Waters To-and-Fro

Brigham and Women's Hospital Department of Anesthesiology, Perioperative and Pain Medicine collection.

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Waters To-and-Fro CO₂ Absorber, circa 1930–1940s

Within anesthesia machines, vaporizers are used to mix anesthesia gases at specific concentrations and control their flow. Delivery of the anesthetic to the patient’s airway is the job of the “breathing system” which incorporates a mask or a tracheal tube. Several attempts were made to design a system that would prevent the exhalation of anesthetic into the ambient air or to prevent the patient from rebreathing their own carbon dioxide. Dr. Ralph Waters (1883–1979) introduced this simple device in 1923. Waters placed a carbon dioxide absorber, soda lime, in the canister between the gas inlet and the air reservoir bag. The patient was able to rebreathe anesthetic, “to-and-fro,” while the CO₂ was filtered out. This style of absorber gradually fell out of favor; the system became less efficient with passing time as the absorbent was exhausted and settled within the canister, but carbon dioxide absorption in one form or another became a standard function of all anesthesia machines.