Blood Pressure: Distribution & Dissipation Flashcards
veins
resistance makes blood pressure drop
flow
Elastic properties of arteries helps maintain blood flow
from veins > arteries> arterioles> capillaries
Measuring blood pressure (arterial)
Blood pressure can be measured indirectly using a sphygmomanometer
– Inflatable cuff with pressure gauge
– Cuff compresses brachial artery
– Measures systolic and diastolic pressure
Sphygmomanometry – principles
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)
Sphygmomanometry -
No Flow
Cuff is inflated
Cuff pressure > arterial pressure
Artery is completely occluded No sound as no flow
Sphygmomanometry -
Turbulent flow:
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)
Sphygmomanometry - Laminar Flow
Laminar Flow
No sound heard when cuff pressure < diastolic pressure
Last sound heard is at diastolic pressure
Other measures of pressure
Pulse Pressure
Difference between systolic and diastolic pressure
Eg 120 – 80 = 40 mmHg
relates to stoke volume higher stroke volume = higher pulse pressure
Other measures of pressure
- Mean Arterial Pressure
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
Important!
The body uses mean arterial pressure to regulate blood pressure, not systolic or diastolic pressur