Monitoring respiration by using fiber-optic interferomtery and maximum a posteriori estimation

This paper reveals a novel approach to recognize respiration events by using an unobtrusive fiber-optic sensor. When the optical fiber is in a direct or indirect contact with human body, it detects weak contributions of vital signs. After a demodulation of fiber-optic signal, breathing can be sorted out by observing variations of heartbeat amplitudes. Introduced into a maximum a posteriori (MAP) estimation, it can locate time instants of inspirations and expirations. Estimates in experiments conducted after submaximal exercise tests in 14 young healthy subjects yield overall sensitivity 94.4±5.62% and overall precision 96.02±2.26% for inspirations. Overall mean absolute error of the inspiration onsets equals 260±143 ms. Similar figures apply to expirations.