PSG ppt

Polysomnography:101

CSRT

Sleep medicine 2010

St. John’s, Newfoundland

Bernie W. Miller, BS, RRTRPSGT

Instructor, Mayo College of Medicine

Sleep Medicine Center. Supervisor

Mayo Clinic in Arizona

Disclaimer

I have no conflicts of interest and receive no

compensation from any sleep equipment

manufacturers

Historical Perspectives

1928 Berger placed electrodes on brain in a

patient who had a missing skull

1937 Loomis suggested first EEG

classification (A-E)

1953 Aserinsky and Kleitman discovered

REM sleep

1963 Rechtschaffen & Kales manual

2007 AASM publishes the new manual

Rechtschaffen and Kales

• EEG leads

• EMG of genioglossus

• EOG

• Sleep stage scoring only

AASM Manual

• Iber C, Ancoli-Israel S, Chesson A, Quan

SF for the American Academy of Sleep

Medicine. The AASM Manual for the

Scoring of Sleep and Associated Events:

Rules, Terminology and Technical

Specifications, Ist Ed.: Westchester,

Illinois: American Academy of Sleep

Medicine, 2007

Recording System

• Oscilloscope to paper, to computer

• Electrode placement

• Jack box or head box, montage selector

• Amplifiers (amplification, filters, calibration)

• Computer was revolutionary!!!

International 10-20 System

• Electrodes are placed apart 10 and 20% of the distance

• From nasion to inion, preauricular points, and top of the head

• Odd numbers are on the left side, Even on the right

Changes in Montage

• Reference electrodes (Just terminology)

• Number of EEG channels; Add Frontal leads

(three channels and three backup channels)

• Alternative channels

• EOG electrodes

• EMG electrodes

AASM Reference Electrode Change

Auricular (A) electrode placement has

been changed from ear to Mastoid (M).

A1 changed to M1

A2 changed to M2

AASM - EEG Derivations

Three channels

a. F4-M1

b. C4-M1

c. O2-M1

EEG - AASM

Backup channels

a. F3-M2

b. C3-M2

c. O1-M2

AASM – Alternative Derivations

Three channels

a. Fz-Cz

b. Cz-Oz

c. C4-M1

Backup channels

a. Fpz-C3

b. C3-O1

c. C3-M2

Amplifiers

• Alternating Current

fast frequencies EEG, EMG, EOG, EKG

(has both HFF and LFF)

• Direct Current

slow frequencies oximeter, CPAP, position

(does not have LFF)

Common Mode Rejection

• The ability of an amplifier to reject signals

common to both electrodes and amplify

the difference

• Same signals are called in phase or

common mode

• CMRR = Difference in voltage

Same voltage (rejected=0)

Differential AC Amplifiers

G1

G2

(C3)

(A2)

-70 µV

-10 µV

-60 µVAMP

Amplifiers

• Amplification of signals

• Filters

• Calibration

Amplification

• Gain, not really relevant in the computer

environment

• Sensitivity

Sensitivity

Measure of OUTPUT of an input voltage

The amount of voltage needed to deflect the recording pen a given distance

• Voltage= uV (microvolts) or mV (millivolts)

• Pen deflection= mm or cm

Sensitivity

Voltage

Sensitivity = Pen deflection

Provides a uniform increase in the size of

the waveforms

EEG CALIBRATION

• Standard calibration 50 uV/cm

(digital world 70 or 100 uv/cm)

• More deflection: Pen blocking artifacts

• Less deflection: Difficult to see low

amplitude waveforms

Amplitude of 50 µV at different

sensitivity levels

0

0.5

1

1.5

2

100 50 25

µV/cm

Am

plitu

de

50 uv/cm in a 4 year old

70 uv/cm in a 4 year old

100 uv/cm in a child

The Digital World

• Unfortunately in the digital world there are

variability's from one software type to the

other, filters may not filter uniformly.

• 0.3 LFF on one system may not be 0.3

LFF on another

Sampling Rates

• Sample at 200 to 500 hz

• ????????????????????

• Number of data points gathered per

second

Filters

Helpful in removing unwanted noise/artifacts

1. Low frequency filter

2. High frequency filter

3. Notch filter

4. ECG filter (during scoring)

EEG Filters

• Variable reduction in amplitude

80%

70%

50%

• Progressive decrease in amplitude below

(LFF) or above HFF) the cut off frequency

LFF and HFF

70Hz 140Hz 280Hz 560Hz

010

2030

405060

7080

90100

0

10

20

30

40

50

60

70

80

90

100

1.25Hz 2.5Hz 5.0Hz 10Hz

EEG HFF Settings

• Sleep EEG waveforms occur at 35 hz/cps

• Spike duration 20-70 msec

• Spike frequency 14-50 Hz

• HFF for seizures 70 Hz

EEG LFF Settings

• To improve low frequency baseline or

baseline drift / sweat artifact

• LFF 0.3 Hz

LFF = None

LFF = 0.1

LLF = 0.3

Notch filter

• Notch filters are designed to sharply attenuate a narrow frequency bandwidth within the range of 50 or 60 Hz.

• Notch filters are also known as 60Hz filters.

• These filters are used to eliminate the noise from electric power lines.

Filter Settings

Low High

• EEG 0.3 Hz 35 Hz

• EOG 0.3 Hz 35 Hz

• EMG 10 Hz 100 Hz

• Snoring 10 Hz 100 Hz

• ECG 0.3 Hz 70 Hz

• Respiration 0.1 Hz 15 Hz

Sampling Rates

Important in the computer age

AASM suggests 500 hz for

EEG/EOG/EMG/ECG

Minimal 200 hz acceptable

EMG

• Recorded as the potential between two surface

electrodes placed several centimeters apart

• Typically, the chin (submental) muscle is used

because it exhibits large differences during

sleep, aiding in the identification of stages

• Wake - high activity

• Sleep - lower activity

• REM sleep - paralysis of skeletal muscles

EMG AASM

Three electrodes should be placed

a. one in midline 1 cm above the inferior edge of the mandible

b. one 2 cm below the inferior edge of the mandible and 2 cm to the right of midline

c. one 2 cm below the inferior edge of the mandible and 2 cm to the left of midline

EMG

• REM versus NREM

• Snoring

• Swallowing

• Bruxism

• GERD

EOG

The eyeball is a dipole where the cornea is

positive and the retina is negative.

EOG

• The electrode close to the retina will pick up a

positive potential (down going wave).

V

EOG

+

V

V

Conjugate eye movements

Out of phase pen deflections

EOG Placement

Usually from ROC and LOC

(option of more channels in MSLT)

ROC:

One cm. superior and lateral from right outer canthus

LOC:

One cm. inferior and lateral from left outer canthus

EOG-AASM

• Nomenclature is different ROC now E2, LOC E1

• Reference electrodes placement (Additional ref

now mandatory)

• Reference electrodes nomenclature now M’s

• Alternative electrodes

Recommended EOG - AASM

• E1-M2

E1 is placed 1 cm inferior to the left outer

canthus

• E2-M1

E2 is placed 1 cm superior to the right outer

canthus

Alternative EOG -AASM

• E1-Fpz

E1 is placed 1 cm inferior and 1cm lateral

to the outer canthus of the left eye

• E2-Fpz

E2 is placed 1 cm inferior and 1cm lateral

to the outer canthus of the right eye

SEMs and REMs

• SEMs

initial deflection usually > 500msec

(usually more than 2 seconds in duration)

• REMs

initial deflection usually < 500msec

(usually less than 1 second in duration)

EOG• EOG records voltage changes caused by

eye movement; EOG changes with sleep

stage

• Wake: random, high amplitude:

• Stage 1: slow rolling:

• REM: very flat with occasional rapid eye

movements:

ARTIFACTS

• Eye movements should be out of phase

• K-complexes should be in-phase

• Channels should not block

– 60 Hz

– Muscle tension

– Electrode popping

– ECG

Questions ?