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Non-contact diagnostic system for sleep apnea–hypopnea syndrome based on amplitude and phase analysis of thoracic and abdominal Doppler radars

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Abstract

Full-night polysomnography (PSG) has been recognized as the gold standard test for sleep apnea–hypopnea syndrome (SAHS). However, PSG examinees are physically restrained for the full night by many contact sensors and obtrusive connecting cables, inducing mental stress. We developed a non-contact SAHS diagnostic system that can detect apneic events without inducing stress in monitored individuals. Two Doppler radars were installed beneath the mattress to measure the vibrations of the chest and abdomen, respectively. Our system determines apnea and hypopnea events when the radar output amplitude decreases by <20 and 70 %, respectively, of the amplitude of a normal breath (without SAHS events). Additionally, we proposed a technique that detects paradoxical movements by focusing on phase differences between thoracic and abdominal movements, and were able to identify three types of sleep apnea: obstructive, central, and mixed. Respiratory disturbance indexes obtained showed a higher correlation (r = 94 %) with PSG than with pulse oximetry (r = 89 %). When predicting the severity of SAHS with an apnea–hypopnea index (AHI) of >15/h or >30/h using PSG as a reference, the radar system achieved a sensitivity of 96 and 90 %, and a specificity of 100 and 79 % with an AHI of >15/h and >30/h, respectively. The proposed radar system can be used as an alternative to the current airflow sensor, and to chest and abdomen belts for apnea–hypopnea evaluation.

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Acknowledgments

This research was partially supported by the Ministry of Internal Affairs and Communications (MIC, Japan), Strategic Information and Communications R&D Promotion Programme (SCOPE), and Japan Society for the Promotion of Science KAKENHI (Grant Number 26350507).

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Authors and Affiliations

  1. Faculty of System Design, Tokyo Metropolitan University, 6-6 Asahigaoka, Hino, Tokyo, 191-0065, Japan

    Masayuki Kagawa & Takemi Matsui

  2. Department of Respiratory Medicine, Tokyo Rosai Hospital, 4-13-21 Omori-minami, Ohta-ku, Tokyo, 143-0013, Japan

    Hirokazu Tojima

Authors
  1. Masayuki Kagawa
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  2. Hirokazu Tojima
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  3. Takemi Matsui
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Correspondence to Masayuki Kagawa.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

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Kagawa, M., Tojima, H. & Matsui, T. Non-contact diagnostic system for sleep apnea–hypopnea syndrome based on amplitude and phase analysis of thoracic and abdominal Doppler radars. Med Biol Eng Comput 54, 789–798 (2016). https://doi.org/10.1007/s11517-015-1370-z

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  • DOI: https://doi.org/10.1007/s11517-015-1370-z

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