Basics of Polysomnography Chitra Lal, MD, FCCP, FAASM

Assistant professor of Medicine, Pulmonary, Critical Care and Sleep,

MUSC, Charleston, SC

∗ Continuous and simultaneous recording of several physiologic variables during sleep

∗ EEG ∗ EOG ∗ EMG ∗ ECG ∗ Snoring ∗ Thoracic and abdominal movements ∗ SaO2 ∗ Airflow

Basics of Polysomnography

∗ Additional Channels : - End tidal Co2 (PetCo2) - Transcutaneous CO2 - PAP level - Esophageal pressure monitor - Additional EEG channels for nocturnal seizures - Video monitoring - Esophageal pH

Polysomnogram

∗ Diagnostic PSG ∗ PAP titration study ∗ Split night study

Types of Sleep Studies

Electroencephalography

∗ International 10-20 system (10% or 20% inter-electrode distance) ∗ Electrodes are identified by letters representing brain regions

and a numeric subscript representing side of the body ∗ F is Frontal ∗ O is occipital ∗ C is central ∗ M is mastoid ∗ Odd #’s are left side, even #’s are right side, z is midline ∗ AASM recommends F4M1, C4M1 and O2M1

Electro-oculography(EOG)

∗ Cornea is positively charged ∗ Retina is negatively charged ∗ EOG measures the potential difference (PD) (dipole)

between the two ∗ Positive voltage (downward deflection) is when the eye

moves towards an electrode and vice-versa ∗ AASM recommends E1M2 and E2M2 ∗ E1 is 1 cm below the left outer canthus ∗ E2 is 1 cm above the right outer canthus ∗ Conjugate eye movements cause out-of-phase deflections

EMG (chin)

∗ 3 EMG leads : - midline and 1 cm above the inferior edge of the mandible - 2 cm to the right of midline and 2 cm below the inferior edge of the mandible - 2 cm to the left of midline and 2 cm below the inferior edge of the mandible ∗ 1 cm electrode distances for children ∗ Derivation consists of either electrode below the mandible

referenced to the electrode above the mandible ∗ Additional masseter electrodes for Bruxism

ECG

∗ Single modified lead II : electrodes below right clavicle near sternum and over left lateral chest wall

Airflow

∗ Apneas are scored by Oronasal thermistor (recommended) or nasal air pressure transducer (alternative)

∗ Hypopneas are scored by nasal air pressure transducer(recommended) or Oronasal thermistor (alternative)

∗ Respiratory effort related arousals are scored by nasal air pressure transducer or respiratory effort

Airflow

∗ Oronasal thermistor measures temperature change with airflow, roughly quantitative measure

∗ Nasal pressure transducer measures subtle variations in airflow

Respiratory Effort

∗ Esophageal pressure monitoring (balloon measure, very uncomfortable, recommended by AASM)

∗ Surface diaphragmatic EMG ∗ Respiratory Inductance Plethysmography (RIP) :

calibrated volumetric measure for chest and abdominal wall excursion (AASM recommended)

∗ Strain guages : use mercury, now banned in hospitals ∗ Effort belts : piezo-crystal sensors

Ventilation

∗ Pulse oximetry ∗ PetCo2 (end tidal CO2) or transcutaneous Co2 in

children for alveolar hypoventilation ∗ Snoring is recorded with a microphone

EMG (anterior tibialis)

∗ Detects periodic limb movements of sleep (PLMS) ∗ Additional electrodes over the extensor digitorum

communis to detect RBD

Interpretation of PSG

∗ 30 second periods or epochs ∗ Paper speed of 10 mm/second ∗ Original scoring criteria per Rechtshaffen & Kales (R &

K), recently revised by AASM ∗ Majority of Epoch rule ∗ Each epoch is assigned a sleep stage

Wake

∗ Alpha rhythm over occipital region > 50% of epoch with eye closure, slow-rolling eye movements

∗ Open eyes wakefulness : beta rhythm, conjugate vertical eye blinks, reading eye movements

∗ High chin tone

Stages of Sleep

∗ N1 : Theta waves > 50% of epoch, slow-rolling eye movements, low chin tone, vertex waves (central region, < 0.5 seconds)

∗ N2 : K complexes and spindles, background theta rhythm, can have delta waves < 20% of epoch

∗ N3 : Delta waves > 20% of epoch ∗ REM sleep : REM’s, lowest chin tone, saw-tooth

waves, relatively low voltage, mixed frequency EEG

∗ Alpha rhythm is attenuated and Theta waves >50% of the epoch

∗ If no alpha rhythm is generated, stage N1 if: - Vertex waves are present - EEG is 4-7 Hz frequency, and ≥ 1 Hz slower then the background rhythm in stage W - Slow eye movements

Stage N1

∗ Score N2 (in absence of criteria for N3) if either/both occur in the first ½ of that epoch or in the last ½ of the previous epoch:

- K complex without associated arousal - Sleep spindles ∗ Continue staging N2 for epochs with low-amplitude,

mixed frequency EEG without K complexes/spindles, if they are preceded by epochs with K complexes without arousals/spindles

Stage N2

∗ End stage N2 when 1 of the following occurs: - transition to stage W, N3 or R - arousal -major body movement followed by slow eye movements without non-arousal associated K complexes/spindles

Stage N2

∗ Score R if ALL of the following are met: - Low-amplitude, mixed-frequency EEG - Low chin EMG tone - Rapid eye movements ∗ REM RULES: Continue staging R even in the absence

of rapid eye movements, if EEG is low-amplitude, mixed frequency, no K/spindles, and low chin tone

Stage R

∗ Stop staging R if: - transition to W or N3 - ↑ in chin tone - arousal/major body movement followed by slow eye movements - non-arousal associated K complex/spindle occurs

Stage R

∗ Movement or muscle artifact obscuring > ½ of the epoch, so that sleep stage cannot be determined

∗ If alpha for part of the epoch (even if < 1/2 of the epoch), stage it as W

∗ If no alpha is discernible, but W epoch precedes/follows it, stage it as W

∗ Otherwise, stage it as the epoch which follows it

Major Body Movement

http://www.google.com/url?sa=i&rct=j&q=major%20body%20movement%20on%20sleep%20study&source=images&cd=&cad=rja&docid=toltgmJa1ZVtxM&tbnid=3aavHuKBu24qVM:&ved=0CAUQjRw&url=http://www.readcube.com/articles/10.1038/nature04287?locale%3Den&ei=4SctUpK8Haf84APQrYCoCw&psig=AFQjCNGd4d7e0BkB3m6oO1SDnpJBE_AfoQ&ust=1378777388985602

∗ Abrupt shift of EEG frequency, including alpha and/or frequencies > 16 Hz (not spindles) which last for ≥ 3 seconds and are preceded by ≥ 10 seconds of sleep

∗ Arousal from REM sleep also requires a concurrent ↑ in chin tone for ≥ 1 seconds

Arousal

Arousal after respiratory event

∗ Significant leg movement (LM) definition: - Duration of LM between 0.5-10 seconds - ≥ 8 microvolts increase in EMG voltage above resting EMG ∗ PLM series: - ≥ 4 consecutive LM events - Duration between LM events between 5-90 seconds - if duration between LM events is < 5 seconds, count as 1 LM

Periodic Limb Movements of Sleep (PLMS)

Periodic Limb Movements of Sleep

∗ Apneas are scored by oronasal thermistor ∗ Hypopneas are scored by nasal pressure transducer ∗ During PAP titration, use PAP device flow signal to

score respiratory events ∗ Respiratory effort is scored by esophageal

manometry (gold standard) or thoracoabdominal RIP belts

Respiratory Rules

Hypopnea

∗ Peak signal excursion drops by ≥ 30% of pre-event baseline for ≥ 10 seconds with a ≥ 3% drop in oxygen saturation or arousal (current AASM recommended)

∗ Classification of hypopneas as obstructive or central is optional

Hypopnea

∗ Obstructive: - snoring - inspiratory flattening of flow signal - thoracoabdominal paradox

∗ Central: - absence of obstructive features

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Respiratory Effort Related Arousal (RERA)

∗ Sequence of breaths lasting ≥ 10 seconds with increasing respiratory effort or decreasing inspiratory flow followed by an arousal, and does not meet criteria for apnea/hypopnea

∗ ↑ paCO2 (or surrogate) to > 55 mm Hg for ≥ 10 minutes OR ∗ ≥ 10 mm Hg increase in paCO2 (or surrogate) during

sleep (compared to awake supine value) to > 50 mm Hg for ≥ 10 minutes

Hypoventilation

∗ ≥ 3 consecutive central apneas and/or central hypopneas separated by crescendo-decrescendo breathing with a cycle length of ≥ 40 seconds

OR ∗ ≥ 5 central apneas and/or central hypopneas per hour

of sleep with crescendo-decrescendo breathing over ≥ 2 hours of monitoring

Cheyne-Stokes Breathing

Cheyne-Stokes Breathing

∗ Lights out clock time (hr:min) ∗ Lights on clock time (hr:min) ∗ Total Sleep Time (TST) ∗ Total Recording Time (TRT; “lights out” to “lights on”

in min) ∗ Sleep latency (SL; lights out to first epoch of any

stage of sleep) ∗ REM latency (sleep onset to first epoch of REM sleep

in minutes)

Sleep Scoring Data

∗ Wake after sleep onset (WASO; TRT-SL-TST, in min) ∗ Percent sleep efficiency (TST/TRT X 100) ∗ Time in each stage in minutes ∗ Time in each stage/TST x 100 ∗ Arousal Index (ArI; # of arousals x 60/TST) ∗ Periodic limb movements of sleep index (PLMSI; PLMS x

60/TST) ∗ PLMS arousal index (PLMSArI; PLMS with arousals x

60/TST)

Sleep Scoring Data

∗ Apnea-Hypopnea Index (AHI; # of apneas + hypopneas x 60/TST)

∗ Respiratory Disturbance Index (RDI; RERA’s + apneas + hypopneas x 60/TST)

Sleep Scoring Data