Chapter 1
Skin Perfusion Studies: Historical Notes
and Modern Measuring Strategies Using
Non-invasive Photoplethysmographic
Sensor Concepts
Vladimir Blazek
Abstract For adequate skin perfusion rhythmicity assessment, sensor technology
must be used, which fulfills basic demands such as unobtrusiveness and continuous monitoring with spatial resolution photoplethysmography (PPG) and its modern
camera-based imaging variant (PPGI) ideally meet these requirements, and they are
generally accepted in the field of noninvasive medical diagnostics. PPG can work
in reflective or transmissive mode and detects blood volume changes in the vascular
plexus within the region of transilluminated tissue. The PPG and PPGI signals
comprise a complex of pulsatile wave formations (AC) associated with cardiac,
respiratory, and different nervous system activities, which are superimposed to a
non-pulsatile baseline (DC) due to optical damping of bloodless tissue. Although
most of the PPG applications in medical diagnostics are today devoted to recording
cardiac rhythmicity, the strength and future of PPG lie in detecting the distributed
and, in some cases, highly autonomous skin perfusion dynamics below the frequencies of the “central oscillators”, namely the heartbeat and breathing. This chapter
presents selected activities and results of the bilateral and interdisciplinary longterm cooperation between IIT Madras in Chennai and RWTH Aachen University in
Aachen in this exciting research field of the dermal perfusion dynamics.
1.1 Introduction
The Englishman William Harvey (1578–1657) was the first physician to correctly
describe the dynamics of blood circulation after many false interpretations and
working hypotheses presented by others. Nevertheless, he considerably underestimated the pumping function of the heart. He assumed that half an ounce (18 g) of
blood is normally pumped per minute by the left ventricle; he then multiplied this
amount by 1000 heartbeats per half an hour and concluded that 1000 oz of blood has
V. Blazek (B)
Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH
Aachen University, Aachen, Germany
e-mail: blazek@hia.rwth-aachen.de
© Springer Nature Singapore Pte Ltd. 2021
V. Blazek et al. (eds.), Studies in Skin Perfusion Dynamics,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-981-15-5449-0_1
1
Skin Perfusion Studies: Historical Notes
and Modern Measuring Strategies Using
Non-invasive Photoplethysmographic
Sensor Concepts
Vladimir Blazek
Abstract For adequate skin perfusion rhythmicity assessment, sensor technology
must be used, which fulfills basic demands such as unobtrusiveness and continuous monitoring with spatial resolution photoplethysmography (PPG) and its modern
camera-based imaging variant (PPGI) ideally meet these requirements, and they are
generally accepted in the field of noninvasive medical diagnostics. PPG can work
in reflective or transmissive mode and detects blood volume changes in the vascular
plexus within the region of transilluminated tissue. The PPG and PPGI signals
comprise a complex of pulsatile wave formations (AC) associated with cardiac,
respiratory, and different nervous system activities, which are superimposed to a
non-pulsatile baseline (DC) due to optical damping of bloodless tissue. Although
most of the PPG applications in medical diagnostics are today devoted to recording
cardiac rhythmicity, the strength and future of PPG lie in detecting the distributed
and, in some cases, highly autonomous skin perfusion dynamics below the frequencies of the “central oscillators”, namely the heartbeat and breathing. This chapter
presents selected activities and results of the bilateral and interdisciplinary longterm cooperation between IIT Madras in Chennai and RWTH Aachen University in
Aachen in this exciting research field of the dermal perfusion dynamics.
1.1 Introduction
The Englishman William Harvey (1578–1657) was the first physician to correctly
describe the dynamics of blood circulation after many false interpretations and
working hypotheses presented by others. Nevertheless, he considerably underestimated the pumping function of the heart. He assumed that half an ounce (18 g) of
blood is normally pumped per minute by the left ventricle; he then multiplied this
amount by 1000 heartbeats per half an hour and concluded that 1000 oz of blood has
V. Blazek (B)
Medical Information Technology, Helmholtz Institute for Biomedical Engineering, RWTH
Aachen University, Aachen, Germany
e-mail: blazek@hia.rwth-aachen.de
© Springer Nature Singapore Pte Ltd. 2021
V. Blazek et al. (eds.), Studies in Skin Perfusion Dynamics,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-981-15-5449-0_1
1