Respiratory Physiology 3 Flashcards

1
Q

Define ‘pulmonary ventilation’

A

Total air movement into/out of lungs

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2
Q

Define ‘Alveolar ventilation’

A

Volume of fresh air getting to alveoli and therefore available for gas exchange

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3
Q

How would you calculate alveolar ventilation?

A

((tidal volume) - (dead space)) x respiratory rate

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4
Q

What is the typical total tidal volume per min

A

4.2L

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5
Q

Describe hypoventilation

A

Breathing real fast

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6
Q

Describe hyperventilation

A

Breathing real slow

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7
Q

Describe the typical value of anatomical dead space in the respiratory system

A

150ml

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8
Q

Define ‘dead space’

A

Dead space is air from alveoli which was not fully exhaled as the prerequisite dead air was exhaled in its place making breathing only ever 70% effective

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9
Q

Describe the composition of air

A

79% nitrogen
21% oxygen
tiny bit CO2 which we ourselves make

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10
Q

What gas is the brain most sensitive to in terms of respiration?

A

Carbon dioxide

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11
Q

Describe the impact dead space has on alveolar ventilation

A

It limits the amount of fresh air getting to the alveoli, reducing gas exchange

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12
Q

Define ‘daltons law’

A

The total pressure of a gas mixture is the sum of the pressures of the individual gasses

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13
Q

Why is the partial pressure of oxygen in alveoli < in air

A
  • Dead space in air gets sucked down into alveoli and residual volume which dilutes down the air we breathe in
  • Air becomes saturated by water vapour in the lungs
  • Pressure of gas in equilibrium with pressure of gas in blood
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14
Q

Is there more compliance at the front or the back of the lung?

A

More compliance at the back than at the front of the lung

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15
Q

What are the changes in alveolar ventilation with height from base to apex?

A

It declines due to changes in compliance

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16
Q

What is the normal alveolar partial pressure and therefore systemic arterial partial pressure of oxygen?

A

100mmHg = 13.3kPa

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17
Q

What is the normal alveolar partial pressure and therefore systemic arterial pressure of carbon dioxide?

A

40mmHg = 5.3kPa

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18
Q

Pulmonary artery carries _________ blood ____ from heart to the lungs

A

Deoxygenated blood away from the heart to the lungs

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19
Q

Pulmonary vein carries __________ blood _____ the heart from the lungs

A

Oxygenated blood towards the heart from the lungs

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20
Q

Pulmonary circulation is only concered with?

A

Gas exchange

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21
Q

Pulmonary circulation is described as what type of system in relation to flow and pressure

A

High flow low pressure system

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22
Q

What is the typical pressure within the pulmonary circulation?

A

25/10 mmHg

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23
Q

What does a ‘A’ represent

A

Alveolar

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24
Q

What does ‘a’ represent

A

Arterial

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25
Q

what does ‘v’ represent

A

Venous mixed blood (eg in pul artery)

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26
Q

What dopes PaO2 represent?

A

Partial pressure of oxygen in arterial blood

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27
Q

What does PACO2 represent

A

Partial pressure of carbon dioxide in alveolar air

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28
Q

What are the typical pressure values of PAO2 and PaO2

A

100mmHg and 13.3kPa

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29
Q

What are the typical pressure vales of:

  • PACO2
  • PaCO2
  • PvO2
A

40mmHg and 5.3kPa

30
Q

Explain why the diffusion of gasses between the alveoli can be described as ‘obeying the rules for simple diffusion’

A

As gas will move across a membrane that is permeable to that gas, down it’s partial pressure gradient and will continue to do so until it reaches an equilibrium

31
Q

The rate of diffusion across the membrane is directly proportional to what 3 things?

A

Directly proportional to:
Partial pressure gradient
Gas solubility
Available surface area

32
Q

The rate of diffusion across the membrane is inversely proportional to what factor?

A

The thickness of the membrane

33
Q

Is the rate of diffusion most rapid over a short or long distance

A

Short

34
Q

What is the partial pressure difference for oxygen and carbon dioxide between the alveoli and peripheral cells

A

6mmHg for CO2
60mmHg for oxygen

35
Q

Explain why the rate of diffusion between oxygen and carbon dioxide is similar despite the large difference in partial pressure gradients between the 2 gasses

A

As carbon dioxide is more soluble than oxygen
Meaning that it can diffuse much faster than you could otherwise predict with partial pressure gradient

36
Q

What is the effect of the oxygen partial pressure gradient on metabolism and waste products

A

It insures that cells metabolise oxygen and produce carbon dioxide as a waste product

37
Q

Is there more CO2 in cells or in venous circulation?

A

Cells

38
Q

What is the effect of the carbon dioxide partial pressure gradient on the movement of CO2 between the venous circulation and peripheral cells?

A

It ensures that CO2 is driven out of cells and into alveoli

39
Q

Define ‘systemic venous pressures’

A

Partial pressure in peripheral tissues

40
Q

Define ‘Systemic arterial pressures’

A

Partial pressure in the alveoli

41
Q

Define emphysema

A

destruction of the alveoli resulting in reduced surface area for gas exchange

42
Q

Describe the effects of emphysema

A
  • Less oxygen can enter blood
  • Pul vein and systemic arterial blood lower partial pressure of PO2
  • Increased complaince
43
Q

Describe a cause of emphysema and the mechanism it causes

A

Brought on by smoking
- Starts enzyme called elastase which breaks down the elastic tissue which reduces the surface area as results in massive alveoli

44
Q

Define fibrosis

A

Fibrous tissue being laid down alongside elastic tissue which ends up forming across alveolar type 2 cells and capillary

45
Q

Describe the effects of fibrosis

A
  • thickening alveolar membrane
  • Slowing gas exchange
  • Loss of lung compliance which may decrease alveolar ventilation
  • Blood leaving lungs -> lower PO2 than normal
46
Q

Define ‘pulmonary oedema’

A

Fluid building up between alveolar and blood vessels

47
Q

Describe the effects of a pulmonary edema

A
  • Increase distance over which gas has to diffuse
  • Decreased partial pressure of oxygen in systemic circulation
  • Normal carbon dioxide pressure in A, (not very typical of lung disease)
48
Q

Describe the typical cause of pulmonary edemas and its subsequent mechanism

A

Pulmonary Hypertension
- Forces plasma out of capillaries and pools in interstitial space

49
Q

Define ‘Asthma’

A

Increased airway resistance causing decreased airway ventilation

50
Q

Describe the effects of asthma

A

Contraction/inflammation within the bronchiole smooth muscle resulting in restricted ventilation
- Reduction of partial pressure of oxygen in alveoli and systemic circ.

51
Q

Define ‘obstructive lung disease’

A

Obstruction of airflow, especailly on epxiration

52
Q

Describe the 2 conditions that make up COPD

A

Chronic bronchitis - inflammation of bronchi
Emphysema - destruction of alveoli, loss of elasticity

53
Q

Describe what is meant by a ‘restrictive lung disease’

A

Restriction of lung expansion

54
Q

Give some examples of restrictive lung diseases (4)

A
  • Fibrosis
  • OEdema
  • Pneumothorax
  • Infant respiratory distress syndrome
55
Q

Define ‘spirometry’

A
  • Technique commonly used to measure lung function
56
Q

What are the two types of spirometry measurements that can be collected?

A

Static - where the only consideration made is the volume exhaled
Dynamic - Where the time taken to exhale a certain volume is what is being measured

57
Q

Spirometry can measure anything which does not contain ______ __________

A

Residual volume

58
Q

Give some examples of what spirometry can measure

A
  • tidal volume
  • Inspiratory reserve volume
  • Inspiratory capacity
  • Vital capacity
  • Expiratory reserve volume
59
Q

What does ‘FEV’ stand for?

A

Forced Expiratory Volume

60
Q

What does ‘FVC’ Stand for?

A

Forced vital Capacity

61
Q

What is a typical FEV value of a fit, young, healthy male

A

5L

62
Q

What does FEV1 stand for?

A

Forced expiratory reserve volume in 1 second

63
Q

What is the typical value of FEV1/FVC

A

80%

64
Q

What are the limitations of the FEV1/FVC ratio?

A

Obstructive: both FEV and FVC fall but more so, so ratio is reduced
Restrictive: Both FEV and FVC fall so ratio remains normal or perhaps may even increase despite severe compromise of function.
Therefore the ratio is NOT indicative of health

65
Q

Describe the spirometry readings typically from a case of COPD

A

COPD = obstructive disease meaning rate at which air is exhaled is much slower.
FVC is reduced
FEV1 is reduced to a greater extent than FVS
Ratio is also reduced

66
Q

Describe the spirometry readings typically from a case of pulmonary fibrosis

A

pulmonary fibrosis = restrictive disease meaning absolute rate of airflow is reduced due to total lung volume being reduced
Total volume is reduced due to limitations on lung expansion
Ratio remains constant or can increase as a large proportion of volume can be exhaled within the first second

67
Q

Is a large or small decrease in intrapleural pressure required to start inspiration?

A

Large

68
Q

Is a large or small decrease in intrapleural pressure required to start inspiration?

A

Small

69
Q

Compliance increases and decrases in what phases of respiration

A

Increases during inspiratory phase
Decreases during expiratory phase

70
Q

Why are inspiratory and expiratory curves not superimposed on one another?

A
  • The need to overcome lung inertia during inspiration
  • The need to overcome surface tension during inspiration
  • As during expiration compression of the airways means more pressure is required for air to flow among them
71
Q

A shift to the left of this graph would indicate what?

A

Obstructive lung disease

72
Q

A shift to the right of the graph below and an increase in the change of partial pressure required for inspiration and expiration would indicate what?

A

Decreased compliance