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Correspondence  |   April 2003
Effect of Nitrous Oxide on Sevoflurane Vaporizer Setting: In Reply:
Author Affiliations & Notes
  • Andre M. De Wolf, M.D.
    *
  • *Northwestern University Medical School, Chicago, Illinois.
Article Information
Correspondence
Correspondence   |   April 2003
Effect of Nitrous Oxide on Sevoflurane Vaporizer Setting: In Reply:
Anesthesiology 4 2003, Vol.98, 1029. doi:
Anesthesiology 4 2003, Vol.98, 1029. doi:
In Reply:—
We appreciate the comments made by Dr. Lin. He correctly points out that the anesthesia circuit and the patient's functional residual capacity can be considered to be a reservoir of vapor (in this study, sevoflurane). However, because the desired end-expired sevoflurane concentration was obtained within 5 min in all groups, and because the sevoflurane concentration was kept constant throughout the study period (10–60 min), the anesthesia circuit and functional residual capacity are not a “source” of sevoflurane thereafter nor do they contribute to sevoflurane consumption during the observation period. In other words, the anesthesia circuit and the patient's functional residual capacity, once saturated at the desired sevoflurane concentration, do not affect the vaporizer setting required to keep end-expired sevoflurane concentration constant. This concept is not influenced by the initial fresh gas flow settings.