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Review Clinical Publications, Clinical Guide, and FAQs to learn more about Cardiopulmonary Coupling (CPC), the technology behind SleepImage®.

Clinical Publications

The SleepImage technology has been thoroughly validated in peer-reviewed publications to measure sleep quality and sleep pathology.  Click on a topic to access its content.

Clinician's Guide

The Clinician’s Guide is a comprehensive guide for clinicians that explains the CPC technology and provides clinical examples of how easy it is to read and understand wealth of data that SleepImage provides in a simple and easy format – including a decision-assist tool to help evaluate sleep disorders to inform or drive clinical management (aid diagnostic decisions).


About SleepImageĀ®


What is SleepImage?

SleepImage is an objective, accurate and easy to use system to measure sleep quality. It is FDA-cleared, clinically proven and patented technology that determines synchronization of heart rate variability and breathing activity termed cardiopulmonary coupling or CPC to provide a picture of objective Sleep Quality. 


How does SleepImage measure sleep quality?

The SleepImage CPC technology uses electrocardiogram (ECG) and accelerometer data to measure the effects of the sympathetic and parasympathetic nervous systems to determine sleep quality, objectively and accurately.

What is CPC?
CPC is an algorithm that uses mathematical analysis to determine the synchronization between modulations of heart rate variability and respiration. The algorithm calculates the percent of stable sleep, presented as high frequency coupling (HFC), unstable sleep, presented as low frequency coupling (LFC) and wake/rapid eye movement, presented as very low frequency coupling (VLFC) in their respective spectral bands. Oscillations between stable and unstable sleep are expected within an intact system to modulate in 30 – 90 minute infra radian cycles that range from 5 – 16 cycles in an 8-hour sleep period and correspond to the alternating periods of non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. Disease states negatively impact this rhythm.


How will SleepImage help me?

Users who take the initiative to become more proactive about their sleep will find using the SleepImage system an easy way to track their sleep quality over time. Good sleep quality is a vital sign of good health. Maintaining quality sleep reduces the likelihood of developing health problems over time.


What exactly does the SleepImage system track?

The SleepImage system gives you detailed analysis about your sleep quality including:

  • Total sleep time
  • Total stable sleep
  • Total unstable sleep
  • Snoring
  • Body position
  • Activity


Does SleepImage track other biometrics in sleep?

In addition to measuring sleep quality, the SleepImage system records electrocardiogram (ECG), actigraphy, snoring and body position data that is automatically analyzed. When the data is combined in the reports, they provide valuable health information about sleep quality, snoring, movement, heart rate and respiration activity in easy to read images and summary tables.


Is SleepImage a useful tool to identify insomnia?

A clinical study showed patients with chronic insomnia could be differentiated from normal sleepers with the SleepImage technology but not by standard polysomnography. Case reports indicate SleepImage technology can identify insomnia phenotypes.


Is SleepImage a useful tool to identify periodic limb movement disorder (PLMD)?

Together with activity measures, SleepImage technology can differentiate PLMD that negatively impacts sleep quality versus benign movements.


Is SleepImage a useful tool to identify restless legs syndrome (RLS)?

Together with activity measures, SleepImage technology can identify RLS and its negative impact on sleep quality versus benign movements.


Is SleepImage a useful tool to identify sleep apnea events according to the American Academy of Sleep Medicine criteria?

The SleepImage technology can automatically and accurately differentiate sleep-breathing disorders into obstructive, central and complex sleep apnea phenotypes. Automatically phenotyping sleep breathing disorders is only possible with SleepImage technology. It does not identify individual sleep apnea events, as defined by the American Academy of Sleep Medicine (AASM) criteria.


Is SleepImage a useful tool to identify upper airway resistance (UARS)?

In conjunction with its unique snore pattern detection capabilities, SleepImage technology can identify UAR and its negative impact on sleep quality.


Is SleepImage a useful tool to evaluate and track therapy efficacy?

Any intervention that has an impact on sleep can be evaluated and tracked for efficacy using SleepImage technology.


What are SleepImageā€™s recorder specifications?

The recorder dimensions are: W 1.9” D .03” H 3.1” and it weighs less than one ounce.


How many nights is it necessary to record sleep quality with SleepImage?

It is enough to record only one night to be able to get a sleep quality report.  It is however very valuable to record sleep quality consistently over time to learn what behavioral or environmental changes impact the user’s sleep quality, which are different things for different people.


About the importance of sleep

Why is sleep Important?
Sleep occupies a third of our lives and is essential for good health and well-being. Therefore it is vital to measure, know and maintain good sleep quality. The following questions and answers provide a general framework for the edification on sleep, sleep quality and the impact caused to their disruption or dysfunction.


Does poor sleep lead to poor health?

Poor sleep for an extended period of time will lead to poor health. For example, insomnia and some sleep breathing disorders are associated with increased risk of hypertension, stroke and mortality. Sleep deprivation can lead to cardiovascular disease, diabetes, obesity and some types of cancers.


Is sleep quality and sufficient sleep the same thing?

Sleep quality is not the same as sleep quantity. Spending 8 hours in bed asleep and not waking refreshed is a clear indication of poor sleep quality. Good quality sleep and sufficient sleep are both essential for maintaining good health and well-being.


Why is good quality sleep essential?

Sleep is an essential physiological process that we can’t live without. During sleep the body is hard at work repairing and rebuilding bones and muscles. It is also a time for brain reorganization; memories are consolidated so upon awakening, learned information is clear and available.


Can SleepImage help qualify sleeping aids?

The SleepImage system is a very sensitive objective measurement that can be used to determine sleep quality improvement using pharmacological and non-pharmacological aids.

In clinical trials, the SleepImage system showed sleep quality improvement in response to exercise, CPAP use, mandibular advancing splint use, psychotherapy and titrated CO2. Cases of improved sleep quality have been documented with nutraceuticals like melatonin and pharmaceutical agents like benzodiazepines.

Any sleeping aid or therapy combination reported to improve sleep can be evaluated for efficacy using the SleepImage system. By tracking stable sleep over time, this metric provides an objective guide in consultation with clinicians when discussing sleep.


Is there a link between poor sleep quality, weight loss difficulties and obesity?

Poor sleep and insufficient sleep can spur some less-than-ideal food choices, including larger food portions and craving for junk food. This is a result of hormonal changes that occur with poor quality or insufficient sleep. Six hours of sleep or less increases production of the hunger hormone Ghrelin and limits the appetite controlling hormone Leptin.
Leptin helps you balance your food intake by regulation of appetite and calorie burning. During sleep, Leptin levels increase, telling the brain you have plenty of energy for now. Decrease in Leptin as a consequence of sleep deprivation results in constant feeling of hunger and a general slow-down of your metabolism.
Ghrelin has the opposite effect of Leptin. Ghrelin tells the brain when to eat, stop burning calories and when to start storing energy as fat. During sleep, levels of Ghrelin decrease. People who don’t sleep enough end up with too much Ghrelin in their system and their body thinks it is constantly hungry and in need for calories and therefore stops burning calories and stores energy as fat.


Is there a link between poor sleep and type II diabetes?

Poor sleep quality and insufficient sleep may lead to type II diabetes by influencing the way the body processes glucose. Poor sleep leads to an increase in the production of cortisol, often referred to as the "stress hormone." Higher levels of cortisol are likely to promote the development of insulin resistance, a risk factor for diabetes.


Is there a link between poor sleep and increased blood pressure or hypertension?

Poor sleep quality and insufficient sleep can cause the body to produce more of the chemicals and hormones that lead to hypertension and heart disease. If during sleep, heart rate remains elevated and blood pressure does not decrease, as it should normally over time, then daytime blood pressure also remains high, causing the chronic elevation of blood pressure known as hypertension. This is a major risk factor for cardiovascular disease. 


Does poor sleep quality reduce alertness?

Poor sleep quality reduces alertness and can lead to excessive daytime sleepiness, fatigue, poor reaction time, and low energy with reduced performance at work, school and play.


Does poor sleep quality increase risk of accidents?

Poor sleep quality and insufficient sleep impacts the ability to interpret events. The ability to make sound decisions and to accurately make good assessments of the situation is compromised. Sleepy drivers are at a higher risk of causing an accident.


Does poor sleep quality affect mood and mental health?

Poor sleep quality or insufficient sleep influences behavioral patterns and mental health. Over time, it can contribute to the symptoms of depression. The most common sleep disorder, insomnia, is often one of the first symptoms of depression.


Is sleep important to young children?

Children ranging in age between 1 – 3 years of age require approximately 12 – 14 hours of sleep per day. Poor sleep quality or insufficient sleep may be related to daytime hypersomnolence and behavioral problems. Daytime naps, proper sleep hygiene and sufficient sleep time is required for healthy maturation during this critical growth period.


Is sleep important to children and teenagers?

Most children between the age of 8 – 12 years need 10 – 12 hours of sleep, while most teens require approximately 8 1/2 – 10 hours of sleep per day. Poor sleep quality or insufficient sleep negatively impacts learning, listening, concentration and memory. It can cause mood swings, aggressive behavior and it negatively impacts the ability to properly function, causing many children and teens to be misdiagnosed with ADD/ADHD.


Is poor sleep quality related to attention deficit hyperactive disorder (ADHD)?

Clinical evidence has shown a strong association between snoring due to enlarged tonsils and adenoids in 5 -7 year olds diagnosed with ADHD and poor sleep. Another study found children who snored were twice as likely to have ADHD. Other studies show a link between restless legs syndrome and ADHD.


Is sleep important to the skin?

Poor sleep quality or insufficient sleep suppresses secretion of human growth hormone that promotes collagen production and increases secretion of the stress hormone cortisol that in excess amounts breaks down collagen,protein that keeps skin firm, smooth and elastic. Collagen also protects against UV damage and bacterial infection, seals in moisture, improves elasticity and preserves its youthful, healthy appearance.

Poor sleep quality or insufficient sleep negatively affects the immune system and makes some teens more prone to acne.


How does sleep affect hormonal balance?

Hormonal balance is regulated by the autonomous nervous system. During good sleep, sympathetic activity is generally decreased and parasympathetic activity is increased. Endocrine organs secreting hormones are sensitive to increased sympathetic tone, associated with poor sleep. Additionally, the autonomic nervous system controls various other functions like heart rate, respiration, blood pressure, body temperature, immune system function and other body processes, all negatively affected by increased sympathetic activity.


Does insufficient sleep lead to increased inflammation?

It is well known that sleep deprivation causes loss of immune function and neuronal apoptosis. Empirical evidence shows poor sleep quality associated with chronic sleep debt and intermittent nocturnal hypoxia negatively impacts immune and endocrine function leading to increased susceptibility to infections.


How are low estrogen levels associated with sleep?

Estrogen reduces the time to fall asleep, improves sleep quality and increases the amount of REM sleep. Sleep disorders and complaints of difficulties falling asleep and staying asleep become more common in women as they progress past menopause.


How are low testosterone levels associated with sleep?

Changes in testosterone levels occur naturally during sleep, both in men and women. Testosterone levels rise during sleep and decrease during wake, with highest levels of testosterone secretion occuring during REM sleep. Lack of quality sleep or not getting enough sleep reduces the amount of REM sleep and can therefore lead to low testosterone levels which has been linked with sleep disordered breathing. Low testosterone levels can also cause sexual dysfunction both in women and men and erectile dysfunction in men.


Does poor sleep quality affect the efficacy of exercise?

Studies show a bidirectional effect of improved sleep quality and exercise. Sleep is the body’s recovery period and therefore sleep is even more important after exercise. Sleep is just as important as calories to maximize the results from exercise.


Does poor sleep quality impact work performance?

Recent reports indicate poor sleep quality is a risk factor for chronic health problems. It reduces work efficiency and presents an almost 2-fold increase of having a serious accident in the workplace. Impaired sleep increases daytime sleepiness and fatigue, which results in increased vulnerability to injury.