How to store User Fitness / Fitness Device data in FHIR?

We are currently in the process of evaluating FHIR for use as part of our medical record infrastructure. For the EHR data (Allergies, Visits, Rx, etc..) the HL7 FHIR seems to have an appropriate mapping.

However, lots of data that we deal with is related to personal Fitness - think Fitbit or Apple HealthKit:

• Active exercise (aerobic or workout): quantity, energy, heart-rate
• Routine activities such as daily steps or water consumption
• Sleep patterns/quality (odd case of inter-lapping states within the same timespan)
• Other user-provided: emotional rating, eating activity, women's health, UV

While there is the Observation resource, this still seems best fit (!) for the EHR domain. In particular, the user fitness data is not collected during a visit and is not human-verified.

The goal is to find a "standardized FIHR way" to model this sort of data.

• Use an Observation (?) with Extensions? Profiles? Domain-specific rules?

  FHIR allows extraordinary flexibility, but each extension/profile may increase the cost of being able to exchange the resource directly later.

  An explanation on the appropriate use of an FHIR resource - including when to Extend, use Profiles/tags, or encode differentiation via Coded values - would be useful.

• Define a new/custom Resource type?

  FHIR DSTU2 does not define a way to define a new Resource type. Wanting to do so may indicate that the role of resources - logical concept vs. an implementation interface? - is not understood.

• Don't use FHIR at all? Don't use FHIR except on summary interchanges?

  It could also be the case that FHIR is not suitable for our messaging format. But would it be any "worse" to go FIHRa <-> FIHRb than x <-> FIHRc when dealing with external interoperability?

The FHIR Registry did not seem to contain any User-Fitness specific Observation Profiles and none of the Proposed Resources seem to add appropriate resource-refinements.

At the end of the day, it would be nice to be able to claim to be able to - with minimal or no translation, ie. in a "standard manner" - be able to exchange User Fitness data as an FHIR stream.

Certainly the intent is to use Observation, and there's lots of projects already doing this.

There's no need for extensions, it's just a straight forward use. Note that this: " In particular the user fitness data is not collected during a visit and is not human-verified" doesn't matter. There's lots of EHR data of dubious provenance...

You just need to use the right codes, and bingo, it all works. I've provided a bit more detail to the answer here: http://www.healthintersections.com.au/?p=2487