Lecture 11: Blood pressure

Question 1

What two factors does hypertension lead to?

Answer 1

• Increased afterload

- Arterial damage (shear damage)

Question 2

What can cause increased afterload? And what is the impact of increased afterload on the heart on a pathological level?

Answer 2

Hypertension -> Inc. afterload

• Systolic dysfunction
• LVH —–> diastolic dysfunction
• Increased myocardial oxygen demand (MI risk)

= Heart failure

Question 3

Hypertension causes arterial damage, what are the consequences of this?

Answer 3

Hypertension -> arterial damage

• Accelerated atherosclerosis (coronary (Dec. O2 supply), cerebral (ischeamic stroke), aorta(aneurysms and dissection))
• Weakened vessel walls, Cerebral (stroke risk), Renal vessels (Renal failure->viscous cycle), opthalmic vessels (retinopathy)

Question 4

Describe the pathophysiological impact of hypertension on vessel walls:

Answer 4

Hypertension
->
Increased wall tension
->
ANG2, VGF, Endothelin, oxidative stress etc (factors released)
->
Remodelling: Thicker, stiffer wall, smaller lumen (hypertrophy)

Question 5

How is MAP calculated? Using blood pressure cuff measures

Answer 5

MAP = P(D) + 1/3 (P(S)-P(D))

1/3 contraction
2/3 Relaxation

Question 6

What happens to blood pressure with age?

Answer 6

Systolic, Diastolic and mean increase with age.

Question 7

What are the determinants of MAP?

Answer 7

MAP = CO x TPR

Question 8

What are the cardiac and non-cardiac influences of cardiac output

Answer 8

Cardiac:

• Heart rate
• Inotropic state
• Neural
• Hormonal

Renal fluid, volume control:

• Renin-Angiotensin
• Pressure natriuresis
• Aldosterone
• Atrial Natriuretic factor

Question 9

What influences peripheral resistance?

Hint (SLH)

Answer 9

SNS

• Vasoconstrictor (alpha)
• Vasodilator (beta)

Local Autoregulation

Humoral

• Vasodilator
• Vasoconstrictor
• Prostaglandin
• Angiotensin
• Kinins
• Catecholamines

Question 10

How is pulse pressure calculated?

Answer 10

Pulse pressure = Systolic pressure - diastolic pressure

Question 11

What influences systolic pressure?

Answer 11

Systolic pressure:

• Aortic compliance
• Stroke volume (and ejection rate)

Compliance changes pulse pressure doesnt change MAPB

Question 12

What influences diastolic pressure?

Answer 12

Diastolic pressure

• Aortic compliance
• Diastolic run off:
  
  • HR
  • TPR

Question 13

How does compliance change pressures?

Answer 13

Diastolic and systolic pressure change with aortic compliance

MABP - Depends on downstream

Question 14

What is the equation for compliance?

Answer 14

Change volume / Change pressure = Compliance

For a given stroke volume into the aorta (V), the aortic pulse pressure is increased when the compliance is reduced.

Question 15

Describe what aortic pulse pressure is;

Answer 15

During systole the aorta stretches to absorb the blood

• Flow continues during diastole due to compliant nature of blood vessels
• The more compliant the large blood vessels the smaller the pulse pressure i.e pulse becomes non-pulsitile by the time it reaches the small arterioles

Question 16

What happens to compliance with age?

Answer 16

Compliance of blood vessels decreases with age

i.e pulse pressure decreases

Question 17

What does compliance ensure?

Answer 17

Continuous capillary flow throughout the cardiac cycle

Question 18

What is a consequence of decreased compliance with age?

Answer 18

• Systolic pressure increases

- Diastolic pressure may decrease

Question 19

What happens with aortic pulse pressure and age?

Answer 19

Compliance of the aorta tends to decrease with age and results in a larger pulse pressure.

Question 20

How does stroke volume influence pulse pressure?

Answer 20

Larger SV increases arterial pulse pressure (Inc. SV = Inc. systolic pressure)

Systolic pressure can increase in exc. b/c of this

Question 21

What influences SV?

Answer 21

Preload
Afterload
Chronotropy
Inotropy

Question 22

What determines diastolic pressure and what influences these?

Answer 22

Diastolic run off determines diastolic pressure i.e the ability of blood to flow forward which is dep. on;

• TPR (Inc TPR = Inc DP)
• HR

Question 23

When taking someones pulse what are you feeling?

Answer 23

The pulse wave i.e you feel the pulse that has travelled through the blood from the heart not the flow of blood which travels much slower.

Question 24

On a standard pulse waveform from the proximal aorta, what is the incisura?

Answer 24

Semilunar valve closure

Question 25

What is the palpation method of pressure measurement?

Answer 25

Attains systolic pressure only as can feel when the pulse returns following occlusion i.e what the systolic pressure would be

Question 26

How does asculatory method of BP measurement work?

Answer 26

As the pressure of the cuff is reduced it will reach the point of the systolic pressure where turbulent flow will resume until the diastolic pressure is reached and the vessel is sufficiently uncompressed for smooth flow to occur i.e at diastolic pressure

Question 27

Whats the impact of gravity on blood pressure?

Answer 27

Hydrostatic pressure is influenced by gravity i.e P = (Density x 9.81 x Height)

Thus when standing pressure in a specific vessel can equal (Hydrostatic + Pressure created by heart)

Question 28

Describe the regulation effects on blood pressure over time;

Answer 28

Short term: Neural
Minutes-Hours: Hormonal and fluid shifts
Long term: Blood volume regulation