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Medicine year 1 > Respiration principles > Flashcards

Respiration principles Flashcards

1
Q

What are the steps of respiration (4)

A

ventilation
Gas exchange between alveoli and blood
Gas transport in blood
Gas exchange at a tissue level

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2
Q

What type of processes are inspiration and expiration

A

Inspiration is an active process
Expiration is a passive process (except in exercise)

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3
Q

What occurs during inspiration (2)

A

respiratory muscles contract
Chest wall and lungs are stretched

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4
Q

What is the mechanism of inspiration (2)

A

increase in the size of the lungs decreases intracellular-alveolar pressure
Air enters lungs down its pressure gradient until intracellular-alveolar pressure equals atmospheric pressure

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5
Q

What occurs during expiration (3)

A

Muscles of inspiration relax
Volume of thoracic cavity is reduced
Volume of lungs is reduced

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6
Q

what enables chest wall and stretched lungs to return to their pre-inspiration size

A

recoil due to elastic properties

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7
Q

What effect does recoil of the lungs have (2)

A

intra-alveolar pressure rises
Air leave as the lungs down its pressure gradient until intracellular-alveolar pressure equals atmospheric pressure

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8
Q

What limits the expansion of alveoli

A

their lining of a fluid that creates surface tension

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9
Q

What counters the limiting effect of the fluid lining alveoli

A

Surfactant which has detergent-like properties
Stabilises inflation of alveoli

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10
Q

What secretes surfactant for alveoli

A

type II pneumocytes

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11
Q
A
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12
Q

Describe the plural seal (2)

A

a seal created by fluid in space between visceral and partial pleura
Keeps the lungs against the chest wall without physical attachment

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13
Q

Describe the pressure of the pleural space (2)

A

negative
Because elastic recoil of the lungs pulls visceral pleura inwards and the chest wall pulls parietal pleura outwards

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14
Q

What forces move the lungs and chest wall (3)

A

Compliance
Elastance
Pressure gradients

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15
Q

What resistances do the lungs and chest walls overcome (3)

A

air-liquid surface tension
Elastic properties of alveolar walls
Airway radius

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16
Q

What is elastic recoil pressure

A

A measure of elastance

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17
Q

What determines frictional resistance of airways

A

Air flow

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18
Q

What are pressure flow characteristics determined by (3)

A

Airway resistance
Parenchymal resistance
Chest wall chest resistance

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19
Q

What effect does parasympathetic stimulation have on the respiratory tree

A

Bronchoconstriction

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20
Q

What effect does sympathetic stimulation have on the respiratory tree

A

bronchodilation

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21
Q

What muscles are involved in tidal inspiration (2)

A

diaphragm
External intercostals

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22
Q

What are the accessory muscles of active inspiration (3)

A

sternocleidomastoid
Scalenes
Pectoral muscles

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23
Q

What muscles are involved in active expiration (2)

A

abdominal muscles
Internal intercostal muscles

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24
Q

Tidal volume definition

A

volume of air entering/leaving lungs in a single breath

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25
Q

Inspiration reserve volume

A

extra volume of air that can be maximally inspired over the typical resting tidal volume

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26
Q

Expiratory reserve volume

A

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after resting tidal volume

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27
Q

Residual volume

A

minimum volume of air remains in lungs after maximal expiration

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28
Q

Which lung volume cannot be measured directly with spirometers

A

Residual volume

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29
Q

Inspiratory capacity

A

maximum volume of air that can be inspired at the end of normal tidal expiration

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30
Q

Functional residual capacity

A

volume of air in the lungs at the end of normal, passive expiration

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31
Q

Vital capacity

A

maximum volume of air that can be moved out during a single breath following a maximal inspiration

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32
Q

Total lung capacity

A

total volume of air lungs can hold

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33
Q

What can be determined from a volume-time curve (2)

A

Forced vital capacity
Forced expiratory volume in one second

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34
Q

What is the expected FEV1/FVC ratio

A

Greater than or equal to 75%

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35
Q

What are the types of lung diseases (2)

A

obstructive
Restrictive

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36
Q

Describe obstructive lung disease

A

when there is reduced expiratory flow and air trapping

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37
Q

Describe restrictive lung disease

A

when the lungs have a reduced functional volume

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38
Q

What increases in cases of obstructive lung disease (3)

A

total lung capacity
Residual volume
Functional residual capacity

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39
Q

What decreases in cases of restrictive lung disease (3)

A

Total lung capacity
Residual volume
Functional residual volume

40
Q

What does anatomical dead space refer to

A

How some inspired air remains within airways where it is not available for gas exchange

41
Q

Which is lower: alveolar/pulmonary ventilation and why

A

Alveolar
Due to presence of anatomical dead space

42
Q

What is alveolar ventilation (2)

A

volume of air exchanged between atmosphere and alveoli per minute
Represents new air available for gas exchange with blood

43
Q

What is atmospheric pressure

A

Pressure exerted by weight of air above earth in the atmosphere

44
Q

What law dictates the mechanism of inspiration and expiration

A

Boyle’s law

45
Q

What is partial pressure

A

pressure exerted by a dissolved gas in a liquid

46
Q

In atmospheric air, what are the partial pressures of oxygen and carbon dioxide

A

O2 - 21.1 kPa
CO2 - 0.03 kPa

47
Q

What happens when inspired gases come into contact with body fluid (2)

A

gas molecules enter water and dissolve in liquid
Water molecules evaporate to enter air and exert a vapour pressure

48
Q

what requirement is there is a gas reacts with a component of liquid

A

the reaction must complete before equilibrium is reached and partial pressure is established

49
Q

Describe interaction between oxygen and blood (4)

A

when oxygen enters plasma it dissolves
The dissolved oxygen enters RBC and binds to haemoglobin
Until haemoglobin is fully saturated
Once it is saturated, oxygen continues to dissolve until equilibrium is reached

50
Q

What is pO2 a measure of

A

dissolved oxygen in blood

51
Q

As dissolved oxygen leaves the blood and diffuses into tissues, what happens

A

it is replaced by the oxygen bound to haemoglobin which in turn also diffuses into tissues

52
Q

What are the partial pressures of oxygen and carbon dioxide in alveolar air

A

O2 - 13.3 kPa
CO2 - 5.3 kPa

53
Q

Describe what happens in alveolar air (3)

A

Inhaled air mixes with residual volume
Oxygen diffuses across alveolar wall
Carbon dioxide enters the alveoli

54
Q

What factors affect the rate of gas diffusion (3)

A

partial pressure gradient across membrane
Surface area available
Thickness (distance to travel)

55
Q

What can alter the distance molecules must diffuse (2)

A

Increases due to oedema fluid in interstitial spaces and alveoli
Increases due to increased thickeners of alveolar capillary membrane (lung fibrosis)

56
Q

Which is more soluble: carbon dioxide or oxygen

A

carbon dioxide

57
Q

Which has a greater molecular weight: carbon dioxide or oxygen

A

carbon dioxide

58
Q

What compensates for slower diffusion of oxygen (compared to carbon dioxide)

A

larger difference in partial pressures

59
Q

Why is oxygen exchange more impaired (than CO2) in a diseased lung

A

Due to slower oxygen diffusion rate

60
Q

Wha are the components of the diffusion barrier (6)

A

Fluid film lining of alveoli
Epithelial cells of alveoli
Interstitial space
Endothelial cells of capillaries
Plasma
RBC membrane

61
Q

What does haemoglobin consist of

A

2 alpha subunits
2 beta subunits

62
Q

Describe T state of haemoglobin (2)

A

low affinity for oxygen
Occurs when pO2 is low

63
Q

Describe R state of haemoglobin (1)

A

high affinity for oxygen

64
Q

At what pO2 is haemoglobin half saturated

A

3.5-4 kPa

65
Q

At what pO2 is haemoglobin saturated

A

9-10 kPa

66
Q

Describe levels in a patient with anaemia btu normally functioning lungs (2)

A

normal pO2
Lower oxygen content

67
Q

What does tissue pO2 depend on

A

Metabolic activity of the tissue

68
Q

What does tissue pO2 determine

A

how much oxygen will dissociated from haemoglobin - the lower the pO2, the more oxygen will dissociate

69
Q

Why must tissue pO2 be sufficiently high

A

To drive diffusion of oxygen to cells

70
Q

In what situations can tissue pO2 fall lower without negatively impacting oxygen diffusion (2)

A

in tissues with high capillary density
Because this means that oxygen does not have as far to diffuse

71
Q

What does the Bohr shift refer to (2)

A

the relationship between pH and haemoglobin’s affinity for oxygen
Acidic conditions shift the dissociation curve to the right and promote the T state of haemoglbin

72
Q

Describe pH in relation to metabolic activity (2)

A

pH is lower in metabolically active tissues
Meaning that more oxygen is given up

73
Q

Describe temperature in relation to metabolic activity (2)

A

Temperature is higher in metabolically active tissues
This means that more oxygen is given up

74
Q

When does maximum unloading of oxygen occur (2)

A

when tissue pO2 can fall to a low level
When increased metabolic activity leads to a more acidic environment with a higher temperature

75
Q

Describe effect of extreme exercise in relation to oxygen (3)

A

Metabolism can increase 10x
Cardiac output can only increase 5x
This improves oxygen extraction by tissues

76
Q

Which cells contain 2,3-biphosphoglycerate

A

Red blood cells

77
Q

In what situations do levels of 2,3-biphosphoglycerate increase (2)

A

Anaemia
High altitude

78
Q

What is the effect of increased 2,3-biphosphoglycerate (2)

A

shifts haemoglobin dissociation curve to the right
Allows more oxygen to be given up to tissues

79
Q

Describe carbon monoxide poisoning (3)

A

CO reacts with haemoglobin to form COHb
This increases the unaffected subunits’ affinity for oxygen
Oxygen wont be given up at tissues

80
Q

What does hypoxaemia refer to

A

low pO2 in arterial blood

81
Q

Why is hypoxaemia a problem (2)

A

when pO2 levels are too low, not all haemoglobin will be saturated
So not enough oxygen will be present in the blood

82
Q

What does hypoxia refer to

A

inadequate oxygen levels in the body/tissues

83
Q

What can cause peripheral hypoxia

A

peripheral vasoconstriction

84
Q

What are examples of issues where tissues use oxygen faster than it is delivered (2)

A

peripheral arterial disease
Raynaud’s

85
Q

Describe cyanosis

A

discolouration due to unsaturated haemoglobin
Deoxygenated haemoglobin is less red than oxygenated haemoglobin

86
Q

What does pulse oximetry detect (2)

A

Levels of haemoglobin saturation
Difference in absorption of light between oxygenated and deoxygenated haemoglobin

87
Q

What does pulse oximetry NOT detect

A

how much haemoglobin is present

88
Q

Which is more abundant in arterial blood: CO2 or O2

A

CO2

89
Q

What are the roles of CO2 (2)

A

Metabolic waste product
Controlling blood pH

90
Q

What is the pH range of arterial blood

A

7.35-7.45

91
Q

Describe what happens when carbon dioxide comes into contact with liquid (2)

A

CO2 dissolves in water
Dissolved CO2 reacts with the water in plasma RBC

92
Q

What is formed when dissolved CO2 reacts with water

A

carbonic acid

93
Q

Describe action of carbonic acid

A

it rapidly dissociates to hydrogen ions and hydrogen carbonate ions

94
Q

What does pH of plasma depend on (2)

A

how much CO2 reacts to form hydrogen ions
And so on [dissolved CO2] and [hydrogen carbonate]

95
Q

What does quantity of CO2 dissolved depend on

A

Partial pressure of CO2
(Higher pCO2, lower plasma pH)

96
Q

What controls pCO2 in alveoli

A

rate of breathing

97
Q

.

A

.

Medicine year 1 (15 decks)

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