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CP Exam 1 > Gas Transport > Flashcards

Gas Transport Flashcards

1
Q

How can we calculate the oxygen in our alveoli?

A

[Oxygen in our lungs] - [Oxygen used in our tissue]

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2
Q

How can we get oxygen (blood) to the tissue?

A
  1. Dissolved O2
  2. Hemoglobin
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3
Q

Why does oxygen not dissolve well in plasma?

A

Because it is lipophillic,

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4
Q

What is the solubility of O2 in the plasma?

A

0.3 ml O2/dl blood/ 100 mmHg

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5
Q

If the PaO2 is 100mmHg, how much oxygen will each dL of blood carry?

A

0.3 mL of O2

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6
Q

What is the metabolic demand of our heart?

A

250 mL of oxygen/ minute

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7
Q

How many times would our hearts have to pump to meet the metabolic demands of our heart of we could only transport oxygen by dissolving it in the blood?

A

83 liters of blood/ minute

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8
Q

What is PaO2?

A

The partial pressure of oxygen that is DISSOLVED in the arterial blood.

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9
Q

What is a better way to transport O2 in the blood?

A

Hb

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10
Q

How can we check how much oxygen is bound to Hb?

A

We can measure the dissolved O2 in our plasma, because it is in equillibrium with the amount bound to Hb.

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11
Q

What does the oxygen-Hb dissociation curve show?

A

It shows how oxygen is released from Hb.

It shows cooperativity- once one O2 binds to Hb, it makes it easier for others to bind.

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12
Q

PO2 in the systemic arteries is what?

What is the Hb saturation?

A

100.

This makes Hb about 100% saturated.

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13
Q

PO2 in the systemic veins is what?

What is the Hb saturation?

A

40.

At PO2 of 40, our Hb is 75 saturated.

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14
Q

How can we find the amount of oxygen that is unloaded to the tissue?

A

The percent difference from the arteries and veins is the % difference that is unloaded to the tissues.

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15
Q

When the PO2 is 60mmHg, what is the saturation?

A

85% saturation

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16
Q

At any PO2>60 mmHg, the Hb is at least ____ saturated with oxygen.

What does this mean?

A

85%.

At 100%, our oxygen content is 20.1 mL O2/dl of blood.

20.1 ml/dl blood * 85%=

At 85%, we have 17mL of O2/ dl blood.

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17
Q

What does a leftward shift in the Hb-O2 curve for HbA show?

A

An increase in affinity of Hb for O2.

O2 loads onto Hb easier, making less O2 available to be used by the tissue (because it wants to stay bound?

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18
Q

What does a right shift in the Hb-O2 curve of HbA show?

What does this mean?

A

Rightward shift–> the affinity for Hb for O2 is decreased.

Therefore, it is not holding onto the O2 as tightly and wants to deliver it to the tissue.

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19
Q

Metabollically active tissue wants a _______ affinity for oxygen.

Shift to the _____.

A

Decrease

RIGHT

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20
Q

What factors affect the affinity of Hb for O2?

A
  1. CO2 and/or pH
    * *We cannot change CO2 without changing the pH.*
  2. Temperature
  3. 2,3 DPG
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21
Q

When CO2 and or pH changes the Hb-O2 curve, what is this called?

A

Bohr effect.

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22
Q

How does CO2, pH or H+ affect the curve?

A
  1. High CO2= High H+ = low pH= shift to the right= decrease in the affinity
  2. Low CO2= low H+= high pH= left shit= increase affinity
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23
Q

How does temperature affect the Hb-O2 curve?

A

Increase temperature= right shift= decrease affinity

Decreased temperature= left shift= increase affinity

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24
Q

How does 2,3 DPG affect the Hb-O2 curve?

A

Increase 2,3 DPG= right shift= decrease affinity

Low 2,3 DPG= left shift = increase affinity

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25
Q

When do we see increases in CO2 and or H+, temperature or 2,3 DPG?

A

In the tissue.

26
Q

When do we see decreases in CO2 and or H+, temperature or 2,3 DPG?

A

In the lungs

27
Q

Fetal Hb has a _____ affinity. Why?

A

Higher.

Because it needs to take O2 from moms blood.

28
Q

We want our lungs to have _____ affinity.

A

Higher.

29
Q

Because we want our lungs to have a higher affinity, what will their temperature be?

A

Cooler than the rest of the body.

30
Q

Is all oxygen taken up by the tissue?

A

No. Our PaO2 is about 100mmHg

PvO2 is about 40mmHg

31
Q

The O2 saturation of venous blood is what?

A

At 40mmHg, it is about 75%/

Thus the O2 content is 20.1 mL O2/dl blood * 75%= 15.2 ml O2/ dl blood is present in our venous blood.

32
Q

Our venous blood has a oxygen content of 15.2 ml O2/dl blood. Where did the rest go?

A

TISSUE

33
Q

a-vO2 difference

A

a-vO2 difference- the difference between the arterial O2 content and the venous content, indicated how much oxygen was used by the tissue being perfused.

34
Q

Was is the normal a-vO2 difference?

A

4.6 ml O2/dl blood

35
Q

a-v O2 varies substantially. How so? Why?

A
  1. Adipose tissue removes very little O2 from the blood.
  2. Skeletal muscle removes much more O2.

Why: Oxygen utilization for the two tissues is v different.

36
Q

Is there a relationship between the amount of O2 consumed and CO2 produced? What is this determined by?

A

Yes, there is a consistent relationship between the amount of O2 consumed and the amount of CO2 produced.

-This relationship (ratio) is determined by the fuel being utilized by the cells.

37
Q

If cells are utilizing carbs (sugars or dextrose)

What is the ratio of CO2 produced and O2 consumed?

A

1:1 ratio.

1 CO2 produced for every 1 O2 consumed.

38
Q

If cells are utilizing fats (sugars or dextrose)

What is the ratio of CO2 produced and O2 consumed?

A

The ratio is 7:10 (or 0.7)

7 CO2 produced for every 10 O2 consumed.

39
Q

Do we usually use carbs or fats as fuels?

A

We usually use a mix of both (with mostly fats)

200 ml CO2 produced for every 250 ml of O2 consumed

-Ratio is 0.8 (8:10(

40
Q

What is the respiratory quotient? (RQ)

A

RQ= the ratio between CO2 produced and O2 consumed.

41
Q

How do we solve for the respiratory quotient (RQ)?

A

RQ= volume of CO2 produced/ volume of O2 consumed= V(dot)CO2/V(dot)O2

We can use this equation to get RQ, CO2 production or O2 consumption.

42
Q

What is our RQ under normal conditions?

A

200 mlCO2 produced/ 250 ml O2 consumed= 0.8

43
Q

To solve an equation, when do we use RQ= 0.7 or 0.8?

A

0.7= carbs

0.8= fats

44
Q

SUMMARY:

  1. How is oxygen transported?
  2. What is the MAJOR transport of O2?
  3. What changes the affinity of Hb for O2?
  4. What occus at the cells (tissues)?
  5. What does the a-vO2 difference tell us?
  6. What does RQ tell us?
  7. How does metabolic substrate (fuel) change the RQ?
A
  1. Dissolved in plasma or bound to Hb
  2. Hb
  3. Temp, CO2, H+, pH, 2,3 DPG
  4. At the tissue, O2 leaves Hb and enters the tissues for metabolic use.
  5. Tells us how much O2 was used by the tissue.
  6. RQ= how much CO2 was made for each molecule of O2 consumed
  7. Changes depending on what fuel is being used (glucose v ffa vs. mixture)
45
Q

iBook Pic

A
46
Q

How can CO2 be transported in the blood?

A

1. Dissolved in plasma

2. Carbamino compounds

3. As HCO3

47
Q

How much CO2 can be dissoolved in plasma?

A

6 ml O2/ dl blood/ 100 mmHg

48
Q

How much CO2 is dissolved in each dl of blood?

A

2.7 ml of CO2

because the PCO2 of the venous blood is 45 mmHg.

49
Q

Is enough CO2 dissolved in the plasma for our metabolic needs?

A

No. we would need a CO higher than 5L/min to deal with the amount of CO2 made very minute (~200 mL CO2)

50
Q

CO2 can bind to Hb to form carbamino compounds. How does this occur and how much CO2 is carried away by this mechanism?

A

CO2 binds to the amine groups of the Hb chains. Oxygen present on the heme reduces the affinity for the Hb chain for CO2–> haldane shift.

3 ml/dl of blood (7% of the total).

51
Q

How is most of the CO2 in the blood carried away?

A

By Bicarb (HCO3)

-86% of the total (44 mL of CO2)

52
Q

Why do we carry more CO2 in the blood than O2?

A

Because kidneys are adding CO2 in the blood.

53
Q

CO2 can diffuse into RBC and be converted to HCO3- and H+. Tell me all about this.

A
  • AT TISSUES LEVEL; SO, CO2 moves into the RBC. Carbonic anhydrase is present here. Inside the RBC, CO2+H20–>Carbonic acid. Carbonic acid quickly dissociates to bicarbonate and hydrogen ions. Hydrogen ions can be harmful. So, we must buffer then somehow. Solution?
    • Hemoglobin acts as a buffer and can bind H+ ions. It then keeps them out of circulation.
  • These are reversible reactions. As HCO3- is produced, the forward reaction tends to slow. To keep the reaction moving forward, it must be removed from the cell. To do this we have an EXCHANGE TRANSPORTER on the cell membrane.
    • It exchanges a bicarbonate molecule for a chloride molecule. Bicarbonate comes in and chloride moves out. This is referred to as the Chloride shift. Chloride shift allows the conversion of CO2àHCO3-. Occurs at tissue level.
  • AT LUNG LEVEL (when we get back to the alveoli), we need to reverse these processes (b/c CO2 is lost)
    • CO2 levels decrease. To decrease:
      • Some of the CO2 dissolved in plasma will leave. CO2 bound to hemoglobin will be released. But we have 70% in the form of bicarbonate. In order to release it, we have to convert it BACK to CO2.
        • Now, the Chloride shift works in the opposite direction. Cl is sent out and HCO3- is put back in the RBC. HCO3- combines with H+ to from H2CO3, which dissociates into CO2 and H2O.
54
Q

Venous blood has _____ plasma chlohride (it is located ____.

A

LOWER

inside the cells.

This occurs because this proces is occuring in the venous blood.

55
Q

Back in the lungs, CO2 will go where? How?

A

Will move into the alveoli.

Dissolved CO2 will go down the gradient into the alveoli.

CO2 and H+ ions will leave the proteins as the dissolved CO2 moves into the alveoli.

HCO3 will be conberted back to CO@.

56
Q

What happens to H+

A

many of them are displaced from the Hb as O2 starts to bind.

57
Q

What is the role of CO2 in acidosis?

A

Because H2CO3 is also made, increases in plasma CO2 are assx with increased acidosis in the blood.

58
Q

What is the role of CO2 in Cl- transport?

A

HCO3- produced in the blood cell is pumped out of the cell in exchange for CL

59
Q

What happens in the lungs during CO2 tranport?

A

Equillibrium shifts back to dissolved CO2 and the CO2 is exhaled.

60
Q

What is the volume of O2 and CO2 carried in the blood?

A

O2- ~20 mL O2/dL blood

~50 mL CO2/dL blood

61
Q

What is the volume of O2 and CO2 dissolved?

A

0.3 mL of O2/ dL blood

~3 mL CO2/dL blood

62
Q
A

CP Exam 1 (29 decks)

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