Pulmonary Circulation

Front 1

Main pulmonary artery extends from?

Back 1

the right ventricle

Front 2

Main pulmonary artery receives?

Back 2

mixed venous blood pumped by the right ventricle

Front 3

The main pulmonary artery divides into?

Back 3

the left and right pulmonary branches which supply the left and right lungs, respectively

Front 4

Describe the pulmonary arterial system

Back 4

Successive branching of arteries into progressively smaller vessels

Front 5

Pulmonary arteries follow the?

Back 5

tracheobronchial segmentation (airway branching) down to the terminal bronchioles

Front 6

The pulmonary arteries are ___-________ vessels with relatively _______ diameters and little smooth muscle (compared with arteries in the systemic circulation)

Back 6

thin-walled, large

Front 7

Does the pulmonary arterial system have a high compliance?

Back 7

yes and thus can accomodate the right ventricle stroke volume with a relatively small change in pressure

Front 8

Pulmonary capillaries

Back 8

dense network of vessels in the alveolar walls- "sheet" of blood

Front 9

Pulmonary venous system transports...

Back 9

oxygenated blood to the left atrium; four main veins empty into the left atrium

Front 10

Pulmonary veins have a _______ function.

Back 10

reservoir

Front 11

What does this reservoir function do?

Back 11

distention can minimize an increase in pulmonary capillary pressure and help to prevent pulmonary edema in the event of impaired left-ventricular function

Front 12

Lymphatic system begins with?

Back 12

blind-ended lymphatic capillaries that orginiate in the interstitial space of the lung

Front 13

What do lymphatic capillaries continually remove?

Back 13

fluid, protein, and foreign particles (even bacteria) from the lung interstitium

Front 14

Lymph flow is ultimately directed to?

Back 14

the right lymphatic duct and from there to the venous side of the systemic circulation

Front 15

What are the pulmonary artery pressures (at level of the heart)?

Back 15

Systolic pressure= 25 mmHg (same as right ventricle)
Diastolic pressure = 8 mmHg
Mean pulmonary arterial pressure = 15 mmHg
Pulse pressure = 17 mmHg

Front 16

The low pressures in the pulmonary arterial system are consistent with? (2)

Back 16

1. Properties of the right ventricle -- low pressure chamber
2. Properties of the pulmonary arteries -- thin-walled, large-diameter, high compliance vessels

Front 17

There are ______ differences in pulmonary arterial pressures due to _______ pressure

Back 17

regional, hydrostatic

Front 18

What is pulmonary capillary pressure estimated to be?

Back 18

about 7 mmHg at the level of the heart

Front 19

Are there regional differences that exist in the lung due to hydrostatic pressure?

Back 19

yes

Front 20

Blood pressure in the pulmonary veins is nearly the same as?

Back 20

pressure in the left atrium and is similiar to LVEDP

Front 21

Pulmonary artery wedge pressure (PAWP) or PAOP can measure?(3)

Back 21

pulmonary venous pressure, left atrial pressure and LVEDP

Front 22

Changes in LVEDP and left atrial pressure usually parallel changes in?

Back 22

PAWP

Front 23

What is the effect of left-side heart failure on pulmonary pressures?

Back 23

modest increases in left atrial pressure have little effect on pulmonary arterial and capillary pressure due to pulmonary venous dilation and pulmonary capillary recruitment

Front 24

Large increases in ____ ______ pressure can exponentially increase pulmonary artery pressure and pulmonary capillary pressure.

Back 24

left atrial

Front 25

Pulmonary edema is likely when left atrial pressure rises above?

Back 25

25-30 mmHg

Front 26

PVR, overall it is?

Back 26

very low, about 1/10 that of systemic vascular resistance

Front 27

The pulmonary circulation does not have?

Back 27

highly muscular arterioles (resistance vessels) as occur in the systemic circulation

Front 28

PVR is determined primarily by?

Back 28

passive factors

Front 29

What passive factors affect PVR?

Back 29

pulmonary arterial and venous blood pressures and lung volume

Front 30

What decreases PVR? And why?

Back 30

an increase in pulmonary arterial or venous blood pressure, through distension and recruitment of pulmonary capillaries

Front 31

What increases PVR?

Back 31

Decrease in pulmonary arterial or venous pressure

Front 32

The relationship between lung volume and pulmonary vascular resistance is shown by what type of curve?

Back 32

J-shaped (U-shaped) curve

Front 33

The influence of lung volume on PVR is __________ at FRC.

Back 33

minimal

Front 34

What occurs at lung volumes above FRC?

Back 34

compression of alveolar capillaries, increasing their resistance

Front 35

How can this increased resistance be partially offset?

Back 35

by a decrease in resistance of extra-alveolar vessels (eg, small arteries, veins) caused by lung expansion

Front 36

This offset of resistance allows for the total PVR?

Back 36

to increase relative to that of FRC

Front 37

At low lung volumes below FRC, what happens with the extra-alveolar vessels?

Back 37

the caliber of these vessels decreases due to less traction exerted by surrounding lung tissue, thereby increasing their resistance and total PVR relative to that at FRC

Front 38

At rest, the lungs contain _____ of blood?

Back 38

450 mL (about 9% of the total blood volume)

Front 39

Of the 450 mL of blood in the lungs, what amount is contained in the pulmonary capillaries?

Back 39

70mL

Front 40

Since the lungs can function as a significant blood reservoir; loss of blood from the systemic circulation can be?

Back 40

compensated

Front 41

How can this loss of blood be compensated?

Back 41

by a shift of blood from the pulmonary circulation into the systemic circulation (sympathetic-mediated pulmonary venous constriction)

Front 42

What conditions can greatly increase pulmonary blood volume and also pulmonary vascular pressures?

Back 42

left heart failure or mitral valve dysfunction (stenosis; regurgitation)

Front 43

Total blood flow is essentially the?

Back 43

cardiac output

Front 44

For the most part the pulmonary vessels behave as ______, distensible tubes that....

Back 44

passive, enlarge with increasing vascular pressure and narrow with decreasing pressure

Front 45

T or F. PVR is largely passive

Back 45

True

Front 46

What factors can actively increase pulmonary blood vessel tone and resistance, and thus influence pulmonary blood flow distribution?

Back 46

1. Hypoxic pulmonary vasoconstriction (HPV)
2. Autonomic nervous system

Front 47

Hypoxic pulmonary vasoconstriction (HPV)

Back 47

if ALVEOLAR P02 is reduced (less than 70mmHg) due to insufficient ventilation of a lung region, contraction of smooth muscle occurs in small arterioles in the hypoxic area, reducing blood flow to the area

Front 48

In HPV, what do the mechanisms of vasoconstriction not depend on? (2)

Back 48

1. Does not depend on nervous input- occurs in an isolated lung
2. Does not depend on a drop in arterial P02-- occurs when arterial P02 is kept high, despite low alveolar P02

Front 49

In HPV, what is thought to be a mechanism of vasoconstriction?

Back 49

It is thought that the mitochondrial electron transport chain in arteriolar smooth muscle cells may be the PA02 sensor; release of reactive oxygen molecules may mobilize calcium for vasoconstriction

Front 50

Function of HPV

Back 50

Diversion of blood flow away from poorly ventilated alveoli to areas that are better ventilated -- mechanism to avoid ventilation-perfusion mismatch and possible hypoxemia

Front 51

What is the function of HPV in the fetal circulation?

Back 51

PVR is normally very high in the fetus, partly because of hypoxic vasoconstriction; when the alveoli are oxygenated with the first few breaths after birth, alveolar P02 rises and vascular resistance decreases substantially

Front 52

What is the ANS contribution to pulmonary blood flow?

Back 52

little influence on pulmonary arterial resistance--the pulmonary arteries do have alpha and beta adrenergic receptors though

Front 53

In some cases, the sympathetic nervous system can strongly constrict the pulmonary...

Back 53

veins and displace blood to the systemic circulation (eg, hemorrhage or shock)

Front 54

What other factors can actively increase pulmonary blood vessel tone and resistance? (3)

Back 54

1. Hypercapnia and acidemia cause pulmonary vasoconstriction and enhance HPV
2. Vasoconstrictors: serotonin, leukotrienes
3. Vasodilators: nitroprusside, nitric oxide, calcium channel blockers

Front 55

Can the effects of hydrostatic pressure affect pulmonary blood flow distribution?

Back 55

yes

Front 56

In a column of blood, hydrostatic pressure occurs at any level due to the _____ of the blood above that level.

Back 56

weight

Front 57

P (cm H20) = height of the column in cm; thus a column of blood 100 cm in height has a hydrostatic pressure of?

Back 57

100 cm H20 at its base (100 cm H20= 73.5 mmHg)

Front 58

The pulmonary circulation can be viewed as a column of blood extending from?

Back 58

apex to base of the upright lung

Front 59

In the adult lung, the distance from apex to base is?

Back 59

about 30 cm, thus a hydrostatic pressure difference of 30 cm H20 (23 mmHg) exists between the apex and the base of the upright lung

Front 60

How much of the apex-to-base difference in mmHg lies above the level of the heart?

Back 60

15

Front 61

How much difference lies below the heart?

Back 61

8mmHg

Front 62

At the apex, what is the systolic, diastolic and mean pulmonary artery pressures?

Back 62

systolic: 10
diastolic: -7
mean: -1.3

Front 63

At the heart, what is the systolic, diastolic and mean pulmonary artery pressures?

Back 63

systolic: 25
diastolic: 8
mean: 15

Front 64

At the base what is the systolic, diastolic and mean pulmonary artery pressures?

Back 64

systolic: 33
diastolic: 16
mean: 22

Front 65

In the upright lung, blood flow is greatest in the ____ and least in the _____.

Back 65

base, apex

Front 66

Uneven distribution of pulmonary blood flow can be referred to as?

Back 66

Zones (west) of pulmonary perfusion

Front 67

Pulmonary capillaries are distended by?

Back 67

internal blood pressure

Front 68

Pulmonary capillaries are also subject to?

Back 68

compression by surrounding alveolar pressure

Front 69

For blood flow to occur in a region of the lung, what must occur?

Back 69

Pcap must exceed Palv

Front 70

Zone 1:

Back 70

No blood flow, Palv>Pcap

Front 71

Zone 2

Back 71

Pcap>Palv during systole --- blood flow occurs; Palv>Pcap during diastole---no blood flow, therefore zone 2 blood flow is intermittent

Front 72

Zone 3

Back 72

Pcap>Palv at all times; continuous blood flow

Front 73

Normally the lungs only have what zones of flow while a person is sitting or standing?

Back 73

zone 2 and 3

Front 74

In the supine position, what happens?

Back 74

Zone 3 blood flow occurs in all parts of the lung

Front 75

When may Zone 1 flow occur in the lung apex?

Back 75

when Palv is increased (eg, positive pressure ventilation) and/or when pulmonary arterial blood pressure is decreased (eg, hypovolemia)

Front 76

Zone 1 flow creates?

Back 76

alveolar dead space

Front 77

Ideally, where should the tip of the pulmonary artery catheter be?

Back 77

in zone 3 to measure LVEDP