In the closed system of administering anesthesia, the patient is required to breathe into the machine and to inhale, unless modifications of the gaseous mixture are brought about, what he has previously exhaled. During respiration, the air is changed in three ways that might prompt one to modify the mixture before rebreathing: the oxygen content is reduced, the carbon dioxide concentration is elevated, and the amount of water is increased. There is no difference in the absolute amounts of nitrogen or argon inhaled and exhaled. A fourth and entirely physical change is the increase in the temperature of the air, resulting from air being drawn into the lungs and from gas, particularly carbon dioxide, being removed from the blood. Gases are exhaled at approximately body temperature. In order to counteract the first two changes, oxygen is added to maintain a constant level and contact with soda lime is employed to
Cole F. WATER ACCUMULATION AS A HAZARD OF REBREATHING IN ANESTHESIA. JAMA. 1953;151(11):910–913. doi:10.1001/jama.1953.02940110032008a
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