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VET 408: Cardio/Respiratory > Hemodynamics > Flashcards

Hemodynamics Flashcards

1
Q

hemodynamics

A

blood movement; the study of blood flow in the circulation

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2
Q

what kind of reservoir are systemic veins

A

volume reservoir

high compliance to expand and contract to meet demands

contraction of veins pushes blood towards heart –> increases venous return

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3
Q

what kind of reservoir are systemic arteries

A

pressure reservoir

low compliance –> greatest point of flow

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4
Q

what type of vessels are the major regulator of vascular resistance

A

arterioles

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5
Q

what is blood flow

A

the displacement of volume of blood per unit time

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6
Q

what does it mean that blood flow is parabolic

A

fluid molecules on the outside move slower than those on the inside

outside molecules have friction with the vessels wall (slow)

inside molecules “slip” against the other fluid layers (fast)

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7
Q

ohm’s law

A

pressure gradient = blood flow x resistance

deltaP = Q x R

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8
Q

what are the two factors affecting blood flow (according to ohm’s law)

A

pressure difference and vascular resistance

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9
Q

pressure difference & blood flow relationship

A

increase deltaP = increase blood flow

blood flows from high to low pressure –> greater pressure difference = stronger gradient –> faster flow

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10
Q

can you change the pressure gradient in order to alter blood flow

A

NO - pressure gradients stay constant at a particular location

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11
Q

what can you change to alter blood flow

A

resistance

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12
Q

vascular resistance

A

friction of blood as it passes along the endothelium

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13
Q

how does resistance affect flow

A

increase R = decrease flow

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14
Q

poiseuille’s law

A

predicts blood flow based on the radius of the vessel

Q = (deltaP x pi x r^4) / (8 x n x L)

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15
Q

how does radius affect flow

A

increase radius (vasodilation) = decrease resistance = increase flow

decrease radius (vasoconstriction) = increase resistance = decrease flow

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16
Q

viscosity

A

“slipperiness” of blood vessels

lower viscosity = more slippery = sharper parabola (faster central flow)

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17
Q

how does viscosity affect flow

A

increase viscosity = decrease flow

decrease viscosity = increase flow

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18
Q

how does length of the vessel affect flow

A

blood flow slows along the length of the vessel due to friction

increase length = decrease flow

decrease length = increase flow

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19
Q

Reynold’s number

A

measures the point at which blood flow increases beyond laminar flow and becomes turbulent (critical velocity)

20
Q

critical velocity

A

the speed at which blood flow transitions from laminar to turbulent

21
Q

aortic pressure

A

the potential energy available to move blood

22
Q

how does aortic pressure change across arteries

A

minimal change from aorta –> arteries

increase pressure from arteries –> arterioles (high resistance vessels)

23
Q

mean arterial pressure

A

average pressure in the arteries during the cardiac cycle

24
Q

MAP equations

A

MAP - CVP = CO x SVR
(CVP is negligible)

MAP = CO x SVR
MAP = (SBP + 2xDBP) / 3

25
Q

modified Bernoulli’s equation

A

estimates pressure gradients using velocity of blood across a narrowed region

deltaP = 4 x V^2

26
Q

how does velocity affect pressure gradient

A

narrow vessels = increased velocity = increased pressure difference

wide vessels = decreased velocity = decreased pressure difference

27
Q

how does Bernoulli’s equation apply to stenotic valves

A

aortic stenosis –> left ventricular pressure becomes significantly INCREASED compared to the pressure within the aorta (on other side of stenotic valve) –> increased velocity –> increased pressure gradient

28
Q

windkessel effect

A

recoil of the aortic wall during diastole to release blood that was stored during diastole

allows perfusion to maintain throughout diastole

29
Q

pulse pressure

A

palpable pulse; the difference between systolic and diastolic blood pressure

30
Q

hyperdynamic pulses

A

bounding

occurs with increased difference between systolic and diastolic BP
(increased systolic or decreased diastolic or both)

ex. aortic regurgitation

31
Q

hypodynamic pulses

A

weak/thready

occurs when decreased difference between systolic and diastolic BP (decreased systolic or increased diastolic or both)

ex. aortic stenosis

32
Q

what is pulse pressure influenced by

A

heart rate and stroke volume

33
Q

perfusion pressure

A

blood flow directed to perfuse organs

ALL organs receive the same perfusion pressure

34
Q

how do organs alter local blood flow based on needs (since perfusion pressure is the same to all organs)

A

changing local arteriole diameter

allows organs to maintain steady blood flow despite changes in systemic BP

35
Q

auto regulation of local blood flow

A

local response to changes in systemic perfusion pressure by changing local vascular resistance

occurs within a range of systemic BPs

36
Q

systemic vascular resistance (SVR)

A

total peripheral resistance; the net resistance of entire systemic circulation

37
Q

what are surrogate measures of SVR

A

blood pressure/MAP

38
Q

vessels arranged in series

A

vessels arranged one after the other

total resistance = R(1) + R(2) + … etc

39
Q

vessels arranged in parallel

A

vessels arranged as parallel branches

1/total resistance - 1/R1 + 1/R2 + … etc

40
Q

which vessel arrangement reduces total resistance

A

parallel

41
Q

how does resistance change as blood moves from arteriole to capillary

A

small radius so you would EXPECT resistance to increase as blood moves from arteriole –> capillary

BUT

capillaries are arranged in parallel so resistance decreases from arteriole –> capillary

42
Q

arteriole function

A

gate keepers - largely control flow to specific tissues by changing vascular resistance

43
Q

pulmonary vascular resistance

A

1/10 systemic vascular resistance

able to accommodate increases in flow from increased CO to lungs and pressure by recruitment and distention of capillaries

44
Q

capillary recruitment

A

opening of additional capillaries to accommodate increased flow

45
Q

capillary distension

A

widening of capillary walls to accommodate increased flow

VET 408: Cardio/Respiratory (38 decks)

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