Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pulmonary physiology > Ventilation > Flashcards

Ventilation Flashcards

1
Q

How does intrapleural pressure and alveolar pressure change in inspiration?

A

Reduced intrapleural pressure (-11cmH2O)

Reduce alveolar pressure by (5cmH2O)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does ventilation allow?

A

Inspired air reaches alveoli and blood gas barrier, expired gases are removed from the alveoli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is total ventilation?

A

Total rate of flow in and out of the lung during normal tidal breathing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Units for total ventilation

A

L/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do changes in rate and depth of ventilation cause?

A

Composition of alveolar gas, and therefore composition of gases entering/exiting blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is alveolar ventilation?

A

Volume of air that reaches the alveoli and is avaliable for gas exchange with blood (vol/min)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the resting O2 consumption and CO2 production?

A

Resting O2 consumption = 250ml/min

Resting CO2 production= 200ml/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What zones do airways compromise and what is their role?

A

1) conducting airways: delivery of gas to alveoli

2) exchange zones: exchange to and from pulmonary circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the volumes of the conducting and exchange zones?

A 
Conducting = 150ml
Exchange = 3000ml
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the anatomical dead space?

A

Volume of conducting airways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the physiological dead space?

A

Anatomical dead space plus the alveolar dead space (volume that doesn’t take part in gas exchange)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How many times do airways bifurcate to reach the alveolar ducts?

A

23 times

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

After how many divisions do we reach respiratory bronchioles?

A

17th is respiratory bronchioles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are normal alveolar partial pressures of O2 and CO2?

A

PAO2 = 13.3.KPa (100mmHg)

PACO2= 5.3 KPa (40mmHg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens as total cross sectional area increases going down the airways?

A

Velocity (of gas flow) decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe how cross sectional area changes across conducting zone and respiratory zone

A

Increases in conducting zone and then rapidly increases in respiratory zone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe how the mechanisms of convection and diffusion change going further into the lungs

A

In conducting zone, convection dominant

In respiratory zone convection slows (velocity decreases due to larger cross-sectional area) so diffusion becomes dominant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe the oxygen percentage: airway generation graph

A

From generation 1-16 oxygen percentage 20% (dead space)

Then from 16-17 large decrease in percentage to 13% and stays there for subsequent generations (exchange is occuring)

In exhalation the O2% remains at 13%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How are lung volumes measured?

A

Spirometer (subject breathes into a sealed container)

The changes in the spirometer are equal and opposite to the the changes in the lungs of the subject

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Lung volumes vary with…

A

Sex, size and gender

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is functional residual capacity (FRC)?

A

Volume of gas in lungs after normal expiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is normal FRC value?

A

2.5-3 L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the tidal volume?

A

0.5 litre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the vital capacity

A

Amount of gas that can be inhaled by a maximal inspiratory effort following maximal expiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Normal value for vital capacity

A

5L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is intrapleural pressure, what is it normally?

A

Pressure of fluid within the pleural cavity. Normally negative (less than atmospheric)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the pleural cavity?

A

Fluid filled space between each pleura (visceral and pareital)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What generates the normally negative intrapleural pressure after expiration?

A

1) Ribcage has natural tendency to spring upwards

2) Lungs have intrinsic tendency to collapse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What happens to intrapleural pressure when pleura damaged?

A

Air introduced into pleural space, intrapleural pressure may exceed/equal atmospheric pressure leading to pneumothorax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What happens to lungs and chest wall in a pneumothorax?

A

Lungs collapse inwards, chest wall outwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is an assumption when we consider normal intrapleural pressure value?

A

Static mechanics (after normal expiration and no gas flow in/out) so pressure outside lung and in alveoli is the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How does inspiration change intrapleural pressure and alveolar pressure (mechanism)?

A

Lift ribcage and increase intra-thoracic volume (stretch lungs)

Reduces intrapleural pressure (holds lungs in more stretched position)

Alveolar pressure is reduced and inspiraiton initiated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe how alveolar pressure compares to atmospheric pressure when no air flowing in

A

Equal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Describe the mechanism behind expiration in terms of pressures

A

Muscles of chest wall and diaphragm relax

Decrease intra-thoracic volume

Increased intrapleural pressure and alveolar pressure (above atmospheric)

Hence expiration initiated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Describe the mechanism for forced expiration in terms of pressures

A

Contraction of chest wall muscles results in even higher increase in intrapleural pressure, increasing expiratory rate further

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Which part of the lung receives more ventilation per unit?

A

Lower part of the lung

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Why does lower part of lung experience more ventilation?

A

Gravity (due to the weight of the lung) means increased pleural pressure at the base (making it less negative).

Reduce the alveolar volume so are smaller percentage of max volume (pre-inspiration).

This gives each alveoli as greater ventilation potential so more compliant and so capable of more oxygen exchange whereas the apex ventilates less efficiently since its compliance is lower and so smaller volumes are exchanged.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What happens to regional ventilation differences when person is supine?

A

Apical and basal ventilation become same

Posterior aspects of lung are best ventilated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

How is FRC measured?

A

Can’t use spirometer

Use helium dilution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

How does helium dilution work?

A

Helium gas used as indicator (known volume and concentration)

Use concentration of helium in expired air to work out difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

How can regional ventilation be detected?

A

Analyse distribution of inhaled radioactive gas (133Xe)

Single breath of 133Xe taken and breath held while counts taken at different levels of lung

133Xe breathed to and from until evenly mixed in lungs to estimate volume at each level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is meant by compliance?

A

Measure of the pressure required to inflate lungs by a certain incremental volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What are the units for compliance?

A

ml/cmH2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Equation for compliance

A

delta V/delta P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Which forces work to deflate the lungs (acting against pressure to inflate lungs)?

A

Inherent elasticity of lungs

Forces which arise due to surface tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What happens to compliance in obstructive diseases, why?

A

Increases

Poor elastic recoil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What reduces compliance in normal breathing?

A

Airways resistance and other frictional forces

48
Q

What is total compliance equal to?

A

Chest compliance and lung compliance

49
Q

What is meant by surface tension?

A

Tendency of fluid surfaces to shrink into minimum surface area possible

50
Q

What does high surface tension mean for lungs?

A

They are more stiff and less compliant (more pressure needed for same volume change)

51
Q

Why is surfactant beneficial?

A

Normal water air surface, tension -70mN/m (lungs too stiff and need too much pressure to inflate).

Surfactant reduces surface tension (to 20mN/m) renders lungs more compliant, reduces work of breathing

52
Q

From when and which cells is surfactant secreted?

A

From 30 weeks gestation, type 2 alveolar cells

53
Q

What happens to surfactant and surface tension upon alveolar inflation?

A

Surface area of surfactant film increases, surface tension is increased

54
Q

What is the benefit of surface tension increasing when alveoli inflate?

A

Prevents smaller alveoli entering into larger ones (Smaller alveoli require greater transmural pressures to remain inflated) so increasing surface tension increases pressure (p=2T/r)

55
Q

What happens when insufficient surfactant in premature babies?

A

IRDS - lungs collapse as surface tension too high on exhalation

Lungs damaged by high pressures used to ventilate them, may cause atelectasis (lung collapse)

56
Q

How does pulmonary oedema lead to difficulty inflating lung?

A

Air water interfaces, so compliance decreases

Harder to inflate lungs and struggle to breathe.

57
Q

What happens in simple pneumothorax?

A

Non expanding collection of air around lung occurs spontaneously (air enters through damaged visceral pleura)

58
Q

What are the symptoms of tension pneumothorax?

A

Resonant percussion and hyperexpanded chest on affected side

Lung collapse, absent breath sounds on affected side

Tracheal deviation to opposite hemithorax

Tachypnoea

Obstructed venous return to heart, decrease CO, tachycardia

59
Q

What are the two types of air flow in the lungs?

A

Turbulent vs laminar flow

60
Q

In the lungs, the conditions are normally … flow?

A

Laminar

61
Q

Normal bronchial tree exhibits both laminar and turbulent flow, true or false?

A

True

62
Q

What sound effect arises due to turbulent flow?

A

Wheezing

63
Q

What determines if flow is turbulent or laminar?

A

Reynolds number
<2000 then Laminar
>2000 then Turbulent

64
Q

What does equation of laminar flow suggest?

A

Flow directly proportional to pressure gradient (constant=Poiseuille’s law)

65
Q

How does turbulent flow relate to pressure gradient?

A

Flow directly proportional to square root pressure gradient

66
Q

How is air resistance calculated?

A

Flow=pressure difference/resistance

67
Q

Three facts needed to calculate the airways resistance

A

Mouth pressure
Alveolar pressure
Rate of air flow

68
Q

How is mouth pressure calculated?

A

Manometer

69
Q

How do we calculate (estimate) alveolar pressure?

A

Body plethysmograph/a sealed box, need to know volume of lung and box, and measure pressure of box, then P1V1=P2V2

70
Q

Equation for airways resistance

A

delta pressure/flow

71
Q

At rest describe flow between alveoli and atmosphere

A

No flow

72
Q

What is the peak expiratory flow rate?

A

Measure of maximum speed of expiration (L/min)

73
Q

How do we measure peak expiratory flow rate?

A

Flow meter

74
Q

In forced expiration, why is there a certain PEF rate above which expiratory effort doesn’t increase expiratory rate?

A

In forced expiration, intrapleural pressure rises this compresses airways which increases resistance and decreases airflow

75
Q

How does peak flow rate vary with lung volume, why?

A

Decreases as lung volume decreases due to increased resistance

76
Q

Compare and contrast flow in submaximal and maximal effort for exhalation

A

Maximal effort: higher initial flow but then gas can’t come out at higher rate (effort independent) so gas flow becomes same as rate of submaximal effort

77
Q

Why may pressure in alveoli be greater than pressure in airways during quiet expiration?

A

Resistance to flow as you go along airways

78
Q

Why is the pressure difference of inside and outside of alveoli always +8?

A

Pressure outside alveoli (in pleural space) is more -ve than in alveoli but difference always +8 because of innate tendency of lung to collapse (prevent collapse).

79
Q

When do the airways collapse?

A

Pressure difference inside airways and outside is -11 so airways collapse

80
Q

As airways collapse, describe the resistance in the same segment of airways in submaximal and maximal effort, what’s the effect?

A

Same resistance thus same pressure gradient through same segment of airways so same flow occurs

81
Q

Describe how intrapleural and alveolar pressure change in maximal effort exhalation compared to submaximal effort?

A

Intrapleural pressure but also alveolar pressure increase (by the same value)

82
Q

Why is high airways resistance clinically significant? Give an example.

A

High resistance gives low maximal expiratory rate (e.g. asthma) so limits flow rate out of lung

83
Q

How can emphysema lead to less flow out of lungs?

A

Low lung elasticity gives poor airways support and easy collapse

Less pressure difference across alveoli at given volume so less support to wall and collapses at lower pressure

Difference across airways also decreases and pressure gradient from alveoli to airways decreases so less flow

84
Q

How does airways close physiologically?

A

At residual volume, lower part of lung in state of compression which closes airways so no further gas exhaled (gas trapping)

85
Q

What happens to airways as you begin inspiration from residual volume?

A

Initially upper part of lung only will inflate until negative pleural pressures lower done

86
Q

How does emphysema lead to intermittent ventilation of lower parts of lung?

A

Loss of elasticity leads to positive intrapleural pressures and airway closure lower down at higher lung volumes

87
Q

What are the symptoms of emphysema?

A

Barrel chest, increased FRC, intermittent ventilation of lower parts of lung, hyperventilation

88
Q

How can airways be closed pathologically?

A

Bronchiolar constriction (e.g. asthma, anaphylaxis, COPD e.g. chronic bronchitis)

Increases airways resistance

89
Q

Why do emphysema patients have broader chests?

A

Increased FRC as lungs more compliant and equilibrium between inward recoil of lung and outward recoil of chest wall disturbed

Relatively unopposed outward recoil of chest wall

90
Q

What is forced expiratory volume in one second (FEV1)?

A

Volume of air exhaled during forced breathe in one second

91
Q

What is FEV1/FVC ratio comparing, what is the normal value?

A

Volume of air expelled in one second to volume of air expelled in total after deepest breath possible.

Normally above 70% (around 80%)

92
Q

What is the FEV1/FVC ratio used for?

A

Distinguish between obstructive and restrivtive diseases

Indicate degree of obstruction in obstructive diseases

93
Q

How can you diagnose obstructive airways disease?

A

If FEV1/FVC ratio less than 70% then may have COPD or asthma

94
Q

How can you use a spirometer to measure resistance?

A

Calculate change in volume over time

95
Q

What could lower lung volume?

A

Damage to phrenic nerve
Kyphosis
Pneumothoax
Restrictive airways disease

96
Q

Examples of obstructive and restrictive airways disease

A

Obstructive: reversible e.g. asthma, or irreversible e.g. COPD

Restrctive: pulmonary fibrosis, Duchenne’s, kyphscoliosis

97
Q

How can chance of pulmonary oedema be reduced (surface tension)?

A

Lower surface tension, reduce chance of alveoli collapse and pulmonary oedema

98
Q

Compare the compliance of lungs and thorax together in intact animal compared to just lungs themselves

A

The compliance of lungs and thorax together in intact animal is half that of the lungs on their own

99
Q

Describe IP pressure relative to atmospheric pressure in normal expiration

A

Still lower than atmospheric pressure (-1cmH2O)

100
Q

Which gases diffuses better within the alveolus?

A

Oxygen (lighter)

101
Q

How can diffusion of gases be increased voluntarily?

A

Hyperventilation to increase SA of alveoli

102
Q

Does anatomical dead space change? When?

A

Inspiration, it increases

103
Q

What affects FRC, what doesn’t?

A

Height, age doesn’t

104
Q

Compare IA pressure and IP pressure

A

IA pressure normally greater

105
Q

What does oxygen diffusion in pulmonary capillaries depend on?

A

Perfusion dependent, need alveolar capillary gradient

106
Q

What is the main component in the work of breathing?

A

Overcome elastic forces of lungs

107
Q

What sort of molecule is surfactant?

A

Phopholipid and protein (not glycoprotein)

108
Q

Why is surfactant less effective at reducing surface tension at larger lung volumes?

A

Surfactant concentration is decreased in larger alveoli

109
Q

True or false and why: low oxygen tensions aggravate V/Q mismatches?

A

False, hypoxia induces pulmonary vascular vasoconstriction to improve V/Q mismatching

110
Q

How much is the physiological dead space?

A

Just >150ml

111
Q

Alveolar PO2 is greater at the … of the lung?

A

Apex

112
Q

What is the main lipid component of surfactant?

A

Dipalmitoylphosphatidylcholine

113
Q

In pulmonary emphysema, what happens to lung compliance ?

A

Increases

114
Q

What is the intrapleural pressure at the base vs the apex of the lung?

A

Apex = -15cmH2O
Base = -7cmH2O
Gravity

115
Q

Where does airways resistance arise mainly from?

A

Trachea and main bronchi

116
Q

The compliance of the lungs and thorax together in an intact animal is

A

Half that of the lungs on their own.

Pulmonary physiology (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions