Pulmonary Blood Flow, Gas Exchange and Transport Flashcards

1
Q

How is the bronchus supplied with blood?

A

Via bronchial arteries (nutritive)

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2
Q

What type of circulation supplies the bronchus?

A

Systemic Circulation

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3
Q

What tissues are supplied in the bronchus by the bronchial arteries?

A
  • Smooth muscle - Nerves - Lung tissue
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4
Q

How are the lungs supplied with the vessels that exchange gas?

A
  • Pulmonary arteries
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5
Q

Where do the pulmonary arteries originate from?

A

Right ventricle

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6
Q

What is the function of the pulmonary vein?

A
  • Returning oxygenated blood to the heart
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7
Q

What is the systolic pressure of the pulmonary artery

A

25mmHg

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8
Q

What is the flow of the pulmonary artery?

A

High flow

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9
Q

How much blood goes through your lungs every minute?

A

5L

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10
Q

What is gas exchange said to travel down?

A

A partial pressure gradient?

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11
Q

What is the partial pressure of CO2 in venous circulation and the pulmonary artery?

A

46mmHg (6.2kPa)

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12
Q

What is the partial pressure of O2 in venous circulation and the pulmonary artery?

A

40mmHg (5.3kPa)

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13
Q

What does the partial pressure of gases in the venous blood give an indication into?

A

What is going on with gas exchange in the tissue

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14
Q

What is the partial pressure of CO2 in the arterial circulation and the pulmonary vein?

A

40mmHg (6.2kPa)

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15
Q

What is the partial pressure of O2 in the arterial circulation and the pulmonary vein?

A

100mmHg (13.3kPa)

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16
Q

What will the partial pressures of these gases in arterial circulation give an indication to?

A

What is going on with gas exchange in the lungs

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17
Q

What does PA stand for?

A

Alveolar pressure

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18
Q

What does Pa stand for?

A

Arterial blood pressure

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19
Q

What does Pṽ stand for?

A

Mixed venous blood pressure (pulmonary artery)

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20
Q

What 3 things is the rate of diffusion directly proportional to?

A
  • Partial pressure across the membrane - Gas solubility - Surface area
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21
Q

What is rate of diffusion inversely proportional to?

A

Thickness of the membrane

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22
Q

What is the partial pressure GRADIENT of O2 in the alveoli to the vessels of deoxygenated blood?

A

60mmHg (100 in the alveoli, 40 in the blood)

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23
Q

How much O2 diffuses across the alveoli per minute?

A

250ml

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24
Q

What is the partial pressure GRADIENT of CO2 in the alveoli to the vessels of deoxygenated blood?

A

6mmHg (46 in the blood, 40 in the alveoli)

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25
Q

How much CO2 diffuses across the alveoli per minute?

A

200ml

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26
Q

Why is the rate of diffusion of CO2 not 10 times less than O2 if the partial pressure gradient is?

A

CO2 is more soluble in water

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27
Q

How does pulmonary oedema affect gas exchange?

A
  • Fluid inbetween vessels and alveoli
  • Since O2 doesn’t dissolve well in water it reduces the movement of O2
  • Also increases distance between membranes so diffusion is reduced
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28
Q

How does emphysema reduce gas exchange?

A

Reduces surface area

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29
Q

How does fibrosis reduce gas exchange?

A
  • Increases membrane thickness
  • Reduces ventilation and compliance
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30
Q
A
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31
Q

How is pulmonary fibrosis confirmed?

A

Is radioopaque so shows up on chest X ray

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32
Q

How does emphysema increase surface area?

A
  • Imagine the lungs are like a net and have loads of small holes
  • If you tear the barrier between one of the holes you get 1 bigger hole
  • This is what emphysema does to the lungs
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33
Q

What is ventilation?

A

Air getting to the alveoli (L/min)

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34
Q

What is perfusion?

A

Locol blood flow (L/min)

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35
Q

What is the relationship between ventilation and perfusion?

A

They are equal

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36
Q

Where in the lung are ventilation and perfusion both higher?

A

Bottom of the lung

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37
Q

Why are ventilation and perfusion higher in the bottom of the lung?

A

Gravity

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38
Q

Where in the lung are ventilation and perfusion the lowest?

A

Apex

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39
Q

Where does arterial pressure exceed alveolar pressure in the lungs?

A

Bottom of the lung

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40
Q

What is distribution of blood flow influenced by?

A

Hydrostatic pressure

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41
Q

What other reasons are there for pulmonary artery perfusion decreasing as you go up the lung?

A

Because the pressure is lower, it is MORE susceptible to gravity

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42
Q

Moving up the lung, at roughly what rib does alveolar pressure become equal to blood flow (ratio = 1)?

A

Rib 3

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43
Q

Above rib 3, which is higher out of alveolar pressure and Pa?

A

Alveolar

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44
Q

What is blood flow (Pa) directly proportional to?

A

Vascular Resistance

45
Q

What is mismatch 1?

A
  • At the apex
  • Ventilation > perfusion
46
Q

What is mismatch 2?

A
  • At the base of the lung
  • Perfusion > ventilation
47
Q

Why is apex Pa lower?

A
  • Gravity
  • Alveoli squash blood vessels
48
Q

What is shunt?

A

Blood shifting from the right to left side of the heart through the pulmonary vessels withouth being oxygenated

49
Q

What happens to most blood vessels in the body in response to hypoxic conditions?

A

They dilate

50
Q

What happens to vessels in the lungs when they detect hypoxic conditions?

A

They contract

51
Q

Why do the vessels in the lungs contract in response to hypoxic conditions?

A

So that less blood travels to the alveoli that have low oxygen and therefore more blood travels to areas with higher O2 conc.

52
Q

What does a higher pressure of CO2 in the lungs cause?

A

Bronchodilation to increase ventilation

53
Q

What is an example of a condition in which perfusion will be higher that PA?

A

Lung cancer

54
Q

What is a condition which may cause higher ventilation?

A

PE

55
Q

What is the name given to the aspect of higher ventilation that means a lot of the air won’t be used in gas exchange? (alveoli that are ventilated but not perfused?)

A

Alveolar dead space

56
Q

What does an increase in alveolar PO2 do to pulmonary circulatory vessels?

A

Pulmonary Vasodilation

57
Q

When alveoli are ventilated but not perfused, alveolar PCO2 is reduced; what effect will this have on the brochus?

A

Bronchoconstriction

58
Q

What is physiological dead space?

A

ALVEOLAR Dead Space + ANATOMICAL Dead Space

59
Q

How much O2 dissolves per litre of plasma?

A

3ml

60
Q

To what value does haemoglobin increase blood O2 capacity to?

A

200ml/L

61
Q

What does arterial partial pressure refer to?

A

ONLY O2 in solution

62
Q

What is O2 concentration determined by?

A
  • O2 solubility
  • Partial Pressure of O2 in the gaseous phase
63
Q

What are the values of partial pressure of a gas in solution equal to?

A

The partial pressure of the gas in the gaseous phase that is DRIVING the gas into solution

64
Q

EXAMPLE OF PARTIAL PRESSURE AND ARTERIAL O2 PRESSURE

A
  • O2 solubility in water is low (0.03ml/L/mmHg)
  • We have 3ml/L of O2 in the plasma therefore the partial pressure driving O2 into the plasma must be 100mmHg
  • VOLUME IN SOLUTION/SOLUBILITY = PARTIAL PRESSURE
  • 3/0.03 = 100mmHg
65
Q

What is the partial pressure that drives oxygen into solution sometimes known as?

A

Oxygen tension

66
Q

What would happen if O2 travelled as gas in the blood?

A

Air Embolism - fatal

67
Q

What is the O2 demand for resting tissue?

A

250ml/min

68
Q

Without haemoglobin, how much O2 would tissue get using just arterial oxygen?

A
  • Arterial O2 = 3ml/L
  • Cardiac output = 5L/min

= 15ml/min

NOT ENOUGH TO MAINTAIN TISSUE

69
Q

How much haemoglobin do we have on average in our blood?

A

150g/L

70
Q

How much O2 is carried per gram of haemoglobin?

A

1.34ml

71
Q

With haemoglobin, how much O2 is carried in the blood to tissues?

A
  • 150g/L
  • 5L
  • 150 x 5 = 750
  • 1.34 ml of O2 per gram
  • Roughly 1000ml/min
72
Q

What percentage of O2 in the blood is extracted by tissue?

A

25%

73
Q

How many alpha and beta chains are in haemoglobin?

A
  • 2 A
  • 2 B
74
Q

What is the name given to the fact that if an O2 binds to one of the polypeptide chains, it increases the affinity for O2 of the others?

A

Cooperative binding

75
Q

What are the 4 different types of haemoglobin?

A
  • Adult haemoglobin (HbA)
  • HbA2
  • Fetal haemoglobin (HbF)
  • Glycosylated haemoglobin
76
Q

What percentage of total haemoglobin is HbA?

A

92%

77
Q

How does HbA2 differ from HbA?

A

Delta chains replace beta chains

78
Q

How does HbF differ from HbA?

A

Gamma chains replace beta chains

79
Q

What are the three types of glycosylated haemoglobin?

A
  • HbA1A
  • HbA1B
  • HbA1C
80
Q

What is the major determinant of haemoglobin saturation with oxygen?

A

Partial pressure of O2 in arterial blood

81
Q

What condition is testing for glycosylated haemoglobin useful for?

A

Diabetes

82
Q

How does haemoglobin help maintain the partial pressure gradient needed to draw O2 out of the alveoli?

A
  • Essentially mops up the O2 in the plasma
  • This means more O2 is drawn out to try to reach equilibrium until the haemoglobin is saturated
83
Q

What saturation is haemoglobin at at normal systemic arterial PO2?

A

About 100%

84
Q

What is the saturation of haemoglobin at venous pressure?

A

75%

85
Q

What has a higher affinity for O2, HbA or HbF?

A

HbF

86
Q

Why does HbF need a higher affinity?

A

Used to capture O2 from maternal blood

87
Q

What has a higher affinity, HbF or myoglobin?

A

Myoglobin

88
Q

Which type of muscle fibres have more myoglobin?

A

Oxidative

89
Q

Definition of anaemia?

A

Condition where O2 carrying capacity of the blood is compromised

90
Q

What is the PaO2 during anaemia?

A

Normal

91
Q

What effect does acidosis have on affinity for oxygen and therefore the haemoglobin saturation curve?

A

Lowers O2 affinity so more O2 moves out into the muscles, graph shifts right

92
Q

What effect does alkalosis have on affinity for oxygen and therefore the haemoglobin saturation curve?

A

Increases affinity for O2, graph shifts left

93
Q

What effect does increased body temperature have on affinity for oxygen and therefore the haemoglobin saturation curve?

A

Reduces affinity and shifts the curve to the right

94
Q

What effect does low body temperature have on affinity for oxygen and therefore the haemoglobin saturation curve?

A

Increases affinity and shifts the curve left

95
Q

How much more attracted to haemoglobin is carbon monoxide than oxygen?

A

250 times?

96
Q

What effect does 2,3 - DPG have on affinity for oxygen and therefore the haemoglobin saturation curve?

A
  • Is released during hypoxia
  • Reduces affinity and shifts the curve right
97
Q

Once someone has breathed carbon monoxide in why is it hard to treat them?

A

Dissociates very slowly

98
Q

What is a typical sign of carbon monoxide poisoning?

A

Cherry red skin

99
Q

What is the treatment for CO poisoning?

A
  • 100% oxygen
  • Sometimes ventilate CO2 to encourage increased ventilation
100
Q

What are the 5 main types of hypoxia?

A
  • Hypoxic hypoxia - reduced O2 gas exchange
  • Anaemic hypoxia - reduction in O2 carrying capability
  • Ischaemic hypoxia - heart disease with innefficient circulation
  • Histotoxic hypoxia - poisoning that prevents cells using O2
  • Metabolic hypoxia - O2 delivery doesn’t reach tissue demand
101
Q

What 3 places does CO2 reside when being transported in the blood

A
  • Plasma (7%)
  • Combines with deoxyhaemoglobin (23%)
  • Reacts with water in erythrocytes to form carbonic acid (70%)
102
Q

What does the carbonic acid dissociate into?

A

Bicarbonate and H+ ions

103
Q

What does the bicarbonate “swap” with to move out of the cell and what is this process called?

A
  • Chlorine
  • Chlorine shift
104
Q

What do the dissociated H+ ions do?

A

Bind to deoxyhaemoglobin

105
Q

Why is CO2 able to change ECF pH?

A

It dissociates into a base and H+ ions which both alter the pH

106
Q

When would CO2 alter pH?

A

During hypo/hyperventilation

107
Q

What will hypoventilation cause?

A

CO2 retention - acidosis

108
Q

What will hyperventilation cause?

A

CO2 will be lost more - alkalosis