Control of breathing-asleep Flashcards
what is apnoea?
The cessation of breathing
What is apnoeic threshold?
The level of blood gas you need to maintain breathing
what is the difference between sleep and other forms such as coma?
Sleep is reversible
How do we measure sleep?
Using a Electroencephalogram (EEG)
what stage of sleep makes you feel better?
Stage 4 which is deep sleep, this is what makes you feel better and restored
what stage do you dream and describe how this stage changes as you go through the night>
In your REM sleep. Deep sleep decreases and the amount of REM sleep increases.
The body becomes functionally paralysed during REM sleep. What two muscles are spared? What implications does this have for breathing?
Eye muscles
Diaphragm
The accessory muscles (e.g. intercostals) are no longer active so it becomes more difficult to breathe
What centre controls breathing and where is it located?
Respiratory Centre - medulla
How does the control of breathing change when asleep compared to when awake?
When asleep, cortical and emotional control of breathing is inactive. It is solely regulated by the respiratory centre.
what are the 2 ways in which breathing during sleep is controlled?
Brainstem: reflex/automatic
Cortex: Voluntary/ behavioural
how is the breathing when your sleeping controlled?
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.
Name a complex in the medulla that is involved in regulating the respiratory rhythm.
Pre-Botzinger Complex.
It is a cluster of respiratory nuclei found on the rostral-ventral-lateral medullary surface.
What models are used to determine certain neuronal control pathways?
Lesion Deficit Models.
This is using patients who have had bleeds in different parts of the brain
why does blood gases change ?
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.
How do minute ventilation and tidal volume change when asleep?
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.
What plays the biggest role in the control of breathing when awake?
PCO2 levels
How does oxygen saturation change when asleep? Explain your answer.
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
Why might this be different for someone with lung disease?
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.
How do carbon dioxide levels change when you go to sleep?
Carbon dioxide levels rise when you go to sleep.
How does the level of carbon dioxide required to trigger breathing change when you go to sleep?
INCREASES - a higher PCO2 is required to trigger breathing
How does sensitivity to carbon dioxide change when you go to sleep?
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.
What is the apnoeic threshold?
The minimum PCO2 required to trigger breathing
Suggest why becoming less sensitive to CO2 might be beneficial?
It gives us more blood gas range before we wake ourselves up
What happens if you prevent the carbon dioxide levels from exceeding the apnoeic threshold?
You stop breathing
what is central sleep apnoea also known as and what is it and what is it also called?
When the person is asleep they are not breathing.
-It is also known as Congenital central hypo-ventilation syndrome (CCHS)
Describe the structure of the upper airways (pharynx).
It is a muscular collapsible tube with no cartilage rings holding it open.
Describe the structure of the muscles involved in breathing relating to the upper airways?
- 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.
what happens to the muscles near the upper airways during sleep?
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
What makes the airway get sucked ?
If we produce negative pressure at the back of the throat, this makes the floppy airway get sucked closed during inspiration.
how is being fat creating difficulty during breathing?
-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.
Describe what causes obstructive sleep apnoea.
-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.
How does central sleep apnoea differ from obstructive sleep apnoea?
This is a chemosensitivity issue rather than a mechanical obstruction and this is very rare.
What are the implications of sleep apnoea on heart disease?
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.
what happens in Obstructive sleep apnea?
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.
How can the breathing response be measured?
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.
what are the 3 types of breathlessness?
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.
