Haemodynamics Flashcards
Difference between serum and plasma
Plasma- fluid collected from unclotted blood
Serum- fluid collected from clotted blood
Units for flow and pressure
Flow- L/min, mL/min (for blood)
Pressure- mmHg (BP), Pascal (SI unit)
What is the equation for flow and what is the name of this law?
Flow= ΔP/R
Darcy’s law
What does K and R stand for
K- conductance (measure of ease of flow)
R- resistance (measure of difficulty of flow),1/K
Define resistance in blood flow
The difference in mean pressure needed to move one unit of flow in steady state (mmHg min/mL)
Vascular resistance
Resistance to flow in blood vessels
Describe the relationship between resistance (R) and perfusion pressure (ΔP) and flow
Flow and resistance are reciprocally related
Flow UP, ΔP UP
R UP, Δ P UP
Laminar flow and turbulent flow
Laminar flow: silent, smooth
Turbulent flow: noisy, disorganised
Sketch the graph showing the relationship between flow,resistance and perfusion pressure
Draw a sketch describing the relationship between flow and perfusion pressure in laminar and turbulent flow
3 factors creating turbulent flow
Branching of vessels
Change in direction of blood flow
Stenosis
Name the point at which turbulent flow is created
Critical Reynolds number
What is a stenosis
Abnormal discrete narrowing of an artery / open area of a heart valve
3 primary factors for flow resistance
Diameter, length of vessel, viscosity
What is the most (physiologically) important factor for determining flow resistance
Diameter
What doesn’t change resistance flow
Vessels length
Viscosity