<Observation xmlns="http://hl7.org/fhir" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://hl7.org/fhir ../fhir-all-xsd/observation.xsd">
  <id value="demo-obs-pef-1" />
  <status value="final" />
  <code>
    <coding>
      <system value="http://loinc.org" />
      <code value="19935-6" />
      <display value="Maximum expiratory gas flow Respiratory system airway by Peak flow meter" />
    </coding>
  </code>
  <subject>
    <reference value="Patient/demo-patient-1" />
  </subject>
  <effectiveDateTime value="2018-04-11" />
  <valueQuantity>
    <value value="391" />
    <system value="http://unitsofmeasure.org" />
    <code value="L/min" />
  </valueQuantity>
  <referenceRange>
    <!-- calculated as the80% of the personali max PEF -->
    <low>
      <value value="368" />
      <system value="http://unitsofmeasure.org" />
      <code value="L/min" />
    </low>
    <text value="Personal best peak flow 460 L/min" />
  </referenceRange>
</Observation>