An Online Metric Of Sleep/Wake Using the Unitary Measure, Z-ratio.

An Online Metric Of Sleep/Wake Using the Unitary Measure,

Z-ratio.

Claude Albertario, RPSGTMineola, NY USA

ZOMNOGRAPHY

ZOMNOGRAPHY, C.Albertario WINTHROP UNIVERSITY HOSPITAL

2WASM 2005

Polysomnography EEG Patterns

Adapted From: Current Concepts: The Sleep

Disorders. Peter Hauri, The Upjohn Company,

1977

?

?


3WASM 2005“Call to Arms”

From: Dement, William C., Commentary, Sleep: An Active Process, Ed. Wilse Webb, Scott, Foresman & Co. 1973, pg. 49.


4WASM 2005

“Call to Arms” cont’d

“More studies are needed that evaluate "sub-cortical" arousals, EEG arousals, and daytime function simultaneously.”

As stated in:The effect of sleep fragmentation on daytime function, Stepanski EJ.Sleep. 1984;7(1):18-26


5WASM 2005Polysomnography EEG Patterns

{

BETA>12 cps

ALPHA8-12 cps

DELTA.5 –2 cps

THETA3-7 cps

MIXED

Adapted From: Current Concepts: The Sleep

Disorders. Peter Hauri, The Upjohn Company,

1977


6WASM 2005

Standard R&K Scoring

“Stage 1 is defined by a relatively low voltage, mixed frequency EEG with a prominence of activity in the 2-7 cps range.”

“The faster frequencies are mostly of lower voltage than the 2-7 cps activity.”

Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects., Rechtschaffen A, Kales A, eds., Los Angeles: UCLA Brain Information Services/Brain Research Institute; 1968.


7WASM 2005

Standard R&K Scoring cont'd

The information used to determine sleep or wake is derived specifically from the EEG.

The EOG and EMG are used basically to “qualify” sleep stage, NOT determine sleep vs. wake per se.


8WASM 2005SLEEP/WAKE EEG Pattern Recognition

Voltage

Lower

Higher

Frequency

Slower

Faster

Adapted From: Current Concepts:

The Sleep Disorders. Peter Hauri, The Upjohn Company, 1977


9WASM 2005

Historical EEG “Relativity” Analyses

Inter-hemispheric EEG studies reflect the RMS power between hemispheres using a simple relational formula:

Left Power – Right Power

Left Power + Right Power(“Total Power”)


10WASM 2005

A new Tool: The FFT

“Fast Fourier Transform: A class of

algorithms used in digital signal

processing that break down

complex signals into elementary

components.”http://computing-dictionary.thefreedictionary.com/FFT


11WASM 2005

FFT Results of a simple 5 Hz signal


12WASM 2005

FFT Results of a simple 10 Hz Signal


13WASM 2005

FFT Results of a mixed 5Hz+10Hz Signal


14WASM 2005

FFT Results of a Multi Hz signal


15WASM 2005


16WASM 2005

}SLOW<7 cps

“SLEEP”{

BETA>12 cps

ALPHA8-12 cps

DELTA.5 –2 cps

THETA3-7 cps

MIXED

}FAST>7 cps

“WAKE”

Adapted From: Current Concepts:

The Sleep Disorders. Peter Hauri, The Upjohn Company, 1977


17WASM 2005

R&K derived 1 sec Z-ratio “Domains”

Frequencies SLOWER than 7 cps are considered SLEEP related in nature

SLOW = SLEEP

Frequencies FASTER than 7 cps are considered WAKE related in nature

FAST = WAKE


18WASM 2005

“prominence”

prominence: noun: relative importance

Z-Ratio depicts the prominence of the background EEG, as instructed in R&K, by numerically highlighting the relative contribution of the slow frequencies compared to the wake frequencies.


19WASM 2005

R&K Meets FFT

Z-Ratio depicts the relative contribution of frequency domains derived from the Fast Fourier Transform.

“SLEEP” (<7cps) – “WAKE” (>7cps)

“SLEEP” (<7cps) + “WAKE” (>7cps)(“TOTAL POWER”)


20WASM 2005

Z-ratio Examples

When the background EEG has more power in the FASTER frequencies (>7 cps) the Z-ratio will be NEGATIVE

= -1= (0-1)

1

(SLOW – FAST)(SLOW + FAST)


21WASM 2005

Z-ratio Examples cont’d

When the background EEG has more power in the SLOWER frequencies (<7 cps) the Z-ratio will be POSITIVE

= +1= (1-0)

1

(SLOW – FAST)(SLOW + FAST)


22WASM 2005

Review of Z-ratio publications Quantification of Sleep/Wake in 2 seconds of EEG, Albertario, C.

and Maberino, M., Journal of Polysomnographic Technologists, Dec. 1991 First described the algorithm and depicted the onset of sleep using 2

second epochs of Z-ratio.


23WASM 2005

Review of Z-ratio publications cont’d

Computerized Quantification of Sleep and Wakefulness in the EEG, Albertario, C., Hertz, G. and Feinsilver, S., Sleep Research, 1991.

Across 10 normal subjects: The Mean Z-Ratio for each stage was

significantly different from every other stage at the p<.01 level or better, except for REM and Stage 2 which were not significantly different.

“No patient demonstrated a mean Z-ratio that was negative during sleep.”


24WASM 2005


Comparisons of Z Ratio and Standard scoring techniques for sleep/wake determination on the MSLT, Albertario, Zendell, Hertz, Maberino, and Feinsilver, Sleep Research, 1992

By using a Z-page threshold between -.10 and -.15 , Central and Occipital Z-Ratio agreement with expert scorers was 89% and 93% respectively.


25WASM 2005


Comparison of a Frequency-based Analysis of Electroencephalograms (Z-Ratio) and Visual Scoring on the Multiple Sleep Latency Test, Albertario, et al. Sleep, 1995

80% kappa for Sleep/Wake determination comparing Z-ratio to expert scorers.


26WASM 2005


Visual Scoring Versus Quantitative EEG Analysis: An Ambulatory Home PSG Study, Von Gizycki et al., Sleep Vol. 22 Supplement #1, 1999 Found no significant differences between Z-ratio and

visually scored methods of sleep/wake Agreement as to sleep or wake, was 87% between

expert scorers and Z-ratio“Together, these observations suggest that the Z-ratio

method could be used to perform quantitative analysis of EEG data during day and night.”


27WASM 2005

Applying Z-ratio on Previous data Discrimination Among States of Consciousness Using EEG Spectra,

Lubin, A, Johnson, LC, Austin, MT, Psychophysiology, 1969, 6, 122-132 as reprinted in Sleep: An Active Process, Wilse Webb, Scott, Foresman & Co. 1973, pg. 103

“Spectral Analysis of the parietal EEG lead does not provide enough information to differentiate among stages

W, 1, 2, 3, 4 and REM”


28WASM 2005

Z-ratio

Negative

Positive


29WASM 2005

Used as an “Online” tool … can be performed on each EEG channel

independently, no ancillary parameters required … is UNITARY in that the algorithm can be

computed from ANY EEG analysis, as long as the source EEG analysis does not perform a priori frequency weighting

… does not “score sleep,” instead It provides a metric upon which to gauge sleep/wake

…is the only simple, transparent, intuitive reduction of EEG into a single per second quantified sleep/wake metric


30WASM 2005

Present On-line Z-ratio from Medcare


31WASM 2005Z-ratio in Analysis


32WASM 2005Z-ratio Depicting Spindles (confound?)


33WASM 2005

Possible analyses using Z-ratio

Viewing second by second EEG

based numeric FFT values allows for

new methods and constructs of

depicting human sleep.


34WASM 2005

Consecutive 1 sec Occipital Z-ratios from Start of Recording

y = 2E-05x - 0.1568

R2 = 0.0756

-1.00

-.80

-.60

-.40

-.20

.00

.20

.40

.60

.80

1.00

Z-R

atio


35WASM 2005

Consecutive per second Occipital Z-ratios from Start of Recording y = 2E-06x + 0.5597

R2 = 0.0032-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Z-R

ati

o


36WASM 2005

Consecutive per second Occipital Z-ratios from Start of Recording

y = 9E-06x - 0.4615

R2 = 0.0328-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Z-R

ati

o


37WASM 2005

Occiptal Z-ratios of DSPS patienty = 4E-05x - 0.5067

R2 = 0.2894

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Z-r

ati

o


38WASM 2005

Consecutive per second Occipital Z-ratios from Sleep onset

y = -3E-05x + 0.6165

R2 = 0.1017

-1-0.8-0.6

-0.4-0.2

00.20.40.6

0.81

1.2

Z-R

atio


39WASM 2005

Percentiles plot of 1 sec Z-ratios


40WASM 2005

Frequency Distribution


41WASM 2005

Some Further analyses using Z-ratio

Multi-site Z-ratio mapping

Infradian, Circadian and Ultradian EEG

rhythmicity similar to limb movements recorded

by actigraphy over multiple 24hr periods blindly

to subjective mental state and etiology.


42WASM 2005External EDF file


43WASM 2005

Posing Questions

Q. Is the following activity Cyclic Alternating Pattern, or Chervin’s “Respiratory cycle-related EEG changes (RCREC)“?

Method for detection of respiratory cycle-related EEG changes in sleep-disordered breathingChervin RD, Burns JW, Subotic NS, Roussi C, Thelen B, Ruzicka DLSleep. 2004 Feb 1;27(1):110-5


44WASM 2005


45WASM 2005During SWS


46WASM 2005Through Apneas


47WASM 2005Also through REM


48WASM 2005

Rhythms, Respiration and EEGQ. Is it respiration influencing EEG or an underlying EEG rhythmicity influencing or

controlling respiration and/or other bodily functions?

The influence of the respiratory cycle on the EEGBusek P, Kemlink D.Physiol Res. 2005;54(3):327-33

Electroencephalographic Changes during Respiratory Cycles Predict Sleepiness in Sleep Apnea, Chervin et al. Am. J. Respir. Crit. Care Med..2005; 171: 652-658

The cyclic alternating pattern as a physiologic component of normal NREM sleep. Terzano MG, Mancia D, Salati MR, Costani G, Decembrino A, Parrino L., SLEEP 1985;8:137-45

Obstructive sleep-disordered breathing with a dominant cyclic alternating pattern—a recognizable polysomnographic variant with practical clinical implications. Thomas RJ; Terzano MG; Parrino L; Weiss JW., SLEEP 2004;27(2):229-34.


49WASM 2005

Novel and transparent methods of depicting: Arousal Time Micro-Sleep during wake time Cyclic Alternating Pattern? Circadian sleep/wake EEG information Epileptiform activity Highlighting normal sleep EEG phenomenon

Tracé-Alternant Spindling, K-complexes Vertex sharp waves Delta and Alpha bursts

Further analyses using Z-ratio cont’d


50WASM 2005

Pros of utilizing Z-ratio Does not stage sleep Can be performed on-line Single intuitive value Impervious to sensitivity/gain and

voltage changes Can be used across hardware platforms

and/or analysis routines Can be performed identically, repeatedly Needs no calibration procedure


51WASM 2005

Cons of utilizing Z-ratio

× Does not stage sleep× Vulnerable to filtering of EEG signal× Similarly vulnerable to human susceptible

EEG artifact (i.e.. drug induced pseudo-spindling, motion artifact, etc.)

× Expectation of normal brain functioning, though may be sleep disordered


52WASM 2005

Use of Z-Ratio

Use of the Algorithm is FREE*!

*Please visit www.zzzratio.com to review this presentation online and find out more

about the free use of Z-Ratio.

An Online Metric Of Sleep/Wake Using the Unitary Measure, Z-ratio.

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Transcript of An Online Metric Of Sleep/Wake Using the Unitary Measure, Z-ratio.