Healthy Adult, 31-year old male
- Healthy sleep pattern.
- Subject had no issues falling asleep.
- Consolidated stable sleep through the night.
- One cup of strong coffee was consumed at 07:00PM.
- Stable sleep onset is not until 2.5 hours into the sleep period.
- Movements are increased during this long sleep latency period.
- Noticeably fragmented sleep for the rest of the night compared to baseline night.
Complex Sleep Apnea
Central Sleep Apnea & Atrial Fibrillation
Presence of CSA indicated by prevalent Periodicity, confirmed by CAI of 24 scored by PSG.
Study produced a clear spectrogram due to strong respiratory component, despite the presence of AF.
Signal Quality Issues: The Signal Quality Line
There are 3 primary reasons why the Signal Quality Line may report segments of yellow, amber, or red signal.
- Signal Loss – The mobile app was not able to communicate with the recorder and therefore no signal is received for that period. The result will be a gap in the analysis.
- Artifact – Poor sensor contact or excessive motion during recording will result in signal noise that does not produce valid output. The result is a signal that does not have the appearance of a physiological signal and may exceed the upper and lower extremes of the graph.
- Physiological abnormalities – In patients with chronic arrhythmia, the SleepImage System may be unable to provide to analyze the signal successfully. In these cases, the signal quality line will be yellow, amber, or red, even though the input signal is absent any signal loss or artifact. If a patient is suspected of having arrhythmia, please refer them to the appropriate specialist for further evaluation. The SleepImage System is not intended to rule in or rule out arrhythmia.
The Signal Quality Line is displayed on every screen of the SleepImage Report: Study Overview, Study Detail, and the Raw Data page. It is recommended to navigate to the Raw Data for signal review for any study that does not have a “predominantly green” Signal Quality Line, or extended areas of suboptimal signal quality. See SleepImage System IFU and Introduction to SleepImage for details.
Example 1 - Temporary Signal Loss
In this example, the communication between the mobile app and the recorder was interrupted and therefore no signal is received for the period between 03:43 AM and 03:59 AM.
The result is a gap in the analysis where the signal quality line is red. We also see that the plethysmogram signal (Pleth) is flat during this period.
Example 2 - Extended Signal Loss
In this example, the communication between the mobile app and the recorder was interrupted at 05:37 AM and the connection is not reestablished until 08:04 AM.
The result is a gap in the analysis where the signal quality line is red. We also see that the plethysmogram signal (Pleth) is flat during this period.
In order to prevent an event like this one where the app is unable to reconnect to the recorder, for example when the patient goes out of Bluetooth range, we recommend unlocking the phone and checking the SleepImage App before going back to sleep. Once SpO2 and pulse rate values are displayed in the app, the patient can go back to sleep.
Example 3 - Signal Artifact
In this example, we click the spectrogram at 02:29 AM where the Signal Quality Line is red until 02:39 AM.
We can see that during this time, the Pleth signal is distorted and exceeds the maximum and minimum values on the graph, as a result of motion in this case.
Other causes, in addition to motion artifact are improper sensor fit or an obstruction between the sensor and the finger. These can result in various different distortions of the signal(s). The key is to become comfortable with identifying what a normal Pleth signal looks like to be able to identify abnormal signal.
During periods like this, the software may not be able to accurately determine the physiological state and alerts the user by coloring the Signal Quality Line red.
Example 4 - Arrhythmia
Important! Please note that the SleepImage System is not intended to aid in identification or diagnosis of any arrhythmias. The information below is provided to explain how to review the Signal Quality Line. If you suspect a patient has arrhythmias, please proceed appropriately.
In this example, there are no signal dropouts and the periods of yellow, amber, and red are mostly not associated with evidence of motion artifact. However, when we review the Pleth signal we see that it looks somewhat abnormal. We see that periodically, some pulses have greater amplitude than the preceding and succeeding pulses. Additionally, there are regular occurrences where the intra-beat interval are abnormally long.
The SleepImage output is fully automated and presented in tables and graphs with color-coded expected values to aid sleep disorder evaluation, diagnosis and management. Multi-night studies are shown on trend graphs and Clinicians can write notes and make recommendations for further testing, evaluation, and treatment. Clinicians furthermore have access to the raw data for evaluation and an ability to adjust the study period to recalculate the automated output values.
The Sleep Spectrogram is an intuitive overview of the sleep period with biomarkers of sleep quality and sleep pathology to provide a new and practical approach to trend sleep as a vital sign of health over time and to identify and manage sleep disorders.
SleepImage is a useful clinical tool, whether it is to evaluate symptoms of Insomnia, aid diagnosis of Sleep Disordered Breathing (SDB) or track treatment. The SleepImage analysis is based on data collected with either an electrocardiogram (ECG) or photoplethysmogram (PPG) sensor during sleep. Both signals contain information/data on heart (pulse) rate variability (HRV/PRV) as a measure of autonomic drive (sympathetic and parasympathetic) and respiration, that both are strongly modulated by sleep.
The SleepImage software utilizes mathematical and frequency analysis to calculate the synchronization between HRV/PRV and respiration to provide visualization of sleep in the Sleep Spectrogram that is reported numerically as Sleep Quality, Sleep Duration, Sleep Apnea, Fragmentation and Periodicity.
Sleep Quality Index (SQI) is a summary index of the CPC biomarkers that provides a meaningful unit of measure of sleep health. The SQI is displayed on a scale of 0-100 and with expected values for both children and adults. The SQI can be used as a “unit of measure” for sleep health that is useful to track sleep health over time, whether to identify the need for further clinical investigation or to track therapy. The SQI is easily communicated and relatable for the patient or other lay persons, while at the same time being a summary measure of sleep health that has been clinically validated and FDA-cleared.
Sleep Apnea Indicator (SAI) provides a measure of SDB and is based on detecting oscillations in cardiac intervals associated with prolonged cycles of sleep apnea, based on Cyclic Variation of Heart Rate (CVHR) during unstable breathing (tidal volume fluctuations in breathing). During each apnea event, blood oxygen decreases and is accompanied by a physiological reaction of bradycardia and, when breathing resumes, a relative tachycardia and thus reflecting hypoxemia. When SAI is presented with the Sleep Quality Index, Fragmentation and Periodicity, it is possible to use the SAI to not only help detect apneas, but also to differentiate between obstructive, central and complex/mixed sleep apnea.
Apnea Hypopnea Index (sAHI) is an automated measure of Apnea/Hypopnea events, following the American Academy of Sleep Medicine (AASM) scoring guidelines of the Apnea Hypopnea Index (AHI) for both adults and children, as mild, moderate and severe sleep apnea. When blood oxygenation data (SpO2) is recorded, the SleepImage System automatically analyzes the SpO2 data to generate desaturation events, display an SpO2 graph and automatically calculate SleepImage Apnea Hypopnea Index (sAHI) by combining other CPC-biomarkers and hypoxic events during sleep time measured by CPC. The automatically generated sAHI is FDA-cleared to be comparable to AHI scoring from polysomnography (PSG) studies to aid diagnosis of Sleep Disordered Breathing (SDB) in both children and adults.
Fragmentation (eLFCBB) is a subset of low-frequency coupling, it is an indicator of pain, upper airway resistance and Obstructive Sleep Apnea (OSA).
Periodicity (eLFCNB) is a subset of low-frequency coupling, it is an indicator of periodic type breathing and Central Sleep Apnea (CSA).
The SleepImage Apnea Hypopnea Index (sAHI) is an automated measure of Apnea/Hypopnea events, following the American Academy of Sleep Medicine (AASM) scoring guidelines of the Apnea Hypopnea Index (AHI) for both adults and children as mild, moderate and severe sleep apnea. When blood oxygenation (SpO2) data is recorded, the SleepImage System analyzes the SpO2 data to generate desaturation events, display an SpO2 graph and automatically calculate SleepImage Apnea Hypopnea Index (sAHI) by combining other Cardiopulmonary Coupling (CPC) biomarkers and hypoxic events during sleep time measured by CPC. The automatically generated sAHI is FDA-cleared to be comparable to AHI scoring from polysomnography (PSG) studies to aid diagnosis of Sleep Disordered Breathing (SDB) in both children and adults.
The sAHI, like the AHI, reports the number of paused breathing events during the sleep period. Events are displayed based on CPC sleep states (Stable and Unstable NREM sleep and REM sleep). Additionally, events are presented concurrently with and without cyclic variation of heart rate (CVHR) to aid in clinical interpretations and management of SDB. When reviewing the overall sAHI score, it is recommended to consider SDB events concurrent with CPC sleep states to evaluate and determine disease severity and for differential diagnosis of Obstructive (OSA), Central (CSA) or Complex/Mixed Sleep Apnea, using the pathology biomarkers of Fragmentation (elevated low-frequency coupling broad band, eLFCBB), that is associated with obstruction and Periodicity (elevated low-frequency coupling narrow band, eLFCNB), that is associated with periodic breathing.
Over the last decades, Polysomnography (PSG) has been the most widely used clinical measure of sleep where sleep is described as NREM sleep and REM sleep based on Electroencephalogram (EEG) morphology. NREM sleep is presented in 3 sleep stages and REM sleep is also often referred to as dream sleep.
SleepImage, Cardiopulmonary Coupling (CPC) is based on the physiological changes in the autonomic nervous system that occur during sleep. It integrates information from the brain electrical activity through the autonomic nervous system. Analyzing heart rate variability (HRV) coupled with respiration, CPC captures the essence of sleep by looking at the ebb and flow of slow wave power that is the accepted marker of sleep drive in humans and in non-human species. The CPC-method does not rely on the same data streams as PSG and the output is not meant to match PSG, it however complements conventional sleep staging, albeit with a different method of categorizing sleep. Rather than being dependent on manual interpretation, primarily of EEG morphology, the automated output reveals that NREM sleep has a distinct bimodal-type structure marked by distinct alternating and abruptly varying periods of high and low frequency CPC-power. High frequency coupling (HFC) or stable sleep occurs during stage part of NREM-2 and all NREM-3 and is associated with periods of stable breathing, non-cyclic alternating pattern (n-CAP) EEG, increased absolute and relative delta power, strong sinus arrhythmia and blood pressure dipping. Conversely, low frequency coupling (LFC) or unstable sleep occurs during NREM-1 and part of NREM-2 and has opposite features and is characterized by temporal variability of tidal volumes, cyclic alternating pattern (CAP) EEG and non-dipping of blood pressure, lower frequency cyclic variation in heart rate. CPC defines REM sleep into Stable and Unstable REM sleep based on frequency analysis of how the dominant CPC state has been classified as vLFC, where fragmented REM sleep is often accompanied by elevated Low Frequency Coupling.
In a healthy sleep pattern, cycles between Stable, Unstable and REM sleep (NREM Stage 1, 2 and 3 & REM sleep cycles on PSG) occur every 30 – 90 minutes and approximately 4-8 cycles occur during an 8 hour healthy sleep period. The ratio of NREM sleep to REM sleep in each cycle varies during the course of the sleep period. The first episode of REM sleep may last only a few minutes, but time periods spent in REM sleep increase progressively over the sleep period, with the final period of REM sleep that may last up to 30 minutes. In summary, Stable NREM sleep (slow-wave sleep) is prominent in the first third of the night and REM sleep is prominent in the last third of the night.
Stable & Unstable Sleep (NREM sleep)
NREM Sleep accounts for 75-80% of the sleep time. During this phase, thinking and most physiological activities slow down, but movement can still occur.
Stage 1 NREM sleep = Unstable Sleep – accounts for 3-8% of total sleep period, each period is about 5-10 minutes long and occurs most frequently in the transition from wakefulness to the other sleep stages or following arousal during sleep. In stage 1 NREM sleep, alpha activity, which is characteristic of calm wakefulness, diminishes and low-voltage theta waves appear on EEG. While in stage 1 sleep, people lose awareness of their surroundings, but they are easy to wake up.
Stage 2 NREM sleep = Unstable & Stable Sleep – accounts for 45-55% of total sleep time. This is the first stage of effective sleep and each period lasts about 10-25 minutes. The characteristic EEG findings of this stage are sleep spindles believed to occur when the brain disconnects from outside sensory input and begins the process of memory consolidation and K complexes that are sort of built-in vigilance system that keep you poised to awake if necessary. Delta waves first appear during this period of sleep but are present in small amounts. Most people spend about half of the night in this stage, where eyes are still, and heart rate & breathing gradually slows down.
Stage 3 NREM sleep = Stable Sleep – accounts for 15-20% of the total sleep period. The characteristic EEG findings of this stage are that slow-brainwaves or Delta waves become dominant. The brain becomes less responsive to external stimuli, making it difficult to wake up the sleeper. Slow-wave sleep is the time for the body to renew and repair. During this sleep stage muscle tone decreases, breathing becomes more regular, blood pressure drops, and pulse rate slows. Blood flow is directed less toward the brain and at the beginning of this stage the pituitary gland releases a pulse of growth hormone (GH) that stimulates tissue growth. When a sleep deprived person gets some sleep, he or she will pass quickly through the lighter sleep stages, into the deeper sleep stages and spend a greater proportion of the sleep period in this stage. This is believed to indicate that slow-wave sleep has an essential role in a person’s optimal functioning.
REM sleep accounts for about 20% of the sleep time. Dreaming occurs during REM sleep. The first REM sleep episode occurs 60-90 minutes after the onset of NREM sleep. Characteristics of REM sleep is atonic of skeletal muscle groups, but the brain is actively thinking and dreaming as the eyes move back and forth behind closed eye lids, hence the name Rapid Eye Movements (REM). During this stage heart rate and blood pressure increase and respiration becomes irregular. Despite all this brain and eye activity, the body hardly moves, the motor function becomes “paralyzed”. Like Stable sleep (slow-wave sleep) restores the body, REM sleep or dream sleep restores the mind by facilitating learning and consolidating memories. When a person deprived of REM sleep falls asleep, he or she will enter REM sleep stage earlier and spend a higher proportion of sleep time in REM sleep.
The SleepImage System is Food and Drug Administration (FDA) cleared Software as a Medical Device (SaMD) that establishes Sleep Quality and measures Sleep Duration.
The technology is based on Cardiopulmonary Coupling (CPC) analysis of data, typically collected during sleep, derived from electrocardiogram (ECG) or photoplethysmogram (PPG) sensors.
The SleepImage System is intended for use by or on the order of a Healthcare Professional to aid in the evaluation and management of sleep disorders in children and adults.
The SleepImage System optionally analyzes SpO2 data to measure oxygen desaturation and calculate the SleepImage Apnea Hypopnea Index (sAHI) that is FDA-cleared to aid clinical diagnosis and management of Sleep Disordered Breathing (SDB) in children and adults.
The SleepImage System is patented, cloud-based and Health Insurance Portability and Accountability Act (HIPAA) compliant software.
The SleepImage System output is automatically generated and presented in an easy to understand manner, with test results for each biomarker displayed and color coded along with expected values for health care professionals to aid sleep disorder evaluation, diagnosis and management.
The SleepImage System is designed for multi-disciplinary care including non-sleep specialized clinicians for prevention or management of chronic diseases related to poor sleep quality, or presence of sleep disorders.