Measuring depth of sleep in the ICU
Working towards a fully automated assessment of quality of sleep
Laurens Reinke
Medical Technician, PhD student
December 8, 2014
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Universitair Medisch Centrum Groningen
Intensive Care Volwassenen
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Sleep deprivation in the ICU
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Sleep and delirium
Emotional stress Fluctuating mental status
Neurocognitive dysfunction
Inattention
↓ Immune func on
Prolongation of mech. vent.
Altered endocrine function (REM) Slaap deprivatie
↑ pain sensi vity
↓ FEV‐1 and FVC
↑ symp. cardiac modulation
↓ paras. cardiac modula on
Delirium
Delier
Emotional stress
Fluctuating mental status
Neurocognitive dysfunction
Inattention
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Environmental light
2500
Patient perspective
ICU window
amplitude (DN)
2000
1500
1000
500
0
400
450
500
550
600
650
700
750
800
wavelength (nm)
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The importance of light: the biological clock
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The importance of light: the biological clock
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A = normal reference
B = ICU patient with bacterial pneumonia, day 3‐5
C = ICU patient with viral pneumonia, day 9‐11
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Sleep architecture
Wakker
REM
N1
N2
N3
N4
12:00
13:30
15:00
16:30
18:00
19:30
21:00
22:30
00:00
Absolute time
01:30
03:00
04:30
06:00
07:30
09:00
10:30
12:00
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Quality of sleep
ICU
Biorhythm
Sleep
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Arousals
Awakenings
Distribution of sleep over 24h
% Rapid eye movement (REM) sleep
% Slow wave sleep (SWS)
Architecture (ultradian rhythms)
Delirium
How to determine ‘quality’ of sleep?
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Polysomnography – Concerns of the intensivist EEG
EOG
Sleep parameters
Chin EMG
Resp. flow sensors
Snore sensor
ECG
Thoracic and abdominal Plethysmography
Position sensor
Polysomnography
Polygraphy
Pulse oximetry
Leg EMG
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Polysomnography – Concerns of the analist
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3 days * 24h * 3600s / 30s = 8640 segments of EEG to be analysed
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The (AASM) scoring rules don’t apply
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Sleep‐like EEG during wakefulness (microsleeps?)
(Bourne 2007, Cooper 2003, Freedman 2001, Drouot 2013)
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Frequent arousals/awakenings (~40 per hour)
(Watson 2007, Cooper 2000, Freedman 2001)
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Sleep is distributed over day and night (50/50)
(Hilton 1976, Cooper 2000, Freedman 2001, Hardin 2006) •
No recognizable sleep architecture
(Freedman 2001)
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Little to no REM sleep and SWS
(all the above)
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Result: poor interrrater reliability in ICU recordings
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Elliot 2013; kappa = 0.51 ‐ 0.56
Ambrogio 2008; kappa = 0.19
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Alternatives – Nurse assessment
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No correlation with PSG
(Beecroft, 2008)
– Overestimates total sleep time
– Underestimates awakenings
• Eyes closed ≠ sleep
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Alternatives – Actigraphy
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Agreement with PSG ~ 65%
(Beecroft, 2008)
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Unreliable in case of:
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Fixation in bed
Hypoactive delirium
ICU aqcuired weakness
Overestimates total sleep time
(van der Kooi, 2013)
• Motor ac vity ≠ sleep
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Alternatives – BIS
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Limited agreement with AASM sleep stages
(Nieuwenhuijs, 2002)
• Seda on ≠ sleep
– Not spontanious
– Non circadian
– But most importantly: • not dynamic
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The way forward: Automated analysis
Strengths
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Cheap
Fast
Repeatable
Objective
• Result:
– Only feasible solution for large studies
Weaknesses
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Difficult to simulate manual scoring
– Smoothing
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High inter‐ and intra‐patient differences
• Result: – Low to moderate agreement with manual scoring (kappa = 0.2‐0.6)
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Current approach: ‘keep it stupid simple’
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ICU Depth Of Sleep (IDOS) index
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Semi‐automatic
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A single EEG channel –
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Manual selection of thresholds between wake, sleep and SWS
C4 (central)
A single EEG feature
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gamma/delta ratio (wakefulness/SWA)
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Current approach: ‘keep it stupid simple’
Outpatient database (n=15)
ICU patients (n=5)
High agreement with manual scoring (Cohen’s kappa: 0.7‐0.9)
Low/moderate agreement with manual scoring
(Cohen’s kappa: 0.2‐0.6)
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Under development
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On‐line
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Artefact filtering
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Fully automated scoring
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Recognize other types of EEG activity
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REM sleep
Burst suppression
Other sedation effects
Define and calculate quality of sleep
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Weighted average of EEG features?
Sleep continuity (X. Drouot 2014)
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Future perspectives
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Further development of IDOS
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Compare IDOS with other algorithms and methods
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Automated real time clustering of EEG
PSG
Actigraphy
RCSQ
Somnolyzer 24x7
Powersleep
Explore the etiology of sleep disturbances in the ICU!
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Discussion
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Sleep is critically important…
…particularly for the critically ill
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There is currently no practical method to determine quality and distribution of sleep
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EEG is necessary to determine quality of sleep in the ICU
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A single index for quality of sleep is needed for future intervention studies
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Manual AASM scoring criteria are unpractical and unreliable for ICU recordings
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Simple, objective EEG features are more important than traditional sleep scorings in ICU recordings
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Practicality outweighs spatial resolution of ICU sleep EEG recordings
(i.e: less electrodes is better)
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Thank you for your time
You can contact me @ l.reinke@umcg.nl
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