(07-29-2015, 02:40 PM)Sleeprider Wrote:(07-29-2015, 12:13 PM)AndyB Wrote: Sleeprider, what are your general thoughts on EPR? Your comment above suggests that you endorse it, at least in some circumstances.
I turned EPR and Ramp off very early in my new adventure with CPAP therapy, thinking they were promoting CAs, of which I had many early on, and still do frequently (my AHI is usually comprised 50-75% by CAs, with the balance being hypopneas).
I'm wondering whether I should turn EPR back on (it was set at 2cmH2O during my sleep study).
That's a good question, and since it seems to affect individuals differently, there is no right or wrong answer. When EPR makes you more comfortable, and makes exhalation easier, it is certainly a good thing. The problem with it is that it actually turns your CPAP into a limited BPAP (bilevel). The fundamental principle of BPAP titration is the EPAP/IPAP must be high enough to support the respiratory system and prevent OA. EPAP/IPAP are both from minimum pressure (usually 4.0/8.0) to eliminate OA. IPAP is then increased to relieve H, RERA and snores, and the PS can also be increased to optimize respiratory perfusion.
In CPAP and APAP, where EPR seems to have problems is when exhalation relief pressure falls below the threshold necessary to prevent OA and hypopnea from occlusion of the throat tissue. Because it is a subtraction from IPAP, you need to set the minimum IPAP at a level that you do not trigger OA and H at the reduced EPAP pressure. When it is set right, EPR provides exhalation comfort and still supports the respiratory system. However, EPR can have a real effect on apnea, if the IPAP is too low and EPR is too great. Since most patients are not titrated on EPR, there is a risk of that happening.
Changing pressure also seems to correlate with increased CA in some people. It could be due to micro arousals, CO2 washout, or the unstable airway at too low of an exhale pressure...I don't know, but it's common. CA events are not much of a concern unless they are clustered or abundant. Almost anyone can be induced to have CA by too much pressure support (pressure difference between EPAP/IPAP) which washes out too much CO2. I suspect that is why Resmed limits EPR to 3.0 cm, and Philips limits Aflex/Cflex to 2.0; that pressure difference is less than the minimum PS for most bilevel and should minimize that problem. A little bit of CA is not bad if the RDI is otherwise low, and that is the tradeoff I accept in my own therapy.
Sorry for the long answer.
Sorry?? I am very grateful to have the benefit of your knowledge and experience. Thank you, Sleeprider!