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Respiratory System > Pulmonary Blood Flow, Gas Exchange & Transport 2 > Flashcards

Pulmonary Blood Flow, Gas Exchange & Transport 2 Flashcards

1
Q

What is blood’s oxygen carrying capacity without haemoglobin?

(i.e. plasma only)

A

3ml/L

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2
Q

What is blood’s oxygen carrying capacity with haemoglobin?

A

200ml/L

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3
Q

Why does blood without haemoglobin have such a low oxygen carrying capacity?

A

Oxygen is poorly soluble in water, plasma is made up from 95% water.

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4
Q

Arterial partial pressure of O2 is the exact same as arterial O2 concentration/content.

True or False.

A

False

Arterial partial pressure of O2 is not the same as arterial O2 concentration/content.

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5
Q

The partial pressure of O2 refers to the O2 in both gas form and in solution in the plasma.

True or False.

A

False

The partial pressure of O2 refers purely to O2 in solution in the plasma.

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6
Q

The partial pressure of O2 is determined by O2 solubility and the partial pressure of O2 in the gaseous phase that is driving O2 into solution.

True or False.

A

True

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7
Q

The total oxygen content refers to oxygen in solution in the plasma and oxygen bound to haemoglobin of red blood cells.

True or False.

A

True

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8
Q

Why do we have 30x more oxygen molecules in the gaseous phase compared to the liquid phase in the plasma?

A

Oxygen has poor water solubility

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9
Q

The partial pressure of oxygen in liquid phase is equal to the partial driving that gas into solution.

True or False.

A

True

PP = 100 mm Hg

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10
Q

Gas is able to travel in its gaseous phase in the plasma.

True or False.

A

False.

Gases in the plasma could lead to a fatal air embolism.

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11
Q

The concentrations are the same between liquid and gases, but the partial pressures are different for a gas and that same gas being driven into solution.

True or False.

A

False

The concentrations are different between liquid and gases, but the partial pressures are the same for a gas and same gas being driven into solution.

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12
Q

Describe haemoglobin (Hb) structure.

A

4 polypeptide chains (2a, 2B) each associated with a haeme group.
Each heme group is able to bind 1 oxygen molecule.

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13
Q

What are the different types of Hb?

A

HbA
HbA(2)
HbF

HbA(1a)
HbA(1b)
HbA(1c)

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14
Q

What is the major determinant of the degree to which Hb is saturated with oxygen?

A

Partial pressure of oxygen in arterial blood.

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15
Q

Partial pressure of O2 in _______ is fundamental in determining how much O2 binds to Hb.

A

plasma

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16
Q

What does the levels of HbA1C tell us about?

A

HbA1C is glycosylated Hb.

All people have a basal level of this form of Hb, however people with diabetes may find their levels fluctuate. Therefore this can be used as a measure of how well a persons diabetes is being controlled.

If a person has a chronically elevated HbA1C, then this tells us that they have a poor long term glycaemic control.

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17
Q

How saturated is Hb at normal systemic arterial PO2 (100mm Hg)?

A

around 98%

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18
Q

How saturated is Hb at a reduced PO2 of 60mm Hg?

What does this tell us?

A

It is around 90%.

This means that there is still a relatively large uptake of oxygen by the blood even when alveolar PO2 is reduced (e.g. with asthma).

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19
Q

Why could it be misleading to refer to venous blood as deoxygenated?

A

Since venous blood still has Hb saturation of around 75% therefore it is still somewhat oxygenated, only less oxygenated than arterial blood.

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20
Q

What happens to the partial pressure of O2 in people with anaemia?

A

It is normal (100mm Hg)

The partial pressure of O2 gradient refers only to the O2 in solution in the plasma, it does not account for RBCs.

Anaemic’s have normal partial pressure of oxygen but lowered total blood oxygen content.

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21
Q

It is possible to have low P(a)O2, and normal total blood O2 content.

True or False.

A

False

It is not possible to have low P(a)O2, and normal total blood O2 content.

It is our partial pressure of oxygen that determines how much oxygen binds to Hb, it drives the O2 into solution in the plasma from its gaseous form in the alveoli where it is then grabbed up by Hb.

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22
Q

It is possible to have normal P(a)O2, while total blood O2 content is low.

True or False.

A

True

e.g. anaemia, 98% of oxygen is wrapped up in Hb, therefore if we do not have adequate amounts of Hb we will have low oxygen content despite the fact that the levels of O2 in the plasma may be normal (because it is saturated at only 3ml/L).

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23
Q

Is it possible for red blood cells to be fully saturated with O2 in anaemia?

A

Yes.

Red blood cells would still be fully saturated with oxygen as the partial pressure of oxygen is normal.

24
Q

An anaemic patient has an arterial oxygen content of 100ml/L (normal = 200ml/L). How saturated would you expect haemoglobin to be?

A. ~100%
B. 75%
C. 50%
D. <50%

A

A. around 100%

Why?
The partial pressure of O2 is normal, the primary determinant of haemoglobin saturation is the partial pressure of O2, if this is normal  the haemoglobin you have is going to be 100% saturated as it is normally, there might not be as much haemoglobin as normal (not as many RBCs as normal), but the Hb we have is fully saturated.

25
Q

What determines our total arterial oxygen content in blood?

Why?

A

How much oxygen binds to Hb.

Because 98% of total oxygen content is wrapped up in Hb.

26
Q

What is the main determinant of how much oxygen binds to Hb?

A

The amount of oxygen in the plasma, which is influenced by the partial pressure of oxygen.

27
Q

How does acidosis (decrease in pH) affect Hb binding saturation?

A

It reduces it

Curve shifts to the R

28
Q

How does an increase in carbon dioxide production affect Hb binding saturation?

A

It reduces it

Curve shifts to the R

29
Q

How does a decrease in body temperature affect Hb binding saturation?

A

It increases it

Curve shifts to the L

30
Q

How does a decrease in carbon dioxide production affect Hb binding saturation?

A

It increases it

Curve shifts to the L

31
Q

How does alkalosis (increase in pH) affect Hb binding saturation?

A

It increases it

Curve shifts to the L

32
Q

How does an increase in body temperature affect Hb binding saturation?

A

It reduces it

Curve shifts to the R

33
Q

Explain changes in CO2 production, body temperature and pH in terms of a person exercising.

A

During exercise:

CO2 production increases
Lactic acid increases (pH decreases)
Body temp increases

All of the above incur a shift to the R on the PPO2/Hb curve and thus decrease Hb affinity for O2 and decrease Hb saturation.

This makes sense seen as oxygen must readily be given off to tissues during exercise as their is an increased demand for O2.

34
Q

In reality, what homeostatic mechanisms are in place to meet additional O2 demands during, for example, exercise.

A

Increased rate and depth of breathing.

35
Q

How can the fatal possibilities of hypothermia be explained in terms of Hb saturation?

A

At extremely low temperatures (20degrees), the partial pressure of oxygen at the peripheral tissues (40mm Hg) still has a Hb saturation of 100% (or even greater) therefore Hb fails to unload O2 at peripheral tissues essentially depriving cells of oxygen which can be fatal.

36
Q

What is 2,3-DPG?

A

A byproduct of RBC metabolism, it is produced when RBC are under stress or there is an inadequate oxygen supply

37
Q

How does 2,3-DPG work?

A

It decreases Hb affinity for O2 by binding to Hb. It allows for O2 to be more easily unloaded at the peripheral tissues.

38
Q

In what circumstances may 2,3-DPG production be increased?

A

In cardiovascular or chronic lung pathology.

In persons living at high altitude, where there is a lower PO2.

39
Q

What would happen if there was no 2,3-DPG produced or present?

(to the curve, what does this mean?)

A

The curve would shift to the L.

Hb saturation would increase, affinity for O2 would increase and Hb unloading of O2 at peripheral tissues would decrease.

40
Q

What can be said about the nature of the curve for PO2 against Hb saturation.

A

The curve is dynamic, it is not static. It constantly responds to changes in chemical factors.

41
Q

Why is carbon monoxide a poison?

A

CO has a much higher affinity for Hb than oxygen does (250x more), therefore it pushes O2 off of Hb and it binds readily, it also does not offload easily thus the blood fails to transport O2 around the circulation to the peripheral tissues.

42
Q

What are the symptoms of carbon monoxide poisoning?

How do we treat CO poisoning?

A 
Hypoxia and anaemia
Cherry red skin
Mucous membranes
Nausea 
Headache

100% O2 to increase PaO2

43
Q

Why is respiratory rate unaffected in patients with CO poisoning?

A

Due to normal arterial partial pressure of carbon dioxide.

44
Q

What is hypoxia?

A

Inadequate supply of oxygen to the tissues.

45
Q

What is Hypoxaemic hypoxia?

A

Hypoxaemic hypoxia - reduction in O2 diffusion due to decrease in atmospheric O2 or lung pathology.

46
Q

What is Anaemic hypoxia?

A

Anaemic hypoxia - reduction in the O2 carrying capacity of the blood due to anaemia (RBC reduction/iron deficiency)

47
Q

What is Stagnant hypoxia?

A

Stagnant hypoxia - cardiovascular pathology leads decreases pumping action of heart

48
Q

What is Histotoxic hypoxia?

A

Histotoxic hypoxia - poisoning prevents cells utilising O2 provided to them (e.g. CO poisoning)

49
Q

What is Metabolic hypoxia?

A

Metabolic hypoxia - oxygen delivery to the tissues does not meet demand by cells (e.g. extreme exercise)

50
Q

What is the most common type of hypoxia?

What lung pathology can lead to this?

A

Hypoxaemic hypoxia

Lung fibrosis, emphysema, pulmonary oedema

51
Q

How is carbon dioxide dissolved into the blood from the peripheral tissues?

A

7% dissolves in plasma in solution

23% combines in the RBC with deoxygenated Hb to form carbamino compounds.

70% combines in the RBC with H2O to form carbonic acid, which then dissociates into H+ ions and bicarbonate.

52
Q

What is the name of the enzyme which leads to the formation of carbonic acid?

A

Carbonic anhydrase

53
Q

What happens to the bicarbonate in the RBC?

A

Most of it transfers into the plasma in exchange for chloride ions, this is known as the chloride shift.

54
Q

What causes a respiratory acidosis?

A

Hypoventilation

Increase in CO2 retention, more H+ ions in ECF, pH decreases

55
Q

What causes a respiratory alkalosis?

A

Hyperventilation

Decrease in CO2 retention, less H+ ions in ECF, pH increases

56
Q

How could you combat a metabolic alkalosis?

A

Hypoventilation, consciously controlling rate and depth of breaths

Respiratory System (26 decks)

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