<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="NHSHC-Observation-VitalSigns" />
  <url value="https://fhir.nhs.uk/StructureDefinition/NHSHC-Observation-VitalSigns" />
  <version value="0.1.0" />
  <name value="NHSHCObservationVitalSigns" />
  <title value="NHSHC Observation - Vital Signs" />
  <status value="draft" />
  <date value="2026-07-30" />
  <publisher value="NHS England" />
  <description value="Derived profile from NHSHC-Observation for vital signs in NHS Health Check Online. Constrains category to vital-signs and provides code slices for height, weight, waist circumference, BMI, and blood pressure with systolic/diastolic components." />
  <fhirVersion value="4.0.1" />
  <kind value="resource" />
  <abstract value="false" />
  <type value="Observation" />
  <baseDefinition value="https://fhir.nhs.uk/StructureDefinition/NHSHC-Observation" />
  <derivation value="constraint" />
  <differential>
    <element id="Observation">
      <path value="Observation" />
      <constraint>
        <key value="nhshc-vs-1" />
        <severity value="error" />
        <human value="At least one of value[x], dataAbsentReason, component, or hasMember must be present." />
        <expression value="value.exists() or dataAbsentReason.exists() or component.exists() or hasMember.exists()" />
      </constraint>
    </element>
    <element id="Observation.status">
      <path value="Observation.status" />
      <min value="1" />
      <fixedCode value="final" />
    </element>
    <element id="Observation.category">
      <path value="Observation.category" />
      <min value="1" />
      <patternCodeableConcept>
        <coding>
          <system value="http://terminology.hl7.org/CodeSystem/observation-category" />
          <code value="vital-signs" />
        </coding>
      </patternCodeableConcept>
    </element>
    <element id="Observation.code">
      <path value="Observation.code" />
      <min value="1" />
      <binding>
        <strength value="required" />
        <valueSet value="https://fhir.nhs.uk/ValueSet/NHSHC-VitalSignsCode" />
      </binding>
    </element>
    <element id="Observation.subject">
      <path value="Observation.subject" />
      <min value="1" />
      <type>
        <code value="Reference" />
        <targetProfile value="https://fhir.hl7.org.uk/StructureDefinition/UKCore-Patient" />
      </type>
    </element>
    <element id="Observation.encounter">
      <path value="Observation.encounter" />
      <min value="1" />
      <type>
        <code value="Reference" />
        <targetProfile value="https://fhir.nhs.uk/StructureDefinition/NHSHC-Encounter" />
      </type>
    </element>
    <element id="Observation.effective[x]">
      <path value="Observation.effective[x]" />
      <min value="1" />
    </element>
    <element id="Observation.performer">
      <path value="Observation.performer" />
      <min value="1" />
      <type>
        <code value="Reference" />
        <targetProfile value="https://fhir.hl7.org.uk/StructureDefinition/UKCore-Organization" />
        <targetProfile value="https://fhir.hl7.org.uk/StructureDefinition/UKCore-Practitioner" />
      </type>
    </element>
    <element id="Observation.component">
      <path value="Observation.component" />
      <slicing>
        <discriminator>
          <type value="pattern" />
          <path value="code" />
        </discriminator>
        <description value="Slice by blood pressure component — systolic and diastolic" />
        <rules value="open" />
      </slicing>
    </element>
    <element id="Observation.component:systolicBloodPressure">
      <path value="Observation.component" />
      <sliceName value="systolicBloodPressure" />
      <min value="0" />
      <max value="1" />
    </element>
    <element id="Observation.component:systolicBloodPressure.code">
      <path value="Observation.component.code" />
      <binding>
        <strength value="required" />
        <valueSet value="https://fhir.nhs.uk/ValueSet/NHSHC-SystolicBloodPressureCode" />
      </binding>
    </element>
    <element id="Observation.component:diastolicBloodPressure">
      <path value="Observation.component" />
      <sliceName value="diastolicBloodPressure" />
      <min value="0" />
      <max value="1" />
    </element>
    <element id="Observation.component:diastolicBloodPressure.code">
      <path value="Observation.component.code" />
      <binding>
        <strength value="required" />
        <valueSet value="https://fhir.nhs.uk/ValueSet/NHSHC-DiastolicBloodPressureCode" />
      </binding>
    </element>
  </differential>
</StructureDefinition>