A New Acid-Base Nomogram Featuring Hydrogen Ion Concentration

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Abstract
A new acid-base nomogram has been devised which facilitates the visual representation of acid base parameters which acidity of the blood is expressed as free hydrogen ion concentration rather than as pH. Henderson''s original equation, which is a non-logarithmic equivalent of the Henderson Hasselbalch equation, expresses acidity directly as hydrogen ion concentration and has provided the mathematical basis for the nomogram. A Cartesian coordinate system has been used to provide a graphic solution to the Henderson equation in which hydrogen ion concentration is assigned to the ordinate and carbon dioxide tension to the abscissa. Bicarbonate concentration is depicted by straight iso-bars fanning out from the origin. Several fortuitous properties of this nomogram allow for an adequate free-hand version to be sketched from memory for use in bedside diagnosis and teaching.