Oxygen affinity of human blood in presence of carbon monoxide.

If carbon monoxide is present in the blood, it is necessary to quantitate its effect on apparent O2 affinity in order to properly compute venous PO2 and P50. Ways of doing this are analyzed theoretically. The classical principles of Haldane and of Roughton and Darling are reviewed and simplified. The method of computation of PO2 in the presence of CO as introduced by Forster is shown to be in considerable error. The source of this error is determined. The error produced if the presence of CO is ignored during the computation of P50 is analyzed.