RELATIONSHIP BETWEEN WHOLE-BLOOD BASE EXCESS AND CO2 CONTENT IN-VIVO

Empirical relationships are demonstrated for whole blood base excess ( BE) and CO2 content (C(CO2)), both calculated from in vivo measurement s of P(CO2), pH, hemoglobin concentration and O2 saturation. Compariso ns are provided by measurements from three separate studies: (1) supin e exercise (arterial and mixed venous samples); (2) chronic obstructiv e disease patients (arterial samples) breathing air and 100% O2; and ( 3) maximal seated exercise on a bicycle ergometer with and without add ed inspired CO2 (arterial samples before, during and after). Two stand ardized values of C(CO2) (vol.%) are derived which closely relate to B E (mmol/l). The C(CO2) at a P(CO2) of 40 mmHg [C(CO2)(40)] for all sam ples (n = 220) demonstrated a curvilinear relationship: C(CO2),(40) = 45.37 + 1.48(BE) + 0.0156(BE)2, r = + 0.996, SEE = 0.88 vol.%. The C(C O2) at a pH of 7.4 [C(CO2)(7.4)] gave a linear relationship: C(CO2)(7. 4) = 45.09 + 2.58(BE), r = + 0.998, SEE = 1.19 vol.%. Empirical comput ations for the Haldane factor from studies 1 and 2 gave values of 0.28 5 in terms of C(CO2) (vol.%/vol.%) and 0.266 for BE (mmol/1/mmol reduc ed Hb). The BE values can serve as useful estimates of lactate concent rations during exercise and the excellent relationships between standa rdized C(CO2) and BE demonstrate their equivalency and either can be u tilized, depending on whether quantification of the CO2 dissociation c urve or acid-base status is desired.