Sarah,

HBO is adjunctive therapy for chronic refractory osteomyelitis. So from a documentation standpoint, you would want to document how the patient was initially diagnosed with acute osteomyelitis (imaging, bone culture, pathology report, etc), how the patient was treated (surgical debridement of the diseased bone, IV abx/Oral abx) and why you believe the patient now has chronic refractory osteomyelitis. So your are right about discussing failed therapy for 4-6 weeks, continued elevation of CRP or ESR and the like. But more to your question, if the skin is healed, can the bone still be infected and would you consider using HBO? I think the important point is to remember that osteomyelitis (acute or chronic) is a surgical problem and as such surgery and antibiotics would be expected to but used for both acute and chronic osteomyelitis. However, if as you describe, the patient is not a good surgical candidate, then I think you could argue that HBO could be use adjunctively to IV/Oral abx but it would necessitate clearly stating why surgery is contraindicated or not needed, agreement from ID that the patient has chronic osteo and needs ongoing abx, and how HBO is being used to resolve the infection. This approach may not make you audit proof but at least you will have described a rational approach to why HBO is being used on your patient.

https://www.uhms.org/10-osteomyelitis-refractory.html