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Resp > Lecture 4 - Oxygen In The Blood > Flashcards

Lecture 4 - Oxygen In The Blood Flashcards

1
Q

What criteria must an oxygen carrier meet?

A

Reaction must be reversible

Carrier must associate with O2 at lungs but dissociate at tissues

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2
Q

Describe the structure of haemoglobin:

A

Made of 2 alpha and 2 beta subunits

Each subunit has 1 haem group
Each haem group can bind 1 oxygen molecule

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3
Q

How many oxygen molecules can a single Haemoglobin molecule transport?

A

4 oxygen molecules

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4
Q

What is cooperativity in terms of haemoglobin?

A

The change in haemoglobins affinity for oxygen as it changes shape

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5
Q

What are the 2 stages of affinity for haemoglobin?

A

T state (tense state)
R state (relaxed state)

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6
Q

What is the T state (tense state)?

A

When no oxygen is bound to haemoglobin it has a very low affinity for oxygen

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7
Q

What is the R state (relaxed state) of haemoglobin?

A

Once the first oxygen has bound it has a higher affinity for oxygen, as more and more oxygen binds the affinity for oxygen increases

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8
Q

What shape of curve is the haemoglobin-oxygen dissociation curve?

A

Sigmoidal curve

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9
Q

What is the relative partial pressure of oxygen in venous blood compared to arterial blood?

What affect does this have on haemoglobin?

A

pO2 in venous blood is low compared to arteries so highly saturated Hb will give up oxygen

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10
Q

What is considered a normal oxygen saturation?

A

95% or above

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11
Q

What is O2 saturation?

A

The percentage of haemoglobin that is saturated with O2

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12
Q

What 3 substances promote the release of O2 by shifting the equilibiurm to the deoxygenated form of haemoglobin (T state)?

A

H+
CO2
2,3-Diphosphoglycerate (2,3-DPG)

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13
Q

How does metabolic acidosis affect Haemoglobin-oxygen dissociation?

How does it affect the sigmoidal curve?

A

Metabolic acidosis means lots of H+ in blood

H+ encourages dislocation of oxygen from oxyhaemoglobin

More H+ shifts the oxygen dislocation curve to the right since a higher partial pressure of O2 will be needed to get the same level of saturation than if there was no extra H+

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14
Q

How are people living in high altitudes (with low pO2) adapted to maximise gas exchange?

A

High capillary density

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15
Q

What is Hypoxaemia?

A

When there’s a low partial pressure of O2 in arterial blood

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16
Q

What is hypoxia?

A

When the oxygen levels are low relative to the need in the body or tissues

So tissues using O2 faster than its delivered

17
Q

What is the difference between hypoxaemia and hypoxia?

A

Hypoxaemia is when the partial pressure of O2 ini arterial blood is low

Hypoxia is when oxygen levels are low relative to the bodies demand

18
Q

How is the blood composition affected by anaemia?

A

Reduced amount of haemoglobin in blood

19
Q

How does oxygen saturation in the blood of a normal person compare to that with a person with anaemia?

A

Oxygen saturation is the same since there is no haematological problem with the haemoglobin so any haemoglobin available still gets saturated like normal theres just less of it

20
Q

What does a shift to the left in the oxygen dislocation curve indicate in terms of Hb affinity?

What does a shift to the right in the oxygen dislocation curve indicate in terms of Hb affinity?

A

Left = increase haemoglobin affinty for oxygen since lower partial pressure of O2 needed to fully saturate Hb

Right = decreased haemoglobin affinity for oxygen since higher partial pressure of O2 needed to fully saturate O2

21
Q

How does 2,3-diphosphoglycerate affect haemoglobins affinty for oxygen?

A

It decreases its affinity fo oxygen by binding to the beta chains

22
Q

How does temperature affect haemoglobins affinty for oxygen and why?

A

At higher temperatures Hb affinity for oxygen is less

In highly metabolically active tissues temperature is high, these tissues need oxygen so the Hb has a decreased affinty for oxygen so it gives it up for these tissues

23
Q

What is the Bohr effect?

A

H+ levels and pCO2 levels are high the affinity of Hb for O2 decreases so it gives up O2 more easily (levels of these are high around highly metabolically active tissues)

24
Q

What is the Haldane effect?

A

Deoxygenated Hb has a higher affinity for CO2 due to Allosteric modulation of CO2 binding sites

25
Q

How does Carbon monoxide affect Hb affinity for oxygen?

A

Carbon monoxide increases Hb affinity for Ooxygen

This makes it so the Hb is unable to dissociate and deliver any of the oxygen to the target tissues

CO also competes with oxygen for space on the binding sites of Hb

26
Q

What are the symptoms of carbon monoxide poisoning?

A

Headache
Nausea
Vomiting
Slurred speech
Confusion
Intially few respiratory symptoms

27
Q

How is Carbon monoxide poisoning dangerous?

A

Hb has a much higher affinity for CO than O2

Means less O2 can be transported with CO bound
CO increases the affinity of unaffected subunits for oxygen making Hb more reluctant to give up O2 so the tissues receive less O2

28
Q

What are the 2 types of cyanosis?

A

Peripheral cyanosis (hands and feet)

Central cyanosis (mouth, tongue, lips and mucous membranes)

29
Q

What is more concerning peripheral cyanosis or central cyanosis?

A

Central cyanosis since it’s indicative of poorly saturated blood in circulation (Hypoxaemia)

Peripheral can happen due to poor circulation

30
Q

What oxygen saturations does cyanosis usually happen at?

A

Less than 90%

31
Q

Where in a persons hand would you look for peripheral cyanosis is they are ethnic?

A

Nail beds

32
Q

What does pulse oximetry measure?

A

O2 saturation

33
Q

How does pulse oximetry measure O2 saturation in blood?

A

It detects the difference in absorption of light between oxygenated and deoxygenated Hb

It only detects pulsation arterial blood levels

34
Q

What is the limitation of pulse oximetry?

A

Less accurate in darker coloured skin

Cant give info on Hb levels

Cant differentiate Carbon Monoxide poisoning

35
Q

What are the advantages of arterial blood gas?

A

Gives info on pO2, pCO2, pH, bicarbonate levels and electrolytes

36
Q

What are the disadvantages of arterial blood gas?

What artery is arterial blood gas taken?

A

Very invasive and painful

Radial artery

37
Q

Why does a patient with anaemia have a normal arterial partial pressure of oxygen (paO2)?

A

Oxygen bound to Hb doesn’t contribute to arterial partial pressure

Resp (23 decks)

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