title: A new look at the essence of the imaging photoplethysmography.
abstract: Photoplethysmography (PPG) is a noninvasive optical method accepted in the clinical use for measurements of arterial oxygen saturation. It is widely believed that the light intensity after interaction with the biological tissue in vivo is modulated at the heartbeat frequency mainly due to pulsatile variations of the light absorption caused by arterial blood-volume pulsations. Here we report experimental observations, which are not consistent with this model and demonstrate the importance of elastic deformations of the capillary bed in the formation of the PPG waveform. These results provide new insight on light interaction with live tissue. To explain the observations we propose a new model of PPG in which pulse oscillations of the arterial transmural pressure deform the connective-tissue components of the dermis resulting in periodical changes of both the light scattering and absorption. These local changes of the light-interaction parameters are detected as variations of the light intensity returned to a photosensitive camera. Therefore, arterial pulsations can be indirectly monitored even by using the light, which slightly penetrates into the biological tissue.
authors.affiliation: 1] Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland [2] Scientific-Technical Centre for Computational Optics, Photonics and Imaging, ITMO University, 197101 St. Petersburg, Russia.
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Kamshilin
authors.affiliation: Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, FI-70211, Kuopio, Finland.
authors.forename: Ervin
authors.initials: E
authors.lastname: Nippolainen
authors.affiliation: Delfin Technologies Ltd., FI- 70210 Kuopio, Finland.
authors.forename: Igor S
authors.initials: IS
authors.lastname: Sidorov
authors.affiliation: Faculty of Medicine, St. Petersburg State University, 199034 St. Petersburg, Russia.
authors.forename: Petr V
authors.initials: PV
authors.lastname: Vasilev
authors.affiliation: Faculty of Medicine, St. Petersburg State University, 199034 St. Petersburg, Russia.
authors.forename: Nikolai P
authors.initials: NP
authors.lastname: Erofeev
authors.affiliation: 1] School of Natural Sciences, Far-Eastern Federal University, 690950 Vladivostok, Russia [2] Lab. of Precision Optical Measurement Techniques, Institute of Automation and Control Processes FEB RAS, 690041 Vladivostok, Russia.
authors.forename: Natalia P
authors.initials: NP
authors.lastname: Podolian
authors.affiliation: 1] School of Natural Sciences, Far-Eastern Federal University, 690950 Vladivostok, Russia [2] Lab. of Precision Optical Measurement Techniques, Institute of Automation and Control Processes FEB RAS, 690041 Vladivostok, Russia.
authors.forename: Roman V
authors.initials: RV
authors.lastname: Romashko
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D005260:Female; D006225:Hand / Q000098:blood supply*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D017156:Photoplethysmography; D063177:Pulse Wave Analysis; D012039:Regional Blood Flow / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D014741:Video Recording
chemical_list: D010100:Oxygen