Hemodynamics and BP Flashcards
week 7
Where is blood velocity the slowest?
in arteries and capillaries
What are the 2 determinants of flow?
Pressure (P)
Difference in blood pressure between 2 points
Flows from high to low
Resistance (R)
Flow is inversely proportional
What factors contribute to vascular resistance?
Viscosity
Blood vessel length
Blood vessel radius
vasoconstriction/dilation
Describe the non-linear relationship of blood flow and resistance.
Resistance decreases as diameter increases due to less friction and more laminar flow.
The blood at vessel wall is slowest (friction) and at centre is fastest (less friction).
What is the impact of vasodilation in blood flow and velocity?
Blood flow increases (decreased resistance)
Blood velocity decreases (increased cross-sectional area)
What is the equation for BP?
BP= CO x PVR
What are the determinants of BP?
CO
PVR
Blood volume
define systolic and diastolic blood pressure respectively and their values.
Sys: peak arterial pressure after LV ejection = 120mmHg
Dia: minimum arterial pressure before next LV ejection = 80mmHg
Pulse pressure (value)
SBP-DBP
40mmHg
MAP equation
MAP = (CO x PVR) + CVP = 93.3mmHg
MAP regulation
Blood V (fluid intake/loss)
Effectivness of heart pump (Hr and SV)
Resistance (diameter of artreries)
distribution of blood between arterial and venous vessels (diameter of veins)
What are the 3 modes of regulation for BP? where do they each impact?
Autoregulation - local blood flow
Neural Regulation - first core BP then local blood flow
Endocrine regulation - either depending on source
What feeling when palpate pulse?
Reverberation or shock wave from ejected SV onto wall of aorta
Actually precedes ejection of blood
Is a reflection of successful ejection of blood from heart = successful round of systole.
What factors change pulse rates?
Loss of vessel wall characteristics
Alterations to CO
Overall poor cardiac output
The merging of two ejection-triggered reverberations waves
What happens if radial pulse < apical pulse and who does it happen in?
= pulse deficit = decrease in LV output.
Occurs in AFib, premature beats and congestive heart failure.
Why simultaneously take radial and femoral pulse?
Can be diagnostic:
They should yield nearly simultaneously pulses.
Delay = coarctation of aorta or aortic obstruction below Subclavian artery
Determining S1 in chest exam
Listen to chest and take carotid pulse
Pulse = systole (S1)
Why should you not palpate both carotid arteries simultaneously?
don’t want to interfere with adequate brain perfusion by placing pressure on both carotid arteries
- very important in the elderly!
why you should take care when palpating the carotid artery of an elderly patient?
Carotid arteries may be stiffened or have small atherosclerotic blockages.
Could risk collapse of vessel or dislodge plaque = ischaemia or stroke!
What is the Windkessel Effect?
storage of blood in aorta during systole
discharge in diastole
buffers pulsatile ejection
