Calculation of bidirectional shunts

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Calculation of bidirectional shunt in cathlab

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Calculation of bidirectional shunts

  1. 1. Calculation of Bidirectional Shunts Cross road both for examinee and examiner
  2. 2. Shunt Run • “Shunt Run” is performed if a difference of 8% or more is noted in blood sampling between chambers
  3. 3. Smaller physical, biggest physiological
  4. 4. Flamm’s
  5. 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 _____________________________________ 4
  6. 6. Dissolved O2
  7. 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. 8. Fick’s
  9. 9. Puzzles of 6 • MVO2 • PAO2 • PVO2 • SAO2 • QP • QS
  10. 10. Pulmonary Blood Flow
  11. 11. Systemic Blood flow
  12. 12. Qeff
  13. 13. In the Absence of Shunt in series •PBF=SBF=EBF
  14. 14. Left-to-right shunt • The approximate left-to-right shunt then = Q p - Q eff
  15. 15. Left to Right shunt
  16. 16. Left to right shunt
  17. 17. Effective Blood Flow • Fraction of Mixed Venous blood received by the lungs without contamination from shunt(from left to right)
  18. 18. Right-to-left shunt • the approximate right-to-left shunt equals Q s- Q eff
  19. 19. Right to left shunt
  20. 20. Just understand ,do not mug it up

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