Thoracic back pain with "minor" pressure elevations

So I have been steady state at 15 cm water (EPR = 3) for about 2 months. The sleep study I had said I achieved better REM at 17 vs 15 but I found the pressure at 17 just too uncomfortable initially. I keep trying to go back up to 17 but failing. I am currently trying to go from 15 to 16 (AutoPAP) and it is raising it to 16 each night. I am sleeping better, feel better, but my back is very sore in the morning. Has anyone else had pain associated with such a seemly small increase in pressure? Note that I don't noticed the pressure at all until I turn the machine off and don't have any pain while sleeping. It's when I get up and start moving around and it seems to wear off as the day goes on.

Prior to therapy, I mainly slept on my side. Once I started wearing a mask connected to a machine, I found I was pretty much forced to sleep on my back. I would have tremendous pain in my lower back after a few hours on many nights. I found that elevating my head on a wedge shaped pillow with yet another pillow on top that so that my head is up about a foot relieves most back issues. I didn't associated this issue with pressure as I am on a Bipap 25/21. After finding the correct mask I could sleep on my side if I choose but I almost never do... I stay on my back as I am comfortable for the most part.

I can't imagine why CPAP pressure would have anything to do with back pain, nor have I ever heard of it happening. However, what could be happening is that the increase of pressure has stabilised your breathing better which has lead to your sleep being less disturbed. This could mean that you are moving a lot less in your sleep which is thus causing the back pain. This could still be true if it was just REM sleep that is improved because in REM sleep most of your muscles are super relaxed to stop you acting out your dreams. It's a bit like you body anaesthetising itself. If you had not been having solid REM and now you are, causing you to be more still, then this might have an effect. I'm really just guessing here. Unfortunately I have no great ideas for fixing it. Just be careful about medicating for it, because if you take muscle relaxants for your back they may also relax your airway making your OSA worse, and then you need more than 17 cmH2O to keep you breathing properly.

Well I'm not a Sleep Tech, but I am a PT. I was stumped by your initial question-not knowing much about this strange new world of sleep apnea devices. But ultimately I think sleeptech is right. This could be especially true if you are a side sleeper. Side sleeping causes you to rotate your lower shoulder forward, thus placing your thoracic spine in rotation for a prolonged period of time. If you are at all stiff in your thoracic spine (most people are), it will hurt most wherever you rotate most. This would be at the thoracic-lumbar junction, which in lay-terms would be just south of your shoulder blades and spreading outwards. I'm just speculating here based on the limited info you gave us. If this is the case, I don't think muscle relaxants are the answer. Rather some range of motion exercises might be more beneficial, as well as investigating your position on your mattress. If the mattress is too firm or too soft, it can exacerbate the problem.