Biomedical Signals and Sensors II: Linking Acoustic and Optic Biosignals and Biomedical Sensors

233 Pages·2015·9.03 MB·English

by  Eugenijus Kaniusas (auth.)

Biological and Medical Physics, Biomedical Engineering
Eugenijus Kaniusas
Biomedical Signals
and Sensors II
Linking Acoustic and Optic Biosignals
and Biomedical Sensors
BIOLOGICAL AND MEDICAL PHYSICS,
BIOMEDICAL ENGINEERING
BIOLOGICAL AND MEDICAL PHYSICS,
BIOMEDICAL ENGINEERING
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More information about this series at http://www.springer.com/series/3740
Eugenijus Kaniusas
Biomedical Signals
and Sensors II
Linking Acoustic and Optic Biosignals
and Biomedical Sensors
With 73 Figures
123
Ao.Univ.-Prof.Dipl.-Ing.habil.Dr.EugenijusKaniusas
Headofresearchgroup‘BiomedicalSensors’
ViennaUniversityofTechnology
InstituteofElectrodynamics,MicrowaveandCircuitEngineering
Gusshausstr. 27–29
1040Vienna
Austria
E-mail: [email protected]
Volume1: ISBN978-3-642-24843-6
ISSN 1618-7210 ISSN 2197-5647 (electronic)
Biological and Medical Physics, BiomedicalEngineering
ISBN 978-3-662-45105-2 ISBN 978-3-662-45106-9 (eBook)
DOI 10.1007/978-3-662-45106-9
LibraryofCongressControlNumber:2012930477
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Preface
The present volume set develops a bridge between physiologic mechanisms and
diagnostichumanengineering.Amultitudeofbiomedicalsensorsarecommonplace
inclinicalpracticetoday.Theregisteredbiomedicalsignals,whichwillbereferred
to as biosignals, reflect vital physiologic phenomena and are relevant not only for
diagnosisbutalsofortherapy.Inordertoadequatelyapplybiomedicalsensorsand
reasonably interpret the corresponding biosignals, a proper and strategic under-
standing of the physiologic phenomena involved, their specific influence on the
registered biosignals, and the technology behind the sensors is critical.
While the first volume is focused on the interface between physiologic mecha-
nisms and the resultant biosignals, the second volume is devoted to the interface
between biosignals and biomedical sensors. That is, in the first volume, the phys-
iologic mechanisms determining biosignals are described from the basic cellular
level—as the place of origin of each and every biosignal—up to their advanced
mutual coordination level, e.g., during sleep. It allows a physiologically accurate
interpretation and comprehensive analysis of biosignals.
Consequently, this second volume considers the genesis of acoustic and optic
biosignals and the associated sensing technology from a strategic point of view.
Unlike other contributions, this book deals differently on the subject of specific
engineering aspects pertaining to particular biosignals, since it discusses hetero-
geneousbiosignalswithinacommonframe.Inparticular,thisframecomprisesboth
thebiosignalformationpathfromthebiosignalsourceatthephysiologicallevelto
biosignalpropagationinthebodyandthebiosignalsensingpathfromthebiosignal
transmission in the sensor applied on the body up to its conversion to a, usually
electric, signal.
Some biosignals arise in the course of the body’s vital functions while others
map these functions that convey physiological data to an observer. It is highly
instructive how sound and light beams interact with biological tissues, yielding
acousticandopticbiosignals,respectively.Discussedphenomenateachalotabout
the physics of sound and physics of light (as engineering sciences), and, on the
otherhand,biologyandphysiology(aslivesciences).Thisbookprovidesasortof
v
vi Preface
common denominator for acoustic and opticbiosignals, i.e., instructive similarities
and differences in between, whereas these biosignals—at first glance—are entirely
differentintheirphysicalnature.Basicandapplication-relatedissuesarecoveredin
depth;infact,theseissuesshouldremainstrongbecausethesestandthetestoftime
and mine knowledge of great value.
This book is directed primarily at graduate and post graduate students in bio-
medicalengineeringandbiophysics.Itisalsoaccessibletothosewhoareinterested
inphysical,engineering,andlifesciences,sinceexpectedbackgroundknowledgeis
minimal and many basic phenomena are explained in depth within numerous
footnotes.Furthermore,thebookshouldserveengineersandpractitionerswhohave
an interest in biomedical engineering. Discussed biosignals and sensing technolo-
gies substantiate wearable sensor technologies—the hot topic today—which com-
prise an appealing solution for pervasive (home) monitoring and prompt novel
approaches in diagnosis and therapy.
Itisimportanttonotethatthisbookwasmainlyinspiredbymylecturesentitled
“BiomedicalSensorsandSignals,”“BiomedicalInstrumentation,”and“Biophysics”
which constitute a significant part of a master’s degree program “Biomedical
Engineering” attheVienna University ofTechnologyin Austria.
In the end, it is not the spot-like knowledge of biosignals and engineering
technologiescomingfromindependentconsiderationsofbiosignalsthatconstitutea
successful biomedical engineer with profound professional knowledge, but the
strategic and global consideration of basically different biosignals and of the cor-
respondingsensingtechnologies,bothintegratedinthecommonframe.Thehighly
interdisciplinary nature of biosignals and biomedical sensors is obviously a chal-
lenge. However, it is a rewarding challenge after it has been coped with in a
strategicway,asofferedhere.Thebookisintendedtohavethepresencetoanswer
intriguing “Aha!” questions.
Vienna, Austria Eugenijus Kaniusas
Acknowledgments
I would like to express my sincerest thanks for support to Univ. Prof. Helmut
Pfützner (from the Institute of Electrodynamics, Microwave and Circuit Engi-
neering(EMCE),Vienna University ofTechnology,Austria), Univ.Prof. Giedrius
Varoneckas (from the Sleep Medicine Centre at Klaipeda University Hospital,
Lithuania), Univ. Prof. Bernd Saletu (from the Department of Psychiatry, Univer-
sity of Vienna, Austria), and Dr. Lars Mehnen, Dr. Karl Futschik, Dr. Stefan
Traxler (all from the EMCE).
I thank my students Dipl.-Ing. Stefan Kampusch, Florian Thürk, and Dejan
Tomic for experimental support and careful proof reading. The book has signifi-
cantlybenefitedfromcountlesssmallandlargeprojectsinwhichnumerousdiligent
students of mine have been involved. I give sincere thanks to all of them. Special
thanks go to Dipl.-Ing. Daniel Von-Chamier-Glisczinski who prepared ball pen
drawings prefacing each chapter and to Univ. Prof. Andrius Baltuska for scientific
advice. I express my deep gratitude to my family, parents, and other relatives for
unlimited support.
vii
Contents
4 Sensing by Acoustic Biosignals . . . . . . . . . . . . . . . . . . . . . . . . . . 1
4.1 Formation Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1.1 Body Sounds—An Overview. . . . . . . . . . . . . . . . . . 4
4.1.1.1 Heart Sounds. . . . . . . . . . . . . . . . . . . . . . . 4
4.1.1.2 Lung Sounds. . . . . . . . . . . . . . . . . . . . . . . 9
4.1.1.3 Snoring Sounds. . . . . . . . . . . . . . . . . . . . . 17
4.1.1.4 Apneic Sounds . . . . . . . . . . . . . . . . . . . . . 28
4.1.1.5 Mutual Interrelations . . . . . . . . . . . . . . . . . 29
4.1.2 Transmission of Body Sounds . . . . . . . . . . . . . . . . . 35
4.1.2.1 Propagation of Sounds . . . . . . . . . . . . . . . . 36
General Issues. . . . . . . . . . . . . . . . . . . . . . 36
Specific Issues. . . . . . . . . . . . . . . . . . . . . . 38
4.1.2.2 Effects on Sounds . . . . . . . . . . . . . . . . . . . 47
Volume Effects . . . . . . . . . . . . . . . . . . . . . 48
Inhomogeneity Effects . . . . . . . . . . . . . . . . 54
Scattering and Diffraction . . . . . . . . . . . . 54
Reflection. . . . . . . . . . . . . . . . . . . . . . . 56
Refraction. . . . . . . . . . . . . . . . . . . . . . . 58
Resonance. . . . . . . . . . . . . . . . . . . . . . . 59
4.2 Sensing Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.2.1 Coupling of Body Sounds . . . . . . . . . . . . . . . . . . . . 61
4.2.1.1 Chestpiece . . . . . . . . . . . . . . . . . . . . . . . . 62
Diaphragm . . . . . . . . . . . . . . . . . . . . . . . . 62
Bell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Diaphragm and Bell. . . . . . . . . . . . . . . . . . 69
Air Leaks . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.2.1.2 Microphone. . . . . . . . . . . . . . . . . . . . . . . . 72
4.2.1.3 Stethoscope. . . . . . . . . . . . . . . . . . . . . . . . 74
ix
x Contents
4.2.2 Registration of Body Sounds . . . . . . . . . . . . . . . . . . 76
4.2.2.1 Cardiac Activity. . . . . . . . . . . . . . . . . . . . . 77
4.2.2.2 Respiratory Activity. . . . . . . . . . . . . . . . . . 80
4.2.2.3 Spatial Distribution of Body Sounds. . . . . . . 83
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5 Sensing by Optic Biosignals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.1 Formation Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.1.1 Incident Light. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.1.1.1 Light Emission . . . . . . . . . . . . . . . . . . . . . 95
5.1.1.2 Light Source. . . . . . . . . . . . . . . . . . . . . . . 99
5.1.2 Transmission of Light. . . . . . . . . . . . . . . . . . . . . . . 101
5.1.2.1 Propagation of Light . . . . . . . . . . . . . . . . . 101
5.1.2.2 Effects on Light. . . . . . . . . . . . . . . . . . . . . 103
Volume Effects . . . . . . . . . . . . . . . . . . . . . 104
Inhomogeneity Effects . . . . . . . . . . . . . . . . 113
5.1.2.3 Light Modulation by Physiological
Phenomena. . . . . . . . . . . . . . . . . . . . . . . . 127
Cardiac Activity. . . . . . . . . . . . . . . . . . . . . 130
Respiratory Activity. . . . . . . . . . . . . . . . . . 133
Blood Oxygenation . . . . . . . . . . . . . . . . . . 139
General Issues. . . . . . . . . . . . . . . . . . . . 139
Specific Issues. . . . . . . . . . . . . . . . . . . . 144
Motion Artefacts . . . . . . . . . . . . . . . . . . . . 154
5.2 Sensing Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
5.2.1 Coupling of Light. . . . . . . . . . . . . . . . . . . . . . . . . . 160
5.2.1.1 Penetration and Probing of Light. . . . . . . . . 160
Penetration Depth. . . . . . . . . . . . . . . . . . . . 161
Probing Depth. . . . . . . . . . . . . . . . . . . . . . 161
5.2.1.2 Transmission and Reflection Modes. . . . . . . 165
General Issues. . . . . . . . . . . . . . . . . . . . . . 166
Source-Sink Distance . . . . . . . . . . . . . . . . . 170
Light Wavelength. . . . . . . . . . . . . . . . . . . . 171
Application Regions. . . . . . . . . . . . . . . . . . 173
Contacting Force and Skin Temperature . . . . 175
5.2.1.3 Light Sink. . . . . . . . . . . . . . . . . . . . . . . . . 180
5.2.1.4 Adverse Health Effects and Exposure
Limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Health Effects . . . . . . . . . . . . . . . . . . . . . . 182
Organs at Risk—Eye and Skin. . . . . . . . . . . 184
Remarks on Exposure Limits
and Optic Biosignals . . . . . . . . . . . . . . . . . 188