Sleep Investigations Flashcards
What are the 6 main factors to consider when taking a sleep history?
▪️Medication
▪️Homeostatic
▪️Circadian
▪️Physical
▪️Psychological
▪️Environmental (incl. diet)
Ideally, how long should a sleep diary be kept for?
1-2 weeks
What are the benefits of a sleep diary?
▪️Determine what a typical night is
▪️Compare weekends and weekdays
▪️Discern patterns and variability
What is the most commonly used self-report scale of sleepiness?
The Epworth Sleepiness Scale
What is a normal score on the Epworth Sleepiness Scale?
0-10
What does a score of 11 or above indicate on the ESS?
Excessive sleepiness
What are the main problems with the ESS?
▪️Relies on honest reporting
▪️Doesn’t differentiate between times of day
▪️Scoring is uneven
What does actigraphy measure?
Motor activity via an accelerometer on the wrist. This can then be translated into sleep-wake data.
What can actigraphy be used for?
▪️Circadian rhythm disorders
▪️Insomnia
▪️Ensuring sleep isn’t restricted prior to Multiple Sleep Latency Test
▪️Measuring effect of medication
▪️Monitoring periodic limb movements
What can actigraphy measure?
▪️Motor activity
▪️Sleep times and fragmentation
▪️Sleep onset latency
▪️Wakefulness after sleep onset
▪️Activity levels before bed
▪️Sleep hygiene
What are the advantages of actigraphy?
▪️Unobtrusive
▪️Longitudinal (often several weeks)
▪️Can be used at home
What are the limitations of actigraphy?
▪️Usually only in specialist clinics
▪️Not validated with all sleep. disorders and populations
▪️Cannot measure sleep stages
▪️Expensive
▪️Commercial equivalents are unreliable
What does pulse oximetry measure?
Oxygen saturations and pulse rate
What investigations are useful in the diagnosis of obstructive sleep apnoea?
Pulse oximetry and respiratory study
How do you diagnose obstructive sleep apnoea using pulse oximetry?
▪️Visual inspection of oxygen saturation and pulse rate tracing
▪️Computer calculated oxygen desaturation index (ODI)
What does an ODI between 5 and 15 indicate?
Mild obstructive sleep apnoea
What does an ODI between 15 and 30 indicate?
Moderate obstructive sleep apnoea
What does an ODI of 30 or greater indicate?
Severe obstructive sleep apnoea
What is the oxygen desaturation index?
A measure of how many times blood oxygen levels drops by 4% of more per hour of sleep
How is pulse oximetry use clinically?
To screen for sleep related breathing disorders (e.g. OSA).
To determine if OSA is position dependent or REM related.
At what point during sleep is sleep apnoea most severe?
During REM because it is aggravated by the atonia
What are the advantages of pulse oximetry?
▪️Cheap and easy
▪️Can be used anywhere
▪️Analysis is quick
▪️Equipment is widely available across clinics, units and wards
▪️High specificity
▪️Can sometimes detect periodic limb movements
What are the limitations of pulse oximetry?
▪️Disagreement over what degree of desaturation should be used (4%?)
▪️Poor sensitivity
▪️Won’t detect apnoea if arousal occurs before oxygen sats drop
▪️Interpretation should be cautious
What are the four main components of a respiratory study?
▪️Pulse oximetry
▪️Nasal airflor
▪️Chest respiratory movements
▪️Abdomen respiratory movements
What are the advantage of a respiratory study?
▪️Can be done at home
▪️Widely available in sleep, respiratory and ENT units
▪️Ensures all body positions are monitored
What are the main clinical uses of respiratory study?
▪️Detect apnoea which don’t lead to desaturations
▪️Detect mixed apnoaes where there are central and obstructive elements
How would you conduct an inpatient split night respiratory study?
First half is diagnostic, looking for OSA
If OSA is found, in the second half you can do a CPAP titration to determine the right pressure needed for treatment
What is CPAP?
Continuous Positive Airway Pressure - a treatment for OSA whereby a mask delivers air at a constant, appropriate pressure to help them breathe
What are the limitations of respiratory study?
▪️Cannot detect impact if respiratory events on sleep
▪️Cannot detect respiratory effort related arousals
▪️Home studies arent widely available and probe to technical problems
▪️Cannot usually detect non-respiratory sleep problems as it can’t give insight into sleep stages or brain activity
What is WatchPat?
A device on the wrist that measures finger blood volume (PAT), HR, oximetry, actigraphy, body position, snoring, and chest motion
What can WatchPat be used for?
Detecting OSA, sleep fragmentation, and sleep architecture
What are the limitations of WatchPat?
▪️Expensive
▪️Poor insight into sleep stages
What is the gold standard investigation for sleep disorder?
Polysomnography
What are the three components of a basic polysomnogram?
▪️EEG (brain activity)
▪️EOG (eye movements)
▪️Submental EMG (upper airway muscle activity)
What other components can be added to a polysomnogram?
▪️Respiratory channels
▪️ECG
▪️Tibialis EEG (lower limb movement)
▪️Video
▪️Audio
What extra components may be added to polysomnography to investigate REM behaviour disorder?
▪️ECG
▪️Tibialis EMG
▪️Video
What conditions can you investigate with polysomnography?
▪️OSA
▪️Periodic limb movement disorder
▪️Insomnia
▪️NREM parasomnias
▪️REM behaviour disorder
▪️Nocturnal epilepsy
Ideally, for how many nights would you use polysomnography?
2-3
What are the advantages of polysomnography?
▪️Gold standard
▪️Differentiates sleep stages
▪️Can detect epileptic phenomena
▪️Measures sleep time, awakenings and arousals
▪️Can determine impact of sleep disorders on sleep (e.g. things too mild for other investigations to detect but still important)
What are the limitations of polysomnography?
▪️Expensive
▪️Analysis requires highly skilled professionals and a lot of time
▪️Very invasive - doesn’t represent normal sleep environment
▪️Only in specialist sleep centres
What is the Multiple Sleep Latency Test (MSLT)?
A test used to measure daytime sleepiness / the ability to initiate sleep
What are the main clinical uses of MSLT?
▪️Daytime sleepiness in central hypersomnolence
▪️Differentiates narcolepsy from idiopathic hypersomnolence
▪️OSA patients with ongoing sleepiness despite good control with CPAP
When and why is actigraphy used for the Multiple Sleep Latency Test?
For a week at the beginning, to ensure that sleep opportunity is not restricted
What is conducted the night before the MSLT and why?
An overnight polysomnogram with full array to ensure the patient gets adequate sleep the night prior to the test and to screen for other sleep disorders.
What is the main MSLT procedure?
Patient stays in clinic for the day with the basic polysomnogram array and is asked to try to nap every two hours, up to 5 times.
The nap trial ends after 20 minutes if they haven’t fallen asleep or 15 minutes after sleep onset. Sleep is staged.
What is the overall MSLT procedure?
- One week actigraphy
- One night polysomnography
- Up to 5 nap trials every two hours (stop after 20 mins if unsuccessful and 15 is successful)
What are the two main variables measured with the MSLT?
- Sleep onset latency
- Sleep onset REM
What is sleep onset latency?
The time from the start of a nap trial to the first 30 second epoch scored as sleep
In normal subjects, what is the mean sleep onset latency (SOL)?
10-20 minutes
What does a mean SOL of 8 minutes or less indicate?
Excessive sleepiness
What does a mean SOL of 3 minutes indicate?
Narcolepsy
What does two or more naps with REM indicate during the MSLT?
Narcolepsy
What does fewer than two naps with REM in the presence of SOL of 8 minutes or less indicate?
Idiopathic hypersomnolence
Why is it important to differentiate between narcolepsy and idiopathic hypersomnolence?
Narcolepsy may need treatment with intense stimulants or medication.
Idiopathic hypersomnolence may be indicative of other comorbidities such as depression or medication side effects, for which treatment might cause more damage
What are the advantages of the MSLT?
▪️Can give an objective measure of sleepiness if you’re considering stimulants
▪️Can differentiate narcolepsy without associated features of REM instability from idiopathic hypersomnolence
What are the limitations of the MSLT?
▪️False positives and negatives are not uncommon
▪️Anxiety may prevent sleep
▪️Medications may interfere (increasing or decreasing sleepiness)
▪️Protocol is not well standardised
How might antidepressants effect the interpretation of MSLT?
Most of them suppress REM, possibly giving a false negative for narcolepsy
How might antidepressant withdrawal affect the MSLT?
Within a couple of weeks of the test can lead to REM rebound, giving a false positive for narcolepsy
What is the Maintenance of Wakefulness Test (MWT)?
A test used to measure ability to resist sleep.
What is the main use of the MWT?
To confirm whether someone with a sleep disorder is sufficiently alert to be safe to drive, work, etc
Does the MWT procedure have to be preceeded by actigraphy and a polysomnogram?
Not always
What is the MWT procedure?
A patient with PSG array is placed in a dim room on a reclining bed. There are four trials, usually 40 minutes, at 2 hour intervals during with which they have to try to stay awake.
When is an MWT trial terminated?
After three continuous 30 second epochs of N1, or after one 30 second eposh of any other sleep stage
What would a SOL of 8 minutes or less indicate during the MWT?
Abnormal alertness
What would an SOL between 8 and 40 minutes during the MWT indicate?
Uncertain alertness
What SOL would indicate good alertness during the MWT?
Greater than 40 minutes (i.e. no sleep in any trial)
What is the mean SOL of presumed normal subjects during the MWT?
30.4 minutes
What test would you use to investigate ability to initiate sleep?
The Multiple Sleep Latency Test
What test would you use to investigate ability to resist sleep?
The Maintenance of Wakefulness Test
What are the advantages of the MWT?
▪️A negative result is very reassuring
▪️It is better than MSLT for fitness to drive
▪️Useful if there’s a discrepancy between self-report and observed alertness
Does ability to initiate sleep relate to ability to resist sleep?
Not necessarily
What are the limitations of the MWT?
▪️Is it really representative of trying to stay awake behind the wheel?
▪️Restrictions on caffeine, smoking or exercise is not representative of real life (BUT should be able to function without them)
▪️Protocol isn’t standardised
▪️Microsleeps may not be picked up
What is the Oxford Sleep Resistance Test (OSLER)?
A similar test to the MWT, patients lie in a dim room and complete 4x 40 minute trials where light is flashed every 3 seconds and have to press a button in response it. 7 consecutive misses are taken as sleep.
What are the advantages of the OSLER test?
▪️Easy to use and interpret
▪️Can be done in any setting
▪️Doesn’t require EEG
What study should you request for insomnia?
Actigraphy
What study should you request for hypersomnia?
Actigraphy, polysomnography, and MSLT
What study should you request for parasomnias?
Polysomnography
What study should you request for movement disorders?
Polysomnography
What study should you request for sleep related breathing disorders?
Oximetry, respiratory study, polysomnography, WatchPat
What study should you request for
circadian rhythm disorders?
Actigraphy
What study should you request for assessing safety to drive?
MWT and OSLER
What are the six categories of sleep disorder?
- Breathing disorders (e.g. OSA)
- Insomnia
- Hypersomnolence (e.g. narcolepsy, idiopathic hypersomnia)
- Movement disorders (e.g. periodic limb movements)
- Circadian rhythm disorders - body clock out of sync (e.g. delayed sleep wake phase disorder)
- Parasomnias - unwanted experiences and behaviours
What are examples of NREM parasomnia?
Sleepwalking, night terrors
What are examples of REM parasomnia?
REM sleep behaviour disorder, nightmares
What sleep related movement disorder might present as excessive sleepiness?
Periodic limb movement disorder
What sleep related movement disorder might present as inability to sleep?
Restless legs
What type of circadian rhythm disorder is more prevalent in the elderly?
Advanced sleep wake phase disorder
What type of circadian rhythm disorder is more prevalent in the adolescence and periods of development?
Delayed sleep wake phase disorder
In what type of parasomnia are you more likely to see sexonomia and why?
Non-REM because it is an automatic behaviour
What type of parasomnia is more likely to result in behavioural abnormalities later on in the night?
REM sleep behaviour disorder
What is chronotherapy?
Sleep restriction therapy - calculate how long it usually takes them to sleep and don’t let them sleep til then then gradually allow them to sleep earlier.
Potentially useful for insomnia
