haemodynamics

Question 1

define systolic blood pressure

Answer 1

maximum blood pressure in the arteries

Question 2

at the brachial artery, what is the systolic blood pressure?

Answer 2

120 mmHg

Question 3

at what pressure is the systolic marginal hypertension?

Answer 3

140 mmHg

Question 4

at what pressure is the definite intervention threshold?

Answer 4

160 mmHg

Question 5

define diastolic blood pressure

Answer 5

minimum blood pressure in the arteries

Question 6

define pulse pressure

Answer 6

difference between the systolic and diastolic blood pressures

Question 7

how is the mean arterial pressure calculated?

Answer 7

diastolic pressure + 1/3 pulse pressure

Question 8

what causes compliance in arteries?

Answer 8

the elastic fibres in the artery wall

Question 9

why is compliance good?

Answer 9

reduces the work of the heart because some blood is stored in the arteries

Question 10

explain the effect of smoking on arteries, systolic volume and cardiac output

Answer 10

hardens arteries
increases systolic volume because aorta cannot stretch to accommodate SV
decreases CO bc ventricular contraction is longer

Question 11

what does the windkessel effect do?

Answer 11

helps reduce fluctuations in pulse pressure over the cardiac cycle
maintains organ perfusion during diastole

Question 12

what are the windkessel vessels?

Answer 12

aorta

large arteries

Question 13

explain the windkessel effect

Answer 13

arteries distend when BP rises in systole and recoil in diastole

in systole there is a net storage of blood bc of difference in rate of the blood entering and leaving the artery

net storage of blood is then released through recoil in diastole

Question 14

define hypertension

Answer 14

abnormally high blood pressure over 140/90

Question 15

what is prehypertension?

Answer 15

BP higher than normal but not enough to need medication

Question 16

what are the range of pressures for prehypertension?

Answer 16

systolic: 120-139
diastolic: 80-89

Question 17

how is local flow calculated?

Answer 17

pressure/local resistance

Question 18

what does Poiseuille’s law state?

Answer 18

at a constant pressure, the flow is proportional to the radius of the tube to the power of 4

small changes in arterial diameter produce large changes in flow

Question 19

how is cardiac output calculated?

Answer 19

heart rate x stroke volume

Question 20

define cardiac output

Answer 20

total blood flow out of the heart

Question 21

how can heart rate be measured?

Answer 21

from an ecg

Question 22

how can stroke volume be measured>

Answer 22

from echocardiography

Question 23

what is the usual heart rate?

Answer 23

70bpm

Question 24

what is the usual stroke volume?

Answer 24

70ml

Question 25

what is the typical cardiac output of a healthy adult male?

Answer 25

4.9L/min

Question 26

what method can be used to measure cardiac output?

Answer 26

doppler ultrasound

Question 27

explain how doppler ultrasound can be used to measure cardiac output?

Answer 27

blood velocity through the first part of the aorta causes a doppler shift in the frequency of the returning ultrasound waves ultrasound can measure cross sectional area of the aorta and uses this to calculate CO

Question 28

what are the advantages of doppler ultrasound?

Answer 28

``` non-invasive accurate inexpensive reliable reproducible ```

Question 29

explain how trans oesophageal doppler works

Answer 29

ultrasound probe inserted into the oesophagus at mid-thoracic level measures blood velocity in adjacent descending thoracic aorta

Question 30

what factors affect heart rate?

Answer 30

autonomic innervation hormones fitness levels age

Question 31

what factors affect stroke volume?

Answer 31

``` heart size fitness levels gender contractility duration of contraction preload afterload ```

Question 32

what are the oxygen requirements of vital organs?

Answer 32

brain - 700ml/min heart - 200ml/min kidneys - 1250ml/min

Question 33

how is blood flow through the skin varied?

Answer 33

increased via AV shunts | decreased via vasoconstriction

Question 34

how much can cardiac output be increased by?

Answer 34

3.75 times to 19L/min

Question 35

how is stroke volume increased during exercise?

Answer 35

contraction of atria - transfers blood to atria | increased ventricular contractility - smaller residual volume

Question 36

how does oxygen uptake increase during exercise?

Answer 36

faster breathing | dilation of bronchi and trachea means less resistance

Question 37

what does the work of the heart depend on?

Answer 37

blood viscosity | arteriole diameter

Question 38

what does the viscosity of the blood depend on and which factor has the biggest impact?

Answer 38

haematocrit - strongest impact RBC deformability RBC aggregation plasma viscosity

Question 39

what is haematocrit?

Answer 39

proportion of red blood cells in the total volume of blood

Question 40

what is polycythemia?

Answer 40

a disease where there's increased haematocrit

Question 41

what are the types of polycythemia

Answer 41

absolute - excessive production of RBCs relative - decrease in plasma volume

Question 42

explain how nitric oxide is released by blood vessels

Answer 42

edges of RBCs interact with polypeptide chains connected to proteins in the endothelium calcium moves into the endothelium nitric oxide forms and relaxes and dilates the walls

Question 43

what effect does nitric oxide have on the capillary wall?

Answer 43

local anticoagulant

Question 44

what does laplace's law state?

Answer 44

the pressure an elastic vessel can withstand depends on the tension produced in the walls by their elasticity divided by the radius of the vessel

Question 45

in a cyclinder, what is the pressure withstood proportional to?

Answer 45

T/R | tension/radius

Question 46

in a sphere, what is the pressure withstood proportional to?

Answer 46

T/2R

Question 47

describe the relationship between the radius of a vessel and the pressure it can withstand

Answer 47

the smaller the radius, the greater the pressure the wall can withstand

Question 48

what is an atheroma?

Answer 48

a fatty deposit on the inside of an artery

Question 49

what happens if an artery wall weakens?

Answer 49

radius increases balancing pressure that the tissue generates is less walls balloon out so its less effective at withstanding pressure aneurysm

Question 50

what is an aneurysm?

Answer 50

localised and abnormal weak spot on a blood vessel that can cause outward bulging

Question 51

what vessels are common sites for aneurysms?

Answer 51

aorta | cerebral arteries

Question 52

at what point in a blood vessel do aneurysms tend to occur?

Answer 52

just before points where the blood vessel branches

Question 53

what are risk factors for aneurysm formation?

Answer 53

hypertension | artery disease

Question 54

why do aneurysms commonly occur in cerebral arteries?

Answer 54

more convoluted and twisted than other arteries | more stress on the walls

Question 55

how can aneurysms present?

Answer 55

discovered incidentally during MRIs or angiography rupture causing subarachnoid brain haemorrhage symptoms of mass effect on neural structures

Question 56

how can cerebral aneurysms be treated?

Answer 56

clipping or coiling

Question 57

explain the process of coiling

Answer 57

fine wire is pushed into the swollen artery to form a coil | blood clots around the coil and takes pressure off the wall