Estimation of Body Movement with Optical Fiber Pressure Sensor

For assessment of body movement during sleep, a system for monitoring pressure in bed has been developed. The system consists of an optical fiber pressure sensor and a notebook personal-computer with A/D converter. The changes in optical density due to changes in pressure was detected and converted with A/D converter and transferred to computer. Preliminary study showed the pressure distributions of head, back, and hip were relatively high. Thus three optical fiber sensors were arranged in above positions. The changes in posture and body movement were recognizable from the changes in pressure. The time of body movement was estimated from the derivative of pressure signal. The time of body movement was determined when two of three signals were changed. In comparison with the video recording, this estimation showed good agreement. The pressure measurement in bed provides a high resolution posture change during sleep.