A program for calculation of intrapulmonary shunts, blood gas and acid base values with a programmable calculator

Abstract

With a desk top, programmable calculator, it is now possible to do complex, previously time consuming computations in the blood gas laboratory. The authors have developed a program with the necessary algorithms for temperature correction of blood gases and calculation of acid base variables and intrapulmonary shunt. It was necessary to develop formulas for the P(O2) temperature correction coefficient, the oxyhemoglobin dissociation curve for adults (with necessary adjustments for fetal blood), and changes in water vapor pressure due to variation in body temperature. Using this program in conjunction with a Monroe 1860-21 statistical programmable calculator, it is possible to temperature correct pH, P(CO2), and P(O2). The machine will compute alveolar arterial oxygen tension gradient, oxygen saturation [S(O2)], oxygen content [C(O2)], actual HCO3- and a modified base excess. If arterial blood and mixed venous blood are obtained, the calculator will print out intrapulmonary shunt data [Q(s)/Q(t)] and arteriovenous oxygen differences (a - vD(O2)). There also is a formula to compute P50 if pH, P(CO2), P(O2), and measured S(O2) from 2 samples of tonometered blood (one above 50% and one below 50% saturation) are put into the calculator.