http://hl7.org/fhir/StructureDefinition/messageheader-response-request|5.2.0

This extension enables the capability currently available through MSH-16 (Application Level acknowledgement) in HL7 Version 2 to declare at a message instance level whether a response is required or only upon error or success, or never.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/code
Extension.value[x].binding.valueSethttp://hl7.org/fhir/ValueSet/messageheader-response-request