OSA w/ BIPAP will most certainly get you a MEB, especially if your AHI's are high and the condition affects your daily duties. As you stated, and are correct, BIPAP usage is not permitted in theater, so you already have that working against you if you are trying to be retained (or for you if you are looking to separate). I started with a CPAP, then (over the course of a few months of the CPAP not working) had to transition to BIPAP with oxygen. My OSA is in conjunction with some pretty heafty lung damage.
smachinnes40, you are correct...typically the military refers sm's out to civilian sleep centers, which (in my opinion) is the way it should be. OSA is deadly and should be properly diagnosed and treated, especially when dealing with central or mixed OSA, as the cause of central OSA comes from inaccuracies/inability of the brain to tell the lungs to function while sleeping, whereas obstructive sleep apnea is caused (typically) by a blockage of the throat by collapsing of the pallet/throat/tounge etc. while sleeping. The reason the BIPAP (aka BPAP) is crucial for central or mixed OSA is because it operates more like a ventilator, not only forcing you to breathe when you go apenic, but also controls the pressure to match the resistance (titration), much unlike the CPAP that just keeps a constant pressure. In my experiences, I couldn't handle the constant pressure of the CPAP ramming air down my throat, and it usually ended up getting ripped off and thrown across the room at night. Due to the titration of the BIPAP, I can handle it now (although having the mask on my face still sucks, even after almost 2 years of treating my OSA).
If you have mixed OSA, the odds are slim that the condition is caused by medication. However, central OSA standalone can be caused or aggravated by certain meds. Also consider requesting a nocturnal pulse oximetry test to determine if the machine/treatment is working for you. Be advised to proceed with caution with requesting this test, as the results can hurt your case if you are trying to be retained.