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

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.