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ESA 3 - Respiratory System > Control of Breathing and Respiratory Faliure > Flashcards

Control of Breathing and Respiratory Faliure Flashcards

1
Q

What is meant by hypoxia?

A

A fall in alveolar, thus arterial pO2

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2
Q

What is meant by hypercapnia?

A

A rise in alveolar, thus arterial CO2

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3
Q

What is meant by hypocapnia?

A

A fall in alveolar, thus arterial CO2

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4
Q

What is meant by hyperventilation?

A

Ventilation increases with no change in metabolism

Breathing more than you actually have to

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5
Q

What is meant by hypoventilation?

A

Ventilation decreases with no change in metabolism

Breathing less than you have too

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6
Q

What affect does pCO2 have on the plasma?

A

It affects the pH

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7
Q

What affect does hyperventilation have on the plasma?

A

It decreases pCO2 and therefore increases pH

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8
Q

What affect does hypoventilation have on the plasma?

A

It increases pCO2 therefore decreases pH

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9
Q

What are the effects of hypoventilation?

A
  • Hypercapnia
  • Respiratory acidosis
  • pH falls below 7.0
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10
Q

What is the result of the pH change in hypoventilation?

A

Enzymes become lethally denatured

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11
Q

What are the effects of hyperventilation?

A
  • Hypocapnia
  • Respiratory alkalosis
  • pH rises above 7.6
  • Free calcium concentration falls
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12
Q

What is the result of the free calcium fall in hyperventilation?

A

Can fall enough to produce fetal tetany

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13
Q

Why does hyperventilation cause a fall in free calcium?

A

Ca2+ is only soluble in acid, so when pH rises, Ca2+ cannot stay in the blood

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14
Q

Why does a fall in free calcium cause tetany?

A

Nerves become hyper-excitable

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15
Q

What happens in respiratory acidosis?

A

CO2 in produced more rapidly than it is removed by the lungs. Alveolar pCO2 rises, so the concentration of dissolved CO2 rises to more than the concentration of HCO3-, producing a fall in plasma pH

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16
Q

What happens in compensated respiratory acidosis?

A

Respiratory acidosis persists, and the kidneys respond to low pH by reducing the excretion of HCO3-, thus restoring the ratio of concentration of dissolved CO2 to concentration of HCO3-, and therefore the pH

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17
Q

What happens in respiratory alkalosis?

A

CO2 is removed from alveoli more rapidly than produced. Alveolar pCO2 falls, disturbing the ratio of concentration of dissolved CO2 to concentration HCO3-, producing a rise in plasma pH

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18
Q

What happens in compensated respiratory alkalosis?

A

Respiratory alkalosis persists, and the kidneys respond to the high pH by excreting HCO3-, thus restoring the ratio of concentration of dissolved CO2 to concentration of HCO3-, and therefore the pH

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19
Q

What happens in metabolic acidosis?

A

Metabolic production of acid displaces HCO3- as the plasma is buffered, therefore the pH of the blood falls

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20
Q

What happens in compensated metabolic acidosis?

A

The ratio of [dissolved CO2] to [HCO3-] may be restored to near normal by lowering pCO2. The lungs increase ventilation to correct pH

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21
Q

What happens in metabolic alkalosis?

A

Plasma [HCO3-] rises, causing the pH of blood to rise

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22
Q

Give an example of when metabolic alkalosis may occur

A

After vomiting

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23
Q

What happens in compensated metabolic alkalosis?

A

The ratio of [dissolved CO2] to [HCO3-] may be restored to near normal by raising pCO2. The lungs decrease ventilation to correct pH

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24
Q

What detects a falling arterial pO2?

A

Peripheral chemoreceptors located in the carotid and aortic bodies

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25
Q

What are the carotid and aortic bodies stimulated by?

A

A decrease in oxygen supply relative to their own oxygen usage

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26
Q

What is the oxygen usage of the carotid and aortic bodies?

A

Small

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27
Q

What size drops in oxygen do the carotid and aortic bodies respond to?

A

Only large ones

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28
Q

What is the result of stimulation of the receptors located in the carotid and aortic bodies?

A
  • Increases the tidal volume and rate of respiration
  • Changes in circulation directing more blood to the brain and kidneys
  • Increased pumping of blood by the heart
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29
Q

Other than changes in pO2, what to the peripheral chemoreceptors in the carotid and aortic bodies detect?

A

Changes in pCO2

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30
Q

What is the limitation of the detection of changes in pCO2 by the carotid and aortic bodies?

A

They are insensitive

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31
Q

What are more sensitive to changes in pCO2?

A

Central chemoreceptors in the medulla of the brain

32
Q

What do central chemoreceptors in the medulla of the brain do?

A

Alter breathing on a second to second basis

33
Q

What do central chemoreceptors detect?

A

Changes in arterial pCO2

34
Q

How do central chemoreceptors respond to a small rise in pCO2?

A

They cause an increase in ventilation

35
Q

How do central chemoreceptors respond to small falls in pCO2?

A

They cause a decrease in ventilation

36
Q

What are central chemoreceptors the basis of?

A

Negative feedback control of breathing

37
Q

How does negative feedback control of breathing work?

A
  • If pCO2 rises, central chemoreceptors stimulate ventilation
  • This blows of CO2, returning pCO2 to normal
  • Vice-versa

​

38
Q

What do central chemoreceptors actually respond to?

A

Changes in pH of cerebro-spinal fluid

39
Q

How is the CSF separated from the body?

A

By the blood-brain barrier

40
Q

What is the pCO2 of the CSF determined by?

A

The arterial pCO2

41
Q

What substances found in plasma cannot cross the blood-brain barrier?

A
  • HCO3-
  • H+
42
Q

What controls the concentration of [HCO3-] in the CSF?

A

Choroid plexus cells

43
Q

What is the pH of CSF determined by?

A

The ratio of [HCO3-] to pCO2

44
Q

What is the short term result of [HCO3-] being fixed in the CSF?

A

Falls in pCO2 cause an increase in pH, and vice versa

45
Q

How are persisting changes in pH in the CSF dealt with?

A

They are compensated for via the choroid plexus cells altering CSF [HCO3-]

46
Q

What is classified as respiratory failure?

A

When arterial pO2 falls below 8kPa when breathing air at sea level

47
Q

What are the types of respiratory failure?

A
  • Type 1
  • Type 2
48
Q

What is type 1 respiratory failure?

A

Arterial hypoxia, accompanied by normal or low pCO2

49
Q

What are the symptoms of type 1 respiratory failure?

A
  • Breathlessness
  • Exercise intolerance
  • Central cyanosis
50
Q

What is type 2 respiratory failure?

A

Arterial hypoxia, accompanied by an elevated pCO2

51
Q

How many factors are necessary to maintain arterial pO2 in the normal range?

A

5

52
Q

What factors could result in hypoxia?

A
  • Low pO2 in inpsired air
  • Hypoventilation
  • Diffusion impairment
  • Ventilation-perfusion mismatch
  • Abnormal right to left cardiac shunts
53
Q

What is happening when there is low pO2 in inspired air causing hypoxia?

A

Everything is normal, the air breathed in just has low pO2

54
Q

Who is susceptible to hypoxia from low pO2 in inspired air?

A

People living at high altitudes

55
Q

What type of respiratory failure is hypoventilation always associated with?

A

Type 2

56
Q

Why is hypoventilation always associated with type 2 respiratory failure?

A

Because it is always associated with increased pCO2

57
Q

What kinds of problems can cause hypoventilation?

A
  • Neuromuscular problems
  • Chest wall problems
  • Hard to ventilate lungs
58
Q

What neuromuscular problems can cause hypoventilation?

A
  • Respiratory depression due to opiate overdose
  • Head injury
  • Muscle weakness
59
Q

What can cause muscle weaknesses?

A
  • Neuromuscular junction diseases
  • Nerve diseases
  • Muscle diseases
60
Q

What chest wall problems can cause hypoventilation?

A
  • Scoliosis
  • Kyphosis
  • Morbid obesity
  • Trauma
  • Pneumothorax
61
Q

What can cause lungs to be hard to ventilate?

A
  • Airway obstruction
  • COPD and asthma, when the airway narrowing is severe and widespread
  • Severe fibrosis
62
Q

Is oxygen or carbon dioxide affected first in diffusion impairment?

A

Oxygen

63
Q

Why is oxygen affected first in diffusion impairment?

A

Because O2 diffuses much less readily than CO2

64
Q

What is the result of O2 being affected first in diffusion impairment?

A

CO2 is low or normal, and therefore it is always type 1 respiratory failure

65
Q

What can cause diffusion impairment?

A
  • Structural changes
  • Increased path length
  • Total area for diffusion reduced
66
Q

What structural changes can cause diffusin impairment?

A

Lung fibrosis causing thickening of alveolar capillary membrane

67
Q

What can cause increased path length leading to diffusion pathway?

A

Pulmonary oedema

68
Q

What can cause a decrease in the total area for diffusion leading to diffusion impairment?

A

Emphysema

69
Q

Is O2 or CO2 affected first in ventilation-perfusion mismatch?

A

O2

70
Q

What is the result of O2 always being affected first in a ventilation-perfusion mismatch?

A

pCO2 is always low/normal, therefore it is always type 1 respiratory failure

71
Q

What can cause a ventilation-perfusion mismatch?

A
  • Reduced ventilation of some alveoli
  • Reduced perfusion of some alveoli
72
Q

What can cause reduced ventilation of some alveoli?

A

Lobar pneumonia

73
Q

What can cause reduced perfusion of some alveoli?

A

Pulmonary embolism

74
Q

Give an example of an abnormal right-to-left cardiac shunt

A

Cyanotic heart disease, such as Tetralogy of Fallot

75
Q

What happens to the respiratory rate in type 1 respiratory failure?

A

It increases

76
Q

What happens to respiratory rate in type 2 respiratory failure?

A

It increases

ESA 3 - Respiratory System (14 decks)

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