Fuzzy Logic Hemoglobin Sensors Zur Erlangung des akademischen Grades eines DOKTOR-INGENIEURS von M. Sc. Eng. Kawther Abo Alam Fuzzy Logic Hemoglobin Sensors Zur Erlangung des akademischen Grades eines DOKTOR-INGENIEURS von der Fakultät für Elektrotechnik und Informationstechnik des Karlsruher Instituts für Technologie (KIT) vorgelegte DISSERTATION von M. Sc. Eng. Kawther Abo Alam Geb. in: El-Minoufia, Ägypten. Tag der mündlichen Prüfung: 10.05.2011 Hauptreferent: Prof. Dr. rer. nat. Armin Bolz Korreferent: Prof. Dr. rer. nat. Josef Guttmann INSTITUT FÜR BIOMEDIZINISCHE TECHNIK KARLSRUHER INSTITUT FÜR TECHNOLOGIE (KIT) n 1 List of Contents: Introduction ............................................................................................................... 14 1.1 Motivation ..................................................................................................................... 14 1.2 Research objectives ........................................................................................................ 16 1.2.1 Non-invasive measuring ................................................................................... 16 1.2.2 Invasive measuring .......................................................................................... 16 1.3 Thesis outline ................................................................................................................. 17 Part I: Background and Current State of the Art .................................................... 18 Physiological Foundations ......................................................................................... 20 2.1 Preliminaries .................................................................................................................. 20 2.2 Blood composition and functions ................................................................................... 20 2.2.1 Blood composition ........................................................................................... 20 2.2.2 Blood functions ................................................................................................ 21 2.3 Hemoglobin ................................................................................................................... 22 2.3.1 Hemoglobin function ....................................................................................... 23 2.3.2 Hemoglobin structure ....................................................................................... 24 2.3.3 Hemoglobinopathy ........................................................................................... 25 2.3.4 Hemoglobin test ............................................................................................... 26 Pulse Oximetry .......................................................................................................... 28 3.1 Preliminaries .................................................................................................................. 28 3.2 Photoplethysmography ................................................................................................... 29 3.2.1 The photoplethysmography waveform .............................................................. 31 3.3 Light absorbance basics .................................................................................................. 32 3.4 Light absorbance in pulse oximetry and estimation of oxygen saturation......................... 34 3.4.1 Light absorbance in pulse oximetry .................................................................. 34 3.4.2 Estimation of functional arterial oxygen saturation ........................................... 36 3.5 Pulse oximetry limitations .............................................................................................. 40 3.5.1 Physiological limitations .................................................................................. 40 3.5.2 Interference from substances ............................................................................ 41 3.5.3 Limitation in the signal processing ................................................................... 43 3.5.4 Physical factors ................................................................................................ 45 LIST OF CONTENTS 3.6 Current state of the art .................................................................................................... 46 3.6.1 The previous work towards the non-invasive determination of the fractional oxygen saturation and the total hemoglobin concentration .............................................. 46 3.6.2 Artificial intelligent applications for PPG signal ............................................... 47 3.6.3 Non-invasive tHb concentration devices in the market ...................................... 50 Part II: Methodology ................................................................................................. 52 Optoelectronic System Set-Up for Non-Invasive Measuring ................................... 54 4.1 Preliminaries .................................................................................................................. 54 4.2 PPG signals extraction.................................................................................................... 54 4.2.1 Transimpedance amplifier circuit ..................................................................... 56 4.2.2 LEDs drive circuit and control.......................................................................... 58 4.3 Proposed low perfusion signal processing module .......................................................... 60 4.3.1 Functional block diagram of the proposed signal processing module................. 61 4.3.2 The proposed signal processing module evaluation ........................................... 65 4.4 Flow chart of the software processing outline ................................................................. 67 4.5 Overview of the optoelectronic system output ................................................................ 68 Proposed Estimation Approaches for Non-Invasive Measuring .............................. 70 5.1 Preliminaries .................................................................................................................. 70 5.2 PPGs main distinctive features extracting ....................................................................... 70 5.3 Proposed algorithm based on modified Lambert-Beer law .............................................. 74 5.3.1 Modified Lambert-Beer law ............................................................................. 74 5.3.2 Modified Lambert-Beer law revisited for PPG signals ...................................... 75 5.3.3 Extinction coefficients of the four hemoglobin components .............................. 79 5.3.4 Proposed indication for Δd applying ................................................................. 80 5.3.5 Recommended strategy of estimation based on modified Lambert-Beer law ..... 82 5.4 Proposed algorithm based on fuzzy logic systems ........................................................... 87 5.4.1 Introduction to fuzzy logic ............................................................................... 87 5.4.3.1 Architecture of fuzzy logic systems .......................................................... 87 5.4.2 Reasons behind using fuzzy logic system ......................................................... 89 5.4.3 Building the fuzzy logic expert system ............................................................. 90 5.4.3.1 Defining the crisp inputs and outputs of the fuzzy system ......................... 90 5.4.3.2 Employing the fuzzy inference scheme ..................................................... 91 5.4.3.3 Fuzzy rule base generation........................................................................ 93 5.4.3.4 Data flow of the proposed fuzzy expert system ......................................... 94 Proposed Estimation Algorithm for Invasive Measuring ........................................ 96 6.1 Preliminaries .................................................................................................................. 96 6.2 Building the fuzzy expert system .................................................................................... 96 5 LIST OF CONTENTS i 6.2.1 Defining the crisp inputs and outputs of the fuzzy expert system ...................... 96 6.2.2 Employing the fuzzy inference scheme ............................................................. 98 6.2.3 Fuzzy rule base generation ............................................................................... 98 6.3 The whole fuzzy expert system....................................................................................... 98 Part III: Results and Conclusions ........................................................................... 100 Results and Discussion............................................................................................. 102 7.1 Preliminaries ................................................................................................................ 102 7.2 Results: non-invasive measuring .................................................................................. 102 7.2.1 Results of the method that is based on modified Lambert-Beer law ................. 104 7.2.2 Results of fuzzy expert system algorithm........................................................ 111 7.3 Results: invasive measuring ........................................................................................