Oxyhemoglobin dissociation curve
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An oxyhemoglobin dissociation curve is a sigmoid plot of percent oxyhemoglobin saturation against the partial pressure of O2. The curve illustrates hemoglobin's affinity for oxygen.
Under normal resting conditions in a healthy individual, the normal position of the curve is at a pH of 7.4.
A shift in the position of the curve with a change in pH is called the Bohr effect.
The 'plateau' portion of the oxyhemoglobin dissociation curve is the range that exists at the pulmonary capillaries (minimal reduction of oxygen transported until the p(O2) falls below 60 mmHg). The 'steep' portion of the oxyhemoglobin dissociation curve is the range that exists at the systemic capillaries (a small drop in systemic capillary p(O2) can result in the release of large amounts of oxygen for the metabolically active cells)
When the curve shifts to the right (representing a decrease in affinity for O2) - acute acidosis, increase in p(CO2), increase in temperature, and increase in 2,3-diphosphoglycerate (DPG) When the curve shifts to the left (representing an increase in affinity for O2) - acute alkalosis, decrease in p(CO2), decrease in temperature, and decrease in 2,3-diphosphoglycerate (DPG)
Carbon monoxide has a much higher affinity for hemoglobin than oxygen does. In carbon monoxide poisoning, oxygen cannot be transported and released to body tissues thus resulting in hypoxia.
The oxygen dissociation curve for fetal hemoglobin is to the left of that of adult hemoglobin, in order to facilitate diffusion of oxygen across the placenta. The oxygen dissociation curve for myoglobin exists even further to the left.