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Respiratory > Session 3- Oxygen in blood and tissues > Flashcards

Session 3- Oxygen in blood and tissues Flashcards

1
Q

R state

A

High affinity for oxygen in R state - easier for oxygen to bind

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2
Q

T state

A

Low affinity for oxygen in T state - difficult for oxygen to bind

when Hb is at the tissues so o2 is more likely to be released and given up to the metabolically active tissues

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3
Q

Cooperativity

A

As each o2 binds the molecule becomes more relaxed ad binding of the next o2 molecule is easier

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4
Q

Why does gas pressure change when it enters our upper respiratory tract

A

It is humidified with water vapour

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5
Q

What is the partial pressure of oxygen in the URT vs alveoli

A

URT- pO2 = 19.8 kPa

Alveoli =13,3 kPa

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6
Q

Why is there a difference between the partial pressure of oxygen in the URT vs alveoli

A

When we breath we do not completely replace all teh air in our lungs

Older air has had o2 continually extracted and CO2 constantly being added

Hence percentage o2 less in alveolar air, hence pAo2 is lower than in URT and pAco2 high

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7
Q

PAco2 vs paCo2

A

A- alveoli a- arterial bloo

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8
Q

When gases are dissolved in body fluids when is equilibrium reached

A

Rate of gas entering liquid = rate of gas leaving the water

The partial pressure of the gas in the liquid = partial pressure of the has in the air above it

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9
Q

What does pO2 reflect

A

The amount of dissolved O2 in the blood not including Hb bound oxygen

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10
Q

Factors affecting rate of diffusion

A

The solubility of the gas in teh liquid; greater the solubility, faster the rate of diffusion

Molecular weight if the gas
-higher the molecular weight slower the rate of diffusion

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11
Q

What is the diffusion coefficient used to determine

A

The relative rates at which different gases will diffuse acros the same membrane at th same pressures

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12
Q

Which diffuses faster and why between CO2 and o2

A

CO2 much mire soluble than o2- so diffuses faster than o2
Molecular weight of CO2 is larger than o2

However co2 is faster

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13
Q

Why is o2 gas exchange more impaired in diseased lungs

A

In diseased lung with lower alveolar o2 partial pressure, there is a less partial pressure gradient. O2 gas exchange more impaired tha co2 because of o2 being less soluble

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14
Q

What is the diffusion barrier room alveolar air to RBC

A 
Fluid film lining alveolus 
Epithelial cell of alveolus 
Interstitial space 
Endothelial cell of capillary 
Plasma 
Red cell membrane
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15
Q

Factors affecting rate of gas diffusion- disease examples

A

Thickness of the membrane
-increase as a result of oedema fluid in the interstial. Space and in alveoli

Surface area of the membrane
-emphysema

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16
Q

What changes in diseases with impaired diffusion

A
  • co2 always diffuses much faster tha o2
  • so diffusion of o2 affected -> pO2 is low
  • difffusoon of co2 not affected -> pCo2 normal
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17
Q

What happens when PAO2 is low

A

Hypoxia vasoconstriction of pulmonary arterioles occurs

-this diverts blood to between ventilated alveoli

18
Q

What is hypoxaemia

A

Low partial pressure oxygen in arterial blood

19
Q

Why cant over-ventilated alveol compensate for under-ventilated alveoli

A

98% of our oxygen carried on Haemoglobin
2% oxygen content is dissolved oxygen

Haemoglobin is already carrying all that it can carry - it is saturated

20
Q

What is decompression sickness in divers

A

Nitrogen moved from high pressure in the lungs into the blood- low pressure

A slow return to the surface lets the nitrogen rein to the lungs where it is breathed out

Swimming up too quickly doesnt give the nitrogen enough time to leave the blood - instead it can form painful bubbles

21
Q

When does optimal gas exchange occur

A

When ventilation and perfusion are matched at the alveolar capillary level

22
Q

R state

A

High affinity for oxygen in R state -easier for oxygen to bind

23
Q

What is cooperativity

A

When the partial pressure is low Hb is tense so ut is ahead for the first o2 molecule to bind

As each o2 binds the molecule becomes more relaxed and binding of the next o2 molecule is easier

24
Q

What is alveolar pO2

A

13.3 kPa

25
Q

How do we calculate the total content of O2 in the blood

A

1) partial pressure of o2 in arterial blood x solubility Coe-efficient of oxygen in plasma which is 0.01mmol/L/kPa X 13.5Kpa = 0.135mmol/L

Then we add the amount attached to haemoglobin
2.2mmol/L - normal Hb conc

4 Hb on each Hb
4x 2.2 =8.8 mmol/L

Total = 0.135 + 8.8mmol/L

26
Q

How do we measure adequacy of oxygenation

A

Oxygen saturation - Sats

Arterial blood gas- ABG

27
Q

What is alveolar pCo2

A

5.3Kpa

28
Q

What does increasing the pO2 in our lungs to more than 13.3kPa do to the total content of oxygen in the blood

A

Nothing because the oxygen content is primarily determined by the o2 carried on haemoglobin and it is sarated at 13.3kpa

29
Q

What increases Hb unloading

A

Bohr shift
Increases in temp
Drop in pH
Increases in 2,3 DPG

30
Q

What is teh total amount of oxygen in the blood determined by

A

The oxygen bound to haemoglobin and the amount of oxygen and the amount of oxygen dissolved in the blood which is low because oxygen has a low solubility in blood

31
Q

What is the arterial partial pressure of oxygen determined by

A

Function of the amount of dissolved oxygen which depends on the alveolar pO2 not the amount of o2 on Hb

32
Q

Why does someone with anaemia have a normal arterial partial pressure of oxygen

A

Oxygen bound to Hb does not contribute to arterial partial pressure as it is no longer a free gas but rather chemically bound

33
Q

What is the partial pressure of oxygen in venous blood

A

5.3-6kpa

34
Q

How low can tissue pO2 get

A

Cannot fall below 3Kpa

35
Q

What is teh effect on CO in the O2 dissociation curve

A

Causes a leftward shift in oxy-haemoglobin

Reduced o2 release

36
Q

Signs of carbon monoxide poisoning

A 
Headache 
Nausea 
Vomiting 
Slurred speech 
Confusion
37
Q

What is hypoxaemia

A

Low partial pressure of oxygen in arterial blood

38
Q

What is hypoxia

A

Low oxygen levels relative to need in body or tissues

39
Q

What is cyanosis

A

Bluish colouration due to unsaturated b

Deoxygenated Hb is less red than oxygenated Hb

40
Q

What effect does elevated temp have on O2 curve

A

Shifts to the right - ,more easily released

41
Q

Lower pH on curve

A

Acidosis - shift to right

42
Q

What is p 50

A

the partial pressure of oxygen necessary to bind

50% of available haemoglobin

Respiratory (21 decks)

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