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Year 1- Respiratory > 6 Haemoglobin & Gas transport > Flashcards

6 Haemoglobin & Gas transport Flashcards

1
Q

How much Oxygen is dissolved in every litre of plasma?

A

3ml

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2
Q

What is the oxygen carrying capacity of the blood?

A

200 ml/L

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3
Q

What determines the arterial partial pressure of O2?

A

The oxygen dissolved in the blood

NOT the oxygen carried by haemoglobin

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4
Q

What 2 factors influence how much O2 is dissolved?

A
  • Its solubility

- The partial pressure of gaseous oxygen driving the O2 into solution (basically the partial pressure in the alveoli)

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5
Q

What is the patial pressure of the oxygen in solution?

A

100mmHg (sometimes called oxygen tension)

Its equal to the PO2 driving it across.

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6
Q

What is the oxygen demand of resting cells?

A

250ml/min

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7
Q

What is cardiac output?

A

Around 5L/min

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8
Q

How much haemoglobin is in the average person?

A

150g/L

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9
Q

How much oxygen is carried in every gram of haemoglobin?

A

1.34ml of O2 per gram of haemoglobin

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10
Q

How much oxygen is carried in the haemoglobin of a normal person?
[150g haemoglobin/L]
[5L/min cardiac output]
[1.34ml O2/g of haemoglobin]

A

5 litres every minute
-> 5L x 150g = 750g/min

  1. 34ml O2/g
    - > 750 x 1.34 = 1000ml/min
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11
Q

How much of the arterial O2 is extracted by tissue at rest?

A

Only about 25%

Since resting tissues use 250ml/min and haemoglobin carries 1000ml/min

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12
Q

How is the PO2 gradient maintained betweent the blood & alveoli?

A

Haemoglobin takes up arterial oxygen so the gradient doesnt reach equilibrium

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13
Q

What is the most common form of Haemoglobin? Descibe?

A

HbA
Makes up 92% of haemoglobin
Made up of 2 alpha & 2 beta chains

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14
Q

What are some other types of haemoglobin?

A

HbA2
HbF (Foetal)
Glycosylated Hb
myoglobin

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15
Q

What makes up foetal haemoglobin?

A

2 Alpha chains

2 Gamma chains

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16
Q

What makes up HbA2?

A

2 Alpha chains

2 Delta chains

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17
Q

What are the types of glycosylated Hb?

A

HbA1a
HbA1b
HbA1c

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18
Q

Where is myoglobin found?

A

In oxidative muscle fibres

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19
Q

How does a foetus extract O2 from maternal blood?

A

HbF has a much higher affinity for O2 than HbA.

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20
Q

How do muscles extract O2 from the blood?

A

BY having a higher O2 afinity than HbA

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21
Q

How long is haemoglobin in contact with the alveoli?

A

ARound 0.75 seconds

IT only takes 0.25 to become saturated though.

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22
Q

How far can PAO2 drop before haem saturation goes below 90%?

A

PAO2 can go as low as 60mmHg without losing much arterial oxygen

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23
Q

What factors can affect the affinty of haemoglobin for Oxygen?

A
  • pH
  • PaCO2
  • Temperature
  • [Diphospholycerate]
24
Q

What kind of people produce more diphosphoglycerate?

A

People who live at a high altitude.

Those with heart or lung disease

25
Q

What is the main determinant of haemoglobin saturation?

A

The PaO2

26
Q

See graphs for how saturation is affected by various factors

A

In word document and pp

27
Q

What decreases haemoglobin’s affinity for oxygen?

A

Its decreased by:

  • a pH drop
  • A PaCO2 increase
  • A Temp rise
28
Q

What is the physiological benefit of decreasing haemoglobin’s affinity for oxygen?

A

Low pH, high PaCO2 & high temp exist in actively metabolising tissues and decrease haemoglobins affinity for oxygen.

This facilitates the dissociation of oxygen from haemoglobin.

29
Q

What increases haemoglobin’s affinity for oxygen?

A
  • A pH rise
  • A PCO2 fall
  • Temp fall
30
Q

Whats the effect of increased haemoglobin affinity for oxygen?

A

It makes oxygen unloading more difficult at tissues.

But it makes it easier to collect oxygen in pulmonary circulation.

31
Q

What does 2,3-DPG do?

A

Decerases haemoglobin oxygen affinity

32
Q

What makes 2.3-DPG?

A

Erythrocytes

33
Q

Why is 2,3-DPG made in situations with inadequate oxygen?

A

It helps maintain oxygen release at tissues.

34
Q

Define anaemia?

A

Any condition where O2 carrying capacity of blood is compromised

35
Q

Give some examples of Anaemic conditions?

A
  • Fe deficiency so cant make enough haem
  • Haemorrhage, losing blood
  • Vit B12 deficiency
36
Q

Why is PaO2 normal in anaemia?

A

Therse no problem with ventilation or gas exchange. Therefore no reduction in the amount dissolved in blood

37
Q

How does anaemia affect the saturation of haemoglobin?

A

The RBCs would still be fully saturated its just theres less of them

38
Q

What do CO & haemoglobin form?

A

Carboxyhaemoglobin

39
Q

Describe the affinity of CO for Haemoglobin?

A

CO has a 250 times greater affinity for haemoglobin than O2 thus preventing transport of oxygen

40
Q

What partial pressure of CO causes carboxyhaemoglobin formation?

A

0.4mmHg PaCO is all thats needed to cause progressive carboxyhaemoglobin formation

41
Q

What are the symptoms of CO poisoning?

A
  • Hypoxia & Anaemia
  • Nausea & Headaches
  • Cherry red skin & Mucous membranes
  • Potential brain damage & death
42
Q

What is the main thing that drives ventilation?

A

Getting rid of CO2

43
Q

How many types of hypoxia are there?

A

5

44
Q

Define hypoxia?

A

An inadequate supply of oxygen to tissues

45
Q

What is the most common form of hypoxia? describe?

A

Hypoxic Hypoxia

  • > Tissue pathology or decreased atmospheric PO2
  • > Reduced O2 diffusion at lungs
46
Q

What is the cause of anaemic hypoxia?

A

Anaemia leads to reduced O2 carrying capacity

47
Q

What is the cause of Ischaemic (stagnant) hypoxia?

A

Heart Pathology

-> Inefficient blood pumping

48
Q

How does histotoxic Hypoxia occur?

A 
Tissue Poisoning (e.g. Hydrogen sulphide or cyanide)
-> Cells cant use the oxygen thats delivered to them
49
Q

What causes metabolic hypoxia?

A

Tissue Oxygen demand increases

-> Oxygen delivery to the tissuesdoesnt meet new demands

50
Q

How is CO2 transported in the blood?

A
  • 70%as carbonate in solution
  • 7% in solution alone
  • 23% in RBCs as carbamino compounds (Formed with deoxyhaemoglobin)
51
Q

Whats the equation for how CO2 affects ECF pH?

A

CO2 + H2O ↔ H2CO3 ↔ HCO3 + H+

52
Q

What is carbonate/carbonic acid?

A

Carbonic acid = H2CO3

Carbonate = HCO3

53
Q

Why does plasma pH alter during hypo/hyperventilation?

A

They alter PaCO2, moving the equation and altering [H+]

54
Q

How does hypoventilation affect plasma pH?

A

Hypoventilation

  • > CO2 retention
  • > [H+] increases
  • > Respiratory acidosis
55
Q

How does hyperventilation affect plasma pH?

A

Hyperventilation

  • > Blowin off more CO2 than normal
  • > [H+] decreases
  • > Respiratory Alkalosis

Year 1- Respiratory (30 decks)

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