A study on the development of the 6 inert gas elimination method for VA/Q distribution measurement during inhalational anesthesia
Ueno, O.; Ueyama, H.
Masui. Japanese Journal of Anesthesiology 36(1): 46-52
1987
ISSN/ISBN: 0021-4892 PMID: 3560426 Document Number: 290522
Ventilation-perfusion ratio (.ovrhdot.VA/.ovrhdot.Q) distribution during N2O-halothane anesthesia was investigated using 6 inert gas elimination method. In order to apply 6 inert gas elimination method for the cases during N2O-halothane anesthesia, original method should be improved by changing one of inert gases, halothane, to enflurane which has almost the same gas solubility in blood as halothane and anesthesia circuit should be changed to collect pure expired gas. For these purposes, changing FID Gaschromatograph from SHIMAZU GC-4C to GC-9A, column packing materials from PORAPAC-T to PORAPAC-QS in FID and to PORAPAC-Q in ECD and using an Oxford Ventilator in anesthesia circuit, we have succeeded to separate enflurane peak from halothane peak, ethane peak from N2O peak and to separate SF6 peak from N2O, halothane peaks. Almost linear relationship between peak heights and concentrations of inert gases were obtained and measurement errors were below 4.4% in SF6 and below 3.0% in other 6 inert gases. Using improved 6 inert gas elimination method, on 11 patients under N2O-halothane anesthesia, .ovrhdot.VA/.ovrhdot.Q distribution was measured during anesthesia and it was concluded that increase in intrapulmonary shunt and development of low .ovrhdot.VA/.ovrhdot.Q contributed to development of hypoxemia during N2O-halothane anesthesia.