oxygen delivery in mL/min =
= (cardiac output) * (arterial oxygen content)
oxygen delivery index in mL oxygen per minute per meter square =
= (cardiac index) * (arterial oxygen content) * 10
oxygen consumption =
= (cardiac output) * (difference in arterial and mixed venous blood oxygen content)
oxygen extraction ratio =
= (oxygen consumption) / (oxygen delivery) =
= ((difference in arterial and mixed venous blood oxygen content) / (arterial oxygen content)
Interpretation:
• normal oxygen delivery: 1000 mL/min
• normal oxygen consumption: 200-250 mL/min
• normal oxygen extraction ratio: 22-32%
• increased oxygen affinity of hemoglobin will decrease the oxygen extraction ratio; decreased oxygen affinity of hemoglobin will increase the oxygen extraction ratio
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Decreased Oxygen Affinity
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Increased Oxygen Affinity
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pH
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decreased
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increased
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|
pCO2
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increased
|
decreased
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|
temperature
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increased
|
decreased
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erythrocyte 2,3-diphosphoglycerate (2,3-DPG)
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increased
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decreased
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abnormal hemoglobins
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some
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some
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other
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methemoglobin
hemoglobin-CO
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