Pillow vs FFM, pressure conversion formula?

[Sleep2Snore]

Doctors generally categorise people into groups.

1 Those that do not have a clue what they are talking about.
2 Those that know what they are talking about and might know more than them.
3 Those that might find out how bad a treatment they are really giving you (so they do not want you looking at data).
4 Those he knows might do better than they are at setting up the pressures and they do not want you doing it.
5 Those that will adjust things and then blame doctor for doing it.
6 Those that are going to adjust their machines anyway, so doctor has to insist you do not do it.  This will keep doctor away from the fact he said it was okay to do it. Now the doctor is bot at fault for allowing you to play with pressures and data.

Doctors are always worried that you can do better than they do, or cause them extra work by having to set up a machine again.

I would tell Doctor #2 to go take a hike.
If you said you were going to change pressures, you are challenging his authority.

When I was in hospital lately, I couldn't stand the pressure so I asked them to come turn it down slightly.
I was just along the corridor from them, I waited two days, then adjusted the machine myself.
I also needed a better humidifier, I phoned them and they said they would send one up.
I had to send someone down to get it.  It was only after I got the humidifier did anyone appear.
I told them I had adjusted the machine, I couldn't wait any longer, this was met with "Oh, okay, if it needs adjusting back again you know what you are doing then."
 I don't know, they will not let you do anything, then after you do they don't appear to care!

Now I have a new machine they didn't know what to set it at, so they asked me what pressure I thought it should be at.
They checked the old machine and decided what it should be set to.  10 to 20 I was going to say a slightly higher low setting, but when they said that I just said "Fine, if it needs adjusting I will adjust it to suit."
I thought I was back at school the lecture I got  
Their parting words were "Now, do not adjust the machine!"
I said "Yeah, yeah, whatever, if it needs to be done and I am not allowed to do it you are going to be very busy."
They also said I should not be looking at the data in Sleepyhead (They use another program and it clashes or something) but I will anyway, if the program they use clashes they can change to Sleepyhead.    

I have had my fill of doctors lately, I was in hospital to long and I saw to many things to worry about them and how they feel about me adjusting a machine so I can get better treatment.
I should have died and did, but they made the mistake of bringing me back.
I am to straight talking for some doctors now, others are fine and treat me like they should, a human and not a lump of meat that knows nothing.  To be fair, most doctors are fine, but if I meet a self interested arrogant, obnoxious doctor he/she is put right into his place these days.  I think the word has got round, most of them are all smiles these days.
There must be a note on my file or something  

The thing at the end of the day Kiwi, you phoned his office and he was out, you can't wait two days until he decides to be available, so you have to do something so you can use your machine. 
Phone on Monday and say you had to adjust it as you couldn't use it and he was not around to adjust it or give you advice.  See what he says then!

[Sleepster]

Haha… yeah, that's okay though, I only need an approximation - just enough to overcome the issue of needing 'permission' to adjust my own machine, which I should never have 'given up' in the first place. I really appreciate your help! The solution is close - I think I've got this!

I'm a bit late to the party, but I want to contribute my thoughts, anyway. You've got the relationship between pressure and speed, but that is precisely the relationship programmed into the machine to account for the change from a FFM to a nasal pillows mask, so when you made that change on your machine's setting from FFM to pillows you made the pressure adjustment you're asking about. It's not a large pressure change, a fraction of a centimeter.

I suspect what you feel when you switch from FFM to pillows is not a difference in pressure, but a difference in air speed. The air is going to enter your nostrils at a much higher speed than before, it has to, because the air has to pass through a much smaller opening. This increased air speed is, I suspect, what's creating the uncomfortable feeling you're experiencing.

[kiwii]

...This increased air speed is, I suspect, what's creating the uncomfortable feeling you're experiencing.

Thank you for that explanation. I set the machine to Pillows, put on my old Swift FX, and watched some videos while sitting upright. I haven't looked at the charts yet but, judging from the machine's screen, the pressure did not go below the lowest setting (EPAP?) which I guess makes sense.

It didn't take long to feel comfortable breathing with the mask - a good lesson for any beginners!

However, it did cause discomfort in my ears and also I could feel the air going down my throat. After maybe an hour I had to take off the mask to relieve the pressure in my ears. They still feel mildly uncomfortable a couple of hours later and my tummy is very uncomfortable despite taking Gas-X.

Does this still sound like air speed? Oh, and I set it to Pillows in the hidden mode. I don't know if that makes any difference.

If the lowest setting is fixed at a rate close to your needs, can the machine's algorithm even make an adjustment to account for the change in masks? Would I need to have the setting below my needs? (my lowest setting was moved up to 8 because I was having a lot of events getting up to the pressure that I needed)

[kiwii]

Sleep2Snore, the story of your experience absolutely floors me. Thank you for the encouragement!

[kiwii]

Do the mask pressure charts in sleepyhead give any clue/difference between the two different masks ? I know it is not a true reading and is calculated from the pressure at the machine but it is performing the calculation knowing the leak rate and the mask type ?


Jason

Jason, I'm hoping someone has the answer to your question. My guess is that it must, although it may take being on a machine that has a wider open setting than mine currently has.

[Sleepster]

It didn't take long to feel comfortable breathing with the mask - a good lesson for any beginners!

I think you just need time to get used to the difference between the way the two masks feel. You don't need to make any adjustments to the pressure.

The thing with the ears is harmless and something that will subside as you adapt.

If the bloating continues let us and your doctor know. Some people recommend a cervical collar for that, but your doctor may also want to make adjustments to your pressure to treat it.

[kiwii]

Sleepster, I had to remove the mask because I could not tolerate the ear-thing.

I'll just use the SimPlus until Monday. If Dr 2 calls, great. If not, well, I'll re-evaluate if I still feel obligated to keep my promise or not.

I'm going to guess that reducing the pressure a bit will resolve the issues. When my husband is home we'll crunch the numbers and see what they reveal.

[AshSF]

Here’s my anecdotal evidence. Started using a f10 ffm with 4-20 range. Got it down to 7-14. Then switched to a p10. (Btw resistance is futile). Started titration pressure again. Switched to constant pressure. And I did a final titration 2+ years into Cpap use last month. Now I sleep on constant 7cm with no flex of any kind. And I feel really good.

My theory on this is:
If your problem is nasal geometry (nasal valve collapse, inflamed tirbinates leading to less cross section for air to flow), nasal pillows are much more effective than ffm so your pressure can be reduced a lot, as in my case.

If your problem is in the throat region, then there isn’t much pressure lowering while going from ffm to pillows.

If you are looking at the engineering side of this, you shouldn’t be looking at air flow but rather pressure losses on piping bends. Air flow is kept up to maintain pressure by the stepper motor and the pneumotachometer

[Doza]

I can't speak about the FFM, but I can tell you that pressure between the Swift FX and P10 feel quite different at first.  
The first time I put the Swift on and got it going (no ramp and was at a min of 8 at the time), I felt like my brains were being blown out.  It settled down pretty quickly though, and can go from one to the other without any dramas. 
The venting is very different between them which might account for the blowpower of the Swift as well as the Swift's XS sizing being noticeably larger than the P10's..
My auto sorts it out well enough.

[kiwii]

Thank you for this AshSF, I will mention it to my husband. The equation he was looking at was dealing with changes in area. I should remember the name of the formula, but I cannot bring it to mind. I don't recognize the wording that you've used, but my brain is absolute mush right now. I *really* need some sleep!!!!!