Oxygen transport and oxyhemoglobin dissociation curve
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Definition
The oxyhemoglobin (Oxy-Hb) dissociation curve is a sigmoid plot relating PO2 in blood to percentage saturation of hemoglobin with oxygen, over a PO2 range of 0 to 100 mm Hg.
P50, the PO2 at which Hb is 50% saturated, is normally 27 mm Hg in adults at sea level.
Shape of the Curve
The curve is sigmoid (S-shaped) because Hb's affinity for oxygen varies with PO2, so saturation rises non-linearly as PO2 increases.
The sigmoid shape lets hemoglobin saturate with oxygen at the high PO2 of the lungs, and give up large amounts of oxygen for small PO2 changes at the tissues.
Phases of the Curve
Steep and plateau phases of the oxyhemoglobin dissociation curve