An oxyhemoglobin dissociation curve is a sigmoid plot of percent oxyhemoglobin saturation vs. P_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 = range that exists at the pulmonary capillaries (minimal reduction of oxygen transported until the P02 falls below 60 mmHg) The Steep portion of the oxyhemoglobin dissociation curve = range that exists at the systemic capillaries (a small drop in systemic capillary PO2 can result in the release of large amounts of xygen for the metabolically active cells)

When the curve shifts to the right (decrease in O2 affinity) - acute acidosis, increase in PCO2, increase in temperature, and increase in 2,3 diphosphoglycerate (DPG) When the curve shifts to the left (incrsae in O2 affinity) - acute alkalosis, decrase in PCO2, 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.