Bohr effect [Christian Bohr, Danish physiologist, 1855–1911] , the effect of CO2 and H+ on the affinity of hemoglobin for molecular O2. Increasing PCO2 and H+ decreases oxyhemoglobin saturation, whereas decreasing concentrations have the opposite effect. In humans a decrease of pH from 7.4 to 7.3 at 40 mm Hg PO2 decreases oxyhemoglobin saturation by 6%. The Bohr effect is particularly significant in the capillaries of working muscles and the myocardium and in maternal and fetal exchange vessels of the placenta.
