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Arterial Pressure

Arterial Pressure. and Elastic Properties of the Blood Vessels and Heart. Which one is more elastic?. Elastance is a measure of how strongly a material pulls back. Force. Slope =. Length - L 0. Stiffness (“Elastance”). less elastic. Force exerted by elastic material.

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Arterial Pressure

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  1. Arterial Pressure and Elastic Propertiesof the Blood Vessels and Heart

  2. Which one is more elastic? Elastance is a measure of how strongly a material pulls back.

  3. Force Slope = Length - L0 Stiffness (“Elastance”) less elastic Forceexerted by elastic material l0 (resting length) Length

  4. Stress Force = 1 Newton Force = 4 Newton A measure of the work done by each muscle cell.

  5. ∆Pressure Pressure Slope= Stiffness (elastance) = Volume - V0 ∆Volume = Elasticity in three dimensions more elastic Pressureexerted by elastic material on fluid inside V0(unstressed volume) Volume

  6. P = TM Pericardial Sac PRV = 4 mmHg PPS = - 3 mmHg Transmural Pressure= Pin - Pout 7 mmHg

  7. ∆Volume 1 stiffness Compliance = = ∆PressureTM more compliant Volume Transmural Pressure Compliance V0(unstressed volume)

  8. h (wall thickness) tension = P x r 2 Stress in three dimensionsLaw of LaPlace force exerted P r

  9. P Pressure overload increased diastolic compliance Ventricular Hypertrophy Volume overload “dilation”

  10. External Work of the Heart Pressure Overload Volume Overload • Increased by • Pressure increase • Volume increase

  11. Internal Work of the Heart Internal work( internal energy necessary to generate active wall stress ,or tension) depends on • Pressure Generated (P) • Ventricular Radius (r)  by Pressure overload  by Volume overload Hypertrophy (or dilation) increases the internal work!

  12. Elastic Arteries Elastic fibers in media

  13. Determinants of Pulse Pressure Systolic Arterial Pressure Pressure kPa kPa mm Hg 16 120 12 Pulse Pressure 80 8 Diastolic Arterial Pressure 40 4 0 0

  14. Slope = Elastance Pulse Pressure Increase in arterial volume during rapid ejection Pulse Pressure Aortic Pressure (mmHg) Volume (% of "normal")

  15. IncreasedPulse Pressure Higher Systolic Pressure Lower Diastolic Pressure Increase Stroke Volume Aortic Pressure (mmHg) Volume (% of "normal")

  16. Increased Pulse Pressure Higher Systolic Pressure Lower Diastolic Pressure Decreased Arterial Compliance 70 yrs Aortic Pressure (mmHg) 20 yrs Volume (% of "normal")

  17. SAP + DAP Mean Arterial Pressure ≠ 2 Integrate electronically Mean Arterial Pressure Systolic Arterial Pressure = 120 mm Hg Diastolic Arterial Pressure = 80 mm Hg Estimate as Diastolic Pressure + 1/3 Pulse Pressure

  18. Pdriving PRA (right atrial) = ˙ ˙ Q Q R RTP = Pa - PRA Pa(mean arterial) ˙ Q Pdriving ˙ R = Q(Cardiac Output) Total Peripheral Resistance

  19. = RTP Pa - PRA X ˙ ˙ Q Q = RTP Pa X ˙ Q(Cardiac Output) Pa(mean arterial pressure) RTP = Pa - PRA ˙ Q Determinants of Arterial Pressure = X RTP (total peripheralresistance) HR X SV Tuesday Next

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