[Treatment] Relationship between EPR and Flow Limitations

[donsburg]

Hi OpalRose, 

Thanks for your response    

I have gone back and re-read the post and the links but I'm still not quite understanding the why - on a physiological level. The closest I could find was in the Barry Krakov link, where it says:

"Still, it would be nice to have a respiratory physiologist explain to us why the larger gap is so effective. As an internist and sleep medicine physician, there are only two obvious theories that stand out. First, what if we’ve always assumed, mistakenly, that airway pressure had to be constant for both inspiration and expiration? I think it has already been proven by other researchers that you actually need higher pressure to keep the airway pinned open on inspiration and a lower pressure on expiration. If that’s so, then is bilevel the best system because it provides the exact pressure you need (not too much and not too little) during expiration.

The second idea relates more to the psychophysiological response to PAP therapy. Maybe the larger gradient simply gives the patient a distinctly more comfortable feeling, because the lower pressure creates a feeling so much closer to breathing normally (without PAP). If this theory were accurate, though, it would imply that over time as you get used to any sort of PAP therapy, then perhaps the gap would narrow and eventually you could use fixed CPAP again. If this were true, I would expect more people to eventually adapt to fixed CPAP pressure, and I don’t believe that’s occurring."

I don't think that quite covers what's actually happening in the body, and why Pressure Support (or a difference between IPAP and EPAP) would help specifically with Flow Limitations. I expect I'm missing something that may be obvious to someone with a deeper knowledge of the topic...?

[SarcasticDave94]

With either CPAP and EPR or a bilevel with PS, when the device transitions back to lower exhale EPAP pressures, due to the pressure differential of the higher inhale IPAP from EPR or PS, there's a natural exhale advantage via that differential. This helps with keeping the airway patent as in "Medicine:
(of a vessel, duct, or aperture) open and unobstructed; failing to close.
"the patient is usually left with a patent vessel", while at the same time should add comfort to the user. It helps maintain the open, unrestricted aspect.

[donsburg]

Ah I see, so sort of: on the inhale the lungs get filled at a pressure of (say) 15, and then the system pressure drops to 10 which helps the air in the lungs rush out down that pressure gradient. I think that makes sense, thank you

[SarcasticDave94]

Welcome