PSG Mod1 Notes PDF

PSG MOD1 NOTES Module 1 Concepts and principles of polysomnography POLYSOMNOGRAPHIC RECORDING TECHNIQUE POLYSOMNOGRAPHY PSG records multiple physiological characteristics simultaneously during sleep. Assesses wakefulness and sleep stages, respiration, cardiopulmonary function, and body movements...

PSG MOD1 NOTES Module 1 Concepts and principles of polysomnography POLYSOMNOGRAPHIC RECORDING TECHNIQUE POLYSOMNOGRAPHY PSG records multiple physiological characteristics simultaneously during sleep. Assesses wakefulness and sleep stages, respiration, cardiopulmonary function, and body movements. Electroencephalography (EEG), electro-oculography (EOG), and chin muscle electromyography (EMG) channels are used to stage sleep. Airflow and respiratory effort channels Finger pulse oximetry channel C-flow channel provides the airflow signal, and CPAP pressure is continuously adjusted during the night to eliminate respiratory events. Limb EMG channels A single-channel electrocardiography (ECG) channel Snore channel are part of the typical PSG setup Video and audio recording PES – intraesophageal pressure Esophageal pH Penile tumescence PSG: PATIENT PREPARATION The goal of the PSG study is to recreate a typical night’s sleep. Simulate an ideal bedroom setting. Replicate familiar sleeping sleeping environment. Patients ’usual sleep schedule should be taken into account. The technician should have: Basic understanding of the PSG equipment Knowledge of important sleep disorders Know the indication why the sleep study was requested Questionnaires and clinical summary help in decision making Technician should also be vigilant for artifacts PSG: LABORATORY ENVIRONMENT Simultaneous video and audio recording to monitor behavior during sleep Control room with remote functions Intercom should be available Able to document the nature of any abnormal behavior TECHNICAL CONSIDERATIONS AND PSG EQUIPMENT Biological signals are of very small amplitude Amplified Filtered High-frequency filters (low-pass) Low-frequency filters (high-pass) High-frequency filters (low-pass) decreasing the high-frequency filter from 70 Hz to 35 Hz may eliminate faster-frequency artifacts like muscle artifact Low-frequency filters (high-pass) increasing the low-frequency filter from 0.3 Hz to 1 Hz may attenuate slower-frequency artifacts like sweat artifact. 60-Hz notch filter – attenuates the main frequency Differential amplifier Common mode rejection ratio – ideally this ratio must not exceed 1000 to 1 Alternating current amplifier Record physiological characteristics showing high frequencies (EEG, EOG, EMG, ECG) Direct current amplifier – have no low frequency filters and used to record potentials with slow frequencies Pulse oximeter output pH meter output CPAP pressure changes Intraesophageal pressure readings Standard speed for recording traditional PSG is 10 mm/sec. Each monitor screen is a 30-second epoch. Standard speed for EEG reading is 30 mm/sec 60-second epoch or more is used to better visualize respiratory events ELECTROENCEPHALOGRAM EEG recording – distinguish between wakefulness and various stages of sleep. Minimum of three channels (F4-M1, C4-M1, O2-M1) – right hemisphere with reference over the contralateral mastoid. Backup electrodes over the left hemisphere (F3-M2, C3-M2, O1-M2) – referenced over the contralateral mastoid. Dominant rhythm in wakefulness – alpha waves best seen occipital leads – posterior Major sleep architecture (vertex waves, sleep spindles, and K complexes) – best seen in frontal and central leads ELECTRO-OCULOGRAPHY EOG recording is crucial to staging sleep accurately E1 (1 cm below the left outer canthus) E2 (placed 1 cm above the right outer canthus) Eye is an electric dipole, with relative positivity at the cornea and a relative negativity at the retina.  Eye blinks are conjugate vertical movements – seen in wakefulness Slow lateral eye movements - defined as conjugate, sinusoidal, regular eye movements REM sleep – rapid eye movement occur in bursts seen in all directions (horizontal, oblique, and vertical REM density - frequency with which bursts of rapid eye movements occur in REM sleep ELECTROMYOGRAPHY Provide important physiological characteristics that help determine sleep stage Aide in the diagnosis of parasomnias PSG consists of chin EMG channels recording activity from the mentalis and submental muscles Bilateral leg EMG channels recording activity from the tibialis anterior muscles. EMG tone is progressively diminishing through NREM to its minimum point and almost absent in REM sleep. Lower-limb EMG – record limb movements in patients with periodic limb movement in sleep PLMS – seen in 80% of patients with RLS – restless leg syndrome PLMS – seen in variety of sleep disorders (RBD and narcolepsy) PLMS – occurs with respiratory events as part of OSA. Multiple muscle montage ELECTROCARDIOGRAPHY PSG generally includes a single channel of ECG Detects bradytachyarrhythmias Reports cardiac rhythm abnormalities. RESPIRATORY MONITORING TECHNIQUE RECORDING OF RESPIRATORY EFFORT INTRAESOPHAGEAL PRESSURE MONITORING Considered as gold standard Not routinely done – discomfort and technical skill Placing a nasogastric balloon-tipped catheter into the distal esophagus Normal pressure change – 5cm H2O Respiratory effort–related arousals (RERAs) RESPIRATORY INDUCTIVE PLETHYSMOGRAPHY RIP - measures changes in thoracoabdominal cross-sectional areas and the sum of these two compartment is proportional to airflow. Inductance refers to resistance to current flow PIEZOELECTRIC STRAIN GAUGES Peizoelectric strain gauges are used to record thoracic and abdominal and thus respiratory movements. Belts consist of a crystal that emits an electrical signal in response to changes in length or pressure. MEASUREMENT OF AIRFLOW ORONASAL TEMPERATURE MONITORING Thermistor – consisting of wires records changes in electrical resistance Thermocouple – consisting of dissimilar metals (copper and constantan) register changes in voltage that result from this temperature variation. Not as sensitive as nasal pressure transducer for detecting airflow limitation – may miss hypopnea. NASAL PRESSURE MONITORING Nasal cannula is connected to a pressure-sensitive transducer, which measures this pressure difference. This alternating decrement and increment of nasal pressure produces electrical signals – indirectly register airflow Nasal pressure monitoring is more sensitive than thermal devices in detecting airflow limitation and hypopneas PNEUMOTACHOGRAPHY Excellent technique to measure quantitatively the tidal volume and direct airflow measurement EXPIRED CARBON DIOXIDE Capnography, or end-tidal CO2 (ETCO2), monitoring detects the expired carbon dioxide (CO2) level, which closely approximates intra-alveolar CO2. Capnography detects both airflow and the partial pressure of CO2 in alveoli useful in OSA Sleep hypoventilation Partial pressure of carbon dioxide in ABG – alternative Increase in CO2 in sleep by 10mmHg or more – sleep related hypoventilation. OXYGEN SATURATION Routinely measured noninvasively by finger pulse oximetry Reflects arterial oxyhemoglobin saturation – percentage of hemoglobin that is oxygenated PSG reports mention the time the patient spent with an Sao2 below 90% Patients with alveolar hypoventilation - have low baseline oxygen saturation, with worsening in the supine position or in REM sleep Sleep hypoxemia – patients with saturations 5min with the lowest SPO2 of 85% and below. ESOPHAGEAL PH MONITORING ESOPHAGEAL PH Specialized procedure and is not routinely done Patient is requested to swallow pH probe Detects nocturnal GERD – mistaken for sleep apnea or nocturnal angina because the patient may wake up choking or with severe chest pain as a result of acid eructation. BODY POSITION MONITORING Essential parameter to measure Many patients have sleep-disordered breathing exclusive to or worse in the supine position Need to capture supine sleep – supine REM sleep – important in CPAP to ensure the the pressure is optimum Most reliable technique is by visual analysis Use of DC electrodes employed – home study SNORING Monitored by microphone attached on patient neck No accepted grading system to quantify snoring In practice – technologist’s annotation during the study and the MDs review of the sound recorded – provide better estimation of the degree of snoring It also worthwhile to note the degree of snoring with the body position during sleep PSG CALIBRATION EQUIPMENT CALIBRATION Technician must perform all channel calibration Done by sending all known signal through all the amplifiers which are set to the same low and high frequency filter settings and sensitivities Appropriate filter settings and sensitivities are then set PHYSIOLOGICAL CALIBRATION TECHNICIAN EDUCATION Technicians should be trained to identify behavior suggesting seizures, postictal confusion, tongue biting, and transient paralysis. Technicians should be instructed to ensure that the camera (during a video-PSG) is focused on the patient during unusual behaviors or movements suspected to be seizures, parasomnias, or dream enactment. In all patients in whom there is suspicion of RBD or in whom complex movements suggesting dream enactment are noted, technicians must ask the patient about dream recall and document this in the chart. Technicians should be trained cardiopulmonary arrest Seizures during PSG monitoring Safety and precautions against injury in appropriate cases ENDING THE TESTING ENDING THE PSG Lights on is reported Equipment and physiological calibration should be performed again The patient is asked to fill out post study questionnaires PORTABLE MONITORING Type 1 study are the traditional attended in-laboratory Type 2 study require a minimum of seven channels, including EEG/EOG, chin EMG, ECG, oximetry, airflow, and respiratory effort channels - they permit sleep scoring, studies using type 2 devices can be attended or unattended. Type 3 studies (also called cardiopulmonary studies) have a minimum of four channels (airflow, respiratory effort, pulse oximetry, and ECG); these studies can be attended or unattended. Sleep scoring cannot be performed with these devices. Type 4 study is overnight ambulatory pulse oximetry (a single-channel device recording a single physiological parameter) DIGITAL POLYSOMNOGRAPHY Previously recorded data can be manipulated retrospectively, and changes can be applied to the filter settings, sensitivities, and monitor speeds Computerized PSG recording replaces paper and makes PSG paperless equipped with the ability to automatically score certain types of events based on patterns of recognition Disadvantage – incompatibility of recordings ARTIFACTS DURING PSG MONITORING PHYSIOLOGICAL ARTIFACTS Muscle artifact originating from the scalp muscles may obscure the EEG activities Movements of the head, eyes, tongue, mouth, and other body parts will produce movement artifacts Sweating may cause excessive baseline swaying, producing a very slow-frequency wave lasting for 1 to 3 seconds Respiratory artifact - distinguished from sweat artifact by its time-locked relationship with breathing Flow and respiratory channels artifact