Measure ID

Percentage of cases with mean fresh gas flow (FGF) equal to, or less than 3L/min, during administration of halogenated hydrocarbons and/or nitrous oxide.

This measure considers Fresh Gas Flow (FGF) during administration of halogenated hydrocarbons and/or nitrous oxide, as an indirect measure of anesthetic gas waste. For a given case, this measure will include the maintenance period of anesthesia, defined as the time between placement of an endotracheal tube or supraglottic airway and removal of the endotracheal tube or supraglottic airway. 

Measure Type

Halogenated agents and nitrous oxide leaking or vented into the atmosphere are environmental pollutants.  Reducing fresh gas flows can reduce cost of anesthesia without compromising patient care.

Measure Time Period
  • Cases with an ETT or LMA as determined by Anesthesia Technique: General value_codes 1,2,3,6
  • Patients administered halogenated hydrocarbons and/or nitrous oxide, for greater than or equal to 30 minutes from placement of the airway device to removal of the airway device.
  • Cases without an ETT or LMA placed (determined by Anesthesia Technique: General value_codes 0,4,5)
  • Cases with documentation of Nitric Oxide use
  • Cases in which halogenated hydrocarbons and nitrous oxide are NOT used
  • Cases with maintenance period < 30 minutes
  • Cases with >20% of Fresh Gas Flow values manually entered during the case (automated capture of FGF required)
Success Criteria

Mean FGF equal to, or less than 3L/minute when inspired halogenated hydrocarbons is >0.2%, or nitrous oxide FGF >0.2L/min, during the maintenance period of anesthesia.

Other Measure Details

Measure Start:

  1. Intubation. If not available, then
  2. Induction End

Measure End:

  1. Latest Extubation Time. If not available, then
  2. Latest LMA Removal Time. If not available, then
  3. Procedure End. If not available
  4. Patient Out of Room. If not available, then
  5. Anesthesia End.


  • If Fresh Gas Flow Total (MPOG Concept ID: 3214) is documented for the case, this concept will be used to determine success in the setting of halogenated agents or nitrous oxide use.
  • If Fresh Gas Flow Total (MPOG Concept ID: 3214) is not documented for the case, MPOG will calculate Fresh Gas Flow: Flows Oxygen (ID: 3215) + Flows Air (ID: 3220) + Flows Nitrous Oxide (ID: 3225)
  • If there are no fresh gas flows documented on the case or the variables are mapped to the incorrect MPOG concept, the case will be excluded. There must be fresh gas flows documented for 80% of the total time the inspired agent is running to be included (minute-by-minute flow values).
  • There must be at least 30 minutes of Nitrous Oxide flow >0L or inspired halogenated hydrocarbons >0% during the maintenance period. Maintenance period is defined as measure start to measure end. See Appendix A for diagram.
  • Of the total number of minutes of gas flows documented, at least 80% of the Fresh Gas Flow values must be machine data captured for the case to be included. Any manually entered fresh gas flow or agent values will be included in the calculation of mean FGF if this threshold is met and the case is included.
  • If there is a gap in documentation for fresh gas flow values, each value is valid for up to one minute.
  • When calculating the mean Fresh Gas Flow, the sum of all flows will be added and divided by the total number of minutes that have a documented gas flow. If there are 30 cumulative minutes of halogenated gas documented, but only 24 minutes of fresh gas flow, the mean will be calculated using the 24 minutes of fresh gas flow.  See Appendix B for diagrams depicting how fresh gas flow is calculated within the maintenance period.
  • If multiple flow values for oxygen (3215), air (3220), and Nitrous Oxide (3225) occur at different second intervals in the same minute, all values will be aligned to the beginning of the minute and the one documented first will be used. For example, if 1 L/min of oxygen flow was documented at 13:02:30 and 2 L/min of air flow was documented at 13:02:32, both would be assigned 13:02 as the documented time and the total FGF would equal 3 L/min for that minute.
  • Values for flows and gases will be assessed and considered artifact if inside the following ranges:
    • Nitrous Oxide Flows: <0.2 L/min
    • Isoflurane Insp %: <0.3%
    • Sevoflurane Insp %: <0.4%
    • Desflurane Insp %: <1.2%
    • Nitrous Oxide Insp % <20%
Provider Attribution

All providers signed in for at least 30 minutes during the time when halogenated agent or nitrous oxide are documented.

Method for determining Responsible Provider:

All providers signed in while patients are administered halogenated hydrocarbons, and/or nitrous oxide, for more than, or equal to, 30 minutes from placement of the airway device to removal of the airway device. See ‘Other Measure Build Details’ section for algorithm for determining measure start and end times.

MPOG Concept Used


  • 50695    Categorized Note - Intubation
  • 50117    Intubation/Airway - Approach
  • 50205    Intubation Tube Note
  • 50121    Intubation ETT Stylet Used
  • 50122    Intubation ETT Size
  • 50123    Intubation ETT Type
  • 50124    Intubation ETT Secured Distance
  • 50125    Intubation ETT Secured Reference Point
  • 50209    LMA Placement Note
  • 50141    Airway - LMA Type
  • 50142    Airway - LMA Size
  • 50143    Airway - LMA Placement Difficulty
  • 50144    Airway - LMA Placement Technique

Halogenated Gases and Flows

  • 3214       Fresh Gas Flow Total (L/min)
  • 3225       Flows Nitrous Oxide (L/min)
  • 3220       Flows Air (L/min)
  • 3215       Flows Oxygen (L/min)
  • 3275       Sevoflurane Insp %
  • 3265       Isoflurane Insp %
  • 3285       Desflurane Insp %
  • 3250       Nitrous Insp %
  1. Sherman J, McGain F. Environmental sustainability in anesthesia: pollution prevention and patient safety. Adv Anesth. 2016;34:47-61.
  2. Feldman JM. Managing fresh gas flow to reduce environmental contamination. Anesth Analg. 2012;114:1093-1101.
  3. Eisenkraft JB, McGregor DG. Waste anesthetic gases and scavenging systems. In: Ehrenwerth J, Eisenkraft JB, Berry JM, eds. Anesthesia Equipment: Principles and Applications. 2nd ed. Philadelphia, PA: Saunders; 2013:139-145.
  4. Ek M, Tjus K. Destruction of Medical N O in Sweden, Greenhouse Gases - Capturing, Utilization and Reduction. Liu G, ed. InTech. 2012. Accessed March 1, 2017.
  5. Barwise JA, Lancaster LJ, Michaels D, et al. Technical communication: an initial evaluation of a novel anesthetic scavenging interface. Anesth Analg. 2011;113:1064-1067.
  6. American Society of Anesthesiologists’ Task Force on Environmental Sustainability Committee on Equipment and Facilities. Greening the operating room. Accessed March 1, 2017.
Measure Authors

 Measure Author


 Nirav Shah, MD

 University of Michigan

 Jodi Sherman, MD

 Yale School of Medicine

 Robert Lagasse, MD

 Yale School of Medicine

 Meridith Wade, MSN, RN

 University of Michigan

 Kate Buehler, MS, RN

 University of Michigan

 Rob Coleman

 University of Michgan

 MPOG Quality Committee



Measure Reviewer(s)
Next Review: 2025
 Date Reviewed  Reviewer  Institution  Summary  QC Vote






Published Date: 07/2019
 Date  Criteria  Revision
 09/01/2022  Multiple  Updated Measure Start to Intubation, then Induction End; Corrected Nitrous calculation
 07/27/2022  Provider  Exclude individual provider attribution
 04/20/2022  Success  Updated gas threshold values