Some years ago I published a description1 of an arrangement of valves for use especially in administering volatile anesthetics to animals in laboratory experimentation. The apparatus was designed primarily to avoid unnecessary waste of volatile anesthetics. An experiment with the first model constructed, in which an 8-kilo dog was employed, showed a saving of almost exactly one-half in ether when the valves were used, as compared to the amount used with the animal directly connected with the anesthetic bottle in the ordinary manner. This saving is due to the action of the valves in preventing air being forced through the bottle during expiration, thus displacing and carrying away ether vapor. And since expired air is warmer than inspired air under usual laboratory conditions, the increased vaporization due to raising the temperature of the liquid anesthetic is avoided. Furthermore, contamination of the anesthetic by condensation of water vapor is avoided. The
GUTHRIE CC. RESPIRATION VALVES. JAMA. 1911;LVII(11):887–888. doi:10.1001/jama.1911.04260090109013
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