An example to demonstrate using the bodyPosition and delta extensions

{
  "resourceType" : "Observation",
  "id" : "map-sitting",
  "extension" : [{
    "url" : "http://hl7.org/fhir/StructureDefinition/observation-bodyPosition",
    "valueCodeableConcept" : {
      "coding" : [{
        "system" : "http://snomed.info/sct",
        "code" : "33586001",
        "display" : "Sitting position (finding)"
      }]
    }
  },
  {
    "url" : "http://hl7.org/fhir/StructureDefinition/observation-delta",
    "valueCodeableConcept" : {
      "coding" : [{
        "system" : "http://snomed.info/sct",
        "code" : "1250004",
        "display" : "Decreased (qualifier value)"
      }]
    }
  }],

  "status" : "final",
  "category" : [{
    "coding" : [{
      "system" : "http://terminology.hl7.org/CodeSystem/observation-category",
      "code" : "laboratory",
      "display" : "Laboratory"
    }]
  }],
  "code" : {
    "coding" : [{
      "system" : "http://loinc.org",
      "code" : "8478-0",
      "display" : "Mean blood pressure"
    }]
  },
  "subject" : {
    "reference" : "Patient/example"
  },
  "encounter" : {
    "reference" : "Encounter/example"
  },
  "effectivePeriod" : {
    "start" : "2018-04-02T10:30:10+01:00",
    "end" : "2018-04-05T10:30:10+01:00"
  },
  "issued" : "2018-04-03T15:30:10+01:00",
  "valueQuantity" : {
    "value" : 60,
    "unit" : "mm Hg",
    "system" : "http://unitsofmeasure.org",
    "code" : "mm[Hg]"
  },
  "interpretation" : [{
    "coding" : [{
      "system" : "http://terminology.hl7.org/CodeSystem/v2-0078",
      "code" : "L",
      "display" : "Low"
    }],
    "text" : "Below low normal"
  }]
}