Calculation of bidirectional shunt in cathlab

1. Calculation of
Bidirectional Shunts
Cross road both for examinee and examiner

2. Shunt Run
• “Shunt Run” is performed if a difference of 8% or more is noted in blood
sampling between chambers

3. Smaller physical, biggest physiological

4. Flamm’s

5. 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
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4

6. Dissolved O2

7. 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

8. Fick’s

10. Puzzles of 6
• MVO2
• PAO2
• PVO2
• SAO2
• QP
• QS

11. Pulmonary Blood Flow

12. Systemic Blood flow

13. Qeff

14. In the Absence of Shunt in series
•PBF=SBF=EBF

15. Left-to-right shunt
• The approximate left-to-right shunt then = Q p - Q eff

17. Left to Right shunt

18. Left to right shunt

19. Effective Blood Flow
• Fraction of Mixed Venous blood received by the lungs without contamination
from shunt(from left to right)

20. Right-to-left shunt
• the approximate right-to-left shunt equals Q s- Q eff

21. Right to left shunt

22. Just understand ,do not mug it up