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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
What are the carotid and aortic bodies stimulated by?
A decrease in oxygen supply relative to their own oxygen usage
26
What is the oxygen usage of the carotid and aortic bodies?
Small
27
What size drops in oxygen do the carotid and aortic bodies respond to?
Only large ones
28
What is the result of stimulation of the receptors located in the carotid and aortic bodies?
* 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
29
Other than changes in pO2, what to the peripheral chemoreceptors in the carotid and aortic bodies detect?
Changes in pCO2
30
What is the limitation of the detection of changes in pCO2 by the carotid and aortic bodies?
They are insensitive
31
What are more sensitive to changes in pCO2?
Central chemoreceptors in the medulla of the brain
32
What do central chemoreceptors in the medulla of the brain do?
Alter breathing on a second to second basis
33
What do central chemoreceptors detect?
Changes in arterial pCO2
34
How do central chemoreceptors respond to a small rise in pCO2?
They cause an increase in ventilation
35
How do central chemoreceptors respond to small falls in pCO2?
They cause a decrease in ventilation
36
What are central chemoreceptors the basis of?
Negative feedback control of breathing
37
How does negative feedback control of breathing work?
* If pCO2 rises, central chemoreceptors stimulate ventilation * This blows of CO2, returning pCO2 to normal * *Vice-versa* ## Footnote *​*
38
What do central chemoreceptors actually respond to?
Changes in pH of cerebro-spinal fluid
39
How is the CSF separated from the body?
By the blood-brain barrier
40
What is the pCO2 of the CSF determined by?
The arterial pCO2
41
What substances found in plasma cannot cross the blood-brain barrier?
* HCO3- * H+
42
What controls the concentration of [HCO3-] in the CSF?
Choroid plexus cells
43
What is the pH of CSF determined by?
The ratio of [HCO3-] to pCO2
44
What is the short term result of [HCO3-] being fixed in the CSF?
Falls in pCO2 cause an increase in pH, and vice versa
45
How are persisting changes in pH in the CSF dealt with?
They are compensated for via the choroid plexus cells altering CSF [HCO3-]
46
What is classified as respiratory failure?
When arterial pO2 falls below 8kPa when breathing air at sea level
47
What are the types of respiratory failure?
* Type 1 * Type 2
48
What is type 1 respiratory failure?
Arterial hypoxia, accompanied by normal or low pCO2
49
What are the symptoms of type 1 respiratory failure?
* Breathlessness * Exercise intolerance * Central cyanosis
50
What is type 2 respiratory failure?
Arterial hypoxia, accompanied by an elevated pCO2
51
How many factors are necessary to maintain arterial pO2 in the normal range?
5
52
What factors could result in hypoxia?
* Low pO2 in inpsired air * Hypoventilation * Diffusion impairment * Ventilation-perfusion mismatch * Abnormal right to left cardiac shunts
53
What is happening when there is low pO2 in inspired air causing hypoxia?
Everything is normal, the air breathed in just has low pO2
54
Who is susceptible to hypoxia from low pO2 in inspired air?
People living at high altitudes
55
What type of respiratory failure is hypoventilation always associated with?
Type 2
56
Why is hypoventilation always associated with type 2 respiratory failure?
Because it is always associated with increased pCO2
57
What kinds of problems can cause hypoventilation?
* Neuromuscular problems * Chest wall problems * Hard to ventilate lungs
58
What neuromuscular problems can cause hypoventilation?
* Respiratory depression due to opiate overdose * Head injury * Muscle weakness
59
What can cause muscle weaknesses?
* Neuromuscular junction diseases * Nerve diseases * Muscle diseases
60
What chest wall problems can cause hypoventilation?
* Scoliosis * Kyphosis * Morbid obesity * Trauma * Pneumothorax
61
What can cause lungs to be hard to ventilate?
* Airway obstruction * COPD and asthma, when the airway narrowing is severe and widespread * Severe fibrosis
62
Is oxygen or carbon dioxide affected first in diffusion impairment?
Oxygen
63
Why is oxygen affected first in diffusion impairment?
Because O2 diffuses much less readily than CO2
64
What is the result of O2 being affected first in diffusion impairment?
CO2 is low or normal, and therefore it is **always type 1 respiratory failure**
65
What can cause diffusion impairment?
* Structural changes * Increased path length * Total area for diffusion reduced
66
What structural changes can cause diffusin impairment?
Lung fibrosis causing thickening of alveolar capillary membrane
67
What can cause increased path length leading to diffusion pathway?
Pulmonary oedema
68
What can cause a decrease in the total area for diffusion leading to diffusion impairment?
Emphysema
69
Is O2 or CO2 affected first in ventilation-perfusion mismatch?
O2
70
What is the result of O2 always being affected first in a ventilation-perfusion mismatch?
pCO2 is always low/normal, therefore it is always type 1 respiratory failure
71
What can cause a ventilation-perfusion mismatch?
* Reduced ventilation of some alveoli * Reduced perfusion of some alveoli
72
What can cause reduced ventilation of some alveoli?
Lobar pneumonia
73
What can cause reduced perfusion of some alveoli?
Pulmonary embolism
74
Give an example of an abnormal right-to-left cardiac shunt
Cyanotic heart disease, *such as Tetralogy of Fallot*
75
What happens to the respiratory rate in type 1 respiratory failure?
It increases
76
What happens to respiratory rate in type 2 respiratory failure?
It increases

ESA 3 - Respiratory System (14 decks)

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