Sleep investigations Flashcards
What is the utility of a sleep diary?
Allows you to determine a typical night’s sleep and see how much variability there is
Compared weekends and weekdays
Discern patterns
What is the scoring system of the Epwrtj sleepiness scale?
0-3 (never to high chance)
8 situations
11+ is excessively sleepy
What is actigraphy?
Accelerometer worn on the wrist to collect continuous data on movements for several weeks
Translated into sleep-wake data
Can confirm circadian rhythm disorders
What is actigraphy used for?
Determining the sleep pattern in insomnia
Measuring sleep fragmentation
Ensuring sleep is not restricted prior to multiple sleep latency test
What are the limitations of actigraphy?
Available only in specialist sleep clinics
Not validated with all sleep disorders and populations
Cannot measure sleep stages
How is pulse oximetry used?
Measures O2 saturation and pulse rate
Used in diagnosis of obstructive sleep apnoeas
(From pulse oximeter and calculated oxygen destruction index)
What are the severity levels of OSA?
Oxygen saturation index
Mild 5-15
Moderate 15-30
Severe 30+
What are the limitations of pulse oximetry?
Unclear what percentage of desaturation should be used
High specificity but lower sensitivity
Will not detect apnoeas if there is arousal before oxygen saturation drops
What does a respiratory study entail?
Pulse oximetry
Nasal airflow
Chest and abdomen respiratory movements
Can be done inpatient or at home
Inpatient may be split between diagnostic and CPAP titration
What are the advantages of respiratory study?
Detect apnoeas before desaturation
Detect mixed (central and obstructive) sleep apnoeas
All body positions are monitored
What are the limitations of respiratory study?
Cannot detect the impact of respiration on sleep
Can miss respiratory effort arousal
Require more time and expertise to analyse
Home studies prone to technical problems
Cannot usually detect non respiratory sleep disorders
What does a WatchPat do?
Measures
PAT signal
Heart ratpcimetry
Sctigrsohy
Body position
Snoring
Chest motion
Can detect OSA, sleep fragmentation, and sleep architecture
What does a polysonogram include?
EEG
EOG
Submental EMG
Tibialis EMG
ECG
Video + Audio
What is a polysomnogram used to detect?
OSA
PLMS
Insomnia
Non rem parasomnias
REM behaviour disorder
Nocturnal epilepsy
What is the gold standard method for sleep study?
Polysomnogram
What are the advantages of polysomnogram?
Differentiates between sleep stages and wherein the disorder occurs
Can detect epileptic phenomena
Measures time awakenings and arousals
Can determine the impact of the disorder on sleep
What are the limitations of polysomnograms?
Analysis is required by highly skilled professionals
Sleep may be affected by wires, awareness of video, sleeping in a strange environment
Only available in specialist sleep centres
What is the multiple sleep latency test used for?
Measure the ability to initiate sleep
Measures sleepiness in hypersomnolence
Used to differentiate between narcolepsy and idiopathic hypersomnolence
May also be used for OSA with ongoing sleepiness
What is the procedure for MSLT?
1 week actigraohy
Overnight polysomnogram with full array to ensure adequate sleep before test
Patient remains in the clinic the following day and is asked to try to nap every two hours - up to 5 trials
Nap trial ends after 20 mins of no sleep, or 15 mins after patient falls asleep
What do results of MSLT indicate?
Normal subject sleep onset latency is 10-20 mins
Mean SOL less than 8 mins is excessive sleepiness
Mean SOL in narcoleptics is 3 mins
2 or more naps with REM - narcolepsy
SOL below 8 mins + less than 2 REM naps - idiopathic hypersomnolence
What are the limitations of MSLT
False positive and false negatives common
Trial settings may change patients sleep behaviour
Antidepressants suppress REM and can give a false negative for narcolepsy
Withdrawal of antidepressants 2 weeks before test can lead to REM rebound giving a false positive
The protocol is not standardised between labs or between clinical and research
What is the maintenance of wakefulness test?
Test ability to resist sleep
Can confirm if a person with sleep disorder is safe to drive or work
What is the normal SOL for the maintenance of wakefulness test?
30 mins
What is a big limitation of MWT in determining safety to drive?
Microsleeps below 15 seconds are not scored but can be fatal at 70mph+
What is the Oxford Sleep Resistance test?
Light flashes every 3 seconds, subject presses button
7 consecutive misses is taken as sleep
Easy to administer and interpret
What test should be requested for insomnia?
Actigraphy
What test should be requested for hypersomnia?
Actigraphy
MSLT
What test should be requested for parasomnias?
Polysomnogram
What test should be requested for movement disorders in sleep?
Polysomnogram
What test should be requested for sleep related breathing disorders?
Oximetry
Respiratory study
PSG
WatchPat
What test should be requested for circadian rhythm disorders?
Actigraphy
What test should be requested for fitness to drive?
MWT
OSLER
What are the six categories of sleep disorders?
Breathing disorders
Insomnia
Movement disorders
Circadian rhythm disorder
Hyoersomnolence
Parasomnias
What might be the underlying cause of REM sleep behaviour disorder?
Parkinson’s disease or Lewy body dementia
(Worsens on antidepressants)
