Blood Pressure: Distribution & Dissipation

Question 1

veins

Answer 1

resistance makes blood pressure drop

Question 2

flow

Answer 2

Elastic properties of arteries helps maintain blood flow

from veins > arteries> arterioles> capillaries

Question 3

Measuring blood pressure (arterial)

Answer 3

Blood pressure can be measured indirectly using a sphygmomanometer
– Inflatable cuff with pressure gauge
– Cuff compresses brachial artery
– Measures systolic and diastolic pressure

Question 4

Sphygmomanometry – principles

Answer 4

Sound can not be heard when:
No blood is flowing (occluded artery) or
Blood is flowing smoothly (‘laminar’ flow)
Sound can be heard when:
Blood flow is turbulent (partially occluded artery)

Question 5

Sphygmomanometry -

No Flow

Answer 5

Cuff is inflated
Cuff pressure > arterial pressure
Artery is completely occluded No sound as no flow

Question 6

Sphygmomanometry -

Turbulent flow:

Answer 6

Cuff Pressure reduced until first sound is heard
Systolic pressure!
Blood passes through turbulently when arterial pressure transiently exceeds cuff pressure (ie with each pulse)

Question 7

Sphygmomanometry - Laminar Flow

Answer 7

Laminar Flow
No sound heard when cuff pressure < diastolic pressure
Last sound heard is at diastolic pressure

Question 8

Other measures of pressure

Pulse Pressure

Answer 8

Difference between systolic and diastolic pressure
Eg 120 – 80 = 40 mmHg
relates to stoke volume higher stroke volume = higher pulse pressure

Question 9

Other measures of pressure

- Mean Arterial Pressure

Answer 9

Average blood pressure in the arteries
Closer to diastolic pressure, because heart spends longer in diastole

Mean arterial pressure = diastolic pressure + 1/3 pulse pressure
Healthy individual (120/80):
80 mmHg + (1/3) 40 = 93 mmHg

Question 10

Important!

Answer 10

The body uses mean arterial pressure to regulate blood pressure, not systolic or diastolic pressur