7 Haemodynamics Flashcards
What are the 2 main functions of elastic arteries?
dampening pulsatile pressure (Windkessel effect)
ensures blood pressure is maintained through diastole (conduit function)
What is the Pulse Pressure?
PP = SP - DP
What is Mean Arterial Blood Pressure?
((SP - DP) / 3) + DP
Why impact does the Windkessel effect have on venous return?
by the time the blood reaches the heart again, it is at a minimum pressure, the central venous pressure
What happens to the DP with age?
Why?
reduced elastic recoil leads to a lower DP
What happens to SP over age?
ejection of same or even reduced SV leads to increased SP
What happens to Pulse Pressure with age?
it increases, this is called atherosclerosis
What happens to vascular elastic fibres with age?
the degenerate and are slowly replaced by collagen which is much stiffer
What is the relationship between flow and pressure?
flow is directly proportional to a change in pressure
What is the relationship between flow and resistance?
flow is inversely proportional to resistance
What is the relationship between flow, pressure, and resistance?
flow is equal to change in pressure over resistance
What is PAOD?
peripheral arterial occlusive disease
athersclerotic plaques in large and medium sized arteries, particularly in the lower limb
Why do those with PAOD experience pain during exercise?
increases in metabolic demand can’t be met during exercise, so there is tissues ischaemia due to hypoxia
What is blood flow through vasculature like normally?
laminar flow, there is an immobile layer of plasma coating the vascular endothelium
What are the features of laminar flow?
normal pattern of flow
highly efficient
follows poiseuille’s law
What are the features of turbulent flow?
occurs where velocity is high
inefficient
cannot apply Poisuelles law
How would you detect turbulent flow clinically?
murmurs and korotkoff sounds
Why are korotkoff sounds important for taking blood pressure?
as you release pressure, you first hear korotkoff sounds at the level of systolic pressure
as the pressure is released, the flow becomes less turbulent and is laminar once diastolic pressure is reached
What is the level of ABP determined by?
blood volume in the arterial system (CO)
TPR
ABP = CO x TPR
What determines SP?
SV primarily
aortic/arterial distensibility
a lil bit of ejection velocity and DP of prev. beat
What determines DP?
arteriolar resistance
Heart rate
What can increase arteriolar resistance?
vasocontriction
arteriosclerosis
atherosclerosis
How can HR affect DP?
a very high HR increases DP as there is not enough time for pressure to decrease again
