RET 010: Introduction to Polysomnography Module 8 - Student Activity Sheet PDF

RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________...

RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Lesson title: Materials: FREQUENCY, VOLTAGE AND MORPHOLOGY OF SIGNALS II Book, pen and notebook Learning Targets: At the end of the module, students will be able to: References: Marshall, B., Robertson, B,. Carno, M-A. 1. Examine waveform components related to data analysis and (2017). Polysomnography for the Sleep interpretation. Technologist (11th ed.). St. Louis, MO: 2. Observe waveform patterns representative of changing Elsevier, Inc. sleep-related variables. 3. Adjust instrumentation controls for optimal recording quality. A. LESSON PREVIEW/REVIEW Introduction Hello, PHINMA Ed students! Welcome to RET 010: Introduction to Polysomnography. In today’s session, you are tasked to set expectations as you get oriented with what the subject is all about and to determine the nature of flexible learning. Before we begin with the formal course orientation, let’s pause and reflect by briefly answering the questions below: B.MAIN LESSON SIGNAL SAMPLING With digital acquisition systems, there are no paper or pens. Advanced signal acquisition theory is applied to take periodic samples of the continuous signal and store them. The samples are generally obtained at a fixed rate, called a sampling rate. The Nyquist-Shannon sampling theorem states that a digital copy of a band-limited signal can be completely reconstructed from samples made at a sampling rate faster than twice the bandwidth of the highest frequency of the original data To determine the optimal sampling rate, one must determine the highest frequency of the data and double it. Sampling at a frequency above this rate will facilitate a more accurate reconstruction of the signal, particularly when it is very fast. For example, if the highest frequency within the bandwidth of a signal is 100 Hz, it should be sampled at a rate faster than 200 Hz (samples per second). From those samples a digitized copy of the original signal can be completely reconstructed according to mathematical theory. In real- world application, the reconstructed signal is always only an approximation of the original, albeit a close approximation with adequate sampling rate. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ SIGNAL RECONSTRUCTION Reconstructing a signal is complicated by the fact that a special filter is required. A reconstruction filter captures the peaks of the signals at the given sample rate and, using an algorithm, extrapolates the data between samples turning the data into a smooth continuous signal similar to the original. If too few data points are sampled, reconstruction of the data may appear blunted or distorted. The AASM developed two levels of recommendations for sampling rates for use on PSG channels. The higher range settings significantly reduce the likelihood of signal aliasing Because sampling rate affects file size, each facility must determine whether the cost of additional storage space is outweighed by the benefit of obtaining higher data resolution SENSITIVITY AND GAIN Biopotentials from the brain are measured in microvolts (mV), which are 1000 times smaller than a millivolt and 1,000,000 times smaller than a volt. Biopotentials are assessed by the voltage, frequency, and morphology of the recorded signal. When an input signal of known voltage is applied to the amplifier to produce a deflection, the signal amplitude can be used to extrapolate the voltage responsible for other deflections. Likewise, if the recorder amplification settings are known, voltage can be determined. SENSITIVITY Sensitivity is a control on the polygraph used to increase or decrease the amplitude of recorded data. It has been defined as the ratio of input voltage to the output deflection. Although somewhat outdated, it is literally the amount of voltage or microunits of voltage (mV or mV), required to produce a 1-mm deflection or 1-cm deflection on the recorder. Despite adoption of gain for use with digital acquisition of data, some manufacturers continue to rely on the concept of sensitivity. Rather than expressing sensitivity in terms of microvolts per millimeter (μV/mm) or millivolts per centimeter (mV/cm), it may be defined in terms of divisions or some other scale more appropriate for a computer screen. The sensitivity setting is expressed in the units of mV/mm or voltage/deflection. Using a basic expression, it could be stated that sensitivity (S) 5 voltage (V)/ deflection (D), or S 5 V/D. GAIN Gain, which has largely replaced the sensitivity control for use in digital polysomnography, has been defined as the ratio of output deflection to input voltage. It is simply a multiplication factor that represents how many times the original signal that arose from the patient was amplified for visual display. To put gain into perspective, a typical setting for EEG is 20,000 times; the EEG signal is amplified 20,000 times for visual display on the recorder. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Both gain and sensitivity must be documented (with numerical values and units) at the recording start, each time there is a change to amplifier settings, and at the end of the PSG. COMMON MODE REJECTION The ideal differential amplifier generates an output that is purely the difference between two input signals. When artifact is superimposed on both inputs of a recording channel, the extraneous signal is called the common mode signal. When both inputs of a derivation are contaminated by artifact of identical phase and equal voltage, the like components of the signal will be eliminated. This characteristic of a differential amplifier is referred to as common mode rejection. Because input 2 is always subtracted from input 1, signals of identical phase, polarity, amplitude, and frequency that reach both inputs, such as 60 Hz activity from electrical leakage current, will be subtracted before reaching the recorder output. The common mode rejection ratio (CMRR) is defined as the differential gain divided by the com- mon mode gain. The higher the CMRR, the more efficient the amplifier and less common mode signal reaches the output. This allows optimal recording of the pure bioelectric signal with minimal artifact. Because impedance is the resistance to an AC signal, as it increases the amplitude of the signal is reduced. The absence of an effective patient ground electrode can also reduce the effectiveness of common mode rejection. The patient ground electrode establishes a universal reference for all scalp potentials. It is the baseline at which the differential amplifier be- gins the potential difference calculation. Without this reference point, identical electrical signals can be excluded from the differential calculation. The patient ground electrode does nothing to protect the patient from electrical shock, and when electrical safety practices are followed, it poses no appreciable risk to the patient. A patent ground wire within the recorder power cord and its connection to the electrical outlet ground, the building ground, and the earth ground does protect the patient from exposure to electricity. AMPLIFIER FILTERS THE LOW-FREQUENCY FILTER AND DECAY TIME CONSTANT Only a limited number of frequencies are of interest to polysomnography. To concentrate on these specific frequencies of interest, filters are employed to isolate them. An analog filter is made of resistors and capacitors, which slow down the time a signal has to move from peak to baseline. A digital filter takes the digitized data and passes it through programmed microchips, where algorithms attenuate signals be- low the filter setting, also referred to as the cut off frequency. Filters, therefore, change the characteristics of the original signal. Ideal digital filters attenuate data in a manner similar to that of analog filters. Low-Frequency Filter (LFF) This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The low-frequency filter (LFF) is also known as the high-pass filter, because it allows signals above the cutoff frequency to pass through. A LFF attenuates components below the filter setting and preserves those above it. The LFF is particularly useful when the signal of interest rides on an unwanted DC level. The LFF is useful on EEG channels for attenuating signals below delta wave activity such as sweat artifact and respiratory artifact. Sweat artifact causes the signal baseline to slowly move up. Increasing the LFF will attenuate this wandering baseline, but care must be taken not to attenuate signals of interest The AASM recommends an LFF setting of 0.3 Hz on EEG channels to ensure lower delta wave frequencies are preserved When the baseline EEG signal becomes contaminated with high amplitude, slow-wave artifact, it is most likely due to sweat, movement, or a combination of the two. If the issue is the result of sweat artifact, lowering the room temperature is the first step toward resolving this issue. If the artifact is aligned with respiratory channel excursion, multiple items may be moving in synch with breathing and may be responsible for the artifact Decay Time Constant (TC) A time constant (TC), more specifically the decay time constant or fall TC, is defined as the time it takes, in seconds, for a square wave to decay to 37% of its original amplitude. The LFF and the decay TC are recorder controls used for the same purpose. One instrument may have an LFF control on the amplifier system, whereas an instrument from another manufacturer may use a TC control instead. For this reason, the technologist must possess a functional understanding of the relationship between these controls. The effects of various low-frequency filter settings and the decay time constant associated with each are shown in the right side. Displays the effect of different LFF settings on sine waves recorded at various frequencies. Here there is no DC channel. The HFF, LFF, and TC settings are identical to those used to record the bottom four channels in the previous example. The sine-wave input signals, applied to each amplifier at a frequency of 0.3 Hz, 1 Hz, 3 Hz, 10 Hz, and 30 Hz, were either allowed to pass through the amplifier because of its LFF setting, or the filter attenuated the signal by varying degrees. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The shorter the TC, the more slow frequencies will be attenuated. o This is very important because while attempting to reduce slow frequency sweat or respiratory artifact, delta waves, which are similar in frequency, could also be attenuated. Attenuation of delta waves reduces the amount of stage N3 sleep on the study that can be scored. It can be helpful for the technologist to think about the inverse relationship that exists between the LFF and the fall TC, because frequency is something that can easily be counted. o As one goes up, the other goes down. o A relatively lower LFF corresponds to a relatively longer TC as measured in seconds. A higher LFF setting corresponds to a shorter TC. THE HIGH-FREQUENCY FILTER The high-frequency filter (HFF) is also known as a low-pass filter. It attenuates signal components with a frequency approaching, meeting, and surpassing the cut-off frequency, and preserves or only nominally attenuates the signal components with a frequency below the filter setting These data, or the majority of the signal amplitude, are allowed to pass through the filter as amplifier output. Setting the HFF too close to 35 Hz can attenuate EEG abnormalities such as sharps and spikes. Muscle twitches from arousals, teeth grinding, and body movements can also be difficult to distinguish from brain activity For this reason, applying an HFF setting of 60 Hz or 70 Hz should be considered when epileptiform activity is expected or suspected Spikes are defined as having a 20- to 70-ms duration, which equals 14 to 50 Hz. An HFF setting of 35 Hz will certainly attenuate frequencies within this range below the filter setting, but it will also result in attenuation of the faster frequencies to some degree. The HFF setting of 70 Hz will not have a negative effect on the recording of epileptiform spikes. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Reducing the HFF in response to artifact is not often the best response. The best solution may be reapplication of electrodes or a derivation change to preserve the integrity of the recording. The HFF imposes a rise time constant on the recording similar to the decay TC of the LFF. The rise TC of the HFF is defined as the time it takes for the signal to attain 63% of its peak amplitude. The HFF rise TC is responsible for the dampened or peaked morphology of data. A higher HFF setting allows fast components to pass and results in a more peaked output. A lower HFF setting attenuates fast components and results in a more dampened or rounded output signal. When signal frequency is below but approaching the HFF setting, the signal will be attenuated to somewhere between greater than 80% and less than 100% of its original amplitude. THE 60-Hz FILTER Although modern laboratories and equipment are well grounded, shielded, and isolated, it is difficult to completely eliminate 60-Hz signals from the PSG. Because EEG, as an example, is typically recorded at a gain setting of 20,000, any artifact, including line noise, is also amplified 20,000 times on the EEG channel. When the slightest hint of 60-Hz noise contaminates the recording, once it is amplified it may obscure the channel. A device used to reduce power line signals obscuring EEG recordings is the 60-Hz filter or notch filter. o This filter attenuates frequencies of 58 to 62 Hz. The attenuation curve is very sharp with a notch in the middle. o As the signal frequency passes 58 Hz and approaches 60 Hz, it is reduced to almost 0% of the original amplitude. o When the signal frequency in- creases above 62 Hz, it returns to its original amplitude. Because signals close to the notch can also be reduced, the notch filter should only be employed when absolutely necessary to prevent unwanted attenuation of signals of interest. Attenuation imposed by the LFF setting of 0.3 Hz and the HFF setting of 70 Hz as input frequency progressively increases from 0.1 Hz to 100 H A frequency response curve from which signal attenuation can be estimated when amplifier settings and input signal amplitude are known. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The technologist should become proficient at equipment troubleshooting and use his or her skills rather than simply applying a filter that distorts the data being acquired. Artifacts and their resolution are thoroughly covered in a later chapter. Obviously the effects of a 60-Hz filter along with a 70-Hz HFF are profound. When the HFF is set too low, even 35 Hz, distortion of fast-frequency signals becomes even more prominent, making data less reliable. In a worst-case scenario, signals originating from the body can be distorted to the point that they no longer appear to be of physiological origin. DIGITAL FILTERING Digital filtering offers the advantage of changing filter settings during the scoring and review of the sleep study. Widening the bandwidth of the bioelectrical signal on the tracing can reveal information not otherwise noticed by the recording technologist. Digital filters produce less peak distortion backward (LFF) and forward (HFF), respectively. There are three types of digital filters: o the finite impulse response (FIR) o the infinite impulse response, and o the fast Fourier transform. o Most PSG systems use the FIR, which averages the amplitude of adjacent digitized signal samples. o The FIR creates a wider HFF band-width, thereby attenuating signals of lower frequency. FREQUENCY RESPONSE Filters act to attenuate signal components outside of the set cutoff frequency and maintain the signal com- ponents inside of the cutoff frequency. All filters have a cutoff frequency, which is by definition the frequency at which the output declines to 80% of the original amplitude. This is also known as the 3 dB point because a voltage ratio of 80%, expressed in decibels, is –3 dB or 3 dB down in amplitude. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ In monitoring bioelectrical data, such as EEG, the convention is that the signal is attenuated to 80% at the cut-off frequency. However, in electrical engineering the signal is attenuated by 30% at the cut-off frequency. That is 10% for each decibel up or down. In reality, the 80% amplitude convention is only followed by certain equipment manufacturers ADDITIONAL TESTING EQUIPMENT AND CONSIDERATIONS TRANSDUCED SIGNALS Signals representing respiratory effort, temperature, pressure, and other mechanical functions are transduced into electrical signals capable of interfacing with the polygraph. A polygraph records the electrical difference between two input signals, or in the case of ancillary devices, the voltage of a single input. However, much of what is obtained during a sleep study is not directly related to the rising and falling of electrical potentials recorded directly from the body’s surface. Instead, mechanical activity, like that associated with breathing, must be converted into a signal that can be interfaced with the acquisition system. A transducer is a device that converts one form of energy into another. For polysomnography, a transducer converts a mechanical signal into an electrical signal. Thermal sensors used for obtaining an airflow signal actually measure the relative change in temperature that occurs as cool room air is pulled across the sensor and then warm air is exhaled over it. This relative temperature change results in a difference in voltage that travels through conductors to the polygraph for display in a sinusoidal signal used to represent airflow. Likewise, the nasal pressure airflow signal is derived from pressure changes exerted on the opening of a cannula that resides at the nares during inspiration and exhalation. The other end of the cannula, or tube, is attached to a pressure transducer that converts the pressure changes into an electrical signal. Similarly, when a cannula is placed in the esophagus for esophageal manometry, the changes in intrathoracic pressure exerted on the esophagus and the tube during breathing are converted by a pressure transducer into a usable signal. Respiratory inductance plethysmography belts and older sensors using piezo crystal technology transduce movement or pressure on a sensor, respectively, into an electrical signal for display on the recording. Conversion of a mechanical to electrical signal can be found in other common sleep testing devices, including snore sensors and snore microphones, position sensors, and movement sensors. ANCILLARY EQUIPMENT Free-standing devices capable of providing diagnostic information when used alone are often interfaced with the sleep study recorder to complement other measures being obtained. When devices are interfaced with the polygraph to supplement diagnostic or therapeutic data, these machines are collectively referred to as ancillary equipment or devices Ancillary devices such as oximeters and capnometers provide the final complement of information re- corded during a sleep study. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ These free-standing machines and signal transducers, along with the electrodes that record bioelectric signals directly from the surface of the body, are connected to polygraph amplifiers for simultaneous recording. o A pulse oximeter provides oxyhemoglobin saturation data and a capnometer is often employed to continuously monitor the patient’s CO2. o A positive airway pressure (PAP) device is used to deliver continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BPAP). A transduced airflow signal is derived from the PAP device during the therapeutic phase of testing Most ancillary devices communicate with the acquisition system using low-voltage signal such as 0-1 V DC. THE POLYSOMNOGRAPH A standard sleep study is segmented into 30-second increments called epochs, each of which must be assigned a sleep stage score by either the recording or scoring technologist. The 30-second epoch recorded on paper required a paper speed of 10 mm/s. For clinical EEG, a 10-second epoch is used. When recorded on paper, this requires a paper speed of 30 mm/s. Standard ECG paper speed is 25 mm/s. When comparing data from an ECG reference, PSG data will be compressed by 2.5 times In addition to sleep-stage identification the scoring technologist must identify, quantify, and tabulate occurrences such as EEG arousals, sleep-disordered breathing events, and EMG changes that are possible signs of a disorder. The tabulated data are organized into a report to be interpreted by a sleep medicine physician. These data are used alongside clinical evaluation of the patient with a possible sleep disorder to aid in diagnostic decision making and to determine the effectiveness of established therapy. If a therapeutic intervention, like CPAP or supplemental oxygen (O 2) is administered during the sleep study, the technologist must also report whether the intervention was effective. RECORDED DATA When preparing a patient for a sleep study, most technologists start with the head measurements, scalp preparation, and application of cephalic electrodes. Although a particular order is not crucial, eye movement and chin EMG electrodes may be placed on the face next, followed by ECG electrodes on the trunk and leg EMG electrodes. Next, respiratory airflow and effort sensors, a snoring microphone, and a nasal cannula connected to a pressure transducer are applied to the face, neck, and trunk. Finally, an oximeter probe is applied to a finger and a body position sensor is attached. THE ELECTROENCEPHALOGRAM (EEG) The EEG represents biopotentials from the brain as recorded at the scalp’s surface. They are the result of potential currents generated by networks of cortical cells. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ When these potential changes are recorded continuously, the frequency, duration, amplitude, and polarity of acquired data combine to create a visual pattern, which is consistent with wakefulness, the stages of sleep, and other findings. Many of the individual patterns and components of the EEG are assessed on a defined channel derived from electrodes overlying specific cortical areas. Because brain potentials are small, in the range of microvolts, potential fields are sampled to obtain a summation of potentials from many nerve cells underlying an exploring electrode. These signals are directed to the polygraph through a selector panel, which pairs two leads for input to the differential amplifiers. Groups of paired electrodes make up the montage, which determines which data are viewed on the channels of the tracing. THE ELECTROOCULOGRAM (EOG) Eye movements can be easily recorded because the retina at the back of the eye is negative with respect to the cornea at the front of the eye. As the eyes move, the potential difference between the EOG electrodes is recorded based on their placement in relation to the cornea and retina. Most commonly, one electrode is affixed 1 cm above the right outer canthus and one electrode is affixed 1 cm below the left outer canthus. Both electrodes are referenced to the M2 electrode for a right and left EOG channel. This configuration is designed to record vertical and horizontal eye movements. Electrodes placed precisely on the same horizontal plane will collect only horizontal and oblique eye movements. When the eye moves so that the cornea is in closer proximity to the electrode than the retina, a positive potential will be recorded as a downward deflection on the respective channel. When the eye moves so that the retina is closer to the electrode, a negative deflection will be generated. THE CHIN ELECTROMYOGRAM (EMG) Biopotentials from chin muscle activation are recorded from the skin’s surface as an EMG signal. Muscle tone in the submentalis decreases as the patient falls asleep, and is at its lowest during rapid eye movement sleep. o The submentalis muscle group consists of the genioglossus, and the hyoglossus and the palatoglossus. These muscles coordinate the control of the tongue and airway space. Three electrodes are placed to record chin EMG: one midline above the inferior edge of the mandible and two others 2 cm below the inferior edge of the mandible with one 2 cm to the right and one 2 cm to the left. When placed properly, the two lower electrodes lie directly over muscle that is activated by having the patient swallow. THE LIMB ELECTROMYOGRAM Bursts of muscle activity recorded from the anterior tibialis of each leg are used to identify periodic limb movements. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ This neurosensorimotor disorder causes frequent limb jerks, EEG arousals, and a reduction in the quality and quantity of sleep. Electrodes for recording leg EMG activity are placed 2-3 cm apart, longitudinally, along the belly of the anterior tibialis muscle group. Check for Understanding You will answer and rationalize this by yourself. This will be recorded as your quiz. One (1) point will be given to correct answer and another one (1) point for the correct ratio. Superimpositions or erasures in you answer/ratio is not allowed. You are given 20 minutes for this activity. 1. A small device constructed of conductive metal for the measurement of bioelectrical signals is known as a (an): a. Electrode b. Amplifier c. Montage d. Meter This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 2. An impedance meter measures: a. Polarity b. Frequency c. Resistance d. Duration ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 3. The minimizing of signals common to input 1 and input 2 is known as: a. Frequency b. Polarity c. Common mode rejection d. Sampling rate ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 4. Which of the following rejects common signals recorded at input 1 and input 2? a. A differential amplifier b. A common mode amplifier c. A referential amplifier d. A WYSIWYG amplifier ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 5. A listing of derivations defines which of the following? a. Sampling rate b. Montage c. GIGO d. Channels ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ 6. ____________ is a control on the polygraph used to increase or decrease the amplitude of recorded data. It has been defined as the ratio of input voltage to the output deflection. ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 7. A time constant (TC), more specifically the _____________ or fall TC, is defined as the time it takes, in seconds, for a square wave to decay to 37% of its original amplitude. ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 8. A higher LFF setting corresponds to a__________. ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 9. The____________ , the more slow frequencies will be attenuated. ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 10. The low-frequency filter (LFF) is also known as the ___________, because it allows signals above the cutoff frequency to pass through. ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ C. LESSON WRAP-UP SIGNAL SAMPLING With digital acquisition systems, there are no paper or pens. Advanced signal acquisition theory is applied to take periodic samples of the continuous signal and store them. The samples are generally obtained at a fixed rate, called a sampling rate. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #8 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The Nyquist-Shannon sampling theorem states that a digital copy of a band-limited signal can be completely reconstructed from samples made at a sampling rate faster than twice the bandwidth of the highest frequency of the original data To determine the optimal sampling rate, one must determine the highest frequency of the data and double it. Sampling at a frequency above this rate will facilitate a more accurate reconstruction of the signal, particularly when it is very fast. For example, if the highest frequency within the bandwidth of a signal is 100 Hz, it should be sampled at a rate faster than 200 Hz (samples per second). From those samples a digitized copy of the original signal can be completely reconstructed according to mathematical theory. In real- world application, the reconstructed signal is always only an approximation of the original, albeit a close approximation with adequate sampling rate. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Lesson title: Materials: BIOELECTRIC SIGNALS OF INTEREST IN SLEEP MEDICINE Book, pen and notebook Learning Targets: At the end of the module, students will be able to: References: Marshall, B., Robertson, B,. Carno, M-A. 1. Describe the EEG and its importance to the study of sleep. (2017). Polysomnography for the Sleep 2. Explain waveforms of interest to the sleep technologist. Technologist (11th ed.). St. Louis, MO: 3. Identify correct electrode placement for EOG monitoring. Elsevier, Inc. 4. Recognize how eye movements display on the polysomnogram. 5. Differentiate slow eye movements, rapid eye movements, and blinks. 6. Describe characteristics of both the chin EMG and leg EMG 7. Identify key characteristics of each sleep stage. A. LESSON PREVIEW/REVIEW Introduction Hello, PHINMA Ed students! Welcome to RET 010: Introduction to Polysomnography. In today’s session, you are tasked to set expectations as you get oriented with what the subject is all about and to determine the nature of flexible learning. Before we begin with the formal course orientation, let’s pause and reflect by briefly answering the questions below: B.MAIN LESSON INTRODUCTION Recalling that a nerve cell, or neuron, is simply a highly specialized animal cell, at one end, the dendrites receive signals from other cells in the form of chemical mediators. On the opposite end of the neuron are the axon terminals, which release chemical mediators across the synapse if the signal is propagated through the cell body and across the axon. These structures lie between the dendrites and the axon terminals. Through the normal function of neurons and other cells of the body, bioelectric signals, also known as biopotentials, are produced. The biopotential measured on the skin surface is actually the collective activity of large groups of cells. This additive change in the extracellular fluid is known as summed ionic flux. The mechanism within neurons creates action potentials through the movement of sodium and potassium ions in and out of the cell, respectively. As a result of the movement of sodium and potassium ions, the extracellular fluid This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ becomes more positively charged and the fluid inside the neuron becomes more negatively charged relative to the outside of the cell. The resulting concentration gradient from this rapid ionic movement is responsible for action potentials. These basic concepts, related to neurochemical and positive-negative charges that create an action potential, are essential for a basic understanding of the data a sleep technologist acquires. The polysomnogram (PSG) is actually an expression of the many bioelectric signals generated by physiologic function. PARAMETERS TYPICALLY EVALUATED BY POLYSOMNOGRAPHY The PSG is a compilation of three basic signal types: bioelectric, transduced, and those incorporated from ancillary equipment. Bioelectric signals directly represent the rising and falling of electrical potentials as obtained at the surface of the body. o These include the electroencephalogram (EEG), electromyogram (EMG), electrooculogram (EOG), and electrocardiogram (ECG). o The EEG is recorded using small cup electrodes constructed of precious metal, often silver or gold-plated silver. o The EMG, ECG, and EOG can be recorded using the same cup electrodes, although it is acceptable to use other types of electrodes to record these noncephalic parameters. A transduced signal is recorded using a transducer, a device that converts one form of energy into another form of energy. For example, a microphone converts sound waves to electricity that can be saved as an audio file or displayed graphically to represent volume. The third type of signal is derived from monitoring equipment that has been interfaced with the data acquisition system. The term interfaced means the quality of being connected together. These devices can be used as stand- alone monitors to provide data, typically on a built-in screen, or they can be connected to the sleep study recorder as an additional parameter of the PSG. ELECTROENCEPHALOGRAPHY The EEG records the amplitude, morphology, and frequency of encephalographic bioelectric signals for visual display. Over many years of research, the sleeping brain was observed to generate distinctive electrophysiologic changes that were categorized into waveform types and allowed for categorization of sleep into various states. Behaviors, such as eye movements and muscle activity, help differentiate sleep from wake and provide essential information used to discriminate non–rapid eye movement (NREM) sleep from rapid eye movement (REM) sleep Muscle activity can also indicate whether sleep issues may be related to a movement disorder or can help distinguish between parasomnias and potential seizure activity. Automatic or anatomic functions such as heart activity and breathing provide additional information about sleep and can yield valuable diagnostic information, as well as information regarding the efficacy of treatment for a previously identified disorder. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The signals typically recorded during PSG, as described in the following paragraphs, should be recorded with all characteristics intact using filters set above and below the individual parameter’s frequencies of interest to produce the most accurate recording of sleep. Example settings for the low-frequency filter, high-frequency filter, and other amplifier controls for each recording parameter are provided by the American Academy of Sleep Medicine (AASM). The AASM-recommended settings, or those deter- mined for use in a specific workplace, should be set at the start of each recording and be appropriately altered to enhance the quality of recorded data. Judicial adjustment of parameters must be employed only when the underlying signals remain intact and other means of correcting an issue have been exhausted. The following are descriptions of the types of wave activity: o Alpha activity: EEG data in the range of 8-13 Hz, most prominently recorded from the occipital region. Waveform morphology is typically sinusoidal, often appearing in a crescendo-decrescendo pattern o Beta activity: waves with frequency >14 Hz interspersed throughout the EEG with eyes opened, and alpha activity when eyes are closed o Delta activity: EEG data with frequency of 0.5-2 Hz and peak-to-peak amplitude of >75 mV measured over the frontal region o Theta activity: EEG activity with a frequency of 3-7 Hz predominantly central in origin. Theta is a prominent component of low voltage mixed frequency activity LOW-AMPLITUDE, MIXED-FREQUENCY (LAMF) WAVES Frequency: predominantly 4-7 Hz Amplitude: relatively low Features: predominantly consists of theta activity in the 4-7 Hz range during sleep, although other fast frequencies such as alpha and beta can be interspersed throughout the pattern. When the subject is awake with eyes open, more alpha and beta are present. Alpha Waves Frequency: 8-13 Hz Location: prominent in the occipital region Amplitude: 10-150 microvolts Features: sinusoidal morphology; seen during wake with eyes closed and attenuated by eyes opening; can be interspersed throughout the LAMF pattern. It should be noted that approximately 10% of the population does not generate an alpha rhythm when the eyes are closed This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Delta Waves Frequency: 0.5-2 Hz Location: measured over the frontal region Amplitude: >75 mV Features: stage N3 (slow-wave sleep [SWS]) scored when >20% of an epoch consists of delta activity; chin EMG amplitude is variable, often lower than seen in stage N2 sleep and sometimes as low as seen in stage R sleep, but not used for scoring stage N3 This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Sawtooth Waves Frequency: 2-6 Hz Location: central region Amplitude: variable Features: sharply contoured or triangular waves can be serrated; often but not always heralds a burst of rapid eye movements; not required for the scoring of stage R This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Theta Waves Frequency: 3-7 Hz or 4-7 Hz Location: temporal and central regions Amplitude: variable Features: Makes up the majority of the predominantly LAMF pattern seen in stage N1, stage R, and the background rhythm of stage N2 Sleep Spindles Frequency: 11-16 Hz (most commonly 12-14 Hz) Location: central region Amplitude: variable Features: bursts with sinusoidal morphology lasting >0.5 seconds, seen in stage N2 sleep This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ K Complex Duration: >0.5 second duration Location: maximal over the frontal region Amplitude: variable Features: biphasic morphology; negative deflection followed by a slower positive component; seen in stage N2 sleep, stands out from the background EEG This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Vertex Sharp Waves Duration: >0.5 second duration Location: central region Amplitude: variable Features: sharply contoured negative wave, distinguishable from the background activity; may be present, but is not required to score N1 sleep; a normal variant of sleep EEG ELECTROOCULOGRAM The EOG records eye movement to identify important changes in sleep state. During wakefulness, eye movements may be sharp as the patient watches an object move across the room or while reading in bed. During drowsiness, the eyes may roll slowly. Slow eye movements (SEMs) often signify drowsiness and the transition into sleep. o SEMs are defined as conjugate, reasonably regular sinusoidal eye movements with an initial deflection usually lasting more than 500 ms. o In fact, when non-alpha producers begin having SEMs, the start of NREM stage 1 (N1) sleep is scored. During REM sleep, the eyes dart right and left and up and down. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Oblique, or slanted, eye movements also occur during this phase of sleep, although they are not recorded using standard electrode placement. The AASM defines rapid eye movements as conjugate, irregular, sharply peaked eye movements with an initial deflection lasting less than 500 ms. o When the patient looks to the right or looks up, the signal on the right EOG channel deflects downward and the signal on the left EOG channel deflects upward. o When the patient looks to the left or downward, the signal on the right EOG channel deflects up and the signal on the left EOG channel deflects down. o Some sleep testing facilities also place a right inferior EOG and left superior EOG electrode for backup purposes. Recording Methods and Sleep-Wake Stage Scoring EOG electrodes are positioned 1 cm below the LOC, or left outer canthus (E1), with another electrode placed 1 cm above the ROC, or right outer canthus (E2). An alternative recording relies on both the right and left EOG electrodes being placed 1 cm lateral and 1 cm inferior to the outer canthus. For these recording channels, the exploring electrodes are connected to a supranasion reference. The supranasion reference is placed midline, above the nasion, at the location referred to as frontal pole midline (Fpz). The main advantage of this configuration is that oblique eye movements are recorded. It can be beneficial to record the EOG with alternative placement when a multiple sleep latency test is anticipated because it is crucial that rapid eye movements be identified during a nap study. Recording from each outer canthus to a right mastoid reference, which are the recommended derivations from the AASM Manual, always yields out- of-phase deflections While awake with the eyes closed, the EOG may show little or no movement. Fortunately, most individuals produce alpha-range activity while awake with the eyes closed, making this state easy to identify with certainty. Refer to the AASM Manual for the Scoring of Sleep and Associated Events for the rules applied to the sleep-stage scoring of wake and N1 in subjects who do not generate alpha rhythm During drowsiness and as sleep ensues, SEMs may commence. o The hallmark of N1 sleep onset is an LAMF EEG with elevated chin EMG and most often the presence of SEMs. o Unfortunately, it can be difficult to differentiate the wake state, stage N1 sleep, or stage REM sleep with the eyes open because an LAMF background makes up the EEG pattern for these three sleep-wake states with only subtle differences. o Chin EMG is essential to help determine REM versus NREM sleep in conjunction with the EOG for correct identification of these states. o During wake with eyes closed, the chin EMG will be elevated and the EOG will yield sharp, fast scanning or reading eye movements with blinks. o Identification of blinks on the EOG is a skill essential to differentiating this state. During NREM 1 there will be SEMs, although rapid eye movements often appear when the subject is taking a selective serotonin reuptake inhibitor (SSRI) or selective norepinephrine reuptake inhibitor (SNRI) antidepressant. o For this reason, it is imperative for a sleep technologist to know the patient’s current and past medical his- tory and medications that have been taken prior to the sleep study. o These particular rapid eye movements during NREM sleep are often referred to as Prozac eyes. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ During REM sleep, as the name suggests, there should be rapid eye movements at some point during the REM period. This is termed “phasic REM” and is the state typically thought of as REM sleep. o As long as all other characteristics of stage REM persist, “tonic REM” is said to occur when there are no eye movements following a period of phasic eye movements. o REM sleep can be discerned from other sleep-wake stages with a LAMF EEG when rapid eye movements appear with- out blinks as long as the patient is not taking an SSRI or SNRI medication. o To stage-score REM sleep, the chin EMG must be lower than all other stages and at the lowest level of the recording. o Chin EMG is primarily useful for differentiating NREM sleep from REM sleep as it has no bearing on scoring the substages of NREM sleep. o To ensure a distinct drop in the qualitative chin EMG signal at the onset of REM, the amplifier should be continuously adjusted during NREM sleep to pro- duce a minimal signal deflection of approximately one- half of the channel’s peak-to-peak capability. o The technologist must also identify and respond to 60-Hz interference. Artifact in the chin EMG should be eliminated to ensure it does not mask a reduction in muscle tone representative of REM sleep. ELECTROMYOGRAM The electromyogram is a measure of the electrical potential difference generated by groups of skeletal muscle cells at rest and during activation. For the purposes of PSG monitoring, the EMG is a qualitative signal, although a voltage threshold must be met for scoring limb EMG events. Overall, the monitoring of EMG is important to the sleep technologist as it provides information on the sleep state of the patient and whether specific body movements cause disruptions in the sleep continuity for the patient. Chin Electromyogram During REM sleep, the body is virtually paralyzed, causing chin EMG tone to disappear (atonia) as submentalis muscles become inhibited by the brain. The submentalis muscle, located immediately under the chin, is very useful in identifying wake, sleep, and REM. The AASM recommends a bipolar derivation of the submentalis with two electrodes to record chin muscle tone and one additional back-up electrode. One electrode is placed 2 cm above the inferior edge of the mandible (jawbone) on the middle of the chin and the other two are placed 2 cm below the inferior edge of the mandible, one 2 cm to the left and the other 2 cm to the right. During acquisition, the anterior midline electrode should be used as input 1 with either of the two electrodes below the inferior edge of the mandible as input 2. The chin EMG amplitude should be high enough that an obvious drop can be seen when the patient goes into REM sleep Leg Electromyogram This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The leg EMG is important to monitor as it gives information concerning limb movements and any changes in sleep patterns caused by these movements. The anterior tibialis muscle group can be best located by having the patient flex the big toe up and down. During this maneuver the belly of the anterior tibialis can be located for electrode placement by feeling for muscle activation. Electrodes should be placed, one above the other, along the belly of each anterior tibialis 1 to 3 cm apart. If only one channel is available, both legs can be recorded on a single channel by placing an electrode from one leg in the input 1 position and an electrode from the other leg into the input 2 position of a single derivation. This is not recommended, but it will suffice, if necessary. Unfortunately, with this “linked” derivation the long interelectrode distance will almost in- variably result in ECG artifact and the likelihood of 60-Hz artifact will be dramatically increased. MODIFIED LEAD II ELECTROCARDIOGRAPHY (ECG) The ECG is a vital parameter for all sleep recordings and is used to document changes in heart rate and ECG signal morphology related to sleep state, ab- normal events, and/or underlying pathologic conditions. Nerves in the heart are highly specialized to depolarize and to conduct electrical activity through specific nerve tracts. When stimulated, these nerve tracts cause cardiac muscles to contract in a sequence, which is responsible for the cardiac cycle that sends nutrient-rich, oxygenated blood throughout the body. Lead Placement The lead placement recommended by the AASM is referred to as modified lead II. One lead is placed below the right clavicle, aligned with the nipple and the other on the lower left ribs, aligned with the hip and midaxillary (arm pit). The left lead should be placed over an intercostal space, between the ribs, although this space is sometimes difficult to identify in the patient population served by sleep centers. T he right lead is plugged into the negative input and the left into the positive connection on the ECG harness. This lead placement should yield an upright P wave, which is of most importance, at the start of the recording. If not, reverse the inputs so that the P wave is upright Depending on exact electrode placement, and the patient’s cardiac pathologic conditions and body composition, the QRS may either yield an upright or downward deflection. The deflection of the QRS has no bearing on the recorded data. SLEEP/WAKE STATES Sleep stage is scored in 30-second periods called epochs. Sleep stage scoring of wake, NREM stage 1 (N1), NREM stage 2 (N2), NREM stage 3 (N3), and REM (R) is determined by the waveform information gathered during a sleep recording through the analysis of all recorded bioelectric signals. Although an oversimplification of the process, the sleep-stage characteristics that comprise more than 50% of a 30- second epoch determine the epoch’s stage. WAKE This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Various differences exist between the appearance of recording parameters during wake with eyes open and wake with eyes closed. Throughout stage wake, however, the chin EMG yields variable muscle tone, typically higher than what is recorded during the various sleep stages. Unfortunately, during stage wake with the eyes open, the EEG can be easily confused with the EEG of stage N1 sleep and stage R sleep, since they are all LAMF patterns; however, a distinct feature of stage wake with eyes open that can resolve this issue is the presence of blinks. When the subject is relaxed with the eyes open, stage wake is identified by a low-amplitude, mixed- frequency EEG pattern, chiefly made up of alpha waves and beta rhythms. Alpha waves are trains of 8-13 Hz activity that are sinusoidal in nature and primarily seen in the occipital region in most sub- jects. Alpha amplitude while the eyes are open is much lower as compared to alpha amplitude during wake with eyes closed. Maximum beta amplitude is usually evident in the frontal to central regions and is composed of frequencies greater than 14 Hz. The EOG demonstrates conjugate eye movements consisting of a slow phase followed by a fast phase in the opposite direction when reading, rapid eye movements as the subject scans the environment, and eye blinks with a frequency of 0.5-2 Hz. When the subject closes his or her eyes, there is a proliferation of alpha activity. During relaxed wakefulness with the eyes closed, more than half of the epoch must contain EEG that consists primarily of alpha activity. Alpha waves are trains of 8-13 Hz activity which are sinusoidal in nature and primarily seen in the occipital region in most subjects. On the EOG, slow eye movements (SEMs) may be present, defined as conjugate, reasonably regular, sinusoidal movements with an initial deflection usually lasting more than 500 ms. Alpha activity is attenuated upon opening of the eyes, giving way to an LAMF EEG pattern, which is primarily seen in the central derivations. Upon transition into sleep, a slowing of background EEG frequencies and attenuation of amplitude are typical. For individuals who do not produce alpha rhythm, score stage wake if any of the following are present: o 1. Eye blinks at a frequency of 0.5-2 Hz. o 2. Reading eye movements. o 3. Irregular, conjugate, rapid eye movements associated with normal or high EMG tone. EXAMPLE OF WAKE STAGE This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ STAGE N1 Stage N1 sleep is scored when greater than half of an epoch contains a LAMF EEG in subjects who generate alpha. The dominant waveform in stage N1, LAMF activity is characteristically within the 4 to 7 Hz range. Vertical sharp waves may also be seen in some patients. Slow-rolling sinusoidal eye movements that are conjugate, with an initial deflection usually lasting more than 500 ms are usually seen. For subjects who do not generate alpha activity, begin scoring stage N1 sleep with the earliest of any of the following: o 1. EEG activity in the range of 4-7 Hz with slowing of background frequencies 1 Hz from those of stage W. o 2. Vertex sharp waves o 3. Slow eye movements This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ STAGE N2 Stage N2 sleep begins with the presence of either a sleep spindle (12-14 Hz) or K complex each of which must have a duration lasting 0.5 seconds or longer. Spindles are maximal over the central regions but may be seen in the occipital or frontal regions. K complexes are maximal when recorded over the frontal region. A LAMF background EEG continues. Eye movement activity usually disappears The chin activity can be variable from slightly below wake to as low as seen in REM sleep This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ STAGE N3 Often called slow-wave sleep (SWS), stage N3 sleep often emerges from stage N2 sleep and is characterized by a progressive decline in spindles and an increase in 0.5-2 Hz delta activity with peak-to-peak amplitude of more than 75 mV as measured over the frontal region. When >20% of the epoch is composed of delta waves, the epoch is scored as stage N3 sleep. On a 30-second epoch, six cumulative seconds of delta activity must be present. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Eye activity is typically absent but delta waves may appear as in-phase deflections on the eye channels because of the voltage responsible for their amplitude. The chin tone is typically lower than in stage N2. STAGE R During REM sleep (stage R), the EEG background is LAMF. Sawtooth waves may be seen. Conjugate rapid eye movements that are sharply peaked and irregular appear in bursts. The initial defection of the eye movements usually last less than 500 ms. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ The chin EMG drops to its lowest level for the sleep study. The first REM sleep period usually occurs ap- proximately 90 minutes after sleep onset. Stage R sleep is divided into two types: o 1) phasic REM sleep, in which there are rapid eye movements and episodic EMG twitching, known as transient muscle activity; and o 2) tonic REM sleep, in which rapid eye movements are absent and chin tone continues to be very low. Tonic REM sleep is only scored following a period of phasic REM sleep when eye movements cease but all other parameters remain consistent with REM sleep. Check for Understanding You will answer and rationalize this by yourself. This will be recorded as your quiz. One (1) point will be given to correct answer and another one (1) point for the correct ratio. Superimpositions or erasures in you answer/ratio is not allowed. You are given 20 minutes for this activity. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ 1. A device that converts one form of energy to another, such as mechanical energy into electrical energy, is known as a(n): a. Oximeter b. Transducer c. Impedance meter d. Capnograph ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 2. Relaxed wakefulness with eyes closed typically results in: a. Alpha activity b. Spindle activity c. REMs d. K complexes ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 3. A clear pattern of rhythmic alpha activity changing to a relatively low-voltage, mixed-frequency pattern occurs during transition from: a. Stage wake to stage N1 b. Stage N1 to stage N2 c. Stage N2 to stage N3 d. Stage N1 to stage R ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 4. A 0.5-second burst of 12-14 Hz activity describes a: a. K-complex b. REM c. SEM d. Spindle ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 5. A 0.5-second sharp negative deflection immediately followed by a slower positive component de- scribes a: a. Delta wave form This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ b. K complex c. Spindle d. REM ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 6. A 1–second, 75 mV wave form describes a: a. Delta wave b. Spindle c. K complex d. SEM ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 7. Sharply contoured 2-6 Hz waves are typically noted in which stage of sleep? a. Stage N1 b. Stage N2 c. Stage N3 d. Stage R ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 8. Epileptiform activity on the PSG encompasses which of the following? a. K complex b. Spindle c. Spike d. Delta ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 9. An eye movement to the right produces which of the following signals? a. Downward deflection on the E2 b. Downward deflection on the E1 c. Lateral deflection on the E2 d. Lateral deflection on the E1 ANSWER: ________ This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #9 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ 10. An eye movement to the left produces which of the following signals? a. Downward deflection on the E1 b. Downward deflection on the E2 c. Lateral deflection on the E1 d. Lateral deflection on the E2 ANSWER: ________ RATIO:___________________________________________________________________________________________ _________________________________________________________________________________________________ C. LESSON WRAP-UP INTRODUCTION Recalling that a nerve cell, or neuron, is simply a highly specialized animal cell, at one end, the dendrites receive signals from other cells in the form of chemical mediators. On the opposite end of the neuron are the axon terminals, which release chemical mediators across the synapse if the signal is propagated through the cell body and across the axon. These structures lie between the dendrites and the axon terminals. Through the normal function of neurons and other cells of the body, bioelectric signals, also known as biopotentials, are produced. The biopotential measured on the skin surface is actually the collective activity of large groups of cells. This additive change in the extracellular fluid is known as summed ionic flux. The mechanism within neurons creates action potentials through the movement of sodium and potassium ions in and out of the cell, respectively. As a result of the movement of sodium and potassium ions, the extracellular fluid becomes more positively charged and the fluid inside the neuron becomes more negatively charged relative to the outside of the cell. The resulting concentration gradient from this rapid ionic movement is responsible for action potentials. These basic concepts, related to neurochemical and positive-negative charges that create an action potential, are essential for a basic understanding of the data a sleep technologist acquires. The polysomnogram (PSG) is actually an expression of the many bioelectric signals generated by physiologic function. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #10 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Lesson title: Materials: THE RECORDING OF PHYSIOLOGICAL PARAMETERS Book, pen and notebook Learning Targets: At the end of the module, students will be able to: References: Marshall, B., Robertson, B,. Carno, M-A. 1. Specify recorded physiologic parameters. (2017). Polysomnography for the Sleep 2. Interpret baseline patient data. Technologist (11th ed.). St. Louis, MO: 3. Classify sleep study calibrations. Elsevier, Inc. 4. Distinguish documentation required during sleep studies. 5. Predict factors for optimization of recorded data. 6. Demonstrate the use and limitations of filters. 7. Specify gain and sensitivity adjustments. A. LESSON PREVIEW/REVIEW Introduction Hello, PHINMA Ed students! Welcome to RET 010: Introduction to Polysomnography. In today’s session, you are tasked to set expectations as you get oriented with what the subject is all about and to determine the nature of flexible learning. Before we begin with the formal course orientation, let’s pause and reflect by briefly answering the questions below: B.MAIN LESSON INTRODUCTION The recording of a polysomnogram (PSG) requires the sleep technologist to use a comprehensive skill set. Performing a sleep study requires a firm grounding in technical knowledge, from the application of electrodes through electrical safety, electrical signal processing, and display and storage of data in a digital format. A technologist who combines these technical skills with basic sleep science and knowledge of treatment modalities is prepared to effectively provide numerous hours of direct patient care. In some ways the basics of recording an electroencephalogram (EEG) during sleep from surface electrodes has changed little since 1938 when the first EEG was recorded. o EEG remains a significant component of the sleep recording; however, there has been a proliferation in the development of sensors and methodologies used to measure the complex array of physiologic signals. o This allows for identification of numerous sleep disorders in a single recording session. o This is the “poly” of polysomnography, which literally means “many sleep writings.” Of course, much of the “writing” today happens in a digital format. This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #10 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ o It is the recording process that has changed dramatically during the past 20 years. o Analog polygraphs were an impressive collection of circuits, switches, galvanometers, and pens. o Computerized sleep recording systems have simplified many aspects of polysomnography. There are no more paper records to store, no ink, and no mechanical parts. Surprisingly, the amplifier controls that allow manipulation of data have changed very little. The recording technologist must possess full knowledge of these controls in the same way required for effective use of an analog polygraph. Without this skill set, it is not possible to produce a high-quality study representative of physiologic data. Digital systems provide a wide array of clinical tools that have helped advance the role from that of someone who was primarily concerned with acquiring data to the role of technologist, a highly skilled clinician who is trained to make important clinical decisions during a sleep study. RECORDING PHYSIOLOGICAL PARAMETERS In simple terms sleep studies can be broken into two primary categories: diagnostic and therapeutic. o The diagnostic PSG provides a comprehensive analysis of sleep patterns, cardiopulmonary function, and body movements that can confirm or rule out sleep- disordered breathing (SDB), movement disorders, inefficient sleep, and parasomnias. o Abnormal cardiac and EEG events may also be identified and recorded. o The diagnostic PSG montage is composed, at minimum, of channels for recording the electroencephalogram, electromyogram, electrocardiogram, airflow, respiratory effort, and oxyhemoglobin saturation measured by pulse oximetry (SpO2). o A diagnostic PSG is also performed to observe and document the efficacy of surgery or pharmacologic treatment of a previously diagnosed sleep disorder. A treatment study is a PSG during which a therapeutic intervention is initiated and titrated. o Therapeutic intervention is the implementation of the PAP therapy or another treatment such as oral appliance therapy. For a treatment study, the same montage as that for a diagnostic study is typically used, with the addition of a treatment parameter, most often positive airway pressure (PAP) or oral appliance therapy for SDB. o A therapeutic study is characterized by active technologist intervention in the therapy being applied. o A split-night PSG combines a diagnostic portion of study to confirm the presence of SDB along with technologist intervention to apply and adjust the therapeutic modality, which is most commonly PAP or an oral appliance. Sleep study measurements are derived from electrodes and sensors that are designed to collect data from numerous physiologic systems. Electrical activity from the brain, eyes, heart, and muscles is measured using surface electrodes. The measurement of changes in body position, vocal sounds, and the respiratory system uses more mechanical technologies. Because these signals are so different, it is important to know what signal is being recording and how that signal is measured to determine what response to expect from each recording sensor during the occurrence of various possible sleep disruptions. BASELINE PATIENT INFORMATION This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #10 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Practitioner orders typically stipulate whether a diagnostic, therapeutic, or split-night test is to be performed, and define patient-specific recording parameters. Most laboratories have a predetermined montage for each test type; however, the ordering practitioner may choose to modify these parameters. For instance, additional EEG electrodes may be placed when epileptiform activity or the presence of a parasomnia is suggested by patient history. Prior to recording, the technologist must verify that the practitioner’s orders for the test to be performed are consistent with the patient’s presentation and medical history. Standing orders, or predetermined physician orders, for each of the study types described previously contain information on the montage, from which equipment requirements for the study can be determined. Prior to recording, the filter and gain or sensitivity settings, and channel labels should be verified to ensure they match the desired montage. MACHINE CALIBRATIONS Once the montage is verified, machine calibration signals are recorded and evaluated to confirm amplifier function and amplifier control response for each channel. If the acquisition system is capable of producing an all- channel calibration signal, this should be the first step in the process The all-channel calibration is performed by simultaneously inputting a known voltage, typically 50 mV, to all amplifiers with each channel gain or sensitivity, low-frequency filter (LFF), and high-frequency filter (HFF) set to identical values. The signals generated are evaluated for consistent amplitude, morphology, and time constant. If a channel displays signals different from the others, amplifier settings should be confirmed and, if correct, amplifier function should be questioned. If incorrect, set to the proper values and repeat the process. Following the all-channel calibration, or as the first step in the process in the absence of this capability, a montage calibration is performed. Following the montage calibration, channels with like settings (e.g., EEG channels, EMG channels, respiratory channels) should be assessed for identical output. If a channel output is not as expected, the technologist must first verify correct settings. If incorrect, the calibration should be repeated after correcting the setting If settings are correct and output is not as it should be, amplifier function should be questioned. Together, the all- channel and the montage calibration are referred to as machine calibrations. Machine calibrations verify the screen order, baseline, labels, and filter settings for each channel. The technologist’s role is to visually inspect the amplitude, morphology, and decay time constant of each recording channel. If settings are correct and output is not as it should be, amplifier function should be questioned. Together, the all- channel and the montage calibration are referred to as machine calibrations. Machine calibrations verify the screen order, baseline, labels, and filter settings for each channel. The technologist’s role is to visually inspect the amplitude, morphology, and decay time constant of each recording channel. Amplitude, Morphology, and Decay Time Constant This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #10 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Signal amplitude is the product of input voltage and the gain or sensitivity setting of the amplifier; morphology is the result of both the HFF and LFF settings; and the decay time constant is determined by the LFF or time constant setting. The decay time constant, or simply time constant, is defined as the time it takes for a square wave to return to 37% of its original amplitude, and can dramatically affect signal morphology. o A longer time constant is the result of a lower LFF setting, whereas a shorter time constant is the result of a higher LFF setting. In other words, the time constant has an inverse relationship with the LFF. o On some recorders, a time constant setting replaces the LFF setting. Because all EEG and EOG channels share identical amplifier settings, respiratory channels also most often have identical amplifier settings. Because all EMG channels have the same LFF and HFF settings, visual inspection of montage calibration signals is easily accomplished by ensuring all like channels have consistent morphology and that EEG and EOG channels have identical amplitude. All-Channel Calibration The all-channel calibration is performed by simultaneously applying a known voltage to all AC channels with the LFF, HFF, and gain or sensitivity controls set the same for each amplifier Each channel yields identical signal amplitude, morphology, and decay if functioning properly. The purpose of this procedure is to verify overall amplifier function by assessing these parameters. The all-channel calibration was an important step in preparing an analog polygraph for use, during which mechanical adjustments were made to the instrument. Although it provides a clear overview of function, most digital acquisition systems lack the ability to perform this step because mechanical adjustments are no longer necessary. Shown below is an example of all channel calibration This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #10 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Montage Calibration The montage calibration is similar to the all-channel calibration in that a known voltage is applied to all alternating current (AC) channels. The difference is that each channel is set to the recommended values for LFF, HFF, and gain or sensitivity typically used at the beginning of each study. This procedure is also performed to verify amplifier function and more importantly, to verify that individual channels respond appropriately to control setting changes. To evaluate recorder function based on this procedure, the technologist must compare channels with like settings (e.g., respiratory channels, EEG channels, EMG channels, etc.). If a channel displays morphology, amplitude, or decay time different from like channels, the technologist must first ensure that settings are correct. If so, amplifier function must be questioned Shown below is an example of montage calibration This document is the property of PHINMA EDUCATION  RET 010: Introduction to Polysomnography Module #10 Student Activity Sheet Name: _________________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ SIGNAL CALIBRATIONS Signal calibrations verify that the direct current (DC) output of ancillary devices such as oximeters, end-tidal carbon dioxide monitors, and pressure transducers are being correctly processed by the PSG recording software. Calibration procedures for these devices are defined by the device manufacturer and PSG software vendor. In general a defined voltage is generated by the ancillary device. o For oximeters this is commonly a 1-V DC signal. From within the software, the technologist types in the physiologic value associated with that signal. In this case 1 V DC equals 100% SpO2. The software indicates if the voltage range generated by the device is within the acceptable range. Once it is accepted, the device generates a second value. Commonly this is half of the voltage output by the device. Once again this value