10- Control Of Breathing Asleep Flashcards
How does breathing change when you are asleep
• There is around a 10% reduction in ventilation
• Breathing becomes shallower - 350 mL rather than 500 mL
• There is little change in oxygen saturation
CO2 levels increase
Why does a reduction in ventilation during sleep not effect oxygen saturation
is because most normal people are living on the FLAT part of the ODC
What is R.E.M. sleep
You dream during REM sleep
• If you measure brain activity during REM sleep, it looks like you’re wide awake
• However, you are functionally paralysed during REM sleep (this has probably
evolved to stop you acting out your dreams)
• As you are functionally paralysed, there is more difficulty breathing
• The two muscles that are spared the functional paralysis are:
Eye Muscles (this is what causes the rapid eye movements)
Diaphragm (to allow you to breathe)
What are the 2 ways breathing is controlled
Brainstem - reflex/automatic Cortex - voluntary/behavioural
What is the cluster of resp nuclei called
Pre-Botzinger
Complex
Why may people with lung disease require o2 at night
If you have lung disease and you’re living on the steep part of the ODC, even going to sleep will be a challenge because it is going to decrease ventilation, decrease oxygen levels and increase carbon dioxide levels
• To compensate, it is sometimes recommended to increase oxygen levels at night
Why are we less sensitive to CO2 during sleep
If we are extremely sensitive to carbon dioxide, every time there is a slight change in carbon dioxide level our body would wake us up
• Therefore, it could be an adaptive system that allows us to maintain our brain in the sleeping state
What is central sleep apnoea
carbon dioxide doesnt exceed the
apnoeic threshold so when the person is asleep they are not breathing
Treat with ventilation at night
How is the upper airway badly designed for breathing
You do NOT get cartilage rings until you get to the larynx
• The muscular tube is distensible so it is good for swallowing but it relaxes during sleep
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 obstructive sleep apnoea
• Patients fall asleep and they lose muscle function (particularly in the upper airway)
• If you lose this muscle function, you stop breathing
oxygen levels fall and carbon dioxide levels increase
• Eventually, either the hypoxia or hypercapnia will wake you up
• Waking up allows them to clear their airways and the cycle starts again
What condition can sleep apnea exacerbate
• Patients with sleep apnoea generate massive pressures in the chest when they are trying to breathe which can exacerbate cardiac conditions
How can heart disease cause sleep apnoea
Pulmonary oedema, irritates J receptors, increased breathing rate, low CO2, so central sleep apnoea
How is COPD exacerbated during sleep
In COPD o2 is already low, drops further during sleep due to ODC
