TheCirculatorySystem

On model elements compliant vessel qin mls qout mls v

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Unformatted text preview: Arterial Compliance In this preparation, stroke volume decreased as compliance decreased so MAP went down as PP went up. 10 Varia?ons in Arterial Pressure Waveforms Moving along the arterial tree: •  High frequency components are damped •  Pulse pressure increases •  Pressure wavespeed increases •  Diastolic bump appears and grows Sphygmomanometry 11 The Cardiovascular Baro- Reflex The cardiovascular baro- reflex 12 Circulatory Models Windkessel Model w༇  windkessel = airkettle w༇  used in plunger pumps to ensure a steady flow 13 Circula?on Model Elements: Compliant Vessel qin [ml/s] qout [ml/s] V [ml] Conservation of mass: dV/dt = qin - qout 32 Circula?on model elements: Compliant Vessel Compliant vessel V [ml] p [kPa] C [ml/kPa] Pressure in vessel: p = V/C 33 14 Circula?on model elements: Resistance R [kPa.s/ml] pin [kPa] pout [kPa] q [ml/s] Flow over resistance: q = (pin - pout)/R 34 Circula?on model elements: Bifurca?on q2 q1 q3 Conservation of mass: q1 = q 2 + q 3 35 15 Circula?on model elements: Compliant Vessel + Resistance pin qin R V pout qout C pin = V/C qout = (pin-pout)/R dV/dt = qin - qout 36 Circula?on model elements: Compliant Vessel + Resistance pin qin R V pout qout C By substitution of pin and qout in dV/dt: qin = C.dpin/dt + (pin-pout)/R With: pout = 0 pin = plv qin = qao R = Rper C = Cart this leads to ... 37 16 Two- element Windkessel model: OWo Frank (1899) Compliant vessel + Resistance Rper plv qao V qout Cart qao = Cart.dplv/dt + plv/Rper 38 Two- element Windkessel model: Circuit Analog Rper plv qao V qout Cart I3≅qout I1≅qao I2≅dV/dt U≅plv Cart Rper 39 17 Two- element Windkessel model: Circuit Analog Rper plv qao qout V Cart The 2wk model produces unrealistic aortic pressure waves, especially at higher frequencies 40 Three- element Windkessel model: (Broemser, 1930) Compliant vessel + two Resistances plv qao Zao V part Rper qart Cart part = V/Cart qao = (plv-part)/Zao qart = part/Rper dV/dt = qao - qart plv: part: qao: Zao: Rper: Cart: V: LV pressure arterial pressure aortic flow aortic impedance peripheral resistance arterial compliance volume of aorta 41 18 Three- element Windkessel model: (Broemser, 1930) Compliant vessel + two Resistances plv qao Zao V part Rper qart Cart Produces realistic aortic pressure and flow waves 42 A model of the Baro- reflex Lu et al (AJP 2001) 19...
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This document was uploaded on 04/09/2014.

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