Integrated Control of Breathing

Question 1

How does the kidney compensate when hyperventilating?

Answer 1

PaCO2 is lowered, causing hypocapnia which results in RESPIRATORY alkalosis. If you really must hyperventilate, the kidney will need to excrete more HCO3- to keep the pH in balance.

Question 2

How does the kind compensate when hypoventilating?

Answer 2

PaCO2 is raised, causing hypercapnia which results in RESPIRATORY acidosis. If you really must hypoventilate, the kidney will need to retain more HCO3- to keep pH in balance.

Question 3

What is metabolic acidosis/alkalosis?

Answer 3

In metabolic acidosis, the body adds H+, so the lungs blow off more CO2, to shift the equilibrium to the left.
In metabolic alkalosis, the body loses H+, so the lungs try to retain CO2, so equilibrium shifts to right.

Question 4

What are the potential causes of metabolic acidosis?

Answer 4

• Lactic acidosis – Caused by exercise (including shivering) or sepsis (organ hypofusion due to low BP caused by sepsis vasodilation)
• Renal failure – Kidneys can’t do their part properly
• Diabetic ketoacidosis – When the liver starts to burn fatty acids for fuel
• Diarrhoea – Failure to reabsorb HCO3- released from pancreas

Question 5

What are the potential causes of metabolic alkalosis?

Answer 5

• Vomiting – Throwing up your acid, this needs to be excessive however
• Antacids – Neutralise acid, again this needs to be excessive
• Diuretics – Loop diuretics cause a loss of cations generally, including H+

Question 6

What happens to O2 and CO2 levels as altitude increases?

Answer 6

O2 levels drop but CO2 levels stay normal. When our PaO2 gets below 8kPa hypoxic drive kicks in.

Question 7

What happens when our hypoxic drive kicks in?

Answer 7

We start to breathe more, this causes us to blow off CO2 giving us alkalosis (which can be seen in the rise in O2, dip in CO2 and rise in pH).

Question 8

What happens when the central chemoreceptors detect that the CSF is too alkaline?

Answer 8

Respiratory rate drops, PaCO2 starts to rise again and PaO2 will drop. Eventually will reach a state where respiratory rate is relatively high. The kidneys kick in and start to increase HCO3- excretion to compensate for the decrease in CO2 (i.e. shift the equation to the right) due to increased ventilation.

Question 9

What is Cheyne-Stokes breathing?

Answer 9

It is the alternating of breathing rapidly and then having a period of where breathing stops. The breathing rapidly is caused by the peripheral chemoreceptors detecting low oxygen (so hypoxic drive) and then the central chemoreceptors start detecting that now the CSF is too alkaline so breathing stops.

Question 10

DON’T FORGET TO LOOK AT OTHER EXAMPLES IN NOTES

Answer 10

DON’T FORGET TO LOOK AT OTHER EXAMPLES IN NOTES