Module 3 - Measurement of Sleep Flashcards
What did von Economo discover and when?
1916: found that encephalitis in flu epidemic led to profound sleepiness or wakefulness due to specific hypothalamus damage.
When did thinking about the unconscious, not just free will, come into discussion?
early 1920s due to Freud
What did Bremer discover and when?
- Used EEG to define physiology of sleep. Found slow waves.
Who described the stages of NREM sleep using EEG?
Loomis in late 1930s
What did Loomis discover?
The stages of NREM sleep using EEG in late 1930s
Who discovered the physiology of sleep and when?
Bremer in 1928
When was the Reticular Activating System discovered?
1949 by Magoun
What did Magoun discover and when?
The Reticular Activating System as a key area for arousal and consciousness in cats in 1949 by Magoun.
Who discovered REM sleep and when?
1953 by Aserinsky and Kleitman. Sleep is active
What did Aserinsky and Kleitman discover and when?
REM sleep, sleep is active. In 1953.
What did Demet discover?
In 1954, defined the human sleep cycle.
When was the human sleep cycle defined?
1954 by Demet.
Who identified the neurophysiology of sleep?
Jouvet in 1960s.
Identified different paralysis patterns in NREM and REM sleep.
What did Jouvet discover?
The neurophysiology of atonia in sleep in the 1960s.
What did Wurtman discover?
The inhibitory control of melatonin with light in 1963.
When was the relationship between melatonin and light established?
1963 by Wurtman
When did polysomnography become a thing?
1972 along with all-night tests becoming routine.
When was the neurochemistry of sleep being established in the literature?
1970s
In which decade did computers help advance the understanding of sleep?
1990s
When were Hcrt1 & 2 peptides discovered?
1998
In which decade was the genome and cell biology of sleep important in the literature?
2000s
When were cellular time keepers in the body discovered?
2010
What is the general decade-by-decade timeline of sleep medicine?
1930-40s: brain is important: EEG + encephalitis + RAS
1950s: sleep cycles
1960s: neurophysiology of sleep + melatonin
1970s: neurochemistry + OSA
1980s: sleep is a clinical speciality (CPAP)
1990s: computers support sleep
2000s: genome and cell biology
2010: cellular time clocks
When was sleep apnea discovered?
1965 by Gastant in one group and Jung and Kuhlo.
When did sleep become a clinical speciality?
1980s
When was CPAP discovered?
1981 by Sullivan
When was narcolepsy first described?
1880 by Gelineau
When was the CNS first described?
1875 by Caton
List the components of a PSG
EEG
EOG
EMG (chin + leg)
airflow
ECG
Respiratory Effort
tCO2
pulse oximetry
body position sensory
What is the difference between AC and DC channels?
AC: alternating - current changes polarity and direction
DC: direct - one polarity, slower speed
What are common PSG recordings in an AC channel?
EEG, EOG, EMG
What are common PSG recordings in a DC channel?
SaO2, Airflow, effort, TcCO2
What filters are used on AC channels?
Low, high and notch
What filters are used on DC channels?
Only high frequency
What are common errors on AC and DC channels?
AC: under sampling
DC: prone to over sampling
What frequencies do low, frequency and notch filters filter out?
Low: filters slow waves, < 0.5 ,3 ,5
High: fliters fast waves, > 10, 35, 70Hz
Notch: 50Hz
What is an issue with using Notch filters
Some seizures occur at 50Hz
What is the difference between I-IV sleep studies?
I: attended, PSG. 4-6 EEG, EOG, EMG, ECG, O2, flow, body position, respiratory effort, video, audio, maybe CO2
II: unattended, PSG, 2 EEG, 1-2EOG, EMG chin, maybe leg. ECG, sPO2, flow, effort, body position [less EEG, reduced EOG, no video, audio, tcCo2]
III: unattended, polygraph, sPO2, flow, effort
IV: unattended, 1-2 channels, Spo2 or actimetry
Which amplifier is respiratory effort measured on?
AC or DC, but need LFF < 0.1Hz
What is aliasing?
Misidentification of a signal frequency which introduces distortion or error
What is Nyquist Theorem?
Sample rate of analogue to digital must be at least 2x the value of the highest frequency you capture.
E.g. EEG expected 0.3-35Hz, therefore LOWEST sampling is 70Hz. Typically use 256 or 516Hz
When do we calibrate on a PSG?
Regularly required. Biocalibration at the start of every study (blink, eyes closed, move eyes, girt teeth, wiggle fingers, breathe and snore).
DC filters like oximetry (0v=0% and 1v=100%) and TcCO@ with known CO2 calibration.
How do you score arousals?
In both adults and children:
- NREM: abrupt shifts in EEG frequency for ≥ 3 seconds with ≥ 10 seconds of sleep prior.
- REM: same as above PLUS increase in chin EMG for ≥ 1 second.
Every wake must have an arousal scored.
Beware of mixing up spindles and arousal.
Marking the beginning is important, not the end.
What are some things to consider about scoring arousals?
Every wake must have an arousal scored.
Beware of mixing up spindles and arousal.
Marking the beginning is important, not the end.
How do you score a wake period?
> 50% of an epoch contains either or both:
- Alpha in O-leads (10% don’t and another 10% low)
- Blinks, REMs or reading eye movements
OR - A patient is disconnected from equipment
How do you set up for a PSG?
- Set up display how you like it
- Familiarise yourself with patients EEG (N3, REM, N2, N1 and review biological checks)
- Allocate sleep stages and mark arousal in 30s epochs
- Score respiratory events and leg movements on longer episodes (2,3,5 minutes)
- Generate report and check details
How do you score sleep onset?
Difficult to define as different systems can fall asleep at different times.
EEG can show changes (reduced alpha) but a persons response can differ
Hypnic myoclonia can occur (fall -> startle)
How do you score Stage N1 sleep?
> 50% epoch has no alpha, replaced by LaMF (do not have to be continuous)
OR, if they don’t produce alpha, N1 until the first sign of:
- EEG 4-7Hz slows down by >1Hz from wake
- vertex sharp waves
- slow eye movements
Keep scoring N1 until evidence otherwise
What do you score arousals after N2 or REM sleep?
N1
What do you score arousals after N3 sleep?
N2
How do you score stage N2 sleep?
First half of epoch or last half of previous epoch has K-Complex or spindle
Continue to score N2 until wake, arousal, body movement, N3 or REM
How do you score stage N3 sleep and in which leads do you expect to use?
When 20% (6 sec) of the page contains slow waves (0.5-2Hz) which are >75mV as measured by F3 or F4 leads.
CANNOT include:
- Pathological slow waves from encephalopathy or epilepform activity
- Slow waves produced by artefacts (commonly sweat)
Note: if no F-leads, if C or O leads are >75mV you can be sure F-leads would be
How do you score REM sleep?
All of the following are present:
- LaMF with no spindles or K-complexes
- Low chin EMG for >50% epoch
- REMs at any point in epoch -> so you can go back and score REM once you see them
If the epoch before the above does NOT have REMs, score REM if there is:
- LaMF with no spindles or K-Complexes
- Low chin EMG
- No intervening arousal
- No slow eye movements or wake
May have sawtooth waves
When should you use infant or child sleep scoring?
Infant: 0-2 months (37-48w)
Child: 2+ months
What are child and infant sleep stages?
Child: same as adults but also NREM
Infant: Wake/NREM/REM/Transitional
How do you determine sleep stages in children?
WAKE
- Posterior dominant rhythm is early alpha
- 3.5-4.5Hz (3-4m), 5-6Hz (5-6m), 7.5-9.5Hz (3y)
- Score when >50% epoch has age appropriate range, otherwise same as adult
N1
- PDR replaced by LaMF for >50% epoch or presence of hypnagogic hypersynchrony (v big waves) or high amplitude rhythmic 3-5Hz
N2, N3. REM is the same as adults
What are hypnagogic hyper synchrony?
Very big waves common in children
