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CPR Exam 1 > 15. Hemodynamics & Systemic Circulation > Flashcards

15. Hemodynamics & Systemic Circulation Flashcards

1
Q

what is the pressure in the As after the aorta

A

highest

= stressed volume

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2
Q

what is the pressure in arterioles compared to As

A

moderate P

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3
Q

where in the circulatory system can you change resistance to control flow

A

arterioles

Sm M contract to control flow by changing resistance

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4
Q

what determines ther degree of perfusion in capillaries

A

constriction/dilation of arterioles

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5
Q

what is the P in venules

A

low P

(large vol)

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6
Q

how can venules control BP

A

contract to move more blood to arteries to increase BP

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7
Q

what are characteristics of Vs

A

large capacitance

low P, large vol = unstressed vol

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8
Q

what are characterisitccs of capillaries

A

lare cross-sectional area

single endothelial lining

nutrient/waste/gas exchange

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9
Q

what area of circulation has to largest area

A

capillaries

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10
Q

where is blood volume least

A

aorta/As/arterioles

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11
Q

relative to the parts of circulation, what is the area and BV of the Vs

A

large A (but smaller than capillaries)

large BV

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12
Q

how does area contribute to velocity of blood flow

A

inverse relationship (increase A –> decrease velocity)

V = Q/A

(calculated single vessel or total summed cross sectional A of parallel circuits)

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13
Q

compare the velocity of the aorta & capillaries

A

aorta - high velocity ( bc small area)

capillaries - low velocity ( bc large crossectional A)

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14
Q

what is the flow from aorta to systems

A

flow is consistent, however the flow is divided btn the systemsl like ….

cerebral = 15%, coronary = 5 %, etc

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15
Q

how does flow change throughout the system

A

the percent division btn systems change based on hormones/activity

like… exercise - more blood sent to MSK than GI

*- based on arteriole resistance*

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16
Q

how does pressure gradient and resistance contribute to flow

A

flow (Q) = pressure gradient/R

pressure gradient directly related to flow

R inversely related to flow

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17
Q

how do you calculate cardiac output with pressure and resistance

A

=(arterial pressure - venous pressure) / total peripheral resistance

(=pressure gradient/R)

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18
Q

how is Resistance calculated

A

change R w/

  1. viscosity - direct relationship
  2. length of vessel - direct relationship
  3. * vessel radius * = most significant & inverse relationship
19
Q

how is vessel radius controlled & what is the purpose

A

hormones or local factors

change resistance to regulate BP and match blood flow to metabolic needs

20
Q

how do you calculate vascular resistance for vessels in series

A

add the resistances

(longer the tube - more resistance)

21
Q

how do you calculate vascular resistance for vessels in parallel

A

1/R(total) = 1/R1 + 1/R2 + etc

total resistance decrease

22
Q

when does laminar flow change to turbulent flow

A

high velocity

large cross sectional area

heavy density or

low viscosity

>2000 Reynolds number (=transition)

23
Q

how does you calculate reynolds number

A

increases w/ density, diameter, velocity

decrease with viscosity

24
Q

what can turbulent flow lead to

A

sound (bruits)

lesion (arteriosclerosis)

25
Q

what is laminar flow

A

high velocity in middle &

zero on the walls (bc increased viscosity on walls)

ideally = parabolic

26
Q

what is complaince

A

how easy it is for a vessel to expand (–> holds more volume)

change in vol/change in pressure

27
Q

what has a larger compliance Vs or As

A

Vs

easiest to stretch –> so hold larger volume at lower pressure

28
Q

what is the compliance for As

A

low

harder to expand –> so need larger P to hold low volumes

29
Q

what happens to compliance when Sm. M of Vs contract

A

decrease compliance –> decrease volume (shift volume from V to A)

so in A increase P and volume

30
Q

what happens to complaince with aging As

A

walls get stiffer –> decrease compliance

so you need higher Ps to hold same amount of volume

31
Q

why do you have pulsatile pressure in aorta

A

compliance and distension during ejection and recoild during diastole

-lost by arterioles

32
Q

what is the pulse pressure dependent on

A

atrial compliance

33
Q

why is the pulsitile pressure higher in the large As compared to the aorta

A

echo effect

-waves bouncing back fron small As and arterioles

34
Q

where is pulsatile pressure lost

A

arterioles

35
Q

what happens to P in the arterioles

A

huge decrease bc high resistance to flow

at end around 30 mm HG

36
Q

how is systolic pressure and diastolic pressure reported clinically

A

systolic = greatest P in large A

diastolic = lowest P in large A

37
Q

why is mean pressure closer to diastolic P

A

spend more time in diastole than systole

= diastolic + 1/3*pulse

38
Q

how do you calculated pulse pressure

A

systolic - diastolic

39
Q

what happens if you have a decrease in compliance of arterials

A

increase pulse P

-increased systolic P & diastolic stays same (but could decrease)

40
Q

what happens to pulse P in arteriosclerosis

A

decrease compliance

increase pulse P

41
Q

what happens to pulse P in aortic stenosis

A

decrease pulse pressure bc decreased SV

42
Q

what happens to the pulse pressure (and its graph) if R is increased

A

shift the entire graph up

*no change in shape*

43
Q

What is the clinical significance of an increased left atrial pressure?

A

indicative of heart failure or decreased left ventricular output

44
Q

What is the pulmonary wedge pressure directly proportional to?

A

left atrial pressure

CPR Exam 1 (27 decks)

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