Try getting ahold of tom workman at UHMS for a list of approved equipment for HBO chambers. you can also call the folks at NAVSEA in panama city, FL who have done lots of testing on approved equipment for chamber use.
dial a flows are an option but I wouldn't recommend them for critical dives.
When I worked a multiplace chamber we had our biomed people test their baxter pumps and we used single chamber pumps during dives (the blue machines) with no problem. the monoplace is a little different because the pump is usually outside the chamber. get ahold of dick clark baromedical.com. his unit is pretty up on the latest and greatest with monoplace treatments and equipment. Kindwall in Milwaukee (?) or if you can contact Steve Reimer he is a big techno geek with lots of researchbig name in the community.
I hope I helped and didn't confuse you.
best of luck