Non-contact screening system for sleep apnea-hypopnea syndrome using the time-varying baseline of radar amplitudes

Abstract

The gold standard test for sleep apnea-hypopnea syndrome is full-night polysomnography (PSG). However, PSG with multiple electrodes is extremely stressful for patients. We have developed a non-contact screening system using two Doppler radars. We propose two methods for the diagnosis: the first is a time-varying amplitude baseline method, and the second is a hypopnea detecting technique that focuses on an increase in heart rates. Using radar signals we detected respiratory effort and the paradoxical movements between chest and abdomen, and demonstrated the ability to identify the three types of sleep apnea. Our developed system was evaluated on 31 outpatients at a hospital. The simultaneous comparison of our system with PSG showed that the respiratory disturbance indexes obtained from radars correlated very closely (90% accuracy) with those from PSG.

Contact-Free Detection of Obstructive Sleep Apnea Based on Wavelet Information Entropy Spectrum Using Bio-Radar

“…For the non-stationary OSA respiratory radar signal, the traditional signal processing method in time domain used the amplitude variations [17] or energy variations [18][19][20] of breathing signals. These methods were easily realized, but the detection accuracy could be affected by the changes of human subjects' posture and the distance of bio-radar.…”

“…Lee [16] thinks that the breathing rate resulting from the radar Doppler shit of human breathing could be used to distinguish various types of respiratory scenarios. Masayuki Kagawa [17] chooses the variation of respiratory amplitudes to identify three types of sleep apnea. Besides, the characteristics of energy between the normal respiratory and apnea [18][19][20] and series of absolute values of wavelet decomposition detail coefficients of signal quadrature components [21] were also selected to make a sleep apnea judgment.…”

“…The energy or amplitude of the Doppler radar is likely to be influenced by the body position and posture in bed. Besides, there is also a non-linear relationship between radar amplitudes and tidal volumes [17]. This means that the radar respiratory amplitude does not represent real ventilation and it tends to be an apparently slightly bigger radar amplitude but there are few actual respiratory ventilation situations during some apnea cases.…”

Analysis of Efficient Biometric Index using Heart Rate Variability for Remote Monitoring of Obstructive Sleep Apnea

“…Qi, et al developed a technique using wavelet information entropy spectrum to judge OSA respiratory signal detected by bio-radar in wavelet domain [24]. However, infrared sensors require strict positional restraints and the region of interest must not be blocked [23]. These constraints are not easily be satisfied during natural sleep.…”

“…Pereira, et al proposed an algorithm for remote monitoring of breathing rate by means of infrared thermal imaging [22]. Kagawa, et al proposed a method for identifying the three types of sleep apnea on basis of time fluctuating baseline of radar amplitudes [23]. Qi, et al developed a technique using wavelet information entropy spectrum to judge OSA respiratory signal detected by bio-radar in wavelet domain [24].…”