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respiratory physio > pulmonary circulation > Flashcards

pulmonary circulation Flashcards

1
Q

RV ejection fraction should equal Lv cardiac output.. why?

A

even though the pressures are different, you’re dealing with the same volumes

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2
Q

the resistance to flow in pulmonary system compared to systemic

A

resistance to flow in pulmonary system is one tenth of systemic circulation

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3
Q

what is the structure of the pulmonary artery like>

A

this walled (1/3) thickness of aorta) and very compliant

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4
Q

RV pressure #

A

25/0-4

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5
Q

RA pressure #

A

0-4

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6
Q

LA pressure #

A

8-10

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7
Q

pulm artery pressure #

A

25/10

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8
Q

pulmonary vessels are divided into

A

alveolar and extra alveolar

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9
Q

what do alveolar vessels do

A

alveolocapillary network involved in gas exchange. the big capillary bed where gas exchange occurs

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10
Q

what collapses alveolar vessels during lung expansion

A

high positive pressure

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11
Q

what do extra-alveolar vessels do?

A

they are the arteries and veins which convey blood to and from the resp units. think: similar to conducting airways that do not participate in gas exchange

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12
Q

are extra-alveolar vessels affected by pressures in lung

A

no

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13
Q

do extra-alveolar vessels compress with positive pressure

A

no

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14
Q

bronchial vessels

A

oxygenated blood from systemic circulation, 1-2% of cardiac output, empty into left atrium

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15
Q

when you take a breath in, what do the alveoli do?

A

squeeze and push on the capillaries and increase resistance

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16
Q

???at low lung volumes, vascular resistance is

A

high. because extra-alveolar vessels become narrow

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17
Q

???at high lung volumes, resistance is

A

low. because the capillaries are stretched

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18
Q

alveolar capillary walls contribute to what % of total resistance

A

40

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19
Q

alveolar arterioles contribute what percentage of resistance

A

5

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20
Q

in the body, major resistance vessels?

A

arterioles (75%)

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21
Q

pulmonary resistance of capillary vessels is reduced by ___ lung volumes. high or low?

A

LOW lung volumes. (and high blood flow rates)

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22
Q

resistance of capillary vessels is greater when

A

lower BP or less vascular distending pressures

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23
Q

passive regulation of blood flow through capillaries occurs in response to changes in

A

cardiac output

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24
Q

increases in blood flow are accommodated by

A

recruitment and distention

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25
Q

when arterial ad venous pressure increases, PVR is

A

decreased

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26
Q

recruitment is simply

A

the opening of previously closed vessels

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27
Q

distension is simply

A

increase in caliber of vessels

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28
Q

explain recruitment

A

when you increase pressure or flow in the venous or arterial side, all the sudden you recruit some of these small capillary channels that were closed, you recruit them and ope the,. so the increase flow, you get decreased resistance. because now you’ve opened other chapels that hd been closed so you have a bigger surface area.

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29
Q

explain distension

A

areas that are already open distend, leading to less resistance.

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30
Q

increased blood flow in lungs, decreased

A

pulm vascular resistance

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31
Q

the two mechanisms for the decrease in PVR that occurs as vascular pressures are raised

A

recruitment and distension

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32
Q

pulm arter wedge pressure tells you

A

preload of left side, filling pressure of the left side of the heart

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33
Q

functional capillary volume

A

70ml. 1ml/kg body weight

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34
Q

the average distance an RBC travels through the network is 600 to 800 um

A

600 to 800 um which is a very short ditance

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35
Q

pulmonary capillary network blood volume is equal to

A

RV stroke volume

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36
Q

RBC remain in alveolocapillary network for

A

one cardiac cycle ( .75sec)

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37
Q

RBC require how much time for gas exchange

A

less than .25s (third of cardiac cycle)

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38
Q

in diseased lungs, the curve for gas exchange shifts to the

A

right

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39
Q

total blood volume from main pulm artery to left atrium

A

500ml

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40
Q

how is the pulm vasculature a capacitance reservoir for the LA

A

pulm vasculature can alter its volume from 50% to 200% of resting volume

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41
Q

why is the pulm vasculature altering its volume from 50% to 200% a good thing?

A

its like a buffer so you wont pass out. it prevents changes in blood return to the RV from affecting LV diastolic filling pressures over 2-3 cardiac cycles

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42
Q

capillary bed contains 70ml of blood at rest, and max volume is?

A

200 ml during exercise

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43
Q

increased CO does what to pulm vascular pressures

A

raises

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44
Q

increased CO does what to PVR?

A

decreases

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45
Q

when does recruitment occur

A

during periods of stress and increased tissue 02 demand

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46
Q

when does distention occur

A

high vascular pressures

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47
Q

what can distention lead to

A

lung congestion and heart failure

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48
Q

capillary volume during exercise

A

doubles to give time for adequate gas exchange during increased blood flow

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49
Q

pleural pressure - inspiration

A

greater sub atmospheric (more negative then -5mm H2o)

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50
Q

pleural pressure - exhalation

A

lower pleural pressure gradient (less negative than -5mm h2o)

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51
Q

when lung volume is close to FRC (end of exhalation), PVR is

A

minimal

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52
Q

PVR is increased with

A

higher and lower lung volumes

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53
Q

what do extra-alveolar vessels do during inspiration

A

dilate

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54
Q

what do alveolar vessels do during inspiration

A

compress. pressure drops with each breath

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55
Q

what does mech vent do to alveolar pressure

A

artificially increases

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56
Q

effect of positive pressure ventilation on CO

A

can decrease

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57
Q

effect of positive pressure ventilation on v/q imbalance

A

can increase

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58
Q

bronchial circulation runs from

A

conducting airways to terminal bronchioles

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59
Q

bronchial blood flow is what % of cardiac output

A

1-2%. flows at systemic pressures

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60
Q

50% of bronchial blood circulation returns to

A

RA via azygos vein

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61
Q

what does the pulmonary lymphatic system do

A

keeps alveoli free of fluid moving from capillaries

62
Q

pressure of interstitium

A

slightly negative

63
Q

hydrostatic starling forces move fluid out at

A

20ml/hr

64
Q

there is a net pressure of +1 out of the vessel so what occurs?

A

theres a net leakage of fluid out of the capillary into the interstitum and the lymphatic pump pulls that fluid out and keeps the interstitum free of fluid, allowing gas exchange to occur.

65
Q

two measurement techniques for pulm blood flow

A

fick principle and indicator dilution principle

66
Q

fick principle

A

measurement of arterial and mixed venous blood and determination of 02 consumption

67
Q

V02 at rest is

A

300ml/min

68
Q

indicator dilution principle

A

inject dye into venous circulation, diluted concentration measured on arterial side

69
Q

thermodilution is also used to measure

A

CO

70
Q

in the supine position, arterial pressure is highest where

A

feet

71
Q

the effect of gravity on pulm circulation is

A

greater than systemic. because pulm circulation pressures are much lower.

72
Q

zero reference points

A

RA level and middle of lung

73
Q

supine or prone does what to hydrostatic pressure?

A

minimizes

74
Q

what is hydrostatic pressure

A

the pressure effect gravity has on a column of fluid

75
Q

what part of the lung receives more blood? base or apex

A

base

76
Q

in zone 1, where is pressure the highest

A

alveolar > arterial > venous

77
Q

in zone 1 where is pressure the lowest

A

venous

78
Q

in zone 2 where is pressure the highest

A

arterial > alveolar > venous

79
Q

in zone 3 where is pressure the highest

A

arterial >venous > alveolar

80
Q

whats gas exchange like in zone 1

A

none

81
Q

zone 1 has a higher or lower v/q ?

A

higher

82
Q

you ventilate which parts of your lung more?

A

lower

83
Q

from the top of the lungs down, you have

A

increased blood flow and increased ventilation

84
Q

the perfusion zones in the lung depend on the relationship between

A

alveoli and BP in pulm arteries and veins

85
Q

blood flow in zone 2

A

intermittent “waterfall affect”. with systole, you intermittently have a higher pressure

86
Q

zone 3 blood flow

A

ideal!

87
Q

zone 4

A

abnormal condition of reduced blood flow… high pulm venous pressures.. pulm edema. increased vascular resistance

88
Q

alveoli pressure is higher in the apex of the lung, so

A

less blood flow

89
Q

blood vessels are more distended in which part of the lung

A

base

90
Q

what will shock and hypovolemia do to zone 1perfusion?

A

expand zone 1. because PA pressure is decreased

91
Q

what will PE do to zone 1 perfusion

A

expand zone 1 because blood vessels are occluded

92
Q

what does peep do to zone 1

A

increases

93
Q

how to reduce zone 1

A

increase PA pressure (give blood or fluids), reduce hydrostatic effect by changing position from standing to supine.

94
Q

pulmonary vascular resistance

A

active regulation of blood flow

95
Q

how does PVR regulate

A

active regulation occurs by altering vascular smooth muscle tone in pulm vessels (arterioles)

96
Q

most active regulation of pulmonary vessels is mediated by

A

local metabolic influences

97
Q

motor innervation of pulm vasculature comes from

A

sympathetic branch of ANS. causes vasoconstriction of pulm vessel walls

98
Q

reduced PA02 causes

A

vasoconstriction

99
Q

increased PAO2 causes

A

vasodilation

100
Q

increased PCO2 causes

A

vasoconstriction

101
Q

histamine causes

A

vasoconstriction

102
Q

nitric oxide causes

A

vasodilation

103
Q

thromboxane A2

A

potent vasoconstrictor

104
Q

what does thromboxane A2 work on ?

A

constricts pulm arterial and venous smooth muscle. produced during acute lung tissue damage

105
Q

prostaglandin I2 (prostacyclin)

A

potent vasodilator and inhibitor of platelet activation

106
Q

nitric oxide - vasoconstrictor or vasodilator?

A

potent endothelium-derived endogenous vasodilator

107
Q

does NO have a systemic or localized effect?

A

strictly localized effect

108
Q

NO is formed by L-arginine and leads to

A

smooth muscle relaxation through synthesis of cyclic GMP

109
Q

how does NO (and also sodium nitroprusside) work?

A

guanylyl cyclase, which is responsible for the synthesis of cGMP,

110
Q

what is inhaled NO used for

A

selective pulmonary vasodilation

111
Q

comparison of NO and O2 binding to hemoglobin

A

NO binds to hemoglobin 200,000x > oxygen.

112
Q

is NO better at low concentrations or high

A

low! it is very toxic at high concentrations

113
Q

global reduction in alveolar oxygen tension does what to PVR?

A

increases total PVR by constriction of arterioles and small arteries

114
Q

as alveolar oxygen tension decreases, surrounding arterioles

A

constrict

115
Q

oxygen diffusing into pulm arteriole walls causes smooth muscle

A

dilation

116
Q

alveolar hypoxia produces

A

hypoxic pulmonary vasoconstriction

117
Q

what enhances HPV

A

hypercapnia and acidosis

118
Q

HPV is a localized or systemic response?

A

localized

119
Q

when the systemic circulation is hypoxic, causes ____ but when the pulmonary circulation is hypoxic, causes ____

A

vasodilation, vasoconstriction

120
Q

HPV is an important mechanism of balancing v/q. explain.

A

there is a shift of blood flow to ventilated pulmonary regions. results from decreased formation and release of nitric oxide by pulmonary endothelium in hypoxic region

121
Q

increase PAO2,

A

increase blood flow

122
Q

pulmonary hypertension

A

increased resistance to blood flow in the lung.

123
Q

pulm hypertension causes increased work of breathing for which part of the heart?

A

right ventricle. causing hypertrophy, tricuspid regurgitation, and right heart failure

124
Q

what causes pulm hypertension - high PVR - elevated PA pressures

A

generalized alveolar hypoxia, lung disease, COPD, low inspired PO2, increased PCO2, pain, patient too light, histamine release

125
Q

why is primary pulm hypertension so serious?

A

small muscular pulm arteries narrow, pulm artery pressure increases, RV pressures rise to compensate until occurrence of RV failure, lung transplant only effective treatment

126
Q

tidal volume is distributed evenly or unevenly

A

unevenly!! ventilate base way more than apex in upright lung.

127
Q

what part of the lung are alveoli more expanded?

A

top

128
Q

what part of the lung is compliance greater

A

base

129
Q

what part of the lung is FRC higher

A

top

130
Q

increased resistance and/or decreased compliance indicates

A

longer alveolar filling time

131
Q

why are the PO2 values higher in the top of the lung as opposed to the base?

A

because no gas exchange is occurring so no oxygen is being extracted

132
Q

goal for systemic oxygen partial pressure range

A

85-100mmHg

133
Q

normal A-a P02 differences are

A

10-15mmHg

134
Q

what to larger A-a PO2 gradients indicate?

A

intrinsic pulm disease, shunting.

135
Q

hypoxemia with normal (A-a) PO2 gradient indicates

A

hypoventilation

136
Q

shunt =

A

perfused but not ventilated

137
Q

right to left heart shunt

A

a portion of CO flowing through pulm circulation that doesnt participate in gas exchange. fraction of blood flow bypasses the lung to enter the systemic arteries without becoming oxygenated leading to venous admixtures

138
Q

venous admixture is

A

the blood flow equivalent of wasted ventilation

139
Q

true anatomical shunts

A

bronco pulmonary venous anastomoses, intracardiac thebesian veins, mediastinal veins, pleural veins

140
Q

right to left heart shunt is also known as

A

pulmonary venous admixture

141
Q

left to right heart shunt is also known as

A

pulmonary venous recirculation

142
Q

L to R shunt

A

a portion of the CO returns to the right heart without flowing thru the body. does not affect systemic arterial oxygen tension.

143
Q

L to R shunt

A

a portion of the CO returns to the right heart without flowing thru the body. does not affect systemic arterial oxygen tension.

144
Q

**know recruitment and distension

A

.

145
Q

*** from apex to base, blood flow and ventilation

A

increase

146
Q

***pulmonary vasculature is very

A

distensible and thin

147
Q

*** unique to the lungs - with increased pressure and increased flow you get what effect on resistance

A

decreased resistance

148
Q

** also unique to the lungs, low O2 causes

A

vasoconstriction . hypoxic PV constriction.

149
Q

LV pressure

A

120/10

150
Q

aortic pressure

A

120/80

151
Q

resistance of capillary vessels is reduced by ___ blood flow rates. high or low?

A

high blood flow rates (and low lung volumes)

respiratory physio (12 decks)

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