haemodynamics Flashcards
what is serum
plasma without clotting factors
what are plasma viscosity changes used to measure
inflammation
modern way of measuring inflammation
measure number C reactive proteins
what is laminar flow
smooth and silent flow
what is turbulent flow
noisy and disorganised flow. usually happens when pressure is disrupted e.g in ventricles or when branching occurs.
where within the vessel is the velocity the greatest
in the centre of the vessel due to the least resistance present here
what is pressure
force per unit area. e.g mmHg
what is the flow of the blood and why does pressure decrease.
moves down pressure gradient from high to low. decreases due to the cross-sectional area of the capillaries being the largest. this explains the drop in pressure
what is flow
volume transferred per unit of time
what is resistance and what is the calculation triangle to go with it
the measure of difficulty of flow (not ease like conductance therefore it is the reciprocal inverse of k) and the equation triangle is change in pressure over flow times resistance
what is conductance
it is the ease of flow (K)
how do you find TPR (total peripheral resistance)
add together the resistances in each vessel. more vessels means more resistance
changes in resistance in the CVS
resistance in the aorta is low because vessel is wide and short and is much higher in the arteries and arterioles. much lower resistance in the pulmonary system as vessels are wide and blood only needs to travel to lungs
what is velocity
distance of fluid moved in a given time (cm/s). low velocity in capillaries to allow material exchange die to the sudden increase in cross sectional area
calculation for flow
velocity x cross sectional area(pi r squared)
explain the pulse pressure change and how to calculate it
on graph pressure increases during systole and then decreases during diastole. pulse pressure is calculated by systolic BP-diastolic BP. it is the force produced every time the heart beats
how to calculate mean arteriole pressure
diastolic blood pressure + 1/3(pulse pressure) . it is the mean arterial pressure is an average blood pressure in an individual during a single cardiac cycle
reasons/ why pulse pressure increases
exercise due to increased stroke volume or bradycardia due to more diastolic run off meaning increased PP or vasodilation which decreases resistance increasing pulse pressure
reasons/ why pulse pressure
haemorrhage causes lower pressure due to lower volume of blood
how to calculate cardiac output
Stroke volume x heart rate
how to calculate mean arterial pressure from the cardiac output
cardiac output x total peripheral pressure.
why doesnt the mean arteriole pressure not increase during exercise
because it is very heavily regulated even though the systolic blood pressure increases.
how to measure blood pressure indirectly
increase pressure of brachial artery using cuff to prevent blood dole. when it is released the blood moves through in a turbulent style producing korotokoff sounds. when this starts it is the systolic BP and when these stop and flow goes back to laminar is the diastolic BP
how to measure blood pressure directly
canulation. however this is an invasive and dangerous technique
what makes a blood pressure measurement accurate
sitting relaxed with both feet on floor and reassuring several times with arm rested on table at heart level. this is because gravity affect BP. if you lift arm up then there is lower blood pressure and below heart it is higher. this is why you get dizzy when you stand up quickly because the blood pools in the venous system.
what does vessel diameter affect
it has huge effect on flow and resistance due to the 4th power relationship
