System for simultaneous measurement of breathing rate and heart rate using photoplethysmogram

Wearable vital sensors for monitoring parameters such as breathing rate and heart rate are important for the daily care of patients and solitary people in home healthcare applications. At present, there are many types of heart rate measurement sensors, including those that are attached to the fingertips, chest, and wrist. However, these types of sensors are unsuitable for home healthcare use because they are too bothersome for daily use. These sensors use a photoplethysmogram to measure the heart rate. Although a breathing signal is also superimposed on the heart rate, the problem is that this signal is very weak and unstable. In the work described in this paper, we developed a reliable breathing rate and heart rate measurement sensor. The sensor is attached on the wrist, like a wristwatch. Such wrist-worn sensors already exist, but they are unreliable due to their generally low sensitivity. In contrast, our newly developed sensor employs an array of multiple photo-interrupters and selects the most reliable photo-interrupter by employing a unique algorithm. In addition, the sensor data is sent to a data logger wirelessly in order to achieve stress-free daily health care monitoring.