SM_159a: Acid Base

Question 1

What is the formula for pH?

Answer 1

pH = log (1 / H⁺) = – log [H⁺]

(as [H⁺] increases, pH decreases)

Question 2

What are two common acidic groups?

Answer 2

Question 3

What is an anion?

Answer 3

Conjugate base of an acid

Question 4

What is a buffer?

Answer 4

A buffer is a combination of acid + conjugate base which minimizes changes in H⁺

Question 5

What is pK?

Answer 5

pK = pH at which [acid] = [conjugate base]

Question 6

Buffers are most effective at pK _____ pH unit(s)

Answer 6

Buffers are most effective at pK ± 1 pH unit

Question 7

What is acidemia?

Answer 7

[H⁺] is elevated in blood and pH is decreased below normal (< 7.35)

Question 8

What is alkalemia?

Answer 8

[H⁺] is decreased in blood and pH is elevated from normal (> 7.45)

Question 9

What is acidosis?

Answer 9

Process tending to decrease pH or increase [H⁺]

Says nothing about the specific pH

Question 10

What is alkalemia?

Answer 10

Process tending to increase pH or decrease [H⁺]

Says nothing about the specific pH

Question 11

What is a respiratory process?

Answer 11

Process in which P_aCO₂ is changed

Question 12

Respiratory acidosis is caused by ________

Answer 12

Respiratory acidosis is caused by hypoventilation

Question 13

Respiratory alkalosis is caused by _______

Answer 13

Respiratory alkalosis is caused by hyperventilation

Question 14

Metabolic acidosis is caused by ________ or ________

Answer 14

Metabolic acidosis is caused by the addition of nonvolatile (fixed) acid (e.g. lactic acid) or loss of base

Question 15

Metabolic alkalosis is caused by ________ or ________

Answer 15

Metabolic alkalosis is caused by addition of bases (e.g. sodium bicarbonate) or loss of acid

Question 16

What is a buffer?

Answer 16

A substance that reduces a change in pH or [H⁺] when an acid or base is added or subtravted

Question 17

Describe the bicarbonate buffer system

Answer 17

• pK = 6.1 which is > 1 pH unit from pHa of 7.4 (effective because lungs continuously expire CO₂)
• Buffers metabolic acids or bases
• Primary extracellular buffer

Question 18

What is the isohydric principle?

Answer 18

• The bodies contains multiple buffer pairs (HA and A-) which are all in equilibrium with each other via their effect on [H⁺]
• Altering equilibrium of one buffer pair alters the [H⁺] and equilibrium for all buffer pairs

Question 19

In the isohydric principle, _____ buffer pairs contribute to equilibrium pH

pH can be calculated from _______

Answer 19

In the isohydric principle, all buffer pairs contribute to equilibrium pH

pH can be calculated from knowledge of the ratio of any one of the buffer pairs

Question 20

What is the Henderson-Hasselbach equation?

Answer 20

Question 21

On the PCO₂ – HCO₃^- diagram, slope ______ as pH increases

Answer 21

On the PCO₂ – HCO₃^- diagram, slope increases as pH increases

Question 22

On the Davenport idagram, slope _____ as PCO₂ increases

Answer 22

On the Davenport idagram, slope increases as PCO₂​ increases

Question 23

What happens when you give an HCl bolus to a ventilated patient?

Answer 23

Metabolic acidosis

• Shifts buffer equations: H⁺ + HCO₃^- -> CO₂ + H₂O such that there is a pronounced decrease in [HCO₃^-]

Question 24

Uncomplicated metabolic acidosis is indicated by _____ pH and caused by ______ HCO₃^-

Answer 24

Uncomplicated metabolic acidosis is indicated by decreased pH and caused by decreased HCO₃^-

Question 25

In metabolic acidosis, the nonbicarbonate buffer reaction ______ the decrease in [HCO₃^-]

Answer 25

In metabolic acidosis, the nonbicarbonate buffer reaction reduces the decrease in [HCO₃^-]

(isohydric buffering)

Question 26

What happens when you give an NaOH bolus to an artificially ventilated subject?

Answer 26

Metabolic alkalosis

Question 27

Uncomplicated metabolic alkalosis is indicated by _____ pH and caused by ______ HCO₃^-

Answer 27

Uncomplicated metabolic alkalosis is indicated by increased pH and caused by increased HCO₃^-

Question 28

In metabolic alkalosis, the nonbicarbonate buffer reaction ______ [HCO₃^-]

Answer 28

In metabolic alkalosis, the nonbicarbonate buffer reaction increases [HCO₃^-]

Question 29

Respiratory processes are buffered by __________

Answer 29

Respiratory processes are buffered by nonbicarbonate buffers only

Question 30

In respiratory processes, _____ HCO₃^- is produced per H⁺ added

Answer 30

In respiratory processes, 1 HCO₃^- is produced per H⁺ added

Question 31

In respiratory processes, many added H⁺ ions are bound to _________

Answer 31

In respiratory processes, many added H⁺ ions are bound to nonbicarbonate buffers

Question 32

In respiratory acidosis, PCO₂ _______

Answer 32

In respiratory acidosis, PCO₂ increases

Question 33

In respiratory alkalosis, PCO₂ ________

Answer 33

In respiratory alkalosis, PCO₂​ decreases

Question 34

What is the nonbicarbonate buffer value?

Answer 34

Nonbicarbonate buffer value = ∆[H⁺] / pH unit

Question 35

On the graph, _______ is equal to the nonbicarbonate buffer value

Answer 35

On the graph, the slope of B-A-C is equal to the nonbicarbonate buffer value

Question 36

Slope of the Davenport diagram ( [HCO₃^-] versus pH graph) is determined by ______________

Answer 36

Slope of the Davenport diagram ( [HCO₃^-] versus pH graph) is determined by the amount of nonbicarbonate buffer present

(larger amounts produce greater slope)

Question 37

In respiratory acidosis, hypoventilation _________

Answer 37

In respiratory acidosis, hypoventilation increases PCO₂

Question 38

Describe the effect of nonbicarbonate buffers in respiratory acidosis

Answer 38

1. Nonbicarbonate buffers remove some H⁺
2. Reduces decrease in pH but favors additional hydration of CO₂ and production of more HCO₃^- (and H⁺)

The greater the [Buff-], the more HCO₃^- formed and the smaller the change in pH

Question 39

In respiratory acidosis, the greater the [Buff-], the _____ HCO₃^- is formed and the _____ the change in pH

Answer 39

In respiratory acidosis, the greater the [Buff-], the more HCO₃^- is formed and the smaller the change in pH

Question 40

In respiratory alkalosis, hyperventilation ________

Answer 40

In respiratory alkalosis, hyperventilation decreases PCO₂ and [HCO₃^-]

Question 41

Describe the effect of nonbicarbonate buffers in respiratory alkalosis

Answer 41

1. Decrease in H⁺
2. Nonbicarbonate buffers contribute H⁺
3. Increase in pH is reduced but additional reduction of HCO₃^- is promoted
4. {HCO₃^-] is reduced

The greater the [HBuff], the more HCO₃^- is reduced

Question 42

In respiratory alkalosis, the greater the [HBuff], the _____ HCO₃^- is reduced

Answer 42

In respiratory alkalosis, the greater the [HBuff], the more HCO₃^- is reduced

Question 43

Question

Answer 43

Horizontal line

[HCO3-] is in units of mM while [H+] is in units of nM, so the buffer line appears to be horizontal

Question 44

Increasing CO₂ shifts the bicarbonate buffer reaction in favor of _________

Answer 44

Increasing CO₂ shifts the bicarbonate buffer reaction in favor of producing H⁺ and HCO₃^- in equal amounts

BUT [HCO₃^-] is in units of mM on graph while ∆[HCO₃^-] is in units of nM, so the buffer line appears to be horizontal