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. Author manuscript; available in PMC: 2015 May 4.
Published in final edited form as: Trends Biotechnol. 2014 Mar 12;32(4):177–185. doi: 10.1016/j.tibtech.2014.02.006

Figure I. Box 1. Gas exchange and performance of oxygen carriers.

Figure I

A) Gas exchange and transport by hemoglobin. Oxygen is carried from the lungs to the tissues by Hb, and CO2 is carried back to the lungs. Part of CO2 (∼20%) is carried on the amino termini of Hb as carbamino compounds (R-NH-COO− + H+). The major mechanism for the transport of CO2 to the lungs is carried out in the plasma, i.e in the plasma as HCO3− (∼80%). This reaction is catalyzed by the enzyme carbonic anhydrase (CA). DeoxyHb picks up those protons and aids in the formation of bicarbonate ions from CO2 in the blood plasma. B) Oxygen equilibrium curves for some commonly used HBOCs compared with that of free hemoglobin and fresh red blood cells. OECs for several HBOCs compared with that of fresh RBCs (dotted red line) (P50 = 29-30 mmHg) and an isolated purified Hb (HbA0) (red line) (P50 = 8-12 mmHg). Some maintained their classical sigmoidal shape, whereas others lack such an important property, and are either left or right shifted and some curves do not reach the saturation levels at higher oxygen tension (i.e PO2 =100 mmHg) (see for example OECs of Hemolink and oxyglobin, an FDA approved HBOC for use in Veterinary Medicine).