Cardiff Calculator for V.O.C. Fluothane
Date of manufacture:
This calculator disc was designed to predict the inhaled concentration of halothane in a circle absorption breathing system when the vaporiser was outside the circuit (Vaporiser Outside Circuit = V.O.C.) and the fresh gas flow is 'low'. It utilises the vaporiser concentration, fresh gas flow and ventilation. It assumes that the uptake of halothane by the patient is 15 ml/minute for each percent alveolar concentration. At this period in time, there were no readily available volatile agent analysers for routine clinical use. Consequently, with low flow circle absorption anaesthesia, there would be some risk of awareness. Many anaesthetists at the time therefore rarely lowered the fresh gas flow below 4 L/minute when using halothane in the V.O.C. mode.
This example has seriously damaged during a flood in the museum.
Brit. J. Anaesth, (1960), 32, 298 - 333.