RE: Risks using EERS?
The EERS article references the physicians that developed and who routinely prescribe and furnish EERS modifications. I think it's always best to work with your doctor rather than experimenting with solutions that sound good. The EERS is a fairly simple concept, and lends itself to DIY experimentation provided you understand the objectives and respiratory feedback mechanisms at work. If your son has little or no central apnea as diagnosed from sleep tests, but manifests problematic CA when using PAP, then experimenting with rebreathing space is an alternative to options like ASV. Conservative addition of expiratory space either improves the problem or not, and can be fine-tuned based on experimentation. I have no argument with other members advocating doing this in cooperation with the physician.
RE: Risks using EERS?
I'm not familiar with your mask. Just make sure the elbow at the top of the mask does not have a vent. The distance from the nasal interface including mask and sections of flex tube to the whisper vent is your exhale dead-space to accumulate CO2.
RE: Risks using EERS?
That's the thing though - the "exhalation elbow" DOES have a vent. It has an array of small holes.
My diagram is not to scale, but I'd bet the air volume of that mask frame is at least as much as the air volume of 6" of Corr-a-flex. (I will measure the volume of the mask when I get a chance)
If I plug the vent on the NOSEPIECE, then I am already creating quite a fairly large deadspace (the whole mask frame). The advice I've read is to start small (6" Corr-a-flex) and extend if necessary. Plugging both vents - the nosepiece and the elbow - creates a MUCH larger deadspace.
Does that make sense?
One other question occurs to me: let's assume what I've said makes sense, and I go ahead and just plug the nosepiece vent; do I need to be concerned about the venting capacity of the elbow? I suppose it's more or less equivalent to the venting of the Whisper Valve. I could check with Philips I suppose, though I don't know how responsive they'd be to that kind of question.
Thanks