Pressure and Flow in Veins Flashcards
How do you measure Korotkoff sounds?
Sphygmomanometer and stethoscope
What are the disadvantages and advantages of using a sphygmomanometer?
Discontinuous, accuracy, needs care and skill
Non-invasive and cheap
What causes Korotkoff sounds?
Turbulent blood flow
Silence above systolic and under diastolic
What sounds are heard on stethoscope?
Silence, tapping, thumping, muffled and then silence again
How does an oscillatory blood pressure measurement calculate arterial pressure?
Vibrations from turbulent blood flow are measured
Peak of vibrations at MAP
Transducer measures this
Explain ventricular contraction on aorta and arteries?
Ventricle contracts, Semilunar valve open and blood ejected from ventricle to arteries and then aorta expands so can store pressure in elastic walls
Explain ventricular relaxation on aorta and arteries?
Isovolumic ventricular relaxation, semilunar valves shut so prevents backflow of blood and then elastic recoil sends blood forward into circulatory system
How does elastic arteries act as pressure reservoir?
Damps down pressure vibrations
What is pressure wave affected by?
Stroke volume, Velocity of ejection, Elasticity of arteries and TPR
Describe pressure and flow from arteries to veins?
Pressure falls throughout vascular tree and velocity is related to total cross-sectional area
What causes small drop in pressure through arteries?
Low resistance conduit
around 95 to 90 mmHg
What causes larger drop in pressure through arterioles?
Resistance vessels
Around 90 - 40mmHg
Describe the pressure in capillaries?
Low which is good as thin walled
Describe pressure in veins?
Small pressure difference pushing blood back through veins as systemic filling pressure
From 20 - 5 mmHg
What is pulmonary circulation pressure?
1/5 th of systemic circulation pressure as need to be low