Current blockchain technologies aren’t scalable enough for storing clinical data. The volumes are just way too high. And blockchain doesn’t really give us anything we need. There are only a limited number of payers and providers, and they can all trust each other to an extent based on legal agreements. Or at least they can trust a smaller set of organizations which act as centralized data aggregators and network hubs. For compliance reasons we also need the ability to permanently and completely delete patient records, which is problematic with blockchains that only allow appending blocks.
HL7 standards don’t really dictate any particular architecture, they just define public APIs and interoperability formats. The data models are inherently complex because the problem domain is complex; attempts at simplification tend to cut off important use cases.
This is an interesting commentary on using “blockchains”. I was reading about hosting the EMR’s on the blockchains, which would serve as an immutable record. The idea is mostly grandstanding; I don’t have access to it now but I plan to look into this more closely. It requires a deep dive.