Sleep monitoring comes home
by Amy Aronsky, DO, FAASM, FCCP
March 15, 2018

We now live in a world where people can heal and age at home, and tools to evaluate sleep at home are readily available. Advances in technology can be used at home to diagnose sleep disorders, assess response to sleep therapies, monitor sleep quality and assist with improved sleep techniques. In this real-world environment, people are able to better understand their own sleep patterns.

When partnered with guidance from their health care professional, patients benefit from a customized wellness program using home sleep monitoring, whereby improved sleep becomes the cornerstone of good health.

Evaluation for sleep disorders, such as obstructive sleep apnea (OSA), has traditionally been assessed in the sleep laboratory using polysomnography. Attended in-laboratory polysomnography is a comprehensive recording of sleep which monitors, at least, electroencephalography (EEG), electrocardiography (ECG), electrooculography (EOG) and electromyography (EMG), pulse oximetry and respiratory effort.

Polysomnography remains the gold standard to evaluate sleep disorders. Sleep laboratories were originally located in hospitals, but many have since migrated to free-standing centers. In the sleep laboratory, individuals are observed and sleep is monitored. Sensors and corresponding wires are applied to assess physiologic parameters of sleep. The application of monitoring equipment may take up to 60 minutes and provides a detailed analysis of sleep stages, body movements and cardiorespiratory parameters.

Home Studies and Treatment

During the last 10 years, home sleep testing has been used to diagnose obstructive sleep apnea in persons without significant comorbid medical conditions, such as congestive heart failure (CHF) or chronic obstructive pulmonary disease (COPD). The prevalence of obstructive sleep apnea associated with accompanying daytime sleepiness is approximately 3 to 7 percent for adult men and 2 to 5 percent for adult women in the general population. The prevalence among obese patients exceeds 30 percent, reaching as high as 50–98 percent in the morbidly obese population. Despite growing knowledge of OSA, most patients go undiagnosed.

Testing for this common sleep disorder is easily accomplished in the home setting. Sleep testing at home is more convenient and accessible for people who prefer to avoid sleeping in the sleep laboratory, or for those whom a testing facility is not readily accessible. In addition, a home sleep test may provide a more representative assessment, as the patient is sleeping in their own bed and environmental conditions.

Home sleep tests cost approximately 75 percent less than sleep testing in the laboratory and are therefore an efficient alternative when there is a high pretest probability of diagnosing OSA. Home sleep tests monitor at least three parameters, including pulse oximetry and respiratory effort. Since this type of test is unmonitored in the home, patients must be able to follow simple instructions to successfully use the equipment.

Treatment Advances in CPAP

Once a diagnosis of obstructive sleep apnea is made, most patients are treated with continuous positive airway pressure (CPAP). CPAP is a non-invasive method of respiratory ventilation which delivers a constant flow of air pressure to the airway through a pressurized mask. This air pressure serves as a pneumatic splint to enable the collapsing airway to remain patent.

CPAP machines also have “smart technology,” which enables the assessment to be downloaded and/or transmitted through cellular, wireless or Bluetooth technology. The health care professional can then review the patient’s use of the device almost immediately. This allows for evaluation of the patient’s hours of PAP use nightly, evidence of mask leakage, measurement of CPAP pressure settings, the effectiveness of the therapy, and device troubleshooting. With this information available, health care professionals can offer almost real-time evaluation and feedback, allowing CPAP changes to be made swiftly in order to improve patient compliance and clinical outcomes.

Additionally, several CPAP manufacturers offer patients mobile applications for their wireless devices that synchronize with the CPAP machine, which means that patients can obtain information describing their sleep quality and CPAP efficacy upon awakening. This information may be used to track trends in sleep patterns and to provide feedback to the health care professional.

Another type of CPAP device used to treat OSA is an auto-adjusting CPAP, or APAP. The APAP is set at a range of pressures and the pressure is variable with each patient breath. For example, patients who sleep on their back will likely have more severe OSA. APAP algorithms determine the appropriate therapeutic air pressure and deliver the pressure through the patient’s mask with each breath. When the patient does not sleep on the back, OSA is typically less severe, and a reduced APAP pressure is delivered. Using variable pressures, the APAP self-adjusts to the patient’s breathing at home, eliminating the need for patients to return to the sleep laboratory for a second in-facility sleep test conducted with the PAP machine. Often, APAP is also considered to be more comfortable for the patient.

Device Improvements Expand Monitoring

Advances in technology mean that detailed physiologic sleep information can be monitored at home. Recent developments allow for home sleep-based monitoring of brain activity. These devices have a headband which monitors brain activity using a limited EEG.

Sleep monitoring based on autonomic signals applies sensors to the chest wall to measure cardiorespiratory physiologic changes that suggest sleep and OSA, and may facilitate diagnosis of additional sleep disorders (beyond OSA) in the home in the near future.

Sleep trackers have increased in popularity and are readily available to consumers. These devices can be synchronized to mobile applications and provide sleep information to the user. While these devices have limited clinical validation studies, they are often useful to observe trends in sleep over a period of time.

Wearable sleep and fitness trackers, such as Fitbit, monitor sleep based on movement. These devices are typically worn on the wrist and provide metrics such as sleep duration, sleep latency, and the number of awakenings from sleep. Non-wearable trackers are bed-based devices placed inside the mattress or pillow. These sensors may record several parameters, such as respiration, heart rate, movement and snoring.

Novel monitoring devices include sensors embedded in shirts and vests to measure sleep quality. A leading PAP manufacturer has developed a sleep tracker that obtains data through radiofrequency technology to measure respiration and body movement without any direct physical contact.

Other home sleep devices have the ability to play music and sound for relaxation or emit a light to assist in waking up from sleep using circadian rhythm physiology. Online sleep diaries may be used by patients to report sleep symptoms remotely to health care professionals.

New technology has allowed the study of a person’s sleep to move from the clinical sleep laboratory to the bedroom. At home, innovative technology may be leveraged to diagnose sleep disorders, observe treatment response and to assess overall sleep quality. When this data is reviewed with a health care professional, home sleep monitoring becomes a component of an overall wellness program and a person’s good health.