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Respiratory > Pulmonary and bronchial circulation > Flashcards

Pulmonary and bronchial circulation Flashcards

Flash cards comprise Kam power/Deranged physiology and Wests. Only the first 3 pages of Nunns chapter included

1
Q

Mean pulmonary artery pressure? Pulmonary trunk diametre?

A

15mmHg or 20cmH20 (25/10) = 1/6 of mean systemic arterial pressure
30mm

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2
Q

Mean pulmonary arteriole pressure

A

12

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3
Q

Mean pulmonary vein pressure

A

8

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4
Q

RV pressure

A

25/0

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5
Q

RA pressure

A

2

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6
Q

LV pressure

A

120/0

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7
Q

LA pressure

A

5

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8
Q

Mean systemic arterial pressure

A

100 120/80

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9
Q

Mean systemic veinous pressure

A

5-10

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10
Q

Mean systemic arteriole pressure

A

30

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11
Q

Mean systemic capillary pressure

A

20

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12
Q

Mean systemic venule pressure

A

10

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13
Q

Why is there a more pronounced pressure drop in the systemic circululation than in the pulmonary circulation?

A
  1. Muscular arteriole mediated blood flow regulation at entrance to organs leading to profound pressure drop across capillary system in systemic circulation
  2. Pulmonary artery shorter, thinner walled more distensible than the aorta ith less smooth muscle
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14
Q

Define vascular resistance

A

Flow = pressure / resistance

Resistance = flow/pressure

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15
Q

How are the pulmonary and systemic arterial systems different? Show this mathematiucally?

A

Identical flow
Pressure drop across pulmonary circulation (mean values) 15 - 5 = 10mmHg
In systemic circulation drop is 100-5 = 95mmHg
Therefore MUCH higher systemic vascular resistance

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16
Q

What pressures are the capillaries exposed to in the pulmonary system?

A
  1. Alveolar pressure - if alveolar pressure is higher than capillary pressure then the capillaries collapse
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17
Q

What is the difference in thw walls of the BV system between the pulmonary and systemic?

A

Pulmonary blood vessels markedly thinner

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18
Q

How to tell the difference on a microscope between a vein and an artery in the lung?

A

Veins are not accompanied by airways, whereas arteries are accompanied by arteries especially more distally; arteries and airways travel down the centre of lobules whereas veins travel down the peripheries of lobules

There is however not much difference in their thickness, but generaly veins are fewer in numbre, thinner walls, less muscular, less elastic and more collagenous. Interestingly pulmonary veins drain seamlessley into the LA with no fold/border. At their largest half the width of pulmonary arteries

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19
Q

How is the path different between a vein and an artery in the lung?

A

Veins are not accompanied by airways, whereas arteries are accompanied by arteries

There is however not much difference in their thickness

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21
Q

How is the pressure different between arteries/veins and capillaries in the lung?

A

Alveolar capillaries - these are compressed between alveoli by alveolar pressure
Pulmonary vein and arteries - extra-alveolar vessels therefore the alveoli/lung parenchyma pull on the veins and arteries as they expand

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21
Q

Alveolar vs extra-alveolar vessels? Whats the difference? How do their calibres change with inspiration and expiration?

A

Inspiration/expansion of lung volume - increased alveolar resistance, however reduced pulmonary vein/artery resistance
The inverse with expiration

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22
Q

What is the resistance equation

A

Resisatnce = input pressure - output pressure/flow

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23
Q

What is the difference between vascular and electrical resistance?

A

Resistance does not change depending on upstream and downstream pressure in electrical systems; HOWEVER physiologically the pressure changes do change the resistance in the lung

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24
Q

Draw a diagram equating pulmonary vascular resistance with arterial or veinous pressure? Give units? Why does this relationship occur? (2) HOw elastic is the pulmonary capillary?

Now draw another diagram describing the relationship between PVR and lung volume? Explain the trends? Explain the different effects on vessels in different areas that explain this? Where is the normal scope of breathing on these diagrams?

A
  1. Recruitment of capillaries with increasing flow
  2. Distension of existing capillaries with increasing flow reducing their resistance

Baseline flow is not enough to distend to maximal diametre as partial collapse; highly elastic thinner walled vessels with less muscle

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25
Q

What is the Fick principles

A

VO2 = CO (CaO2 - CvO2)

Volume of oxygen going into the lung, is equal to the amount removed by pulmonary blood flow which is equal to Ca O2 - CvO2

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26
Q

Rearranging the Fick principle for CO =

A

CO = VO2 / (CaO2 - CvO2)

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27
Q

How do you measure the cardiac output in order to calculate VO2?

A

Catheter in pulmonary artery
Arterial blood sample
Mixed veinous blood sample

Other methods - dye dilution, thermal dilution

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28
Q

Distribution of blood when upright? Draw a diagram describing this relationship for sitting up, supine and seated? Why is supine not straight?

How was this relationship derived? What i blood flow at the apex of the lung when upright? On exercise how does this change? What effect does reduced pulmonary arterial pressure have on standing curve? What point corresponds to no blood flow? What point corresponds to a change in gradient?

A

Radioactive xenon with breath hold and emission

Apex of upright lung under normal conditions has barely any blood flow

It is affected by change of posture

Exercise both basal and apical increase, fractional differences between areas of the lung becomes less

Reducing pulmonary artery pressure exacerbates this difference, and flow stops at the top where arterial = alveolar pressure. Much more flow at the bottom.

Raising pulmonary veinous pressure increases flow in the middle zone where veinous > alveolar, but in the middle zone it still drops to zero once arterial < alveolar

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29
Q

What is the 3 zone description of blood flow? Which are present under normal conditions? When do they become apparant?

A

The pulmonary arterial pressure is just sufficient for zone 1 not to exist - if you had a haemorrhage and decreased pulmonary arterial pressure then you may have zone 1; or if positive pressure ventilation you may induced zone 1.

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30
Q

What does the flow depend on in West Zone 2? What model is used to explain this? Why does blood flow increase as you progress down/descend?

A

Zone 2 = Pa > Palveolar > P veinous
Blood flow dependent on arterial - alveolar pressure (not veinous). Acting as a starling resistor where capillaries collapse

Blood flow increases due to gravity increasing Pa and Pv above Palveolar which is constant throughout the lung

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31
Q

Non gravitational causes of uneven blood flow in the lung (3)

A

Random variation sin resistance of vessels
Proximal acinus receive more blood flow than distal regions
Some regions have intrinsically higher resistance

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32
Q

What factors determine pulmonary blood flow?

A
  1. Lung volume
  2. Gravitational forces
  3. Cardiac output
  4. FiO2
  5. PaCO2
  6. pH
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33
Q

What effect does FiO2 have on pulmonary artery pressure? Draw a diagram of blood flow vs alveolar PaO2? Over what range does it mostly change?

A

Reduced Fio2 increases mean pulmonary artery pressure, reducing flow. This is hypoxic mediated pulmonary vasoconstriction

Maximum change between PaO2 50 - 150; steepest gradient below 50mmHg

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34
Q

Where does the response to alveolar PaO2 and blood flow get controlled? How does alveolar gas affect this because pulmonary blood has not yet exchanged? What channel is important? What can inhibit this mechanism? Pulmonary blood flow in the foetus is what proportion of cardiac output? What is PVR so high?

A

Pulmonary artery - as the artery is next to the airway and alveoli, via diffusion alveolar gas moves across into pulmonary artery. Vascular smooth muscle - voltage gated pottasium channels; and nitric oxide inhibits this process.

15%
PVR is so high because the lung has no oxygen coming through it

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35
Q

Metabolic functions of the lung?
- Activation of (1)
- Inactivation of (4)
- Metabolism of and released (2)
- Secretion of (1)

A

AT2 activation
Inactivation - bradykinin, serotonin, PGE1/2, F2, NA
Adrenaline, AT2 and vasopressin NOT affected
Metabolism of and released - LT and PG (AA metabolism)
Secretion of - IgA in bronchial mucous

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36
Q

PART 2

(already answered) Draw a diagram equating pulmonary vascular resistance with arterial or veinous pressure? Give units? Why does this relationship occur? (2) HOw elastic is the pulmonary capillary?

Now draw another diagram describing the relationship between PVR and lung volume? Explain the trends? Explain the different effects on vessels in different areas that explain this? Where is the normal scope of breathing on these diagrams?

A

Low lung volumes = loss of extraalveolar vessel radial traction causing partial collapse and vascular resistance rises

At high lung volumes it also causes increasing resistance likely due to high tension from extralaveolar vessel assymetric application of distension causing distortion of the vessel in a way that increases resistance

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37
Q

Draw a diagram describing pulmonary blood flows relationship to posture for sitting up, supine and seated? Why is supine not straight?

A

Apical blood flow higher when lying down because of the orientation of the lung is not horizontal it is instead slightly head down when lying flat. Blood flow is more uniform however

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38
Q

What is the effect of increased pulmonary veinous pressure on blood flow in relation to vertical distance in the lung in a seated patient - draw a diagram to reflect this

A
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39
Q

Why does blood flow increase as you descend in the lung within zone 3? Gravitational forces should be equal in their effect on Arterial and Veinous should they not?

A

Gravitational forces are equal but because the raw pressures are higher recruitment and distension is maximised leading to lower resistance and higher flow

40
Q

Dividing pulmonary arteries into 3 subdivisions which are

A

Elastic large
Muscular small - vasoreactive
Non muscular smallest - intra-acinar affected by alveolar pressure

41
Q

What is in a bronchovascular bundle?

A

Extensinos fo the visceral pleura

Bronchi, nerves, lymphatics, pulmonary arteries and bronchial artery +/- pulmonary vein (proximal are separate, closer to the airway are part of the bundle but the vein is somewhat apart in the interlobular septa)

42
Q

Where do pulmonary capillaries start with reference to airway anatomy>

A

terminal bronchioles forming a vascuar sheet interrupted by intercapillary posts

43
Q

Bronchial circulation arises from?

A

Systemic circulation
Right bronchial artery from an intercostal artery
Left bronchial artery usually two arties with separate origins from the aorta

44
Q

How much of the venous bronchial blood drains back into systemic circulation?

A

1/3 –> via azygous and hemiazygous veins
The rest forms a physiological shunt

45
Q

3 sources of blood the pulmonary artery receives

A

Deoxygenated systemic blood
Deoxygenated bronchial blood - 1/3 of bronchial circulation
Oxygenated arterial blood from bronchial circulation via Sperr arteries

46
Q

4 sources of pulmonary veinous blood

A

Oxygenated venous blood from pulmonary capillaries
Deoxygenated blood from intrapulmonary shunting
Deoxygenated blood from bronchial circulation 2/3 of bronchial drainage
Deoxygenated venous blood from Thebesian circulation 0.5mm in diametre

47
Q

Innervation of pulmonary vessels

A

SNS > PSNS

48
Q

4 Function of the pulmonary circulation

A
  1. Gas exchange
  2. Blood filter
  3. Blood reservoir - 500ml as a high capacitance
  4. Metabolic - metabolism of noradrenaline, PG, bradykinin, seratonin; activation of angiotensin; production of LT and PG
49
Q

Describe the distribution of blood stored in the pulmonary circulation

A

150ml in arteries
80ml in capillaries
250ml in veinous

50
Q

Surface area for gas exchange

A

50-70m^2

51
Q

What % of circulation goes to the bronchial circulation

A

1%

52
Q

Which ventricle has slightly higher cardiac output?

A

LV due to bronchial physiological shunt of blood

53
Q

Mean pulmonary capillary pressure

A

10

54
Q

What difference in hydrostatic pressure do you find between the apex and the base of the lung when upright?

A

Base 10mmHg more than pulmonary artery mean (25mmHg mean); and apex vice versa

55
Q

Explain what pressures the circulation is subjected to in the apex of a normal uprgiht lung?

A

Pulmonary blood - 5mmHg mean (15/5 to 10/0)
Alveolar pressure 0 +/- 1 cmH20 but can be much higher in PPV

56
Q

Where does zone 2 start in the upright lung relative to the heart?

A

Apex down to 10cm above the level of the heart

57
Q

Where does zone 3 start and end in the normal heart?

A

10 above the level of the heart to the base

58
Q

What is zone 4

A

Interstitial pressure > alveolar and veinous pressure

Reduced blood flow in most dependent regions

59
Q

What passive factors affect pulmonary vascular resistance?

A
  1. Distension and recruitment - resistance decreases as flow increases (mostly passive distension)
  2. Lung volume - vascular resistance lowest at FRC
  3. Gravity
60
Q

How is pulmonary capillary flow different to systemic blood flow

A

Pulsatile as minimal dampening of pressure waveform

61
Q

What is normal pulmonary vascular resistance?

A

150-200 dynes/sec/cm^5 (1/10 of systemic vascular resistance)

62
Q

Pulmonary vascular resistance primarily comes from arteries, veins or capillaries?

A

Evenly spread
Unlike systemic vascular resistance which primarily comes from arterioles

63
Q

What active factors regulate pulmonary vascular resistance

A
  1. Autonomic control - SNS (density of receptors less than systemic vessels); vagal muscurinic supply
  2. Hypoxic pulmonary vasocontriction - mainly at arterial pre-capillary vessels close to alveoli and with prolonged hypoxia is biphasic with rapid change in first 5 minutes, with second phase of activity 40 minutes later with maximal response at 2-4 hours. This is augmented by acidosis
  3. Alveolar hypercapnoea causes vasoconstriction
  4. Humeral - catecholamines, thromboxane and LT vasoconstrict, PGI2 vasodilates, seratonin vasoconstricts
  5. Drugs - nitric oxide vasodilates, nebulised prostacyclin vasodilates, phosphodiesterase inhibits inhibit cGMP breakdown and cAMP causing vasodilation. As does milrinone, levosimendan, sildanafil and volatile anaesthetics
64
Q

Describe the phases of pulmonary hypoxic vasoconstriction?

A

mainly at arterial pre-capillary vessels close to alveoli and with prolonged hypoxia is biphasic with rapid change in first 5 minutes, with second phase of activity 40 minutes later with maximal response at 2-4 hours

65
Q

Mediators of hypoxic pulmonary vasoconstriciton?

A

Low alveolar PO2 nd less extent mixed veinous PO2

66
Q

How does hypoxic pulmonary vasoconstriction occur?

A

First phase - voltage gated K channels (outward K current)
Second phase 0 endothelin with reduction in endothelial nitric oxide synthesis when PO2 below 70mmHg

67
Q

What factors augment hypoxic pulmonary vasoconstriction

A

Metabolic and respiratory acidosis

68
Q

What is the diametre of a pulmonary capillary

A

7-10microm

69
Q

Blood gas interface thickness

A

0.2 - 0.3micrometre

70
Q

How much time does each RBC spend in the acpillary network?

A

0.75 seconds

71
Q

Is recruitment or distension more important to reduction in vascular resistance with increased pressure or flow

A

At low vascular pressures recruitment is more important

At high vascular pressures distension is more important

72
Q

Units of resistance

A

cmH20 / L /min
mmHg/L/min
Dynes.sec/cm^5

73
Q

Give 4 pulmonary vasoconstricotrs

A

Endothelin
Noradrenaline/adrenaline
Seratonin
Thromboxane
Histamine

74
Q

Give 5 pulmonary vasodialtors

A

Nitric oxide
PGI2
Phosphodiesterase inhibitors
ACh
CaB

75
Q

What is the relationship of blood flow to distance above and below the heart in the upright lung

A

linear

76
Q

Colloid osmotic pressure in pulmonary vessels

A

25-28mmHg

77
Q

Colloid osmotic pressure in lung interstitium?

A

17-20mmHg

78
Q

What is the normal lymph flow in the lung per hour?

A

20ml/hr

79
Q

Where is ACE found in the lung

A

capillary endothelial cells in smalll pits

80
Q

What % of overall bradykinin is metabolised i the lung

A

80%

81
Q

What is an example of an amine?

A

seratonin, norepinephrine, hsitamine, dopamine

82
Q

What are peptides processed in the lung

A

angiotensin 1 and bradykinine

83
Q

How is the pulmonary blood volume affected by going from supine to erect

A

Decreases pulmonary blood volume by a third

84
Q

What is the difference between intravascular pressure, transmural pressure and driving pressure

A

Intravascular pressure - is the pressure at any one point relative to the atmosphere

Transmural pressure - difference in pressure between inside of a vessel and tissue surrounding the vessel

Driving pressure is the difference between one poin tin the circulation and another point downstream

85
Q

Intrathoracic pressure is related to alveolar pressure how

A

Intrathoracic pressure = alveolar pressure - alveolar transmural pressure

86
Q

How is the anatomical location of early pulmonary oedema explained

A
  • Pulmonary arteries and veins travel with bronchi, nerves and lymphatics in bronchovascular bundles, which are extensions of the visceral pleura
    ◦ The clinical relevance of these structures is the tendency of oedema fluid to accumulate in them, creating “peribronchial cuffing”
87
Q

What % of the pulmonary capillary bed is filled at baseline

A

◦ 75% of the capillary bed is filled at baseline with gravity dependent variation

88
Q

Give the pressures within the pulmonary circulation

A

◦ PA systolic pressure = 18-25 mmHg
◦ PA diastolic pressure = 8-15 mmHg
◦ Mean pulmonary arterial pressure = 9-16 mmHg
◦ Pulmonary capillary pressure = 8-10mmHg
◦ Pulmonary venous pressure = 6-12 mm Hg

89
Q

What physiological factors affect pulmonary arterial pressure

A

Flow = pressure/resistance
Pressure = flow x resistance

Flow is cardiac output therefore can describe the factors determining this

Resistance hagen poiseulle

Radius is afected by
◦ Blood flow
◦ Lung volume
◦ Hypoxic pulmonary vasoconstriction - most effected by alveoalr hypoxia, PaO2 <70mmHg causes closure of hypoxa sensitive pottasium channel –> depolarisation and opening of voltage gated calcium channels –> vasoconstriction
◦ Humoural and hormonal mediators (eg. eicosanoids, amines, adrenaline)
◦ Drugs (eg. nitric oxide and sildenafil)
◦ Neural

90
Q

How si the pulmonary resistance changed

A

◦ Blood flow
◦ Lung volume
◦ Hypoxic pulmonary vasoconstriction - most effected by alveoalr hypoxia, PaO2 <70mmHg causes closure of hypoxa sensitive pottasium channel –> depolarisation and opening of voltage gated calcium channels –> vasoconstriction
◦ Humoural and hormonal mediators (eg. eicosanoids, amines, adrenaline)
◦ Drugs (eg. nitric oxide and sildenafil)
◦ Neural

91
Q

What is the volume of blood in the pulmonary system? How much modulation is there in this? Why can it act as a reservoir

A

450mls
During straining drops to 250mls
Recruitment and distension

92
Q

Volume of blood in the pulmonary capillaries

A

80mls

93
Q

Central blood volume

A

450mls in the lung
350mls int he heart durnig diastole
800mls total

15% of blood volume in errect position

94
Q

What is the equation of pulmonary vascular resistance with a Swanz Ganz catheter

A

PVR = (mean PAP - PCWP) / CO

Dynes.sec/Cm/5
Normal 100dyanes.sec/cm^5
1/10 of systemic vascular resistance

95
Q
A

Respiratory (10 decks)

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