Session 8 Sleep physiology Flashcards
What are the 3 distinct states of brain activity?
wakefulness
non-REM sleep, including slow wave sleep
REM sleep
characteristics of non-REM sleep?
EEG (electroencephalography)- would show low frequency, high amplitude
synchronised
slow rolling eye movements
motor system capable
4 stages: 1 and 2= shallow, most of night, 2- spindle and K complex
3 and 4= slow wave
frequency decrease and amplitude increase with depth
EMG would show a moderate level of muscle tone
EOG would show that eyes not moving
characteristics of REM sleep?
high frequency, low amplitude EEG
muscle paralysis, excluding resp., so may wake and be unable to move for a few s, as low skeletal muscle tone- EMG, important so that we don’t act out our dreams
EOG: flicking eye mments, sudden jerking
muscle twitches
desynchronised firing of individual cells
ill defined depth
more common in last part of night
define insomnia
inability to sleep
define parasomnia
abnormal movements or behaviour in sleep e.g. sleep walking
how can sleep pattern be displayed
using a hypnogram
what does a hypnogram show?
Sleep follows a cycle of about 90mins. Early cycles comprise deep non-REM sleep, followed by short periods of REM. Later cycles have more lighter (Stage 2) NREM sleep and more REM sleep. We normally enter sleep through slow wave sleep (non-REM) and often leave it through REM. We may wake between cycles but don’t remember it unless we wake for >20secs
5 main classes of sleep disorders?
difficulty initiating and maintaining sleep (DIMS)
disorders of excessive sleepiness
parasomnias
circadian rhythm disturbances
sleep related factors in systemic disease
examples of disorders in initiating and maintaining sleep?
insomnia- acute and chronic depression poor sleep hygiene drug induced fatal familial insomnia paradoxical insomnia= people believe they're not sleeping well but tests show that they are
disorders of excessive sleepiness?
Primary: narcolepsy- suddenly falling asleep at inappropriate times long sleepers short sleepers cerebral injury e.g. stroke, trauma idiopathic hypersomnolence
Primary= neurological problem
Secondary- sleeping broken up by multiple arousals: obstructive sleep apnoea, central sleep apnoea, limb movement disorders- restless legs, periodic limb movement
examples of circadian rhythm disorders?
jet lag delayed sleep phase syndrome advanced sleep phase syndrome long sleep non-entrained circadian rhythm
DSPS is common in young people and ASPS in older people (sleep early, wake early). Most people’s body clocks are entrained to 24 hours, those blind from birth free-run, their day is about 24.5 hours long
what is assessed in sleep?
duration
quality
architecture- use a hypnogram
assoc. phenomena
how can sleep duration be assessed?
diary- form/questionnaire
actigraphy- monitors movement, usually at wrist, something they can wear on wrist like a wristwatch and it may tell the time
polysomnography- assesses lots of functions
characteristics of sleep diary?
records time to bed, how many times awoken, wake time, out of bed time
moderately objective
but people often underestimate how much they sleep
can be useful as a therapeutic tool
what does polysomnography measure?
electrophysiology- EEG, EMG, ECG, EOG
movement
respiratory- Chest wall movement, airflow, airway pressures, oximetry, CPAP pressures
CVS: HR, HR variability and BP
what is cataplexy?
bilateral, sudden-onset loss of muscle tone with preserved consciousness, may happen with emotional extremes e.g. very happy, angry, coincidence
partial or complete muscle wkness
knees, and face/neck most commonly affected, eye and resp function not affected
full attack takes several s to develop
attacks last from several s to rarely several min
how is wakefulness assessed?
questionnaires
multiple sleep latency
multiple wakefulness
vigilance testing
example of questionnaire used to assess wakefulness?
epworth sleepiness scale: Likelihood of falling asleep in 8 common situations (0-3), maximum score 24
Normals 2-10
OSA 4-23
Insomnia 0-6
Narcolepsy 13-23
describe multiple sleep latency
After monitored sleep
measure latency to sleep onset
5 nap opportunities of up to 20mins, 2hr apart
Darkened room: “Fall asleep, please”, comf bed, quiet
units of measure= mins to sleep onset (stage 1), mins to REM sleep onset (from stage 1 onset)
Mean Latency >10mins, normal
mean sleep latency /2 SOREM episodes diagnostic for narcolepsy
describe mutiple wakefulness to assess wakefulness
After monitored sleep
4 nap opportunities of up to 20mins
Darkened room: “Stay awake, please”
Mean Latency >11mins, normal
probably better than multiple sleep latency for judging unintended sleepiness
what is hypersomnia?
excessive daytime sleepiness
typical characteristics of an obstructive sleep apnoea patient (secondary cause of DOES)?
daytime sleepiness unrefreshing sleep snoring witnessed apnoeas- gap in breathing obese big neck crowded oropharynx type 2 DM, high BP, IHD
significant problems resulting from OSA?
road traffic accidents
nocturia- as increased thoracic stretching as air not being shifted into oropharynx with chest movements, stretch of atrium-ANP release-vasodilates affer arteriole to increase GFR, and subsequent Na+ and H20 excretion
reduced QOL
reduced cognition
mood changes
excessive dtime sleepiness and unrefreshing sleep
what is apnoea?
without breath, 100% cessation of aflow for 10s
what is hypopnoea?
50% decrease of aflow over 10s
what is central apnoea?
neurological cause means lack of effort
define obstructive sleep apnoea
absence of airflow from an obstruction during sleep
how might an overbite be responsible for OSA?
tongue is attached to lower jaw so if jaw is down, the tongue hangs down
upper airway causitive factors for OSA
large tonsils poor nasal airway chunky uvula long soft palate/uvula narrow max arch large tongue overbite
what is catathrenia?
groaning in sleep, expiratory sound
use of apnoea-hypopnea index in defining OSA?
look at frequency of events per hr
mild= 5-14
moderate= 15-29
severe= >30
5 core symptoms of narcolepsy?
EDS- continous, and sleep attacks- usually </20min
cataplexy
hallucinations- occur during transition between sleep and wake, usually bizarre and frightening
sleep paralysis- at sleep onset or upon wakening, consciousness preserved, frightening/disconcerting
disturbed night-time sleep
how is EDS in narcolepsy releieved?
daytime naps
clinical presentation of cataplexy?
arm or leg wkness sagging jaw nodding head slurred speech full attack= complete muscle atonia and postural collapse
how does living with narcolepsy affect patients?
reduced performance in school and workplace interpersonal difficulty impaired social interaction accidents/injury-RTA and workplace depression loss of self-esteem
what does the sleep/wake flip-flop switch refer to?
pathways promoting wakefulness and sleep actively inhibit each other
what stabilises the sleep/wake flip-flop?
hypocretin
cause of narcolepsy in humans?
loss of hypocretin neurotransmission- reduced or absent levels in CSF of patients, marked reduction or absence of hypocretin-containing neurones
possible AI aeitiology- HLA link
likely that it is driven by environ factors in context of a strong genetic susceptibility
disadvantages of polysomonography?
expensive
time-consuming
how can a patient with OSA be helped to sleep more easily?
continuous positive airway pressure therapy- machine used to increase airway pressure so that a.way doesn’t collapse when you breathe in
daytime sleepiness assessment?
subjective: stamford sleepiness scale, epworth sleepiness scale
objective: multiple sleep latency test, maintenane of wakefulness test, vigilence tests e.g. OSLER
OSA home investigations?
oximetry only or respiratory sleep studies
what is the OSLER test?
test of vigilence:
4x40min in dark
light presented every 3s, release button
no response for 21s=sleep
driving simulators
how is a free running circadian rhythm treated?
strict routine
light
melatonin- more produced at night when dark, related to sleepiness
