Oxygen delivery: Factors impacting
Last updated: 03/04/2015
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.]
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