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Respiratory system > Disturbed acid-base balance > Flashcards

Disturbed acid-base balance Flashcards

1
Q

What is hyperventilation?

A

Increase in alveolar ventilation

without change in metabolism

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2
Q

How does hyperventilation affect alveolar pO2 and pCO2?

A

Alveolar pO2 increases because are inspiring more oxygen

Alveolar pCO2 decreases because are expiring more carbon dioxide

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3
Q

How does hyperventilation affect plasma pO2 and pCO2?

A

Plasma pO2 increases because more oxygen diffuses from alveoli into pulmonary capillaries

Plasma pCO2 decreases because more carbon dioxide diffuses from pulmonary capillaries to alveoli

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4
Q

What is hypoventilation?

A

Decrease in alveolar ventilation

without change in metabolism

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5
Q

How does hypoventilation affect alveolar pO2 and pCO2?

A

Low alveolar pO2 because are inspiring less oxygen

High alveolar pCO2 because are expiring less carbon dioxide

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6
Q

How does hypoventilation affect plasma pO2 and pCO2?

A

Low plasma pO2 because less oxygen diffusing into pulmonary capillaries from alveoli, hypoxia

High plasma pCO2 because less carbon dioxide diffusing from pulmonary capillaries into alveoli

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7
Q

What is hypercapnia?

A

Increase in plasma pCO2 above normal range

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8
Q

How does hypercapnia affect plasma pH?

A

Higher concentration of carbon dioxide dissolved in the blood
favours forwards bicarbonate buffer reaction
increases concentration of hydrogen ions
decrease in plasma pH

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9
Q

What is hypocapnia?

A

Decrease in plasma pCO2 below normal range

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10
Q

How does hypocapnia affect plasma pH?

A

Lower concentration of carbon dioxide dissolved in the blood
favours backwards bicarbonate buffer reaction
reduces concentration of hydrogen ions
increase in plasma pH

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11
Q

What is respiratory acidosis?

A

Hypoventilation
gives hypercapnia
gives decrease in plasma pH

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12
Q

What are the relative levels of the following in respiratory acidosis

  • plasma pCO2
  • plasma bicarbonate ion concentration
  • plasma pH
A

plasma pCO2 - high

plasma bicarbonate ion concentration - normal

plasma pH - low

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13
Q

What is meant by compensating for respiratory acidosis?

A

Kidneys increase their reabsorption and production of bicarbonate ions
to increase the plasma bicarbonate ion concentration

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14
Q

How does increasing plasma bicarbonate ion concentration compensate for respiratory acidosis?

A

Stops the forwards bicarbonate buffer reaction from being favoured
plasma pH returns to normal

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15
Q

How long does it take for the kidneys to increase plasma bicarbonate ion concentration to compensate for respiratory acidosis?

A

2-3 days

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16
Q

What is the similarity between fully compensated and partially compensated respiratory acidosis?

A

plasma pCO2 - high

plasma bicarbionate ion concentration - higher

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17
Q

What is the difference between fully compensated and partially compensated respiratory acidosis?

A

Fully compensated respiratory acidosis
plasma pH - normal

Partially compensated respiratory acidosis
plasma pH - low

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18
Q

What is respiratory alkalosis?

A

Hyperventilation
gives hypocapnia
gives increase in plasma pH

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19
Q

What are the relative levels of the following in respiratory alkalosis

  • plasma pCO2
  • plasma bicarbonate ion concentration
  • plasma pH
A

plasma pCO2 - low

plasma bicarbonate ion concentration - normal

plasma pH - high

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20
Q

What is meant by compensating for respiratory alkalosis?

A

Kidneys decrease their reabsorption and production of bicarbonate ions
to decrease the plasma bicarbonate ion concentration

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21
Q

How does decreasing plasma bicarbonate ion concentration compensate for respiratory alkalosis?

A

Stops backwards bicarbonate buffer reaction being favoured

pH returns to normal

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22
Q

How long does it take for the kidneys to decrease plasma bicarbonate ion concentration to compensate for respiratory alkalosis?

A

2-3 days

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23
Q

What is the similarity between partially compensated and fully compensated respiratory alkalosis?

A

plasma pCO2 - low

plasma bicarbonate ion concentration - lower

24
Q

What is the difference between partially compensated and fully compensated respiratory alkalosis?

A

Fully compensated respiratory alkalosis
plasma pH - normal

Partially compensated respiratory alkalosis
plasma pH - high

25
Q

What is meant by the anion gap?

A

Difference between measured cations and anions

26
Q

Which cations are measured?

A

Sodium ions

Potassium ions

27
Q

Which anions are measured?

A

Chloride ions

Bicarbonate ions

28
Q

What is the equation for the anion gap?

A

Anion gap = (sodium ion concentration + potassium ion concentration) - (chloride ion concentration + bicarbonate concentration)

29
Q

Why is there an anion gap in the first place?

A

Because there are other anions

which are not measured

30
Q

What are the causes of metabolic acidosis?

A

Tissue metabolism produces more acid

Kidneys don’t excrete enough hydrogen ions
Kidneys don’t reabsorb or produce enough bicarbonate ions

Severe diarrhoea gives loss of bicarbonate ions from the GI tract

31
Q

What can cause tissue metabolism to produce more acid?

A

Lactic acidosis - intense exercise, decreased perfusion of tissues

Ketoacidosis - diabetes

32
Q

How does the kidneys not excreting enough hydrogen ions cause metabolic acidosis?

A

Higher concentration of hydrogen ions in plasma

decrease in plasma pH

33
Q

How does the kidneys not reabsorbing or producing bicarbonate ions and severe diarrhoea causing loss of bicarbonate ions from the GI tract give metabolic acidosis?

A

Decrease in plasma bicarbonate ion concentration
favours forwards bicarbonate buffer reaction
increased concentration of hydrogen ions
decreases plasma pH

34
Q

What are the relative levels of the following in metabolic acidosis

  • plasma pCO2
  • plasma bicarbonate ion concentration
  • plasma pH
A

plasma pCO2 - normal

plasma bicarbonate ion concentration - low

plasma pH - low

35
Q

How does metabolic acidosis caused by tissue metabolism producing more acid and kidneys not secreting hydrogen ions cause a decrease in the plasma bicarbonate ion concentration?

A

Because increased concentration of hydrogen ions favours backwards bicarbonate buffer reaction
bicarbonate ions react with hydrogen ions
decrease in bicarbonate ion concentration

36
Q

How does metabolic acidosis caused by tissue metabolism producing more acid affect the anion gap? Why?

A

Anion gap is bigger
because bicarbonate ion concentration decreases
replaced with anion of acid which is not measured

37
Q

How does metabolic acidosis caused by the kidneys not secreting enough hydrogen ions affect the anion gap? Why?

A

Anion gap is bigger
because bicarbonate ion concentration decreases
replaced with anion of acid which is not measured

38
Q

How does metabolic acidosis caused by the kidneys not reabsorbing enough bicarbonate ions affect the anion gap? Why?

A

Anion gap remains the same

because the bicarbonate ions are replaced with chloride ions, which is a measured anion

39
Q

How does metabolic acidosis caused by severe diarrhoea giving loss of bicarbonate ions through the GI tract affect the anion gap? Why?

A

Anion gap remains the same

because the bicarbonate ions are replaced with chloride ions, which is a measured anion

40
Q

What is meant by compensating for metabolic acidosis?

A

Peripheral chemoreceptors detect decrease in plasma pH
stimulate increased alveolar ventilation
to decrease plasma pCO2

41
Q

How does decreasing plasma pCO2 compensate for metabolic acidosis caused by tissue metabolism producing more acid or kidneys not excreting enough hydrogen ions?

A

Removes extra carbon dioxide in the plasma produced from backwards bicarbonate buffer reaction being favoured

42
Q

How does decreasing plasma pCO2 compensate for metabolic acidosis caused by kidneys not reabsorbing or producing enough bicarbonate ions and severe diarrhoea causing loss of bicarbonate ions from GI tract?

A

Carbon dioxide concentration in plasma decreases
prevents forwards bicarbonate buffer reaction being favoured
plasma pH returns to normal

43
Q

What is the similarity between partially compensated and fully compensated metabolic acidosis?

A

plasma bicarbonate ion concentration - low

plasma pCO2 - low

44
Q

What is the difference between partially compensated and fully compensated metabolic acidosis?

A

Fully compensated metabolic acidosis
plasma pH - normal

Partially compensated metabolic acidosis
plasma pH - low

45
Q

What are the causes of metabolic alkalosis?

A

Tissue metabolism produces less acid

Severe vomiting causes loss of hydrogen ions from stomach

46
Q

What are the relative levels of the following in metabolic alkalosis

  • plasma pCO2
  • plasma bicarbonate ion concentration
  • plasma pH
A

plasma pCO2 - normal

plasma bicarbonate ion concentration - high

plasma pH - high

47
Q

Why is the plasma bicarbonate ion concentration high with metabolic alkalosis?

A

Fewer bicarbonate ions react

increased bicarbonate ion concentration

48
Q

What is meant by compensating for metabolic alkalosis?

A

Peripheral chemoreceptors detect increase in plasma pH
stimulate decreased alveolar ventilation
to increase plasma pCO2

Kidneys secrete fewer hydrogen ions and reabsorb fewer bicarbonate ions

49
Q

How does increasing plasma pCO2 compensate for metabolic alkalosis?

A

Increase plasma carbon dioxide concentration
stops backwards bicarbonate buffer reaction being favoured
pH returns to normal

50
Q

How does the kidneys secreting fewer hydrogen ions and reabsorbing fewer bicarbonate ions compensate for metabolic alkalosis?

A

Decreased concentration of bicarbonate ions in plasma

pH returns to normal

51
Q

How effective are the kidneys in compensating for metabolic alkalosis caused by severe vomiting losing hydrogen ions from the stomach?

A

Usually effective
but in cases of hypotension, hypovolaemia
kidneys increase reabsorption of sodium ions, water
this increases secretion of hydrogen ions by NHE, and reabsorption of bicarbonate ions

52
Q

How effective is decreased alveolar ventilation in compensating for metabolic alkalosis Why?

A

Not very effective
because cannot decrease alveolar ventilation very much
because plasma pO2 would decrease below normal range giving hypoxia

53
Q

What are the consequences of acidaemia?

A

Proteins denature

Hyperkalaemia

54
Q

What are the consequences of alkalaemia?

A

Tetany

Hypokalaemia

55
Q

How does alkalaemia cause tetany?

A

Calcium ions leave solution, bind to proteins
lower concentration of calcium ions in plasma
increases neuronal excitability
at neuromuscular junctions, this gives tetany

56
Q

What is the relationship between disturbances in acid-base balance and disturbances in plasma potassium ion concentration?

A

Acidosis causes hyperkalaemia
Hyperkalaemia causes acidosis

Alkalosis causes hypokalaemia
Hypokalaemia causes alkalosis

57
Q

What is the exception to acidosis causing hyperkalaemia?

A

Type 1 diabetes ketoacidosis
acidosis and lack of insulin causes more potassium ions to move out of cells into blood
but then diuresis by kidneys causes loss of potassium ions
giving hypokalaemia

Respiratory system (32 decks)

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