Non-contact respiratory monitoring system using a ceiling-attached microwave antenna

Using a microwave antenna attached to the room ceiling, we conducted non-contact monitoring of respiratory chest wall motions of subjects in bed and covered by a soft comfortable bedding, to measure the vital signs of patients under nursing care in a welfare institution. Long-term vital sign monitoring using electrodes places a heavy burden on monitored individuals. Our non-contact respiratory monitoring system comprises a 1,215 MHz-microwave radar (LDR-1), antenna box attached to the ceiling, and personal computer with analyzing software. The system was tested on eight healthy volunteers (mean age, 25 years; range, 21–44 years) and eight elderly volunteers with some disorders (mean age, 69 years; range, 66–75 years). Respiratory rates of subjects measured using this system correlated with rates measured using respiration sensors (r = 0.97, P < 0.001 for healthy volunteers, r = 0.98, P < 0.0001 for elderly volunteers). The system could monitor subtle changes in respiratory rate, and monitoring respiratory rate increases caused by disorders such as pneumonia will be possible.