Determination of carbon monoxide in blood.

Methods suggested for the determination of carbon monoxide in blood may be considered as belonging to either of these two classes: first, those in which the relative content of carbon monoxide in blood is measured; second, those in which the absolute quantity of carbon monoxide per given quantity of blood is determined. In the first class, the result is expressed as the percentage saturation of hemoglobin with carbon monoxide. Usually a few drops of blood suffice for a determination. The principal methods belonging to this class are: (a) Haldane’s carmine method (l), whereby the carbon monoxide content is determined from the color of the greatly diluted blood solution, which is more or less pink, depending on the percentage saturation of the hemoglobin with carbon monoxide. This method is not very exact, its results being largely dependent upon subjective causes. (b) Sayers and Yant’s pyrotannic acid method (2). This is based on the fact that after the addition of tannic acid to normal diluted blood a gray color is produced, whereas under the same conditions, blood containing carbon monoxide remains more or less red. The percentage saturation is found by comparison with a color scale. This method is open to the same criticisms as Haldane’s carmine method. (c) Spectroscopic determination. Here the percentage saturation of hemoglobin with carbon monoxide is found by the amount of displacement of the absorption bands of the blood, which are displaced more towards the violet end of the scale, depending upon the amount of carbon monoxide present. Hartridge’s reversion spectroscope (3) is well suited to this method, but is very expensive. In the methods belonging to the second class, the result is