Personal Health Device Implementation Guide
1.0.0 - STU 1

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## NaN Example

This example results when the device reports a NaN (not a number). The important aspect of this case is that the value element is absent and replaced by a dataAbsentReason element.

Note there is no logical id in this resource as this resource is being uploaded to the server in a create operation. The server will create the logical id and return it to the sender in the response. There is also no reference to the coincident time stamp since this observation is generated by a device that is streaming data and reporting no time stamp. The time stamp is taken to be the time of reception by the gateway.

    {
    	"resourceType": "Observation",
    	"meta": {
    		"profile": [
    			"http://hl7.org/fhir/uv/phd/StructureDefinition/PhdNumericObservation"
    		]
    	},
    	"extension": [
    		{
    			"url": "http://hl7.org/fhir/StructureDefinition/observation-gatewayDevice",
    			"valueReference": {
    				"reference": "Device/ecde3d4e58532d31.000000000000"	// Already on the server
    			}
    		}
    	],
    	"status": "final",
    	"code": {
    		"coding": [
    			{
    				"system": "urn:iso:std:iso:11073:10101",
    				"code": "150320"
    			}
    		],
    		"text": "MDC_SAT_O2_QUAL: Pulsatile quality"
    	},
    	"subject": {
    		"reference": "Patient/sisansarahId.1.2.3.4.5.6.7.8.10"	// Already on the server
    	},
    	"effectiveDateTime": "2018-11-11T19:07:48-05:00",
    	"dataAbsentReason": {
    		"coding": [
    			{
    				"system": "http://terminology.hl7.org/CodeSystem/data-absent-reason",
    				"code": "not-a-number"
    			}
    		],
    		"text": "not-a-number (Not a number)"
    	},
    	"device": {
    		"reference": "Device/74E8FFFEFF051C00.001C05FFE874"	// Already on the server
    	}
    	// Streamed data. This PHD sent no time stamp with its measurement and therefore there is no
    	// coincident time stamp Observation reference.
    }