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November 1984

Bicarbonate or CO2?

Author Affiliations

Newcastle Upon T[ill]ne, England

Arch Intern Med. 1984;144(11):2285-2287. doi:10.1001/archinte.1984.04400020219047

To the Editor.—In their editorial in the November 1983 Archives, Garfinkel and Gelfman1 stated that there is "widespread" uncertainty about what total CO2 content actually is" and that "CO2 (from total CO2 content)... is often confused in the clinician's mind with Pco2." They submit that using the terms bicarbonate concentration or bicarbonate instead would avoid this confusion and simplify understanding of acid base metabolism. We disagree. We believe that to do so would only further obscure the confusion already inherent in current clinical biochemical practices.

It is current teaching that change in pH results from alteration of the ratio, in circulating plasma, between concentrations of bicarbonate ions ([Hco3]p) and of dissolved CO2 molecules plus carbonic acid.2 This interrelationship is presented in the Henderson-Hassel-balch equation,

Where Pco2 is the partial pressure of CO2 with which plasma is in equilibrium, s is the solubility factor for plasma and

pH, Pco2

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