M. Kagawa 1 , K . Ueki 1 , A. Kurita 2 , H. Tojima 3 , and T. Matsui 1

1. Medinfo2013 Decision Support Systems and Technologies - II Non-contact Screening System with Two Microwave Radars in the Diagnosis of Sleep Apnea-Hypopnea Syndrome 21 August 2013 M. Kagawa1, K. Ueki1,A. Kurita2, H. Tojima3, and T. Matsui1 1 Faculty of System Design, Tokyo Metropolitan University, Japan 2 Fukuinkai,A Social Welfare Corporation, Japan 3 Department of Chest Medicine, Tokyo Rosai Hospital, Japan

2. Outline 1. Introduction ・Sleep Apnea-Hypopnea Syndrome and diagnosis 2. Methods ・Non-contact Vital Signs Measurement with Radars ・ Criteria for apnea/hypopneas with radars 3. Clinical Tests ・Comparison between Non-contact and Contact tests 4. Results ・ Obstructive Sleep Apnea with paradoxical movements 5. Conclusions and future work

3. 1. Introduction Sleep Apnea-Hypopnea Syndrome (SAHS) 》 High prevalence: 2-4% of the adult population (still underdiagnosed) Apnea (pauses in breathing) Hypopnea (low breathing) (1) Obstructive Sleep Apnea (OSA) ・the most common type airflow ・Collapse of the chest upper airwayin the presence of respiratory efforts • abdomen SpO2 Low blood oxygen (2) Central Sleep Apnea (CSA) airflow ・Failure of the brain to initiate chest a breath abdomen No respiratory effort SpO2 (3) Mixed Sleep Apnea (MSA)

4. The “gold standard” for diagnosis of SAHS Polysomnography (PSG) Overnight monitoring of sleep anda variety of body functions during sleep Apnea-HypopneaIndex (AHI) (the total number of apneic events per hour of sleep) 5–15/hr = mild; 15–30/hr = moderate; and > 30/h = severe brain (EEG) eye movements (EOG) muscle activity (EMG) ECG SpO2 airflow chest abdomen snoring

5. Motivation and Aim of the Project 》 Motivation: PSG with many electrodes restrain the patient and obtrusive inspection methods could disturb the measurement itself. ・ Need for diagnostic alternatives 》 Hypothesis: Displacements of respiratory movement measured by microwave radars have a linear relationship to tidal volumes. 》 Main goal: Developments of non-contact SAHS-diagnostic tools based on microwave radar sensors. ・Identifynovel SAHS features based on the amplitude analysis of chest-abdominal radar signals.

6. 2. Methods Body surface oscillation 50cm 25cm Pillow Respiration and Heartbeat R2: R1: Abdomen Chest Chest Abdomen mattress pillow mattress Control unit DC Amp. I - channel R2: Abdomen R1: Chest Q - channel A/D Conv. PC system for analysis (LabVIEW) LO Apnea/Hypopnea SASDiagnosis Event BPF Respiration FFT AGC SSA & Heart rate LPF LPF BPF : Band Pass Filter AGC : Automatic Gain Control Q-channel I-channel FFT : Fast Fourier Transform SSA : Spectrum Shape Analysis (b)Doppler-radar system and I/Q channels (a) Measurement setup and block diagram Figure 1 Monitoring system setup

7. (1) Characteristic of the radar Microwave Doppler radars (NJR4262) Pillow ・ Output power 7mW 30cm Coverage area Quadrupole plane antenna Radar1:chest (24.11GHz, 24.15GHz) Radar2: abdomen Bed Incident power density: 1.5×10-2mW/cm2< 1mW/cm2 （9.5×5.8×1.7cm） the Japanese electromagnetic wave safety guideline Compact microwave radar The electricwave of this radar is weaker than that of the mobile phone and PHS.

8. (2) Heart Beat Measurement with Radars Detecting the small vibration caused by pulse wave (heartbeats) Radar Radar Doppler detection Entry from heart Entry from heart Expansion Contraction A：Arteries (Systole) B: Arteries (Diastole)

9. (3)Samples of radar output signals respiration pulse Amplitude (V) Amplitude (V) hypopnea apnea 1 5 10 15 Time (sec) 1 20 40 60 80 (a) Slight vibrations due to Time (sec) (b) Apnea and hypopnea signal heartbeat are superimposed Figure 2 Radar output signals

10. (4) Criteria for apnea/hypopneas with radars ※ the American Academy of Sleep Medicine Our original criteria in accordance with the clinical guidelines of AASM* 》 Apnea event: radar amplitude < 20% of the baseline* baseline Amplitude (V) 》 Hypopnea event 1: 50% line radar amplitude < 50% of the baseline* 20% line 》 Hypopnea event 2: radar amplitude is 50% to 80% of the baseline* and rise of heart rates Apnea event Hypopnea event 1 is accompanied. ※ All events last 10 seconds or more. ※ Baseline changes dynamically according 1 20 40 60 80 Time (sec) to the mean value of the amplitudes of normal breathing radar signal in latest Figure 3 Criteria for Apnea and hypopnea 60 seconds. events

11. (5)Flow of the signal processing AGC : Automatic Gain Control Four radar channel signals Heartbeat signal AGC FFT Band-Pass Sampling Filter 100Hz AGC SSA Respiratory signal Peak Detection SSA : Spectrum Shape Analysis Heart rates OSA SAHS Diagnosis Apnea Hypopnea Event CSA ・Riseof heart rate MSA: Mixed Sleep Apnea ・Respiratory effort Hypopnea ・Paradoxical movement Figure 4 Block diagram of SAHS diagnosis

12. (6) Prototype of the system Radars Chest I/Q Abdomen I/Q Control unit hypopnea hypopnea (12×12×6.5cm） LAN Remote monitoring (b) Sample of monitoring display (a) Monitoring system setup Figure 5 Prototype of the monitoring system

13. 3.Clinical tests 》 Subjects: eight outpatients at the sleep disorder center (mean age 63; range 30-90, two females and six males) 》 Overnight test: between 9 PM and 6 AM the following day 》 PSG as reference data Monitoring PC R2: Abdomen R1: Chest Figure 6 The setup of the overnight test for SAHS

14. 4. Results: OSA with paradoxical movements Amplitude (V) No respiratory effort 1 10 20 30 40 50 60 Time (sec) (a) a typical central sleep apnea (CSA) Amplitude (V) paradoxical movement of the reversed phase 1 10 20 30 40 50 60 Time (sec) (b) an obstructive sleep apnea (OSA) Figure 7 Features of CSA and OSA

15. Results: Hypopnea accompanied by rise of heart rates Radar Amplitude (V) Hypopnea Hypopnea Radar Heart rate (bpm) Rise of HR Delay time 15 sec Rise of HR Delay time 15 sec 0 30 60 90 120 Time(sec) Normalized Airflow Blood oxygen level (%) Low blood oxygen Low blood oxygen Time(sec) 0 30 60 90 120 Figure 8 Features of Hypopnea

16. Results: RDIs calculated with the radar and the PSG RDI: the Respiratory Disturbance Index (the total number of apnea and hypopnea events per hour of recording ) The difference of these is small.

17. Results: Linear association and Bland Altman analysis RDIs obtained from radars and PSG correlated very closely, with a Pearson correlation coefficient of 0.98 (n=64). Difference Between RDIs 8.65: Agreement 95% confidence line RDI by radars -0.03: mean r = 0.98 -8.72: Agreement 95% confidence line RDI by PSG [times/hour] Mean value of RDI between radar and PSG [times/hour] Fig. 9 Comparison between radar test and PSG

18. 5. Conclusions and future work We have identified SAHS features based on the radar amplitude analysis. Developed SAHS diagnostic system can deal with body movement noises and positional changes in bed during sleep. (1) In a practical test at the hospital, we achieved an accurate diagnosis with RDI of SAHS (r = 0.98). (2) 》 Future work: Features abstraction of mixed sleep apnea, detection of consecutive hypopnea events. Our non-contact diagnostic system for SAHS shows great promise as a new screening system. Thank you for your attention!