Blood gas calculator.

SEVERINGHAUS, JOHN W. Blood gas calculator. J. Appl. Physiol. 21(3): I 108-1 I 16. 1966.-A slide rule is described whose scales yield direct solutions of the following blood gas problems: r) the whole blood oxygen dissociation curve of man with variable temperature, pH, and base excess; 2) the effect of anaerobic temperature change on blood Pea , Pcoz , and pH; 3) the true oxygen consumption fraction from mixed expired 02 and CO2 concentrations, breathing air; 4) correction of gas volume from ATPS to BTPS or STPD; 5) Henderson-Hasselbalch equation, relating pH, Pcoa , and either HC03 or CO2 content of plasma (range 10-40 C) or cerebrospinal fluid (20-40 C); 6) base excess and standard pH and bicarbonate (at Pcoz = 40 mm Hg) from pH and PCO~ at 37 C. The following modifications of standard blood gas relationships are described. The new oxygen dissociation curve deviates maximally from Dill’s curve by -4.5 and + I .5 % at I 4 and 60 mm Hg PO:! , respectively. Temperature shifts the dissociation curve by A log PO:! 0.024 AT C (formerly about 0.019). The “Bohr shift” with l;ctic acid is about 20% less than with CO2 , the combined effect being given by A log POT = -0.48 A pH + .oo13 A base. The correction factors for anaerobic temperature change diminish for PO:! at high saturation and for pH in acidosis.