Carbon Dioxide Tolerance and Toxicity

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Title: Carbon Dioxide Tolerance and Toxicity
Author: Lambertsen, CJ
Abstract: Carbon Dioxide is a normal body constituent, continually produced by oxidative metabolism. Its hydration leads to formation of hydrogen ions and the establishment of a bicarbonate buffer system in blood and other vital body fluuids. In its numerous normal roles in body function carbon dioxide is a key chemical messenger substance in the linking of respiration, general circulation and local vascular responce to the demands of metabolism both at rest and exercise. In its normal, active role as an agent in the respiratory, circulatory and renal control systems, intrinsically produced carbon dioxide is not a toxin. It is an essential factor in the determination of the normal acid-base balance required for enzymatic reactions. Inhaled carbon dioxide produces the same physiological effects as does carbon dioxide produced metabolically. These effects appear to result from the acidosis induced by carbon dioxide reaction with water, rather than by the CO2 molecule itself. Toxic effects of CO2 do occur when such high concentrations of CO2 are inhaled that severe and disruptive cellular acidosis occurs. This acidosis and its effects are alleviated by lowering the inhaled concentration of CO2. Adaptation to moderate inspired concentrations of carbon dioxide (to three and four percent) occurs in normal men who can tolerate continuous inhalation of three percent inspired CO2 for at least one month and four percent inspired CO2 for over a week. Because the effects produced by low and moderate concentrations of carbon dioxide are physiological and reversible, rather than toxic and damaging, it is recommended that the allowable inspired levels of carbon dioxide be increased from 0.5 to 2.0 percent in inspired air. This level has not been shown too induce decrement in performance or in normal physical activity.
Description: Citation Status: Active; Citation Classification: Unclassified; Title Classification: Unclassified; Report Classification: Unclassified; Identifier Classification: Unclassified; Abstract Classification: Unclassified; Distribution Limitation(s): 01 - APPROVED FOR PUBLIC RELEASE; Information provided by the Department of Defense and the Defense Technical Information Center ( is considered public information and may be distributed or copied unless otherwise specified. Use of appropriate byline/photo/image credits is requested.
Date: 1971

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