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Respiratory phase 1 > Lung physiology > Flashcards

Lung physiology Flashcards

1
Q

What structures contribute to the respiratory pump?

A

Bones, muscles, pleura, peripheral nerves, airways

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2
Q

What structures make up the conducting airways?

A

Nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles.

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3
Q

What is the function of the conducting airways?

A

To filter, warm, humidify and conduct air to the lungs.

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4
Q

True or False: the intercostals are the main muscles of respiration.

A

False - the diaphragm is the main muscle of respiration.

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5
Q

What is respiratory epithelium?

A

Pseudo-stratified, columnar, ciliated, interspersed with goblet cells.

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6
Q

What cell type lines most of the surface of an alveoli?

A

Type 1 pneumocytes.

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7
Q

Where is the resistance greatest in the airway?

A

In the trachea - the trachea is longer (length adds resistance) and there is only one of it (branching decreases resistance).

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8
Q

What equation can be used to demonstrate resistance of an airway?

A

Poiseuille’s law: R = 8ƞl / πr^4.

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9
Q

Briefly describe inspiration…

A

Inspiration is an active process. The external intercostal muscles and diaphragm contract. The volume of the thoracic cavity increases and you get a negative intra-thoracic pressure; air is drawn in.

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10
Q

Briefly describe expiration…

A

Expiration is usually passive. The ribs move down and in, the diaphragm relaxes. The intra-thoracic volume decreases and the pressure increases. Air is forced out.

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11
Q

Which muscles are involved in active expiration?

A

Internal intercostal muscles these muscles contract pulling the ribcage inwards and downwards.
abdominal wall muscles

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12
Q

What is the ‘pump handle’ representing?

A

The movement of the sternum. In inspiration the sternum moves anteriorly and superiorly.

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13
Q

What is the ‘bucket handle’ representing?

A

The movement of the rib cage. In inspiration the rib cage moves upwards and outwards.

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14
Q

What does perfusion (Q) refer to?

A

refers to the flow of blood to alveolar capillaries

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15
Q

What is perfusion of pulmonary capillaries dependent on?

A
  1. Pulmonary artery pressure.
  2. Pulmonary venous pressure.
  3. Alveolar pressure.
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16
Q

What does ventilation (V) refer to?

A

Refers to the flow of air into and out of the alveoli

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17
Q

What is the relevance of ventilation and perfusion?

A

For effective gas exchange to occur, alveoli must be ventilated and perfused

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18
Q

What is V/Q mismatch?

A

When the perfusion of blood in capillaries isn’t matching the ventilation of the alveoli.

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19
Q

What is it called when you have a high V/Q ratio?

A

Dead space. Lots of ventilation but no perfusion.

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20
Q

What is a cause of a high V/Q ratio (dead space)?

A

Pulmonary embolism - when a blood clot blocks a blood vessel within the lungs.

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21
Q

What is it called when you have a low V/Q ratio?

A

Shunt. Lots of perfusion but no ventilation.

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22
Q

What is a cause of a low V/Q ratio (shunt)?

A

Pulmonary oedema - fluid builds up in the lungs, making it difficult to breathe

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23
Q

Does the apex of the lung have a high or a low V/Q? Why?

A

The apex of the lung has a high V/Q (less perfusion) due to gravity

There is more perfusion at the base of the lung.

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24
Q

Nomenclature;
PaCO2
PACO2
PaO2
PAO2
PiO2
FiO2
VA
VCO2

A

PaCO2: arterial CO2
PACO2: alveolar CO2
PaO2: Arterial O2
PAO2: alveolar O2
PiO2: pressure of inspired O2
FiO2: fraction of inspired O2
VA: alveolar ventilation
VCO2: CO2 production

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25
Q

What is normal PCO2 level?

A

4-6KPa

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26
Q

PaCO2 equation?

A

PaCO2 = K VCO2 / VA
Carbon dioxide = K CO2 production / alveolar ventilation

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27
Q

What are the 7 layers for gas exchange?

A
  1. Alveolar epithelium.
  2. Interstitial fluid.
  3. Capillary endothelium.
  4. Plasma layer.
  5. RBC membrane.
  6. RBC cytoplasm.
  7. Hb binding sites.
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28
Q

What is the alveolar gas equation?

A

PAO2 = PiO2 - (PaCO2/R)
Alveolar gas = pressure of inspired O2 - (CO2/R)

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29
Q

What is hypoxia?

A

A state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis

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30
Q

Name 4 causes of hypoxia.

A
  1. Hypoventilation.
  2. V/Q mismatch.
  3. Diffusion abnormality.
  4. Reduced PiO2.
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31
Q

What effect does hypoxia have on pulmonary vessels?

A

It vasoconstricts the vessels and so redirects blood to O2 rich alveoli.

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32
Q

What effect does hypoxia have on systemic vessels?

A

Vasodilation.

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33
Q

What is hypercapnia?

A

When you have too much carbon dioxide (CO2) in your blood.

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34
Q

Name 4 causes of hypercapnia.

A
  1. Increased dead space ventilation; rapid, shallow breathing.
  2. V/Q mismatch.
  3. Increased CO2 production.
  4. Reduced minute ventilation.
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35
Q

What is type 1 respiratory failure?

A

Hypoxia / hypoxyaemia

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36
Q

What is type 2 respiratory failure?

A

Hypoxia and hypercapnia

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37
Q

What if the difference between type 1 and 2 respiratory failure?

A

Type 1 respiratory failure occurs when the respiratory system cannot adequately provide oxygen to the body, leading to hypoxemia.

Type 2 respiratory failure occurs when the respiratory system cannot sufficiently remove carbon dioxide from the body, leading to hypercapnia.

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38
Q

What causes a shift in the oxygen dissociation curve and which way does it shift?

A

Shift right
Increasing temperature
Increasing 2,3 diphosphoglyceric acid
Increasing H+ concentration
Increasing CO2

Shift left
Decreasing temperature
Decreasing 2,3 diphosphoglyceric acid
Decreasing H+ concentration
Decreasing CO2

39
Q

Oxygen dissociation curve: what does it mean when the curve shifts to the right?

A

There is increased O2 unloading. Hb’s affinity for oxygen has decreased.

40
Q

What is Hb affinity for O2?

A

How readily Hb acquires and releases O2 at respiring tissues.

41
Q

What does Boyles law describe?

A

How pressure of a gas increases as volume decreases.

42
Q

What is Boyle’s law?

A

Pressure and Volume are inversely proportional;
P1V1 = P2V2

43
Q

What is Dalton’s law?

A

In a mixture of non reacting gases Ptotal = Pa + Pb.

(P total is the sum of the pressures of individual gases).

44
Q

What is Henry’s law?

A

The solubility of a gas is proportional to the partial pressure of the gas.
S1/P1 = S2/P2.

45
Q

What is Laplace’s law?

A

P = 2T/R.
Pressure = 2(surface tension)/ radius

46
Q

What is the significance of Laplace’s law?

A

It tells us that small alveoli have a greater pressure and so air will move from small alveoli to larger alveoli; uneven aeration. (Surfactant can prevent this).

47
Q

Where is surfactant produced?

A

It is produced by type 2 pneumocytes in the alveoli.

48
Q

When is surfactant produced?

A

It starts being produced from 34 weeks gestation and production increases rapidly 2 weeks before birth.

49
Q

List 4 functions of surfactant.

A
  1. Prevents alveoli collapse.
  2. Allows homogenous aeration.
  3. Reduces surface tension.
  4. Maintains functional residual capacity.
50
Q

Premature babies may have surfactant deficiency. What are the consequences of this?

A
  1. Respiratory distress syndrome.
  2. Non-compliant lungs.
  3. Unequal aeration.
  4. Reduced lung volume.
51
Q

How can you treat surfactant deficiency?

A

Ensure the patient is warm and is receiving O2 and fluids. Begin surfactant replacement.

52
Q

What is the respiratory drive more senstitive to, CO2 or O2?

A

It is very sensitive to CO2 and so CO2 is a greater drive. A small change in PaCO2 results in a large ventilatory change.

53
Q

What is the acid/base dissociation equation?

A

CO2 + H2O = H2CO3 = HCO3- + H+

54
Q

What enzyme catalyses the formation of bicarbonate and hydrogen ions from CO2 and H2O?

A

Carbonic anhydrase.

55
Q

What is the henderson hasselbalch equation?

A

pH = pKa + log (A-)/(HA)

56
Q

Describe the 4 main acid-base disorders…

A

Respiratory acidosis; increased PaCO2, decreased pH, mild increased HCO3-

Respiratory alkalosis; decreased PaCO2, increased pH, mild decreased HCO3-

Metabolic acidosis; reduced bicarbonate and decreased pH

Metabolic alkalosis; increased bicarbonate and increased pH

57
Q

What is a cause of respiratory acidosis?

A

Inadequate ventilation; could be due to obstruction e.g. COPD.

58
Q

What is the renal compensation mechanism for respiratory acidosis?

A

Increased ammonia formation. H+ secretion increases and there is increased HCO3- reabsorption.

59
Q

What can cause respiratory alkalosis?

A

Hyperventilation in response to hypoxia.

60
Q

What is the renal compensation mechanism for respiratory alkalosis?

A

H+ secretion decreases; more H+ is retained. HCO3- secretion.

61
Q

What is a cause of metabolic acidosis?

A

Renal failure; loss of HCO3-, excess H+ production.

62
Q

What is the respiratory compensation mechanism for metabolic acidosis?

A

Chemoreceptors stimulated, enhancing respiration, PaCO2 decreases.

63
Q

What is a cause of metabolic alkalosis?

A

Vomiting; loss of H+.

64
Q

What is the respiratory compensation mechanism for metabolic alkalosis?

A

Chemoreceptors are inhibited, reduced respiration, PaCO2 increases.

65
Q

Why can hypoxia cause respiratory alkalosis?

A

Hypoxia leads to hyperventilation as the person tries to inhale more O2. This means you lose a lot of CO2 resulting in alkalosis.

66
Q

What is forced vital capacity?

A

Volume of air that can be forcibly exhaled after maximum inhalation.

67
Q

How can you work out total lung capacity?

A

Add vital capacity to residual volume.

68
Q

How could you diagnose a patient with having an obstructive lung disease?

A

The FEV1/FVC ratio would be less than 70% predicted value.

69
Q

What is the normal range of FEV1 FVC ratio?

A

Equal to or > 70%

70
Q

How could you diagnose a patient with having an restrictive lung disease?

A

The FEV1/FVC ratio would be normal but their FVC value would be very low.

71
Q

Define FEV1…

A

FEV1: Forced expiratory volume in one second

The volume of air that can be forcibly exhaled in 1 second.

72
Q

Define forced vital capacity (FVC)…

A

The maximum volume of air that can be forcibly exhaled after maximal inhalation. Usually in 6 seconds.

73
Q

Equation for total lung capacity?

A

TLC = VC + RV.
Vital capacity + residual volume

74
Q

Define total lung capacity…

A

The vital capacity plus the residual volume. It is the maximum amount the lungs can hold.

75
Q

Define residual volume (RV)…

A

The volume of air remaining in the lungs after a maximal exhalation.

76
Q

Define functional residual capacity (FRC)…

A

The volume of air remaining in the lungs after a tidal volume exhalation.

77
Q

Define tidal volume (TV)…

A

The volume of air moved in and out of the lungs during a normal breath.

78
Q

Define expiratory reserve volume (ERV)…

A

The additional volume of air that can be forcibly exhaled after a tidal volume expiration.

79
Q

Define inspiratory reserve volume (IRV)…

A

The additional volume of air that can be forcibly inhaled after a tidal volume inspiration.

80
Q

What is lung compliance?

A

A measure of the lung’s ability to stretch and expand. Compliance = ∆V/∆P.

81
Q

What happens to the FEV1 and FVC in an elderly person?

A

They both decrease and the residual volume increases.

82
Q

What changes are seen in an aging lung?

A

Decreased compliance, muscle strength, elastic recoil, immune function. Decreased response to hypoxia and hypercapnia. Impaired gaseous exchange.

83
Q

Why do you see decreased elastic recoil in an ageing lung?

A

The elastin degenerates and ruptures.

84
Q

Why do you see decreased muscle strength in an ageing lung?

A

There is a decrease in type 1, fatigue resistant fibres. And muscle mass also decreases.

85
Q

Why do you see a decreased response to hypoxia and hypercapnia in an ageing lung?

A

The lung is more vulnerable and has a decreased awareness meaning these changes aren’t detected till late on.

86
Q

Why do you see decreased immune function in an ageing lung?

A

There is less protective mucus and sputum clearance is less effective.

87
Q

Why do you see impaired gaseous exchange in an ageing lung?

A

The SA for gaseous exchange decreases and there is increased V/Q mismatch.

88
Q

Why does the residual volume increase in an ageing lung?

A

The chest wall changes shape. There is increased calcification and stiffness.

89
Q

Define vital capacity…

A

The maximum volume of air that can be exhaled after a maximal inhalation.

90
Q

What is the normal tidal volume in an adult?

A

500ml

91
Q

What is the thickness of the air-blood barrier in nm?

A

200-800nm

92
Q

Define peak expiratory flow (PEF)…

A

The greatest rate of airflow that can be obtained during forced exhalation.

93
Q

Define airway obstruction…

A

Impediment to inspiratory and expiratory air flow.

94
Q

Define airway restriction…

A

When the lungs are restricted from full expansion.

Respiratory phase 1 (8 decks)

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