This book talks about photoplethysmography (PPG) techniques based on computer-aided data processing. In particular, it presents the results of a co-operative Indo-German project on the topic between Indian Institute of Technology at Chennai and RWTH Aachen University. Measuring system design, experimental details and some preliminary results obtained so far within the framework of this project are presented here. From the investigations carried out so far using the PPG sensors in conjunction with breathing sensors, it has been possible to monitor the 0.125 to 0.15 Hz rhythms in the arterial volumetric changes and to study the influence of breathing on them. These rhythms, which according to medical experts have relevance to psychosomatic conditions e.g. stress or relaxation, can also be addressed to by ancient Indian practices like yoga and meditation. This book presents the results of studying the effects of Indian relaxation techniques like pranayama, meditation, etc. in comparison to western relaxation techniques like autogenic training. So far it has been established that the Indian techniques of relaxation like yoga and meditation are very effective in generating low frequency rhythms in the skin perfusion as monitored by optical sensors. According to medical experts, these low frequency rhythms have a very important bearing on the human physiology and have potential therapeutic implications. This book is meant to provide an overview of the current state-of-knowledge and encourage the next generation of scientists/engineers to carry this work forward, especially on the novel PPG application fields that are of growing importance like pain and stress assessment, detection of peripheral venous saturation and local arterio-venous oxygen consumption as well as contactless space resolved skin perfusion studies with modern camera based PPG technology.
