Acid-Base Homeostasis- Respiratory

Question 1

How do you calculate pH of blood?

Answer 1

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

Question 2

What is pKa?

Answer 2

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

Question 3

What is the breakdown of carbonic acid reaction?

Answer 3

H2CO3 HCO3- + H

Question 4

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

Answer 4

Driven to the left

Question 5

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

Answer 5

Equation is driven to the right

Question 6

what is the pKa for carbonic acid/bicarbonate?

Answer 6

6.1

Question 7

What is the normal pH of blood?

Answer 7

7.4

Question 8

How can the absolute levels of bicarbonate change?

Answer 8

Changed by changes in breathing

Question 9

What does increased CO2 do?

Answer 9

Increases levels of carbonic acid

Question 10

What do respiratory acid-base disturbances change?

Answer 10

CO2 and water levels

Question 11

What do metabolic acid-base disturbances change?

Answer 11

Hydrogen ions and bicarbonate

Question 12

What is considered acidosis?

Answer 12

pH less than 7.35

Question 13

What is considered alkalosis?

Answer 13

pH greater than 7.45

Question 14

What can cause acid-base disturbances?

Answer 14

Increased and decreased CO2

Increased non-volatile acid/decreased base

Increased base/decreased non-volatile acid

Question 15

What can an acidosis be caused by?

Answer 15

Rise in PCO2

Fall in HCO3

Question 16

What can an alkalosis be caused by?

Answer 16

Fall in PCO2

Rise in HCO3

Question 17

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

Answer 17

Alters ventilation

Happens quickly

Question 18

How does the kidneys change any acid-base disturbances?

Answer 18

Alter excretion of bicarbonate

2-3 days

Question 19

What causes respiratory acidosis?

Answer 19

Hypoventilation

Ventilation perfusion mismatch

Question 20

What are the causes of respiratory acidosis?

Answer 20

COPD

Blocked airway

Lung collapse

Injury to chest wall

Drugs reducing respiratory drive- morphine, barbiturates, general anaesthetics

Question 21

What causes respiratory alkalosis?

Answer 21

Alveolar hyperventilation

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

Question 22

How does the kidneys compensate for respiratory alkalosis?

Answer 22

Reduce bicarbonate reabsorption and reduced bicarbonate production

Question 23

What pathophysiological causes of respiratory alkalosis?

Answer 23

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

Hyperventilation through brainstem damage, infection driving fever

Question 24

What causes metabolic acidosis?

Answer 24

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

Respiration is unaffected, therefore PCO2 is initially normal

Question 25

What is the respiratory compensation for metabolic acidosis?

Answer 25

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

Question 26

Can the respiratory system fix metabolic acidosis alone?

Answer 26

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

Question 27

What are the causes of metabolic acidosis?

Answer 27

Loss of bicarbonate from gut in diarrhoea Exogenous acid overloading (aspirin overdose), endogenous acid production(ketogenesis) Failure to secrete hydrogen ions, renal failure

Question 28

What are the pathophysiological causes of metabolic alkalosis?

Answer 28

Vomiting-loss of HCL from stomach Ingestion of alkali substance Potassium depletion (diuretics)

Question 29

What are the causes of metabolic alkalosis?

Answer 29

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

Question 30

What is the respiratory compensation to metabolic alkalosis?

Answer 30

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