Derives the correlation between the arterial blood composition and the acid-base status of the whole body subjected to simultaneous respiratory and metabolic changes. To improve diagnosis and therapy, the biochemical status of a patient is often predicted from commonly measured parameters of a sample of blood in vitro. This method gives a rough index of the body status. This Memorandum constructs a nomogram for more exactly estimating whole body base excess from the pH and the partial pressure of carbon dioxide of arterial blood in vitro. It is based on experimental data obtained from 54 nephrectomized dogs subjected to hyperventilation, carbon dioxide breathing, and infusion of acid and base. The experimental results validated a mathematical, computer-based model of whole body fluid and electrolyte distribution. Because of the similarity between the acid-base responses of dog and man, the model should permit more accurate determination of human whole body base excess from a blood specimen.