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Respiratory System BDS1 > Ventilation, Perfusion and V/Q Relationship > Flashcards

Ventilation, Perfusion and V/Q Relationship Flashcards

1
Q

what is ventilation?

A

the process by which air moves in and out of lung

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2
Q

what is perfusion?

A

the process by which deoxygenated blood passes through the lung and becomes deoxygenated

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3
Q

what is the relationship between ventilation and perfusion called?

A

V/Q ratio

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4
Q

where in the alveoli is the pleural pressure more negative?

A

at the apex than at the base

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5
Q

where in the alveoli is the transpulmonary pressure the greatest?

A

at the apex

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6
Q

where in the alveoli is the alveolar volume greater?

A

at the apex

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7
Q

what affects distribution of ventilation?

A

gravity, compliance (C) and resistance (R)

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8
Q

what is compliance?

A

how much effort is required to stretch the lungs and the chest wall

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9
Q

what does high compliance mean?

A

the lungs and the chest wall expand easily

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10
Q

what is decreased compliance common in?

A

pulmonary conditions

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11
Q

what is scarring in lung tissue more commonly known as?

A

tuberculosis

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12
Q

what is lung filled with fluid known as?

A

edema

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13
Q

what is the destruction of elastic fibres called?

A

emphysema

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14
Q

what are the four pulmonary conditions that decreased compliance is common in?

A

scarring in lung tissue, lung filled with fluid, deficiency in surfactant production and destruction of elastic fibres

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15
Q

what does resistance mean?

A

any narrowing or obstruction of the airway that may reduce airflow

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16
Q

what part of the respiratory system has decreased resistance?

A

large diameter airways

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17
Q

what pulmonary conditions is increased resistance common in?

A

asthma, COPD due to obstruction or collapse of airways

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18
Q

what are the two types of dead space?

A

anatomical and physiological

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19
Q

what is anatomical dead space?

A

volume of gas during each breath that fills the conducting airways

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20
Q

what is physiological dead space?

A

total volume of gas in each breath that does not participate in gas exchange e.g. alveoli that are ventilated but not perfused

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21
Q

what is the function of the pulmonary circulation?

A

brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart

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22
Q

what is the function of bronchial circulation?

A

brings oxygenated blood to lung parenchyma

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23
Q

comment on the systemic circulation in terms of pressure and resistance

A

high pressure - 120/80mmHg and high resistance

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24
Q

comment on the pulmonary circulation in terms of pressure and resistance

A

low pressure - 24/9 mmHg and low resistance

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25
Q

what is the difference between the vessels of the systemic and pulmonary circulation

A

smooth muscle in systemic vessels whereas wider vessels with less smooth muscle in pulmonary vessels

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26
Q

what type of circulation does gravity influence more?

A

pulmonary

27
Q

what factors influence flow and ventilation-perfusion relationships?

A

the greater blood flow to base than apex and the wide variations in arterial and venous pressure from apex to base

28
Q

what is the V/Q ratio?

A

the ratio of ventilation to blood flow

29
Q

what is the V/Q ratio for a single alveolus defined as?

A

alveolar ventilation divided by capillary flow

30
Q

what is the V/Q ratio for the entire lung defined as?

A

total alveolar ventilation divided by cardiac output

31
Q

what is the alveolar ventilation in healthy individuals?

A

4-6 L/min

32
Q

what is the pulmonary blood flow in healthy individuals?

A

5L/min

33
Q

what is the V/Q for lungs in healthy individuals?

A

0.8-1.2

34
Q

what happens to the V/Q ratio when ventilation exceeds perfusion

A

V/Q > 1

35
Q

what happens to the V/Q ratio when perfusion exceeds ventilation?

A

V/Q < 1

36
Q

what does the mismatching of pulmonary blood flow and ventilation result in?

A

impaired O2 and CO2 transfer

37
Q

what is arterial hypoexmia?

A

arterial PO2 < 80mmHg

38
Q

what is arterial hypoxia?

A

when insufficient O2 to carry out metabolic functions - when arterial PO2 < 60 mmHg

39
Q

what is hypercapnia?

A

increase in arterial PCO2 > 40 mmHg

40
Q

what is hypocapnia?

A

decrease in arterial PCO2 < 35 mmHg

41
Q

what is V-Q mismatching?

A

some alveoli V/Q > 1 and some < 1

42
Q

where does V/Q mismatching result in?

A

varying alveolar and capillary gas contents

43
Q

what is an anatomical shunt

A

mixed venous blood shunted directly into arterial blood (in the case of lung - mixed pulmonary artery blood shunted into the pulmonary veins)

44
Q

what happens to the alveolar ventilation and the distribution of blood flow in an anatomical shunt?

A

alveolar ventilation is the same but distribution of blood flow changed

45
Q

where do most anatomical shunts occur?

A

within heart - blood from right atrium or ventricle crosses septum to left atrium or ventricle: right to left shunt

46
Q

what does an anatomical shunt result in?

A

varying degrees of hypoxemia

47
Q

what is the effect on the PCO2 in an anatomical shunt?

A

PCO2 not increased because central chemoreceptors are very sensitive to CO2 changes - leads to increased ventilation and therefore reduction in PCO2

48
Q

what happens to the lung unit ventilation in a physiological shunt?

A

ventilation to lung units is absent in presence of continuing perfusion

49
Q

what happens in a physiological shunt?

A

blood perfusing non-ventilated alveolus is mixed venous blood, blood leaving continues to be mixed venous then mixes with arterial

50
Q

what is atelectasis?

A

obstruction of ventilation due to mucous plugs, airway oedema, foreign bodies or tumours in airways

51
Q

what happens when the V/Q = 0

A

ventilation to a region is 0, blocks airway, ventilation redistributed to other alveoli - elevated V/Q in other regions, e.g. child inhaling a peanut

52
Q

what happens with low V?Q?

A

asthma and chronic bronchitis

53
Q

what happens when the V/Q is infinite

A

no blood flow; perfusion to a region is 0, physiological deadspace, blood diverted to ther capillaries - low V/Q in other regions, e.g. pulmonary embolism

54
Q

what happens when there is a high V/Q?

A

emphysema - disrupted gas exchange and pulmonary fibrosis - decreased gas exchange

55
Q

what is COPD

A

condition in which the airflow is obstructed

56
Q

what does COPD usually appear as?

A

emphysema and chronic bronchitis

57
Q

what is COPD caused by?

A

long terms smoking

58
Q

what are the symptoms of COPD?

A

chronic cough, chest tightness, shortness of breath, increased mucous production

59
Q

what is emphysema?

A

structures in alveoli over inflated, lungs loose elasticity and cannot fully expand and contract, patients can inhale but exhalation is difficult due to decreased elastic recoil

60
Q

what is chronic bronchitis?

A

inflammation of bronchi causing mucous production and excessive, shortness of breath with mild exertion, chest infections more prevalent

61
Q

what is pulmonary fibrosis?

A

a type of interstitial lung disease, scarring and thickening of tissue, decreased elasticity, decreased gas exchange

62
Q

what are the regional differences in ventilation and perfusion due to

A

gravity

63
Q

what is the V/Q ratio in a healthy lung?

A

0.8

Respiratory System BDS1 (8 decks)

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