integrated control of breathing

Question 1

What happens in the event of a change in respiratory function caused by a change in pH?

Answer 1

Respiratory acidosis
OR
Respiratory alkalosis

Either of the 2 above will occur in the event of pH change UNLESS [HCO3-] changes are in proportion with PaCO2

Question 2

Does hypoventilation lead to acidosis or alkalosis?

Answer 2

Respiratory acidosis

Question 3

Does hyperventilation lead to acidosis or alkalosis?

Answer 3

Respiratory alkalosis

Question 4

How does respiratory acidosis occur in the event of hypoventilation?

Answer 4

In the event of hypoventilation, there is a decreased ventilation/ exchange rate. This increases PACO2, which increases PaCO2, which results in hypercapnia. This increases H+ concentration in the blood, which decreases the pH (acidosis).
The body’s chemoreceptors detect both the increased PACO2 and the decreased pH. They then signal to increase the respiratory rate to counterbalance this.

Question 5

In the event of chronic hypoventilation, what must be done in order to maintain normal pH?

Answer 5

In the event of chronic hypoventilation, HCO3- excretion must decrease in order to maintain normal pH

Question 6

What causes hypoventilation?

Answer 6

Airway obstruction:
• Asphyxia
• Choking
• Obstructive sleep apnoea
• Increased airway resistance (asthma OR COPD)
Problems with initiation of breathing:
• Drug overdose (opioids) affecting the brainstem
• Neuromuscular problems (motor neuron disease OR respiratory muscle wasting)
Stroke

Question 7

How does respiratory alkalosis occur in the event of hyperventilation?

Answer 7

In the event of hyperventilation, there is an increased ventilation rate. This decreases PACO2, which decreases PaCO2, resulting in hypocapnia. This decreases the H+ concentration in the blood, which increases the pH (alkalosis).
The body’s chemoreceptors detect the decreased PACO2 and the increased pH. They then signal to decrease the respiratory rate to counterbalance this.

Question 8

Describe how anxiety can lead to hyperventilation

Answer 8

1. Anxiety trigger can result in a panic attack
   
   2. This increases ventilation (tachypnoea) without increased metabolic demand
   3. Hyperventilation decreases PaCO2
2. Results in respiratory alkalosis

Question 9

How can high altitude result in hyperventilation?

Answer 9

1. High altitude
   
   2. Increase in alveolar ventilation to maintain PAO2 and PaO2 (via hypoxic drive)
   3. Increases ventilation = decreases PaCO2
2. Results in respiratory alkalosis

Question 10

What causes metabolic acidosis?

Answer 10

Decreased absorption of HCO3-
OR
Increased excretion of HCO3-
• Unless PaCO2 changes in proportion with [HCO3-] acidosis (decreased pH) will occur
• Respiratory compensation usually occurs almost instantly, HOWEVER, it may not be sufficient to prevent disturbance in pH-
Ventilation increases

Question 11

What conditions can cause increased acid levels or decreased HCO3- within the body?

Answer 11

1. Lactic acidosis (sepsis)
   
   2. Lactic acidosis (exercise)
   3. Diabetic ketoacidosis
   4. Diarrhea
2. Renal failure

Question 12

Describe lactic acidosis caused sepsis

Answer 12

• Infection leads to a pathological immune response
  
  • This can cause a septic shock
  • Decreases oxygen delivery to tissues (hypoxia)
  • Increases lactic acid production and decreases pH
  • Respiratory compensation to increase oxygen delivery and increase lactic conversion

Question 13

Lactic acidosis can result in metabolic acidosis. Name 3 other causes of metabolic acidosis and describe them in detail

Answer 13

1. Diabetic ketoacidosis
   Increased fatty acid release from liver due to insulin deficiency = increased acidic ketone body production
   
   2. Renal failure
      Decreased HCO3- reabsorption in proximal tubule
   3. Diarrhea
      Decreased HCO3- absorption in colon

Question 14

What causes metabolic alkalosis?

Answer 14

Excessive metabolic acid excretion OR excess HCO3-
Increased absorption of HCO3-
OR
Decreased excretion of HCO3-
• Unless PaCO2 changes in proportion with [HCO3-], alkalosis will occur
• Respiratory compensation typically occurs almost instantly, HOWEVER, it may not be sufficient enough to prevent disturbance in pH

Question 15

What can cause decreased acid levels or increased HCO3- within the body?

Answer 15

1. Diuretics 
	Changes to H+ and HCO3- reabsorption 
	2. Antacids 
	Increases HCO3- consumption 
	3. Vomiting 
Loss of H+ in stomach acid