Novel Methods for Noncontact Heart Rate Measurement: A Feasibility Study

The following paper investigates four novel methods for noncontact measurement of heart rate (HR) and consequently its derivate HR variability, an important marker of autonomic activity proven to be predictive of likelihood of future health related events. Feasibility study of basic principles is focused on measurements of signal-to-noise ratio with respect to the distance between the subject and HR sensor/apparatus. The discussed methods are divided into the following two groups: the methods measuring electromagnetic energy generated by the bioelectrical activity within the cardiac muscle (referred to as direct methods), and the methods measuring displacement of a part of the subject's body caused by the periodic physical contractions of the heart (referred to as indirect methods). The first group is represented by a measuring device which detects changes in surrounding electric field, whereas the second group consists of measuring devices that use the Doppler effect phenomena (microwave radar, ultrasound radar) and audio signal acquired by a condenser microphone. All measuring devices were assembled and put to test. The results indicate that noncontact measuring of HR is possible, especially for distances of less than 50 cm meeting essential requirements for HR diagnostic purposes.