Haemodynamics

Question 1

what is haemodynamics?

Answer 1

physical factors that control blood flow

Question 2

what does blood consist of ?

Answer 2

Blood is a fluid.

Consists of cells and plasma (fluid that contains proteins and electrolytes)

Question 3

what is the difference between plasma and serum?

Answer 3

serum is plasma without clotting factors

Question 4

Name some diseases that can affect whole blood viscosity

Answer 4

polycythaemia
thromobocythaemia
leukaemia

Question 5

what is C-reactive protein a clinical indicator of?

Answer 5

inflammation

Question 6

what is flow?

Answer 6

vol transferred per unit time (ml/min)

Question 7

what is pressure?

Answer 7

force per unit area (mmHg)

Question 8

what is vascular resistance?

Answer 8

resistance to flow in blood vessels

Question 9

features of laminar flow

Answer 9

adjacent layers of fluid slide over each other
‘streamline’
silent
flow is fastest in central layers

Question 10

features of turbulent flow

Answer 10

disorganised

noisy

Question 11

when is there turbulent flow

Answer 11

when the pressure increases but the flow can’t match it.
critical Reynolds number exceeded
e.g changing direction of vessels(branching), in stenosed arteries, stenotic heart valves

Question 12

factors affecting resistance to flow

Answer 12

diameter
length
viscosity
diameter is most important as length doesn’t change and viscosity is regulated

Question 13

where is resistance highest and lowest?

Answer 13

low in aorta as is has a large diameter and is short

high in smallest arteries and arterioles

Question 14

what is velocity

Answer 14

distance blood moves in given time (cm /s)

Question 15

why is velocity at capillary level slow

Answer 15

capillary brings oxygenated blood to tissues so enables exchange

Question 16

what is pulse pressure

Answer 16

systolic bp - diastolic bp

Question 17

what is pulse

Answer 17

shock wave that arrives slightly before blood itself

Question 18

what can cause a strong pulse ( increasing pulse pressure)

Answer 18

heart block-bradycardia
vasodilation-decrease in peripheral resistance -hot bath, pregnancy
elite athletes - systolic increased and diastolic decreases

Question 19

theory behind measuring arterial bp

Answer 19

normally blood flow is laminar so silent
if pressure in cuff is inflated above systolic pressure there is no blood flow (no sound)
as the cuff is deflated below systolic pressure blood will begin to flow but artery is partially compressed so flow is turbulent and you will hear kortokoff sounds.
cuff deflates more and when it passes below diastolic pressure there is no sound as now there is laminar flow

Question 20

what happens to flow in a stenosed vessel

Answer 20

velocity increases through the stenosis and turbulence occurs beyond it.
a thrill is felt
bruit is heard

Question 21

what happens if cuff is too small/big

Answer 21

small-overestimate bp

big-underestimate bp

Question 22

how does the effect of gravity maintain pressure gradient

Answer 22

pressure above heart is greater and below heart if lower.

when GPE is considered it increases the pressure at the feet so there is a slight gradient allowing blood flow.

Question 23

what is postural hypotension and what causes it

Answer 23

dizziness upon standing

low stroke vol as there is pooling at feet creating hypotension

Question 24

what is normal bp

Answer 24

s- less than 120

d- less than 80

Question 25

mean arterial pressure equation

Answer 25

mean arterial pressure =DBP + (SBP-DBP)/3

Question 26

CARDIAC OUTPUT EQUATION

Answer 26

CARDIAC OUTPUT=HR X SV

Question 27

mean arterial pressure equation

Answer 27

cardiac output x total peripheral resistance