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Active and Passive Optical Imaging Modality for Unobtrusive Cardiorespiratory Monitoring and Facial Expression Assessment

Blazek, Vladimir Dr.-Ing. Dr. h.c.; Blanik, Nikolai Dipl.-Ing.; Blazek, Claudia R. MD; Paul, Michael MSc; Pereira, Carina MSc; Koeny, Marcus Dr.-Ing.; Venema, Boudewijn Dr.-Ing.; Leonhardt, Steffen Dr.-Ing., MD

doi: 10.1213/ANE.0000000000001388
Technology, Computing, and Simulation: Narrative Review Article

Because of their obvious advantages, active and passive optoelectronic sensor concepts are being investigated by biomedical research groups worldwide, particularly their camera-based variants. Such methods work noninvasively and contactless, and they provide spatially resolved parameter detection. We present 2 techniques: the active photoplethysmography imaging (PPGI) method for detecting dermal blood perfusion dynamics and the passive infrared thermography imaging (IRTI) method for detecting skin temperature distribution. PPGI is an enhancement of classical pulse oximetry. Approved algorithms from pulse oximetry for the detection of heart rate, heart rate variability, blood pressure-dependent pulse wave velocity, pulse waveform-related stress/pain indicators, respiration rate, respiratory variability, and vasomotional activity can easily be adapted to PPGI. Although the IRTI method primarily records temperature distribution of the observed object, information on respiration rate and respiratory variability can also be derived by analyzing temperature change over time, for example, in the nasal region, or through respiratory movement. Combined with current research areas and novel biomedical engineering applications (eg, telemedicine, tele-emergency, and telemedical diagnostics), PPGI and IRTI may offer new data for diagnostic purposes, including assessment of peripheral arterial and venous oxygen saturation (as well as their differences). Moreover, facial expressions and stress and/or pain-related variables can be derived, for example, during anesthesia, in the recovery room/intensive care unit and during daily activities. The main advantages of both monitoring methods are unobtrusive data acquisition and the possibility to assess vital variables for different body regions. These methods supplement each other to enable long-term monitoring of physiological effects and of effects with special local characteristics. They also offer diagnostic advantages for intensive care patients and for high-risk patients in a homecare/outdoor setting. Selected applications have been validated at our laboratory using optical PPGI and IRTI techniques in a stand-alone or hybrid configuration. Additional research and validation is required before these preliminary results can be introduced for clinical applications.

Published ahead of print August 17, 2016.

From the *Philips Chair for Medical Information Technology, Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany; The Czech Institute of Informatics, Robotics and Cybernetics, CTU Prague, Prague, Czech Republic; and The Private Clinic of Dermatology, Haut im Zentrum, Zurich, Switzerland.

Published ahead of print August 17, 2016.

Accepted for publication March 31, 2016.

Funding: Carina Pereira is founded by the Foundation for Science and Technology (FCT) in Portugal (PhD grant SFRH/BD/84357/2012).

Conflict of Interest: See Disclosures at the end of the article.

Reprints will not be available from the authors.

Address correspondence to Vladimir Blazek, Pauwelsstr. 20, 52074 Aachen, Germany. Address e-mail to

© 2017 International Anesthesia Research Society