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Module 9 > Respiratory Acid-Base Balance > Flashcards

Respiratory Acid-Base Balance Flashcards

1
Q

what occurs when CO2 dissolves in an aqeous solution

A

CO2 is gaseous acid

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2
Q

what are pH buffers

A

that reversibly bind H+

blood pH is a measure of H+ that are not bound to buffers

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3
Q

what is the most important buffer system in the blood

A

interaction between CO2 and HCO3

there is a large amount of bicarb in the blood (24mM/L)

reactions are reversible so dependent on what’s on each side of equation

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4
Q

how does hemoglobin buffer pH

A

through imidazole groups

H+ ions will bind

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5
Q

what are intracellular buffers

A

when inside the cell, H+ buffered by amino acids, peptides, proteins and organic phosphates

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6
Q

how do intracellular buffers work

A

when intracellular H+ increases

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7
Q

what mechanisms ultimately correct the H+ load

A

lungs and kidneys

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8
Q

how can arterial pH be measured

A

by using henderson-hasselbalch equation

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9
Q

what is pH

A

negative Log of [H+]

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10
Q

what is the henderson-hasselbalch equation

A

when HCO3- is constant, increases in PCO2 cause decrease in pH

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11
Q

how does hypoventilation change PCO2 and alter pH

A
  • PaCO2 increases
  • leads to hypercapnia
  • acidosis (lowers pH)
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12
Q

how does hyperventilation change PCO2 and alter pH

A
  • PaCO2 decreases
  • leads to hypocapnia
  • alkalosis (increase in pH)
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13
Q

what is the davenport diagram

A

as PCO2 increases or decreases the changes in pH and bicarbonate concentration are predicted by the normal buffer line

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14
Q

how can H+ ions be eliminated

A

kindey is the only route

H+ excretion occurs in the PCT and is coupled to reabsorption of HCO3-

H+ secreted into the tubular lumen in exchange for Na+

Na+ and HCO3- are reabsorbed

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15
Q

what are primary problems in acid-base distribution (2)

A
  1. excessive accumulation or elimanation of CO2 (resp. abnormalities)
  2. excessive accumulation or elimination of fixed acids or buffer bases (metabolic abnormalities)
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16
Q

what is resp acidosis

A
  1. breathing is suppressed holding CO2 in body –> pH decreases, PCO2 increases, HCO3- no change
  2. the kidneys conserve HCO3- ions and eliminate H+ ions in acidic urine
  3. or lactate solution used in therapy converted to bicarbonate ions in the liver
17
Q

what is metabolic acidosis

A
  1. metabolic acidosis HCO3- decreases because of excess presence of ketones, chloride or organic acid ions. pH decreases, PCO2 no change, HCO3- decreases
  2. body compensation: hyperactive breathing to blow off CO2 + kidneys conserve HCO3- and eliminate H+ ions in acidic urine
  3. lactate solution used converted to bicarbonate ions in liver
18
Q

what are the causes of respiratory acidosis

A
  1. CNS depression
  2. Resp muscle paralysis/diaphragm paralysis, rib fractures
  3. obstructive lung diseases (emphysema)
  4. pulmonary edema
19
Q

how does the body compensate resp acidosis

A
  1. carbonic acid excess caused by blood levels of CO2 above 45 mmHg
  2. kidneys eliminate hydrogen ion and retain bicarbonate ion
  3. kidney also generates new bicarbonate
20
Q

what are the causes of metabolic acidosis

A
  1. bicarbonate deficit: blood conc. of HCO3- drops below 22mEq/L
  2. diabetic ketoacidosis
  3. severe diarrhea (loss of HCO3-)
  4. hypoaldosteronism
  5. acute renal failure (fail to excrete H+)
  6. accumulation of acids
21
Q

how does the body compensate for metabolic acidosis

A
  1. increased ventilation
  2. renal excretion of hydrogen ions if possible
  3. K+ exchanges with excess H+ on ECF (H+ into cells, K+ out of cells)
22
Q

what are the causes of resp alkalosis

A

carbonic acid deficit: pCO2 is <35mmHg (hypocapnia)

  1. hyperventilation
  2. high altitude (oxygen deficiency)
  3. hysterical
  4. anorexia nervosa
  5. early salicylate intoxication
23
Q

how does the body compensate for resp alkalosis

A
  1. conditions that stimulate resp centre and wash out CO2 (hyperventilation)
  2. kidneys conserve+ ion
  3. excrete bicarbonate ion
24
Q

what are the causes of metabolic alkalosis

A

blood conc. of HCO3 is > 26mEq/L

  1. severe vomiting = loss of stomach acid or heavy ingestion of antacids
  2. severe dehydration
  3. excess antacids & alkaline drugs
  4. hyperaldosteronism (endocrine disorders)
25
Q

how does the body compensate metabolic alkalosis

A
  1. kidney excretes alkaline urine and retain H+
  2. respiratory compensation difficult (hypoventilation limited by hypoxia)
26
Q

how do acid base disturbances affect distribution of K+

A

decrease in pH = increase in [K+] (hyperkalemia)

increase in pH = decrease in [K+] (hypokalemia)

27
Q

what does hypokalemia lead to

A

increase in H+ elimination

28
Q

what does Cl- depletion occur

A

can maintain metabolic alkalosis (ex. after vomiting has stopped) because of absence of Cl-, kidney must reabsorb HCO3- with Na+ (electroneutrality)

Module 9 (43 decks)

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