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Oxygen delivery: Factors impacting

Delivery of oxygen can be calculated with the equation:

DO2 = CO x CaO2

Where CaO2 = [1.34 x Hgb x SaO2] + [PaO2 x 0.003]

The portion contributed by dissolved O2 [PaO2 x 0.003] is usually negligible except in cases of extreme anemia (i.e. Hgb 5) or carbon monoxide poisoning.

Factors that affect the oxyhemoglobin dissociation curve will also affect oxygen delivery:

Normal p50 is 27mmHg

Left shifts (Hgb holds onto O2 more):

carbon monoxide, methemoglobin, hypophosphatemia (i.e. critical care patients), HbF

Right shifts (Hgb unloads more O2):

CADET right face!

CO2 [Bohr effect: hypercarbia causes drop in pH, decreases affinity for oxygen (right shift) at tissues and facilitates unloading of O2.]