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HemodynamikkHemodynamikk
Hans TorpFysiologi og Biomedisinsk Teknikk
NTNU
HemodynamicsHemodynamics
• Hemo from Hemo from Haima =Haima = Blood Blood
• Dynamics from Dynamics from Dynamis ~ Dynamis ~ force which results in force which results in
motionmotion
• Blood pressure -> Blood flowBlood pressure -> Blood flow
Voltage
current
Normal blood pressure is not Normal blood pressure is not sufficientsufficient
Voltage
current
Relation Relation blood pressure / blood flowblood pressure / blood flow
• Blood pressure = Blood flow * periferal resistance Blood pressure = Blood flow * periferal resistance
• periferal resistance increases by narrowing of periferal resistance increases by narrowing of
capillariescapillaries
• Blood flow to an organ may have substaial variation, Blood flow to an organ may have substaial variation,
with a constant blood pressure with a constant blood pressure
Blood flow – low periferal Blood flow – low periferal resistanceresistance
Blood pressure
Blood flow
Blood flow – high periferal Blood flow – high periferal resistanceresistance
Blood pressure
Blood flow
Spill film
Hastighet [cm/s] versus volumstrøm Hastighet [cm/s] versus volumstrøm [ml/s][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
Stenosis assessmentStenosis assessment
V1 V2
A1 A2
V1 * A1 = V2 * A2
% reduksjon A1 - A2 = V2 - V1 A1 V2
Example:
5x velocitycorresponds to
80% stenose
Degree of stenosis can be calculatet without angle correction
Stenose + lekkasje i aortaklaffStenose + lekkasje i aortaklaff
Pressure gradient in a stenosisPressure gradient in a stenosis
V1 V2
P1 P2
Bernouli’s equation: P1 - P2 = 4 V2 - 4 V1 2 2V [m/s]
P [mmHg]
Hans TorpNTNU, Norway
Fall i blodtrykk ved stenoseFall i blodtrykk ved stenose
V1 V2
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 TorpNTNU, Norway
Pressure gradient in a stenosisPressure gradient in a stenosis
V1 V2
P1 P2
Trykk - fall (gradient) : P1 - P3 = 4 V2
P3
2
Eksempel: 80% aorta-stenoseV1= 1 m/s V2 = 5 m/s gir trykk-gradient 4*5*5 = 100 mmHg
Hans TorpNTNU, Norway
V1 V2
P1 P2
Bernouli’s equation Pressure gradient: P1 - P3 = 4 V22
P3
Example: 80% aortic-stenosisV1= 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 TorpNTNU, Norway
Pressure gradient in a stenosisPressure gradient in a stenosis