Customized in-ear PPG sensor

The advent of consumer market wearable devices like watches or rings that incorporate photoplethysmography (PPG) sensors has ignited a revolution in general medicine, with a particular emphasis on sports medicine. PPG devices generally obtain heart rate frequency accurately; however, they are unable to retrieve a clean arterial waveform due to motion and other types of noise sources. As a result, their clinical potential is strongly limited. One approach to mitigate motion artifacts is to maintain the PPG sensor as fixed as possible in a given location. It is for these reasons that we are building, for the first time, a wireless PPG sensor inserted in the ear canal while being embedded inside a custom earmold. This earmold precisely fits a subject’s ear, ensuring that the sensor moves minimally while in operation. The location chosen for placing the sensor is the ear canal as the technology for creating custom earmolds that tightly fit a person is well established, moreover, the ear canal presents an abundant number of arteries that help enhance the signal captured from the PPG. In this manuscript we compare the output from a commercially available electrocardiogram (ECG) device to that of our own PPG sensor to validate the data captured. Furthermore, a comparison with a commercial PPG device is also made. We believe that the data presented here demonstrates that the sensor is functional and has significant potential for applications requiring reliable heart rate waveform acquisition, even during activities involving body motion.