Peripheral Vascular System Flashcards
Fick’s Principle (2 eqs)
Amount = V x C, or Utilization rate = Flow x DeltaC
3 Alternate Methods of Cardiac Output
Dilution Method: output of heart equal to amount of indicator injected divided by avg conc in arterial blood after single circulation through heart
Doppler Ultrasound: CO = SV x HR, and SV = VTI (velocity time integral) x CSA (valve orifice cross sectional area)
Echocardiography
Ohm’s Law Relating to Fluid Flow
Q = DeltaP/R
Flow =
Mean velocity x area
Turbulent Flow (determinant and only place in body you have to worry about it)
Reynolds number > 2000, just past valves
Hematocrit and O2 Transport
Increased hematocrit increases O2 carrying capacity, but also viscosity which reduces flow. So two opposing forces for O2 transport, so the curve has a sharp peak around 40-60
Kirchoff’s Law (and how it relates to blood flow)
Series of Resistors is additive, parallel resistors are 1/R. So sequential resistances/pressure drops add, but resistances in different tissues often in parallel (except lungs) so 1/TRP = 1/Rbrain + 1/Rmuscle, etc
Laplace Law (and how it relates)
P = T/r, so arterioles don’t need much T/smooth muscle for significant P store
Windkessel Function of Aorta
To create a solid stream from pulses - instead of air dome like windkessel pipe that will become compressed and expand, the compliance of the vessels create that effect
Compliance =
DeltaV/DeltaP
Pulse Waves as you get Further From Aortic Valve (2)
Systolic pressure peak gets sharper/higher because wave reflection at each branch point, but flow pulse decreases
MAP Estimate from BP
MAP = Pdias + (Psys - Pdias)/3 (spends about 1/3 of time in systole)
MAP =
CO x TPR
SV =
Pp x Compliance
