Home sleep testing devices are more reliable, portable, and user-friendly than ever before. The future may bring individualization, real estimates of actual sleep time, and even contactless sensors.
The groundwork for home sleep testing (HST) began in the mid to late 1980s when clinicians developed indications and standards for cardiopulmonary sleep studies and there was a growing interest in ambulatory monitoring of arterial oxygen saturation, according to Nathaniel F. Watson, MD, MSc, president of the American Academy of Sleep Medicine (AASM).
“Sleep scientists always have been intrigued by the possibility of gathering more accurate sleep data by monitoring subjects in their accustomed bedroom environment at home rather than in the unfamiliar confines of the sleep lab,” says Watson, who is also professor of neurology at the University of Washington in Seattle, co-director of the University of Washington Medicine Sleep Center, and director of the Harborview Medical Center Sleep Clinic. “In the 1990s, there arose a greater awareness of both the high prevalence of obstructive sleep apnea [OSA] and the severe health consequences of untreated OSA, which created a greater sense of urgency to develop alternative, cost-effective methods to expedite diagnostic testing for more patients.”
These early devices were strikingly primitive by today’s standards. Sara Weimer, director of Sleep Products & Services for CleveMed, says many attempted to replicate the in-lab experience in the home. “Many of the patients were homebound, so they needed a technician on hand,” she says.
And the amount of data these devices could measure was limited, to say the least. “In the mid-1990s, most HST devices only measured one parameter at a time, for instance,” says Christie Rose, senior manager of product management, Respiratory Care, Diagnostics for ResMed. “The early HST devices could measure snoring and, eventually, were updated to include percent SpO2, pulse rate, oral/nasal airflow, respiratory effort, and body position.”
The early devices were about the size of a large portable cassette recorder/player, and were clunky and heavy. They recorded data on an eight-channel cassette tape for a maximum duration of 8 hours, according to Edmund Shaw, MBA, RPSGT, senior global product manager for Philips Respironics. “The lab primarily used them for research and differential diagnosis of depression and insomnia,” he says. “The previous channel configuration did not include effort, SpO2, or snoring.”
In addition, they weren’t user friendly, and not necessarily reliable either. “Once the electrodes were applied, the only way to check data quality was to connect it to a pen and paper PSG,” Shaw says. “The patient had to start the device by moving a switch and closing a gate to engage the write-head. If either step was omitted, the recording was lost.”
While Shaw may recall a device that wasn’t ideal, Robert Owens, MD, assistant professor of medicine at the University of California San Diego (UCSD), remembers a device that was effective—though he admits the early devices required a patient who was “on the ball” to properly attach the electrodes and use the interface.
The technical success of these tests, according to Owens, was only 70%-80% effective, and they had another limitation. They were used essentially as a fait accompli. “When HSTs came out, they were mainly used on patients that already had pretested for a high probability of sleep apnea,” he says. “They were designed knowing the patient had sleep apnea.” Owens in 2015 coauthored a paper that predicts where OSA diagnostics and therapeutics are headed next, including detailing what improvements the industry can expect from HSTs.1
Today HST is no longer used to simply confirm a diagnosis that was arrived at by other means. In conjunction with proper pretest screening, HST is now frequently used to diagnose OSA.
There are three causes for this shift, according to Owens: patient acceptance, cost, and access.
Of the three, cost is perhaps the most compelling factor. The move to HST has been fueled, in part, by the payors, says Owens. “In-lab testing requires paying for space, technicians, and scoring. We can’t pay for everybody to test in lab,” he says.
Awareness of sleep disorders as an important medical issue is also helping to create HST acceptance among patients and clinicians. “Physician awareness of obstructive sleep apnea as an important medical issue has been driven primarily by public awareness efforts or organizations such as the American Academy of Sleep Medicine, and by a wealth of scientific research showing that untreated OSA is destructive to a patient’s health and well-being,” says AASM’s Watson. “Although some patients still prefer to be monitored by a sleep professional during a study at a sleep center, others enjoy the comfort and convenience of sleeping in their own bedroom during a home sleep apnea test.”
But most important is the technical success rate of HST. Based on his clinic experience, Owens says that today’s HST has a success rate of at least 90% (and, if a test fails, it is relatively easy to retest a patient).
Helping with this success rate is not only improved, user-friendly devices that are portable, intuitive, and reliable, but the amount of data that these devices can capture. “The usability of today’s devices is definitely much better than past devices, and this is crucial when it comes to reliable results. This is why the Alice NightOne has worked so well—it uses clear, intuitive icons to guide the patient through setup, making for a more user-friendly experience,” says Philips’ Shaw. “Unlike previous devices, today’s devices also are able to store multiple recordings with a built-in memory.”
In addition to the amount of data, the type of data often equals what could have been captured by a traditional in-lab test. “The first FDA-approved device measured snoring only, then the second device incorporated pulse oximetry with snoring, giving heart rate, SpO2, and snoring to analyze. Respiratory effort, flow, actigraphy, and body positioning were eventually added to devices. More complicated devices do exist, including the ability to monitor EEG, ECG, and EMG,” says ResMed’s Rose, though she says added monitors sometimes have the unintended effect of being more cumbersome for the patient. ResMed’s current Type III device, ApneaLink Air, has four channels including flow, effort, heart rate, and SpO2.
Other companies, such as SOMNOmedics, have developed scalable devices that go beyond the AASM guidelines and will grow with the needs of patients and clinicians alike. “We’ve created a device that minimizes the failure rate and is flexible enough to adapt to the industry,” says Julia Sarmiento, director, SOMNOmedics America. “We can measure one to 10 channels, including EEG, airflow, snoring, plethysmography, and leg movement. It’s battery powered, has a touchscreen, can be set up on the fly, and results can be uploaded or downloaded. The device has 512 MB storage, and we can customize it however the clinician wants. A signal check can be done prior to leaving the office and doing the test. That way the clinician and patient know there’s a signal, and it helps with the success rate.”
Weimer of CleveMed notes that her company’s device is very user-friendly and simplified, with indicator lights and fewer connections needed, consequently less training is required, giving the patient an increased level of confidence when using the device. “A more confident patient reduces the labor requirements for the sleep lab,” she says.
HST is here to stay, and there is little doubt the devices will continue evolving. But what specific improvements can we expect in the future?
“HST will be the same, but look different,” predicts Weimer of CleveMed. “We’ll be able to measure time and position and maybe wake, REM, and non-REM sleep. Sensors will become more comfortable. We may be using a different part of the body as a measuring point in the future.”
While UCSD’s Owens foresees more high tech in the future, such as “tattoo” electrodes (stick-on bendable sensors that bond to the skin in a similar way as temporary tattoos), he notes that there’s something even more fundamentally necessary. “We need an objective measure of sleep,” he says. Sleep duration is not recorded during HST; practitioners are therefore reliant on total recording time rather than total sleep time to calculate time-derived indices such as AHI.
On its website, Itamar Medical says its HST, the WatchPAT, does measure true sleep time. Citing a study in JAMA Otolaryngology-Head & Neck Surgery,2 Itamar states, “WatchPAT with its innovative peripheral arterial tone (PAT) signal is the only FDA-cleared HST device that measures true sleep time (rather than the total device recording time) and all sleep stages (wake, light sleep, deep sleep, and REM sleep) with up to 90% correlation to a PSG test.”
Other HST equipment providers also already have at least one foot squarely in the future. SOMNOmedics’ device is scalable, offering up to 10 channels and a high level of customization, and other providers are giving clinicians more tools for their diagnostic toolboxes.
“We can already record body position and a patient’s apneas per body position with ResMed’s ApneaLink Air,” says ResMed’s Rose. “And ResMed’s general consumer sleep tracker, S+, records the time someone spends in each stage of sleep. The S+ is not a diagnostic tool. Our engineers have made incredible strides in these areas, and are always looking for ways to leverage these advancements to give patients and providers the data they need to make better care decisions.”
Philips’ Shaw notes that the ability to make the determination between wake, non-REM, and REM sleep—the holy grail of sleep testing—may be right around the corner. “We are currently able to record body position with the Alice PDx and Alice NightOne, but there are several physiologic parameters that can be correlated in a sleep state, so it seems likely that the determination of wake, REM, and non-REM sleep without the use of electrodes will become more common,” he says.
One of the biggest complications in HST historically has been the need to use patient contact points—either electrodes, pulse oximeters, or sensors around the cannula. One solution is more comfortable sensors—as Weimer suggests—or the ability to measure patients’ sleep without contact. Weimer, for her part, is skeptical that this is a possibility. “Contactless is intriguing, but I’m doubtful how much info you can truly get, and what the correlation is to traditional sensors. There’s more research needed,” she says.
Jeremiah Sparks, director of marketing and reimbursement strategy for Itamar, sees contactless devices as less of a pressing issue. “Contactless HST is the future of the future,” he says. “The future is going to be less about technology and how we screen and treat patients. There will be more collaboration between different medical specialties such as cardiology and endocrinology.”
Shaw notes that, as with HST in general, it will likely be up to the payors for contactless devices to see development and wide adoption. “There are several contactless devices on the market; however, in order for them to become more widely adopted, payors are going to have to accept them,” he says.
ResMed for its part has already jumped into the contactless pool. “Contactless sleep sensors are already here!” says Rose, referring to ResMed’s S+ non-contact sleep tracker released in October 2014. “This personalized sleep solution uses patented bio-motion sensors, designed to measure an individual’s sleep stages and environment, and delivers personalized feedback that helps improve sleep from the very first night. Again, S+ is not a diagnostic tool recommended for clinical use; it is available over the counter to help people improve their nightly sleep.”
The future also will almost certainly include more convergence of clinical and consumer technology such as the Fitbit and the Apple Watch, which Sparks thinks will be used as a “screener” to help patients identify potential problems or as a high-tech sleep diary to help patients manage their sleep health.
Owens notes that HST could be helpful in developing more individualized treatments for patients instead of just blanket prescriptions of CPAP. “If a patient has mild OSA and isn’t happy about CPAP, we can advise them to lose weight, or cut back on alcohol, or change their sleeping position—and reinforce what’s working and not changing behavior,” he says.
In the future, HST might be the key to monitoring patients regularly, easily, and economically. “With the home test, we diagnose the problem and don’t look again,” Owens says. “If we had the ability of testing regularly, that would be very powerful.”
While researching this article, Los Angeles-based writer C.A. Wolski had his Fitbit strapped to his wrist measuring how much sleep he was getting. While it may not be as accurate as a home test, he remarked: “It did get me thinking about how well I’ve been sleeping.”
1. Malhotra A, Orr JE, Owens RL. On the cutting edge of obstructive sleep apnoea: where next? Lancet Respir Med. 2015;3(5):397–403.
2. Yalamanchali S, Farajan V, Hamilton C, et al. Diagnosis of obstructive sleep apnea by peripheral arterial tonometry. JAMA Otolaryngol Head Neck Surg. 2013;139(12):1343-1350.