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IVC Collapse Physiology knowing the caveats & evidence

Delve into the Vena Cava pressure-volume relationship, Trans-mural pressure, and specificity of IVC collapse for volume responsiveness. Discover insights on Doppler theory for intensivists. Learn about the implications of Velocity Error in Doppler equations and how to improve specificity and sensitivity for volume determination.

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IVC Collapse Physiology knowing the caveats & evidence

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  1. IVC Collapse Physiologyknowing the caveats & evidence Jon-Emile S. Kenny MD Senior contributor pulmccm.org Author of ICU Physiology in 1000 Word Series Creator heart-lung.org Cofounder & Chief Medical Officer of Flosonics Medical Twitter handle @heart_lung

  2. Conflicts of Interest Chief Medical Officer and Co-founder of Flosonics Medical in Toronto, Canada

  3. The IVC acts as an un-stressed chamber Huh?

  4. Vena cava pressure-volume relationship IVC volume Spontaneous breathing without assistance Trans-mural pressure [CVP – PAB]

  5. Toronto Doppler Monster RUQ Transverse plane 01/27/2015 MR: 29205

  6. Vena cava pressure-volume relationship IVC volume Trans-mural pressure [CVP – PAB]

  7. Volume or Flow Guyton What are some basic assumptions here? Venous return curve doesn’t change with inspiration & Starling physiology occurs at atmospheric pressure Cardiac function doesn’t change Change in pleural pressure is standardized Pmsf Ppl +5 PRA [mm Hg]

  8. Specificity What are some basic assumptions here? Volume or Flow Venous return curve doesn’t change with inspiration & Starling physiology occurs at atmospheric pressure Cardiac function doesn’t change Pcrit Clinical relevance? False positive = lower specificity Pmsf Ppl +5 PRA [mm Hg]

  9. 90 80 70 60 Specificity 50 40 30 20 10

  10. Sensitivity What are some basic assumptions here? Volume or Flow Change in pleural pressure is standardized Clinical relevance? False negative = lower sensitivity Pmsf Ppl +5 PRA [mm Hg]

  11. Based on the above, how could one improve specificity & sensitivity of IVC collapse for determining volume responsiveness? Exclude patients receiving ventilation assistance Ensure adequate inspiratory effort

  12. 90 80 70 60 50 40 30 20 10

  13. Thank you! www.heart-lung.org Stay hungry. Stay Foolish

  14. Advanced Doppler Theoryfor the intensivist Jon-Emile S. Kenny MD Senior contributor pulmccm.org Author of ICU Physiology in 1000 Word Series Creator heart-lung.org Cofounder & Chief Medical Officer of Flosonics Medical Twitter handle @heart_lung

  15. Conflicts of Interest Chief Medical Officer and Co-founder of Flosonics Medical in Toronto, Canada

  16. Background: Doppler & velocity

  17. Toronto Doppler Monster Suprasternal Notch 01/27/2015 MR: 29205 80 60 40 20 cm/s

  18. Doppler Equation

  19. So what? Velocity & Time At the Bedside

  20. So what? Velocity Time Integral = Distance

  21. Continuous Wave & Pulsed Wave

  22. Velocity Error: intrinsic aspects

  23. Geometric Spectral Broadening Ɵ Oh no! why?!

  24. Cosine Error Cosine Error

  25. Velocity Error: extrinsic aspects

  26. What is the assumption here? Velocity Time Integral = Distance

  27. Velocity Gradient Broadening w

  28. Accounting for Velocity Gradient Broadening

  29. Uniform Insonation

  30. Area

  31. 0 0

  32. In Review … Inherent variability at high angles of insonation Inherent variability with linear array transducers Velocity profiles pose sampling problems with PW Small errors in measurement leads to large error in flow Assumes constant circular shape Small errors in diameter may be due to inherent ultrasound characteristics

  33. Thank you! www.heart-lung.org Stay hungry. Stay Foolish

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