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Vascular > Quiz 2 (Hemodynamics) > Flashcards

Quiz 2 (Hemodynamics) Flashcards

1
Q

define hemodynamics

A

basic principles of the dynamics of blood circulation

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2
Q

are hemodynamics the same for arterial and venous circulation?

A

no

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3
Q

what are the tiniest blood vessels?

A

capillaries

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4
Q

what is the order of blood vessels starting at arteries to veins?

A
  • arteries
  • arterioles
  • capillaries
  • venules
  • veins
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5
Q

what is an artery called when it cant be seen with the naked eye anymore?

A

arteriole

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6
Q

what is thicker in arteries?

A

tunica media

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7
Q

why is the artery tunica media thicker than veins?

A

allows for greater elasticity

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8
Q

arteries tunica media have an _________ amount of smooth muscle

A

increased

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9
Q

what does the arteries deal with?

A

surges of oxygenated blood from heart

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10
Q

do arteries have valves?

A

no

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11
Q

do arteries have a high or low pressure system?

A

high pressure system

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12
Q

are highly tensile vessels needed in veins?

A

no

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13
Q

is venous system a high or low pressure system?

A

low

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14
Q

do veins contain valves?

A

yes

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15
Q

are more valves in veins located in the proximal or distal part of the body?

A

distal

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16
Q

what is the structure of vein walls?

A

collapsible
larger
misshaped

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17
Q

why are veins easier to extract blood?

A

thinner walls

larger diameters

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18
Q

why is it less painful to get sticked with a needle from a vein?

A

The thinner the vessel, the less the innervation, so the less painful to stick with a needle

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19
Q

why will blood not seep out of your vein when getting sticked with a needle?

A

veins have blood under less pressure within them

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20
Q

is their more blood in you arteries or veins?

A

veins, they store blood

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21
Q

where do veins store blood?

A

in the valves

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22
Q

why do veins have valves?

A

helps blood get back to the heart

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23
Q

is it slower or faster getting blood back to the heart?

A

slower

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24
Q

when do valves prevent backflow?

A

during diastole

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25
Q

what does momentum do?

A

during systole it forces valves open

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26
Q

when do valves close?

A

when momentum decreases

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27
Q

what moves blood forward into the right atrium?

A

decrease in thoracic pressure

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28
Q

are veins deep or near the surface of the skin?

A

near the surface of the skin

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29
Q

what is the process referred to when getting blood back to the heart with your muscles?

A

ladder system

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30
Q

what veins typically have a pulsatile flow?

A

veins closer to the heart (hepatic veins)

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31
Q

what does spontaneous mean?

A

probe down on vein and there is instant flow

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32
Q

describe low resistant vascular bed

A

always needs blood flow (brain)

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33
Q

describe high resistant vascular bed

A

changes depending-can stop at times (legs)

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34
Q

when can blood be stored in arteries?

A

when they expand

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35
Q

what will happen if arteries cant expand?

A

blood pressure will rise

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36
Q

pressure gradient

A

measure of pressure the veins excert

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37
Q

what is the direction of pressure gradient?

A

high pressure to low pressure

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38
Q

what is phrenic vein?

A

diaphragm

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39
Q

what is azygos vein?

A

lateral veins descends into thoracic to right side of vertebral column

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40
Q

what does the azygos serve?

A

as a collateral if the SVC or IVC is occulted or blocked

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41
Q

what is vessel compliance?

A

ability to expand and contract

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42
Q

vascular musculature

A

relative to max. dilated state

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43
Q

ischemia

A

tissue death

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44
Q

what are the pumps in the arterial system?

A
  • heart
  • aortic pump
  • muscular venous pump
  • respiratory pump
  • gravity
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45
Q

what is the principal force behind blood flow?

A

pumping action of the heart

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46
Q

what exists in the right atrium?

A

A partial vacuum exists in the right atrium during the right ventricular filling phase to suck venous blood from the IVC

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47
Q

what does the aorta act as?

A

subsidiary pump

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48
Q

Much of the energy resulting from cardiac contraction must be _____

A

stored

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49
Q

Much of the energy resulting from cardiac contraction must be stored?

A

is because of the holdup of blood flow that occurs in the capillary bed

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50
Q

The aorta and other elastic arteries near the heart serve as what?

A

store excess energy by stretching with each systole

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51
Q

what does the stretching of the aorta during peak systole allows the aorta to act as?

A

“reservoir”,storing much of the blood expelled by the heart

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52
Q

what happens in the aortic pump during diastole?

A

the energy stored in the arterial walls dissipates the large volume of blood stored in the aorta by forcing blood forward in the arteries

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53
Q

what is the pump for the venous system?

A

muscular pump

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54
Q

what ensures venous return at rest when in a supine postion?

A

pressure gradient

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55
Q

what muscles in the legs help with the muscular pump?

A

soleus and gastrocnemius sinusoids

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56
Q

flow which is initiated by cardiac contraction is further assisted by what?

A

muscular contraction and venous valve action

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57
Q

what does the respiratory pump assist in?

A

venous return to the heart

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58
Q

pressure in the thorax is always ________ than atmospheric pressure?

A

lower

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59
Q

Inspiration causes an _______ in abdominal pressure and a ________ in thoracic pressure

A

increase in abdominal pressure and decrease in thoracic pressure

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60
Q

what happens with the blood flow during inspiration?

A

reduced flow in the abdomen and increased venous flow in the chest

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61
Q

during each phrase in respiration what is the blood flow in the upper and lower extremities?

A

venous flow in the upper extremities is opposite to flow in the lower extremities during each phrase of respiration

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62
Q

where does gravity play a role for venous flow in the upper and lower extremities?

A
  • upper extremity, gravity aids venous return from head and neck (any body part placed higher than level of heart)
  • lower extremity, gravity acts as a deterrent
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63
Q

what is the end of the smallest airways?

A

alveoli

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64
Q

what is the purpose of alveoli?

A

exchange of oxygen and carbon dioxide takes place

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65
Q

what chamber does the pulmonary arteries come off of?

A

off the base of the right ventricle

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66
Q

what is ventricular systole?

A

period of contraction of the heart

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67
Q

what is arterial systole?

A

occurs toward the end of the ventricular diastole and completes by filling of the ventricles

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68
Q

what is ventricular diastole?

A

period during which both ventricles are relaxing

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69
Q

what is atrial diastole?

A

period during which the atria are relaxing (filling)

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70
Q

do the atria contact at the same time?

A

yes

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71
Q

do the ventricles contract at the same time?

A

yes

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72
Q

where is the blood going during systole?

A

great vessels

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73
Q

where is the blood going during diastole?

A

ventricles

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74
Q

where does the azygos vein drain?

A

into SVC just prior to the RT atrium

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75
Q

which brachiocephalic vein is longer?

A

left

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76
Q

what influences blood flow?

A
  • cardiac function
  • vessel compliance
  • peripheral resistance
  • tone of vascular musculature
  • blood viscosity
  • pattern of branching vessels and collaterals
  • vasoconstriction and vasodilation
  • exercise
  • autoregulation
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77
Q

what does arterial physiology depend on?

A

cardiac status

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78
Q

what is blood flow determined by?

A

blood pressure and peripheral vascular resistance

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79
Q

heart failure

A

cardiac output is insufficient to meet the needs of the body and lungs

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80
Q

valvular dysfunction

A

prolapsed, vegetations, regurgitation

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81
Q

Ischaemia

A

Ischaemia due to impaired flow to left ventricular muscle (CAD)

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82
Q

arrythmias

A

irregular heart beat

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83
Q

Cardiomyopathy

A

problems within the heart muscle-thickening and enlargement of chambers

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84
Q

heart beat

A

rhythmic contraction of the heart

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85
Q

heart rate

A

number of times that the heart contracts per minute

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86
Q

Internal pacemaker

A

sino-atrial and atrio-ventricular nodes that initiates the hearts own impulses to contract

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87
Q

what is our heart rate controlled by?

A

autonomic nervous system

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88
Q

what increases heart rate and force of cardiac contraction?

A

sympathetic nervous system

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89
Q

what decreases heart rate and force of cardiac contraction?

A

parasympathetic nervous system

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90
Q

what must exist in order for fluid in a closed system to move from one point to another?

A

an energy gradient

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91
Q

which side of the heart has higher pressure and why?

A

left side is higher pressure to create the necessary pressure gradient

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92
Q

what is blood pressure?

A

Force exerted by the blood against the arterial walls when the heart contracts

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93
Q

why do we measure blood pressure?

A

indicator of current cardiovascular function and a risk indicator of future cardiovascular morbidity and mortality

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94
Q

what does the capillary bed consist of?

A

arterioles, capillaries, and venules

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95
Q

in each heart beat, how much blood is ejected?

A

approximately 70cc

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96
Q

what builds at the beginning of each cardiac contraction as the pressure in left ventricle rapidly rises?

A

pressure builds

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97
Q

how does the aortic valve open?

A

when pressure in the left ventricle exceeds the pressure in the ascending aorta

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98
Q

where does the pressure wave go after it goes through the arterial system?

A

past the resistance vessels (arterioles) and into the venous system

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99
Q

why does the mean pressure gradually decline?

A

losses in total fluid energy, however the systolic portion of the pressure wave actually increases

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100
Q

wave propagation

A

This phenomenon is due to increasing stiffness of the vessel walls toward the periphery and the reflected waves which are enhanced by increasing peripheral resistance

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101
Q

in the circulatory system there is a ______ pressure, ______ energy arterial reservoir

A

high pressure,high energy

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102
Q

in the circulatory system there us a _____ pressure, ____ energy venous pool

A

low pressure,low energy

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103
Q

when is energy stored in the stretched elastic walls of the arteries?

A

during diastole

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104
Q

what propels blood forward through the peripheral resistance vessels?

A

energy stored in the stretched elastic walls of the arteries

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105
Q

when is pressure in the heart the highest?

A

during ventricular systole (contraction)

lowest during diastole (filling)

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106
Q

what is the normal pressure during the cardiac cycle?

A

120/80

120=systolic
80=diastolic

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107
Q

what happens to the pressure as blood flows toward the periphery?

A

gradually decreases

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108
Q

how is pressure and energy produced?

A

contraction of the heart and resultant ejection of blood into aorta and systemic vessels

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109
Q

in the circulatory system, energy is lost in the form of what?

A

heat

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110
Q

what is vascular resistance?

A

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

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111
Q

systemic vascular resistance(SVR)

A

the resistance offered by the peripheral circulation

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112
Q

what is net flow controlled by?

A

arterial and arteriolar resistance

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113
Q

what are the main resistance vessels?

A

arterioles

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114
Q

flow model

A

An increase in resistance in a large distributing artery because of atheroma must be compensated by a decrease in the resistance of the small arteries and arterioles

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115
Q

what does any increase in the degree of stenosis lead to?

A

reduction in flow

116
Q

what is the major determinant of vascular resistance?

A

precapillary arterioles

117
Q

autoregulatory vessels

A

they can dynamically change in diameter to increase or reduce blood flow Ex) exercise

118
Q

what happens to blood flow for increased flow to muscles?

A

The arterioles will increase in diameter to allow for increased flow to the muscles-the peripheral flow then becomes low resistant with continuous flow throughout systole and diastole

119
Q

what are sources of peripheral resistance?

A
  • blood viscosity
  • blood vessel diameter(radius)
  • total vessel length (not changing)
120
Q

what is blood viscosity?

A

measure of resistance of blood to flow (thickness and stickiness)

121
Q

what does viscosity determine?

A
  • friction against vessel walls
  • rate of venous return
  • work required to pump the heart
  • how much oxygen is transported to tissues and organs
122
Q

what is blood viscosity affected by?

A
  • hypertension
  • cholesterol
  • diabetes
  • obesity
  • smoking
  • male
  • aging
  • temp.
  • anemia
123
Q

hemoconcentrated

A

red blood cell concentration increases

124
Q

how does blood viscosity increase and decrease?

A

Blood viscosity increases as blood is more hemoconcentrated and decreases as blood is more dilute

125
Q

the greater the viscosity the larger the _______

A

resistance

126
Q

__________ blood will flow more readily

A

Hemodilute(thinner)

127
Q

________ blood will flow more steadily

A

Hemoconcentrated blood(thicker)

128
Q

hematocrit

A

percentage of red blood cells in the total blood volume

129
Q

what does hematocrit affect?

A

blood viscosity so therefore resistance to flow

130
Q

when can hematocrit increase?

A

there are more red blood cells or less plasma in the blood and vise versa

131
Q

what does blood viscosity strongly depend on?

A

hematocrit

132
Q

Polycythemia

A

a condition of abnormal elevation in red cell hematocrit causing higher blood viscosity

133
Q

what can polycythemia cause?

A

increases the resistance to flow,increases the work of the heart and can impair organ perfusion

134
Q

what does anemia cause?

A

low hematocrit and reduced blood viscosity

135
Q

what happens to red blood cells in low flow states?

A

red cells stick together which increases the blood viscosity

136
Q

what happens if clotting mechanisms are stimulated in the blood?

A

platelet aggregation and interactions with plasma proteins occur

137
Q

does blood get thicker when it is hot or cold?

A

cold

138
Q

what type of relationship does temperature and viscosity have?

A

inverse (blood temp. decreases and viscosity increases)

139
Q

There is _______ pressure change as blood flows from the Aorta to large arteries

A

very little

140
Q

what are the main regulators of SVR (systemic vascular resistance)?

A

small arteries ad arterioles

141
Q

what is the percentage of pressure drop in the small arteries and arterioles?

A

70%

142
Q

arterioles are ________

A

autoregulatory

143
Q

what does vessel diameter affect?

A

peripheral resistance

144
Q

when vessel diameter decreased why is there more resistance?

A

a greater proportion of the fluid is in contact with the walls therefore resistance to flow is increased and pressure rises

145
Q

larger diameter= _______ volume= _______ pressure

A

same volume=less pressure

146
Q

smaller diameter=________ volume= _______ pressure

A

same volume=more pressure

147
Q

what does total vessel length affect?

A

peripheral resistance

148
Q

what does a longer vessel length do in terms of resistance and blood pressure?

A

the longer the vessel length, the greater the resistance and the greater the blood pressure

149
Q

what is the relationship of vessel resistance to viscosity?

A

directly proportional

150
Q

what is the vessel resistance in relationship to radius?

A

inversely proportional to the radius to the 4th power

151
Q

what is the vessel resistance in relationship to the length of the vessel?

A

directly proportional

152
Q

what 2 factors controls peripheral resistance?

A
  • sympathetic nerve innervation

- autoregulation (vasoconstriction and vasodilation)

153
Q

what happens to the blood flow and pressure within a vessel during vasoconstriction?

A

When an artery constricts, the flow of blood decreases and the pressure within the vessel rises

154
Q

what does vasoconstriction and vasodilation regulate?

A

body temperature and blood pressure

155
Q

what happens to blood flow during vasodilation?

A

When a blood vessel dilates, blood is able to flow through the vessel with less resistance

156
Q

where does vasodilation occur?

A

at the arteriole and capillary bed level

157
Q

what are the “stopcocks” of the vascular tree?

A

arterioles

158
Q

where does blood pressure take its biggest drop?

A

arterioles

159
Q

reactive hyperemia

A

marked increase in blood flow which follows restoration of arterial inflow to a previously ischemic limb

160
Q

what is an example of reactive hyperemia?

A

during exercise induced increased heart rate and vasodilation of arterioles to allow more flow to muscular branches

161
Q

what increases SVR?

A

vasoconstriction (vise versa for vasodilation)

162
Q

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

A

cardiac output

163
Q

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

A

arterial pressure and total peripheral resistance(dependant on status of microcirculation)

164
Q

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

A
  • potential energy

- kinetic energy

165
Q

what is potential energy generated by?

A

the left ventricular contraction that distends the vessel wall

166
Q

what is the pulsatile arterial flow signal a summation of?

A

forward flow from the left ventricle and reverse flow from the tidal reflection

167
Q

how is energy lost in the flow of blood?

A

friction of blood at the vessel wall and between adjacent layers of blood

168
Q

where are energy losses the highest?

A

in the region of stenosis due to considerable friction during turbulent flow and vortex type motion

169
Q

what will increase within a stenosis?

A

there will be an increase in blood kinetic energy associated with the increase in blood velocity

170
Q

bernouilli’s principle

A

there is a corresponding fall in blood pressure immediately after the stenosis

171
Q

what is compliance?

A

the ability of a vessel to distend and increase volume with increasing transmural pressure

172
Q

how much larger is venous compliance than arteries?

A

30x

173
Q

what is blood pressure affected by?

A

peripheral resistance and blood vessel elasticity

174
Q

what does a healthy elastic artery do during systolic pressure?

A

expands,absorbing the shock of systolic pressure

175
Q

what maintains the continued flow during diastole?

A

elastic recoil

176
Q

what does a arteriosclerosis artery do during systolic pressure?

A

become calcified and rigid,so they can’t expand when the pulse wave of systolic pressure passes through them

177
Q

plug flow

A

when flow enters a vessel there are no leaders in velocity (velocity is the same)

178
Q

parabolic (laminar) flow

A

as blood moves along a straight tube it becomes parabolic

179
Q

in parabolic flow, where is the flow the fastest?

A

in the center of the vessel, slowest at the walls

180
Q

why does laminar flow occur?

A

This profile is determined by frictional and inertial forces between the layers of blood and changes throughout the pulse cycle

181
Q

when does blood velocity increase uniformly across a vessel?

A

early systole as a fluid motion begins

182
Q

when does turbulent flow occur?

A

very high velocities

183
Q

what happens with energy with turbulent flow?

A

significant irreversible loss of energy

184
Q

what are the essential flow states?

A

turbulent

laminar

185
Q

what does disturbed flow show as?

A

The velocities of the blood cells will be more random and displays itself as “spectral broadening”,but will not show an increase in velocity in a normal vessel

186
Q

when does disturbed flow occur?

A

sites of arterial dialation, curvature, branching or bifurcation

187
Q

in normal circulation, flow is mainly ________

A

laminar

188
Q

where in the vessel does disturbed or turbulent flow occur?

A

post stenotic region

189
Q

what does turbulent and disturbed flow give rise to?

A

spectral broadening

190
Q

The pressure drop across a stenosis is __________ as a result of _________in the poststenotic region

A

high, energy loss

191
Q

critical stenosis

A

narrowing of the arterial lumen resulting in a hemodynamically significant reduction in volume,pressure and flow

192
Q

what happens to pressure before a stenosis?

A

pressure decreases before a stenosis to allow fluid to accelerate into the stenosis and decelerate out of it

193
Q

what is the magnitude dependant on?

A

degree of stenosis

194
Q

where is arterial pressure high and low at a site of narrowing?

A

higher proximal to the site and lower distally because of the loss of kinetic energy

195
Q

Anastomosis

A

branches form between adjacent blood vessels

196
Q

what happens due to atherosclerosis to prevent perfusion?

A
  • development of a collateral circulation
  • a degree of local dilation of the affected arterial segment
  • An increase in the extraction efficiency of oxygen from blood
197
Q

damped and trickle flow

A

Very high degrees of stenosis are accompanied by a low flow rate and low velocities

198
Q

what are the three types of flow waves?

A
  • monophasic
  • biphasic
  • monophasic
199
Q

what are the 2 types of vascular beds?

A
  • low resistant bed (brain)

- high resistant bed (muscles at rest)

200
Q

low resistant beds

A

Their metabolic process needs continuous
forward flow throughout the cardiac cycle
(kidneys, liver, brain)

201
Q

High resistant beds

A

peripheral circulation (small intestine not during digestion)

202
Q

how is high resistant beds characterized?

A

low, absent, or reversed flow during diastole

203
Q

where would you find triphasic waveforms?

A

The triphasic waveform is normally found in arteries supplying a high resistance peripheral vascular bed

204
Q

what happens in the periphery during systole?

A

forward flow throughout

205
Q

why does temporary flow reversal occur during diastole?

A

a negative pressure gradient caused by peripheral resistance to forward flow

206
Q

when does flow reversal decrease?

A

increasing vasodilation as in exercise, body heating, and stenosis

207
Q

when does flow reversal increase?

A

vasoconstriction

208
Q

what are the 3 components of flow?

A
  • forward flow in systole
  • diastolic flow in reversal
  • forward flow in late diastole
209
Q

describe appearance of biphasic flow?

A

loss of 3rd component in late diastole

210
Q

describe appearance of monophasic waveform?

A

flow is all above baseline

211
Q

when is monophasic waveform seen?

A

low resistance beds

212
Q

what are factors determining the stenosis effect?

A
  • Length and diameter of the narrowed segment
  • Roughness of the epithelial surface
  • Degree of irregularity of the narrowing and its shape(abrupt or gradual)
  • Ratio of the cross-sectional area of the stenotic zone to that of the normal vessel
  • The rate of flow
  • The arteriovenous pressure gradient
  • Peripheral resistance beyond the stenosis
213
Q

tandem lesions

A

2 or more stenosis

214
Q

why may a vessel appear normal when there is a stenosis?

A

collaterals happen so we measure systolic pressure

215
Q

what resistance will blood flow have proximal to a stenosis or occlusion?

A

higher resistant pattern due to the impending resistance to flow up ahead

216
Q

what is the resistance after a stenosis?

A

pressure wave is more damped than normal due to the pressure drop across the stenosis

217
Q

what happens to flow reversal distal to a stenosis?

A

disappears

218
Q

when do monophasic signals only occur?

A

during systole

219
Q

The disappearance of reversed flow distal to the stenosis results from a combination of which factors:

A

1-The maintenance of a relatively high level of forward flow throughout the cardiac cycle
2-Resistance to reverse flow created by the stenotic lesion
3-A decrease in peripheral resistance as a result of ischemia
4-Damping of the pressure wave by the lesion,resulting in attenuated pressure pulses

220
Q

in normal arteries when does blood flow velocity increase?

A

during early systole

221
Q

in normal arteries when does blood flow velocity decrease?

A

during early diastole

222
Q

what reflects pressure gradient?

A

The shape of the resulting pulse velocity wave

223
Q

over normal peripheral arteries what do the sounds represent?

A

second sound represents the diastolic flow reversal (biphasic)
third sound represents the second forward component (triphasic)

224
Q

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

A

flow velocity

225
Q

where do we measure blood flow to evaluate the significance of the occlusive disease?

A

blood flow at and distal to arterial obstructions

226
Q

what are the effects of arterial stenosis?

A
  • Widening or dispersal of the band of systolic velocity
  • Spectral broadening(loss of clear window below systolic portion)
  • Complete filling- in of the spectral tracing
  • Reversal of blood flow due to eddies
227
Q

what is the pressure remaining in the veins after the blood has went through capillaries for a subject in a supine position?

A

pressure is low

228
Q

Alterations in venous hemodynamics occur with :

A
  • changes in posture
  • important consequence of competence or incompetence of venous valves
  • effects of venous obstruction
229
Q

what are the 3 components of the venous pressure of the lower limbs?

A
  • hydrostatic (gravitational pressure)
  • residual pressure
  • muscular and respiratory pressure
230
Q

in lower limbs what is the main resistance to flow?

A

microcirculation

231
Q

residual pressure

A

At the venous end of the capillaries,the venous pressure supplied by the arterial pressure

232
Q

how does the cardiac pump bring blood back to the heart?

A

contraction (systole) and relaxation (diastole) brings flow back to the right atrium

233
Q

what do the volume in the veins of the thorax do with inspiration?

A

volume increases

234
Q

what happens to lower limb flow in veins during inspiration?

A

blood flow decreases

235
Q

what happens to upper limbs in veins during expiration?

A

blood flow decreases

236
Q

what are the venous flow characteristics?

A
  • phasicity
  • spontaneity
  • augmentation
  • compressibility
237
Q

where is flow most spontaneous?

A

closest to the heart-instant flow pattern

238
Q

Augmentation

A

wrap around flow

239
Q

Spontaneous flow

A

Flow is readily apparent

240
Q

Valsalva manoever

A

Increased abdominal pressure by “bearing down” will cause the valve to close and the flow to cease -this proves the valve is competent

241
Q

arterial hemodynamics?

A
  • Waveform reflects the cardiac cycle
  • Not affected by respirations
  • High pressure system
  • Pulsatility:Varies according to vascular bed it supplies
  • Has a pulse
242
Q

venous hemodynamics

A
  • Waveform reflects the respiratory -movements:
  • Phasicity
  • Low pressure system
  • Pulsatility:Varies according to proximity to the heart
  • No pulse
243
Q

what is the doppler shift equation?

A

fd=ft-fr

244
Q

cos0

A

1

245
Q

cos30

A

0.8

246
Q

cos60

A

0.5

247
Q

cos90

A

0

248
Q

what parameters would affect the doppler equation?

A
  • velocity

- angle of insonation (cosine)

249
Q

what angle does not help us?

A

90

250
Q

how does the angle affect the flow?

A

Direction of blood
flow in relation to the
transducer-toward
or away

251
Q

what angle should we be for doppler?

A

under 60 degrees

252
Q

what do we do to improve doppler angle?

A
  • heel and toe
  • use angle correct
  • change colour box angle
  • change window of insonation
253
Q

in spectral doppler where is the flow in relation to the baseline when it is toward the transducer?

A

above the baseline

254
Q

where should our sample volume-gate be set in the vessel?

A

center of vessel and be as small as possible so we pick up a cleaner signal

255
Q

why do we have to keep angle correct the same universally?

A

consistency within:

  • entire exam
  • recheck exams
  • patient to patient
256
Q

ideally what should the spectral trace be set?

A

2/3 of the display

257
Q

what adjusts the scale on doppler?

A

PRF

258
Q

what happens when spectral wall filter is set too low?

A

wall thump from arterial systole

259
Q

what happens when spectral wall filter is set too high?

A

eliminates echoes within waveform

260
Q

what causes aliasing?

A

PRF too low

so we increase the velocity scale

261
Q

what will happen If you adjust the colour bar?

A

will result in inadequate colour representation

262
Q

what happens if you place the colour baseline too low?

A

only higher velocity flow will be depicted

263
Q

what happens if you place the color baseline too high?

A

only lower velocities will be depicted

264
Q

what direction does red indicate?

A

red indicates flow towards the transducer

265
Q

what direction dies blue indicate?

A

flow away from the transducer

266
Q

where is arterial flow in relation to the baseline in spectral doppler?

A

above the baseline

267
Q

what does a colour box too big do to our image?

A

decreased frame rate and poor resolution of colour within the vessel

268
Q

frame rate ________ as the box size increase

A

frame rate decreases as the box size increases

269
Q

besides colour box what else influences frame rate?

A

PRF

270
Q

increasing the PRF will ___________ the frame rate

A

increase

271
Q

what decreases as beam is steered with a colour box?

A

sensitivity of transducer

272
Q

when would we use a straight colour box?

A

vessel is angled quite steeply

273
Q

what direction do we steer our colour box?

A

Steer the box so that it is
parallel to the flow,not
angled in the opposite direction

274
Q

how do we angle our colour box when we get to a bifurcation?

A

angle to colour box twice to delineate each branch with the most clarity
as the vessels usually
are not parallel

275
Q

what velocity range do carotids have?

A

carotid settings have a higher velocity range due to higher arterial flow

276
Q

when could aliasing occur when thinking about velocity ranges?

A

Color aliasing will occur for example-if a venous setting is used to visualize
arterial flow

277
Q

when wall filter is set too high and velocity close to the walls is not shown what can it give a false impression of?

A

wall thickening

278
Q

what are guidelines for optimal doppler examination?

A
  • adjust gain and filter
  • adjust velocity scale and baseline
  • doppler angle under 60 by steering and probe position
  • colour box as small and superficial as possible
  • sample volume size
  • avoid transducer motion
279
Q

advantages for power doppler?

A
  • no aliasing
  • angle independent
  • detect low velocity flow
  • imaging tortuous vessels
  • grading stenosis
280
Q

disadvantages to power doppler?

A
  • no velocity of flow
  • no direction of flow
  • very motion sensitive
281
Q

when is fluid flow laminar?

A

low velocity

282
Q

what is the resistance offered by the peripheral circulation also known as?

A

systematic vascular resistance

283
Q

what is the major regulator of vascular resistance?

A

vessel radius

284
Q

Augmentation

A

Venous flow can be squeezed to observe a large bolus of blood flowing through a vein in an unobstructed vessel

285
Q

what is blood flow determined by?

A
  • blood pressure

- peripheral vascular resistance

Vascular (10 decks)

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