Doppler Principles Flashcards
Flow
go from one place to another in a steady stream
velocity
the speed of something in a given direction
Pulsatile flow
blood that flows with variable changes with the cardiac cycle in arterial circulation
Phasic flow
when blood moves with a varying velocity, such as changes that occur with respiration (venous phase
Laminar flow
- Layers of fluid are straight and parallel to each other, they slide over each other
- Highest flow speed at center of vessel
- Minimum or zero speed at walls
- Results in parabolic flow profile
Plug flow
Flow with all fluid portions traveling with the SAME flow speed and direction (type of laminar flow)
Parabolic flow
Laminar flow with a profile shape of a bullet; middle layers of blood travel faster than the layers at the sides of vessels
Turbulent flow
- Random and chaotic flow pattern
- Particles move at different speeds in different directions
- Net result of forward flow is maintained
Disturbed flow
- Layers are now altered from their straight flow
- Occurs at bifurcations and at stenoses
- The layers are still moving in the forward direction so is a form of laminar flow
Bruit
Blowing, swishing sound indicating blood flow turbulence or atherosclerotic narrowing
Thrill
a thrill is considered a palpable cardiac murmur. It feels like the throat of a purring cat and is abnormal. It signifies turbulent blood flow and accompanies loud murmurs. Absence doesn’t necessarily mean a murmur isn’t present
Reynolds number
predicts wheather flow is laminar or tubulent
- laminar R# is 1,500.
- Turbulent flow Reynolds # is 2300
- critical reynolds number is 2000
Energy Gradient
total fluid energy at one location differs from the total fluid energy at another location causing an
Kinetic Energy
energy that a body possesses by virtue of being in motion.
Pressure Energy
Pressure is defined as force per unit area
-the heart acts like a pump in the body
Gravitational energy
potential energy associated with the gravitational field
Viscous / viscosity
- defined as the friction existing between contiguous layers of fluid
- The resistance to flow offered by a fluid in motion
- Water has a low viscosity compared to molasses
- Viscosity of blood is 5 times that of water
Frictional
of or produced by the action of one surface or object rubbing against or moving over another.
Inertial
Mass is an object’s resistance to acceleration or flow
The resistance is called inertia
Greater mass = greater inertia
Stenosis
Narrowing of a vessel lumen
Produces disturbed or turbulent flow
Effects of a Stenosis
produces disturbed or turbulent flow
Bernoulli’s Principle
- Explains that fluid moves against a pressure gradient from a point of low pressure to a point of high pressure
- Total fluid energy remains the same
- Pressure energy is converted to flow energy upon entrance to a stenosis
- As flow energy increases, pressure energy decreases (velocity goes up; pressure goes down)
Pressure flow Relationships
Fluid in a tube flows in response to a pressure difference at both ends
Blood flows in response to pressure differences
With equal pressures at both ends, fluid will not flow
The pressure difference can be generated by a pump (such as the heart) or by gravity
The greater the pressure difference, the greater the flow rate
Ohm’s Law
the voltage in a circuit equals the product of the current and the resistance
Hydrostatic pressure
The pressure that the fluid exerts on the walls of its container.
Expiration & inspiration
- inspiration- diaphragm contracts, expands, greater volume.
- expiration- passive, relaxation rib and sternum back in regular position
external/ internal respiration
- external respiration- moving gases from outside the body into the lungs and then the blood.
- Internal respirtaiton- gas exchange between blood and tissues
