Respiratory Centre Depression and Hypoventilation

Question 1

Where are central chemoreceptors and what do they respond to?

Answer 1

Medulla

Respond to PaCO2, via CSF H+

Question 2

Where are peripheral chemoreceptors and what do they respond to?

Answer 2

Carotid bodies

Respond to PaO2, PaCO2, pH

Question 3

What changes occur in ventilation in response to CO2 and O2?

Answer 3

If CO2 goes up we hyperventilate

No change occurs in ventilation until PaO2 is around 50-60mmHg - much less sensitive

Question 4

What are some causes of hypoventilation?

Answer 4

• Reduced respiratory centre activity
• Neuromuscular disease
• Chest wall deformity
• Obesity
• Sleep disordered breathing

Question 5

What is OSA?

Answer 5

Obstructive Sleep Apnoea

• transient obstruction of the throat during sleep preventing breathing and disturbing sleep
• occurs in people who snore

Question 6

What is the cycle of events in OSA?

Answer 6

1. Snoring in light sleep
2. Complete obstruction in deep sleep
3. Reduced blood O2, increased CO2
4. Brain “wakes” to lighter sleep (arousal)
5. Muscles contract, airways open, breathing recommences
6. Back into deep sleep, obstructs again