Week 3 - Lesson 1 (Part 6) Flashcards
What is blood pressure effect by? (2)
- Peripheral resistance
2. Blood vessel elasticity
What does a healthy artery do? (4)
- Expands
- Absorbs the shock of systolic pressure
- each instant that the left ventricle contracts and forces a large bolus of blood into the system - Elastic recoil of the vessel
- Maintains the continued flow of blood during diastole
What happens to an individual that has arteriosclerosis? (2)
- Arteries become calcified and rigid
- so they can’t expand when the pulse wave of systolic pressure passes through them - The walls of the arteries experience higher pressures and become weaker and weaker
Where does atheroma develop?
In the arteries
What does atheroma do?
Impeds the flow of blood
How can you confirm atheroma?
Spectral doppler analysis
- depends on the extent of atheroma present and on the degree of obstruction
What kind of flow does a vessel have when flow enters it?
Plug flow
Plug flow
No leaders in velocity
- all at the same time
What happens to the flow pattern of blood as it moves along the normal straight unobstructed tube?
It becomes parabolic
- laminar (normal flow)
Where is the flow the highest/lowest in laminar flow? (2)
- Highest = in the centre
2. Lowest = at the walls
What is laminal flow determined by? (2)
- Frictional fouces
- Inertial forces
- between the layers of blood and changes throughout the pulse cycle
What kind of velocity for laminar flow have?
Low
What happens to the blood flow as the pressure wave propagates? (2)
- Flow begins as a result of high pressure to low pressure gradient
- Blood velocity increases uniformly across the vessel in early systole as fluid motion begins
What kind of velocity does turbulent flow have?
High
Turbulent flow (4)
- Abnormal flow
- Particular elements no longer travel along well-defined paths
- Random component to the motion of the fluid
- Significant irreversible loss of energy occurs
What are 2 essential flow states?
- Laminar
2. Turbulent
Disturbed flow
Is flow that is somewhere between laminar and turbulent flow
What is an example of disturbed flow?
The separation of flow that occurs in vessels with an obvious change in lumen size
- eg. the carotid bulb
What is the velocity in disturbed flow?
Will be more random and display itself as spectral broadening, but will not show an increase in velocity in a normal vessel
What is disturbed flow often an indication of?
Pathological change in the vessel
Where does disturbed flow occur? (4)
- Arterial dilatation
- Curvature
- Branching
- Bifurcation
What does turbulent flow create?
Eddy’s
- swirling
What does a clean signal look like on US? (6)
- Clean up stroke
- Low resistance
- Low flow
- Clean anechoic window
- Free floating above the base line
- Bright
What does a abnormal spectral broadening look like on US? (5)
- Turbulent flow
- Window is filled in
- Little bit below the baseline
- High pitch sound
- Aliasing
Where does turbulent flow mostly occur?
After a stenosis
- but some happen at the stenosis
Where does disturbed and turbulent flow occur?
In post stenotic regions
What does disturbed and turbulent flow give rise to?
Spectral broadening
Critical stenosis
Narrowing of the arterial lumen resulting in a hemodynamically significant reduction in volume, pressure and flow
What happens to pressure right before a stenosis?
It decreases
Why does pressure decrease before a stenosis?
In order to allow fluid to accelerate into the stenosis and decelerate out of it
What is the magnitude of blood cells dependent on?
The degree of the stenosis
Where is arterial pressure higher/lower? (2)
- Higher = proximal to the site of narrowing
2. Lower = distally to the site of narrowing
What is arterial pressure reduction distally accompanied by?
A loss of kinetic energy distal to the stenosis
What is the result of a disease progression?
Further loss of energy and pressure, which results in increased vasodilation
Mild turbulent
Little bit of filling, turbulence, not alot of change
Critical turbulent
Pressure decreases and velocity increases
