Cyanosis.

"In their monumental 1945 paper on the surgical treatment of malformations of the heart, Alfred Blalock and Helen Taussig refer to this monograph: 'Lundsgaard and Van Slyke in their classic studies on the causes of cyanosis showed that there were four important factors in the production of cyansosis: the height of the hemoglobin, the volume of the venous blood shunted into the systemic circulation, the rate of utilization of oxygen by the peripheral tissues and the extent of the aeration of the blood in the lungs' " (W. Bruce Fye).