obstructive sleep apnoea Flashcards
summarise resp control in sleep
– reduced output to resp muscles in sleep – lung onflation and ventilation is down. Co2 up – maintains breathing, ox stays say the same
how does obstructive sleep apnoea occur
• Relax of resp muscles = occlusion of upper airway – because soft tissue muscle bounded by tongue and laryngeal constrictor muscles round the back of airway – negative pressure in lungs to pull aior in = suck on flexible airway = collapse = apnoea from obstruction = obstructive sleep apnoea
EEG - Rapid activity when arousal from sleep after reduced breathing activity
Effort of trying to push air past tongue wakes person up
how does central sleep apnoea occur
• Medulla – some people when sleep lose cortical control of breathing, meduillary control takes over – if stroke or CCHS (genetic disorder) = pts not breathing when go to sleep. Also in HF where pul oedema = hypervent = low co2 = central sleep apnoea
does obstructive sleep apnoea matter
o Difficult for people to quantify what they’re quality of sleep is – so mybe doesn’t matter
o Prevalent so does matter – apnoea/hypopnea (paused) index = number times stop breathing overnight - >15 times an hour a lot. >5/hr – mild
o NHS not seeing all pts
o Should treat mild to stop them getting severe – but not doing this now
what is the obstructive sleep apnoea cycle
sleep decreased muscle tone upper airway collapse apnoea - intermittent hypoxia arousal - fragmented sleep and sleep disruption airway opens sleep
key issues of sleep apnoea
intermittent hypoxia and sleep disruption
intermittent hypoxia very dangerous in people with co-morbidities eg cardiac disease
reduction in airflow, fall in sats, rise in HR – when terminate apnoeaic event – adds load on CVS which is operating ion -ve pressure so load is additive
describe sleep function and significance of sleep fragmentation
Synaptic Homeostasis Hypothesis: Learning occurs via the formation of synapses
Neurones strengthen synapses when awake while interacting with the environment
Neurones renormalize synapses in sleep when the brain is ‘off line’
Arousal from sleep if frequent – don’t get ability to process activity = sleepy
how do you measure sleep objectively
Electroencephalogram: Sleep Lab
in ear sleep monitor
not every hospital has access to these
problem with subjective measure of sleep
People find it hard to assess sleepiness – we can use scales such as those that are used for pain
Epworth sleepiness scale
• Score >10 – on edge of being clinically sleepy
• >12 – clinically sleepy
describe obstructive sleep apnoea as a continuum
o People don’t suddenly wake up with, insidiously creep up on you – until not able to function.
at 1 end - flow limitation, difficulty getting air in = turbulent airflow = snoring
go through increase resistance airflow - upper airway resistance syndrome
mild - 5-15/hr
to moderate where stop breathing 15-30/hr
severe >30 events/hr
treatment of obstructive sleep apnoea
o CPAP continuous positive pressure airway pressure - recommended for patients with moderate to severe OSA and symptoms of sleepiness
o Blow positive air into airway
o Got to strap the mask to theyre face – need nose and mouth mask
o Machines smaller, quieter, and portable but need mask – deal breaker for a lot of pts
o Approx 1/3 pts struggle to use
o Have built in trackers to see how many hrs used
o Support – not all centres have team of sleep therapists
clinical effectiveness of CPAP
o Sleepiness scale improves for all studies of sleep apnoea
o CVS improvement of BP = if use >4hr – improves BP as much as anti-hypertension therapy in some pts
alternatives to CPAP
o Mandibular advancement splint – stops pharyngeal airway collapsing by pulling mandlible forward – buy over counter or orthodontist – not on NHS
o Sleep on tennis ball
o Device vibrate if sleep on back – tongue easier fall back if on back and adipose on neck
is CPAP cost effective according to NHS threshold £20,000/QALY gained
yes
who is given treatment for obstructive sleep apnoea
• If stop breathing <15/h not under NICE guidelines
• However treatment options vary in countries
• In UK count on symptoms as well as number of times stop breathing – allows on eductational experience of dr – means can consider impact on pt and spouse
mild - lifestyle measurements, consider CPAP and MAS (mandible advancement splint). CPAP might be too much of a burden
mod-severe - lifestyle measures and CPAP
