Ch 13 Spectral Doppler Flashcards
Hemodynamics is based on the investigation of what 2 physical principles?
Blood flow + circulation
The fundamental doppler principles are partly based on what principles?
Hydraulic principles: investigation of steady flow of a uniform fluid through a solid tube
Blood is not uniform due to what?
Containing solid matter
(it travels through “elastic tubes” which expand + contract)
Blood flow characteristics are based on a range of factors, list 5?
-Type of vessel (artery vs vein)
-Size of vessel
-Resistance to flow offered by vessel
-Phase of cardiac cycle the flow is occurring
-Disease processes which cause vessel narrowing
What is the driving force behind all fluid flow?
Pressure - differences in pressure is required for flow to occur
Does flow follow the path of least or most resistance?
Least - ex. higher pressure at 1 end of a tube than another causes fluid to move from an area of higher pressure to an area of lower pressure
Blood flows from the LA into the LV once when happens?
Once the pressure in the LA exceeds the pressure in the LV, causing the MV to open
Resistance to flow is determined by that 3 factors?
-Bloods viscosity
-Radius of vessels lumen
-Length of vessel
Rate of flow is determined by what 2 things?
-Pressure difference
-Resistance to flow
Define viscosity?
The ease in which fluid particles move past one another
Higher viscosity causes greater or lesser resistance to flow?
Greater
Define Poiseuille’s Law?
Relationship b/w flow rate, pressure difference + resistance
Define laminar flow?
Movement of fluid in “layers” or streamlines that travel parallel to one another, in the same direction + at approx the same velocity
List 4 types of laminar flow?
-Plug
-Parabolic
-Skewed
-Disturbed
Where would plug flow occur?
At entrance of a vessel where velocities of all streamlines are roughly the same, with the exception of mild disturbances caused by valves
Examples:
-RVOT + LVOT
-MV + TV inflows
Define parabolic flow? Where would this occur?
-Occurs in long, straight vessels.
-Walls cause friction + slowing of flow, while the center moves at a higher velocity
Examples:
-Peripheral vessels of cardiovascular system
-Pulmonary veins
Define curved skewed flow? Where would we see this flow?
-Asymmetric flow profile caused by vessel curvature.
-Higher velocities on the outside curve, lower velocities on the inside curve.
Example:
-Carotid artery
Define U-Shaped skewed flow? Where would we see this flow?
-Complex flow based on many variables.
-Higher velocities on inner side of ascending limb + on outer side of descending limb.
Example:
-Aortic arch
Define disturbed flow? Where would we see this flow?
-Laminar blood flow that is NOT traveling in a straight path.
-There is laminar flow at the outer walls of the vessel, then slower circular flow (Eddy flow) on the inner side of branches.
Example:
-PA Bifurcation
When would turbulent flow occur?
When blood passes through an area of obstruction or a narrowed orifice
Examples:
-Stenosis
-Regurgitation
-Septal defects
Flow obstructions increase or decrease velocities?
Increases - causing a curling whirlpool flow pattern called vortices (casts off jets at different velocities + directions)
If there is an increase in velocity at a narrowing/stenosis, what happens to the pressure?
There is a decrease + drop in pressure at the stenosis
According to the continuity principle, when there is a narrowed orifice will the blood velocity increase or decrease across it?
Must increase
The continuity principle is based on conservation of what?
Mass - “whatever mass flows in, must flow out”