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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

What is internal respiration?

A

The intracellular mechanisms which consumes O2 and produces CO2.

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2
Q

What is external respiration?

A

The sequence of events that leads to the exchange of O2 and CO2 between the external environment and the cells of the body.

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3
Q

What are the four steps of respiration?

A
  1. Ventilation
  2. Exchange of O2 and CO2 between air in lungs and blood
  3. Transport of O2 and CO2 to tissues
  4. Exchange of O2 and CO2 between blood and tissues
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4
Q

What are the four systems involved in external respiration?

A
  1. The respiratory system
  2. The cardiovascular system
  3. The haematology system
  4. The nervous system.
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5
Q

What is ventilation?

A

The mechanical process of moving air between the atmosphere and the alveolar sacs.

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6
Q

What is inspiration?

A

An active process brought about by contraction of inspiratory muscles.

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7
Q

What is resting expiration?

A

This is a passive process brought about by the relaxation of the respiratory muscles.

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8
Q

What forces can reduces lung expansion?

A

Elastic resistance of the lungs and chest wall.

Non-elastic resistance (airway resistance).

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9
Q

Name the forces keeping the alveoli open?

A 
Transmural pressure gradient.
Pulmanory surfactant (reduces alveolar surface tension).
Alveolar interdependence.
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10
Q

Name elastic forces promoting alveolar collapse.

A

Elastic recoil of the lungs and chest wall

Alveolar surface tension.

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11
Q

What is the transmural pressure gradient?

A

The difference between intrathoracic and alveolar pressure.

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12
Q

What is pulmonary surfactant?

A

A mixture of lipids and proteins secreted from type II alveoli.

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13
Q

What is alveolar interdependence?

A

This is essentially the elastic recoil of the alveoli. The alveoli are interconnected, therefore if one alveoli collapses, the surrounding alveoli will help keep it open.

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14
Q

What is the elastic recoil of the lungs and chest wall?

A

Following inhalation, the lungs will rebound after being streched.

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15
Q

What is alveolar surface tension?

A

The alveoli are lined with a thin film of water. the attraction between them creates a force called alveolar surface tension.

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16
Q

How do the lungs adhere to the chest wall and follow its movement?

A

Transmural pressure gradient.

The intrapleural fluid cohesiveness.

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17
Q

What is intrapleural fluid cohesiveness?

A

The water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart.

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18
Q

Name the three types of pressure that are important in ventilation.

A

Atmospheric Pressure
Intra-alveolar (Intrapulmonary) Pressure
Intrapleural (Introthoracic) Pressure

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19
Q

What is atmospheric pressure?

A

The pressure caused by the weight of the gas in the atmosphere on the Earth’s surface.
Normally 760 mmHg @ sea level.

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20
Q

What is intra-alveolar pressure?

A

The pressure within the lung alveoli.

Normally 760 mmHg when equilibrated with atmospheric pressure.

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21
Q

What is intrapleural pressure?

A

Pressure exerted outside the lungs within the pleural cavity. This is a sub-atmospheric value.

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22
Q

How is the transmural pressure gradient calculated?

A

Across the lung wall:
TP = Intra-alveolar pressure - intrapleural pressure.

Across the thoracic wall:
TP = Atmospheric pressure - Intrapleural pressure.

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23
Q

Describe the relationship between transmural pressure gradient and expansion of the lungs.

A

As the transmural pressure gradient dincreases, the lung volume increases. (DIRECT RELATIONSHIP)
Due to this pressure gradient, we will never be able to expire all the air out of the lungs.

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24
Q

What is a Pneumothorax?

A

Air in the pleural space. This can be spontaneous, traumatic or iatrogenic (from medical procedures).
The air can enter this space either from outside the body or from the lungs.

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25
Q

How does pneumothorax lead to lung collapse?

A

The entrance of air abolishes the transmural pressure gradient, by increasing the intrathoracic pressure. This leads to lung collapse

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26
Q

What are some symptoms of pneumothorax?

A

Shortness of breath

Chest pain

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27
Q

What are some of the physical signs of pneumothorax?

A

Hyperresonant percussion note - due to increased air.

Decreased/Absent Breath Sounds.

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28
Q

State Boyle’s Law.

A

At any constant temperature the pressure exerted by a gas varies INVERSELY with the volume of the gas.

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29
Q

What does Boyle’s Law mean for inspiration?

A

The intra-alveolar pressure must become less than the atmospheric pressure for air to flow into the lungs during inspiration.
Before inspiration, intra-alveolar pressure = atmospheric pressure.
During inhalation, the lungs expand, making the intra-alveolar pressure fall as the volume is increasing (Boyle’s Law).

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30
Q

Name the muscles that allow for the expansion of the chest during inspiration.

A

Diaphragm - increases vertical diameter of the chest.

External intercostal muscle _ increases anteriopostal diameter of the chest (bucket handle mechanism)

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31
Q

What does Boyle’s Law mean for expiration?

A

The recoiling of the lungs means that the alveolar pressure rises because their volume is decreased. The air will then leave the lungs down a pressure gradient.

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32
Q

How does the Law of LaPlace relate to the alveoli?

A

The smaller the alveoli, the higher tendency they have to collapse.

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33
Q

How does pulmonary surfactant work?

A

It lowers the alveolar surface tension by interspersing the water molecules lining the alveoli. It lowers that surface tension of small alveoli more than that of large alveoli to prevent the small alveoli form collapsing.

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34
Q

State the equation relating to LaPlaces Law.

A

P (inward directed collapsing pressure) = 2 x Surface Tension / Radius of the alveoli.

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35
Q

Describe respiratory distress syndrome of the new born.

A

A developing foetus is unable to synthesise pulmonary surfactant until late in pregnancy. Premature babies may not have enough surfactant. The baby will therefore make very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs.

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36
Q

Name the accessory muscles of inspiration.

A

Sternocleidomastoid, scalenus and pectoral.

These only contract during forceful inspiration.

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37
Q

Name the muscles of active expiration.

A

Abdominal muscles, internal intercostal muscles.

These only contract during active expiration.

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38
Q

Name the static lung volumes.

A

Inspiratory Reserve Volume.
Tidal Volume
Expiratory Reserve volume
Residual volume.

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39
Q

Name the static lung capacities.

A

Functional residual capacities
Inspiratory capacity
Vital capacity
Total lung capacity.

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40
Q

What is tidal volume (TV)?

A

Volume of air entering or leaving lungs during a single breath.
Normally 0.5 L

41
Q

What is inspiratory reserve volume (IRV)?

A

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume.
Normally 3.0 L

42
Q

What is expiratory reserve volume (ERV)?

A

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after resting tidal volume.
Normally 1.0 L

43
Q

What is residual volume (RV)?

A

Minimum volume of air remaining in the lungs even after a maximal expiration. This volume can never be removed form the lungs.
Normally 1.2 L
Cannot be measured by simple spirometry.

44
Q

What is inspiratory capacity (IC)?

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration.
IC = Inspiratory reserve volume + tidal volume.
Normally 3.5 L

45
Q

What is functional residual volume (FRC)?

A

Volume of air in lungs at end of normal passive expiration.
FRC = Expiratory reserve volume + Residual volume.
Normally 2.2 L
This cannot be measured by simple spirometry.

46
Q

What is vital capacity (VC)?

A

Maximum volume of air that can be moved out during a single breath following maximal expiration.
VC = inspiratory reserve volume + tidal volume + expiratory reserve volume
Normally 4.5 L

47
Q

What is total lung capacity (TLC)?

A

Total volume of air the lungs can hold.
TLC = Vital capacity + reserve volume
Normally 5.7 L
This cannot be measured by simple spirometry

48
Q

What is airway resistance?

A

Resistance to flow in the the airway.

49
Q

Describe the normal airway resistance.

A

Airway resistance is normally very low and therefore moves air with a small pressure gradient.

50
Q

What is the primary determinant of airway resistance?

A

The radius of the conducting airway. The smaller the radius, the more the resistance.

51
Q

What does parasympathetic stimulation do to the airway?

A

Bronchoconstriction

52
Q

What does sympathetic stimulation do to the airway?

A

Bronchodilation

53
Q

What happens to intrapleural pressure during inspiration?

A

It falls

54
Q

What happens to intraplrural pressure during expiration?

A

It rises

55
Q

What is dynamic airway compression?

A

It happens when intrapleural pressure equals or exceeds alveolar pressure. This makes expiration more difficult.

56
Q

What does dynamic airway compression do in normal people?

A

It causes no problems. The increased airway resistance causes an increase in airway pressure upstream. This helps open the airways by increasing the driving pressure between the alveolus and airway.

57
Q

What does dynamic airway compression do in people with dynamic airway obstruction?

A

If there is an obstruction, the driving pressure between the alveolus and airway is lost over the obstructed segment. This causes a fall in airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration.

58
Q

What is a peak flow meter?

A

This gives an estimate of peak flow rate measured in L/min.
This will assess airway function and is useful in patients with obstructive lung diseases.
The results vary in normal adults with age and height

59
Q

How is peak flow measured?

A

The patient will give a short sharp breath into the peak flow meter.

60
Q

What is pulmonary compliance?

A

It is a measure of the effort that has to go into stretching and distending the lungs.
The less compliant the lungs are, the more work is required to produce a given degree of inflation. This causes shortness of breath.

61
Q

What is lung compliance?

A

The change in lung volume per unit change in transmural pressure gradient across the lung wall.

62
Q

What factors decrease pulmonary compliance?

A

Pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, and absence of surfactant.

63
Q

What does a decrease in pulmonary compliance cause in spirometry?

A

May cause a restrictive pattern of lung volumes.

64
Q

When would pulmonary compliance abnormally increase?

A

If the elastic recoil of the lungs is lost, in emphysema. Compliance also increases with age.

65
Q

What is work of breathing?

A

It is a reflection of energy needed to overcome impeding elements of the respiratory system.

66
Q

How much energy does quiet breathing require?

A

It requires about 3% of total energy expenditure.

67
Q

Give some examples of where breathing is increased.

A
  1. When pulmonary compliance is decreased.
  2. When airway resistance is increased
  3. When elastic recoil is decreased
  4. When there is a need for increased ventilation
68
Q

What is anatomical dead space in the airways?

A

This is areas of the airway that is not available for gas exchange. e.g the trachea

69
Q

What is the equation for pulmonary ventilation (L)?

A

Pulmonary ventilation = tidal volume x respiratory rate

70
Q

What is a the equation for alveolar ventilation?

A

Alveolar ventialtion = (tidal volume - dead space) x respiratory rate.

71
Q

Why is alveolar ventilation less than pulmonary ventilation?

A

Because of the presence of anatomical dead space therefore not as much air reaches the alveoli.

72
Q

What is the average volume of dead space in the respiratory system?

A

About 150ml

73
Q

What is pulmonary ventilation?

A

The volume of air breathed in and out per minute.

74
Q

What is alveolar ventilation?

A

The volume of air exchanges between the atmosphere and alveoli per minute.
This is more important as it represents new air available fo gas exchange with blood.

75
Q

How can pulmonary ventilation be increased?

A 
The depth (tidal volume) and respiratory rate must increase.
Due to dead space, it is more advantageous to increase the tidal volume
76
Q

What is ventilation?

A

The rate at which gas is passing through the lungs.

77
Q

What is perfusion?

A

The rate at which blood is passing through the lungs.

78
Q

What should the ventilation perfusion ratio be?

A

It should equal 1 as this will give the best concentration of gases.

79
Q

What is alveolar dead space?

A

Ventilated alveoli that are not adequately perfused with blood. `This is because the match between air in the alveoli and the blood in the pulmonary capillaries is not always perfect.

80
Q

Describe alveolar dead space in nealthy and diseased individuals.

A

In healthy people the alveolar dead space is very small and of little importance.
In diseased people, the alveolar dead space can be significantly increased.

81
Q

What is physiological dead space?

A

Anatomical dead space + alveolar dead space

82
Q

What does a an accumulation of CO2 in alveoli as a result of increased perfusion cause?

A

This decreases airway resistance and dilation of local airways leading to increased airflow.

83
Q

What does an increase in alveolar O2 concentration as a result of increased ventilation cause?

A

This causes pulmonary vasodilation which increases blood flow to match larger airflow.

84
Q

What will happen to the CO2 and O2 in an area where the perfusion is greater than ventilation?

A

CO2 increases

O2 decreases

85
Q

What will happen to the CO2 and O2 in an area where the

ventilation is greater than perfusion?

A

CO2 decreases

O2 increases

86
Q

What does decreased O2 do to pulmonary and systemic blood vessels?

A

Pulmonary arterioles - vasoconstriction

Systemic arterioles - Vasodilation

87
Q

What does increased O2 do to pulmonary and systemic blood vessels?

A

Pulmonary arterioles - vasodilation

Systemic arterioles - vasoconstriction

88
Q

What are the four factors that influence the rate of gas exchange across alveolar membrane?

A
  1. Partial pressure gradient of O2 and CO2.
  2. Diffusion coefficient for O2 and CO2
  3. Surface area of alveolar membrane
  4. Thickness of alveolar membrane
89
Q

What is daltons law of partial pressures?

A

The total pressure exerted by a gaseous mixture = the sum of the partial pressures of each individual component in the gas mixture.

90
Q

What is the partial pressure of a gas?

A

The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature.

91
Q

What is the average partial pressure of O2 in atmospheric air?

A

160 mm Hg

92
Q

What is the partial pressure of O2 in the alveolar air?

A

Atmospheric pressure - Water vapour pressure

This is normally 100 mm Hg at sea level

93
Q

What is the O2 and CO2 partial pressure gradient across pulmonary capillaries?

A

O2 partial pressure gradient from alveoli to blood = 60 mm Hg
CO2 partial pressure gradient from blood to alveoli = 6 mm Hg

94
Q

What is the O2 and CO2 partial pressure gradient across systemic capillaries?

A

O2 partial pressure gradient from alveoli to blood > 60 mm Hg
CO2 partial pressure gradient from blood to alveoli > 6 mm Hg

95
Q

What offsets the difference in partial pressure gradient for CO2 and O2?

A

CO2 is more soluble in membranes than O2.

96
Q

What is the diffusion coefficient of a gas?

A

The solubility of gas in membranes is known as the Diffusion coefficient for the gas.

97
Q

Compare the diffusion coefficient for CO2 and O2.

A

The diffusion coefficient for CO2 is 20 times that of O2.

98
Q

What is the rhythm of respiration?

A

Inspiration followed by expiration.

Respiratory (16 decks)

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