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Assuming someone has a normal heart, normal coronaries... We know:
Oxygen Delivery:
Arterial DaO2= Q x CaO2 x 10 [N=1000 mL/min]
Venous DvO2= Q x CvO2 x 10 [N=775 mL/min]
Given:
Oxygen carrying capacity
CaO2 = (hgb x SaO2 x 1.38) + (PaO2x0.003) [N=20 mL/dL]
CvO2 = (hgb x SvO2 x 1.38) + (PaO2x0.003) [N=15 mL/dL]
Oxygen Delivery:
VO2 = DaO2-DvO2
Reducing Equation:
VO2 = Q x (SaO2-SvO2) x Hgb x 13.8 [N=200-250 mL/min]
Extraction Ratio:
(CaO2-CvO2)/CaO2 x 100 (N=25%)
So.... VO2 = Q x (SaO2-SvO2) x Hgb x 13.8
My question is this, utilizing maximum oxygen extraction (I believe 50%)... At what level can the heart increase the cardiac output (Q) before oxygen delivery needs to be increased?
Stated another way, at what point can your Q increase to make up for decreased Hgb until oxygen delivery becomes dependent on hgb?
Oxygen Delivery:
Arterial DaO2= Q x CaO2 x 10 [N=1000 mL/min]
Venous DvO2= Q x CvO2 x 10 [N=775 mL/min]
Given:
Oxygen carrying capacity
CaO2 = (hgb x SaO2 x 1.38) + (PaO2x0.003) [N=20 mL/dL]
CvO2 = (hgb x SvO2 x 1.38) + (PaO2x0.003) [N=15 mL/dL]
Oxygen Delivery:
VO2 = DaO2-DvO2
Reducing Equation:
VO2 = Q x (SaO2-SvO2) x Hgb x 13.8 [N=200-250 mL/min]
Extraction Ratio:
(CaO2-CvO2)/CaO2 x 100 (N=25%)
So.... VO2 = Q x (SaO2-SvO2) x Hgb x 13.8
My question is this, utilizing maximum oxygen extraction (I believe 50%)... At what level can the heart increase the cardiac output (Q) before oxygen delivery needs to be increased?
Stated another way, at what point can your Q increase to make up for decreased Hgb until oxygen delivery becomes dependent on hgb?