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Term 2 > Vascular (hemodynamics) > Flashcards

Vascular (hemodynamics) Flashcards

1
Q

Hemodynamics of Occlusive Disease

A

-abnormalities that can occur in the presence of vascular obstruction

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2
Q

Are hemodynamics the same for arterial and venous circulation?

A

No.

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3
Q

Are arterial and venous walls constructed the same?

A

No.

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4
Q

Arterial Walls

A
  • thicker tunica media than veins
  • greater elasticity
  • non collapsable
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5
Q

Do arteries have valves?

A

No.

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6
Q

What are the pressure systems of arteries vs. veins?

A

Arterial System- high pressure system

Venous System- low pressure system

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7
Q

Do veins have valves?

A

Yes.

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8
Q

How come when you take blood from a vein, blood does not gush out?

A
  • veins have blood under less pressure

- thinner walls

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9
Q

Valves

A
  • prevent back flow during diastole
  • wider diameter
  • helps blood get back to heart
  • storage for blood
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10
Q

Is it possible to return blood as quickly as it leaves the heart?

A

No.

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11
Q

What happens to venous valves during systole?

A
  • momentum forces valves open

- valves close when momentum decreases

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12
Q

What moves blood forward into the Rt atrium?

A

-decrease in thoracic pressure

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13
Q

Does the brain have a low or high resistance vascular bed?

A

-low

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14
Q

Where are there more venous valves? (prox. or dist.)

A

-distal

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15
Q

Pumps in Circulation

A
  • heart (primary)
  • aortic pump
  • muscular venous pump
  • respiratory pump
  • gravity
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16
Q

What does the pumping of the heart mostly affect?

A

-arterial system

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17
Q

Partial Vacuum

A
  • in Rt atrium during Rt ventricular filling phase

- sucks venous blood flow from IVC to Rt atrium

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18
Q

How do the aorta and other elastic arteries store energy?

A

-stretch during each systole

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19
Q

The AO acts as a _____ pump.

A

-subsidiary

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20
Q

Pressure in Venules

A

16 mmHg

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21
Q

Pressure in Great Veins (near heart)

A

4 mmHg

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22
Q

What does the muscular venous pump do?

A

-squeezes the veins and propels blood forward (toward the heart)

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23
Q

What assists the muscular pump?

A

-venous valves (one way)

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24
Q

What does the respiratory pump do?

A

-venous return to the heart

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25
Q

What happens with diaphragm motion?

A

-variations in thoracic and abd pressure

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26
Q

Is thoracic pressure lower or higher than atmospheric pressure?

A

-lower

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27
Q

What happens to abd and thoracic pressure during inspiration?

A
  • increase in abd pressure (reduced flow in abd)

- decrease in thoracic pressure (increased venous flow in chest)

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28
Q

Alveoli

A
  • tiny air sacs (1 cell thick)
  • in lungs
  • at ends of smallest airways
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29
Q

What do alveoli exchange?

A

-oxygen and carbon dioxide

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30
Q

How many alveoli absorb oxygen from air?

A

300 mil

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31
Q

What is in close contact with the alveoli?

A

-PA’s and PV’s

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32
Q

What kind of blood do PA’s carry?

A

-deoxygenated

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33
Q

What are the PA’s branches of?

A

-pulmonary trunk (off Rt ventricle)

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34
Q

Where do the PV’s carry oxygenated blood?

A

-from lungs to Lt atrium

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35
Q

How many PV’s are there?

A

4

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36
Q

Diastole

A

-period of time when the heart (atria) refills with blood after systole (contraction)

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37
Q

Ventricular Diastole

A

-period when both ventricles are relaxing (filling, no contracting)

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38
Q

Atrial Diastole

A

-period when both atria are relaxing (filling)

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39
Q

What are the great vessels?

A
  • SVC
  • IVC
  • PA’s
  • PV’s
  • AO
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40
Q

Which chamber of the heart does the aorta leave from?

A

-Lt ventricle

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41
Q

What does the thoracic/descending aorta supply?

A

Thoracic Structures:

  • pericardium
  • mediastinum
  • diaphragm
  • esophagus
  • bronchi
  • intercostal muscles
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42
Q

What does the abd aorta supply?

A

-abdominal viscera with oxygenated blood

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43
Q

Azygos Vein

A

-drains into SVC right before it enters the Rt atrium

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44
Q

Which brachiocephalic vein is longer?

A

-Lt is longer than Rt

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45
Q

What does arterial physiology depend on?

A

-cardiac status

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46
Q

What determines blood flow?

A
  • BP

- peripheral vascular resistance

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47
Q

Heart Failure

A

-cardiac output is insufficient to meet the needs of the body and lungs (Lt and Rt sided failure)

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48
Q

Valvular Dysfunction

A

-prolapsed, vegetations and regurgitation

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49
Q

What causes ischemia?

A

-impaired flow to the Lt ventricle muscle

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50
Q

Arrythmias

A

-irregular heart beat

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51
Q

Cardiomyopathy

A
  • problems within the heart muscle

- thickening and enlargement of chambers

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52
Q

Heart Beat

A

-rhythmic contraction of the heart

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53
Q

Heart Rat

A

-number of times that the heart contracts per minute

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54
Q

Internal Pacemaker

A

-sinoatrial and atrioventricular nodes that initiate he hearts own impulses to contract

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55
Q

What is the overall activity of the heart adjusted by?

A

-nervous impulses in order to serve he body’s changing needs

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56
Q

What is heart rate controlled by?

A

-autonomic nervous system (regulates functions below our consciousness)

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57
Q

What is the autonomic NS composed of?

A
  • sympathetic component

- parasympathetic component

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58
Q

What do the parasympathetic and sympathetic NS do?

A

Sympathetic: increases heart rate and force of cardiac contraction

Parasympathetic: decreases heart rate and force of contraction

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59
Q

What must be present for a fluid in a closed system to move from one point to another?

A

-energy gradient

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60
Q

In the case of an arterial tree, blood moves because of a ______ ______.

A

-pressure gradient

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61
Q

Which side of the heart has a higher pressure gradient?

A

-left

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62
Q

BP

A

-force exerted by blood against the arterial walls when the heart contracts

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63
Q

What is BP an important indicator of?

A
  • current cardiovascular function

- risk indicator of future cardiovascular morbidity and mortality

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64
Q

What do capillary beds consist of?

A
  • arterioles
  • venules
  • capillaries
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65
Q

each heart beat results in the ejection of approx. ____ cc of blood from each ventricle into the arterial tree.

A

70

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66
Q

What is oscillatory flow in the atrial tree initiated by?

A

-each beat of the heart (behaves like a flow generator with an ejected pulse)

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67
Q

Each heart best pumps approx. ___ml of blood into the atrial system. (causing a BP pulse)

A

70

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68
Q

How many litres of blood is ejected each minute?

A

5

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69
Q

What do the elastic walls of the conducting arteries store?

A

-excess volume by stretching during systole and relaxing during diastole

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70
Q

Where is energy stored during diastole?

A

-the stretched elastic walls of arteries

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71
Q

What is the energy stored in elastic walls used for?

A

-to propel blood forward through the peripheral resistance vessels

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72
Q

Is flow constant in the cardiac cycle?

A

Yes.

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73
Q

When is BP highest and lowest?

A

Highest- during ventricular systole (contraction)

Lowest- during diastole (filling)

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74
Q

Normal BP

A

120/80

120 is systolic
80 is diastolic

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75
Q

Essentail Principal in Circulation

A

-pressure gradient

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76
Q

What produces a pressure gradient?

A

-contraction of the heart and the resultant ejection of blood into the AO and systemic vessels

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77
Q

In circulation, what form is energy lost in?

A

-heat

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78
Q

Vascular Resistance

A

-resistance to flow that must be overcome to push blood through the circulatory system and create flow

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79
Q

Systemic Vascular Resistance (SVR)

A

-resistance offered by the peripheral circulation

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80
Q

What is net flow controlled by?

A

-arterial and arteriolar resistance

81
Q

In non diseased circulation, the main arteries have large ______ and their resistance to flow is ______.

A
  • diameters

- small

82
Q

Wha are the main resistance vessels?

A

-arterioles

83
Q

What is the major determinant of vascular resistance?

A

-papillary arterioles

84
Q

What kind of vessels are precapillary arterioles?

A
  • autoregulatory vessels

- dynamically change in diameter to increase or reduce blood flow

85
Q

What is an example of auto regulatory vessels?

A

-arterioles increase in diameter when exercising to allow for increased flow to muscles

86
Q

Sources of Peripheral Resistance

A
  • blood viscosity
  • vessel diameter/radius
  • vessel length
87
Q

Blood Viscosity

A
  • resistance to blood flow

- thickness/stickiness of blood

88
Q

What does viscosity determine?

A
  • friction against vessel walls
  • rate of venous return
  • work required to pump the heart
  • amount of oxygen transported to tissues and organs
89
Q

What affects blood viscosity?

A
  • hypertension
  • cholesterol (LDL and HDL), triglycerides
  • diabetes
  • obesity
  • smoking
  • males
  • age
  • temp.
  • anemia
90
Q

When does blood viscosity increase and decrease?

A

Increases- as blood is more hemoconcentrated (rbc concentration increases)

Decrease- as blood is more dilute

91
Q

The greater the viscosity of blood, the larger the ______ will be.

A

-resistance

92
Q

How does hemodilute (thinner) blood flow?

A

-more readily

93
Q

How does hemoconcentrated (thicker) blood flow?

A

-more steadily

94
Q

What is the hematocrit?

A

-% of rbc’s in the total blood volume

95
Q

What does the hematocrit affect?

A
  • blood viscosity

- resistance to flow

96
Q

The more viscous the blood, the ______ the resistance and the ______ the BP.

A
  • higher

- higher

97
Q

When will the hematocrit increase or decrease?

A

Increase:

  • more rbc’s
  • less plasma

Decrease:

  • less rbc’s
  • more plasma
98
Q

What does blood viscosity strongly depend on?

A

-hematocrit

99
Q

Polycythemia

A
  • abnormal elevation in red cell hematocrit causing high blood viscosity
  • increases resistance
  • increases work of heart
100
Q

What does anemia cause?

A
  • low hematocrit

- reduced blood viscosity

101
Q

What happens in low flow states that causes an increase in blood viscosity?

A

-rbc’s stick together

102
Q

What happens in clotting mechanisms are stimulated in the blood?

A

-platelet aggression and interactions with plasma proteins occur

103
Q

What does clotting cause?

A

-entrapment of rbc’s (increase in blood viscosity)

104
Q

What is an important factor that influences viscosity?

A
  • temperature

- thickness of fluid

105
Q

What happens when blood gets cold?

A
  • thicker

- slower

106
Q

What resistance does blood viscosity affect?

A

-peripheral

107
Q

If there is a greater resistance to flow, what is needed to pump the same volume of viscous fluid?

A

-greater pressure

108
Q

What has the biggest effect on resistance?

A

-radius

109
Q

Is there a large pressure change as blood flows from the AO to large vessels?

A

No.

110
Q

Small arteries and arterioles are the site of ___% of the pressure drop and are the main regulators of SVR (system vascular resistance).

A

70

111
Q

Which vessels are autoregulatory?

A

-arterioles

112
Q

What happens to resistance and pressure as diameter decreases?

A

-both increase

113
Q

What does total vessel length affect?

A

-peripheral resistance

114
Q

What does increased fatty tissue require?

A

-more blood vessels

115
Q

What happens to BP and resistance in a longer vessel?

A

-greater BP and resistance

116
Q

2 Factors that Control Peripheral Resistance

A

1) sympathetic nerve innervation

2) autoregulation (vasoconstriction and vasodilation)

117
Q

Vasoconstriction

A

-narrowing of a vessel due to contraction of the muscle wall

118
Q

What happens when the smooth muscle found in the tunica media is stimulated?

A
  • vasoconstriction

- contracts, squeezing the walls of the artery and narrowing the vessel

119
Q

When an after constricts, what happens to the blood flow and the pressure?

A
  • blood flow decreases

- pressure increases

120
Q

What can be regulated in the body through vasoconstriction?

A
  • body temp.

- BP

121
Q

Vasodilation

A

-widening of a vessel, due to relaxation of the muscular wall

122
Q

When a blood vessel dilates, what happens to resistance?

A

-decreases

123
Q

During exercise, what is required?

A

-increased blood flow to deliver oxygenated blood to the working muscle

124
Q

Where does vasodilation occur?

A

-arteriole and capillary bed

125
Q

What vessels are the “stopcocks” of the vascular tree?

A

-arterioles

126
Q

Where does BP take its biggest drop?

A

-arterioles

127
Q

What is the principle point of resistance to blood flow in the circulatory system?

A

-arterioles

128
Q

Autoregulation

A

-ability of vascular beds to constrict in response to a rise in BP and dilate in reposes to a fall in BP

129
Q

What is reactive hyperemia an example of?

A

-autoregulation

130
Q

Reactive Hyperemia

A
  • increase in blood flow
  • follows restoration of arterial inflow to a previously ischemic limb
  • ex. during exercise increase heart rate and vasodilation of arterioles allow more flow to muscular branches
131
Q

Vasoconstriction

A
  • decrease in vessel diameter

- increase in SVR

132
Q

Vasodilation

A
  • increase in vessel diameter

- decreases SVR

133
Q

What is high arterial pressure due to?

A

-high volume of blood in lg and medium sized arteries

134
Q

How is the large volume in the arterial tree preserved?

A

-maintaining balance between the amount of blood entering and leaving

135
Q

What is the amount of blood entering the arterial tree determined by?

A

-cardiac output

136
Q

What is the amount of blood exiting the arterial tree determined by?

A
  • arterial pressure

- total peripheral resistance (dependant on status of microcirculation)

137
Q

What is the driving pressure for flow within a vessel determined by?

A
  • potential energy (generated by Lt ventricular contraction that distends the vessel wall)
  • kinetic energy
  • pulsatile arterial flow signal is a summation of forward flow from the (Lt ventricle and reverse flow from tidal reflection)
138
Q

What happens when someone has arteriosclerosis?

A
  • arteries become calcified and rigid
  • cant expand when the pulse wave of systolic pressure passes through them
  • arterial walls experience higher pressure and become weaker
139
Q

Why do we need to know about atheroma?

A
  • develops in arteries and impedes the flow of blood
  • evident in spectral doppler
  • depends on extent of atheroma present and on the degree of obstruction
140
Q

What type of flow does blood have when it enters a vessel?

A

-plug flow (no leaders in velocity)

141
Q

What type of flow is in a straight non obstructed tube?

A
  • parabolic (laminar)
  • highest flow in centre
  • lowest flow at walls
142
Q

What is laminar flow determined by?

A

-frictional and internal forces between the layers of blood and changes throughout the pulse cycle

143
Q

At a low velocity, fluid flow is ______.

A

-laminar

144
Q

How is laminar flow characterized?

A

-motion of fluid along a well defined path

145
Q

What is flow a result of?

A

-pressure gradient

146
Q

In what way does blood viscosity increase across a vessel in early systole as fluid motion begins?

A

-uniformly

147
Q

When does turbulent flow happen?

A

-high velocities

148
Q

Turbulent Flow

A
  • elements no longer travel along well defined paths
  • random motion
  • irreversible loss of energy
149
Q

What is an example of disturbed flow?

A

-separation of flow that occurs in vessels with an obvious change in lumen size (ex. carotid bulb)

150
Q

What types of flow may she spectral broadening?

A
  • disturbed

- turbulent

151
Q

What can disturbed flow indicate?

A

-pathological change in vessel

152
Q

Where is disturbed flow seen?

A

At sites of arterial…

  • dilation
  • curvature
  • branching
  • bifurcation
153
Q

Why is the pressure drop across a stenosis high?

A

-as a result of energy loss in the post stenotic region

154
Q

Critical Stenosis

A

-narrowing of arterial lumen (reduced volume, pressure and flow)

155
Q

Why is there a pressure decrease before a stenosis?

A

-to allow fluid to accelerate into the stenosis and decelerate out of it

156
Q

What happens to arterial pressure prox. and dist. to a stenosis?

A

Prox.- higher

Dist.- lower

157
Q

What is lost distal to a stenosis?

A
  • pressure

- kinetic energy

158
Q

When atherosclerosis develops, wha compensatory mechanisms come into play to preserve perfusion?

A
  • development of collateral circulation
  • local dilation of the affected arterial segment
  • increase in the extraction efficiency of oxygen from blood
159
Q

How can flow rate to an organ be controlled?

A

-degree of constriction of distal arterial bed

160
Q

Types of Flow Waves

A
  • triphasic

- monophasic

161
Q

2 Types of Vascular Beds

A

1) low resistance (ex. brain)

2) high resistance (ex. muscles at rest)

162
Q

Low Resistance Beds

A
  • brain
  • parenchymal organs (kidneys, liver)
  • need continuous flow
163
Q

High Resistance Beds

A
  • peripheral circulation (arms, legs and sm intestine when it’s not digesting)
  • muscles need a high rate of oxygen (especially when exercising)
  • low, absent or reversed flow during diastole
164
Q

When is a tripahsic waveform found?

A

-arteries supplying high resistance peripheral vascular beds

165
Q

3 Components of Flow

A
  • forward flow in systole
  • diastolic flow reversal
  • forward flow in late diastole
166
Q

What does a biphasic flow wave indicate?

A
  • mild disease if seen in vessel supplying a high resistant bed
  • loss of 3rd component in late diastole
167
Q

Monophasic Waveform

A
  • flow is all above baseline
  • normally seen in low resistance beds (brain, kidneys)
  • abnormal if seen in a vessel supplying a high resistant bed
168
Q

What is the result of tandem lesions?

A

-large losses of energy at the entrance and exit of lesion

169
Q

What is the result of tandem lesions?

A

-disturbed flow patterns (jets, turbulence, eddies)

170
Q

How come at rest, the blood flow of a stenosed or occluded vessel may be normal?

A
  • collateral pathways

- decrease in peripheral resistance

171
Q

How can we measure the severity of occlusive disease? (stenosis/occulsion)

A

-measure systolic pressure

172
Q

The doppler waveforms have a ______ component (monophasic) rather than the double or triple components usually heard.

A

-single

173
Q

The monophasic signal occurs only during ______.

A

-systole

174
Q

Blood Flow in Normal Arteries

A
  • velocity increases to a peak during early systole

- decreases during early diastole (when flow reversal can occur)

175
Q

What does the shape of the resulting pulse velocity wave reflect?

A

-pressure gradient

176
Q

Over normal peripheral arteries, double or triple sounds are heard. The second sound represents the diastolic flow ______ (biphasic) and the 3rd sound represents the ___ forward component (triphasic).

A
  • reversal

- 2nd

177
Q

Velocity Profile

A

-velocity of blood will vary depending on it’s position within the vessel

178
Q

What profile does steady laminar flow demonstrate?

A
  • parabolic

- ex. CCA

179
Q

Where are max. and min. velocity?

A

Max.- centre

Min.- wall

180
Q

What is the main parameter for evaluating the severity of carotid stenosis?

A

-flow velocity

181
Q

How do we ensure the the site of the highest flow velocity has been detected in a stenosis?

A

-sample through whole area of presumed stenosis until the distal end of plaque is seen

182
Q

Effects of Arterial Stenosis

A
  • widening of band of systolic velocity
  • spectral broadening
  • complete filling
  • reversal of flow (eddies)
183
Q

Alterations in Venous Hemodynamics Occur With:

A
  • change in posture
  • competent or incompetent of valves
  • effects of venous obstruction
184
Q

What are the 3 main components of venous pressure in the lower limbs?

A
  • hydrostatic (gravitational) pressure
  • residual pressure
  • muscular and respiratory pressure
185
Q

Hydrostatic Pressure

A
  • due to height of venous blood column
  • applies to standing patient
  • flow from the furthest point (feet) must return to the Rt atrium
186
Q

In the lower limbs, what is the main resistance to flow due to?

A

-microcirculation

187
Q

Residual Pressure

A

-venous pressure supplied by the arterial pressure at the venous end of capillaries

188
Q

Which muscles act as an alternate pump to the heart?

A

-peripheral muscles

189
Q

The venous valves, like the cardiac valves, establish _______ flow.

A

-unidirectional

190
Q

Where is the venous response to respiration reversed?

A

-in the abd

191
Q

What can influence the respiratory changes in blood flow in the upper limbs?

A

-posture

192
Q

Phasicity

A
  • changes with respiration

- valsalva manoeuvre affects flow

193
Q

Spontanaity

A

-flow is most spontaneous closest to heart

194
Q

Spontanaity

A
  • flow is most spontaneous closest to heart

- flow is readily apparent

195
Q

Compressibility

A

-veins are compressible due to a thinner muscular wall (can r/o clot this way)

196
Q

What does valsalva do?

A
  • increases intrathoracic and abd pressure

- decreases or reverses flow in peripheral veins

197
Q

Arterial Hemodynamics

A
  • waveform reflects cardiac cyclce
  • not affected by respirations
  • high pressure system
  • pulsatile
198
Q

Venous Hemodynamics

A
  • waveforms reflect respiratory movements
  • phasicity
  • low pressure system
  • no pulse

Term 2 (19 decks)

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