Cardiorespiratory Parameters Monitoring Through a Single Digital Camera in Real Scenarios: ROI Tracking and Motion Influence

Monitoring of heart rate (HR) and respiratory rate (fR) is fundamental to assessing the health status of an individual. To address this scope, technologies that frame the upper body and the face regions of a subject without any physical contact can be used. Motion artifacts can affect the applicability of non-contact methods to the continuous monitoring of these parameters as well as the computational burden. This article focuses on a technique based on images captured with a single digital camera for the continuous estimation of HR and fR. The main goal is to analyze how the velocity of facial movements and region of interest (ROI) tracking duration influence the performance of the method. Tests were performed on healthy volunteers during motionless trials (i.e., at rest and after exercise), head and torso movements, and during physical exercise. Results demonstrated that a continuous estimation of HR and fR can be performed with acceptable errors under changing ROI tracking duration and velocity in motionless trials (mean absolute error (MAE) below 5 bpm and 3.42 breaths · min-1 for HR and fR, respectively), whereas during movements (mimicking head and torso movements, and during exercise) the error increases (MAE up to 5.42 bpm and up to 5.03 breaths · min-1 for HR and fR , respectively). The proposed investigation can provide a framework for the continuous estimation of HR and fR during both static and dynamic activities by optimizing the ROI tracking duration under different velocities of facial movements.