ResMed mask settings - what changes in each type?

[skypony]

I've been wondering what actually happens in each mask setting - nasal, pillows or full face. I realize that we should match the setting with the mask type.

The reason I ask is that my son in his forties uses a nasal mask but uses the pillow setting. After I pointed out the mismatch, he tried the nasal setting but changed back to pillow setting. He says the pillow setting is more comfortable. So i wonder what is different.

[SarcasticDave94]

For ResMed machines, I think it's to help the display of corrected calculated leak rates. For Respironics machines, the setting is supposed to deal with calculated resistance.

There are some masks like the ResMed N30i that I have. N means this is a nasal mask, but the mask directions state to set your mask type to Pillows on the machine for this one. My F20, F means Full face and it gets set to full face. I have the Pillow cushions for the *30i, so mine is either Pillows/P30i or Nasal/N30i depending on which cushion I snap on the frame.

The best answer is look at the mask package on ResMed brand masks, it should state what setting is best.

[SevereApnea]

Hi skypony

That is a really good question, I have been wondering about that lately.
(I messed up my settings last week between Pillow and FFM and have no idea about the effect)

In what way did your son say the pillow setting was more comfortable? did he say this changed his pressures, flow rates, oscar charts, AHI, or was this just a subjective feeling?

Perhaps others on this board can answer this.

Does changing the setting from Pillow to Nasal to FFM or vice versa ...

1) change what the machine does, change how it delivers pressure: e.g. change the algorithm for detecting events to which it should respond, change how quickly it responds? Perhaps this is what your son was feeling?

Or 

2) just change how it detects things such as Flow Rates, Leaks, flow limitations etc, and in consequence only change what is written to the SD and displayed on the Charts.

(I remember early in my sleep tech visits she said to remember to change the settings when I change masks, no big deal, because if I forgot, she could correct for this somehow. I will ask her again at my next visit.)

[skypony]

Does changing the setting from Pillow to Nasal to FFM or vice versa ...
1) change what the machine does, change how it delivers pressure: e.g. change the algorithm for detecting events to which it should respond, change how quickly it responds? Perhaps this is what your son was feeling?
Or 
2) just change how it detects things such as Flow Rates, Leaks, flow limitations etc, and in consequence only change what is written to the SD and displayed on the Charts.

My son says that using the pillows setting while using the nasal mask made it feel easier to inhale. He said it seemed like the inhale pressure response increased more quickly while using the pillows setting. The nasal setting seemed to respond more slowly and caused him to feel like it was harder to inhale. He only tried changing it once.

[Crimson Nape]

Looking at the different mask styles shows a difference in volumetric compressibility area.  An FFM has a lot more volumetric area under seal than a Nasal Pillow.  As an analogy, compare the difference between a big truck tire and a lawnmower tire.   Adding or removing the exact same volume of air in both will have a more dramatic change in the smaller tire long before any change occurs in the larger one.  Also, along with mask settings, there is the hose setting types, at least on a Resmed.   You have Heated, Standard, Slimline, and 3 m(eter).  Each of these also have different volumetric areas, thus a different compressibility factor.

[SevereApnea]

@skypony

Thank you for the feedback. So it seems changing the Mask Settings does indeed change what the machine does and how it delivers therapy.

@ CrimsonNape

Good analogy. This would help explain the sensation felt by skypony's son.

I have read that FFM increases the Respiratory dead space when compared to nasal pillows and mask.


By inference, using the incorrect mask settings may contribute to incorrect therapy delivery, either too much or too little.

Hypothetical question: using your analogy, is it possible then to have a situation where one gets too much volume/pressure, with more PEEP than anticipated, and potentially even barotrauma? Or are the pressures we operate at too low for that? One would assume the Resmed algorithms would "bail out" before causing any damage. 

[Crimson Nape]

I will answer your question by saying that the CPAP doesn't operate at pressures that would cause harm.  Blowing up a balloon or blowing through a straw in a tall glass filled with a beverage produces the same pressures (sometimes even more).  While there is probably a latency due to the dead space, unlike my analogy, there isn't that much volumetric difference before the sensor would respond to pressure changes.  The CPAP is sampling your flow pattern at about 25-50 times a second (brand dependent).

BTW: 1 atmosphere = 1033.23 cm H₂O  

I would like to end this by saying that I don't have any factual data to support my insights, these are just my observations.  I welcome any corrections if needed.