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Diagnosis of obstructive sleep apnea using a bio-radar contact-free system compared with an established HST device in older adults

  • Author Footnotes
    # Co-first authors.
    Chuan Xiang Li
    Footnotes
    # Co-first authors.
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Department of Respiratory and Critical Care Medicine, Tongren Hospital Affiliated With Wuhan University, The Third Hospital of Wuhan, Wuhan, China
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  • Author Footnotes
    # Co-first authors.
    Yun Feng Zhang
    Footnotes
    # Co-first authors.
    Affiliations
    Department of Respiratory and Critical Care Medicine, Putuo District Liqun Hospital, Shanghai, China
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  • Author Footnotes
    # Co-first authors.
    Zheng Zhu
    Footnotes
    # Co-first authors.
    Affiliations
    Department of Respiratory and Critical Care Medicine, Putuo District Liqun Hospital, Shanghai, China
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  • Fang Ying Lu
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Yi Wang
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Li Yue Zhang
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Ning Li
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Xian Wen Sun
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Qing Yun Li
    Correspondence
    Corresponding author: Qing Yun Li, MD, PhD, Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University school of Medicine, Shanghai 200025, China. Tel.: +86-21-64370045.
    Affiliations
    Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

    Institute of Respiratory Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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  • Author Footnotes
    # Co-first authors.
Open AccessPublished:January 23, 2023DOI:https://doi.org/10.1016/j.sleh.2023.01.001

      Abstract

      Goal and aims

      To compare a bio-radar contact-free monitoring device in diagnosing obstructive sleep apnea (OSA) in older people with an established home sleep apnea testing system (HST).

      Focus method/technology

      A bio-radar contact-free monitoring device (OrbSense+).

      Reference method/technology

      An established HST, Alice NightOne.

      Sample

      Fifty-three out of 63 recruited subjects were included in the final analysis. Seventy-two percent were male (age 72 ± 9 years; body mass index 31.05 ± 5.56 kg/m2).

      Design

      An observational, prospective study.

      Core analytics

      Intraclass correlation coefficient (ICC), Bland-Altman analysis, and receiver operating characteristic analysis.

      Additional analytics and exploratory analyses

      None.

      Core outcomes

      Both 45 (84.91%) were diagnosed with OSA by Alice NightOne (average respiratory event index = 21.23 events/h) and by OrbSense+ (average respiratory event index = 25.98 events/h). Respiratory event index and oxygen desaturation index obtained by Alice NightOne and OrbSense+ were highly correlated, with ICC of 0.93 and 0.88, respectively. The Bland-Altman plot comparing the means showed good agreement between the 2 diagnostic techniques. With more than 5 respiratory events per hour as the standard for OSA diagnosis, OrbSense+ had a sensitivity of 100% and a specificity of 100% in diagnosis of OSA (P < .0001). With more than 15 respiratory events per hour as the standard for OSA diagnosis, OrbSense+ was found to have a sensitivity of 100% and a specificity of 86.96% in diagnosis of OSA (P < .0001).

      Important additional outcomes

      None.

      Core conclusion

      The bio-radar sleep monitoring device is a reasonably accurate home sleep apnea test for use in older patients.

      Keywords

      Introduction

      Rationale

      As the gold standard for obstructive sleep apnea (OSA) diagnosis, laboratory-based polysomnography is not available in many health care facilities due to equipment cost and insufficient staffing.

      Significance

      A new and effective contact-free home sleep apnea test devices for OSA diagnosis for the older population is needed.

      Background

      OSA, a common sleep breathing disorder, is characterized by the occurrence, during sleep, of cyclic episodes of complete or partial obstruction of the upper airways, affecting 936 million individuals aged 30-69 years worldwide.
      • Benjafield AV
      • Ayas NT
      • Eastwood PR
      • et al.
      Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis.
      The prevalence of OSA increases with age.
      • Gottlieb DJ
      • Punjabi NM.
      Diagnosis and management of obstructive sleep apnea: a review.
      OSA is associated with increased motor vehicle accidents, cardiovascular and cerebrovascular diseases,
      • Zapater A
      • Sánchez-de-la-Torre M
      • Benítez ID
      • et al.
      The effect of sleep apnea on cardiovascular events in different acute coronary syndrome phenotypes.
      ,
      • Ponsaing LB
      • Lindberg U
      • Rostrup E
      • Iversen HK
      • Larsson HBW
      • Jennum P.
      Impaired cerebrovascular reactivity in obstructive sleep apnea: a case-control study.
      metabolic disorders,
      • Drager LF
      • Togeiro SM
      • Polotsky VY
      • Lorenzi-Filho G.
      Obstructive sleep apnea: a cardiometabolic risk in obesity and the metabolic syndrome.
      and cancers.
      • Justeau G
      • Gervès-Pinquié C
      • Le Vaillant M
      • et al.
      Association between nocturnal hypoxemia and cancer incidence in patients investigated for OSA: data from a large multicenter French cohort.
      As the gold standard for OSA diagnosis, laboratory-based polysomnography is not available in many health care facilities due to equipment cost and insufficient staffing.
      • Gottlieb DJ
      • Punjabi NM.
      Diagnosis and management of obstructive sleep apnea: a review.
      ,
      • Collop NA
      • Anderson WM
      • Boehlecke B
      • et al.
      Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. Portable Monitoring Task Force of the American Academy of Sleep Medicine.
      With the development of home sleep apnea testing (portable monitoring technology) and relate evidence supporting the home based for OSA, home sleep apnea test devices have been recommended and are used for diagnosing of OSA in uncomplicated adult patients presenting with signs and symptoms that indicate an increased risk of moderate to severe OSA.
      • Kapur VK
      • Auckley DH
      • Chowdhuri S
      • et al.
      Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: an American Academy of Sleep Medicine Clinical Practice Guideline.
      Sleep Disorder Group of Chinese Thoracic Society; Group of Sleep Disordered Breathing, Committee of Respiratory Diseases of China Association of Medical Equipment
      Expert consensus for the use of home sleep apnea test in the diagnosis of obstructive sleep apnea in adults.
      • Jonas DE
      • Amick HR
      • Feltner C
      • et al.
      Screening for obstructive sleep apnea in adults:Evidence Report and Systematic Review for the US Preventive Sevices Task Force.
      • El Shayeb M
      • Topfer L-A
      • Stafinski T
      • Pawluk L
      • Menon D.
      Diagnostic accuracy of level 3 portable sleep tests versus level 1 polysomnography for sleep-disordered breathing: a systematic review and meta-analysis.
      However, some patients, especially old adults may not have normal sleep when using home sleep apnea test systems with numerous sensors on their body, and system and sensor failure occur and often cannot be detected and resolved in a timely manner. Thus, there is a need for new and effective contact-free home sleep apnea test devices for the older population.
      Contact-free devices are desirable due to their low disruption of sleep and real-time monitoring capability. Bio-radar contact-free devices have been validated for OSA diagnosis.
      • Zhao R
      • Xue J
      • Dong XS
      • et al.
      Screening for obstructive sleep apnea using a contact-free system compared with polysomnography.
      ,
      • Wei Z
      • Xu J
      • Li W
      • et al.
      Evaluation of a non-contact ultra-wideband bio-radar sleep monitoring device for screening of sleep breathing disease.

      Aims

      We evaluated a new home sleep apnea test, a bio-radar contact-free monitoring device (OrbSense+) for the diagnosis of OSA in older adults and compared it with an established home sleep apnea test system, a portable monitoring device (PM, Alice NightOne).

      Methods

      Sample

      During July 2021 to December 2021, 63 people age ≥60 years with snoring and suspected OSA were recruited from the sleep center of Liqun Hospital, Shanghai, China. Patients with unstable medical conditions, such as severe respiratory failure, severe heart failure, and inability to complete the sleep detection were excluded. The study was approved by the Ethics Committee of Liqun Hospital (RT201912). All subjects received detailed information about the study, and informed consent was obtained.

      Focus method/technology

      The new bio-radar contact-free monitoring device (OrbSense+, Megahealth Medical, Inc, Zhejiang, China), uses an ultra-wideband wireless radar system to provide a contact-free radar sleep monitoring, integrating radar, and biomedical engineering technologies. OrbSense+ consists of 2 components: a radar-transmitting host for tracking respiratory movements and body movements wirelessly, and a finger plethysmograph (ie, “CIRCUL”) for oxygen saturation monitoring
      • Zhao R
      • Xue J
      • Dong XS
      • et al.
      Screening for obstructive sleep apnea using a contact-free system compared with polysomnography.
      • Wei Z
      • Xu J
      • Li W
      • et al.
      Evaluation of a non-contact ultra-wideband bio-radar sleep monitoring device for screening of sleep breathing disease.
      • Liang X
      • Wang Y
      • Wu S
      • Gulliver T
      Experimental study of wireless monitoring of human respiratory movements using UWB impulse radar systems.
      (Fig. 1). The radar monitoring device was placed within 2 m of the patient, with the antenna inside the device pointed toward the patient's chest, and the CIRCUL was worn on the index, middle, or ring finger. The patient is free to change body position during monitoring. OrbSense+ can distinguish whether the patient is in the bed and changes in body position, and can detect and remove wake time data. OrbSense+ processes all signals automatically with signal processing algorithms and generates a report, including total sleep time, respiratory event index (REI), oxygen desaturation index, total number of respiratory events, mean oxygen saturation (MSaO2, %), and lowest oxygen saturation (LSaO2, %).
      • Zhao R
      • Xue J
      • Dong XS
      • et al.
      Screening for obstructive sleep apnea using a contact-free system compared with polysomnography.
      ,
      • Xue JB
      • Zhao R
      • Li J
      • et al.
      Validation of a contact-free sleep apnea monitor in adults with obstructive sleep apnea.
      Fig 1
      Fig. 1New bio-radar contact-free monitor device. New bio-radar contact-free monitor (OrbSense+), consists of 2 components, a radar transmitting host for tracking respiratory and body movement, and a ring for oxygen saturation monitoring (pulse oximeter).

      Reference method/technology

      An established portable monitoring device (PM), the Alice NightOne (Philips-Respironics, Inc, Murrysville, PA) system was used to record signals that included nasal airflow, chest and abdominal movements and pulse oximetry. The result of the PM was analyzed automatically by analysis software, and then manually interpreted again. Total number of respiratory events, REI, oxygen desaturation index, mean oxygen saturation (MSaO2, %), and lowest oxygen saturation (LSaO2, %) were calculated.

      Design, study setting, and procedures

      All patients were monitored with the OrbSense+ device and PM simultaneously in the sleep center of Liqun Hospital. We defined apnea as the complete cessation of respiratory flow for over 10 seconds, and hypopnea as a reduction in respiratory flow lasting for over 10 seconds and accompanied by oxygen desaturation of at least 3%. A REI cutoff of ≥5 events/h combined with clinical symptoms were used to define OSA. Further, the severity was classified as mild OSA (5 ≥ REI < 15), moderate OSA (15 ≥ REI < 30), or severe OSA (REI ≥ 30). All results were manually interpreted by 2 certified physicians according to the criteria in “The AASM Manual for the Scoring of Sleep and Associated Events.”
      • Kapur VK
      • Auckley DH
      • Chowdhuri S
      • et al.
      Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: an American Academy of Sleep Medicine Clinical Practice Guideline.
      If the results were different, a third physician was invited to interpret the results.

      Core analytics and main outcome variables

      Measurement data were presented as means ± standard deviation, and count data were presented as percentages (%). Agreement sleep events between the 2 diagnostic methods on sleep event were assessed using the nonparametric Wilcoxon signed-rank test. Intraclass correlation coefficients (ICC) and Bland-Altman tests were used to evaluate the agreement on REI and oxygen desaturation index from the 2 techniques. Diagnostic accuracy of OrbSense+ to discriminate OSA was quantified by sensitivity and specificity. Statistical analyses were performed using SPSS version 22.0 (SPSS Inc, Chicago, IL). P < .05 was considered statistically significant.

      Additional analytics and exploratory analyses

      None.

      Results

      Core analytics and main outcome variables

      Demographics

      The study screened a total of 63 subjects, who were all monitored with both OrbSense+ device and PM simultaneously. Ten patients were excluded because of over 2 hours without any record of breath wave or SpO2 (7 patients for PM and 3 patients for OrbSense+). Finally, 53 cases (male 71.69%, mean body mass index 30.05 ± 5.56 kg/m2, mean age 72 ± 9 years) were included in the analysis. OSA was diagnosed by PM in a total of 45 patients (84.91%) with an average REI of 21.23 events per hour. Of them, 15 patients (28.30%) had mild OSA, 16 patients (30.19%) had moderate OSA, and 14 patients (26.42%) had severe OSA. By OrbSense+, 45 patients (84.91%) met the criteria for a diagnosis of OSA, with an average REI of 25.98 events per hour, including 5 mild, 25 moderate, and 15 severe OSA, respectively (Table 1).
      Table 1The sleep parameters and obstructive sleep apnea severity obtained from 2 devices (n = 53)
      Number of patients, n (%)

      n = 53
      REI, mean ± SD

      n = 53
      ODI, mean ± SD

      n = 53
      PMOrbSense+PMOrbSense+PMOrbSense+
      No OSA8 (15.09)8 (15.09)1.86 ± 1.252.69 ± 1.521.41 ± 1.284.25 ± 2.22
      Mild OSA15 (28.30)5 (9.43)9.69 ± 2.5010.34 ± 1.457.80 ± 5.669.30 ± 0.92
      Moderate OSA16 (30.19)25 (47.17)21.59 ± 3.8921.83 ± 5.2418.85 ± 6.9719.52 ± 7.96
      Severe OSA14 (26.42)15 (28.30)44.25 ± 10.1950.55 ± 12.9239.11 ± 15.8139.59 ± 20.04
      Total53 (100)53 (100)21.23 ± 16.4625.98 ± 18.6418.44 ± 16.6721.93 ± 17.16
      PM, portable monitoring (Alice NightOne); SD, standard deviation; REI, respiratory event index; ODI, oxygen desaturation index; OSA, obstructive sleep apnea.

      Correlation and Bland-Altman analysis

      The total number of respiratory events determined by OrbSense+ (161.38 ± 126.99) was not significantly different by PM (159.30 ± 130.73), P = .199. The recording time (in minutes) by OrbSense+ (379.98 ± 69.66) was shorter than that by PM (445.88 ± 78.48), P < .001, as OrbSense+ removed awake time using signal processing algorithms, which may contribute to higher REI and oxygen desaturation index obtained by OrbSense+ (vs. PM: 25.98 ± 18.64 vs. 21.23 ± 16.46, P = .000, and 21.93 ± 17.16 vs. 18.44 ± 16.67, P = .001, respectively; Table 2).
      Table 2Comparison of sleep parameters obtained using PM and OrbSense+
      PMOrbSense+P
      Aanlysis by Wilcoxon signed-rank test.
      CoefficientP
      Intraclass correlation coefficients of PM vs. OrbSense+: 2-way random model assessing absolute agreement, for single measures.
      R
      P values were estimated by the Pearson correlation analysis.
      P
      P values were estimated by the Pearson correlation analysis.
      Number of patients5353
      Total sleep time445.88 ± 78.48379.98 ± 69.66.0000.57.0000.79<.01
      Total events159.30 ± 130.73161.38 ± 126.99.1990.97.0000.97<.01
      REI21.23 ± 16.4625.98 ± 18.64.0000.93.0000.97<.01
      ODI18.44 ± 16.6721.93 ± 17.16.0010.88.0000.89<.01
      PM, portable monitoring (Alice NightOne); REI, respiratory event index; ODI, oxygen desaturation index.
      Values are presented as mean ± standard deviation.
      a Aanlysis by Wilcoxon signed-rank test.
      b Intraclass correlation coefficients of PM vs. OrbSense+: 2-way random model assessing absolute agreement, for single measures.
      c P values were estimated by the Pearson correlation analysis.
      A good degree of agreement and reliability in the ICC was observed between 2 methods. REI and oxygen desaturation index obtained from PM and OrbSense+ were highly correlated with ICCs, as shown in Table 2 and Fig. 2. The Bland-Altman analysis revealed a high level of agreement between PM and OrbSense+ (mean bias: −4.8 events/h of REI, 95% confidence interval [CI]: −14.5 to 5.0 events/h; mean bias of −3.5 events/h of oxygen desaturation index, 95% CI: −18.9 to 11.9 events/h). Fifty-one of 53 (96.23%) points for REI and 52/53 (98.11%) points for oxygen desaturation index located within the limits of agreement and its 95% CI, which means a high agreement between both REI and oxygen desaturation index from PM and OrbSense+ (Fig. 3).
      Fig 2
      Fig. 2Correlation analysis. Plots of total respiratory events, respiratory event index and oxygen desaturation index detected by PM and OrbSense+. Each point represents the results of one subject. The solid lines are the lines of identity. P values were estimated by the Pearson correlation analysis. REI, apnea-hypopnea index; ODI, oxygen desaturation index; PM, portable monitoring (Alice NightOne).
      Fig 3
      Fig. 3Bland-Altman analysis. Bland-Altman plots of respiratory event index and oxygen desaturation index with the difference between potable PM and OrbSense+ measures plotted against the average of the 2 values. The solid line indicates the mean difference. The dashed lines show the 95% confidence intervals (CI). Fifty-one of 53 (96.23%) points for respiratory event index and 52/53 (98.11%) points for oxygen desaturation index located within the limits of agreement and its 95% CI, which means a high agreement between both respiratory event index and oxygen desaturation index from PM and OrbSense+. REI, respiratory event index; ODI, oxygen desaturation index; PM, portable monitoring (Alice NightOne).

      Receiver operating characteristic analysis

      With more than 5 respiratory events per hour as the standard for OSA diagnosis, OrbSense+ had a sensitivity of 100% and a specificity of 100% in diagnosis of OSA (P < .0001). With more than 15 respiratory events per hour as the standard for OSA diagnosis, OrbSense+ was found to have a sensitivity of 100% and a specificity of 86.96% in diagnosis of OSA (P < .0001). The area under the receiver operating characteristic (ROC) curve was used to compare the diagnostic validity of OrbSense+ vs. PM for the different cutoff points for OSA diagnosis. The values for the diagnosis of OSA were 1.000 (REI ≥5 events/h) and 0.984 (REI ≥15 events/h), respectively (Table 3, Fig. 4).
      Table 3Diagnostic validity of OrbSense+
      REI ≥ 5REI ≥ 15
      Sensitivity100%100%
      Specificity100%86.96%
      Area under the curve1.00.984
      Best cutoff point (events/h)6.8519.10
      REI, respiratory event index.
      Fig 4
      Fig. 4ROC analysis. Receiver operating characteristic plot using respiratory event index (REI) PM cutoff of 5 events/h and 15 events/h to determine sensitivity and specificity for OrbSense+ values. The values of OrbSense+ for the diagnosis of obstructive sleep apnea were 1.000 (REI-PM ≥ 5 events/h) and 0.984 (REI-PM ≥ 15 events/h), respectively. PM, portable monitoring (Alice NightOne).

      Additional analytics and exploratory analyses

      None.

      Discussion

      Main results and implications

      Worldwide, about one billion individuals are affected by OSA worldwide; however, most cases of OSA remain undiagnosed and untreated, even in developed countries.
      • Leger D
      • Stepnowsky C.
      The economic and societal burden of excessive daytime sleepiness in patients with obstructive sleep apnea.
      The “gold standard” diagnostic test is laboratory-based polysomnography, which is labor-intensive and inconvenient for the patient. Portable monitoring has been proposed as a reasonable substitute for in-laboratory polysomnography in most patients, except for those with severe cardiopulmonary or neuromuscular diseases.
      • Wei Z
      • Xu J
      • Li W
      • et al.
      Evaluation of a non-contact ultra-wideband bio-radar sleep monitoring device for screening of sleep breathing disease.
      ,
      • Zhou Y
      • Shu D
      • Xu H
      • et al.
      Validation of novel automatic ultra-wideband radar for sleep apnea detection.
      In recent years, portable sleep monitoring devices using contact or contact-free sensor technology at home have greatly reduced barriers to diagnosis and facilitated routine management of OSA. In addition, portable monitoring enabled continued testing during the coronavirus disease 2019 pandemic.
      • Miller MA
      • Cappuccio FP.
      A systematic review of COVID-19 and obstructive sleep apnoea.
      Furthermore, contact-free devices used at home may show greater value due to their low less disruption of intervention on sleep, especially for older adults, who may not sleep normally in a hospital bed with numerous sensors on their body.
      OrbSense+, a contact-free sleep test device, has been used in the screening and diagnosis of OSA.
      • Xue JB
      • Zhao R
      • Li J
      • et al.
      Validation of a contact-free sleep apnea monitor in adults with obstructive sleep apnea.
      ,
      • Zhou Y
      • Shu D
      • Xu H
      • et al.
      Validation of novel automatic ultra-wideband radar for sleep apnea detection.
      Our study compared the effectiveness of OrbSense+ with an established portable monitoring device (Alice NightOne) in older adults. The failure rate of OrbSense+ and PM was about 4.8% and 11.1%, respectively, which was similar to other portable monitoring devices.
      • Flemons WW
      • Littner MR
      • Rowley JA
      • et al.
      Home diagnosis of sleep apnea: a systematic review of the literature. An evidence review cosponsored by the American Academy of Sleep Medicine, the American College of Chest Physicians, and the American Thoracic Society.
      Fifty-three out of 63 recruited subjects were included in the final analysis. Forty-five (84.91%) were diagnosed with OSA by portable monitoring device (average REI = 21.23 events/h); similarly, 45 patients (84.91%) were diagnosed with OSA by OrbSense+ (average REI = 25.98 events/h). REI and oxygen desaturation index obtained by portable monitoring device and OrbSense+ were highly correlated, with ICC of 0.93 and 0.88, respectively. The Bland-Altman plot comparing the means showed good agreement between the 2 diagnostic techniques. As showed in Fig. 2, 2 cases for REI and 1 case for oxygen desaturation index showed significant difference between the 2 methods, but the difference did not affect diagnosis or the identification of the degree of severity. ROC analysis showed OrbSense+ had a high sensitivity and specificity in diagnosis of OSA; the values for the diagnosis of OSA were 1.000 (REI ≥5 events/h) and 0.984 (REI ≥15 events/h), respectively. In summary, our results suggested that contact-free monitoring can be useful in diagnosing older patients suspected of having OSA.

      Additional results and implications

      None.

      Limitations and future perspectives

      This study has several limitations. First, the small sample size may result in statistical bias. In the real world, diagnosis of OSA in older adults may be affected by confounding factors, especially the potential coexistence of chronic diseases (eg, chronic obstructive pulmonary disease, heart failure), which may need further investigation. Second, although OrbSense+ processes all the signals using signal processing algorithms, which can remove awake time and calculate total sleep time, no study has demonstrated the accuracy and the agreement between total sleep time as detected by bio-radar contact-free sleep monitoring vs. laboratory-based polysomnography; therefore, REI instead of apnea hypopnea index was used in this paper. Third, OrbSense+ currently can record only one night of data indicating a need for further development. Fourth, another limitation of the study is that the accuracy of the OrbSense+ was tested against only one type of portable monitoring device and the results may not generalize to other portable monitoring devices or to PSG.

      Core conclusion

      In conclusion, a bio-radar contact-free sleep monitoring device with a finger plethysmograph enabled diagnosis and evaluation of the severity of OSA in older adult. This device is promising for in clinical diagnosis, treatment follow-up, and population-based epidemiologic studies of OSA.

      Declaration of conflict of interest

      The authors have no conflicts to declare.

      Funding

      This work was supported by grants from the National Natural Science Foundation of China (grant numbers 82070089 and 81770084); Shanghai Putuo District Health System Science and Technology Innovation Project (grant number ptkwws201917); Shanghai Putuo District Clinical Specialty Project-Chronic Obstructive Pulmonary Disease (grant number 2020tszb05); Shanghai Municipal Key Clinical Specialty (grant number shslczdzk02202); Shanghai Top-Priority Clinical Key Disciplines Construction Project (grant number 2017ZZ02014); and National Key R&D Program of China (grant number 2018YFC1311900).

      Data sharing statement

      No additional data are available.

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