Haemodynamics

Question 1

What is haemodynamics?

Answer 1

The physical factors that control blood flow

Question 2

What dictates the delivery of blood to different organs?

Answer 2

The metabolic demands of the organs

Question 3

What determines the way that blood moves?

Answer 3

The pressure gradient
(High pressure to low pressure)
Flows as a fluid from a high pressure to a low pressure

Question 4

What is the composition of blood?

Answer 4

Red blood cells
White blood cells
Plasma

Question 5

What is serum?

Answer 5

Plasma with no clotting factors (no platelets …)

Question 6

What is the affect of heparin on the blood?

Answer 6

Makes it unable to clot

Question 7

How can the whole blood viscosity change?
How does this affect the blood?

Answer 7

Changes in number of blood cells:
Polycythaemia (more RBCs/higher Haematocrit)
Thrombocythaemia (more platelets)
Leukaemia (more WBCs)

Thicker sludge blood - gangrene in peripheries

Question 8

How can plasma viscosity change?

Answer 8

Plasma protein composition can change
-fibrinogen
-c reactive proteins

Question 9

What is C-reactive protein used to measure?

Answer 9

Inflammation
High usually indicates bacterial infection

Question 10

What is the FLOW of blood?

Answer 10

Volume of blood transferred per unit time
Ml/min or L/min

Question 11

What is pressure and what is blood pressure measured in?

Answer 11

Force per unit area exerted by the blood
(mmHg) mm of mercury

Question 12

What is cardiac output? (Equation)

Answer 12

CO = stroke volume x heart rate

Question 13

What is stroke volume?

Answer 13

Volume of blood squeezed out of the left ventricle every cardiac cycle

Question 14

What factors influence FLOW of blood?

Answer 14

Conductance (ease of flow/resistance)
Pressure gradient/difference

Question 15

What equation can relate flow to conductance and pressure difference?

Answer 15

Flow = conductance x pressure difference

Question 16

What is vascular resistance?

Answer 16

Resistance to blood flow in blood vessels

Question 17

How are resistance and flow related?

Answer 17

Inversely proportional
As resistance increases flow decreases

Question 18

What factor is normally changed if flow needs to be increased to an area?

Answer 18

Resistance decreased

Question 19

What are the 2 types of blood flow?

Answer 19

Laminar flow (smooth/silent and maintains energy, travels in stream lines)

Turbulent flow (disorganised, noisy energy lost)

Question 20

What is a stenosis?

Answer 20

Abnormal discrete narrowing of an artery or open area of a heart valve

Question 21

What point does laminar flow become turbulent?

Answer 21

When flow can not increase proportionally to match the increased pressure in the blood vessel

Question 22

What is the point called which pressure increases beyond which flow can match it linearly so flow becomes turbulent?

Answer 22

Critical Reynolds number

Question 23

What is the main factor which affects resistance to blood flow?

Answer 23

Blood vessel diameter
(Vessel length doesn’t usually change and viscosity is very tightly regulated)

Question 24

What does a drop in pressure indicate in terms of resistance to flow?

Answer 24

Changed

Question 25

Why does the aorta have a low resistance?

Answer 25

Large diameter Short

Question 26

Which blood vessel type has the biggest affect of total peripheral resistance?

Answer 26

Arterioles

Question 27

What is velocity?

Answer 27

Distance fluid (blood moves in a given time

Question 28

The capillaries have a very large cross sectional area, this slows blood flow down, why is this useful?

Answer 28

Allows time for nutrients and waste to be exchanged between blood and tissues

Question 29

Does increasing vessel diameter increase or decrease blood velocity? Why does this happen?

Answer 29

Increases Inc vessel diameter = less resistance (less blood touching vessel wall/less friction) = more blood flow at higher speed

Question 30

What is diastole?

Answer 30

When heart is relaxed and filling up with blood

Question 31

What is systole?

Answer 31

When heart contracts squeezing out blood

Question 32

What is pulse pressure?

Answer 32

Difference between peak systolic pressure and end diastolic pressure

Question 33

What is considered a normal blood pressure?

Answer 33

120/80 mmHg or below (90/60 - 120/80 mmHg)

Question 34

What is the Dicrotic notch on a blood pressure time graph?

Answer 34

The point which pressure starts to increase when the atrioventricular valves close

Question 35

What are the 2 equations for Mean Arterial pressure?

Answer 35

MAP = Diastolic blood pressure + 1/3(Pulse pressure) MAP = Diastolic blood pressure + 1/3(Systolic pressure - Diastolic pressure) OR MAP = Cardiac output x total peripheral resistance

Question 36

What determines pulse pressure?

Answer 36

Volume of blood ejected (SV) Compliance of the blood vessels

Question 37

How does haemorrhaging affect pulse pressure?

Answer 37

Decreases it Less blood volume ejected

Question 38

How can age affect pulse pressure, what condition of the vessels usually occurs with age? How does this affect pulse pressure?

Answer 38

Atherosclerosis reduces vessel compliance Increased pulse pressure as vessel compliance reduces

Question 39

What is the pulse?

Answer 39

The shock wave that arrives before the blood

Question 40

What does a strong and weak pulse indicate (in terms of stroke volume)?

Answer 40

Strong = high stroke volume Weak = low stroke volume

Question 41

What happens to the velocity of blood in a stenosis?

Answer 41

Initially it decreases since the resistance of the vessel increases since its become narrower So the heart pumps harder increasing stroke volume to increase the velocity to maintain the cardiac output

Question 42

What can be heard from a stenosed vessel?

Answer 42

Bruit

Question 43

What can be felt from a stenosed vessel?

Answer 43

A thrill

Question 44

Why can a thrill be felt and a bruit be heard from a stenosed vessel?

Answer 44

Laminar flow changed to turbulent flow by narrowing of the blood vessel

Question 45

How is blood pressure measured?

Answer 45

Using a pressure cuff

Question 46

What artery is targeted and squeezed by the pressure cuff?

Answer 46

Brachial artery

Question 47

Describe how a pressure cuff is used to measure blood pressure:

Answer 47

Pressure of cuff increased restricting blood flow through the brachial artery occluding it Pressure is then slowly reduced blood flow is changed from laminar to turbulent flow causing sounds to be heard called Korotokoff sounds First point at which Korotokoff sounds can be heard is the systolic blood pressure Once the blood flow goes from turbulent to laminar/silent this is the diastolic blood pressure

Question 48

What are Korotokoff sounds?

Answer 48

The tapping noises created by converting laminar flow into turbulent flow

Question 49

How is systolic pressure determined using a pressure cuff?

Answer 49

When the Korotokoff sounds are first heard (tapping noises)

Question 50

How is diastolic pressure determined using a pressure cuff?

Answer 50

Pressure at which the Korotokoff sounds stop being heard (Turbulent flow is now laminar/silent)

Question 51

What is the role of gravity in blood pressure?

Answer 51

Maintains a pressure gradient allowing blood to flow from heart to the feet

Question 52

Is blood pressure above the heart greater than below the heart?

Answer 52

Blood pressure above the heart is less than below it

Question 53

What is postural hypotension?

Answer 53

When blood pools in your feet/ venous system below your heart as you are sitting down Reduces blood flow to head when you stand up (may faint)

Question 53

What is postural hypotension?

Answer 53

When blood pools in your feet/ venous system below your heart as you are sitting down Reduces blood flow to head when you stand up (may faint)

Question 54

What is the average cardiac output for the average 70kg male?

Answer 54

5 L/min