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Hemodynamics Flashcards

1
Q

systole

A

blood into atria

contraction

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2
Q

diastole

A

blood into ventricles

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3
Q

arteries - flow, pump, compressibility

A

pulsatile flow
heart is pump
non-compressible

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4
Q

veins- flow, pump, compressibility

A

less pulsatile, phasic
leg contractions is pump
compressible

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5
Q

where are there valves

A

heart and veins

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6
Q

regurgitation

A

when the valves dont close enough

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7
Q

venous hemodynamic factors (2)

A

hydrostatic pressure

respiration

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8
Q

hydrostatic pressure - how does it change?

pressure supine vs standing

A

increases with increasing distance below heart
supine- 0 mmHg
standing- 100 mmHg

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9
Q

Describe how thoracic and abdominal volume (and pressure) changes with inspiration. What happens to venous return?

A

inspiration
increased thoracic volume, decreased pressure
decreased abdo volume, increased pressure
STOPS venous return

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10
Q

Describe how thoracic and abdominal volume (and pressure) changes with expiration. What happens to venous return?

A

expiration
decreased thoracic volume, increased pressure
increased abdo volume, decreased pressure
venous blood RETURNS from legs

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11
Q

what is valsalva and what does it do?

A

breath hold

increases abdo pressure, STOPS venous return

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12
Q

fluid

A

liquid or gas

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13
Q

driving force behind fluid flow

A

pressure, low to high

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14
Q

pressure formula

A

P = force/area

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15
Q

volumetric flow rate - what is it and whats the unit

A

volume of blood passing a point per unit time
applies to LONG STRAIGHT TUBE
mL/s

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16
Q

volumetric flow rate (Q) basic formula

A

Q = pressure/resistance (in vessel)

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17
Q

Resistance of a long straight tube depends on

A

tube length
viscosity
radius

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18
Q

poise

A

viscosity and resistance

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19
Q

If tube LENGTH increases what happens to flow RESISTANCE

A

length and resistance proportionate related

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20
Q

if tube RADIUS increases what happens to flow RESISTANCE

A

radius and resistance inversely related (to the power of 4!)

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21
Q

if VISCOSITY increases what happens to flow RESISTANCE

A

viscosity and resistance proportionately related

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22
Q

poise is what units

A

1 gram per cm^4-s

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23
Q

how much more viscious is plasma than water

A

50%

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24
Q

viscosity normal blood is what times that of water

A

5 times

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25
what happens to flow rate if you increase resistance
Q and R are inversely related so decreases
26
How does resistance depend on radius? If radius doubles, what happens to resistance?
Resistance depends on radius to the 4th power | radius doubles, resistance decreases X16 (2^4)
27
how does vasodilation and vasoconstriction change flow resistance
vasodilation- decreases resistance | vasoconstriction- increases resistance
28
When do you use the poiseuille equation?
when resistance is not known
29
what happens to flow rate if you decrease diameter (according to poiseuille's law)
flow rate decreases
30
what happens to flow rate if you increase length
flow rate decreases (because resistance increases)
31
volumetric flow rate in a tube depends on
pressure difference length of tube diameter of tube viscoscity of fluid
32
what are the two types of flow
laminar and turbulent
33
what is laminar flow
flow in which layers of fluid slide over eachother in straight lines
34
types of laminar flow (3)
plug flow parabolic flow disturbed flow
35
Flow is seen at a stenosis or bifurcation
Disturbed flow
36
Plug flow
Flow seen at the entrance to tubes where the same speed is seen across the vessel
37
The fastest speed seen in parabolic flow? the slowest? what is the average flow speed?
fastest= centre slowest= tube walls average flow speed is 1/2 the fastest speed
38
Type of flow seen after significant stenosis
Turbulent flow
39
Flow where you'll hear bruit
Turbulent
40
Characterizing factor for turbulent flow
critical reynolds number, 2000 for blood
41
Factors affecting reynolds number
``` density (p) velocity diameter ------------- viscosity ```
42
stenosis vs occulsion
partial vs complete blockage
43
what is pulsatile flow
non-steady, acceleration and deceleration over cardiac cycle
44
true or false - venous circulation is such that pressures, flow speed and patterns do not change over time
true
45
with pulsatile flow, blood flow speed/pressure changes. this depends on (3)
impedence intertia compliance
46
what are two things observed in compliant vessels with pulsatile flow
windkessel effect | flow reversal
47
what is the windkessel effect
observed in compliant vessels where systole = vessel expands and volume increases distole = pressure decreases, compliant vessel contracts producing extended flow without driving pressure from the heart
48
true or false - blood stops flowing during diastole
false
49
what causes flow reversal and where is it seen
reversal of flow because decreased pressure and vessel contraction without valves to prevent back flow. Not seen in the aorta because of valves
50
what is the continuity rule
the volumetric flow rate is constant
51
the continuity rule only applies under what conditions
a short segment, usually a stenosis or narrowing of lumen
52
FORMULA for volumetric flow rate (continuity rule)
Q= velocity X area
53
what happens if you decrease the area x2
speed increases X2 to maintain constant flow
54
how does poiseuilles law contradict the continuity rule
- poiseuille's law suggests that flow speed decreases with smaller diameters - continuity rule suggests flow speed increases with smaller diameters two situations are different because poiseuilles law = entire vessel, continuity rule is the diameter of a short portion (stenosis)
55
If the AREA of a stenosis is 1/2 the distal vessel what happens to flow speed?
flow speed doubles
56
if the DIAMETER of a stenosis is 1/2 the distal vessel what happens to flow speed?
flow speed quadrouples
57
When does flow rate and distal pressure drop significantly with a stenosis?
beyond a diameter reduction of 50% (area reduction 75%)
58
if you hear a bruit sound what has likely happened?
stenosis due to turbulence distal to stenosis
59
velocity at a stenosis can tell us what
how much it's stenosed
60
what is the Bernoulli effect
a decrease in pressure in regions of high flow speed (velocity and pressure are inversely related) therefore low pressure at the stenosis because high velocity
61
what are the conditions of an aneurysm?
there is a decrease in speed at the widening, causing increased pressure

Physics (9 decks)

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