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04. Year 1: Respiratory System > Pulmonary Blood Flow and Gas Exchange and Transport 1 > Flashcards

Pulmonary Blood Flow and Gas Exchange and Transport 1 Flashcards

1
Q

How does alveolar ventilation and compliance change with height from the base to the apex?

A

Both of them decline

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2
Q

Why does compliance decline with height from the base to the apex?

A

Alveoli are more inflated at FRC at the apex, since the ones at the base are more compressed

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3
Q

What does the alveoli at the apex being more inflated than the ones at the base mean for changes in intrapleural pressure?

A

Changes in pressure brings about bigger changes in alveolar volume at the base

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4
Q

What does the pulmonary vein carry?

A

Oxygenated blood from the lungs to the heart

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5
Q

What does the pulmonary artery carry?

A

Deoxygenated blood from the heart to the lungs

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6
Q

What are the 2 kinds of blood supply to the lungs?

A

Bronchial circulation

Pulmonary circulation

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7
Q

What is the purpose of bronchial circulation?

A

Supply the lungs with nutrients

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8
Q

What circulation supplies the lungs with nutients?

A

Bronchial circulation

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9
Q

What is bronchial circulation supplied via?

A

Bronchial arteries from systematic circulation to supply oxygenated blood to airway smooth muscle, nerves and lung tissue

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10
Q

What is the purpose of pulmonary circulation?

A

Gas exchange

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11
Q

What circulation is used for gas exchange?

A

Pulmonary circulation

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12
Q

What does pulmonary circulation consist of?

A

Left and right pulmonary arteries originating from the right ventricle

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13
Q

What does pulmonary circulation do?

A

Carries entire cardiac output from right ventricle, supplying dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein

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14
Q

What kind of system is the pulmonary circulation?

A

High flow, low pressure

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15
Q

How does air diffuse across membranes?

A

Down its partial gradiants

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16
Q

What does gas exchange occur due to?

A

Presence of partial pressures

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17
Q

Where is the partial pressure of oxygen highest?

A

In arterial circulation

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18
Q

Where is the partial pressure of carbon dioxide highest?

A

In venous circulation

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19
Q

What does the abbreviation “A” mean in regards to partial pressures?

A

Alveolar

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20
Q

What does the abbreviation “a” mean in regards to partial pressures?

A

Arterial blood

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21
Q

What does the abbreviation “v” mean with regards to partial pressures?

A

Mixed venous blood (such as pulmonary artery)

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22
Q

What does PaO2 mean?

A

Partial pressure of oxygen in arterial blood

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23
Q

What does PACO2 mean?

A

Partial pressure of carbon dioxide in alveolar air

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24
Q

What does mixed venous blood (v) reflect the values of?

A

Values in tissue

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25
Q

What does arterial blood (a) reflect the values of?

A

Values of lungs

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26
Q

What rules does the diffusion of gases follow?

A

Rules for simple diffusion:

Moves across a membrane that is permeable to that gas

Moves down it’s partial pressure grandient until equilbrium is reached

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27
Q

What must a membrane be for a gas to diffuse across it?

A

Permeable to that gas

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28
Q

When does a gas stop diffusing down it’s concentration gradient?

A

When equilbrium is reached

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29
Q

What is the rate of diffusion across a membrane directly proportional to?

A

Partial pressure gradient

Gas solubility

Surface area

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30
Q

What is the rate of diffusion across a membrane inversely proportionate to?

A

Thickness of the membrane

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31
Q

When is diffusion most rapid?

A

Over short distances

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32
Q

Why does oxygen diffuse quicker than carbon dioxide, but no as great as might be expected?

A

Oxygen has a much greater partial pressure gradient

Carbon dioxide is much more soluble

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33
Q

What is the typical diffusion rate of oxygen?

A

250ml/min

34
Q

What is the typical diffusion rate of carbon dioxide?

A

200ml/min

35
Q

What does partial pressure in the alveoli reflect?

A

Systemic arterial blood

36
Q

What does partial pressure in pulmonary arteries reflect?

A

Partial pressure at tissues

37
Q

What are the typical partial pressure values for oxygen and CO2 in alveoli?

A

Oxygen 100mmHg

Carbon dioxide 40mmHg

38
Q

What are the typical partial pressure values for oxygen and CO2 in the pulmonary arteries?

A

Oxygen 40mmHg

Carbon dioxide 46mmHg

39
Q

What are some pathologies that affect gas exchange?

A

Emphysema

Fibrotic lung disease

Pulmonary edema

Asthma

40
Q

How does emphysema affect gas exchange?

A

Destruction of alveoli reduces surface area for gas exchange

41
Q

What disease reduces the surface area for gas exchange?

A

Emphysema

42
Q

How does fibrotic lung disease affect gas exchange?

A

Thickened alveolar membrane slows gas exchange, loss of lung compliance may decrease alveolar ventilation

43
Q

What disease thickens alveolar membranes and slows gas exchange?

A

Fibrotic lung disease

44
Q

How does a pulmonary edema affect gas exchange?

A

Fluid in interstitial space increases diffusion distance

Arterial PCO2 may be normal due to higher CO2 solubility in water

45
Q

What disease causes fluid in interstitial space that increases the distance gas needs to diffuse?

A

Pulmonary edema

46
Q

How does asthma affect gas exchange?

A

Increased airway resistance decreases airway ventilation

47
Q

What disease increases airway resistance and decreases alveolar ventilation?

A

Asthma

48
Q

What is present to help diffusion between alveoli and red blood cells?

A

Alveoli have a large surface area

Thin membrane between the two for a short diffusion distance

49
Q

What does this show the histology of?

A

Fibrotic alveoli

50
Q

What does this chest X-ray show?

A

Fibrosis

51
Q

What does this histology show?

A

Pulmonary oedema

52
Q

What disease has this lung suffered from?

A

Emphysema

53
Q

How should ventilation and perfusion compare to each other?

A

Complement each other

54
Q

What is ventilation?

A

Air getting to alveoli in L/min

55
Q

What is perfusion?

A

Local blood flow in L/min

56
Q

How do blood flow and ventilation change with heigh across the lung?

A

Both decrease

57
Q

How does blood flow compare to ventilation at the base of the lung and why?

A

Blood flow is higher than ventilation due to arterial pressure exceeding alveolar pressure, which compresses the alveoli

58
Q

Why are alveoli at the base of the lung compressed?

A

Because arterial pressure exceeds alveolar pressure

59
Q

How does blood flow compare to ventilation at the apex?

A

Blood flow is less than ventilation at the apex because arterial pressure is less than alveolar pressure, which compresses the arteries

60
Q

Why are the arteries compressed at the apex of the lung?

A

Because arterial pressure is less than alveolar pressure

61
Q

Where in the lung are alveoli and arteries compressed?

A

Alveoli are compressed at the base

Arteries are compressed at the apex

62
Q

How does blood flow and ventilation compare between the apex and the base of the lung?

A

Both are smaller at the apex, but at the base blood flow is greater than ventilation whereas at the apex ventilation is greater than blood flow

63
Q

Why does the ratio of ventilation to perfusion change within the lung between the base and the apex?

A

Due to difference between alveolar and arterial pressures, and because of gravity

64
Q

What is a perfectly matched ventilation/perfusion ratio?

A

1

65
Q

What is a mismatch ventilation:perfusion ratio?

A

Anything greater than or less than 1

66
Q

How much of a healthy lung performs well in matching perfusion and ventilation?

A

Over 75%

67
Q

Where does majority of the ventilation:perfusion mismatch take place?

A

Apex

68
Q

What occurs at the apex to try and keep the ventilation:perfusion ratio near 1?

A

Auto regulation, diverting blood to better ventilated alveoli

69
Q

What happens if ventilation becomes less than perfusion?

A

PCO2 increases and PO2 decreases

Blood flowing past those alveoli does not get oxygenated

70
Q

What is alveolar dead space?

A

When ventilation is greater than blood flow

71
Q

What is shunt?

A

When blood flow is greater than ventilation

72
Q

What happens when ventilation is greater than blood flow?

A

Increase in alveolar PO2 causing pulmonary vasodilation

Decrease in alveolar PCO2 causing mild bronchial constriction

73
Q

What is the response to alveolar dead space?

A

Increase perfusion and to lesser the extent decrease ventilation to bring the ratio back towards 1

74
Q

What is anatomical dead space?

A

Air in the conducting zone of the respiratory tract unable to participate in gas exchange as walls of the airways in this region are too thick

75
Q

What is the air in conducting zones of the respiratory tract that is unable to participate in gas exchange due to the wall being to thick called?

A

Anatomical dead space

76
Q

What is physiologic dead space?

A

Alveolar dead space + anatomical dead space

77
Q

What is alveolar dead space + anatomical dead space?

A

Physiologic dead space

78
Q

How would you describe pulmonary arterial pressures?

A

Low

79
Q

What are typical sysolic and diastolic pulmonary arterial pressures?

A

Systolic 25mmHg

Diastolic 8mmHg

80
Q

What is the low pressure of the pulmonary arterial blood flow more susceptable to?

A

Effects of gravity which gives rise to a greater degree of variability in blood flow within the lung, the base being highly perfused compared to the apex

81
Q

Why is the base highly perfused compared to the apex?

A

Gravity having a great impact on the vessels due to the low pressure

82
Q

Why are the overall diffusion rates of CO2 and oxygen similar dispite CO2 diffusing much faster?

A

Oxygen has a greater partial pressure difference

04. Year 1: Respiratory System (37 decks)

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