Module 5 Principles of spectral and colout doppler Flashcards
Hemodynamic intro - poisuilles law etc
Difference between blood density and viscosity.
Density of blood refers to its mass per unit volume, typically measured in grams per cubic centimeter (g/cm³), indicating how much matter is contained in a given volume of blood.
Viscosity of blood, is thickness of a fluid. Describes its resistance to flow, reflecting the internal friction between blood layers as they move past each other, and is measured in units such as poise or millipascal-seconds (mPa·s).
What is Hagen-Poiselles equation used for?
Hagen-Poiseuille’s equation is used to describe the flow of an incompressible and Newtonian fluid (like water or blood) through a long, cylindrical pipe with a constant cross-section. The equation relates the volumetric flow rate to the viscosity of the fluid, the pressure difference across the length of the pipe, and the pipe’s dimensions (length and radius). It is particularly useful for predicting the flow of fluids in situations where laminar flow conditions prevail, such as in small blood vessels or in laboratory settings involving narrow tubes.
What is Hagen-poiseulles equation look like?
What does Poisuilles law describes:
The relationship between flow, pressure and resistance
Turbulence in stenosis causes a sound called a what?
A brut
What is reynolds number and what does the formula/diagram look like?
to a dimensionless number used to predict the flow patterns of blood or other fluids within the body. It is a crucial parameter in fluid dynamics, indicating whether the flow is laminar or turbulent.
What is the velocity profile in a normal vessel?
Blunt flow to parabolic flow
What are the two flow options at a curve? If the blood is parabolic at the curve then what happens?
If the blood is blunt at the curve then what happens?
- If blood is is parabolic at the curve then it is skewed to the outer wall
- If it is blunt flow at the curve then it is skewed to the inner wall
What happens to flow at bifurcations?
-Bifurcation causes a disturbance in blood flow.
-The fastest moving flow is closest to the bifurcation
-The eddy currents and turbulence are on the other side of the vessel to the bifurcation
What happens to a velocity profile at a stenosis?
Velocity increase as it pass through the narrowing
-As it widens again–flow reversal/eddy currents/ vortices happen
What happens to a velocity profile at a stenosis?
Proximal to the stenosis frequencies are dampened.
As the flow passes through the stenosis there is and increase in doppler frequencies and is displayed as spectral broadening
After stenosis-chaotic colours - eddy currents etc
What is the calculation for velocity changes with stensis - hint – V-Q-CSA
When a reduction in CSA considered hemodynamically significant?
When the CSA is reduced by 70-80% it is considered hemodynamically significant.
What are the factors that affect stensosis?
