Calculation of Bidirectional ShuntsCross 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

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

Dissolved O2

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

Fick’s

Puzzles of 6

• MVO2

• PAO2

• PVO2

• SAO2

• QP

• QS

Pulmonary Blood Flow

Systemic Blood flow

Qeff

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