A microcomputer-based respiratory and activity recording system

A respiratory and activity recording system has been developed for monitoring health conditions and living patterns, such as activity/rest time periods and general activity level. The system employs a piezoelectric sensor, a low-power operational amplifier, a low-power 8-bit microcomputer and a 512 KB EEPROM. The piezoelectric sensor, whose electrical polarization voltage is produced by mechanical strain, records body movements produced by respiration, heart pulse, walking and running. The high and low frequency components from the recorded body movements are discriminated by high and low pass filters. The high frequency components reflect the body movements produced by cardiac vibrations, walking and running activities. The low frequency components are mainly generated by respiration. The degree of activity is obtained by summing the high frequency components for 1 second. The microcomputer stores the obtained low frequency components and activity to the EEPROM at 0.2 second and 1 second intervals, respectively. After recording, these stored data are downloaded to a desktop computer. The computer then detects behavior patterns from the activity data and respiration from the low frequency components.