1 Skin Perfusion Studies: Historical Notes and Modern Measuring …
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1.11 Recent Developments and Additional Application
Fields of PPG Sensing Modalities
The analysis of heterogenous rhythmical phenomena in dermal perfusion requires
sophisticated assessment strategies [60–62]. It is possible to acquire undistorted
vital signals across a broad frequency range using modular multi-sensor concepts
and the correlations between the sensors. These sophisticated assessment strategies reveal—alongside known central rhythms—local oscillations around 0.1 Hz,
showing endogenous influence ability. Local changes in perfusion patterns can
further be assessed by novel optical remote sensing techniques like photoplethysmography imaging (short PPGI; this acronym is a registered trademark since 1997)
in a completely contactless manner, while simultaneously providing results with
high spatial resolution. Advanced joint-time-frequency signal processing allows the
observation and visualization of local slow perfusion rhythms in healthy and/or adjacent skin regions. Signals across a wide frequency range can be examined, including
a good resolution at low frequencies. At the same time, the temporal evolution of
different frequency components in the skin perfusion dynamics over time can also
be revealed (see Chaps. 11 and 12).
Some of the current hardware and software developments should be mentioned
in the following short review, which will open up new and possibly can revolutionize today´s application fields of the photoplethysmography in functional vascular
diagnostics and smart home care.
1.11.1 Distributed Micro Sensor Solutions
Multi-body side PPG sensor solutions have been proposed for peripheral vascular
disease detection. Comparing arterial pulse recordings simultaneously taken at the
right and left ear lobes, index fingers, and great toe sides, the considerable similarity
in bilateral body paths under physiological conditions were demonstrated in [63].
This study also described that cross-correlation analysis quantified the degree of similarity in normal subjects compared to dissimilarity in a patient with unilateral arterial
diseases. A fascinating platform, integrating a collection of independent sensor types
(such as electro-optical, temperature and strain gauge), wireless powering components and components for RF communications, all integrated on a thin and flexible
sheet was published in [64]. Such distributed microsensor solutions also can be
used for assessment and minimization of motion artefacts in PPG recordings or as a
human/machine interface in common body alarm devices.
23
1.11 Recent Developments and Additional Application
Fields of PPG Sensing Modalities
The analysis of heterogenous rhythmical phenomena in dermal perfusion requires
sophisticated assessment strategies [60–62]. It is possible to acquire undistorted
vital signals across a broad frequency range using modular multi-sensor concepts
and the correlations between the sensors. These sophisticated assessment strategies reveal—alongside known central rhythms—local oscillations around 0.1 Hz,
showing endogenous influence ability. Local changes in perfusion patterns can
further be assessed by novel optical remote sensing techniques like photoplethysmography imaging (short PPGI; this acronym is a registered trademark since 1997)
in a completely contactless manner, while simultaneously providing results with
high spatial resolution. Advanced joint-time-frequency signal processing allows the
observation and visualization of local slow perfusion rhythms in healthy and/or adjacent skin regions. Signals across a wide frequency range can be examined, including
a good resolution at low frequencies. At the same time, the temporal evolution of
different frequency components in the skin perfusion dynamics over time can also
be revealed (see Chaps. 11 and 12).
Some of the current hardware and software developments should be mentioned
in the following short review, which will open up new and possibly can revolutionize today´s application fields of the photoplethysmography in functional vascular
diagnostics and smart home care.
1.11.1 Distributed Micro Sensor Solutions
Multi-body side PPG sensor solutions have been proposed for peripheral vascular
disease detection. Comparing arterial pulse recordings simultaneously taken at the
right and left ear lobes, index fingers, and great toe sides, the considerable similarity
in bilateral body paths under physiological conditions were demonstrated in [63].
This study also described that cross-correlation analysis quantified the degree of similarity in normal subjects compared to dissimilarity in a patient with unilateral arterial
diseases. A fascinating platform, integrating a collection of independent sensor types
(such as electro-optical, temperature and strain gauge), wireless powering components and components for RF communications, all integrated on a thin and flexible
sheet was published in [64]. Such distributed microsensor solutions also can be
used for assessment and minimization of motion artefacts in PPG recordings or as a
human/machine interface in common body alarm devices.