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Respiratory > ABGs > Flashcards

ABGs Flashcards

1
Q

What is the main buffer in blood?

A

bicarb/CO2

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2
Q

What is the role of Hb in the maintenance of blood pH

A

Hb can donate or accept electrons

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3
Q

What is meant by the term “positive cooperativity”?

A

Hb becomes more efficient at binding oxygen as oxygen levels increase

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4
Q

What is the T state of Hb? What is the chemical change that allows for this?

A

“tense” state, where Hb has a low affinity for oxygen

Beta subunits are blocked by a Valine residue

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5
Q

What is the R state of Hb?

A

High oxygen affinity state.

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6
Q

What is the change that occurs going from the T state to the R state?

A

Oxygen binding to the alpha subunits in the T state, cause the valine residue in the beta subunit to move away from the binding site of oxygen

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7
Q

What stabilizes the R form, factors that increase the strength of bonds between subunits, or factors that decrease? Why?

A

Decrease, since stronger bonding means less likely to move Valine residue out of the way in the beta chain

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8
Q

What is the role of 2,3 BPG?

A

The negatively charged 2,3 BOG interacts with the positively-charged amino-termini of the beta chains, and also with specific K and H residues within the beta chains

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9
Q

What is the Bohr effect?

A

Increased H+ formed from metabolizing tissues is absorbed by Hb Histidine residue, stabilizing the T state

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10
Q

What happens with the Bohr effect in the lungs?

A

H+ leaves the Hb d/t need to form CO2 from bicarb, stabilizing the R state

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11
Q

What is the interaction between CO2 and Hb besides the Bohr effect?

A

CO2 binds to the N terminal end of the subunit, forming a carbamate and salt bridge formation, thus stabilizing the T state

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12
Q

What are the three forms in which CO2 is transported?

A
  • Dissolved CO2 gas
  • Combined to N terminal Hb
  • Bicarb
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13
Q

What percent of CO2 is transported as bicarb?

A

80-90%

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14
Q

What is the only form CO2 can take that does not contribute a H+ to the serum?

A

Dissolved CO2

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15
Q

What form of CO2 is the only form that can pass through the alveolar capillaries?

A

CO2 gas

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16
Q

What is the Haldane effect?

A

At any given partial pressure of CO2, oxygenated blood contains less total CO2 than deoxygenated blood at the same partial pressure of CO2

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17
Q

Which is a stronger base: deoxyhemoglobin, or oxyhemoglobin? What is the consequence of this?

A

Deoxyhemoglobin, meaning that deoxygenated blood more readily accepts H+ from the solvation of CO2 than oxygenated blood

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18
Q

Why is it that the amount of oxygen dissolved in the blood is very low, but is extremely important?

A

Since this is the form that:

  • Diffuses from lungs into blood
  • enters erythrocytes
  • binds Hb
19
Q

Anything that increases what type of bond will reduce the oxygen affinity of Hb (stabilize the T form)?

A

Salt bridge formation

20
Q

What is the effect on the PO2 vs hemoglobin saturation curve with increases in [H]? PCO2? 2,3 BPG?

A

All shift the curve to the right (lower the % oxygen saturation at every level of PCO2)

21
Q

What is the enzyme in RBCs that takes CO2 from the blood and turns it into H2CO3?

A

Carbonic anhydrase

22
Q

What ion in the serum is exchanged for HCO3 in the RBC?

A

Cl-

23
Q

What is the Henderson-Hasselbach equation?

A

pH = pKa + log(base/acid)

24
Q

What is the simplification made for the henderson-hasselbach equation when calculating the pH of the bicarb buffer?

A

Very little H2CO3 present (almost all is either dissolved CO2, or HCO3) Thus the [CO2] is substituted for the “acid” in the equation

25
Q

What is the equation for the CO2 buffer in the blood?

A

pH = 6.1 + log ([HCO3]/0.03pCO2)

26
Q

What is the normal PCO2 in the blood?

A

40 torr

27
Q

What is the normal [HCO3] in the blood?

A

24 mM

28
Q

What is the normal [HCO3]/[CO2]?

A

20/1

29
Q

What is the normal pH of the blood?

A

7.4

30
Q

What are respiratory acid/base imbalances?

A

Blood pH changes that are the result of changes in PCO2

31
Q

What are metabolic acid/base imbalances?

A

Blood pH changes that are the result from changes in [HCO3]

32
Q

Why is it that pH can be normal despite having abnormal [CO2] and [HCO3]?

A

It’s the ratio of the two that matter, not the absolute value of one

33
Q

How is hypoventilation reflected on the pH vs [HCO3-] graph?

A

Shifs to the right

34
Q

How is hyperventilation reflected on the pH vs [HCO3-] graph?

A

Shifts to the left

35
Q

What is the normal buffer slope in the pH vs [HCO3] graph? What determines the slope?

A

Represents the effect of other blood buffers on [HCO] and pH as PCO2 varies

Mostly represents the effect or [Hb]

36
Q

Why is it that the pH values predicted by the henderson hasselbach equation are not always precise?

A

Does not take into account other buffers in the blood, namely the Hb buffer

37
Q

How are metabolic disturbances reflected in the pH vs [HCO3] graph?

A

Shifts along the curve of a PCO2 isobar

38
Q

How are respiratory disturbances reflected in the pH vs [HCO3] graph?

A

Shifts of the PCO2 isobar

39
Q

How does the body compensate for acidosis/alkalosis?

A

Will shift the non-affected variable to maintain the ratio of [HCO3]/PCO2

40
Q

What are the two major organ systems that regulate the pH of the blood?

A

Lungs and kidneys

41
Q

What is the compensatory reaction for metabolic acidosis, and how is this reflected in the pH vs [HCO3] graph?

A

Initial shift down the isobar, but then shift to the right of the curve

42
Q

What is the compensatory reaction for respiratory acidosis, and how is this reflected in the pH vs [HCO3] graph?

A

Shift of the curve to the left, followed by a slow increase in the | slope | of the compensatory curve

43
Q

What is the compensatory reaction for respiratory alkalosis, and how is this reflected in the pH vs [HCO3] graph?

A

Shift of the curve to the right, followed by a decrease in the compensatory curve | slope |

44
Q

What is the compensatory reaction for metabolic alkalosis, and how is this reflected in the pH vs [HCO3] graph?

A

Initial change along the curve, then change in the slope of the curve to the left

Respiratory (34 decks)

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