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Effect of inspired nitrous oxide concentration on the rate of fall of alveolar concentration: reversed concentration effect
Author(s) -
MASUDA T.,
IKEDA K.
Publication year - 1986
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1986.tb02389.x
Subject(s) - nitrous oxide , medicine , anesthesia , oxide , zoology , respiratory system , minimum alveolar concentration , nitric oxide , nitrogen , chemistry , anesthetic , organic chemistry , biology
The effect of inspired nitrous oxide concentration on the rate of fall of alveolar nitrous oxide concentration was studied in six patients ranging in age from 25 to 46 years. After equilibrium was reached with nitrous oxide, nitrous oxide administration was stopped and replaced by the same concentration of nitrogen. The decrease in alveolar concentration of nitrous oxide (FE/FE o ) was measured continuously, where FE = measured end‐tidal concentration of nitrous oxide, and FE o = the end‐tidal concentration immediately preceding the cessation of nitrous oxide administration. The rate of decrease in FE/FE o was more rapid when 70% nitrous oxide was inspired (Part I) than when 30% nitrous oxide was inspired (Part II). One minute after the cessation of nitrous oxide administration, FE/FE o was 0.30 0.03 (mean s. d.) in Part I and 0.36 0.02 in Part II ( P <0.05). Mean expired tidal volume increased from 515 43 ml to 552 48 ml in Part I and from 510 48 ml to 526 39 ml in Part II ( P <0.05). The authers conclude that the more rapid decrease in alveolar concentration of nitrous oxide (FE/FE o ) at higher concentrations of nitrous oxide results from augmentation of expired ventilation. We have called this phenomenon the “reversed concentration effect”.