control of breathing when asleep

Question 1

different controls of breathing

Answer 1

reflex/automatic - brainstem
vol/behavioural - motor cortex
emotional - limbic system
all input resp muscles via the phrenic nerves
vol can override the automatic - when awake

Question 2

changes in breathing mechanics during sleep

Answer 2

rely on brainstem 
minute vent decreases by 10% 
reduction in tidal vol 
freq of breathing is unchanged 
doesn't affect O2 saturation

Question 3

changes in oxygen saturation during sleep

Answer 3

reduction in PaO2

only small reduction in O2 saturation - on flat of ODC

Question 4

changes in CO2 with sleep

Answer 4

reduction in tidal vol = increase in CO2 - necessary to breath because CO2 sensitivity decreases
can measure ventilation sensitivity - graph with end tidal PaCO2 against ventilation

Question 5

the apnoeic threshold

Answer 5

CO2 level must be above the threshold to breathe during sleep

Question 6

why wouldn’t the apnoeic threshold be reached

Answer 6

tidal vol doesn’t decrease because of
stroke
central congenital hypoventilation syndrome

Question 7

influence of sleep in upper airway

Answer 7

when asleep more floppy so bit behind throat more relaxed
generates -ve pressure
airway closes

Question 8

effect of fat on the upper airway

Answer 8

+ve pressure pushing airway closed

can collapse

Question 9

obstructive sleep apnoea

Answer 9

caused by reduced upper airway which can lead to obstructive sleep apnoea
extraluminal pressure and -ve intraluminal pressure = occlusion of phalangeal airway

Question 10

affect of partially obstructed airway

Answer 10

turbulent airflow over the vocal cords - snore

Question 11

airways in older people

Answer 11

more compliant and more distendible

obstructive sleep apnoea

Question 12

affect of uvula sucked into airway

Answer 12

obstructive sleep apnoea

Question 13

central sleep apnoea

Answer 13

no central effort to breath

Question 14

obstructive sleep apnoea

Answer 14

effort of resp muscles
no airflow = obstructive
can stimulate by closing glottis and trying to breathe - diaphragm moves but no air in

Question 15

obstructive sleep apnoea cycle

Answer 15

patent airway
increased vent = next apnoea
sleeo
reduced muscle func
apnoea - hypoxia/hypercapnia = increased effort
arousal - because of effort trying to breath against closed airway
mood -ve because disturbed every minute, lose humour and emotional intelligence

Question 16

COPD and sleep

Answer 16

further down the ODC anyway so the reduction in PaO2 in sleep = reduction in O2 saturation

Question 17

Heart failure in sleep

Answer 17

cardiac disease
exacerbated by sleep
cause pul oedema = hyperventilate = low CO2
central sleep apnoea
therefore don’t breathe
already have bad heart so worsens the prognosis
in half of HF patients