Respiratory Physiology during Sleep

Question 1

Name the three inputs of breathing

Answer 1

1. Reflex/Automatic
   
   1. Brainstem
2. Voluntary
   
   1. ​Motor Cortex
   2. Corticospinal Tracts
3. Emotional
   
   1. ​Limbic

Question 2

How do we know which aresa of the brain are involved in breathing? How does this work?

Answer 2

Functional MRI (fMRI)

Measures the magnetism of haem group. fMRI relies on the coupling of nerve activation and increased blood flow

It requires measurement of passive and active breathing to measure blood flow difference

Question 3

Through what tracts is a) voluntary b) automatic breathing controlled by.

Answer 3

Voluntary - corticospinal tracts

Automatic - bulbospinal

Question 4

Where is the respiratory control centre in mouse and humans?

Answer 4

Mouse: Pre-Botzinger Region

named after wine they drank over discovery lmao

Humans: Pre-Botzinger Region still not found in humans as highly developed pyramidal tracts (for fine control) probably pushes the complex out

Question 5

Where is the Pre-Botzinger Complex found and what is the significance of its location?

Answer 5

Ventrolateral medulla (rostral and ventral)

Near medulla surface so that it can sample CSF for pH

Question 6

What determines rate of breathing?

Answer 6

pH of CSF

Question 7

What is one proposed mechanism in which the pre-botzinger complex regulates breathing.

Answer 7

Reciprocal inhibition

Question 8

Describe the changes that occur in muscles/body when you sleep

Answer 8

Breathing rate is 10% less during sleep

Loss of voluntary control

Muscle relaxation

Hypercapnoea

Question 9

Why are we hypercapnoeic during sleep

Answer 9

We are less sensitive to CO2 whilst asleep

Therefore need a higher pCO2 to ensure there is ventilatory drive

Question 10

Other than an increase in CO2 during sleep, what other changes are then in breathing?

Answer 10

Decrease in tidal volume (as we go from awake to sleep state)

Question 11

Define the apnoeic threshold

Answer 11

The level of CO2 needed to ensure breathing continues during sleep

Question 12

What is Cheyne-Stokes breathing and describe the concept

Answer 12

Alternating state between apnoea and hyperventilation due to compensatory delay

Patient sleeping and normal breathing

Increase pCO2

Hyperventilation -> decrased pCO2

Goes below apnoeic threshold

Stops breathing

Increase pCO2

Question 13

Explain why more effort is needed to achieve same amount of ventilation in people who snore

Answer 13

When lying down, palatine muscle collapses

Airway is less patent

Increased pharyngeal resistance

More effort needed to achieve same amount of ventilation

Question 14

What types of sleep apnoea are there?

Answer 14

Obstructive Sleep Apnoea

Central Sleep Apnoea

Question 15

Describe a cycle of sleep apnoea

Answer 15

• Sleep
• ↓Upper airway muscle function
• OSA
  
  • hypoxia
  • hypercapnia
• Increased effort
• Arousal
  
  • Termination of apnoea
• Patent airway
• ↑ventilation
  
  • Hypocapnia
  • Decreased respiratory drive
  • CSA
• Sleep

Question 16

How do we manage sleep apnoea

Answer 16

CPAP

Keeps airways patent during sleep

Question 17

What factors affect susceptibilty to sleep apnoea

Answer 17

1. Anatomical compromise
2. Poor respiratory muscle responsiveness
3. Unstable respiratory control
4. Low Arousal threshold

Age

Question 18

What are the three drivers of breathing

Answer 18

Mechanical effort (muscles)

Chemosensitivity

Neuronal

Question 19

Describe the pathology of OSA

Answer 19