Profile for capturing continuous glucose measurements from real-time monitoring devices (esp. rtCGM).

This profile defines the exchange of raw measurement data for the Mandatory Interoperable Value (MIV) "Continuous Glucose Measurement" which is technically defined by the ValueSet hddt-miv-continuous-glucose-measurement. This MIV is e.g. implemented by real-time Continuous Glocose Monitoring devices (rtCGM) and Automated Insulin Delivery systems (AID) that control an insulin pump from rtCGM data. Future non-invasive measuring methods will expectedly be linked with this MIV and therefore use this profile for sharing data with DiGA, too.

Obligations and Conventions:

Devices for continuously measuring glucose values may produce data with a sample rate of more than 1000 values per day (e.g. current rtCGM provide measures for glucose in interstitial fluid with up to one value per minute). For sharing such data efficently, this profile makes use of the FHIR sampledData data type. Sampled data is portioned into chunks of a fixed size (for an exception see below), with the chunk size being set by the resource server (e.g. such that 24 h of measurements fit into a single chunk). If a DiGA requests data for a period where the end time is earlier that the expected end time of the current chunk, the resource server only fills up the chunk up to the requested end time and sets the Observation.status to incomplete while Observation.effectivePeriod captures the full period of the chunk (see section "Retrieving Data" in the HDDT specification for details on chunks and missing data).

Each Continuous Glucose Measurement MUST either hold a reference to a Sensor Type And Calibration Status DeviceMetric resource or to a Personal Health Device Device resource (eXclusive OR). A reference to Sensor Type And Calibration Status MUST be provided from the Observation resource if the sensor for continuous measuring needs to be calibrated (either automatically or by the user) or if the sensor may change its calibration status over time. A change in DeviceMetric.calibration.state or a change of Device.status to inactive finalizes the current chunk and therefore is the only reason why a chunk may be smaller than the defined fixed size.

Constraints applied:

• code is constrained to the ValueSet that represents the MIV Continuous Glucose Measurement
• effective[x] is restricted to effectivePeriod and constrained as mandatory. Both a starting time and an end tme MUST be given.
• value[x] is restricted to valueSampledData. The elements valueSampledData.origin.unit, valueSampledData.origin.system, and valueSampledData.origin.code are mandatory. valueSampledData.origin.system is restricted to UCUM. Observation.valueSampledData MAY only be omitted in case of an error that accured with the measurement. In this case, Observation.dataAbsentReason MUST be provided.
• device is set to be mandatory in order to provide the DiGA with information about the sensor's calibration status and with information about the static and dynamic attributes of the Personal Health Device.