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Respiratory System > Haemoglobin And Gas Transport > Flashcards

Haemoglobin And Gas Transport Flashcards

1
Q

Roughly how much O2 is dissolved per litre plasma?

A

3mL

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2
Q

Describe the difference between arterial partial pressure of O2 and arterial O2 content

A

Arterial O2 partial pressure - the gaseous phase that is driving O2 into solution

Arterial O2 content - refers to O2 in solution and is determined by O2 solubility

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3
Q

What percentage of arterial O2 is extracted by peripheral tissues at rest?

A

25%

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4
Q

What percentage of oxygen is bound to haemoglobin in each litre of systemic arterial blood?

A

98%, the rest is dissolved in plasma

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5
Q

Describe how O2 binds to haemoglobin

A

Co-operatively to 4 molecules of oxygen.

1.34ml O2 binds to each gram of haemoglobin.

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6
Q

Describe the difference between arterial partial pressure of O2 and arterial O2 content

A

Arterial partial pressure - the O2 in solution, determined by O2 solubility

Partial pressure of O2 - in the gaseous phase that is driving O2 into solution

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7
Q

Describe how the demand of 250ml/min of O2 from resting tissues is met

A

150g/l of haemoglobin binds 1.34ml of O2 per g, so with a cardiac output of 5L/min the O2 delivery to tissues would be 1000ml/min

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8
Q

Describe the HbA form of haemoglobin

A

Makes up 92% of haemoglobin in RBC

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9
Q

Describe the HbA2 form of haemoglobin

A

Delta chains replace beta chains

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10
Q

Describe the HbF form of haemoglobin

A

Gamma chains replace beta chains

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11
Q

Describe the glycosylated Hb form of haemoglobin

A

Glucose molecules are added on to the haemoglobin. Useful in the diagnosis of diabetes and how its being controlled

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12
Q

State the haemoglobin saturation at the normal systemic arterial PO2 of 100mmHg

A

100%

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13
Q

State the haemoglobin saturation at PO2 60mmHg

A

90%

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14
Q

Describe the saturation of foetal haemoglobin in relation to normal haemoglobin at any given partial pressure of oxygen

A

HbF (foetal haemoglobin) has a higher affinity for O2 than HbA to extract O2 from maternal blood, therefore is more saturated at any given Kpa

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15
Q

Describe the saturation of myoglobin in relation to normal haemoglobin at any given partial pressure of oxygen

A

Myoglobin has a higher affinity for O2 than HbA to extract O2 from arterial blood, is therefore more saturated at any given Kpa

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16
Q

Describe anaemia

A

Any condition where the oxygen carrying capacity of the blood is compromised

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17
Q

State examples of when anaemia may occur

A
  • iron deficiency
  • Haemorrhage
  • vitamin B12 deficiency (involved in production of red blood cells)
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18
Q

Describe the affect of anaemia on PaO2

A

Normal, as gas exchange will still occur normally, however not enough oxygen is being exchanged to maintain total blood O2 conc. ie there is a problem with the blood cells not diffusion at the lungs

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19
Q

State the affect on RBC O2 saturation in anaemia

A

RBC would still be fully saturated with O2, the number of binding sites isn’t affected, only the amount of oxygen available to bind.

20
Q

An anaemic patient has an arterial oxygen content of 100m/l, what would be their % O2 saturation? Why?

A

Saturation ~100%, they have fewer cells/binding sites available but those that are available have oxygen bound.

21
Q

Describe the effect of increased/decreased pH on the affinity of haemoglobin for O2

A

Acidosis (decreased pH) decreases affinity of haemoglobin for O2 so decreases saturation

Alkalosis (increased pH eg increased CO2) increases affinity of haemoglobin got O2 so increases saturation

22
Q

Describe the effect of changes in PCO2 on % haemoglobin saturation

A

Decrease in PCO2 (20mmHg) increases the haemoglobin saturation

Increase in PCO2 (80mmHg) decreases the haemoglobin saturation

23
Q

Describe the effect of changes in temperature on haemoglobin saturation

A

Decrease in temperature causes an increase in haemoglobin saturation

Increase in temperature causes a decrease in haemoglobin saturation

24
Q

Describe the effect of addition/removal of 2,3-DPG

A

No 2,3-DPG causes an increase in haemoglobin saturation

Added 2,3-DPG causes a decrease in haemoglobin saturation

25
Q

What is 2,3-DPG

A

2,3-diphosphglycerate which is synthesis by erythrocytes.

Increases in situations associated with inadequate O2 supply.

Helps maintain O2 supply in tissues

26
Q

What is formed when carbon monoxide binds to haemoglobin?

A

Carboxyhaemoglobin, affinity is 250 times greater than O2

27
Q

State the symptoms expressed when CO binds to haemoglobin

A
  • hypoxia and anaemia
  • nausea and headaches
  • cherry red skin
  • respiration rate unaffected due to normal arterial PCO2
  • potential brain damage and death
28
Q

State the treatment for CO poisoning

A

Provide 100% O2 to increase PaO2

29
Q

Define hypoxia

A

Inadequate supply of oxygen to tissues

30
Q

State the 5 main types of hypoxia

A
  • hypoxia hypoxia
  • anaemic hypoxia
  • ischaemic hypoxia
  • histotoxic hypoxia
  • metabolic hypoxia
31
Q

Describe hypoxia hypoxia

A

Reduction in O2 diffusion at lungs either due to decreased PO2 or tissue pathology

32
Q

Describe anaemic hypoxia

A

Reduction in O2 carrying capacity of blood due to anaemia (RBC loss/iron deficiency)

33
Q

Describe ischaemic hypoxia

A

When heart disease results in inefficient pumping of blood to lungs/around the body

34
Q

Describe histotoxic hypoxia

A

When poisoning prevents cells utilising oxygen delivered to them eg in CO/cyanide poisoning

35
Q

Describe metabolic hypoxia

A

When O2 delivery to the tissues foes not meet increased O2 demand by cells

36
Q

Describe the ways in which CO2 is transported

A
  • 7% remains dissolved in plasma and erythrocytes
  • 23% combines in the erythrocytes with deoxyhaemoglobin to for carbamino compounds
  • 70% combines in the erythrocytes with water to forms bicarbonate
37
Q

Describe ‘chloride shift’

A

When CO2 combines with water to form bicarbonate, it moves out of the erythrocytes and into the plasma in exchange for Cl- ions and excess H+ ions bind to deoxyhaemoglobin.

Then carried to lungs in venous blood and reversed to allow dissolved CO2 to move into alveoli to be expired.

38
Q

Describe how respiratory acidosis is brought about

A

Through Hypoventilation which causes CO2 retention. The equilibrium of CO2-> HCO3- is shifted to the right causing more H+ ions to be produced and the pH to decrease

39
Q

Describe how respiratory alkalosis is brought about

A

Through hyperventilation, which allows more CO2 to be blown off. The equilibrium of CO2->HCO3- is shifted to the left which causes the H+ concentration to decrease which increases the pH

40
Q

State the PO2 in arterial blood

A

100mmHg

41
Q

State the PO2 in venous blood

A

40mmHg

42
Q

State the PCO2 in arterial blood

A

40mmHg

43
Q

State the PCO2 in venous blood

A

46mmHg

44
Q

State the PO2 in resting cells

A

40 mmHg

45
Q

State the PCO2 in resting cells

A

46mmHg

46
Q

State PO2 in the alveoli

A

100mmHg

47
Q

State the PCO2 in the alveoli

A

40mmHg

Respiratory System (20 decks)

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