In R4 Device could be associated with a single patient. This works for implantable devices and other devices that are permanently associated with a patient. Many devices can be associate with multiple patients over time, e.g. a wheelchair, and that association may need to be tracked for, e.g. recall purposes.

To address this, R5 Device changes that patient element to association[0..*].humanSubject. There are several issues with this approach: there is no time period associated with the association (FHIR-38637), and we end up with Device  resource containing data about multiple patients. The latter issue is particularly relevant because Device is in the patient compartment, and thus would leak PHI about other patients.

A different approach is needed, such as: creation of a new "DeviceAssociation" resource, or updates to or profiling of DeviceDispense (e.g. adding an end date, or potentially using a List for each Device of Patient assignments, including of the end date of the assignment).

(Comment 34 - imported by: Ron G. Parker)