11 Control of Breathing During Sleep

Question 1

What would EEG show when you’re awake and asleep and in REM sleep

Answer 1

Wakefulness and REM: low voltage, high frequency

Non-REM sleep: high voltage and low frequency

Question 2

Where is Pre-Botzinger Complex located

Answer 2

Rostral ventrolateral medulla

Question 3

Describe the change of ventilation and oxygen saturation during sleep

Answer 3

Minute ventilation reduced by 10%. This is a result of decreasing frequency by 10% and no change in tidal volume. This causes the oxygen saturation to drop by only about 1%.

Question 4

Describe the changes in PaCO2 during sleep

Answer 4

PaCO2 increases by 0.5 kPa to 7 kPa. This is due to reduced sensitivity to PaCO2

Question 5

Why does PaCO2 increase during sleep

Answer 5

This is so that the PaCO2 is above the apnoeic threshold which is increased during sleep to prevent central sleep apnoea.

Question 6

What is obstructive sleep apnoea

Answer 6

This is the obstruction of phalangeal airway due to reduced upper airway muscle activity and positive extraluminal pressure and negative intraluminal pressure

Question 7

What are the risk factors for obstructive sleep apnoea

Answer 7

Adipose tissues in the tongue and neck

Question 8

Describe the sleep cycle of a patient with obstructive sleep apnoea

Answer 8

Sleep -> decreased upper airway muscle tone -> apnoea (hypercapnia and hypoxia) -> arousal -> patent airway -> increase ventilation

Question 9

Differentiate between central sleep apnoea and obstructive sleep apnoea

Answer 9

Although both suffer cessation of breathing, but only patients with obstructive sleep apnoea will have thoracic and abdominal effort

Central: won’t breathe
Obstructive: can’t breathe

Question 10

What is the effect of COPD on breathing during sleep

Answer 10

Patients with COPD are living on the steep part of oxygen dissociation curve so even without central or obstructive sleep apnoea, they are dangerous as a small drop in inspired oxygen can result in a huge drop in oxygen saturation

Question 11

Describe the effect of heart failure on breathing during sleep

Answer 11

Heart failure causes pulmonary oedema which irritates J receptors in the lungs to cause the patients to hyperventilate. Therefore this causes a drop in PaCO2 during sleep and cause central sleep apnoea

Question 12

What are the muscles that are still active during REM sleep

Answer 12

Diaphragm and occular muscle

Question 13

What are the muscles involved in obstructive sleep apnoea

Answer 13

Tongue, levator palatini and tensor palatine