Canadian Anaesthetists’ Society Journal

, Volume 26, Issue 4, pp 313–318 | Cite as

Nitrous oxide levels in operating room air with various gas flows

  • Robert W. Virtue
  • Alfonso Escobar
  • Jack Modell


Monitoring of nitrous oxide concentrations in operating rooms disclosed some leaks that had hitherto been unrecognized. Because nitrous oxide concentrations reported before 1967 had been obtained for the most part with high flows of the gas and without information concerning room air exchange, measurements were made of nitrous oxide levels during operations with an infra-red analyzer, after correction of leaks. Measurements were made at six sites in the operating-room suite, with and without scavenging. Flows that varied from 0.1 to 2.5 litres of nitrous oxide were used in rooms that had 20 changes per hour of fresh air. Without scavenging, the highest time-weighted average value inhaled by any of the personnel (anaesthetists) was 31 ppm, when flow of 500 ml of nitrous oxide per minute were employed. The lowest reported deleterious concentration (unconfirmed) is 50 ppm. Lower flows produced lower values. With good scavenging, using flows as high as 2.5 1/min of nitrous oxide, the highest average value (anaesthetist) was 7.2 ppm. A short discussion is given concerning reasons for using low flows, including the cost of wasting agents and pollution of the entire atmosphere.


Operating Room Nitrous Oxide Halothane Tracheal Tube Relief Valve 


La mesure des concentrations de protoxyde ďazote dans ľathmosphère de nos salles ďopération a permis de mettre en évidence des fuites de gaz insoupçonnées au niveau de nos appareils ďanesthésie. Les concentrations de protoxyde rapportées avant 1967 provenaient pour la plupart de mesures effectuées alors que ľon utilisait de hauts débits gazeux et ces résultats étaient rapportés sans faire mention de la ventilation des salles ďopération.

Nous avons effectué des mesures de concentration de cet agent à six endroits de nos salles ďopération au moyen ďun analyseur à ľinfrarouge et ce, après correction des fuites décelées au niveau de nos appareils ďanesthésie et de leurs raccords. Les débits de protoxyde utilisés s'échelonnaient de 0.1 à 2.5 l/min. dans des salles oò le système de ventilation fournissait 20 changements ďair à ľheure. Les mesures ont été effectuées avec ou sans vidange des gaz anesthésiques.

Sans système de vidange, les valeurs les plus élevées (31 p.p.m.) observées ľont été près de ľanesthésiste lorsque ľon utilisait des débits de gaz de 500 ml/min. On sait que les effets nuisibles (non confirmés) commenceraient à des taux de 50 p.p.m. Avec un bon système de vidange des gaz et avec des débits de 2.5 l/min., les valeurs maximales observées (près de ľanesthésiste) étaient de 7.2 p.p.m.

En terminant, les auteurs discutent des avantages de ľemploi de petits débits gazeux, tant du point de vue du coôt des agents anesthésiques que du point de vue de pollution de ľathmosphère des salles ďopération.


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Copyright information

© Canadian Anesthesiologists 1979

Authors and Affiliations

  • Robert W. Virtue
    • 1
  • Alfonso Escobar
    • 1
  • Jack Modell
    • 1
  1. 1.Department of AnesthesiologyUniversity of Colorado Medical CenterDenver

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