Vent rate is included in this. Only problem is the vent rate for my mask at my pressure is around 34 L/min. Obviously it can't be less so this means that the vent rate or base that the machine uses for calculation is not spot on. Nit picking? Yes, but it is what it is and we have to work with it.

So best we can do is get close and not let this drive us crazy trying to make everything match up. It won't. And this doesn't even have any larger leaks to mess with the average.

[Tip10]

Nope -- understood it perfectly. THANKS Pugsy!

Now, since I use a ResMed -- I'll go off and see if I can find out what fixed rate they apply to each of the 4 or 5 different mask types we have as choices for the machine -- in particular the difference between a NASAL ULTRA and a NASAL mask -- so that I can figure out which might be best suited for the actual published leak rates of whatever mask I might choose.

Does it really make a difference -- probably not -- but I AM an engineer by trade so I GOTS to do this -- its in my nature!

[Pugsy]

How does E.Pro "know" how much leak is intentional vs. unintentional? I

It doesn't. It gives a WAG or close approximation. See my last image of the same report I did earlier.

I haven't found a place to enter the mask's intentional vent rate. If he's not using a Respironics mask, is it just picking some default number?

There is no place to enter vent rate. Yes, Repironics is picking a default number of sorts but I played with it and found that even that number is not constant. Respironics math is notorious for sucking.

Do you think it would be better for Mac to set E. Pro to show total leak rate so he isn't counting on the software to make computations?

Not really needed. All it would show that might scare the heck out of him is that the leak line itself will be closer to the upper green line and the Large leak area. As long as he understands that the leak being reported is all real leak, that is all that is needed. No need to have to do the math and confuse things. The math won't work perfect anyway.
Main thing is the leak line needs to be straighter whether is is Total Leak or Excess Leak line. Averages are just too easily screwed with to be of any great importance.

In other words whatever the reporting figure (Total Leak or Unintentional Leak) starts out with during the night assuming no leaks at onset is a good base line to start with and hopefully not have huge bumps. The machine can compensate for a lot but we always should try to keep it generally within acceptable levels.

These numbers and graphs are useful for isolating problems. We can't expect to dissect every little number because of the infinite number of variables. It would drive us nuts. I used to try. I gave up because you know what? Whatever happened last night I can't do a thing about except maybe learn from it and try to do better.

[Drowsy Dancer]

Encore Pro offers 2 choices. Encore Viewer offers 1 choice.

Total leak which would include a "base" or vent rate and excess leak (Encore Pro choice and only choice for Encore Viewer)
or Unintentional leak which is all excess leak. (Encore Pro default setting which can be changed to Total leak)

Problem with Respironics machines is that it has no way of knowing exactly which mask type a person uses and with either way of reporting. Resmed machines at least get to get a closer estimate for Vent rate allowance (or base) before subtraction, by the mask selection feature.
So Mac's machine doesn't know what his base vent rate really is. It just takes a calculated number and that's what it uses. It is close but it is not spot on.

A while back I did a little experiment with the 2 reports. Unintentional and Total Leak. I toggled back and forth between the 2 and compared leak averages over the same 7 days. The "base" rate used by the machine varied between 28 L/min and 30 L/min. Okay that is wonderful but at my pressure my mask vent rate is 34 L/min... So obviously the number that is the machine calculated vent rate is not very close. I can't subtract 34 L/min vent rate from a Total Leak average of say 29 L/min (and I have seen it often and even 25 Total leak) and get a less than zero leak rate average.

In other words, the leak rate average shown is a close WAG. So I don't put a whole lot of stock in that average or even vent rate numbers for different masks. I just say look at the line itself. That is the starting point wherever it is and little bumps are okay but lots of big bumps not okay, doesn't matter what the overall average ends up being.

This is the part that makes me crazy. My Respironics machine would probably be horrified to know that I am using a Resmed-manufactured mask--sleeping with the enemy, as it were. For this reason I set my software to display "Total Leak" because how the heck can it know what is "unintentional"? I looked up the vent rate for my mask, but all I can really go by AFAICT is the shape of the line. It's like calculus all over again.

This part makes my head hurt. It seems so...so...imprecise.

In other words whatever the reporting figure (Total Leak or Unintentional Leak) starts out with during the night assuming no leaks at onset is a good base line to start with and hopefully not have huge bumps. The machine can compensate for a lot but we always should try to keep it generally within acceptable levels.

Yeah. But see comment above about head hurting.

DD

[Pugsy]

This is the part that makes me crazy. My Respironics machine would probably be horrified to know that I am using a Resmed-manufactured mask--sleeping with the enemy, as it were. For this reason I set my software to display "Total Leak" because how the heck can it know what is "unintentional"? I looked up the vent rate for my mask, but all I can really go by AFAICT is the shape of the line. It's like calculus all over again.

This part makes my head hurt. It seems so...so...imprecise.

Yeah, for those of us that like all this number stuff wrapped up in a neat little ball we do lose a few hairs over this.
When it really comes down to it though, 5 L/min variable in leak is really insignificant. The reports and software were never designed to be an exact reporting medium. Designed for trends and patterns to see what is going on in general. We are trying to fit a square peg in a round hole. Nit picking is time consuming, prone to give headaches and when all the nits are picked we still are left with imprecise numbers. They are close and really close enough to give the general idea as to what is going on and that is all it was really supposed to do.

We are the ones that want the software to be the holy grail and point out problems to the nth degree. When it comes to numbers.... well, they are just numbers. A scoring method that we use to validate our treatment. We need it like a diabetic needs their blood glucose numbers. It's just that our numbers aren't so accurate but they are close.

[mayondair]

This is the part that makes me crazy. My Respironics machine would probably be horrified to know that I am using a Resmed-manufactured mask--sleeping with the enemy, as it were. For this reason I set my software to display "Total Leak" because how the heck can it know what is "unintentional"? I looked up the vent rate for my mask, but all I can really go by AFAICT is the shape of the line. It's like calculus all over again.

This part makes my head hurt. It seems so...so...imprecise.

Yeah, for those of us that like all this number stuff wrapped up in a neat little ball we do lose a few hairs over this.
When it really comes down to it though, 5 L/min variable in leak is really insignificant. The reports and software were never designed to be an exact reporting medium. Designed for trends and patterns to see what is going on in general. We are trying to fit a square peg in a round hole. Nit picking is time consuming, prone to give headaches and when all the nits are picked we still are left with imprecise numbers. They are close and really close enough to give the general idea as to what is going on and that is all it was really supposed to do.
May have to keep Robysue away from all this fuzzy math and below zero leaks, gives me a headache, but might drive her to distraction. BTW where's McSnoresalot?
We are the ones that want the software to be the holy grail and point out problems to the nth degree. When it comes to numbers.... well, they are just numbers. A scoring method that we use to validate our treatment. We need it like a diabetic needs their blood glucose numbers. It's just that our numbers aren't so accurate but they are close.

[Pugsy]

May have to keep Robysue away from all this fuzzy math and below zero leaks, gives me a headache, but might drive her to distraction. BTW where's McSnoresalot?

Yeah Robysue and I have already talked about this fuzzy math back when I did the 7 day number test toggling back and forth with the leak average numbers and I found that the "base" varied. It does drive her nuts being math prof and all.

Where is Mac? I bet he is hiding and wishing he had never opened this can of worms. While not nearly as interesting and entertaining as his stories, sometimes we do have to get some work done around here.

[McSnoresalot]

"....it was my understanding that there would be NO math......"

I bailed on the calc series in college when they got to "imaginary numbers" - if "imaginary numbers" are cool, why didn't they accept my "imaginary answers". I'm not a volatile guy, but if someone asks me what is the square root of -1 ever again I think I'd go postal.

This is good info though - gonna start with trying to flatten the graph out - tighten up the head gear, make sure I'm not rockin the 2 day beard stubble.

gracias.


Mac.

[robysue]

May have to keep Robysue away from all this fuzzy math and below zero leaks, gives me a headache, but might drive her to distraction. BTW where's McSnoresalot?

Yeah Robysue and I have already talked about this fuzzy math back when I did the 7 day number test toggling back and forth with the leak average numbers and I found that the "base" varied. It does drive her nuts being math prof and all.

Yep. And on every night Encore Viewer reports my total leak (unintentional + intentional leak rates) as a number that's between 17 L/min and 20 L/min. And the intentional leak rate for my mask at my pressures ranges from 20 L/min (at 4cm, my min EPAP) to 30 L/min (at 8cm, my max IPAP). And my EPAP is at 4cm for only about 50% of the night these days. (Spring allergies, I hope since the tummy does NOT want to increase that max IPAP to let the EPAP go up higher than 6cm.) So I know all about those negative unintentional leak rates.

All this falls into the category of "let's hide what's really going on from the patients because they're too dumb to understand it." And I do resent it on multiple levels both as a patient and as a mathematician. PR's customers ought to have the same kind of clear definitions of "Large Leak" and "what gets subtracted off to compute unintentional leak" that Resmed's customers have. And don't even get me started on the lack of genuine, bona fide overnight data on the PR System One's pitiful LCD (and I'm one who has the backlit LCD).

[HoseCrusher]

Pugsy, I don't know if this every crossed your mind...

If your mask's leak rate is supposed to be 35 l/m and it is only venting at 25 l/m, obviously your mask is defective.

You can actually get a good approximation of your mask's leak rate by doing a test.

First you have to figure out a way to plug the main opening of the mask. This allows air to flow only through the vent.

Next you need to find a plastic bag with a known size. For example a 33 gallon trash bag holds about 125 liters (33 X 3.8 = 125.4).

Finally the test. Put your mask into the bag and seal it with your hand as well as you can around the hose. Turn the machine on, and at the same time note the time. If your mask vent is flowing 25 l/m it should take about 5 minutes to inflate the bag.

While not exact, it does give you an idea of where you are.

[Pugsy]

You can actually get a good approximation of your mask's leak rate by doing a test.

I am going to get right on that test.... just as soon as I get my stuff ready to go to tax lady before I have to file an extension because I have spent too much time here. Does mask failure mean I can't count that night I had AHI of 0.2?? Oh crap, that was the only thing keeping me going..

I am with Robysue and her frustrations with the reporting software, etc. Heck, I would be thrilled to actually see a number for the "Large Leak". All I know is I hit 80 L/min one night and it didn't flag as a Large Leak and that is pretty sad but maybe it is near 100... Intellipap says it can handle to 95 L/min. Just give me something I can sink my teeth in.

With the plus or minus variables listed in mask vent material and the plus or minus variables that are obvious in the machine reporting software, I am surprised we get as close as we get. Still it is better than being completely in the dark so I try to look at the pluses and not the negatives. Won't change anything but makes me feel a tad less frustrated.

[HoseCrusher]

Pugsy, let's see now...

It would probably not be appropriate to show up at the tax ladies place with a bag full of air... It would be funny though.

I forgot to mention that you can also check the maximum capacity of your machine the same way. Just take the mask off and shove the hose into the bag.

If you play with this a little, you can actually get an idea of how the machine is scoring leaks. In a "fuzzy" world, this can offer some surer footing.

[mayondair]

Plastic bags! the tax lady is sounding like more fun where's McSnoresalot? Think I'll join him, all this math , fuzzy and otherwise is giving me a headache McSnoresalot! come back we didn't mean it! No more math, just work on the leaks and we'll make the calculus go away!

[Janknitz]

Well, none of us would be having these problems if we'd just did like we are supposed to --act like mushrooms and let the DME's feed us BS instead of looking at our own data!

Truthfully, we do go a little overboard here. When I first started on CPAP I tended to hang out on the ASAA board (with the CPAP police and all) because I was lurking here and saw a post by somebody (no offense if you're that poster reading this!) who noted that his AHI averaged something like 0.5 higher on nights he took Acetominaphin than on nights he didn't. That was way too geeky for my little brain--I was just happy to have an AHI under 70!!!!!!!!!! Although I do admit that once the brain fog cleared, I was geeky enough to come here as my "main" place.

I know these machines are imprecise, but they do provide enough data to help us dial in our therapy as well as we do and have good, fully oxygenated nights. It was not so long ago that nobody had access to this data and the machines sounded like vacuum cleaners in heat. So I think we're way better off overall.

[mayondair]

Well, none of us would be having these problems if we'd just did like we are supposed to --act like mushrooms and let the DME's feed us BS instead of looking at our own data!

Truthfully, we do go a little overboard here. When I first started on CPAP I tended to hang out on the ASAA board (with the CPAP police and all) because I was lurking here and saw a post by somebody (no offense if you're that poster reading this!) who noted that his AHI averaged something like 0.5 higher on nights he took Acetominaphin than on nights he didn't. That was way too geeky for my little brain--I was just happy to have an AHI under 70!!!!!!!!!! Although I do admit that once the brain fog cleared, I was geeky enough to come here as my "main" place.

I know these machines are imprecise, but they do provide enough data to help us dial in our therapy as well as we do and have good, fully oxygenated nights. It was not so long ago that nobody had access to this data and the machines sounded like vacuum cleaners in heat. So I think we're way better off overall.

Don't get me wrong, I truly appreciate and admire the geeks and math whiz's here, and thank goodness we don't have those annoying CPAP police trying to cultivate mushrooms. No complaints here about going overboard, just pass the aspirin, and I'll leave some of the minutia to others.