Why Home Testing

Validation of a Self-Applied Unattended Monitor
for Sleep Disordered Breathing

Indu Ayappa, Ph.D.; Robert G. Norman, Ph.D.; Vijay Seelall, M.D.; David M. Rapoport, M.D.
Division of Pulmonary and Critical Care Medicine, New York University School of Medicine, New York, NY

Study Objectives: To evaluate the validity of the Apnea Risk Evaluation System (ARES™  ) Unicorder, a self-applied, limited-channel portable monitoring device for the evaluation of sleep disordered breathing (SDB).
Design: Prospective study with blinded analysis.
Setting: Sleep disorder center, academic institution.
Participants: Eighty patients with suspected obstructive sleep apnea hypopnea syndrome (OSAHS) and 22 volunteers.
Interventions: N/A.

Measurements and Results: Subjects used the ARES™ Unicorder at home for 2 nights using only written instructions. Within 2 weeks, they returned to the laboratory for full nocturnal polysomnography (NPSG) with simultaneous monitoring with the Unicorder. NPSGs were scored manually to obtain an apnea-hypopnea index based on Medicare guidelines (AHI4%) and a respiratory disturbance index (RDI). ARES™ studies were autoscored and reviewed to obtain indices based on equivalent definitions i.e., AHI4% ARES and apnea hypopnea (events with 1% desaturation) index (AHI1%ARES ). Indices from the NPSG were compared to the in-lab ARES™ and in-home ARES™ indices using mean differences and the intraclass correlations (ICC). For the in-lab comparison, there was high concordance between AHI4%NPSG and AHI4%ARES (ICC = 0.96, mean difference = 0.5/hour) and RDINPSG and AHI1%ARES (ICC = 0.93, mean difference = 3.2/hour). For NPSG versus In-Home ARES™ comparison, there was good concordance between AHI4%NPSG and AHI4%ARES (ICC = 0.8, mean difference = 4.1/ hour) and RDINPSG and AHI1%ARES (ICC = 0.8 mean difference = 8.6/ hour). The diagnostic sensitivity of in-lab ARES™ for diagnosing SDB using an RDI cut-­off of 15 per hour was 95% and specificity was 94%, with a positive likelihood ratio (LR+) = 17.04, and negative likelihood ratio (LR-) = 0.06. For in-home ARES™ data the sensitivity was 85% and specificity 91% (LR+ = 9.34, LR-­ = 0.17). There was good agreement between the manually scored NPSG SDB indices and the autoscoring ARES™ algorithm.

Conclusions: ARES™ Unicorder provides acceptably accurate estimates of SDB indices compared to conventional laboratory NPSG for both the simultaneous and in-home ARES™ data. The high sensitivity, specificity, and positive and negative likelihood ratios obtained in the group we studied supports the utility of an ambulatory limited-monitoring approach not only for diagnosing sleep disordered breathing but also to rule out SDB in suitably selected groups.

Keywords: Sleep disordered breathing, home monitoring, obstructive sleep apnea/hypopnea syndrome, diagnosis, portable monitoring

Citation: Ayappa I; Norman RG; Seelall V; Rapoport DM. Validation of a self-applied unattended monitor for sleep disordered breathing. J Clin Sleep Med 2008;4(1):26-37.

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Sleep testing should not be conducted
like a medical experiment

Photo Courtesy of Bob Martin
Martin's Mercurial Musings
From the unfamiliar walls of a medical facility or hospital to an altered hotel room, the attempt to provide a comfortable environment to diagnose sleep apnea remains a problem. It is often difficult to schedule a convenient time for an overnight stay. Leaving loved ones for an evening or two and arranging care for your children or pets is not conducive to recording an accurate sleep study.

A conventional sleep study will require you to travel to the sleep lab. Once there, expect to be observed and filmed all night. The technician will apply 15 electrodes to your head and face with numerous sensors placed all over your body. If the unfamiliarity of sleeping in a different bed with cables attached to you is not intrusive enough you may find comfort in knowing someone is watching you all night.

Log Z's does not recommend this conventional method for making the diagnosis of Obstructive Sleep Apnea. Log Z’s does recommend a full sleep study to make the diagnosis of Narcolepsy, Restless Leg Syndrome, identify Parasomnias such as Night Terrors and possibly Circadian Rhythm Disorders, however these sleep disorders combined do not make up 10 percent of all referrals to a sleep facility.

Home sleep study is convenient, fast and effective

Due to modern advances in sleep science, it is no longer necessary to travel to a hospital or an unfamiliar sleep lab to make the diagnosis of Obstructive Sleep Apnea (OSA). With today’s technology a patient does not need to endure the application of the cumbersome 21 electrodes and sensors originally required to make the diagnosis of OSA. Our approach allows patients to be tested in the comfort of their own home with as little technical intervention and disruption of their daily routine as possible. This approach to Polysomnography (PSG) can be achieved while maintaining the highest quality of sleep medicine.

The equipment is sophisticated enough to make quick, accurate diagnoses. Yet, to the patient, the simplicity of the equipment ensures minimal interference with their normal sleep schedule: the equipment can easily be set up for their night study without assistance from a technician. Instruction on the use of the equipment takes less than 10 minutes to complete by a trained staff member This patient interaction encourages commitment from the patient that they will follow through with the doctor’s orders. The physician’s staff will be educated on how to properly instruct the patient on initiating the study. Furthermore, Log Z’s will compensate the instructor’s practice for educating each individual patient that undergoes a sleep study.