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Respiratory Module > Lecture 8 - Control Of Ventilation At High Altitude > Flashcards

Lecture 8 - Control Of Ventilation At High Altitude Flashcards

1
Q

What is the biggest factor that affects high altitude?

A

Barometric pressure

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2
Q

What happens to the barometric pressure as altitude increases?

A

Barometric pressure decreases

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3
Q

What would happen if the barometric pressure was at the equator?

A

You would not be able to climb as the barometric pressure would be too low and you would need supplementary oxygen

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4
Q

What does inspired air =

A

Pressure - water vapour x oxygen fraction

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5
Q

What is the alveolar gas equation?

A

PA02 - (inspired PO2) - (PO2/respiratory exchange ratio)

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6
Q

What is the barometric pressure at Everest?

A

It is around 250

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7
Q

What is the barometric pressure at the top of Everest?

A

250

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8
Q

What is the barometric pressure at the top of Everest?

A

Around 250

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9
Q

What is changes in arterial PO2 sensed by?

A

Peripheral chemoreceptors - below 10% is when the are activated

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10
Q

How could you change the partial pressure of CO2?

A

Increasing the ventilation rate

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11
Q

What happens at the top of Everest?

A

Lower inspired PO2, increases ventilation, decreases PCO2 and increases pH

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12
Q

What is the mmHg for water vapour?

A

47mmHg - it is the same everywhere

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13
Q

What is the fraction of O2?

A

21%

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14
Q

What is the level of barometric pressure at sea level?

A

760mmHg

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15
Q

What is PCO2 at rest?

A

40mmHg

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16
Q

What happens when there is an increase in altitude?

A

Acute increases in rate and depth of ventilation, peripheral chemoreceptors are stimulated by low PO2 and PO2 drives respiration due to hypoxia

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17
Q

What does an increase in heat rate due to hypoxaemia increase?

A

Increases O2 delivery to the pheriphery

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18
Q

What level of arterial pressure of O2 does ventilation start to increase? normal O2 is 160mmHg

A

70-60mmHg

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19
Q

Why do you get an increase in pH when CO2 decreases?

A

Because CO2 is important as a buffer for blood and in cerebral spinal fluid

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20
Q

What does an increase in pH cause?

A

Causes changes in Cheyenne stroke ventilation

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21
Q

What does a low PCO2 inactivate?

A

Central chemoreceptors which decrease ventilation, which is not ideal at high altitude. PCO2 rises and initiatives slow deep breaths by O2 demand is not met

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22
Q

What does an increase in pH to the cerebral spinal fluid do when CO2 changes in the blood due to a decrease in PCO2? - hypoxia

A

Causes the central chemoreceptors to stop firing ventilation and causes a reduction in ventilation which is not ideal at high altitude.

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23
Q

What are your breaths like at a high altitude?

A

Big deep breaths width pauses and another deep big breath. As you are constantly trying to fight the increase in pH but also the demand for CO2 at the same time

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24
Q

What happens to the blood brain barrier at high altitude?

A

Charged particles cannot cross,
Changes in spinal fluid pH,
Need to reduce pH in both CSF and blood,
Can take several days to acclimatise

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25
Q

What is acclimatisation?

A

The process to try and Normalise your pH, specifically cerebral spinal fluid pH - because it is the break on ventilation.

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26
Q

If you can get the pH more neutral or an acidic pH what can happen?

A

The central chemoreceptors can start work in again which is done by the choroid plexus

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27
Q

What is the choroid plexus?

A

It sits on the blood brain barrier and actively transports bicarbonate from the spinal fluid into the blood. Bicarbonate neutralises.

28
Q

What organ can help with reducing the pH?

A

The kidney - but it takes a couple of days to process

29
Q

What mode of transport does not allow your body to acclimatise?

A

Planes - if you fly to somewhere with a high altitude like Machu Picchu then you are at risk of acute mountain sickness as your body did not acclimatise

30
Q

What is your arterial PO2 if you have COPD?

A

55mmHg - you would need supplementary oxygen if uou decides to walk up a mountain

31
Q

What is considered to be high altitude?

A

Anything above 2000 metres

32
Q

What do athletes do in regards to High altitude?

A

They train at high for a period of time so when they go back down it is easier. Although they need to train at a low altitude the majority of the time as they need to train at the best of their ability which is with a decent barometric pressure and good oxygen supply

33
Q

What are some short physiological adaptions to an increase in altitude?

A

Increase in Diphosphoglycerate (2,3-DPG)

34
Q

What does 2,3-DPG help with?

A

Helps release oxygen at lower tensions, makes it slightly harder for haemoglobin to take up oxygen from the lungs but this is compensated for an increase in ventilation

35
Q

Increase in 2,3-DPG =

A

Stops the tissues become hypoxic

36
Q

What is an increase in 2,3-DPG an important mechanism for?

A

To match o2 demand to o2 supply

37
Q

What is a longer physiological adaption to altitude?

A

Increase in haematocrit which increases haemopoiesis

38
Q

What is the initial response for an increase in haematocrit?

A

25% decrease in plasma volume, increase in urination, increase in respiratory loss of H20 as increase in ventilation and dry air,
increase in number of capillaries

39
Q

What does an increase in the number of capillaries =

A

Improves diffusion of oxygen

40
Q

What would be a longer term response to an increase in haematocrit?

A

Increase in haemopoiesis, get more red blood cells, decrease in O2 tension in the kidney and the kidney can release erythropoietin

41
Q

What are the normal haematocrit levels at seal level?

A

50% at sea lebel

42
Q

What are the haematocrit levels of people who live in the Andes at 6000 metres?

A

Up to 80%, increase the concentration in a solution then it becomes much more viscous so their blood will be like porridge

43
Q

What does increases the number of capillaries allow?

A

Allows oxygenated blood to become closer to the tissues where it is needed

44
Q

What are formed due to an increase number of capillaries?

A

More mitochondria and cellular respiratory enzymes are formed

45
Q

What are the symptoms for acute mountain sickness?

A

Headache, anorexia, nausea, malaise, lack of energy, disturbed sleep and occasional vomiting

46
Q

What physiologist looked into acute mountain sickness?

A

John west

47
Q

What is the best treatment for acute mountain sickness?

A

Descent of the mountain - going down to a lower altitude

48
Q

What is the best treatment for acute mountain sickness?

A

Descent is the best treatment - going to a lower altitude

49
Q

What is the best treatment for acute mountain sickness?

A

Descent is the best treatment - going to a lower altitude

50
Q

What are some other treatments for acute mountain sickness?

A

Oxygen, acetazolamide, dexamethasone

51
Q

Describe acetazolamide

A

It’s a carbonic anhydrase inhibitor so causes slight acidosis. Stops the equation shifting back the other way so keeps it slightly acidic

52
Q

Describe dexamethasone

A

Effective in that it increases ventilation rate - but if you stop taking it then ventilation rate will decrease straight away

53
Q

What equipment is useful to have if you are climbing a mountain and have symptoms of acute mountain sickness?

A

Gamow bag - inflate and climb inside

54
Q

What are the symptoms for high altitude pulmonary edema?

A

Breathless, more noticeable at night lying down, crackles during auscultation and frothy pink sputum

55
Q

What causes high altitude pulmonary edema?

A

Uneven vasoconstriction

56
Q

What happens during uneven vasoconstriction?

A

Blood pressure increases and heart rate increases - starts to cause ultra structural changes

57
Q

What does an increase in pressure in the small capillaries do?

A

Starts to cause leakage of red blood cells and other components of the blood

58
Q

What ultra structural changes occur? - due to uneven vasoconstriction

A

Happens around the blood gas barrier, diffusion across this barrier is very important and increases a large level of fluid - affects how oxygen and other gases diffuse

59
Q

What is the pink/red frothy sputum due to?

A

Proteins in the blood escaping into the airways

60
Q

What is another ultra structural change due to high altitude pulmonary edema?

A

Breaks in epithelial layers - where proteins and components can escape

61
Q

What are the symptoms of high altitude cerebral edema?

A

Develop with acute mountain sickness, confusion, ataxia (muscle coordination)

62
Q

What is the treatment for high altitude cerebral edema?

A

Descent, increasing barometric pressure - Gamow bag

63
Q

What do the kidneys produce that is useful in adaptions for altitude?

A

Hypoxic inducible factor 1 - only stable under hypoxic conditions, stimulates bone marrow to produce or stop apoptosis and allows red blood cells to mature

64
Q

How can you increase red blood cells without increasing altitude?

A

Blood doping, increasing erythropoietin

65
Q

How long does it take to see changes in red blood cells?

A

3 weeks

66
Q

Who is famous for increasing their erythropoietin?

A

Lance Armstrong - used it illegally for the Tour de France

67
Q

What are the symptoms of chronic mountain sickness?

A

Headache, somnolence (strong desire to fall asleep), depression

Respiratory Module (10 decks)

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