The copper kettle: a historical perspective

Until 1952, the administration of inhaled volatile anesthetics was inexact because vaporizers in general use were not calibrated for either concentration or volume of vapor produced. These devices diverted a variable portion of fresh gas flow either through or over the liquid to be vaporized, but they lacked vernier or fine control. Therefore, changes in the concentration of the anesthetic vapor were not easily controlled. Dr. Lucien E. Morris standardized the administration of volatile anesthetics with his invention of the Copper Kettle, which produced known volumes of saturated vapor, then diluted to calculated concentrations necessary for anesthesia. To achieve this, modifications had to be made in the liquid container, circuit design, and vaporizing surfaces in use at the time. Morris' design incorporated a separately metered flow of carrier gas through the vaporizer to produce known volumes of saturated vapor for introduction into the fresh gas flow delivery.