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Respiratory > Respiratory physiology > Flashcards

Respiratory physiology Flashcards

1
Q

What are the 2 classes of respiration?

A

Internal respiration
External respiration

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2
Q

What is meant by internal respiration?

A

This refers to the mechanisms of O2 consumption and CO2 production by cells

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3
Q

What is meant by external respiration?

A

This refers to the sequence of events that allow O2 into the body and CO2 into the environment

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4
Q

What are the 4 stages of external respiration?

A

Ventilation
Exchange of O2 and CO2 in the alveoli
Transport of O2 and CO2 in the blood
Exchange of O2 and CO2 at the tissue

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5
Q

What is ventilation?

A

This the mechanical process of moving air between the atmosphere and the alveolar sacs

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6
Q

What forces keep the alveoli open?

A

Transmural pressure gradient
Pulmonary surfactant
Alveolar interdependance

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7
Q

What forces promote alveolar collapse?

A

Elastic recoil of the lungs and chest wall
Alveolar surface tension

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8
Q

What is the transmural pressure gradient?

A

This is the difference in pressure between the low intrapleural pressure and the higher intrapulmonary pressure

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9
Q

Why does expansion of the chest wall cause expansion of the lungs?

A

Because the surface tension of the pleural fluid resists the pulling apart of the pleura and lungs

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10
Q

How do you convert from kPa to mmHg?

A

mmHg = 7.5 x kPa

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11
Q

What is meant by alveolar interdependence?

A

If an alveolus begins to collapse, it stretches the surrounding alveoli, which recoil and prevent it from collapsing

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12
Q

How do the lungs overcome surface tension in the alveoli?

A

Type II pneumocystis release surfactant, which lowers the surface tension and allows for the easier pulling apart of the alveolar walls

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13
Q

What is LaPlace’s law?

A

The smaller the alveoli, the greater the tendency to collapse

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14
Q

What is work of breathing?

A

This is a reflection of the energy needed to overcome the forces preventing inspiration

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15
Q

What are some factors that may increase the work of breathing?

A

Decreased pulmonary compliance
Decreased airway resistance
Decreased elastic recoil
Need for increased ventilation

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16
Q

What is meant by anatomical dead space?

A

This is space that moves into the lungs but stays trapped in the bronchioles, as the alveoli are full

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17
Q

What is meant by pulmonary ventilation?

A

This is the rate of air movement into the lungs

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18
Q

What is meant by alveolar ventilation?

A

This is the rate of air movement between the atmosphere and the alveoli

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19
Q

What is the formula for pulmonary ventilation (PV)?

A

PV = Tidal volume x respiratory rate

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20
Q

What is the formula for alveolar ventilation (AV)?

A

AV = (Tidal volume - dead space) x resp rate

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21
Q

What is alveolar dead space?

A

This occurs when there is air in the alveoli, but there is not enough blood flowing to it to remove oxygen

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22
Q

What is physiological dead space?

A

This is anatomical dead space + Alveolar dead space

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23
Q

What is Boyle’s law?

A

“At any constant temperature, the pressure exerted by a gas varies inversely with the volume of a gas”

This is means that small volumes have high pressure and large volumes have low pressures

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24
Q

How does Boyle’s law fit into inspiration?

A

In order to allow air into the alveoli, pressure needs to be decreased below that of the atmosphere
Boyle’s law means that to do this, the alveoli must expand to decrease pressure

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25
Q

What causes inspiration?

A

The diaphragm contracts due to stimulation of the phrenic nerve and the external intercostal muscles contract

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26
Q

What are some accessory muscles used in active inspiration?

A

Sternocleidomastoid
Scalenus (Anterior, middle, posterior)
Deltoid
Pectoralis muscles

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27
Q

How does expiration occur?

A

Relaxation of the diaphragm and intercostal muscles allows the elastic recoil of the lungs to decrease volume and thus increase pressure by Boyle’s law, forcing air out

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28
Q

What is tidal volume?

A

Normal change in lung volume during resting ventilation ~0.5L

Think of the tide coming in and out normally

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29
Q

What is inspiratory reserve volume?

A

This is the difference between maximum lung volume and usual maximum inspiration during resting breathing ~3L

Think this is the reserve air that you can breath in after a normal breath in

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30
Q

What is expiratory reserve volume?

A

This is the difference between the minimum lung volume and usual minimum expiration during resting breathing ~1L

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31
Q

What is vital capacity?

A

This is the difference between maximum and minimum lung volumes ~4.5L

Think vitality, yoga, take a deep breath out then in

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32
Q

What is meant by residual capacity?

A

This is the air left in the lungs after maximum expiration ~1.2L

Think residue, stuff left over

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33
Q

What is meant by inspiratory capacity?

A

This is the maximum amount of air that can be breathed in after normal expiration ~3.5L

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34
Q

What is meant by total lung capacity?

A

The total amount of air the lungs can hold ~5L

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35
Q

What is FVC?

A

Forced vital capacity - Maximum volume of air that can be forcibly expelled from the lungs after a maximum inspiration

36
Q

What is FEV1?

A

Forced expiratory volume in 1 second - Maximum volume of air that can be forcibly expelled from the lungs in 1 second after a maximum inspiration

37
Q

What is FER?

A

Forced expiratory ratio - FEV1 ÷ FVC

38
Q

What is a normal value of FER?

A

> 75%

39
Q

Compare the spirometry result of asthma and COPD

A
40
Q

Compare the spirometry result of restrictive disease and obstructive disease

A
41
Q

What is airway resistance?

A

This is the ease at which air can leave the lungs

42
Q

What is the calculation for flow?

A

Flow = ∆Pressure ÷ Resistance

43
Q

What is the main source of resistance in the lungs?

A

The radius of the airways

44
Q

What causes bronchoconstriction of the airways?

A

Parasympathetic stimulation of M3 Ach receptors

45
Q

What causes bronchodilation of the airways?

A

Sympathetic stimulation of ß2 adrenoceptors

46
Q

What is meant by dynamic airway compression?

A

During expiration, pressure in the thoracic cavity increases, therefore compressing the airways

47
Q

What usually resists airway closure by dynamic airway compression?

A

Elastic recoil of the lungs build up pressure in the airways, which keeps the airways open

48
Q

What are some conditions in which dynamic airway compression causes closure of the airways?

A

Emphysema in COPD

49
Q

What is meant by pulmonary compliance?

A

This is a measure of effort that goes into stretching the lungs

It is the change in lung volume per unit change in transmural pressure across the lung wall

50
Q

What are some conditions that can decrease pulmonary compliance (Make it harder to stretch)?

A

Pulmonary fibrosis
Pulmonary oedema
Lung collapse
Pneumonia
Surfactant absence

51
Q

What condition can increase pulmonary compliance?

A

Emphysema

52
Q

What are the consequences of increased pulmonary compliance?

A

This means that the patient has to work harder to deflate and empty the lungs, casing hyperinflation of the lungs

53
Q

What is ventilation rate?

A

The rate at which gases pass through the lungs

54
Q

What is perfusion rate?

A

The rate at which blood passes through the lungs

55
Q

What receptors control ventilation and perfusion?

A

Chemoreceptors, mostly through CO2 (O2 in hypoxic drive)

56
Q

What are some symptoms of severe hypoxia?

A

Altered mental state
Cyanosis
Dyspnoea
Tachypnoea
Arrhythmia

57
Q

What will occur at a pO2 below 5.3 kPa?

A

Hyperventilation

58
Q

What will occur at a pO2 of ~4.3 kPa?

A

Loss of consciousness

59
Q

What will occur at a pO2 of ~2.7 kPa?

A

Death

60
Q

What is hypoxia?

A

A lack of oxygen to the tissues

61
Q

What is hypoxaemia?

A

A lack of oxygen in the blood

62
Q

What is circulatory hypoxia?

A

This is a lack of oxygen getting to the tissues caused by hypokinesia and akinesia of the heart, preventing the transport of oxygen around the blood

63
Q

What condition will cause global reduction in oxygenation, causing systemic circulatory hypoxia?

A

Heart failure

64
Q

What are some conditions that will lead to local reduction in oxygenation, causing isolated circulatory hypoxia?

A

Obstruction of vessels
Oedema
Compression
Compartment syndrome

65
Q

What are some forms of anaemic hypoxia?

A

Macrolytic anaemia
Iron deficiency anaemia
Sickle cell anaemia

66
Q

What deficiencies can lead to macrolytic anaemia?

A

B12
Folate

67
Q

What is koilonychia?

A

Spooning of the nails due to iron deficiency anaemia

68
Q

What is a common cause of iron deficiency anaemia?

A

Blood loss

69
Q

What are some examples of causes of toxic hypoxia?

A

Carbon monoxide poisoning
Cyanide poisoning
Fava-ism (G6PD deficiency)
Amyl nitrate (Poppers)
Aromatic amines
Nitrates
Chloroquine, quinones, sulphonamides, dapsone

70
Q

How does carbon monoxide poisoning cause toxic hypoxia?

A

Carbon monoxide binds irreversibly to haemoglobin, forming carboxyhemoglobin, which prevents the release of oxygen from haemoglobin

71
Q

What are some signs of carbon monoxide poisoning?

A

As oxygen is trapped within the carboxyhemoglobin, venous blood remains oxygenated, causing cherry red blood and cherry red extremities

72
Q

What is the half life of CO in the blood in room air?

A

4-6 hours

73
Q

What is the half life of CO in the blood at 100% oxygen?

A

80 minutes

74
Q

What is the half life of CO in the blood in a hyperbaric chamber?

A

22 minutes

75
Q

How does cyanide cause toxic hypoxia?

A

Cyanide inhibits ATP, shifting cells from aerobic to anaerobic respiration
This means that cells no longer take up oxygen, and so the blood remains oxygenated

76
Q

What are some signs of cyanide poisoning?

A

Clinically identical to CO poisoning
Cherry red blood and extremities

77
Q

What are the treatment options for cyanide poisoning?

A

Amyl nitrite
Hydroxy-cobalamin (Vitamin B12 derivative)

78
Q

What is the risk of giving amyl nitrite in cyanide poisoning?

A

It can cause dangerously high levels of methaemoglobin

79
Q

What is methaemoglobin?

A

Normal haemoglobin contains Fe2+, however, oxidation can form Fe3+, which forms methaemoglobin

80
Q

Why is methaemoglobin (Met-Hb) dangerous?

A

It cannot bind to O2, and so reduces O2 deliver to tissues

81
Q

What are some causes of methaemoglobin production?

A

Favism (G6PD deficiency)
Amyl nitrate (Poppers)
Chloroquine
Dapsone
Primaquine
Quinones
Sulphonamides
Aromatic amines
Nitrates

82
Q

What is favism?

A

This is a genetic condition leading to G6PD deficiency which causes toxic hypoxia on ingestion of fava beans

83
Q

What is meant by hypoxaemic hypoxia?

A

A lack of oxygen in the blood leading to a lack of oxygen in the tissues

84
Q

What are some causes of hypoxaemic hypoxia?

A

Anaesthetic gases
High altitudes (Climbing, aeroplane)

85
Q

What are some causes of alveolar hypoventilation?

A

Opiates
Laryngeal obstruction
Obesity
Bronchial obstruction
Anaesthesia
Kyphoscoliosis

86
Q

What is meant by type I respiratory failure?

A

Low pO2

87
Q

What is meant by type II respiratory failure?

A

Low pO2
High pCO2

Respiratory (23 decks)

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