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Sleep Technology. An Overview of Polysomnography and the Roles and Responsibilities of the Sleep Technologist.
Sleep Technology An Overview of Polysomnography and the Roles and Responsibilities of the Sleep Technologist
Everybody was excited, except the fat boy, and he slept as soundly as if the roaring of cannon were his ordinary lullaby… “Sleep!” said the old gentleman, “he’s always asleep. Goes on errands fast asleep, and snores as he waits at table.” Charles Dickens The Posthumous Papers of the Pickwick Club 1884
Sleep Disorders are Common: • Over 80 different types of sleep disorders have been identified. • About one-half of adults in the U.S. experienced a sleep problem a few nights per week or more during the past year. • More than one-half of the adults surveyed report having experienced one or more symptoms of insomnia a few nights per week or more within the past year. • Obstructive Sleep Apnea symptoms in occur in 1 out of every 10 people. • Only one-third of adults say they get at least the recommended 8 hours or more of sleep per night during the work week • More than one-third of U.S. adults report snoring a few nights per week or more within the past year. • A sizable proportion of adults (43%) report that they are so sleepy during the day that it interferes with their daily activities a few days per month or more; and, one out of five experience this level of daytime sleepiness at least a few days per week or more.
Sleep Disorders are Serious: • Chronic insomniacs report decreased quality of life, memory and attention problems, decreased physical health. • About one-half of adults in the U.S. report driving while drowsy in the past year; nearly one out of five (17%) have actually dozed off while driving. • Total estimated annual costs of sleep disorders in U.S. $15.9 billion. (NCSDR)
Sleep Disorders are Treatable: • Multiple successful treatment modalities exist, including pharmacotherapy, oral appliances, surgical intervention, behavioral therapy, and continuous positive airway pressure.
Sleep Disorders:Conceptual Framework Insufficient Sleep (Sleep Deprivation) Fragmented Sleep (Sleep Disruption) Excessive Daytime Somnolence Primary Disorders of EDS
Assessing Excessive Daytime Sleepiness • Differentiate sleepiness vs fatigue • Subjective perception of sleep tendency, especially in low stimulus conditions • Sleepiness rating scales (subjective): • Epworth Sleepiness Scale (ESS) – most common • Stanford Sleepiness Scale (SSS) • Sleep-Wake Activity Inventory (SWAI) • Objective measure of EDS – Multiple Sleep Latency Test (MSLT) and Maintenance of Wakefulness Test (MWT)
Sleep Disorders:Clinical Impact Excessive Daytime Somnolence Neurobehavioral Deficits Performance Deficits Increased Morbidity/Mortality Decreased Quality of Life
Medical-psychiatric sleep disorders Medical Sleep-related asthma COPD G-E reflux Pain related Medication related Psychiatric Depression or panic disorder Neurological Sleep-related epilepsy Others Restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) Dyssomnias - disorders of initiating or maintaining sleep Circadian rhythm disorders/shiftwork Narcolepsy Idiopathic hypersomnia Inadequate sleep hygiene Sleep-related respiratory disorders OSAHS, CSAHS, Cheyne-Stokes, periodic breathing Upper airway resistance syndrome Parasomnias Disorders of arousal Disorders of sleep-wake transition REM behavior disorder Nightmares Rhythmic movement disorder Bruxism Sleep Disorders:EtiologicFramework/ Clinical Disorders
Evaluating Sleep Disorders • Overnight Polysomnogram (PSG) • Split Night Study • Multiple sleep latency testing (MSLT) • Maintenance of wakefulness test (MWT) • Limited-Channel PSG (pediatrics) • Unattended (portable) PSG
Bio-electric Signals: EOG - Electrooculogram EEG -Electroencephalogram EMG - Submental Electromyogram EKG - Electrocardiogram Transduced Signals: Tracheal Noise Nasal and oral airflow Thoracic and abdominal respiratory effort Pulse oximetry Video (body position) limb movements via EMG end-tidal CO2, transcutaneous CO2 Esophageal pH CPAP and BiLevel outputs The Polysomnogram: What’s Recorded
Electrodes Preps and Gels Lead wires Airflow sensors Respiratory effort Misc. Sensors Snoring/mike/body position/motion Amplifiers Headbox Software Oximeters pH meters Audiovisual PAP equipment Types of Equipment
Patient Set-up Components • Sleep History • Pre-Sleep Questionnaires • Electrode and Sensor Placement • Equipment Set-up and Calibration • Biocalibrations • Patient Monitoring • Troubleshooting • Reduce anxiety !!!
The International 10-20 System • The International 10-20 System of electrode placement is the most widely used method to describe the location of scalp electrodes. • The 10-20 system is based on the relationship between the location of an electrode and the underlying area of cerebral cortex. • Each site has a letter (to identify the lobe) and a number or another letter to identify the hemisphere location.
The International 10-20 System • The letters used are: "F" - Frontal lobe, "T" - Temporal lobe , "C" - Central lobe , "P" - Parietal lobe, "O" - Occipital lobe. (Note: There is no central lobe in the cerebral cortex. "C" is just used for identification purposes only.) • Even numbers (2, 4, 6, 8) refer to the right hemisphere and odd numbers (1, 3, 5, 7) refer to the left hemisphere. "Z" refers to an electrode placed on the midline. The smaller the number, the closer the position to the midline.
The International 10-20 System • "Fp" stands for Front polar. "Nasion" is the point between the forehead and nose. "Inion" is the bump at the back of the skull. • The "10" and ""20" (10-20 system) refer to the 10% and 20% interelectrode distance.
Electrode Placement for PSG • EEG electrode placement for sleep studies are usually limited to C4, C3, A1, A2, O1, O2, LOC, ROC, and chin EMG. • EEG, EOG, and EMG electrodes are necessary for staging sleep.
Signals: How we see them • Signals from the patient are amplified using the sensitivity setting and are filtered with: • High frequency filter (HFF). • Low frequency filter (LFF). • Time constant (TC). • Filters reduce unwanted activity.
WAVEFORM VOCABULARY • peak / crest - the highest point of a portion of a wave before it begins to decrease • trough - the lowest portion of a wave • rest - the horizontal line that would go through the center of a wave • amplitude - the 'height' of the wave from either the crest or trough to the rest. • cycle - from one point on a wave to its corresponding point as the wave cycle repeats (for example, from one trough to the next) • frequency - the number of cycles passing by a given point in one second
EEG MEASUREMENT AND CLASSIFICATION • Frequency - cycles/second (Hz) • Amplitude (microvolts) • Presence of sleep-specific waveforms: • Vertex Sharp Wave • Sleep Spindle, K complex • “Sawtooth” wave Defined by duration and/or morphology
Sleep Scoring • All sleep recording studies follow the same guidelines : • Recording speed : 10 mm/sec. • One page = 300 mm. • Epoch = 30 seconds. • One minute = two epochs.
PSG Components - Summary • Bio-electrical and transduced signals are transmitted, amplified, and filtered. • Signals are combined (PSG) in a montage. • Recording is divided into epochs (30 sec) • Each epoch is assigned a sleep stage. • The recording is analyzed for events.
Alpha Activity • Alpha EEG: 8-13 cps. • Alpha: occipital region • Alpha: crescendo-decrescendo appearance • Decrease in frequency occurs with aging
Awake • >50% of each epoch contains alpha activity. • Slow rolling eye movements or eye blinks will be seen in the EOG channels • Relatively high submental EMG muscle tone
Theta Activity • A frequency of 3-7 cps. • Produced in the central vertex region • No amplitude criteria for theta • The most common sleep frequency
Stage WakeEyes Closed vs. Eyes Open Eyes open
Stage 1 • > 50% of the epoch contains theta activity (3-7 cps.) There may be alpha activity within <50% of the epoch. • Slow rolling eye movements in the EOG channels • Relatively high submental EMG tone.
K Complexes • Sharp, slow waves, with a negative then positive deflection • No amplitude criteria • Duration must be at least .5 seconds • Predominantly central-vertex in origin • Indicative of stage 2 sleep Sleep Spindles • Sleep Spindle - 12-14 cps. • Central - vertex region • >.5 to 2-3 seconds in duration • .5 second spindles - 6-7 cycles • Indicative of stage 2 sleep
Stage 2 • Background EEG is Theta (3-7 cps.) • K-Complexes and Spindles occur episodically • Mirrored EEG in the EOG leads • High tonic submental EMG
Delta Activity • Sleep Delta Activity - frequency of .5-2 cps. • Clinical EEG - frequency of > .5-4 cps. • Seen predominantly in the frontal region • Delta Activity - amplitude of > 75mn Delta EEG Activity (zoomed in 4 times larger than normal)
Stage 3 Read through the noise 75mn 1 sec. • 20% to 50% of each epoch and must contain Delta Activity • EOG channels will mirror Delta activity • Submental muscle tone may be slightly reduced
Stage 4 75mn • >50 of the epoch will have scorable Delta EEG activity • The EOG leads will mirror all of the Delta EEG Activity • Submental EMG activity will be slightly reduced from that of light sleep
Stage REM • Rapid eye movements • Mixed frequency EEG • Low tonic submental EMG
Stage REM: Phasic Twitching • Very short muscle twitches that normally occur in REM Sleep • May occur in the inner ear, genioglossal, limb, and facial muscles The arrows are pointing to Phasic Twitching
Sawtooth Pattern • Jagged evenly formed EEG pattern seen usually in the vertex region • Seen predominantly in REM
Sleep Architecture • During sleep, we move through the various stages in a general pattern. • We have sleep cycles that include at least one NREM stage and one REM stage and last from 90 to 110 minutes. • During a night's sleep, the typical young adult experiences four to six sleep cycles, which change in composition as the night progresses. • REM: 25% • NREM: 75%- Stage 1: 5%- Stage 2: 45%- Stage 3: 12%- Stage 4: 13% • In the first third of the night, delta sleep stages are longer, and REM stages are shorter. • In the last third of the night, delta sleep usually decreases from the NREM portion of the cycle, and REM sleep stages last longer.
Sleep Architecture (cont’d) • A typical sleeper's first sleep cycle moves from wakefulness through stages 1, 2, 3, and 4, consecutively. • Then the sleeper moves back into stage 2 sleep and then into REM sleep. • The conclusion of the REM stage ends the first sleep cycle. • This first cycle usually lasts about 70 to 100 minutes, typically the shortest of the cycles. • This example is not absolute, but it does represent the norm. • REM: 25% • NREM: 75%- Stage 1: 5%- Stage 2: 45%- Stage 3: 12%- Stage 4: 13%
EKG Airflow Thoracic effort Abd. effort SpO2 Exhale Airway obstructs Airway opens Effort gradually increases Inhale Paradoxing Paradoxing Ends Blood oxygen levels reduce to < 3% of basline value • Obstructive Apnea A complete blockage of the airway (>10 seconds) despite efforts to breath. Notice the effort gradually increasing ending in airway opening.
Exhale Airflow reduction Inhale > effort with paradox Paradox ends SpO2 desaturation Hypopnea: This is a hypopneic event. The airflow signal is reduced by approximately 50% during this event for at least 10 seconds. The criteria for classifying hypopneas can vary from lab to lab.
ECG Airflow Thor. Effort Abd. Effort SpO2 Central Apnea: These are central apneas (2) with minimal oxygen desaturation. The criteria for central apnea is no effort and no airflow for at least 10 seconds.
EKG Airflow Thoracic Effort Abdominal Effort SAO2 Mixed Apnea
OSAHS Treatment Options • CPAP (most common) • Bi-Level • Region specific surgery • Tracheostomy • Non-surgical alternatives • behavioral modification • pharmaceutical • mechanical (dental devices)
PAP TITRATION GOALS • Eliminate Apnea • Eliminate Hypopnea • Eliminate Snoring • Eliminate Desaturation • Eliminate Arousals • Increase Compliance
End of Test Components • Post – Study Biocalibrations • Electrode and Sensor Removal • Post-Sleep Questionnaires • Equipment Cleaning • Documentation