Simultaneous Measurement of Heartbeat Intervals and Respiratory Signal using a Smartphone

This paper explores the use of a common smartphone for measuring simultaneously both heartbeat intervals and respiratory cycles. The proposed technique uses the smartphone’s accelerometer to measure the seismocardiographic signal and the acceleration due to breathing movements. The measurement is carried out while the subject is laying down, with the smartphone placed on his/her xiphoid process. In the paper, processing algorithms are presented, that can be used to obtain the heartbeat and the respiratory intervals from the measured signals. As concrete examples of possible application, heartbeat intervals are used to derive Heart Rate Variability and, together with the respiratory signal, to derive a Respiratory Sinus Arrhythmia measure on eight healthy volunteers.