Published on March 21, 2014
Calculation of Bidirectional Shunts Cross road both for examinee and examiner
Shunt Run • “Shunt Run” is performed if a difference of 8% or more is noted in blood sampling between chambers
Smaller physical, biggest physiological
Flamm’s MVO2 • Average Oxygen Content in Chambers proximal to the Shunt • Method to calculate Mixed Venous Oxygen content • Need to factor in Contribution from IVC and SVC which is not equal • Flamm Equation: 3xSVC Oxygen Content + IVC Oxygen Content _____________________________________ 4
Fick Equation to Calculate Oxygen Content • Assumes in steady state that… that rate of substance entering (C in x Qflow) is equal to the rate of substance leaving (C out x Qflow) + the rate at which indicator, V, is added. Flow= Oxygen consumption/Arterial- Venous oxygen content difference • Where oxygen content is determined by automated methods • oxygen consumption is assumed based on patient’s age, gender and body surface area when not directly measured
Puzzles of 6 • MVO2 • PAO2 • PVO2 • SAO2 • QP • QS
Pulmonary Blood Flow
Systemic Blood flow
In the Absence of Shunt in series •PBF=SBF=EBF
Left-to-right shunt • The approximate left-to-right shunt then = Q p - Q eff
Left to Right shunt
Left to right shunt
Effective Blood Flow • Fraction of Mixed Venous blood received by the lungs without contamination from shunt(from left to right)
Right-to-left shunt • the approximate right-to-left shunt equals Q s- Q eff
Right to left shunt
Just understand ,do not mug it up
Calcification Inhibitors in CKD and Dialysis Patients
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