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SMP - Cardiopulmonary Exam 1 > Lecture 6 - Overview of Cardiovascular Physiology > Flashcards

Lecture 6 - Overview of Cardiovascular Physiology Flashcards

1
Q

Other than bringing oxygen and nutrients to tissues and taking away wastes, what are some other functions of the CV system?

A
  1. Endocrine signaling
  2. Thermoregulation
  3. Facilitate the immune response
  4. Hemostasis
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2
Q

What is hemostasis?

A

Process which causes bleeding to stop

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3
Q

What are the 3 major parameters to measure CV function?

A
  1. Pressure
  2. Flow
  3. Resistance
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4
Q

2 possible units for blood pressure?

A

mmHg (or Torr) and cmH2O

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5
Q

What is blood pressure?

A

Measure of the force exerted by blood per unit area on vessel walls

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6
Q

Which pressure are we the most interested in clinically?

A

Arterial BP

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7
Q

How is arterial BP expressed?

A

Systolic P/diastolic P

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8
Q

What is the mean arterial pressure?

A

Arterial pressure integrated over the course of one cardiac cycle of systole and diastole

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9
Q

How to approximate the mean arterial pressure at a normal heart rate?

A

MAP = diastolic P + 1/3 pulse pressure

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10
Q

Systole?

A

Period of cardiac contraction and ejection

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11
Q

Diastole?

A

Period of cardiac relaxation and filling

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12
Q

Normal BP for an adult?

A

120/80

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13
Q

Why is MAP not the average of systolic and diastolic pressures?

A

Because diastole lasts a little longer than systole in the cardiac cycle

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14
Q

Systolic pressure?

A

Highest arterial BP observed when the heart is ejecting blood

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15
Q

Diastolic pressure?

A

Lowest arterial BP observed when the heart is filling up with blood

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16
Q

Pulse pressure?

A

Systolic P - Diastolic P

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17
Q

What is blood flow?

A

BV passing through a portion of the circulation per unit time (Q)

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18
Q

Blood flow 2 units?

A

mL/min or L/min

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19
Q

What equation relates flow, pressure, and resistance? Analogy to this equation?

A

Q = ΔP/R

Analogy: Ohm’s Law = I = V/R

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20
Q

Most important cardiac flow rate?

A

Cardiac output

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21
Q

What is cardiac output?

A

Flow rate from 1 ventricle

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22
Q

Equation to calculate cardiac output?

A

CO = HR x SV

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23
Q

Normal CO value?

A

5L/min

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24
Q

What is the stroke volume?

A

Volume ejected by 1 ventricle in 1 beat

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25
Q

Normal SV for a 170 lb person?

A

70 mL

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26
Q

What is the cardiac index (CI)?

A

CO normalized for body surface area

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27
Q

Formula for CI?

A

CI = CO / m^2

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28
Q

CI for 170 lb person?

A

CI = 5/1.5 = 3.3 L/min/m^2

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29
Q

What is the stroke index (SI)?

A

SV normalized for body surface area

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30
Q

Formula for SI?

A

SI = SV/ m^2

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31
Q

What is blood velocity?

A

Speed at which blood flows

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32
Q

What is another word for resistance?

A

Impedance

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33
Q

What is the unit of resistance?

A

mmHg/mL/min

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34
Q

Unit of resistance of the systemic circulation?

A

PRU = peripheral resistance units

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35
Q

Normal resistance of the systemic circulation?

A

0.02 PRU

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36
Q

How do valves work?

A

They passively respond to pressure gradients

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37
Q

Unit of blood velocity?

A

cm/s

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38
Q

What is resistance to blood flow a property of?

A

Fluid AND vessel

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39
Q

Is ALL of the blood in the ventricles ejected with contraction?

A

NOPE

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40
Q

What is the end diastolic volume (EDV)?

A

Amount of blood in ventricle following atrial contraction during diastole

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41
Q

What is the end systolic volume (ESV)?

A

Residual amount of blood in ventricle following ventricular contraction during systole

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42
Q

What is the ejection fraction?

A

Proportion of end diastolic volume ejected during systole

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43
Q

Equation for ejection fraction?

A

Ejection fraction = SV/EDV

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44
Q

Equation for end diastolic volume?

A

EDV = SV + ESV

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45
Q

Describe the timing of the electrical and mechanical events taking place in the heart?

A

Electrical events precede and initiate the mechanical ones

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46
Q

What is the blood transit time?

A

Average time for a particle of blood to pass from one point to the another in the circulation

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47
Q

Is the CO of the RV = to the CO of the LV?

A

YESSS

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48
Q

Describe the pressure and resistance of the systemic circulation.

A

High pressure

High resistance

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49
Q

Describe the pressure and resistance of the pulmonary circulation.

A

Low pressure

Low resistance

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50
Q

Is the overall circulatory pathway a circuit in parallel or in series? What does this mean?

A

Series

CO = venous return

51
Q

Is regional circulation in parallel or in series? What does this mean?

A

Parallel

Individual organs can adjust their flow individually via dilation/constriction of the arterioles

52
Q

% of cardiac output going to the brain? VO2?

A

13%

VO2: = 21%

53
Q

% of cardiac output going to the coronary circulation? VO2?

A

4%

VO2 = 11%

54
Q

% of cardiac output going to the liver and GIT? VO2?

A

24%

VO2 = 23%

55
Q

% of cardiac output going to skeletal muscles? VO2?

A

21%

VO2 = 27%

56
Q

% of cardiac output going to the kidneys? VO2?

A

20%

VO2 = 7%

57
Q

% of cardiac output going to the skin and other organs? VO2?

A

18%

VO2 = 11%

58
Q

Why is the venous system sometimes called the capacitance system?

A

Because it can function as a reservoir for blood, i.e. if you lose blood or if the flow rate increases (e.g. during exercise), sympathetic NS will contract veins to release blood to make up for it to maintain BP homeostasis

59
Q

What % of the blood is found in the venous system?

A

64%

60
Q

What vessels account for most of the resistance of the CV system?

A
  1. Small arteries/arterioles: 47%
  2. Capillaries: 27%
  3. Large arteries: 19%
  4. Veins: 7%
61
Q

Breakdown % of blood in systemic vs pulmonary circulation? How is this possible if CO of RV = CO of LV?

A

Systemic circulation => 90% of the blood
Pulmonary circulation => 10% of the blood

Possible because the pulmonary circulation is low pressure and resistance

62
Q

Which CV vessels regulate blood flood to specific regional circuits? How?

A

Arterioles by dilating or constricting to decrease or increase resistance

63
Q

Pulmonary arterial pressure?

A

25/10 mmHg

64
Q

Pulmonary MAP?

A

15 mmHG

65
Q

Where is the largest pulse pressure found in the CV system? What is it? Why?

A

LV: 120

Required to pump blood into the aorta and setting up the pressure gradient for flow through the systemic circulation

66
Q

Which vessels make up the distributing system?

A

Arteries

67
Q

Which vessels make up the collecting system?

A

Veins

68
Q

Which vessels make up the exchange system?

A

Capillaries

69
Q

% of cardiac output going to the lungs?

A

100%

70
Q

Pressure higher in atria or ventricles?

A

Ventricles

71
Q

Diastolic P in LV? Why?

A

0 mmHg

To allow LV to fill up

72
Q

How is systemic arterial pressure commonly measured?

A

Indirectly via a BP pressure cuff, a sphygomomanometer:

Cuff applies a pressure of around 180 mmHg until flow is stopped in the arm (no more sound), then pressure is slowly released until sound is heard like a beat, demonstrating intermittent flow = systolic pressure. Then, no more sound will be heard once the flow is constant = diastolic pressure

73
Q

How are arterial and venous pressures directly measured?

A

Direct catheterization

74
Q

What vessels/heart compartments can be measured by direct catheterization and advancing it in retrograde direction?

A

Arteries, aorta, and LV

75
Q

What vessels/heart compartments can be measured by direct catheterization and advancing it in anterograde direction?

A

Veins, RA, RV, and pulmonary arteries

76
Q

Is it possible to measure pulmonary venous and LA pressures by direct catheterization?

A

NOPE

77
Q

How are pulmonary veins and LA pressures measured?

A

Indirect measurement of pulmonary capillary wedge pressure

78
Q

Which vessels/heart compartment cannot be measured via direct catheterization?

A

Pulmonary veins and LA

79
Q

Where is the lowest pulse pressure found in the CV system? What is it?

A

RV

20 mmHg

80
Q

Normal venous pressure?

A

2-6 mmHg

81
Q

What is another name for a pulmonary artery catheter?

A

Swan-Ganz catheter

82
Q

When is a pulmonary artery catheter used to measure wedge pressure?

A

For heart patients, for example during heart failure

83
Q

Where is a pulmonary artery catheter first introduced?

A

A large vein

84
Q

What pressures can a pulmonary artery catheter measure? What else?

A

Veins, RA, RV, PA, PV/LA (wedge pressure), and filled LV + CO

85
Q

What are the 5 tubes contained in a pulmonary catheter? What do we call this? What else does the catheter include?

A
  1. Thermistor
  2. Balloon port
  3. Filament
  4. PA distal
  5. Infusion port

=> multi-lumen smooth catheter (each tube ends at different places)

+ Balloon on the outside of the catheter at its tip

86
Q

Describe the steps to measure pulmonary artery pressure using a pulmonary artery catheter.

A
  1. Advance catheter to RV
  2. Slightly inflate balloon to help utilize blood flow to gain entry into the pulmonary artery (like a sail) and advance it as far as you can (2nd or 3rd generation branch of pulmonary artery)
  3. Fully inflate balloon until flow in the artery is blocked
  4. This will cause the pressure beyond the catheter tip to fall and equilibriate with the downstream pressure = capillary wedge pressure = pressure of pulmonary veins and LA
87
Q

When using a pulmonary catheter, how can one tell at which location it is?

A

The pressure at the tip reflects its location

88
Q

PA normal pressure?

A

25/10 mm

89
Q

How would the LA pressure be affected if the LV is failing to pump blood?

A

Would be elevated

90
Q

During diastole, what pressures equilibriate?

A

Those in the ventricles, atria, and large vessels feeding into the atria

91
Q

When using a pulmonary arterial catheter, does the balloon inflation affect the patency of the lumen through which pressure is measured?

A

NOPE

92
Q

What is another name for wedge pressure measurement?

A

Hemodynamic assessment

93
Q

For how long are pulmonary catheters usually left in the patient?

A

Couple days with balloon NOT inflated (inflate periodically)

94
Q

Normal RA pressure?

A

9/4 mmHg

95
Q

Normal LA pressure (wedge)?

A

12/5 mmHg

96
Q

Normal RV end-diastolic pressure?

A

< 6 mmHg

97
Q

Normal LV end-diastolic pressure?

A

< 12 mmHg

98
Q

How is cardiac output measured?

A
  1. With a pulmonary arterial catheter in the pulmonary artery using an indicator dilution technique
  2. By employing Fick’s principle
99
Q

Is CO in pulmonary artery = CO in aorta?

A

YUP

100
Q

What is the curve duration when using the indicator-dilution method?

A

Time from injection until concentration has reached 0 (will need to be extrapolated)

101
Q

What is the actual equation to measure CO using the indicator-dilution technique?

A

I/C.T

I = mass of indicator injected
C = mean dye concentration 
T = duration of 1st circulation
102
Q

Other 2 names for curve duration when using the indicator-dilution method?

A

Duration of 1st circulation = duration of primary curve

103
Q

Describe the indicator dilution technique to measure CO.

A
  1. Indicator dye is injected into the RV
  2. Serial measurements of concentration are made in the pulmonary artery
  3. Average indicator concentration and the duration of the first-circulation curve are used to calculate PA flow = CO
104
Q

How will the concentration of dye in the PA fluctuate during the indicator-dilution method to measure CO?

A

Starts at 0 => reaches maximum => goes back down to a minimum => goes back up again because of recirculation

105
Q

Describe the thermal dilution technique to measure CO.

A
  1. Cold or room temperature saline is injected into the RV
  2. Serial measurements of temperature are made in the pulmonary artery
  3. Temperature deflection and the duration of the first-circulation curve are used to calculate PA flow = CO
106
Q

What is the Fick principle?

A

Amount of substance added or removed to or from an organ = blood flow x (a-v)

(a-v) = difference in concentration across the organ between arteries and veins

107
Q

How is Fick’s principle used to calculate CO?

A

CO = blood flow across the lungs = amount of oxygen consumed (mL/min) / (a-v)O2

a = systemic arterial oxygen concentration (sampled from any artery) 
v = pulmonary arterial oxygen concentration
108
Q

Why is pulmonary arterial O2 concentration used in CO measurement using the Fick principle instead of the venous O2 concentration?

A

Because complete mixing of venous blood from various systemic regional circulations might not be accomplished until that point in the circulation

109
Q

5 other techniques used to measure blood flow?

A
  1. Plethysmography
  2. Doppler flow meter
  3. Electromagnetic flow
  4. Echocardiography
  5. fMRI
110
Q

Do all circulatory pathways have the same transit time through the entire systemic circulation?

A

NOPE

111
Q

How to use the indicator dilution technique when all you have is the curve produced?

A

CO = amount of indicator added / area under first circulation curve

112
Q

What is 1 mmHg?

A

The pressure generated by elevating a column of mercury by 1 millimeter

113
Q

What is VO2 a measure of?

A

Oxygen utilization

114
Q

Normal RV pressure?

A

25/0 mmHg

115
Q

Normal LV pressure?

A

120/0 mmHg

116
Q

What would a continuous murmur in the second left intercostal space adjacent to the sternum mean? How would this affect CO?

A

Murmur near trunk of the pulmonary artery => patent ductus arteriosus so blood is being mixed between the aorta and the pulmonary artery causing the CO to appear to be higher when calculating CO with Fick’s principle because (a-v) will be lower

117
Q

When using a pulmonary arterial catheter, does the the balloon inflation affect the patency of the lumen through which pressure is measured? Explain.

A

The balloon is around the outside the catheter, which isn’t weak enough to be collapsed by that balloon. Imagine a blood pressure cuff that is inflated, but still letting blood pass beneath it.

118
Q

When are the pressures in the pulmonary vein, LA and LV very close?

A

Toward the end of diastole

119
Q

Units for O2 consumption?

A

mL O2/min

120
Q

What is pulse pressure a function of? What are the most important determinants in a healthy individual?

A
  1. Stroke volume***
  2. TPR***
  3. Aortic distensibility
  4. Heart rate
  5. Ejection velocity
121
Q

Which part of the pulmonary circuit has the highest pulse pressure?

A

RV

122
Q

What other pressures is the RV diastolic pressure equal to?

A

CVP = RA diastolic

123
Q

What other pressures is the LV diastolic pressure equal to?

A

LA diastolic = PAP diastolic

124
Q

What is pulse pressure a surrogate for?

A

SV

SMP - Cardiopulmonary Exam 1 (28 decks)

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