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Human Systems and Anatomy > VQ relationships and disorders > Flashcards

VQ relationships and disorders Flashcards

1
Q

what is the VQ ratio

A

the relationship between ventilation and perfusion (ventilation to blood flow)

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2
Q

what is ventilation

A

process by which air moves in and out of the lung

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3
Q

what is perfusion

A

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

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4
Q

what does the VQ ratio determine

A

the level of partial pressure of oxygen and carbon dioxide in the blood

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5
Q

describe the pleural pressure distribution in the lungs

A

more negative at the apex than at the base

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6
Q

what is compliance

A

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

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7
Q

what are some pulmonary conditions that lead to reduced compliance

A

scarring in the lung tissue
fluid in the lungs
deficient surfactant production
destruction of elastic fibres

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8
Q

what is resistance

A

narrowing or obstruction in the airway that may reduce airflow

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9
Q

what are some conditions that lead to an increase in resistance

A

asthma
obstruction or collapse of airways due to COPD

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10
Q

what is COPD

A

chronic obstructive pulmonary disease including ephysema or chronic bronchitis

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11
Q

what are the two types of dead space

A

anatomical dead space or physiological dead space

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12
Q

what is anatomical dead space

A

volume of gas during each breath that fills the conducting airways

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13
Q

what is physiological dead space

A

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

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14
Q

describe pulmonary blood flow distribution

A

pulmonary circulation is a low pressure and low resistance system, influenced by gravity more than systemic circulation

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15
Q

describe pulmonary circulation when sat upright

A

greater blood flow to the base than to the apex

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16
Q

what can influence flow and the VQ ratio

A

the variations in arterial and venous pressure

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17
Q

summarise pressure and resistance of pulmonary circulation

A

low pressure
low resistance

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18
Q

what is the VQ ratio defined as for a single alveolus

A

alveolar ventilation divided by capillary flow

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19
Q

what is the VQ ratio defined as for the lungs as a whole

A

total alveolar ventilation divided by cardiac output

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20
Q

what is the VQ for lungs in healthy people

A

0.8-1.2

21
Q

what does the perfect model for VQ ratio actually mean

A

where the alveolar partial pressure of oxygen and arterial partial pressure of oxygen are the same

22
Q

what is the arterial blood gas for someone with arterial hypoxemia

A

arterial partial pressure of oxygen is less than 80mmHG

23
Q

what is the partial pressure for hypoxia

A

less than 60mmHg

24
Q

what is hypoxia

A

this is when there is insufficient oxygen to carry out metabolic functions

25
Q

what is the partial pressure for hypercapnia

A

over 40 mmHg

26
Q

what is the partial pressure for hypocapnia

A

less than 35 mmHg

27
Q

what is anatomical shunting

A

this is when mixed venous blood is shunted directly into arterial blood
when this happens, the alveolar ventilation is the same, but the distribution of blood flow is changed

28
Q

what is a right to left shunt

A

blood being shunted is deoxygenated

29
Q

where do most anatomical shunts occur

A

in the heart, where the blood from the right ventricle or atrium crosses the septum to the left atrium or ventricle

30
Q

what does anatomical shunting lead to

A

hypoxemia

31
Q

does anatomical shunting affect the partial pressure of carbon dioxide

A

no, because central chemoreceptors are very sensitive to carbon dioxide changes to increase ventilation. this leads to a reduction in partial pressures of carbon dioxide

32
Q

describe physiological shuntings impact on VQ

A

the alveolar ventilation is different, but the distribution of the blood flow is the same

33
Q

what is the VQ ratio in physiological shunting

A

0

34
Q

what is physiological shunting

A

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

35
Q

what is atelectasis

A

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

36
Q

what is the most frequent cause of artieral hypoxemia in patients with respiratory disorders

A

VQ mismatching

37
Q

what does VQ mismatching lead to

A

varying alveolar and capillary gas contents

38
Q

what is encompassed in COPD

A

emphysema and chronic bronchitis

39
Q

what are the symptoms of COPD

A

chronic cough
chest tightness
shortness of breath
increased mucous production

40
Q

what is the most frequent cause of COPD

A

long term smoking

41
Q

what is emphysema

A

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

42
Q

describe chronic bronchitis

A

inflammation of the bronchi causes mucous production and excessive swelling
shortness of breath with mild exertion

43
Q

what is pulmonary fibrosis

A

this is a type of interstital lung disease, and leads to scarring and thickening of tissue.
there is decreased elasticity and decreased gas exchange

44
Q

what is used to measure lung volume

A

vitalograph or spirogram

45
Q

what are the four major results obtained from vitalograph

A

forced vital capacity
forced expiratory volume in one second
ratio of forced expiratory volume to forced vital capacity
average mixmaximal expiratory flow

46
Q

what is the main cause for the regional differences between ventilation and perfusion

A

gravity

47
Q

what is the VQ when ventilation exceeds perfusion

A

over one

48
Q

what is the VQ ration when perfusion exceeds ventilation

A

less than one

Human Systems and Anatomy (57 decks)

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