Creating the Ventilator Availability Group

Situational Awareness for Novel Epidemic Response, published by HL7 International / Public Health. This guide is not an authorized publication; it is the continuous build for version 1.0.1 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/fhir-saner/ and changes regularly. See the Directory of published versions

Making the Group Optional for Reporting
Describing the Group
Define each Population
Ventilator Supplies

When tracking ventilators, many EHR systems may not directly track ventilator devices in the hospital. Ventilator use is indirectly determined in this measure based on the presence of observations that would only be present in the patient chart when the patient is being ventilated. Direct tracking of ventilator devices and telemetry is typically the purview of other systems used for asset management or ICU central monitoring. The number of ventilator devices is generally known, and does not change frequently, and so implementers may provide an alternate mechanism (e.g., a defined parameter) to supply this value. Thus, while this guide provides an expression for identifying ventilators in this sample measure, more user feedback on how to obtain this value is desired.

Making the Group Optional for Reporting

* with group[3]
** extension[MeasureExpectation].valueCode = http://terminology.hl7.org/CodeSystem/conformance-expectation#SHOULD

Describing the Group

The first step in describing the group is to identify it with a code. Measure developers will generally define the codes used for the measure groups they create.

 * with group[3].code do
 ** coding = MeasureGroupSystem#Ventilators
 ** coding.display = "Ventilators"
 ** text = "Ventilator Reporting"

Measure Group Attributes

Each group must be described by the Measure Group Attributes extension to further describe the measure group content.

The first step in describing these attributes is to indicate how the measure is scored. The ventilator measure is a measure of available and utilized capacity, so the capacity scoring is used.

 * with group[3].extension[groupAtts] do
 ** extension[scoring].valueCodeableConcept = http://hl7.org/fhir/uv/saner/CodeSystem/PublicHealthMeasureScoring#capacity

Next, the measure describes the type of measure (e.g., structure, process or outcome). This measure is a structural measure, representing the current ventilator capacity and availability in a hospital.

 ** extension[type].valueCodeableConcept = http://terminology.hl7.org/CodeSystem/measure-type#structure

An indication of how the scoring system works is then provided (e.g., increase, decrease). The scoring on capacity measures reports on utilization, so lower numbers are “better”, with regard to utilization.

 ** extension[improvementNotation].valueCodeableConcept = http://terminology.hl7.org/CodeSystem/measure-improvement-notation#decrease

The type of resource associated with this measure expresses what to count for the measure implementer. For this case, it is a patients with an active inpatient or ED Encounter. This tells “what to count”. The ResourceType slice identifies the FHIR Resource which is likely being counted. The SNOMED slice can be used to provide a more fine grained code to describe the resource (e.g. a specific condition, medication, type of encounter, patient, practitioner, et cetera), and might be a code found or used to find resources based on the code field associated with it. This information is descriptive, rather than semantically exact content. It is meant to convey information to an implementer, rather than to automated systems.

 ** with extension[subject] do
 *** valueCodeableConcept.coding[ResourceType] = http://hl7.org/fhir/resource-types#Device
 *** valueCodeableConcept.coding[Snomed] = http://snomed.info/sct#257463002 "Ventilator Outlet"
 *** valueCodeableConcept.text = "Ventilator capacity"

NOTE: The coding of this measure reports that it counts ventilator outlets. During the early period of the COVID Epidemic, a facilities in New York City and elsewhere used a single ventilator to support more than one patient. In the US, the FDA issued an emergency use authorization for such use. CDC issued guidance describing the counting of Bi-level Positive Airway Pressure (BiPAP) equipment when such equipment and procedures were available within the facility. This guide makes NO recommendation about the appropriateness of this use, but notes this so that measure developers will consider such cases when creating measures.

Capacity measures are point in time measures.

 ** extension[rateAggregation].valueString = "point-in-time"

Define each Population

The population definitions provide both descriptive and computable content for the measure, describing it to the implementer, and to the system that automates its computation. Capacity measures have three or four populations:

An optional initial population from which the other populations are found.
The denominator population, which may simply be the initial population (this is the case for ventilators).
The numerator population, which usually applies a filter to the initial population.
The numerator-complement population, which represents the population in the denominator not found in the numerator.

The initial population is not used in the Ventilators measure because it would be the same as the denominator population so the measure starts with the denominator.

 * with group[3].population[0] do
 ** with code do
 *** coding[0] = http://hl7.org/fhir/uv/saner/CodeSystem/MeasuredValues#numVent "Mechanical Ventilators"
 *** coding[1] = http://terminology.hl7.org/CodeSystem/measure-population#denominator
 *** text = "Total number of ventilators"
 ** description = "Count of all ventilators that can support patient care, whether or not they are presently in use."

 * with group[3].population[1] do
 ** with code do
 *** coding[0] = http://hl7.org/fhir/uv/saner/CodeSystem/MeasuredValues#numVentUse "Mechanical Ventilators in Use"
 *** coding[1] = http://terminology.hl7.org/CodeSystem/measure-population#numerator
 *** text = "Total number of ventilators in use"
 ** description = "Count of all ventilators in use."

 * with group[3].population[2] do
 ** with code do
 *** coding[0] = http://hl7.org/fhir/uv/saner/CodeSystem/MeasuredValues#numVentAvail "Mechanical Ventilators Available"
 *** coding[1] = http://hl7.org/fhir/uv/saner/CodeSystem/MeasurePopulationSystem#numerator-complement
 *** text = "Total number of ventilators not presently in use."
 ** description = "Count of all ventilators not presently in use."

Describe the Evaluation Criteria

Name the criteria and give a description for what qualifies to be included.

 * with group[3].population[0].criteria do
 ** name = "NumVent"
 ** description = """Computes the total number of ventilators from the previously reported MeasureReport"""

 * with group[3].population[1].criteria do
 ** name = "NumVentUse"
 ** description = """Identifies the number of ventilators in use by counting Patient with an Observation
 or Procedure resource from an appropriate value set indicating ventilator use."""

 * with group[3].population[2].criteria do
 ** name = "NumVentAvail"
 ** description = """Computes the number of ventilators available by substracting the number of ventilators in use
 determined by population 1 from thee total number of ventilators given in population 0"""

Provide the Computable Content

The computable content “implements” the automated computation of the measure.

 * with group[3].population[0].criteria do
 ** language = #text/fhirpath
 ** expression = "%PriorReport.group[3].population[0].count"

NOTE: The following population is also important for computing the stratification of an earlier measure group by ventilator use. It’s important that what it counts are Patients with an observation or procedure implying ventilator use.

  * with group[3].population[1].criteria do
 ** language = #text/fhirpath
 ** expression = """
       // Find all active encounters
       findAll('Encounter',
        including('subject'),
        with('status').equalTo('in-progress'|'finished'),
        with('date').within(%ReportingPeriod)
       ).onServers(%Base)
       // Filter to patients
       .select(resource as Patient)
       .where(
         iif(
           whereExists('Observation',
             with('status').equalTo('registered'|'preliminary'|'final'|'amended'|'corrected'),
             with('patient').equalTo($this.id),
             with('verificationStatus').notEqualTo('refuted'|'entered-in-error'),
             with('date').within(%ReportingPeriod),
             with('code').in(%VentilatorObservations.url)
           ).onServers(%Base),
           true,
           whereExists('Procedure',
             with('status').equalTo('in-progress'|'completed'),
             with('patient').equalTo($this.id),
             with('date').within(%ReportingPeriod),
             with('code').in(%VentilatorProcedures.url)
           ).onServers(%Base)
         )
       )
 """

 // Compute ventilators available as total number of ventilators - ventilators in use.
 * with group[3].population[2].criteria do
 ** language = #text/fhirpath
 ** expression = "%NumVent - %NumVentUse.count()"

Ventilator Supplies

With any resources, including ventilators, require a supply of additional equipment in order to maintain operations. In the case of ventilators, this might include tubing which needs replacement for each patient using the ventilator. The adequacy of the ventilator tubing supply can be reported using an availability measure. The simplest measure of adequacy of supply would be provided using the example below; either there is tubing available, or it is not.

Describing the Ventilator Supplies Group

 * with group[3].code do
 ** coding = MeasureGroupSystem#VentilatorSupplies
 ** coding.display = "Ventilator Supplies"
 ** text = "Ventilator Supplies Reporting"

Ventilator Supplies Measure Group Attributes

The Measure Group Attributes for this group appears below.

This is an availability measure:

 * with group[4].extension[groupAtts] do
 ** extension[scoring].valueCodeableConcept = http://hl7.org/fhir/uv/saner/CodeSystem/PublicHealthMeasureScoring#availability

This measure is a structural measure, representing the current ventilator supply availability in a hospital.

 ** extension[type].valueCodeableConcept = http://terminology.hl7.org/CodeSystem/measure-type#structure

Higher numbers (1) represent availability, and so are “better” for this case, but it may vary depending on the question.

 ** extension[improvementNotation].valueCodeableConcept = http://terminology.hl7.org/CodeSystem/measure-improvement-notation#increase

This example reports on availability of devices (most non-medication supplies are devices)

 ** with extension[subject] do
 *** valueCodeableConcept.coding[ResourceType] = http://hl7.org/fhir/resource-types#Device
 *** valueCodeableConcept.coding[Snomed] = http://snomed.info/sct#26412008 "Endotracheal Tube"
 *** valueCodeableConcept.text = "Endotracheal Tube"

Supplies are normally tracked in an inventory management system, and these systems do not typically track supplies an an individual unit level, but rather as a quantity of a specific kind of device that is described. FHIR does not presently have a resource that tracks supplies at the quantity level. Supply adequacy is a determination that is made at the facility level, possibly through some automated logic.

 *** extension[subjectValueSet].valueReference.reference = http://example.com/ventilatorSupplies

 * with group[4].population[0] do
 ** with code do
 *** coding[0] = http://hl7.org/fhir/uv/saner/CodeSystem/MeasuredValues#VentSuppliesAdequate "Ventilator Supplies"
 *** coding[1] = http://terminology.hl7.org/CodeSystem/measure-population#denominator
 *** text = "Adequacey of ventilator supplies"
 ** description = "Represents the adequacy of ventilator supplies"

Lastly, encode the logic that determines the adequacy of ventilator supplies. That logic is not shown below because it varies by facility. Knowing the quantity of supplies on hand is a critical input for that decision, but adequacy of supply is also based on the current or projected rate of consumption, and the lead time for obtaining replacements.

 ** with criteria do
 *** language = #text/fhirpath
 *** name = "VentSuppliesAdequate"
 *** description = """Computes the adequecay of ventilator supplies from inventory"""
 *** expression = """See text above"""