Control of breathing-asleep

Question 1

what is apnoea?

Answer 1

The cessation of breathing

Question 2

What is apnoeic threshold?

Answer 2

The level of blood gas you need to maintain breathing

Question 3

what is the difference between sleep and other forms such as coma?

Answer 3

Sleep is reversible

Question 4

How do we measure sleep?

Answer 4

Using a Electroencephalogram (EEG)

Question 5

what stage of sleep makes you feel better?

Answer 5

Stage 4 which is deep sleep, this is what makes you feel better and restored

Question 6

what stage do you dream and describe how this stage changes as you go through the night>

Answer 6

In your REM sleep. Deep sleep decreases and the amount of REM sleep increases.

Question 7

The body becomes functionally paralysed during REM sleep. What two muscles are spared? What implications does this have for breathing?

Answer 7

Eye muscles
Diaphragm
The accessory muscles (e.g. intercostals) are no longer active so it becomes more difficult to breathe

Question 8

What centre controls breathing and where is it located?

Answer 8

Respiratory Centre - medulla

Question 9

How does the control of breathing change when asleep compared to when awake?

Answer 9

When asleep, cortical and emotional control of breathing is inactive. It is solely regulated by the respiratory centre.

Question 10

what are the 2 ways in which breathing during sleep is controlled?

Answer 10

Brainstem: reflex/automatic
Cortex: Voluntary/ behavioural

Question 11

how is the breathing when your sleeping controlled?

Answer 11

There is NO corticol control when you’re sleeping. Most of the time there is some input from the cortex unless you’re in deep sleep.

Question 12

Name a complex in the medulla that is involved in regulating the respiratory rhythm.

Answer 12

Pre-Botzinger Complex.

It is a cluster of respiratory nuclei found on the rostral-ventral-lateral medullary surface.

Question 13

What models are used to determine certain neuronal control pathways?

Answer 13

Lesion Deficit Models.

This is using patients who have had bleeds in different parts of the brain

Question 14

why does blood gases change ?

Answer 14

Because there is less input from the respiratory centres and so you have less output to the respiratory muscles. As a result, blood gases change when you go to sleep.

Question 15

How do minute ventilation and tidal volume change when asleep?

Answer 15

Minute Ventilation = DECREASES (10% reduction in minute ventilation) 
Tidal Volume = DECREASES 
NOTE: frequency remains roughly the same
Breathing becomes shallower.
Little change in oxygen saturation.

Question 16

What plays the biggest role in the control of breathing when awake?

Answer 16

PCO2 levels

Question 17

How does oxygen saturation change when asleep? Explain your answer.

Answer 17

Oxygen saturation remains the same - because you are at the flat part of the oxygen dissociation curve meaning that despite a decrease in PO2, oxygen saturation stays the same.
NOTE: During REM sleep, you PO2 and SO2 drop slightly

Question 18

Why might this be different for someone with lung disease?

Answer 18

People with lung disease live on the steeper part of the ODC so a reduction in PO2 during sleep can cause a marked reduction in oxygen saturation.

Question 19

How do carbon dioxide levels change when you go to sleep?

Answer 19

Carbon dioxide levels rise when you go to sleep.

Question 20

How does the level of carbon dioxide required to trigger breathing change when you go to sleep?

Answer 20

INCREASES - a higher PCO2 is required to trigger breathing

Question 21

How does sensitivity to carbon dioxide change when you go to sleep?

Answer 21

Sensitivity to carbon dioxide decreases when you go to sleep - there is a smaller change in minute ventilation per 1 kPa rise in PCO2. This allows CO2 levels to rise when we sleep.

Question 22

What is the apnoeic threshold?

Answer 22

The minimum PCO2 required to trigger breathing

Question 23

Suggest why becoming less sensitive to CO2 might be beneficial?

Answer 23

It gives us more blood gas range before we wake ourselves up

Question 24

What happens if you prevent the carbon dioxide levels from exceeding the apnoeic threshold?

Answer 24

You stop breathing

Question 25

what is central sleep apnoea also known as and what is it and what is it also called?

Answer 25

When the person is asleep they are not breathing.

-It is also known as Congenital central hypo-ventilation syndrome (CCHS)

Question 26

Describe the structure of the upper airways (pharynx).

Answer 26

It is a muscular collapsible tube with no cartilage rings holding it open.

Question 27

Describe the structure of the muscles involved in breathing relating to the upper airways?

Answer 27

• The bit at the back of the throat is a muscular tube.
• at the front you have the tongue and you have the pharyngeal constrictor muscles around the back- the airway at this point is a muscular tube.
• No cartilage until you get to the larynx
• muscular tube is distensible so it is good for swallowing but bad to breathe through.

Question 28

what happens to the muscles near the upper airways during sleep?

Answer 28

When you’re asleep, your muscles relax and thus applies to the muscles at the back of your throat, instead of being open and rigid, they are floppy.q

Question 29

What makes the airway get sucked ?

Answer 29

If we produce negative pressure at the back of the throat, this makes the floppy airway get sucked closed during inspiration.

Question 30

how is being fat creating difficulty during breathing?

Answer 30

-when you’re asleep there is negative intraluminal pressure (ILP) and positive extraluminal pressure (ELP) pressing down on the muscular tube.
If you are Fat around the neck, then you have even more extraluminal pressure.

Question 31

Describe what causes obstructive sleep apnoea.

Answer 31

-fall asleep and lose muscle function (esp in the upper airways)
- once lost, you stop breathing
-this has nothing to do with respiratory control- there is a mechanical obstruction preventing breathing
- so O2 fall and CO2 increase.
-the hypoxia or hypercapnia will wake you up.
Relaxation of the muscular parts of the upper airways, negative intraluminal pressure and positive extraluminal pressure can lead to collapse of the airways.

Question 32

How does central sleep apnoea differ from obstructive sleep apnoea?

Answer 32

This is a chemosensitivity issue rather than a mechanical obstruction and this is very rare.

Question 33

What are the implications of sleep apnoea on heart disease?

Answer 33

Patients with sleep apnoea have to generate massive pressures in their chest to allow them to breathe and this can exacerbate heart conditions. It will cause them to get more pulmonary oedema which exacerbates hyperventilation and difficulty breathing.

Question 34

what happens in Obstructive sleep apnea?

Answer 34

They will have a continuous cycle of breathing and then not breathing and then breathing again. These patients will be tired throughout the day because they have disrupted sleep.

Question 35

How can the breathing response be measured?

Answer 35

To distinguish between a reduced response that may be central in origin (‘won’t breathe) or peripheral (‘cannot breathe’) and these can be distinguished by measuring mouth occlusion pressure or diaphragm EMG during CO2 stimulation.

Question 36

what are the 3 types of breathlessness?

Answer 36

Tightness: difficulty in expanding the thorax, generally associated with airway narrowing
Increased work and effort: either the hyperventilation of exercise, or breathing against increased external resistance or at high end-expired volume.
Air hunger: describes a powerful urge to breathe such as at the end of a prolonged breath hold.