I am so sorry that you are going through this..I too have bilateral diaphragmatic weakness, my nerve functions okay but it is my muscles that have failed. I started with shortness of breath and not being able to do anything, working became very difficult. I was hospitalized repeatedly for what docs thought was ''athmatic" issues and treated me as such but I didn't get better...I was finally transferred to a bigger hospital where they determined that it was my diaphragm, not the asthma.
To make a long story short, I am now on a ventilator full time. I used to be on BiPAP...I see that you are on CPAP. I could not tolerate CPAP for one very important reason: I could inhale with the pressures but could not exhale against them so I was placed on BiPAP instead which operates with two different pressures instead of one continuous one like CPAP. The inhaled pressure is higher than the exhaled pressure, this helps with breathing out and also prevents CO2 build up. People with muscular issues have a hard time with CPAP because they can't seem to exhale against the pressure due to the weakness in their muscles. It might be worth considering to switch to BiPAP, you will find it easier to breathe with it. I was ultimately on 20/5 for pressure (inspiratory pressure: 20 cmH20, expiratory pressure 5 cmH20) prior to being vented. I also had a huge problem with gastric distention from the BiPAP, I have severe reflux disease which did not help my situation. I found that sleeping half on my stomache helped but not always. I am glad that the PEG helps with that for you, it is just so uncomfortable
The docs also don't know why this happened to me...they have done muscle biopsies on me which have come back inconclusive for mitochonidrial disease or glycogen storage diseases such as Pompe's type II. Have the doctors done biopsies on you? That would be helpful if the docs haven't done them yet to you. With a CK like that, it could easily be a dystrophy or the above. Mine was only slightly elevated at one time, it has been normal for years now.
I really feel for you, I know how frustrating and frightening this is....before I was vented, my PFT's were only showing about 13% of my lung function, it was pathetic. My oxygenation was also not great with exertion, I was on O2 with activity. All of this was gradual...my PFT's weren't too bad at first, over the course of two years they dropped to the 13%. ABG's, same thing...but right off the bat I needed O2, BiPAP was added shortly thereafter. Two years later, I was vented because was on BiPAP and O2 24/7 with no quality of life.
If you ever want to email me, I am just a click away. Sunny