Validation of a dynamic evaporation technique for generating isoflurane/air gas mixtures standards to calibrate anesthetic gas monitors.

The dynamic evaporation and mixing technique standardized in EN 1839 (method T), originally developed to determine the flammability limits of chemical vapors, was applied to prepare isoflurane-in-air calibration gas mixtures, with air serving as the carrier gas. Isoflurane concentrations spanning 0 to 8 vol% were generated on demand by independently controlling the liquid isoflurane and air flow rates. Verification using an anesthetic gas monitor demonstrated excellent agreement between predicted and measured concentrations. A comprehensive validation study was conducted in accordance with EURACHEM guidelines, encompassing linearity, limit of detection (LOD), limit of quantification (LOQ), precision, robustness, and measurement uncertainty. The method yielded a correlation coefficient of r² = 0.9998 over the full clinical range, an LOD of 0.08 vol%, and an LOQ of 0.27 vol%. All concentrations between 0.70 and 8 vol% complied with EN 1839 uncertainty requirements, confirming the suitability of this approach for routine calibration of isoflurane gas monitors.