Dissociation curves of carbon monoxide-hemoglobin in the presence of air (20.9% O2) at a temperature of 38 degrees C

Although the curve for each individual is a rectangular hyperbola, the percentage saturation with a given percentage of carbon monoxide varies for different individuals and across species. However, the dissociation curves are not affected by varying the pressure of CO2. The percentage of carbon monoxide required to produce half-saturation in presence of air is about 15% less for the blood of JS Haldane (I) than for that of CG Douglas (II). The dissociation curve of carboxy-hemoglobin for the blood of JSHaldane is about 15% to the left of that of CG Douglas, indicating that the affinity for carbon monoxide of the blood of JS Haldane is about a sixth greater than in the case of the blood of CG Douglas. The affinity of carbon monoxide for hemoglobin is 246 times as great as that of oxygen for hemoglobin in the blood of CG Douglas. Key: I, blood of John S Haldane (Sr.); II, blood of CG Douglas; III, Blood of mouse A; IV. blood of mouse B. The crosses indicate points determined in the presence of 40 mm pressure of added CO2. (Source: Douglas CG, Haldane JS, Haldane JB. The laws of combination of haemoglobin with carbon monoxide and oxygen. J Physiol 1912;44(4):275-304.)