Contactless systems for physiological parameters monitoring and biomedical applications

The measurement of physiological parameters is paramount to assessing and monitoring a person’s health status, diagnose medical conditions at an early stage, enabling timely treatment, and preventing or reducing complications in hospitalized patients. Various technologies and measurement tools allow for estimating these parameters and involve direct contact of the sensing element with the subject’s body. The contactless monitoring of vital signs may provide benefits in various fields of application, from healthcare and clinical settings to occupational and sports scenarios, due to its ease of use and completely non-intrusiveness. Recent research has been focused on the potentiality of camera-based systems working in the visible range (380–750 nm) for estimating vital signs by capturing subtle color changes or motions caused by physiological activities but invisible to human eyes. These quantities are typically extracted from videos framing some exposed body areas (e.g., face, torso, and hands) with adequate post-processing algorithms. In this thesis, research related to the innovative use of digital cameras in the field of visible light and the development of algorithms to continuously and without contact estimate heart rate, frequency rate, and SpO2 and other parameters of physiological interest (e.g., thoraco-abdominal asynchrony) from a video of the subject’s face and torso was carried out. Several experimental tests were performed on healthy subjects and patients in different application scenarios (e.g., clinical, occupational, sports) to evaluate the performance of the systems under different environmental conditions and in the presence of subject movement. Firstly, in Chapter 2 and Chapter 3, the assessment of respiratory and cardiac parameters was described, evaluating the performance of different digital cameras under the influence of some external factors (e.g., user-camera distance, ambient light condition, regions of interest selection). Tests were performed in different scenarios (from occupational to clinical settings). Next, in Chapter 4, an analysis of using RGB digital cameras in the simultaneous and continuous estimation of SpO2 and heart rate was carried out. Chapter 5 explores the use of digital cameras in monitoring cardiorespiratory parameters (heart rate and frequency rate) continuously in static and dynamic conditions (e.g., sports science). In summary, this thesis explores the use of digital cameras to monitor physiological parameters in different scenarios continuously. Further research is needed to promote the advancements of the technology, allowing its application in a wide range of populations and everyday life.