pulmonary circulation Flashcards
(151 cards)
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
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
3
Q
what is the structure of the pulmonary artery like>
A
this walled (1/3) thickness of aorta) and very compliant
4
Q
RV pressure #
A
25/0-4
5
Q
RA pressure #
A
0-4
6
Q
LA pressure #
A
8-10
7
Q
pulm artery pressure #
A
25/10
8
Q
pulmonary vessels are divided into
A
alveolar and extra alveolar
9
Q
what do alveolar vessels do
A
alveolocapillary network involved in gas exchange. the big capillary bed where gas exchange occurs
10
Q
what collapses alveolar vessels during lung expansion
A
high positive pressure
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
12
Q
are extra-alveolar vessels affected by pressures in lung
A
no
13
Q
do extra-alveolar vessels compress with positive pressure
A
no
14
Q
bronchial vessels
A
oxygenated blood from systemic circulation, 1-2% of cardiac output, empty into left atrium
15
Q
when you take a breath in, what do the alveoli do?
A
squeeze and push on the capillaries and increase resistance
16
Q
???at low lung volumes, vascular resistance is
A
high. because extra-alveolar vessels become narrow
17
Q
???at high lung volumes, resistance is
A
low. because the capillaries are stretched
18
Q
alveolar capillary walls contribute to what % of total resistance
A
40
19
Q
alveolar arterioles contribute what percentage of resistance
A
5
20
Q
in the body, major resistance vessels?
A
arterioles (75%)
21
Q
pulmonary resistance of capillary vessels is reduced by ___ lung volumes. high or low?
A
LOW lung volumes. (and high blood flow rates)
22
Q
resistance of capillary vessels is greater when
A
lower BP or less vascular distending pressures
23
Q
passive regulation of blood flow through capillaries occurs in response to changes in
A
cardiac output
24
Q
increases in blood flow are accommodated by
A
recruitment and distention
25
when arterial ad venous pressure increases, PVR is
decreased
26
recruitment is simply
the opening of previously closed vessels
27
distension is simply
increase in caliber of vessels
28
explain recruitment
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.
29
explain distension
areas that are already open distend, leading to less resistance.
30
increased blood flow in lungs, decreased
pulm vascular resistance
31
the two mechanisms for the decrease in PVR that occurs as vascular pressures are raised
recruitment and distension
32
pulm arter wedge pressure tells you
preload of left side, filling pressure of the left side of the heart
33
functional capillary volume
70ml. 1ml/kg body weight
34
the average distance an RBC travels through the network is 600 to 800 um
600 to 800 um which is a very short ditance
35
pulmonary capillary network blood volume is equal to
RV stroke volume
36
RBC remain in alveolocapillary network for
one cardiac cycle ( .75sec)
37
RBC require how much time for gas exchange
less than .25s (third of cardiac cycle)
38
in diseased lungs, the curve for gas exchange shifts to the
right
39
total blood volume from main pulm artery to left atrium
500ml
40
how is the pulm vasculature a capacitance reservoir for the LA
pulm vasculature can alter its volume from 50% to 200% of resting volume
41
why is the pulm vasculature altering its volume from 50% to 200% a good thing?
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
42
capillary bed contains 70ml of blood at rest, and max volume is?
200 ml during exercise
43
increased CO does what to pulm vascular pressures
raises
44
increased CO does what to PVR?
decreases
45
when does recruitment occur
during periods of stress and increased tissue 02 demand
46
when does distention occur
high vascular pressures
47
what can distention lead to
lung congestion and heart failure
48
capillary volume during exercise
doubles to give time for adequate gas exchange during increased blood flow
49
pleural pressure - inspiration
greater sub atmospheric (more negative then -5mm H2o)
50
pleural pressure - exhalation
lower pleural pressure gradient (less negative than -5mm h2o)
51
when lung volume is close to FRC (end of exhalation), PVR is
minimal
52
PVR is increased with
higher and lower lung volumes
53
what do extra-alveolar vessels do during inspiration
dilate
54
what do alveolar vessels do during inspiration
compress. pressure drops with each breath
55
what does mech vent do to alveolar pressure
artificially increases
56
effect of positive pressure ventilation on CO
can decrease
57
effect of positive pressure ventilation on v/q imbalance
can increase
58
bronchial circulation runs from
conducting airways to terminal bronchioles
59
bronchial blood flow is what % of cardiac output
1-2%. flows at systemic pressures
60
50% of bronchial blood circulation returns to
RA via azygos vein
61
what does the pulmonary lymphatic system do
keeps alveoli free of fluid moving from capillaries
62
pressure of interstitium
slightly negative
63
hydrostatic starling forces move fluid out at
20ml/hr
64
there is a net pressure of +1 out of the vessel so what occurs?
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
two measurement techniques for pulm blood flow
fick principle and indicator dilution principle
66
fick principle
measurement of arterial and mixed venous blood and determination of 02 consumption
67
V02 at rest is
300ml/min
68
indicator dilution principle
inject dye into venous circulation, diluted concentration measured on arterial side
69
thermodilution is also used to measure
CO
70
in the supine position, arterial pressure is highest where
feet
71
the effect of gravity on pulm circulation is
greater than systemic. because pulm circulation pressures are much lower.
72
zero reference points
RA level and middle of lung
73
supine or prone does what to hydrostatic pressure?
minimizes
74
what is hydrostatic pressure
the pressure effect gravity has on a column of fluid
75
what part of the lung receives more blood? base or apex
base
76
in zone 1, where is pressure the highest
alveolar > arterial > venous
77
in zone 1 where is pressure the lowest
venous
78
in zone 2 where is pressure the highest
arterial > alveolar > venous
79
in zone 3 where is pressure the highest
arterial >venous > alveolar
80
whats gas exchange like in zone 1
none
81
zone 1 has a higher or lower v/q ?
higher
82
you ventilate which parts of your lung more?
lower
83
from the top of the lungs down, you have
increased blood flow and increased ventilation
84
the perfusion zones in the lung depend on the relationship between
alveoli and BP in pulm arteries and veins
85
blood flow in zone 2
intermittent "waterfall affect". with systole, you intermittently have a higher pressure
86
zone 3 blood flow
ideal!
87
zone 4
abnormal condition of reduced blood flow... high pulm venous pressures.. pulm edema. increased vascular resistance
88
alveoli pressure is higher in the apex of the lung, so
less blood flow
89
blood vessels are more distended in which part of the lung
base
90
what will shock and hypovolemia do to zone 1perfusion?
expand zone 1. because PA pressure is decreased
91
what will PE do to zone 1 perfusion
expand zone 1 because blood vessels are occluded
92
what does peep do to zone 1
increases
93
how to reduce zone 1
increase PA pressure (give blood or fluids), reduce hydrostatic effect by changing position from standing to supine.
94
pulmonary vascular resistance
active regulation of blood flow
95
how does PVR regulate
active regulation occurs by altering vascular smooth muscle tone in pulm vessels (arterioles)
96
most active regulation of pulmonary vessels is mediated by
local metabolic influences
97
motor innervation of pulm vasculature comes from
sympathetic branch of ANS. causes vasoconstriction of pulm vessel walls
98
reduced PA02 causes
vasoconstriction
99
increased PAO2 causes
vasodilation
100
increased PCO2 causes
vasoconstriction
101
histamine causes
vasoconstriction
102
nitric oxide causes
vasodilation
103
thromboxane A2
potent vasoconstrictor
104
what does thromboxane A2 work on ?
constricts pulm arterial and venous smooth muscle. produced during acute lung tissue damage
105
prostaglandin I2 (prostacyclin)
potent vasodilator and inhibitor of platelet activation
106
nitric oxide - vasoconstrictor or vasodilator?
potent endothelium-derived endogenous vasodilator
107
does NO have a systemic or localized effect?
strictly localized effect
108
NO is formed by L-arginine and leads to
smooth muscle relaxation through synthesis of cyclic GMP
109
how does NO (and also sodium nitroprusside) work?
guanylyl cyclase, which is responsible for the synthesis of cGMP,
110
what is inhaled NO used for
selective pulmonary vasodilation
111
comparison of NO and O2 binding to hemoglobin
NO binds to hemoglobin 200,000x > oxygen.
112
is NO better at low concentrations or high
low! it is very toxic at high concentrations
113
global reduction in alveolar oxygen tension does what to PVR?
increases total PVR by constriction of arterioles and small arteries
114
as alveolar oxygen tension decreases, surrounding arterioles
constrict
115
oxygen diffusing into pulm arteriole walls causes smooth muscle
dilation
116
alveolar hypoxia produces
hypoxic pulmonary vasoconstriction
117
what enhances HPV
hypercapnia and acidosis
118
HPV is a localized or systemic response?
localized
119
when the systemic circulation is hypoxic, causes ____ but when the pulmonary circulation is hypoxic, causes ____
vasodilation, vasoconstriction
120
HPV is an important mechanism of balancing v/q. explain.
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
increase PAO2,
increase blood flow
122
pulmonary hypertension
increased resistance to blood flow in the lung.
123
pulm hypertension causes increased work of breathing for which part of the heart?
right ventricle. causing hypertrophy, tricuspid regurgitation, and right heart failure
124
what causes pulm hypertension - high PVR - elevated PA pressures
generalized alveolar hypoxia, lung disease, COPD, low inspired PO2, increased PCO2, pain, patient too light, histamine release
125
why is primary pulm hypertension so serious?
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
tidal volume is distributed evenly or unevenly
unevenly!! ventilate base way more than apex in upright lung.
127
what part of the lung are alveoli more expanded?
top
128
what part of the lung is compliance greater
base
129
what part of the lung is FRC higher
top
130
increased resistance and/or decreased compliance indicates
longer alveolar filling time
131
why are the PO2 values higher in the top of the lung as opposed to the base?
because no gas exchange is occurring so no oxygen is being extracted
132
goal for systemic oxygen partial pressure range
85-100mmHg
133
normal A-a P02 differences are
10-15mmHg
134
what to larger A-a PO2 gradients indicate?
intrinsic pulm disease, shunting.
135
hypoxemia with normal (A-a) PO2 gradient indicates
hypoventilation
136
shunt =
perfused but not ventilated
137
right to left heart shunt
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
venous admixture is
the blood flow equivalent of wasted ventilation
139
true anatomical shunts
bronco pulmonary venous anastomoses, intracardiac thebesian veins, mediastinal veins, pleural veins
140
right to left heart shunt is also known as
pulmonary venous admixture
141
left to right heart shunt is also known as
pulmonary venous recirculation
142
L to R shunt
a portion of the CO returns to the right heart without flowing thru the body. does not affect systemic arterial oxygen tension.
143
L to R shunt
a portion of the CO returns to the right heart without flowing thru the body. does not affect systemic arterial oxygen tension.
144
**know recruitment and distension
.
145
*** from apex to base, blood flow and ventilation
increase
146
***pulmonary vasculature is very
distensible and thin
147
*** unique to the lungs - with increased pressure and increased flow you get what effect on resistance
decreased resistance
148
**** also unique to the lungs, low O2 causes
vasoconstriction . hypoxic PV constriction.
149
LV pressure
120/10
150
aortic pressure
120/80
151
resistance of capillary vessels is reduced by ___ blood flow rates. high or low?
high blood flow rates (and low lung volumes)
