Passive RFID Tag for Respiratory Frequency Monitoring

Continuous monitoring of vital signals provides relevant information about a patient health status, which is essential in situations of risk. There is a need for practical and efficient systems to obtain these parameters and the RFID technology is presented here as a solution. In this work, a passive RFID tag is developed for respiratory rate monitoring. The RFID tag is a wireless solution for the subject and provides comfort due to its flexibility. Simulations and measurements were performed. To carry out the simulations, it was necessary to characterize the dielectric materials. The principle of operation of the technology in this application is based on the variations of the Received Signal Strength Indicator (RSSI) caused by the respiratory movements. As a result of the measurements performed with the tag placed on the abdomen of a person, during which forced inhalations and slow expirations were made, these variations of the RSSI could be noticed and, based on the respiratory cycles detected, it was possible to estimate the respiratory rate.