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Respiratory Medicine > Week 1- Respiratory Physiology > Flashcards

Week 1- Respiratory Physiology Flashcards

1
Q

What is the average lung volume?

A

6L

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2
Q

What is the volume of air taken in on an average inspiration?

A

2.8L

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3
Q

Define “tidal volume”

A

the volume of air that you breathe in and out at rest

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4
Q

What is the average tidal volume?

A

500ml

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5
Q

Explain what is meant by the term “functional residual capacity”

A

The residing volume of air still in our lungs at the end of a normal relaxed expiration

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6
Q

What is the average functional residual volume?

A

2.3L

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7
Q

Define the term “inspiratory reserve” and state the average respiratory reserve volume.

A

If we take a really big breath and take in as much air as we can on top of our normal tidal volume, we can take in an additional 3L of air; this is our inspiratory reserve.

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8
Q

What is meant by the term “expiratory reserve?” State the average respiratory reserve in L

A
  • Our expiratory reserve volume is the extra air that we can exhale on top of a normal exhalation (exhale normally then force further air out of the lungs. On average this is around 1L of air)
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9
Q

What is “vital capacity”?

A

the maximum amount of air that we can voluntarily expire after a maximum inspiration

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10
Q

What can vital capacity be used to measure?

A

Lung function

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11
Q

What is the difference between a capacity and a volume?

A

A capacity is made up of 2 or more different volumes added together.

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12
Q

Which capacities are added together to make the vital capacity?

A

inspiratory reserve volume + tidal volume + expiratory reserve volume.

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13
Q

Which capacities are added together to make the total lung capacity?

A

vital capacity + the residual volume

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14
Q

Which capacities are added together to make the inspiratory capacity?

A

tidal volume + inspiratory reserve volume.

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15
Q

Which capacities are added together to make the functional residual capacity?

A

expiratory reserve volume + residual volume.

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16
Q

If we expire as hard as we can, is it possible to empty the residual volume?

A

No

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17
Q

Explain why the residual lung volume cannot be forcibly expired

A

Because it plays the following 2 important roles;

  1. It stops the alveoli from collapsing (this is a means of saving energy because it would take a LOT more effort to inflate collapsed alveoli). Alveoli never fully collapse they just vary in the degree of their expansion.
  2. Residual volume provides a volume of air that allows gas exchange to continue to take place in between breaths
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18
Q

What volume of fluid is contained within the pleural cavity?

A

3ml

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19
Q

Name the two components of the pleura

A

Parietal pleura & visceral pleura

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20
Q

Where would you find the parietal pleura?

A

Stuck to the ribs & chest wall

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21
Q

Where would you find the visceral pleura?

A

The lung surface

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22
Q

Are the parietal and visceral pleura two separate membranes?

A

No they are continuous with each other at the hilum

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23
Q

What is the function of the pleura?

A

To adhere the lung to the chest wall and to allow smooth movement between the lungs and the chest wall

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24
Q

What drives the recoil of the chest wall during expiration?

A

Elastic Recoil

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25
Q

Is expiration a active or passive process?

A

Passive (except in disease)

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26
Q

What is the hilum of the lungs?

A

The hilum is the point at which the bronchi, blood vessels and other structures enter and leave the lungs

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27
Q

What does Boyle’s law state?

A

the pressure exerted by a gas is inversely proportional to its volume. Gases (singly or in mixtures) move from areas of high pressure to areas of low pressure

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28
Q

What does Dalton’s law state?

A

the total pressure of a gas mixture is the sum of the pressures of the individual gases.

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29
Q

What does henry’s law state?

A

the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid.

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30
Q

What does Charles’ law state?

A

the volume occupied by a gas is directly related to the absolute temperature

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31
Q

What happens to the pressure inside the chest when the volume increases (inspiration)

A

The pressure decreases (which helps to draw air into the lungs)

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32
Q

What happens to the pressure inside the chest when the volume decreases (on expiration)

A

The pressure increases (which helps to move air out of the lungs and back into the atmosphere)

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33
Q

What are the normal muscles of inspiration?

A

external intercostals muscles and the diaphragm

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34
Q

What are the normal + accessory muscles of inspiration?

A

external intercostals muscles, the diaphragm, the scalene and the sternocleidomastoid

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35
Q

What are the accessory muscles of expiration (remember that expiration is a passive process in healthy individuals)

A

internal intercostal and abdominal muscles

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36
Q

What nerve causes contraction (flattening) of the diaphragm?

A

The phrenic nerve

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37
Q

Is air resistance greater during inspiration or expiration? Explain the answer.

A

during inspiration the airways get stretched open. Therefore, air resistance is less during inspiration than it is during expiration

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38
Q

What action do the external intercostal muscles have upon the sternum?

A

They raise the sternum which increases the dimensions of the anterior and posterior thoracic cavity

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39
Q

What actions do the external intercostals exert on the ribs?

A

They cause them to raise in an outwards and upwards movement which increases the lateral dimension of the ribcage

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40
Q

What action do the internal intercostals have on the sternum?

A

They bring the sternum down which decreases the dimensions of the anterior and posterior cavity

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41
Q

What actions do the internal intercostals exert on the ribs?

A

Move the ribcage downwards and inwards which decreases the lateral dimension of the ribcage

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42
Q

Define “intra-thoracic (alveolar) pressure”

A

The pressure inside the thoracic cavity, (essentially pressure inside the lungs).

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43
Q

Is intra-thoracic pressure positive or negative?

A

pressure may be negative (less than atmospheric pressure) at the start of inspiration or positive (more than atmospheric pressure) at the start of expiration.

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44
Q

What is intra-pleural pressure?

A

The pressure inside the pleural cavity

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45
Q

Is intra pleural pressure positive or negative?

A

Negative

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46
Q

What is trans pulmonary pressure?

A

the difference between alveolar pressure and intra-pleural pressure

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47
Q

Is trans pulmonary pressure positive or negative?

A

It is almost always positive because Pip is negative (in health). PT = Palv – Pip.

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48
Q

What two things determine lung volume?

A
  1. Transpulmonary pressure

2. Elastic capacity of the lungs

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49
Q

What does airway resistance determine?

A

how much air flows into the lungs at any given pressure difference between atmosphere and alveoli.

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50
Q

What is airway resistance determined by?

A

The radii of the airways

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51
Q

When is alveolar pressure the same as atmospheric pressure?

A

When the air movement has stopped

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52
Q

Describe a lung pressure of 0 and of +ve 4 in relation to atmospheric pressure

A

The pressure inside the lungs is measured in comparison to atmospheric pressure. Therefore, if the reading is 0, it means that the pressure is the same as atmospheric pressure. If the reading is +ve 4, then the pressure is 4 millilitres higher than atmospheric pressure.

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53
Q

Why is intrapleural pressure always less than alveolar pressure?

A

The intrapleural pressure is generated between the chest wall and the lungs. The chest wall drives inspiration and elastic recoil drives expiration. The muscles that act upon the chest wall means that the chest wall always wants to expand so the cavity is always trying slightly to expand and increase in volume. Because it always wants to increase in volume, it is always negative (remember as you increase in volume, you decrease in pressure).

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54
Q

Which cell type produces surfactant?

A

Type 2 pneumocytes

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55
Q

What is the role of surfactant/

A

reduces surface tension on the alveolar surface membrane, thus reducing the tendency for alveoli to collapse

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56
Q

What is surface tension?

A

the attraction between water molecules which occurs when there is an air-water interface

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57
Q

Other than reducing surface tension, that other three functions does surfactant have?

A
  • Increases lung compliance
  • Reduces the lungs tendency to recoil
  • Makes the work of breathing easier
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58
Q

What is the law of LaPlace?

A

the pressure required to keep an alveoli open is 2x the surface tension divided by the radius.

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59
Q

Is the pressure required to keep an alveoli open greatest in bigger alveoli or in smaller alveoli?

A

smaller alveoli

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60
Q

Why is maintaining the inflation of smaller alveoli is more beneficial than maintaining the inflation of larger alveoli?

A

smaller alveoli have a bigger surface area to volume ratio

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61
Q

When does surfactant production occur in utero?

A

starts at 25 weeks’ gestation and is complete by 36 weeks

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62
Q

What is the production of surfactant in utero stimulated by?

A

thyroid hormones and cortisol

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63
Q

Briefly describe the physiology of Infant Respiratory Distress Syndrome

A

Babies born prematurely before 36 weeks’ gestation must overcome surface tension caused by a lack of surfactant and essentially fight to stop their alveoli from collapsing. This requires a colossal energy requirement. This is the reason that premature babies become exhausted very quickly

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64
Q

What can be administered to a premature baby after birth to help manage respiratory distress?

A

Aerosol Surfactant

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65
Q

What is the difference between lung compliance and lung elasticity?

A

Compliance is the lung stretching outwards when you breathe in, elasticity is the lung recoiling when you breathe out

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66
Q

Which three factors determine compliance?

A

Elastic forces, surface tension at the alveolar air-liquid interface and by airway resistance.

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67
Q

What happens to compliance in emphysema and why is a bad thing?

A

Emphysemic lungs have high compliance BUT they have low elasticity. High compliance is only a good thing if it is accompanied by high elasticity

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68
Q

Explain low compliance

A

a small increase in lung volume for a large decrease in intrapleural pressure.

Low compliance means you have to work very hard to get air into the lungs.

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69
Q

Name a pathology that causes low compliance

A

Fibrosis

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70
Q

Explain high compliance

A

a large increase in lung volume for a small decrease in intrapleural pressure (healthy lungs have high compliance)

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71
Q

What happens to compliance as we age?

A

Lungs loose compliance

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72
Q

What impact does surfactant have upon compliance

A

Surfactant increases compliance

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73
Q

What is a normal, average tidal volume volume?

A

500ml

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74
Q

What is a normal, average residual volume volume?

A

1200ml

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75
Q

What is a normal, average expiratory reserve volume?

A

1100ml

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76
Q

What is a normal, average inspiratory reserve volume??

A

3000ml

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77
Q

What is a normal, average vital capacity volume?

A

4600ml

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78
Q

What is a normal, average total lung capacity volume?

A

6L

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79
Q

What is the volume of the anatomical dead space?

A

150ml

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80
Q

What is ventilation?

A

The movement of air in and out of the lungs (breathing)

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81
Q

What is pulmonary/minute ventilation?

A

The total air movement in and out of the lungs

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82
Q

What is alveolar ventilation?

A

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

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83
Q

Explain the impact of the anatomical dead space on alveolar ventilation

A
  1. Upon expiration, the first air to be expelled is the 150ml sitting in the dead space. 500ml of air is pushed out of the lungs on expiration but only 350ml leaves the respiratory system completely. 150ml remains behind in the dead space.
  2. During the next inhalation, the 150ml of air in the dead space is the first to move down into the lungs. This is followed by 500ml of ‘fresh air’ however only 350ml of this 500ml reaches the lungs because 150ml is left behind in the dead space.
  3. And repeat

This means that breathing is only ever 70% effective

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84
Q

How can we change our alveolar ventilation?

A

our dead space volume is fixed but our lung capacity can vary enormously. We can therefore, change our alveolar ventilation by altering our breathing pattern

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85
Q

Should the term hyperventilation not be used to describe somebody that is breathing very fast

A

Their breathing rate may be fast but this means that their tidal volume will be low. The amount of air reaching the alveoli is therefore less so they are HYPOventilating

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86
Q

How can be pulmonary ventilation be calculated?

A

Respiratory rate x tidal volume

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87
Q

How can alveolar ventilation be calculated?

A

[Tidal volume-dead space volume] x respiratory rate

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88
Q

What is the normal alveolar partial pressure (and therefore systemic arterial PP) of O2 (in mmHg and kPa)

A

100mmHg (13.3 kPa).

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89
Q

What is the normal alveolar partial pressure (and therefore systemic arterial PP) of CO2 (in mmHg and kPa)

A

40mmHg (5.3kPa).

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90
Q

What happens to PO2 and PCO2 in hyperventilation?

A
  • During hyper-ventilation (increased alveolar ventilation) PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg.
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91
Q

What happens to PO2 and PCO2 in hypoventilation?

A
  • During hypo-ventilation (decreased alveolar ventilation) PO2 falls to 30 mmHg and PCO2 rises to 100 mmHg
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92
Q

What is the partial pressure of oxygen in the atmosphere?

A

160mmHg

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93
Q

Why is the partial pressure of oxygen in the alveoli lower than the partial pressure of oxygen in the atmosphere?

A

the air becomes diluted by The air in the anatomical dead space and the residual volume. It also becomes saturated with water. This causes the reduction in the partial pressure of O2

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94
Q

What happens to breathing rate when PaCO2 begins to rise and why?

A
  • As carbon dioxide levels creep up, centres in the brain that make us breathe are stimulated.
  • Humans are hypersensitive to changes in CO2. Too much CO2 is toxic to our cells, but not enough CO2 will stop stimulating our breathing centres and we become apnoeic
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95
Q

Where in the lung is alveolar ventilation greatest and worst?

A

greatest at the base of the lung and worst at the apex due to changes in compliance throughout the lung.

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96
Q

Where in the lung is compliance lowest and why?

A

Compliance is lower at the apex because the lungs are hanging in the thoracic cavity & the weight of the lungs causes alveoli at the apex to be open while alveoli at the base are slightly squashed by the weight of the lungs and the diaphragm. Therefore, there is much more capacity for the alveoli at the base to expand because those at the apex are already stretched open (and therefore don’t have much space to expand any further).

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97
Q

The pulmonary artery carries ______ blood ____ from the ______ to the ______

A

The pulmonary artery carries deoxygenated blood AWAY from the heart to the lungs.

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98
Q

The pulmonary vein carries _________ blood __________ the _______ from the _________

A

The pulmonary artery carries deoxygenated blood AWAY from the heart to the lungs.

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99
Q

What are the two branches of the pulmonary circulation?

A

Bronchial circulation (blood supply to the lungs)

Pulmonary circulation (gas exchange)

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100
Q

What is the blood pressure like in the pulmonary circulation compared to the systemic circulation?

A

The pulmonary circulation is a high flow, low pressure system: (the blood pressure is around 25/10mmHg vs the systemic circulation which has a pressure of around 120/80mmHg).

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101
Q

Name the two places that gas exchange occurs

A
  1. Between the pulmonary circulation and the alveoli

2. Between the systemic circulation and the tissues

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102
Q

What is the partial pressure of oxygen in the tissues?

A

40mmHg

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103
Q

Why is the pressure gradient of oxygen between the blood (100mmHg) and the tissues (40mmHg) so important?

A

It creates a gradient and facilitates the movement of oxygen into the tissue

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104
Q

What is PaO2

A

partial pressure of oxygen in arterial blood

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105
Q

What is PAO2?

A

partial pressure of oxygen in alveolar air

106
Q

What is the rate of gas diffusion across a membrane directly proportional to?

A
  • The partial pressure gradient
  • Gas solubility
  • The available surface area
107
Q

What is the rate of gas diffusion across a membrane directly inversly proportional to?

A

The thickness of the membrane

108
Q

What are the diffusion rates of oxygen and CO2?

A 
oxygen = 250ml/min 
CO2= 200ml/min
109
Q

Which is more soluble in water; O2 or CO2?

A

CO2 is FAR more soluble in water than O2

110
Q

What is spirometry used to measure?

A

Lung function

111
Q

Which lung volumes and capacities can be measured with spirometry?

A

Remember if you can’t expire it, spirometry can’t measure it!

  • Tidal volume
  • Expiratory reserve volume
  • Inspiratory reserve volume
  • Inspiratory capacity
  • Vital capacity
112
Q

What is FEV1?

A

the amount of air that can be forcibly exhaled in 1s from your lungs after taking the deepest breath possible

113
Q

What is FVC?

A

the total volume of air that can be forcibly exhaled from the lungs after taking in the deepest breath possible (in however long it takes).

114
Q

What is the average FVC of a fit, healthy young adult male?

A

5.0L

115
Q

What is a normal healthy FEV1/FVC ratio?

A

80%

116
Q

What happens to the FEV1/FVC ratio in obstructive disease?

A

Unproportional decreases in FEV1 and FVC

117
Q

What happens to the FEV1/FVC ratio in restrictive disease? 9overall ratio is decreased)

A

Proportional decreases in FEV1/FVC (so the overall ratio s unchanged)

118
Q

Which type of lung diseases (obstructive or restrictive) is spirometry good at diagnosing?

A

useful at diagnosing obstructive lung diseases.

not useful for diagnosing restrictive lung diseases because it gives a normal ratio

119
Q

What is the difference between compliance and elasticity?

A

compliance is how stretchy the lungs are on inspiration while elasticity is how much recoil the lungs have on expiration

120
Q

What happens to compliance as you move through inspiration and why?

A

At the start of inspiration, you need quite a big decrease in intrapleural pressure before you see a change in lung volume, therefore, complience increases as you move through the inspiratory phase.

121
Q

What happens to compliance as you move through expiration and why?

A

On expiration, compliance is low at the start and very little air moves out of the lungs. Compliance increases significantly and much more air is expired once intrapleural pressure has fallen. Compliance therefore decreases as you move through the expiratory phase.

122
Q

Do obstructive diseases increases the work of inspiration or expiration?

A

Obstructive diseases increase the work of expiration

123
Q

Do restrictive diseases increases the work of inspiration or expiration?

A

Restrictive diseases increase the work of inspiration

124
Q

What is lung inertia?

A

the lung not wanting to change shape

125
Q

What must be overcome during inspiration?

A

Lung inertia

126
Q

What must be overcome during expiration?

A

Surface tension

127
Q

Define ventilation

A

The amount of fresh air getting to the alveoli to engage in gas exchange(L/min)

128
Q

Define perfusion

A

The blood flow through the pulmonary circulation (L/min)

129
Q

If ventilation and perfusion matched perfectly, then the ventilation/perfusion ratio (sometimes called V/Q) would be ___.

A

1

130
Q

How do you calculate the ventilation perfusion ratio?

A

ventilation divided by perfusion (V/Q)

131
Q

What happens to blood flow and ventilation from the apex to the base of the lung and why?

A

From the apex to the base the ventilation and blood flow decrease due to changes in compliance

132
Q

What causes the small V/Q mismatch at the base of the lungs?

A

Blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure. This compresses the alveoli.

133
Q

What are the two ways in which V/Q can be mismatched?

A
  1. Ventilation is less than perfusion

2. Ventilation exceeds perfusion

134
Q

What is the ventilation perfusion ratio going to be when ventilation is less than perfusion?

A

less than 1

135
Q

What is the ventilation perfusion ratio going to be when ventilation exceeds perfusion?

A

> 1

136
Q

Where in the lung is there a significant ventilation/perfusion mismatch that is physiologically normal?

A

At the apex of the lung

137
Q

What physiological process happens when perfusion exceeds ventilation and why?

A

Shunt (pulmonary vasoconstriction and bronchial dilation occurs to redirect the blood flow away from an area that is poorly ventilated)

138
Q

What happens when ventilation exceeds perfusion?

A

“Alveolar dead space” (not enough blood passing by the alveoli for gas exchange so the air in the alveoli isn’t used and is therefore “dead air”)

139
Q

What is physiological dead space?

A

Anatomical dead space + alveolar dead space

140
Q

What is respiratory sinus arrhythmia?

A

the natural quickening of your pulse upon inspiration and the natural slowing of your pulse upon expiration.

141
Q

Why does respiratory sinus arrhythmia occur?

A

If heart rate always stayed constant, during inspiration we would have increased alveolar dead space and upon expiration we would have increased shunt.

Respiratory sinus arrhythmia therefore ensures that the ventilation/perfusion ratio stays as close to 1 as possible (matched)

142
Q

What causes respiratory sinus arrhythmia?

A

Increased vagal activity during expiration

143
Q

Describe the partial pressure of O2 and CO2 at each point;

  1. Dry inspired air
  2. Humidified Tracheal Air
  3. alveolar Air
  4. Systemic Arterial Blood
  5. resting tissue
  6. Systemic Mixed venous Blood
A
  1. Dry inspired air (PO2 = 160, PCO2= 0)
  2. Humidified Tracheal Air (PO2= 150, PCO2= 0)
  3. alveolar Air (PO2= 100, 0CO2= 40)
  4. Systemic Arterial Blood (PO2= 100, PCO2= 40)
  5. Resting Tissue (PO2= 40, PCO2= 46)
  6. Systemic Mixed venous Blood (PO2= 40, PCO2= 46)
144
Q

What is the rate of gas diffusion proportional to?

A

The partial pressure of the gas

145
Q

How does oxygen travel in the blood?

A
  1. Bound to haemoglobin

2. In solution in plasma

146
Q

How may ml of oxygen are carried per litre of whole blood?

A

200ml

147
Q

If the 200ml of oxygen carried in 1L of whole blood, how many ml are carried in plasma and how many ml are carried by haemoglobin?

A

Dissolve in Plasma= 3ml

Bound to haemoglobin= 197ml

148
Q

How is CO2 transported in blood?

A

The majority of CO2 (77%) is transported in solution in plasma. Only 23% of CO2 is transported in haemoglobin.

149
Q

Why is oxygen carried by haemoglobin rather than just dissolving in plasma?

A

It is not very soluble

150
Q

How may molecules of oxygen can each haemoglobin bind?

A

4

151
Q

What element is utilised by haemoglobin?

A

Fe2+

152
Q

Explain the concept of cooperative binding

A

When the first oxygen molecule binds to haemoglobin, it causes haemoglobin’s polypeptide chains to reshuffle slightly to make it easier for the other 3 oxygen molecules to bind. Similarly, when oxygen leaves the haemoglobin, the polypeptide chains reshuffle again making it harder for any more oxygens to bind.

153
Q

How long is the arterial blood in contact with the alveoli and how long does it take dot haemoglobin to saturate?

A

Arterial blood is usually in contact with the alveoli for around 0.75 seconds but haemoglobin is fully saturated after 0.25 seconds of contact.

154
Q

Name three causes of anaemia

A
  1. iron deficiency
  2. Haemorrhage
  3. Vitamin B12 deficiency
155
Q

Does the partial pressure of oxygen change in the blood of an anaemic patient? Explain why

A

The partial pressure only accounts for the oxygen that is in solution (not the oxygen attached to haemoglobin).
Anaemia is caused by the reduced carrying capacity of haemoglobin therefore overall, an anaemic patient will have less oxygen in their blood but their partial pressure will be unchanged

156
Q

What is meant by the “partial pressure of oxygen”?

A

REMEMBER THAT THE PARTIAL PRESSURE OF OXYGEN IS THE AMOUNT OF OXYGEN IN SOLUTION (THE OXYGEN BOUND TO HAEMOGLOBIN DOES NOT COUNT!)

157
Q

What happens to the affinity of haem groups for oxygen when PO2 falls below 60mmHg?

A

The affinity of the haem groups for oxygen begins to decrease.

158
Q

How much oxygen does haemoglobin give up to resting tissue to meet the resting energy demand?

A

25% (1 oxygen molecule out of the 4 it is carrying)

159
Q

name 4 factors that cab affect the affinity of oxygen for haemoglobin and therefore disrupt the oxygen/haemoglobin dissociation curve

A
  1. PH
  2. Partial pressure of CO2
  3. temperature
  4. Diphosphoglycerate
160
Q

What impact does alkalosis have on the oxygen-haemoglobin dissociation curve?

A

shifts curve to the left (affinity of haemoglobin for oxygen is decreased)

161
Q

What impact does acidosis have on the oxygen-haemoglobin dissociation curve?

A

Shifts curve to the right (affinity of haemoglobin for oxygen is increased)

162
Q

What impact does hypocapnia have on the oxygen-haemoglobin dissociation curve?

A

Shifts curve to the left (affinity of haemoglobin for oxygen is decreased)

163
Q

What impact does hypercapnia have on the oxygen-haemoglobin dissociation curve?

A

shifts curve to the right (affinity of haemoglobin for oxygen is increased)

164
Q

What impact does hypothermia have on the oxygen-haemoglobin dissociation curve?

A

Shifts curve to the left (affinity of haemoglobin for oxygen is decreased)

165
Q

What impact does hyperthermia have on the oxygen-haemoglobin dissociation curve?

A

Shifts curve to the right (affinity of haemoglobin for oxygen is increased)

166
Q

What impact does low diphosphoglycerate have on the oxygen-haemoglobin dissociation curve?

A

shift the curve to the left (affinity of haemoglobin for oxygen is decreased)

167
Q

What impact does high diphosphoglycerate have on the oxygen-haemoglobin dissociation curve?

A

shift the curve to the right (affinity of haemoglobin for oxygen is increased)

168
Q

What is the Bohr effect?

A

the shifting of the oxygen-haemoglobin dissociation curve to the right. It aides oxygen unloading at the peripheral tissues by reducing the affinity of haemoglobin for oxygen.

169
Q

Explain why carbon monoxide is so dangerous

A

binds to haemoglobin to form carboxyhaemoglobin with an affinity 250 times greater than O2 - binds readily and dissociates very slowly so very problematic once dissolved in circulation.

170
Q

List the clinical signs of carbon monoxide poisoning

A

hypoxia, anaemia, nausea, headache, cherry red skin and mucous membranes

171
Q

What would be the expected respiratory rate in carbon monoxide poisoning?

A

Respiratory rate is unaffected in carbon monoxide because of the normal PCO2

172
Q

How is CO poisoning treated?

A

100% oxygen to increase PaO2

173
Q

What happens when CO2 molecules diffuse from the tissues into the blood?

A

7% remains dissolved in plasma and erythrocytes

23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds

70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions.

174
Q

What happens to the bicarbonate ions formed by CO2 after it is released from tissues into the blood?

A

Bicarbonate moves out of the erythrocytes into the plasma in exchange for Cl- ions & the excess H+ ions bind to deoxyhemoglobin

175
Q

Name the enzyme that converts carbon dioxide to carbonic acid and bicarbonate ions and back again. Where is this enzyme found.

A

carbonic anhydrase (found in red blood cells)

176
Q

Explain why arterial partial pressure of O2 (PaO2 ) is not the same as arterial O2 concentration/content

A

PaO2 refers purely to O2 in solution

Arterial O2 content includes O2 in solution AND O2 bound to haemoglobin

177
Q

Why must gases travel in solution or bound to haemoglobin?

A

they cannot travel as a gas because this would cause an air embolism and death

178
Q

Name the three different types of haemoglobin

A
  1. HbA2 (δ chains replace β)
  2. HbF= foetal haemoglobin (γ chains replace β)
  3. Glycosylated Hb (HbA1a, HbA1b, HbA1c)
179
Q

Which type of haemoglobin makes up 92% of the haemoglobin in our bodies?

A

HBA

180
Q

What causes glycosylated haemoglobin?

A

Haemoglobin becomes glycosylated when it is exposed to high levels of glucose

181
Q

what can glycosylated haemoglobin be used to measure?

A

Control of blood sugar in diabetic patients over a 3 month period

High levels of glycosylated haemoglobin= poor control of blood sugars and multiple hyperglycemic attacks.

182
Q

Why do HBF (foetal haemoglobin) and myoglobin have a higher affinity for haemoglobin than HBA?

A

to extract O2 from maternal/arterial blood.

183
Q

What is myoglobin and where can it be found?

A

Myoglobin is another oxygen carrier & oxygen storage molecule, found exclusively in cardiac and skeletal muscle.

184
Q

What is myoglobin in the blood indicative of?

A

Tissue damage (myoglobin should not be found in the blood!)

185
Q

How does myoglobin’s affinity for oxygen compare to HBA’s?

A

Myoglobin has a much higher affinity for oxygen than haemoglobin

186
Q

List the 5 different types of hypoxia

A
  1. Hypoxaemic hypoxia
  2. Anaemic hypoxia
  3. Stagnant hypoxia
  4. Histotoxic hypoxia
  5. Metabolic hypoxia
187
Q

What is the most common type of hypoxia

A

Hypoxaemic hypoxia

188
Q

What is hypoxaemic hypoxia?

A

Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology.

189
Q

What is anaemic hypoxia?

A

Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency).

190
Q

What is stagnant hypoxia?

A

Heart disease results in inefficient pumping of blood to lungs/around the body

191
Q

What is histotoxic hypoxia?

A

poisoning prevents cells utilising oxygen delivered to them e.g. carbon monoxide/cyanide

192
Q

What is metabolic hypoxia?

A

oxygen delivery to the tissues does not meet increased oxygen demand by cells.

193
Q

What are the skeletal muscles involved in ventilatory control innervated by?

A

Somatic motor neurone (we have control over them!)

194
Q

Explain what drives the skeletal muscles of respiration when we are not consciously thinking about it

A

Centres in the brainstem control the phrenic (to diaphragm) and intercostal nerves (to external intercostal muscles) which stimulate the skeletal muscles to facilitate inspiration.

195
Q

which part of respiration is passive at rest (and therefore requires no neural input)

A

Expiration

196
Q

Where are the areas of ventilation control in the brain/

A

Brainstem (pons and medulla)

197
Q

Severing the spinal cord at what level would cause cessation of breathing and why?

A

C3 (because this is the origin of the phrenic nerve)

198
Q

Name 4 factors that can influence the neural control of respiration

A

Chemoreceptor input
Emotional impulses from the limbic system
Voluntary control from higher brain centres
Mechanosensory receptor input

199
Q

Name the two different types of chemoreceptor involved in respiration

A
  1. Central chemoreceptors

2. peripheral chemoreceptors

200
Q

Where are central chemoreceptors and what do they respond to?

A

Location: Medulla

Respond to: H+ in the CSF around the brain (which originate from PCO2)

201
Q

Which chemoreceptors are responsible for primary ventilatory drive

A

Central Chemoreceptors

202
Q

Where are peripheral chemoreceptors and what do they respond to?

A

Location: Carotid and Aortic bodies

Respond to: PO2

203
Q

What happens to respiration when central chemoreceptors detect a rise in H+ (raised PCO2)

A

Ventilation is stimulated

204
Q

What causes the central chemoreceptors to inhibit ventilation?

A

a decrease in arterial PCO2

205
Q

explain why individuals with chronic lung disease can become reliant on peripheral chemoreceptors instead of central chemoreceptors

A

central chemoreceptors of these individuals become desensitised to PCO2 and the individual instead begins to rely on changes in PaO2 to stimulate ventilation (detected by the peripheral chemoreceptors). This is called “Hypoxic Drive”

206
Q

WhatmmHg must PO2 drop below before peripheral chemoreceptors are stimulated?

A

60mmHg

207
Q

Why doesnt the respiration rate of anaemic patients increase?

A

If the lungs are working normally, diffusion will take place normally and therefore the amount of oxygen in solution in the plasma (PaO2) will be normal.

As PaO2 is what the peripheral receptors monitor there will be no increase in RR.

208
Q

Explain the effects of barbiturate and opioid analgesics on respiration

A

Barbituates and opioids depress the respiratory centres by decreasing their sensitivity to pH (which is controlled primarily by the CO2/bicarbonate buffer system)

209
Q

Explain the effects of nitrous oxide (an analgesic) on peripheral chemoreceptors. When would these effects be problematic/

A

blunts the peripheral chemoreceptor response to falling PaO2.

Not problematic in most people because peripheral chemoreceptors are responsible for secondary ventilatory drive. In those with a chronic lung disease running off hypoxic drive. in these individuals, central chemoreceptors are desensitised and peripheral chemoreceptors are therefore responsible for primary ventilatory drive. Giving these patients NO will leave them with no control over their respiratory drive

210
Q

What is the main factor which determines ventilation?

A

The chemical composition of plasma (controlled mainly by PCO2)

211
Q

Which two systems are responsible for the acid/base balance in blood?

A

The renal and respiratory system

212
Q

What is normal blood pH?

A

7.4

213
Q

Can H+ ions cross the blood brain barrier?

A

NO

214
Q

What happens to ventilation in acidosis (reduced blood pH?)

A

Ventilation increases

215
Q

What happens to ventilation in alkalosis (increased blood pH?)

A

Ventilation decreases

216
Q

What happens to H+ levels in hypoventilation? (remember hypoventilation is NOT breathing slowly!!)

A

Hypoventilation, causing CO2 retention, leads to increased [H+] bringing about respiratory acidosis.

217
Q

What happens to H+ in hyperventilation? (remember hyperventilation is NOT ‘breathing fast”)

A

Hyperventilation, blowing off more CO2, lead to decreased [H+] bringing about respiratory alkalosis

218
Q

How does exercising affect the acid base balance of blood?

A

The release of lactic acid from exercising muscle into blood causes metabolic acidosis

219
Q

Explain why hyperventilation can occur during exercise

A

During very strenuous exercise, ventilation increases more than metabolism. Arterial [H+] increases because of increased lactic acid production. This accounts for some of the hyperventilation seen in this situation.

220
Q

Explain what happens to PO2 and PCO2 when you hold your breath and the affect this has on the body

A

Prolonged breath holding results in decreased PO2 and increased PCO2. This eventually causes a loss of consciousness at which point the individual loses voluntary control over breathing and the body initiates breathing.

221
Q

Explain how the respiratory system facilitates safe swallowing

A

Respiration is inhibited during swallowing to avoid aspiration of food or fluids into the airways. Swallowing is followed by an expiration in order that any particles are dislodged outwards from the region of the glottis.

222
Q

What are the 4 main functions of the respiratory system?

A
  1. Gas exchange
  2. Acid base balance
  3. Protection from infection
  4. Communication & speech
223
Q

What is external respiration?

A

breathing & gas exchange

224
Q

What is internal respiration?

A

Cellular respiration

225
Q

List the three points of gas exchange in the body

A
  1. Gas exchange between the atmosphere and the lung
  2. Gas exchange between the lung and the blood
  3. Gas exchange between the blood and the cells
226
Q

What is the difference between the systemic and the pulmonary circulatory system?

A

Systemic circulation = the system that goes all around the body. The systemic circulatory system delivers O2 to the peripheral tissues and collects CO2

The pulmonary circulation= the specialised circulatory system that only travels between the heart and the lungs

227
Q

Which pulmonary vessels carry A) Oxygenated blood & B) Deoxygenated blood

A

A) pulmonary vein carries oxygenated blood.

B) pulmonary artery carries deoxygenated blood

228
Q

What are the anatomic definitions of an artery and a vein?

A

Artery = “a vessel carrying blood away from the heart”

vein = “a vessel carrying blood towards the heart”.

229
Q

In the steady state, what is the net volume of eO2 and CO2 exchanged in the lungs per unit time

A

250ml/min O2

200ml/min CO2

230
Q

Why is it more comfortable to breathe through the nose than through the mouth?

A

the nose is better at warming and moistening air due to its larger surface to volume ratio.

231
Q

Why must air be fully saturated with water before it reaches the deepest part of the lung?

A

If air is not in solution, it cannot diffuse

232
Q

What is the pharynx?

A

the throat

233
Q

Where is the epiglottis located?

A

Between the pharynx and the larynx

234
Q

Where does the trachea begin?

A

After the larynx

235
Q

Where does the trachea divide?

A

Sternal angle (T4)

236
Q

How many secondary bronchi are there on the left and on the right?

A 
L= 2 (to supply the 2 lobes)
R= 3 (to supply the 3 lobes)
237
Q

What structures make up the upper respiratory tract?

A

The larynx and everything above

238
Q

What structures make up the lower respiratory tract?

A

The trachea and everything below

239
Q

How much air is in the dead space?

A

150ml

240
Q

Name the lobes of the right lung

A

superior, middle and inferior lobes

241
Q

What fissures split the right lung?

A

Horizontal and oblique

242
Q

What fissure splits the left lung?

A

Oblique

243
Q

Name the lobes of the left lung

A

Superior and inferior

244
Q

Why has the left lung got 2 lobes while the right lung has 3 lobes?

A

The left lung is smaller because more space on this side is occupied by the heart

245
Q

What supplies each segment of lung?

A

A tertiary bronchus

246
Q

There is no cartilage in the tertiary bronchi. What keeps it patent?

A

Physical forces acting within the thorax

247
Q

At what point to bronchi become bronchioles?

A

At the point where the cartilage is lost

248
Q

In which primary bronchus are aspirated foreign objects more likely to become lodged and why?

A

The right- it is wider and straighter

249
Q

is airflow resistance greater in the smaller airways or in the larger airways? Why?

A

It is greater in the larger airways because there are more air molecules within one tube

250
Q

What impact does airway contraction have on airflow?

A

Increases it

251
Q

How is the respiratory system able to alter airflow resistance?

A

Through the action of smooth muscle wrapped around bronchioles

252
Q

What is the most significant determinant of airflow resistance?

A

The diameter of the airways

253
Q

What does airway resistance determine?

A

How much air flows into the lungs at any given pressure difference between atmosphere and alveoli.

254
Q

What surrounds an alveoli?

A

Elastic fibres and a capillary network

255
Q

What is the function of the elastic fibres surrounding alveoli?

A

They facilitate the expansion of alveoli during inspiration

256
Q

Name the two different cells making up an alveoli

A

Type 1 and type 2 pneumocystis

257
Q

What is the function of type 1 pneumocytes?

A

Make up the alveoli and facilitate gas exchange

258
Q

What is the function of type 2 pneumocytes?

A

produce surfactant

259
Q

What is the third cell type you will find in an alveoli?

A

Aveolar macrophages

260
Q

Is the surface area of an alveoli large or small?

A

Large!

Respiratory Medicine (27 decks)

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