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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

Define what is meant by lung volumes and lung capacity?

A

Lung volumes and lung capacities refer to the volume of air in the lungs at different phases of the respiratory cycle. The average total lung capacity of an adult human male is about 6 litres of air.

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2
Q

What is inspiratory capacity?

A

The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration.

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3
Q

What is inspiratory capacity a sum of?

A

It is the sum of the TIDAL VOLUME and the INSPIRATORY RESERVE VOLUME.

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4
Q

What is expiratory reserve volume?

A

The extra volume of air that can be expired with maximum effort beyond the level reached at the end of a normal, quiet expiration

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5
Q

What is residual volume?

A

The volume of air remaining in the lungs after maximum forceful expiration

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6
Q

What is vital capacity?

A

The greatest volume of air that can be expelled from the lungs after taking the deepest possible breath

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7
Q

What is inspiratory reserve volume?

A

The extra volume of air that can be inspired with maximal effort after reaching the end of a normal, quiet inspiration.

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8
Q

What is tidal volume?

A

The amount of air that moves in or out of the lungs with each respiratory cycle

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9
Q

What is functional residual capacity?

A

The volume remaining in the lungs after a normal, passive exhalation.

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10
Q

What is total lung volume?

A

The volume of air in the lungs upon the maximum effort of inspiration.

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11
Q

What is FEV1?

A

The volume expelled in the first second of forced expiration.

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12
Q

What is FVC?

A

The volume expelled from maximal inspiration to forced maximal expiration.

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13
Q

What is FEV1/FVC ratio?

A

Proportional volume breathed out in first second compared to whole breath.

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14
Q

What percentage of FEV1 indicate a lung disease?

A

<80% predicted

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15
Q

What happens to the FEV1 in obstructive disease?

A

FEV1 is reduced in obstructive because there is airway resistance to expiratory flow.

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16
Q

What happens to the FEV1 in restrictive disease?

A

FEV1 is also reduced in restrictive because there is decreased compliance and elasticity so lungs can force air out quickly.

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17
Q

What else is FEV1 volume used for?

A

It is used in COPD to grade the severity.

  • Mild (50-80%)
  • Moderate (30-50%)
  • Severe (<30%)
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18
Q

What happens to the FVC in restrictive disease?

A

<80% is indicative of restrictive disorder due to decreased lung expansion so the volume the lungs can hold is reduced.

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19
Q

What value of FVC is indicative of obstructive disease?

A

There is airway resistance to expiratory flow, but a normal volume of air in the lungs - so the FVC is normal.

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20
Q

What ratio of FEV1/FVC is indicative of obstructive?

A

<0.7%

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21
Q

What ratio of FEV1/FVC is indicative of restrictive?

A

> 0.8%

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22
Q

Describe the effect of obstructive disorders of FEV1/FVC ratio

A

Obstructive disorders result in obstructive airways creating airway resistance to expiratory flow so the patient will struggle to get the air out quickly resulting in a FEV1.

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23
Q

Describe the effect of restrictive disorders of FEV1/FVC ratio

A

Restrictive disorders result in restricted lung expansion, reducing the amount of air the lungs can hold, resulting in decreased FVC.
As there is decreased compliance and elasticity it is also harder for the lungs to force out air quickly resulting in decreased FEV1.
Since both FEV1 and FVC is decreased, the FEV1/FVC ratio remains same.

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24
Q

What is restrictive disorder?

A

A restrictive disorder results in expansion of the lungs due to stiffness of the lungs.

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25
Q

Give examples of restrictive disorders

A
  • Pulmonary Fibrosis
  • Sarcoidosis
  • Obesity
  • Muscular dystrophy
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26
Q

What is obstructive disorder?

A

An obstructive disorder is when the airways are narrowed. Hence, air is exhaled more slowly than normal.

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27
Q

Give examples of obstructive disorders

A
  • COPD
  • Asthma
  • Cystic fibrosis
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28
Q

Define airway resistance

A

It is defined as the change in transpulmonary pressure needed to produce a unit flow of gas through the airway of the lungs.

In simple terms, it is a pressure difference between the mouth and alveoli, divided by airflow.

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29
Q

Name 3 factors that can influence airway resistance

A
  • Airflow velocity
  • Diameter of the airway
  • Lung volume
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30
Q

What is the major site of resistance?

A

Medium sized bronchi and very small bronchioles

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31
Q

What is Helium dilution?

A

The helium dilution technique is the way of measuring the functional residual capacity of the lungs.

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32
Q

Describe the steps of helium dilution process.

A
  • Patient inhales the gas
  • After breathing, the conc. of helium in lungs and container stabilises.
  • The conc. of the container can be used to calculate the volume of the lungs and container.
33
Q

Why is helium used in helium dilution?

A

Helium does not cross the barrier between the alveoli and the blood.

34
Q

What are different types of Asthma?

A
  • Atopic asthma
  • Non-atopic asthma
  • Drug induced asthma
  • Occupational asthma
  • Exercise induced asthma
35
Q

Name 3 processes of respiration

A
  • Ventilation
  • Pulmonary respiration
  • Tissue respiration
36
Q

At rest, what is the normal breaths per minute?

A

12-15 bpm

37
Q

Describe the process of gas exchange.

A

The air mixes with the gas in the alveoli and by simple diffusion oxygen enters the blood in the pulmonary capillaries while carbon dioxide enters the alveoli.

38
Q

What are two zones of the respiratory system?

A
  • Conducting zone
    - Trachea, bronchi, bronchioles, terminal bronchioles
  • Respiratory zone
    - Resp. bronchioles, alveolar ducts, alveolar sac
39
Q

What is dead space?

A

Area that does not take part in the gas exchange.

40
Q

What is alveolar dead space?

A

Alveoli that have lost their blood supply (such as pulmonary embolism)

41
Q

Define surface tension

A

It refers to the attraction between molecules at a gas/liquid interference causing a pull to those molecules together.

42
Q

Describe the role of surface tension in alveoli

A
  • In spherical shapes (such as alveoli), the pressure within the alveolus is increased.
  • The smaller the alveoli, the greater the pressure.
    - Small alveoli have more tendency to collapse than larger ones.
43
Q

What can reduce surface tension?

A

Surfactant - allows alveoli to expand.

44
Q

What is a surfactant?

A

It is a mixture of phospholipids produced by type II alveolar cells.

45
Q

What happens when the alveolus shrinks?

A

It’s surface area diminishes and the surface conc. of surfactant rises.

46
Q

What gradient does the air travel in?

A

Air moves from an area of higher conc. to an area of lower conc.

47
Q

Describe the gradient during inspiration and expiration.

A

During inspiration, area of high pressure is the external world. Whereas, during expiration, area of high pressure is the lungs.

48
Q

What is Boyles Law?

A

It states that if the volume increases, the pressure decreases and vice versa.

49
Q

Describe the lung pressure during inspiration.

A

Lung pressure is decreased below atmospheric pressure causing air to move into the lungs.
- Lungs expand (Increase volume)

50
Q

What is a function of inspiratory muscles?

A

They all act to increase the thoracic cage, causing intrapleural and alveolar pressure to fall to create an alevolar-mouth pressure gradient, causing air to come into lungs.

51
Q

Name 3 accessory muscles used in breathing.

A
  • Stenomastoids
  • Scalene
  • Serratus anterior
52
Q

Name 2 expiratory muscles

A
  • Rectus abdominis

- External and internal oblique

53
Q

Name 2 inspiratory muscles

A
  • Diaphragm

- External intercostals.

54
Q

Give characteristics of the alveolar wall

A
  • Alveolar walls are moist allowing gases to dissolve.
  • They have a large surface area.
  • They are one layer thin cells creating a short diffusion path which increase rate of diffusion.
55
Q

How is diffusion affected in Emphysema?

A

Loss of alveolar surface causes decreased diffusion of oxygen.

56
Q

What does Adolf Fick’s law state?

A

The rate of gas transferred across a membrane is directly proportional to the difference in partial pressures on the two sides of the membranes which depends on 4 factors.

57
Q

What 4 factors are mentioned in Fick’s law?

A
  • Membrane thickness (less thick)
  • Small molecular weight molecule
  • Increased pressure
  • Increased area
58
Q

Diffusion is very short in healthy individuals, under what circumstances can diffusion increase?

A
  • Fluid in the lungs (Pneumonia)

- Mucus in the lungs (Cystic fibrosis)

59
Q

Define lung compliance

A

The ease at which the lungs and the thoracic cage can be expanded at.

60
Q

What is the formula for lung compliance?

A

Volume / pressure = Compliance

61
Q

When is lung considered to be highly compliance?

A

High change in volume and small change in pressure suggests that the lung is highly compliance and vice versa.

62
Q

What does lungs having high compliance mean?

A

High compliance means that the lungs can stretch easily for smaller pressure.

63
Q

What is re-coiling?

A

Lungs would want to return back to their shape, called elastic re-coiling.
- Comes from the elastin forces which are in the connective tissue.

64
Q

Does surfactant increase lung compliance?

A

Yes

65
Q

What is the function of Alveolar type I cells?

A

Their thin cytoplasm allows gas exchange.

66
Q

What is the function of Alveolar type II cells?

A

They release surfactant which decreases the surface tension.

67
Q

Define ventilation

A

Amount of air in the alveoli.

68
Q

Define perfusion

A

Amount of blood moving past alveoli that can participate in gas exchange.

69
Q

What is the V/Q optimal ratio?

A

1 (for the whole lung= 0.8)

70
Q

What is shunt?

A

Area of tissue that are perfused but not ventilated are referred to as shunt.

71
Q

Where in the lung does the ventilation increase?

A

Ventilation increases from the top to the bottom of the lungs.

72
Q

What happens when ventilation is less than perfusion?

A
  • Decreased ventilation and increased perfusion of the alveoli causes local increase in carbon dioxide and decreased oxygen.
  • Pulmonary arterioles serving these alveoli constricts.
  • Results in decreased ventilation and ventilation.
73
Q

What happens when ventilation is greater than perfusion?

A
  • Increased ventilation and decreased perfusion of the alveoli causes local decrease in carbon dioxide and increased oxygen.
  • Pulmonary arterioles serving these alveoli dilate.
  • Results in increased ventilation and ventilation.
74
Q

List 3 causes of decreased V/Q ratio

A
  • Chronic bronchitis
  • Asthma
  • Pulmonary oedema
  • Pulmonary fibrosis
75
Q

What happens during a decreased V/Q ratio?

A

Although there is blood passing the alveoli; gas exchange is limited due to less air. Thus, levels of oxygen decreases and carbon dioxide increases.

76
Q

List 2 causes of increased V/Q ratio

A
  • Pulmonary embolism

- COPD

77
Q

What happens during a increased V/Q ratio?

A

Although there is plenty of air getting into the alveoli; oxygen is not getting into the blood and carbon dioxide is not getting out efficiently.

78
Q

What are the controllers of respiration/ventilation?

A

The respiratory centres

Respiratory (5 decks)

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