Gas measurement REFIDs for partial pressure and concentration
Paul Schluter May 8, 2013
Core Proposal
1. Specify two top-level vocabulary branches for gas concentration and partial pressure measurements:
MDC_CONC_AWAY for measurements obtained at the patient airway and MDC_CONC_GASDLV for
measurements obtained in the system supplying the gas to the patient, with or without a mechanical ventilator.1
The vocabulary branch REFID prefix is followed by the gas identifier and measurement phase on the
waveform, similar to the terms already defined ISO/IEEE 11073-10101-2004.
2. For both MDC_CONC_AWAY and MDC_CONC_GASDLV, the gas measurement site may be specified in
cases where greater semantic precision is required. These would be conveyed by OBX-20 in an HL7 V2.6
message. In each list, one of the enumerated values is identified as the ‘default’ value is OBX-20 is empty.
3. Since the expiratory _EXP and inspiratory _INSP breath phases are somewhat ambiguous, greater precision can
be specified by an enumerated value that also has a specified default value.
4. The units-of-measure are conveyed by a separate attribute, e.g. OBX-6 in an HL7 V2.6 message.
The table below lists the REFIDs for representing the concentration or partial pressure of desflurane.
CF_CODE10 REFID
152024
152084
152112
152168
{152052}
{152140}
{152200}
SysName
Concentration | |
MDC_CONC_AWAY_DESFL
Desflurane, Gas | Airway
Concentration | EndTidal |
MDC_CONC_AWAY_DESFL_ET
Desflurane, Gas | Airway
Concentration | Expiration
MDC_CONC_AWAY_DESFL_EXP
| Desflurane, Gas | Airway
Concentration | Inspiration
MDC_CONC_AWAY_DESFL_INSP
| Desflurane, Gas | Airway
Concentration | |
MDC_CONC_GASDLV_DESFL
Desflurane, Gas | Gas
Delivery System
Concentration | Expiration
MDC_CONC_GASDLV_DESFL_EXP | Desflurane, Gas | Gas
Delivery System
Concentration | Inspiration
MDC_CONC_GASDLV_DESFL_INSP | Desflurane, Gas | Gas
Delivery System
CommonTerm
Concentration airway
desflurane
Concentration airway
desflurane end tidal
Concentration airway
desflurane expiratory
Concentration airway
desflurane inspiratory
Concentration
desflurane (gas delivery
system)
Concentration airway
desflurane expiratory
(gas delivery system)
Concentration airway
desflurane inspiratory
(gas delivery system)
Description
Concentration of desflurane in airway
gas
Concentration of desflurane in airway
gas measured at the end of expiration
Concentration of desflurane in airway
gas measured during expiration
Concentration of desflurane in airway
gas measured during inspiration
Concentration of desflurane in airway
gas in the system supplying the gas to
the patient
Concentration of desflurane in airway
gas in the system supplying the gas to
the patient during expiration
Concentration of desflurane in airway
gas in the system supplying the gas to
the patient during inspiration
Notes (informative)
1.
The existing REFID prefix MDC_VENT_CONC has been changed to MDC_CONC_GASDLV on 5/8/2013 to indicate
that the term refers to the system supplying the gas to the patient, regardless of whether a ventilator is used or not. This
closely parallels the existing MDC_VENT_CONC, and, in fact, will be defined as a ‘REFID synonym’ that uses the same
numeric code (CODE10 and CF_CODE10) as the corresponding MDC_VENT_CONC term, enclosed in {wavy braces}.
The MDC_CONC_AWAY_ branch is already defined in ISO/IEEE 11073-10101-2004 and we’re simply re-using those terms.
The MDC_CONC_GASDLV_ is new but closely parallels the existing MDC_VENT_CONC_ branch except that there is a
strong expectation that the measurement site will be specified, e.g. in OBX-20 in an HL7 V2.6 message.
1
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Notes (normative)
1. The REFID prefix MDC_CONC_AWAY_ denotes gas concentration and partial pressure measurements obtained at the
patient airway (MDC_GAS_MSMT_SITE_AIRWAY) unless otherwise specified by an optional measurement location attribute,
e.g. OBX-20 in an HL7 V2.6 message, using one of the following enumerated values listed below.
MDC_GAS_MSMT_SITE_UNKNOWN
MDC_GAS_MSMT_SITE_AIRWAY
MDC_GAS_MSMT_SITE_YPIECE
MDC_GAS_MSMT_SITE_ENDOTRCH
… other breathing circuits::sites
unknown
airway adaptor (default)
Y-piece
Endotracheal
2. The REFID prefix MDC_CONC_GASDLV_ denotes gas concentration and partial pressure measurements in the system
supplying the gas to the patient obtained at the fresh gas port (MDC_GAS_MSMT_SITE_FRESHGAS) unless otherwise specified
by an optional measurement location attribute, e.g. OBX-20 in an HL7 V2.6 message, using one of the following enumerated
MDC_GAS_MSMT_SITE_UNKNOWN
MDC_GAS_MSMT_SITE_FRESHGAS
MDC_GAS_MSMT_SITE_EXHAUST
MDC_GAS_MSMT_SITE_INSP
MDC_GAS_MSMT_SITE_EXP
unknown
fresh gas (default)
exhaust
inspiratory port
expiratory port
3. The suffixes _INSP and _EXP denote the entire inspiratory and expiratory phase of a breath, respectively, and may be further
qualified by an optional attribute that specifies the calculation method.2
MDC_METHOD_CALC_UNKNOWN
MDC_METHOD_CALC_MAX
MDC_METHOD_CALC_MIN
MDC_METHOD_CALC_MEAN
MDC_METHOD_CALC_MEAN_FLOW_WEIGHTED
MDC_METHOD_CALC_MEDIAN
not otherwise specified
maximum
minimum
mean value, time-weighted
mean value, flow weighted
median value
Questions raised during our Wednesday discussion:
1.
In the current proposal, the MDC_CONC_GASDLV_ is defined as a ‘REFID synonym’ to the existing
corresponding MDC_VENT_CONC_ terms, using the same numeric CODE10 and CF_CODE10. Should we
assign new numeric codes for the MDC_CONC_GASDLV terms, at the cost of consuming the remaining few
numeric codes currently left in the SCADA partition?
2.
In the normative notes #1 and #2 above, the measurement site was left as ‘optional’ with a pre-defined default
value defined in the standard. An alternative approach would be to make the measurement site location
mandatory. Preferences? [If we decide on ‘optional’ with a pre-defined default value, the default value will be
specified in the RTMMS.]
3.
During our discussion on Wednesday, that case of where ‘no gas delivery’ occurs when intravenous anesthetics
are used. What is the best way to specify that?
2
Most observation identifiers in the SCADA partition support the two-bit disrciminator for _MIN, _MAX and _MEAN.
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Gas Parameter Usage
Exhaust
Exp
Fresh Gas
Insp
Ken Marks
GE Healthcare
October 12, 2009
Gas/Agent parameter measurement locations

Fresh Gas

Exhaust

Insp Limb

Exp Limb

Y-Piece

Endotracheal

Alveolar
Gas/Agent parameter measurement time spans & points

Insp Phase

Exp Phase

End Tidal

End Insp

Breath Cycle
Fresh Gas Ctrl
Insp Ctrl
Exp Ctrl
End Tidal Ctrl
Note: Titration mechanisms are
dependent upon the capabilities of the
gas delivery system. Purely pneumatic
delivery systems are only capable of
setting the fresh gas and cannot
provide closed loop compensation due
to the absence of sensing and
electronic/electro-mechanical control.
Electronic gas delivery systems (i.e.
electronic mixers and vaporizers) are
capable of all these mechanisms
because they have the ability for
remote control of gas settings via an
electronic interface and can be
controlled based on compensation from
measurements.
GasREFIDs.3a.docx
Gas/Agent Delivered




CH4


Ethanal

CO


end
start
flow  conc dt

end
flow dt
Note: Concentrations are measured as
partial pressures. Accuracy is affected
by barometric pressure, temperature,
and humidity.
NO2


NO


He

Ar


N2
Isoflurane


Air
Enflurane


CO2
Sevoflurane


O2
Halothane

M A C Gas
B alance Gas
M et ab o lically
U sef ul
M et ab o lically
C o nsumed
M et ab o lically
Pr o d uced
U nwant ed Gas


start
Consumption
Production
Xe
Desflurane


V o lat ile A g ent s
conc dt
Case Delivery
Total Delivery
Gas Physiological Parameters
A g ent / Gasses
end
start
conc flow
N2O




conctime  
Gas/Agent Parameter Calculations

Mean

- time wt

- flow wt

Min

Max
Gas/Agent parameter setting mechanisms







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