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Hemodynamikk Hans Torp Fysiologi og Biomedisinsk Teknikk NTNU

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Hemodynamics Hemo from Haima = BloodHemo from Haima = Blood Dynamics from Dynamis ~ force which results in motionDynamics from Dynamis ~ force which results in motion Blood pressure -> Blood flowBlood pressure -> Blood flow Voltage current

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Normal blood pressure is not sufficient Voltage current

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Relation blood pressure / blood flow Blood pressure = Blood flow * periferal resistanceBlood pressure = Blood flow * periferal resistance periferal resistance increases by narrowing of capillariesperiferal resistance increases by narrowing of capillaries Blood flow to an organ may have substaial variation, with a constant blood pressureBlood flow to an organ may have substaial variation, with a constant blood pressure

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Blood flow – low periferal resistance Blood pressure Blood flow

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Blood flow – high periferal resistance Blood pressure Blood flow Spill film

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Hastighet [cm/s] versus volumstrøm [ml/s] V1 A1 Blodmengde som passerer areal A1: Q1 = V1 * A1 Hastighet V1 måles med Doppler, areal A1 måles på ultralydbilde Eksempel: V1= 30 cm/s, A1= 0.3 cm^2, Q1 = 9 ml/s = 54 ml/min

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Stenosis assessment V1V2 A1 A2 V1 * A1 = V2 * A2 % reduksjon A1 - A2 = V2 - V1 A1 V2 Example: 5x velocity corresponds to 80% stenose Degree of stenosis can be calculatet without angle correction

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Stenose + lekkasje i aortaklaff

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Pressure gradient in a stenosis V1V2 P1 P2 Bernouli’s equation: P1 - P2 = 4 V2 - 4 V1 22 V [m/s] P [mmHg] Hans Torp NTNU, Norway

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Fall i blodtrykk ved stenose V1V2 P1 P2 Bernouli’s ligning: P1 - P2 = 4 V2 - 4 V1 2 2 Significant stenosis (V2 >>V1) : P1 - P3 = 4 V2 Cinetic energy loss due to turbulence P3 2 Hans Torp NTNU, Norway

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Pressure gradient in a stenosis V1V2 P1 P2 Trykk - fall (gradient) : P1 - P3 = 4 V2 P3 2 Eksempel: 80% aorta-stenose V1= 1 m/s V2 = 5 m/s gir trykk-gradient 4*5*5 = 100 mmHg Hans Torp NTNU, Norway

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V1V2 P1 P2 Bernouli’s equation Pressure gradient: P1 - P3 = 4 V 2 2 P3 Example: 80% aortic-stenosis V1= 1 m/s V2 = 5 m/s ~ pressure gradient of 4*5*5 = 100 mmHg Left ventricular pressure of 220 mmHg is required to achieve 120 mmHg aothic pressure Hans Torp NTNU, Norway Pressure gradient in a stenosis

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Blood Pressure. Blood pressure is the force exerted by the blood against the walls of the blood vessels. It is necessary to maintain blood flow though.

Blood Pressure. Blood pressure is the force exerted by the blood against the walls of the blood vessels. It is necessary to maintain blood flow though.

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