Haemodynamics Flashcards
What is laminar flow?
Smooth, silent, maintains energy.
Typical of arteries and veins.
What is turbulent flow?
Disorganised, energy loss, due to a pressure increase beyond which flow can match linearly
Ventricles to arteries
Branching in arteriolar
What is flow?
Volume transferred per unit time
What affects flow?
Low resistance increases flow
Higher pressure change increases flow
UNTIL it reaches turbulent flow
What is pressure?
Force per unit area mmHg
What causes TPR?
Where is it lowest?
MOSTLY arterioles
Lower in pulmonary circulation due to shorter and wider vessels
What is velocity?
Distance fluid moves in a given time (cm/s)
What affects velocity?
What affects velocity the most?
Vessel length, Viscosity, MOSTLY diameter (cross sectional area)
What is pulse pressure ?
Volume of blood ejected and compliance of arterial system to govern pulse pressure
What increases pulse pressure?
Heart block, brachycardia
Lower TPR
Elite athletes have a higher SP but a lower DP
What affects resistance?
Diameter, length of vessel, viscosity.
What is the r^4 rule and why is it important to blood flow?
A change in diameter of a vessel will impact flow/resistance by ^4.
Small change is diameter = BIG difference
What is the effect of gravity on BP?
Pressure below the heart is greater than above the heart. Maintains a pressure gradient.
What happens to blood pressure upon standing?
What is this called?
Pooling of blood occurs below the heart, near the feet. Venous return is reduced which lowers stroke volume, lowering arteriole pressure.
Causes postural hypotension which causes dizziness upon standing.
Lowers stroke volume so transient arterial hypotension.
How do you measure pulse pressure?
SBP - DBP
