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MD3001 Week 8 > Acid-Base Homeostasis- Respiratory > Flashcards

Acid-Base Homeostasis- Respiratory Flashcards

1
Q

How do you calculate pH of blood?

A

pKa + log(conc of bicarbonate/ conc of CO2)

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2
Q

What is pKa?

A

Defined as the pH at which 50% is ionised and 50% is unionised in the reaction

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3
Q

What is the breakdown of carbonic acid reaction?

A

H2CO3 HCO3- + H

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4
Q

How does the breakdown of carbonic acid reaction change if hydrogen ions rise?

A

Driven to the left

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5
Q

How does the breakdown of carbonic acid reaction change if hydrogen ions falls?

A

Equation is driven to the right

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6
Q

what is the pKa for carbonic acid/bicarbonate?

A

6.1

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7
Q

What is the normal pH of blood?

A

7.4

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8
Q

How can the absolute levels of bicarbonate change?

A

Changed by changes in breathing

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9
Q

What does increased CO2 do?

A

Increases levels of carbonic acid

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10
Q

What do respiratory acid-base disturbances change?

A

CO2 and water levels

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11
Q

What do metabolic acid-base disturbances change?

A

Hydrogen ions and bicarbonate

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12
Q

What is considered acidosis?

A

pH less than 7.35

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13
Q

What is considered alkalosis?

A

pH greater than 7.45

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14
Q

What can cause acid-base disturbances?

A

Increased and decreased CO2

Increased non-volatile acid/decreased base

Increased base/decreased non-volatile acid

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15
Q

What can an acidosis be caused by?

A

Rise in PCO2

Fall in HCO3

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16
Q

What can an alkalosis be caused by?

A

Fall in PCO2

Rise in HCO3

17
Q

How does the respiratory system change any acid-base disturbances?

A

Alters ventilation

Happens quickly

18
Q

How does the kidneys change any acid-base disturbances?

A

Alter excretion of bicarbonate

2-3 days

19
Q

What causes respiratory acidosis?

A

Hypoventilation

Ventilation perfusion mismatch

20
Q

What are the causes of respiratory acidosis?

A

COPD

Blocked airway

Lung collapse

Injury to chest wall

Drugs reducing respiratory drive- morphine, barbiturates, general anaesthetics

21
Q

What causes respiratory alkalosis?

A

Alveolar hyperventilation

Causes a decrease in hydrogen ion concentration and thus a rise in pH

22
Q

How does the kidneys compensate for respiratory alkalosis?

A

Reduce bicarbonate reabsorption and reduced bicarbonate production

23
Q

What pathophysiological causes of respiratory alkalosis?

A

Increased ventilation from hypoxic drive in pneumonia, diffuse interstitial lung diseases, high altitude, mechanical ventilation

Hyperventilation through brainstem damage, infection driving fever

24
Q

What causes metabolic acidosis?

A

Results from an excess of hydrogen ions in the body, which reduced bicarbonate levels

Respiration is unaffected, therefore PCO2 is initially normal

25
Q

What is the respiratory compensation for metabolic acidosis?

A

the lower pH is detected by peripheral chemoreceptors,
causes an increase in ventilation which lowers PCO2.
! Also, the bicarbonate equation is driven further to the left, lowering H+ and HCO3- concentration further! The decrease in H+ concentration moves pH towards normal

26
Q

Can the respiratory system fix metabolic acidosis alone?

A

No, has to have excess hydrogen ions or increased bicarbonate through renal system

27
Q

What are the causes of metabolic acidosis?

A

Loss of bicarbonate from gut in diarrhoea

Exogenous acid overloading (aspirin overdose), endogenous acid production(ketogenesis)

Failure to secrete hydrogen ions, renal failure

28
Q

What are the pathophysiological causes of metabolic alkalosis?

A

Vomiting-loss of HCL from stomach

Ingestion of alkali substance

Potassium depletion (diuretics)

29
Q

What are the causes of metabolic alkalosis?

A

Results form an increase in bicarbonate concentration or a fall in hydrogen ions

Removing hydrogen from equation drives reaction to right, increasing bicarbonate

Lowering of hydrogen ions raises pH with PCO2, initially being normal

30
Q

What is the respiratory compensation to metabolic alkalosis?

A

Increase in pH detected by peripheral chemoreceptors, decreases ventilation which raises PCO2

Respiratory compensation is often small or even absent- ventilation cannot reduce enough to correct imbalance

MD3001 Week 8 (7 decks)

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