Oxyhemoglobin Dissociation Curve
The content of this page is intended to familiarize the reader with the very basic understanding of oxygen hemoglobin dissociation curve and discuss the major factors involved. The curve is of sigmoidal shape and relates oxygen content to the partial pressure of oxygen in the blood. Percent of oxygen saturation is on the y-axis, and pO2 pressure is on the x-axis, expressed in mmHg.
Bohr Effect
Bohr Effect plays an important role in oxygen-hemoglobin dissociation curve. Carbon Dioxide diffuses into alveoli when the blood passes through the lungs, this results in a decrease in the blood pCO2 and also decreases hydrogen ion concentration (due to the decrease in blood carbonic acid). This shifts the dissociation curve to the left. The amount of oxygen that binds with hemoglobin at any given alveolar PO2 increases and provides for greater O2 transport to the tissues. When the blood reaches tissue capillaries, CO2 enters the blood and shifts the curve to the right, thus displacing oxygen from hemoglobin and oxygen delivery occurs at a higher PO2.Oxygenation
The primary purpose of extracorporeal circuit is to perfuse vital organs and maintain oxygen transport. Oxygenation is influenced by the cellular supply and demand as well as the cell's ability to effectively extract and utilize the oxygen. The oxygenation is influenced by such factors as intracellular pH, temperature, 2,3-diphosphoglutamate (2,3-DPG), and carbon dioxide.2,3-DPG
2,3-diphosphoglycerate (2,3-DPG) is a phosphate compound normally present in blood in different concentrations under different conditions.p50
The position of the oxyhemoglobin curve is best described by the pO2 tension at which hemoglobin is 50% saturated. The normal value for p50 is 26.7 mm Hg.
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Right and Left shifts
p50 value of greater than 27 mm Hg describes a right shift in the curve, meaning that hemoglobin has a lower affinity for oxygen and therefore it is less saturated. p50 value lower than 27 mm Hg indicated a leftward shift in the curve meaning that hemoglobin has a higher affinity for oxygen and thus it is more highly saturated.Major factors involved
pH --> increase results in shift to the left.decrease results in shift to the right.
Temperature --> increase results in shift to the right.
decrease results in shift to the left.
pCO2 --> increase results in shift to the right.
decrease results in shift to the left.
2,3-DPG --> increase results in shift to the right.
decrease results in shift to the left.
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