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556 - Physiology & Pathophysiology II > Exam 1 - Control Of Cardiac Output > Flashcards

Exam 1 - Control Of Cardiac Output Flashcards

1
Q

3 basic principles of blood flow

A

1 - Control of flow to local tissues depends on metabolic need
2 - VR is sum of flow from local tissues and CO is driven by VR
3 - BP is independent of control of flow through local tissue and CO

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2
Q

Baroreceptors

A
  • respond to moment to moment changes
  • respond to increase or decrease in BP fro normal MAP
    ~ all others respond to drop in MAP
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3
Q

Responds to changes in pressure over all ranges

A
  • Baroreceptors
  • Cap fluid shift
  • Stress relaxation/constriction
  • Renal BP control (long term)
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4
Q

Responds to changes when MAP drops

A
  • Chemoreceptors
  • Renin-angiotensin / aldosterone
  • CNS ischemic response
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5
Q

CO

A

CO = HR x SV

HR: autonomic innervation (para) / drugs
SV: autonomic innervation (symp) / preload / afterload

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6
Q

CO vs VR

A
  • Over time…they must be equal
  • May be different for a few beats
  • CO affected by: metabolic activity / body mass / age
  • VR determines CO
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7
Q

Frank-Starling law

A
  • SV changes based on VR

- Increased VR produces more stretch which increases SV/HR

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8
Q

Q (sum of all VR) =

A

Q = P/SVR

  • SVR changes based on metabolism…inversely proportional
    ~ only works if body maintains constant MAP
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9
Q

ANS and maintaining MAP

A
  • ANS keeps MAP constant (baroreceptors)
  • Allows CO to change based on metabolic need / SVR changes
  • Without ANS…MAP drops as SVR drops with minimal CO change
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10
Q

Peak CI

A
  • Age 8-10

- 4 to 4.5 L/min/m2

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11
Q

Affect of age on CI

A
  • metabolic activity determines CO
  • CI drops as you age due to drop in muscle mass / activity
    ~2.4 @ 80 yo
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12
Q

Average CO

A
  • 5.0 L/min
  • Male: 5.6
  • Female: 4.9
  • CI: 3.0
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13
Q

Hypereffective

A
  • Increased CO from changes in contractility and HR
  • Curve shifts UP and LEFT
  • Causes: sympathetic / hypertrophy
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14
Q

Hypoeffective

A
  • decreased CO
  • curve shifts DOWN and RIGHT
  • caused by: anything that makes the heart pump less effectively
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15
Q

RAP

A

Resting Atrial Pressure aka CVP

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16
Q

Normal ANS tone

A

Resting: RAP - 0 / CO - 5.0
Max: RAP > 4 / CO - 13.0

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17
Q

Hypereffective heart values (nervous only)

A

Max: RAP > 4 / CO - 25

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18
Q

Hypereffective heart values (hypertrophy and symp)

A
  • Mass is 50 - 75% greater

- Max: RAP > 4 / CO - 30 to 40

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19
Q

CO vs External Pressure

A
  • Intrapleural pressure usually -4 mmHg
  • Increase intrapleural pressure increases RAP
    ~ 1:1 ratio
  • Hypereffective shifts cardiac function curve up (hypo is oppo)
  • Increased intrapleural pressure shifts right (visa versa)
20
Q

Cardiac tamponade

A
  • fluid build up around heart
  • heart cannot fill properly
  • hypoeffective
  • drop in pre-load
21
Q

Factors that alter external pressure

A
  • respiration cycle
  • negative shifts left…positive shifts right
  • open thoracic cage….move to 0 mmHg…. shift curve right 4
  • cardiac tamponade
22
Q

To get VR….

A

Need pressure drop from caps to RA

23
Q

Central vs Peripheral venous compartment

A

Central: affected by intrathoracic pressure
Peripheral: not affected

VR = (peripheral venous p - CVP) / venous resistance
~ same equation as before

24
Q

Ventricle values

A

Volume: 30
Compliance: 24
Resistance: 0

25
Q

Artery values

A

Volume: 600
Compliance: 2
Resistance: 1

26
Q

Arterioles values

A

Volume: 100
Compliance: 0
Resistance: 13

27
Q

Capillary values

A

Volume: 250
Compliance: 0
Resistance: 5

28
Q

PVC values

A

Volume: 2500
Compliance: 110
Resistance: 1

29
Q

CVC values

A

Volume: 80
Compliance: 4
Resistance: 0

30
Q

Entire body values

A

Volume: 3560
Compliance: 140
Resistance: 20

R in Wood units

31
Q

Normal systemic volume

A
  • 4500 mls
  • 4500-3560 = 1000
  • 1000/140 = 7 mmHg pressure when full but no flow
32
Q

Mean systemic filling pressure

A
  • Psf
  • similar to Pmf (Mean circulatory filling pressure)
    • Pmf includes pulmonary but it has minimal effect
33
Q

Arteries vs Venous compliance

A
  • change in volume has bigger pressure change in arteries

~ arteries have lower compliance (2 vs 110)

34
Q

CVC

A
  • RA and central veins in thorax

- volume depends on VR (in) vs CO (out)

35
Q

Factors affecting VR

A
  • Pressure in PVC (usually = Psf = 7 mmHg)
  • Venous resistance: 2/3 veins and 1/3 arterioles (1.4)
  • Pressure in CVC (usually 0 mmHg)
  • VR = Psf - RA / Resistance -> 7/1.4 = 5 L/min
36
Q

Venous function curve

A
  • independent = RAP aka CVP
  • dependent = VR
  • RAP/CVP affect VR…not the other way around
37
Q

Changing Psf and venous curve

A
  • Can change Psf by adding CBV
  • increase CBV….curve shifts right
  • increase resistance….curve SLOPE drops down
    ~ up resistance….down VR
38
Q

Intersection of Cardiac and Venous curves

A
  • Shows CO / VR / CVP
39
Q

Increase in CVP on cardiac and venous curves

A
  • increase CO
  • decrease VR
  • more volume leaving CVP than coming in -> CVP drops until back to equilibrium (CO and VR are equal)
40
Q

What has to happen to get a change in CO

A
  • one or both curves have to shift
  • Cardiac shifts: Change in cardiac effectiveness (hyper/hypo)
    Change in external pressure
  • Venous shifts: Change in Psf aka CBV
    Change in venous resistance (slope)
41
Q

Effect of increasing CBV

A
  • Increases Psf
  • Distends vessels so resistance drops
  • Venous curve shifts right and slope increases
  • Kidneys will take off extra volume over time (big player)
    ~ fluid also moves to 3rd space (edema)
    ~ autoregulation constricts
    ~ fluid stored in liver and spleen
    - all these try to bring Venous curve back to normal spot
42
Q

Response to hemorrhage

A
  • Loss of volume shifts venous curve left
  • symp stimulation kicks in (cardiac curve up and left)
    ~baroreceptors / CNS ischemic / chemoreceptors / etc.
  • symp stimulation constricts veins (shifts venous curve back right a little)
43
Q

Inotropic drugs

A
  • increase cardiac curve (increases contractility)
44
Q

Vasoactive drugs

A

Changes venous curve resistance (slope)

45
Q

Diuretic drugs

A
  • shifts venous curve based on loss or gain of volume

556 - Physiology & Pathophysiology II (8 decks)

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