Haemacodynamics Flashcards
What is meant by flow?
Volume transferred per unit time (L/min)
What is meant by velocity?
The distance blood moves in a given time. (Cm/s)
What is a stenosed vessel?
A blood vessel which is obstructed in some way.
How does a stenosed vessel affect flow and velocity?
The obstruction reduces flow but increases velocity.
What can be heard and felt over a stenosed vessel?
‘Bruit’ can be heard (french for noise)
‘Thrill’ can be felt.
How is blood flow increased to tissues?
Blood flow is increased by decreasing resistance.
How is resistance decreased?
Increasing vessel diameter.
Decreasing vessel length.
Decreasing plasma viscosity.
What has the greatest impact on resistance within a vessel?
The diameter of the vessel.
Small changes to the diameter will have massive effects on the resistance.
Which vessel type has the greatest effect on total peripheral resistance?
Arterioles.
Why is lower velocity useful in capillaries?
The lower velocity gives more time for exchange to occur between tissue and the capillaries.
Time is needed for the diffusion.
What is pulse pressure and what is its formula?
It is an indicator of the force that the heart produces in each cardiac cycle.
PP = Systolic blood pressure - Diastolic blood pressure
What is mean arterial pressure and how do you calculate it?
It is the average pressure of blood within the arteries.
MAP = Cardiac output x Total peripheral resistance
OR
MAP = Diastolic blood pressure + 1/3 Pulse pressure
Define systole
Phase of the cardiac cycle where the heart contracts to pump blood into arteries
Define Diastole
Phase of the cardiac cycle where the heart relaxes in order to let its chambers fill with blood.
