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Factors Affecting Venous Return and Cardiac Output
- 1. Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 11
- 2. Cardiac out put IICardiac out put II Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 22
- 3. Venous ReturnVenous Return Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 33
- 4. Factors affecting venous returnFactors affecting venous return Right Atrial pressureRight Atrial pressure – Higher pressure impede the venous returnHigher pressure impede the venous return – Venous return becomes ZERO at only +7Venous return becomes ZERO at only +7 mm Hgmm Hg Mean systemic filling pressureMean systemic filling pressure – Higher pressure increase the venous returnHigher pressure increase the venous return Resistance to blood flowResistance to blood flow – Higher resistance reduce the venous returnHigher resistance reduce the venous return Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 44
- 5. Venous return curveVenous return curve Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 55
- 6. At +7 mm Hg Venous return is ZEROAt +7 mm Hg Venous return is ZERO So COP is also ZEROSo COP is also ZERO At such stage the pressure in all theAt such stage the pressure in all the circulatory components is +7 mm Hgcirculatory components is +7 mm Hg This is calledThis is called Mean Systemic Filling PressureMean Systemic Filling Pressure Very negative pressure below -4 mm HgVery negative pressure below -4 mm Hg doesdoes NOTNOT further increase VRfurther increase VR Big vein in the thorax are collapsed dueBig vein in the thorax are collapsed due to suction by very negative in RAto suction by very negative in RA Mean Systemic Filling PressureMean Systemic Filling Pressure (MSFP) (Psf)(MSFP) (Psf) Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 66
- 7. Heart stopped by shock or any otherHeart stopped by shock or any other meansmeans Blood flow ceases every whereBlood flow ceases every where Pressure every where becomes equalPressure every where becomes equal This is calledThis is called MeanMean CirculatoryCirculatory FillingFilling PressurePressure Almost same asAlmost same as Mean SystemicMean Systemic Filling PressureFilling Pressure Mean Circulatory Filling PressureMean Circulatory Filling Pressure (MSFP)(MSFP) Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 77
- 8. Calculations involving MeanCalculations involving Mean System Pressure (MSP)System Pressure (MSP) Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 88 PsF= Mean Systemic Filling Pressure RVR= Resistance to VPRA= Pressure in Right Atrium
- 9. Effect of MSFP on Venous returnEffect of MSFP on Venous return ↑↑ MSFPMSFP →→ – ↑↑ venous returnvenous return Greater the difference between MSFP andGreater the difference between MSFP and RA pressure greater is the Venous ReturnRA pressure greater is the Venous Return Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 99
- 10. Effect of Sympathetic NS on MCFPEffect of Sympathetic NS on MCFP SNS stimulationSNS stimulation →→ GeneralizedGeneralized vasoconstrictionvasoconstriction ↓↓ Total capacity of circulatory systemTotal capacity of circulatory system ↑↑ MCFPMCFP Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1010
- 11. Effect of MSFP on Venous returnEffect of MSFP on Venous return Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1111
- 12. Effect of venous resistance onEffect of venous resistance on venous returnvenous return Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1212
- 13. Measurement of COPMeasurement of COP Oxygen Fick MethodOxygen Fick Method RequirementsRequirements 1.1. Arterial OArterial O22 concentration /Lconcentration /L 2.2. RA ORA O22 concentration/Lconcentration/L 3.3. Volume of Total OVolume of Total O22 absorbed /minabsorbed /min by the lungsby the lungs COP =COP = OO22 absorbed/minuteabsorbed/minute AV OAV O22 difference (ml/L)difference (ml/L) Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1313
- 14. OO22 Fick methodFick method Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1414
- 15. Indicator Dilution Method for Measuring Cardiac Output Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1515
- 16. Indicator Dilution Method for Measuring Cardiac Output Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1616
- 17. Questions ?Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1717