Haemodynamics 2

Question 1

What is pulse pressure?

Answer 1

Peak systolic pressure - end diastolic pressure

(the difference between the systolic blood pressure and diastolic blood pressure)

Question 2

What is the mean arterial pressure?

How do you work out mean arterial pressure?

What is the mean arterial pressure NOT?

Answer 2

It is the average blood pressure throughout the cardiac cycle

Diastolic blood pressure + 1/3(pulse pressure)

NOT the arithmetic mean of SBP and DBP

Question 3

What is critical point of mean arterial pressure?

Answer 3

Below 70mmHg = organ perfusion becomes impaired

Question 4

In this equation (Darcy’s law), what does each variable represent?

Answer 4

Question 5

What is cardiac output? Units? Formula?

Answer 5

The amount of blood/flow that is leaving the heart at a given time

Volume/min ie ml/min

Stroke volume x heart rate

Question 6

What governs pulse pressure?

What will cause an increase in pulse pressure?

What else may impact pulse pressure?

Answer 6

1) Volume of blood ejected and compliance of arterial system

2) Increased stroke volume during exercise with relative compliance of vessels = increased pulse pressure

3)
Haemorrage - decrease in PP
Age - with age, a lot of people develop atherosclerosis , decrease in compliance

Question 7

What is the formula for mean arterial pressure and explain how it gets deduced?

Answer 7

MAP = CO X TPR

Question 8

What is a pulse?

Answer 8

Shock wave that arrives slightly before the blood itself

Question 9

What is a bounding pulse?

Answer 9

A pulse that is abnormally strong

Question 10

What is an increase in pulse pressure described as?
What is actually happening when pulse pressure is increasing?

Answer 10

• A bounding pulse
• There is a larger gap between systolic and diastolic pressures

Question 11

Describe 3 situations that could lead to/influence increasing pulse pressure

Answer 11

1) Heart block (conduction in the heart is compromised) so you become bradycardic (slow heart rate)

2) Vasodilatation due to hot bath or pregnancy ie, leads to decrease in peripheral resistance

3) Elite athlete like swimmers or track cyclists, as they train harder, you get increase in systolic pressure and decrease in diastolic

DOTTED line shows these things

Question 12

What causes pathological turbulence in blood flow?
Describe what is occurring in this case

Answer 12

Caused in a stenosed vessel through atheroma or stenotic heart valve or if a vessel is occluded in a particular way

Velocity increases through the stenosis and turbulence occurs beyond the stenosis

Question 13

How does measuring blood pressure work?

Answer 13

• Normally, blood flow is laminar so it’s silent
• Increase the cuff pressure to completely occlude brachial artery
• You get silence because you have occluded the brachial artery, so there’s no blood flow
• Gradually reduce cuff pressure
• Korotkoff sounds are produced
• Initial Korotkoff sound = systolic pressure/start of systole is indicated
• There’s some blood flow but it’s TURUBLENT FLOW
• Reduce cuff pressure further until cuff pressure < artery pressure
• When sound stops = diastolic pressure/start of diastole is indicated here
• Sound has stopped because there is now normal blood flow

Question 14

Describe how to manually measure blood pressure (5 marks)

Answer 14

• Inflate cuff around upper arm whilst palpating the brachial pulse [1 mark]
• Inflate to 30mmHg above the point where the pulse disappears [1 mark]
• Release pressure slowly, listening with stethoscope over brachial artery [1 mark]
• First Korotkoff sound = systolic pressure [1 mark]
• Fifth Korotkoff sound (where sounds disappear) = diastolic pressure [1 mark]

Question 15

What can be felt and heard when pathological turbulent flow occurs?

Answer 15

Thrill can be felt
Bruit (bro-eee) can be heard

(Velocity increases through stenosis, turbulence occurs beyond)

Question 16

What sounds do you hear when measuring BP?
What are these?

Answer 16

• Korotkoff sounds
• These are sounds that occur due to changes from laminar to turbulent blood flow which can be used to estimate blood pressure

Question 17

What is important when measuring blood pressure? (7)

Answer 17

1) Cuff size
- too small = will overestimate bp
- too big = will underestimate bp

2) Positioning of cuff - over brachial artery

3) Measure in both arms, often a difference, use the higher as reference arm

4) Sat comfortably, upright with legs uncrossed and flat on the ground

5) Supported arm on table

6) Repeat several times - take arithmetic mean of 2 values

7) MEASURE AT THE LEVEL OF THE HEART and at rest

Question 18

Gravity effects on BP

Answer 18

• In order for blood to flow, it needs to move from an area of high pressure to an area of low pressure
• Pressure below the level of the heart is higher than pressure above
• But blood is still able to move from the heart to the feet while standing
• Gravity enables this

Question 19

Describe how gravity enables blood to move from the heart to the feet while standing

Answer 19

• Gravity acts
• and maintains a pressure gradient,
• so the pressure above is now higher than the pressure below,
• allowing blood to move from the heart to feet whilst standing.

Question 20

Describe the concept of blood pooling an the effects

Answer 20

• Pooling of blood at the feet in the venous system when you stand up
• Less blood being returned to the heart initially
• Smaller stroke volume
• Lower stroke volume=less blood able to get to vital systems ie cerebral circulation.

Question 21

What is postural hypotension?

Answer 21

Dizziness upon standing from a decrease in stroke volume and transient arterial hypotension

Question 22

How do you calculate Mean arterial pressure with cardiac output?

Answer 22

MAP = CO x total peripheral resistance

Question 23

What is the slight raise on blood pressure graph after peak systolic?

What is happening here?

Answer 23

Dicrotic notch

Aortic valve closing = short increase in pressure