Design of pulse oximeters

Design of Pulse Oximeters......Page 1
CONTENTS......Page 5
PREFACE......Page 13
1.1.1 Neural control......Page 15
1.2 VENTILATORY MECHANICS......Page 16
1.2.1 Inspiration......Page 17
1.2.2 Expiration......Page 18
1.3.2 Gas exchange......Page 19
1.4.1 Characteristics of hemoglobin......Page 20
1.4.2 Oxyhemoglobin dissociation curves......Page 21
1.6.1 The heart......Page 22
1.6.4 Cardiac output......Page 23
1.7 DIFFUSION TO TISSUE......Page 24
1.8 USE IN CELL......Page 25
INSTRUCTIONAL OBJECTIVES......Page 26
2.1 PULSE OXIMETER PRINCIPLES......Page 27
2.2 Sp02 AS MONITOR OF HEMOGLOBIN OXYGENATION......Page 28
2.2.3 Hypoxia and hypoxemia......Page 29
2.2.4.1 Anesthesiology.......Page 30
2.2.5 Photoplethysmography......Page 32
2.3.2 Limitations in Sa02......Page 33
INSTRUCTIONAL OBJECTIVES......Page 34
3.1 CHEMICAL METHODS......Page 35
3.1.1 Van Slyke method......Page 36
3.1.3 The Clark electrode......Page 37
3.2 TRANSCUTANEOUS PO2 SENSOR......Page 39
3.3.1 Spectrophotometers......Page 40
3.3.2 The CO-oximeter......Page 42
3.5.1 In vitro reflectance oximeter......Page 44
3.5.2 In vivo reflectance catheter oximeter......Page 45
3.6 IN VIVO EIGHT-WAVELENGTH OXIMETER......Page 46
3.7.1 Overview......Page 48
3.7.2 LEDs......Page 49
3.7.4 Probes......Page 50
3.7.6 A three-wavelength pulse oximeter for COHb determination......Page 51
REFERENCES......Page 52
INSTRUCTIONAL OBJECTIVES......Page 53
4.1 BEER’S LAW......Page 54
4.1.2 Multiple absorbers......Page 55
4.2.2.1 Methemoglobin.......Page 56
4.2.2.4 Fractional hemoglobin saturation.......Page 57
4.3 BEER'S LAW IN PULSE OXIMETRY......Page 58
4.3.2 Absorbance in hemoglobin solutions......Page 59
4.3.3 Pulsation of the blood......Page 60
4.3.4 Measurement of pulse oximeters......Page 62
4.4.2 Ratio of normalized signals......Page 63
4.4.3 Theoretic calibration curve......Page 64
4.5 VALIDITY OF BEER’S LAW IN PULSE OXIMETRY......Page 65
4.6.2 Models for light absorbance including scattering......Page 66
4.6.3 Influence of scattering on pulse oximeter readings......Page 67
REFERENCES......Page 68
INSTRUCTIONAL OBJECTIVES......Page 69
5.1 AN INTRODUCTION TO LIGHT-EMITTING DIODES......Page 70
5.2 LIGHT-EMITTING DIODE SPECIFICATIONS......Page 71
5.2.2 Forward current......Page 72
5.2.3 Power dissipation......Page 73
5.2.6 Operating temperature......Page 74
5.2.9 Pulse capability......Page 75
5.3 MEASURING AND IDENTIFYING LED WAVELENGTHS......Page 76
5.4 LED DRIVER CIRCUIT......Page 78
5.5.2 Studies......Page 80
5.5.3 Two methods to compensate for LED temperature changes......Page 82
5.7 LED PACKAGING......Page 83
INSTRUCTIONAL OBJECTIVES......Page 84
6.1.1 Photocells......Page 85
6.1.2 Photodiodes......Page 86
6.1.2.4 Avalanche photodetectors (APDs).......Page 89
6.2.1 Junction capacitance......Page 90
6.2.5.3 Resin mold package.......Page 91
6.4 AMPLIFIERS......Page 93
6.4.1 Standard transimpedance amplifier configuration......Page 94
6.4.1.5 Feedback capacitor.......Page 95
6.4.2 Differential transimpedance amplifier......Page 96
6.4.3 Zeroing circuit......Page 97
REFERENCES......Page 98
INSTRUCTIONAL OBJECTIVES......Page 99
7.1.1 Principle......Page 100
7.2 REFLECTANCE PROBES......Page 101
7.2.2.1 Optimum distance between LEDs and photodiode.......Page 102
7.2.4 Effect of skin temperature......Page 104
7.3 MRI PROBES......Page 105
7.4 PROBE CONNECTORS......Page 106
7.5 REUSABLE PROBES......Page 107
7.7.1 Ambient light interference......Page 108
7.7.4 Nail polish......Page 109
INSTRUCTIONAL OBJECTIVES......Page 110
8.1 GENERAL THEORY OF OPERATION......Page 111
8.1.1 Historic perspective......Page 112
8.2 MAIN BLOCK DIAGRAM......Page 113
8.2.1 Input module......Page 114
8.3.1.1 Memory and memory mapping.......Page 115
8.3.2 General block description......Page 116
8.3.4 Clock generator, timer circuit and UART......Page 117
8.3.5 Pattem generator......Page 118
8.4.3 Preamplifier......Page 119
8.4.4 Demodulator and filtering......Page 120
8.4.5 DC offset elimination......Page 121
8.4.6 Timing diagram (NellcorB)......Page 123
8.4.7 LED driver circuit......Page 124
8.4.8.1 LED drive and monitor.......Page 125
8.4.8.8 Sample and hold circuits.......Page 126
8.5 ECG SECTION......Page 127
8.5.3 Detached lead indicator......Page 128
8.5.5 ECG output......Page 129
8.6.1 Analog-to-digital conversion technique......Page 130
8.7.1 Polling and interrupt......Page 131
8.8 POWER SUPPLY......Page 132
8.10 STORAGE......Page 133
8.11.1 Front end driver circuit......Page 134
8.12 SPEAKERS......Page 135
INSTRUCTIONAL OBJECTIVES......Page 136
9.1 SOURCES OF ERRORS......Page 138
9.2 BEER-LAMBERT LAW......Page 139
9.2.1.1 Eliminating the input light intensity as a variable.......Page 140
9.2.1.2 Eliminating the thickness of the path as a variable.......Page 141
9.3.1 Peak and valley method......Page 143
9.3.2 Derivative method: noise reduction software......Page 144
9.4 GENERAL PROCESSING STEPS OF OXIMETRY SIGNALS......Page 147
9.4.1 Start up software.......Page 148
9.5 TRANSIENT CONDITIONS......Page 149
9.6 ECG SYNCHRONIZATION ALGORITHMS......Page 157
9.6.1 Nellcora system......Page 158
9.6.1.2 The systems routine.......Page 160
9.6.1.3 LEVEL 3 software.......Page 161
9.6.2 Criticare@ systems......Page 163
9.6.2.2 Peak discrimination algorithm.......Page 165
9.6.2.3 Ensemble averaging algorithm.......Page 166
9.6.2.4 Motion determination algorithm.......Page 168
9.6.2.5 Pulsatile waveform weight determination algorithm.......Page 169
9.7 SPECTRAL METHODS OF ESTIMATING SpOz......Page 171
INSTRUCTIONAL OBJECTIVES......Page 172
10.1.1.1 Procedure.......Page 173
10.1.1.2 Problems.......Page 174
10.1.1.4 Field calibration.......Page 175
10.1.2 In vitro calibration using blood......Page 176
10.2 TESTING SIMULATORS......Page 177
10.2.1.4 Dual wedge system.......Page 178
10.2.1.5 Bulb device.......Page 180
10.2.2.4 Colored colloid simulator.......Page 182
10.2.2.7 Optoelectronic device.......Page 184
10.2.3 Electronic simulators......Page 185
10.3 STANDARDS......Page 186
10.3.2 IS0 9919......Page 187
REFERENCES......Page 188
INSTRUCTIONAL OBJECTIVES......Page 189
11.1 EVALUATION OF PULSE OXIMETERS......Page 190
11.1.1 Accuracy, bias, precision, and confidence limit......Page 191
11.1.2 What do pulse oximeters really measure?......Page 192
11.1.4 Pulse oximeter versus in vivo eight-wavelength ear oximeter......Page 193
11.2.1 High saturation (greater than 97.5%)......Page 194
11.2.3 Low saturation (less than 80%)......Page 195
11.3.1 Venous congestion......Page 196
11.4 ACCURACY VERSUS MOTION ARTIFACTS......Page 197
11.5 ACCURACY VERSUS OPTICAL INTERFERENCE......Page 198
11.6 ACCURACY VERSUS INTRAVENOUS DYES......Page 199
11.7.1 Carboxyhemoglobin (COHb)......Page 201
11.7.2 Methemoglobin (MetHb)......Page 202
11.7.3 Fetal hemoglobin......Page 203
11.8.1 Ambient temperature......Page 204
11.8.2 Patient temperature......Page 205
11.10 ACCURACY VERSUS PROBE POSITION......Page 206
11.1 1.1 Intelference from magnetic resonance imaging (MRI)......Page 208
11.12.1 Exercise......Page 209
REFERENCES......Page 210
INSTRUCTIONAL OBJECTIVES......Page 212
12.1 INTRODUCTION......Page 213
12.2 FRONT PANEL......Page 214
12.2.1 Graphical displays......Page 215
12.2.2 Numerical displays......Page 217
12.3 FUNCTION CONTROLS......Page 218
12.4 ALARM CONTROLS......Page 220
12.5 COMMUNICATION FUNCTIONS......Page 223
12.7 OTHER FEATURES......Page 224
12.8 COMPLIANCE REQUIREMENTS......Page 225
REFERENCES......Page 226
INSTRUCTIONAL OBJECTIVES......Page 227
13.1 ANESTHESIA......Page 228
13.1.1  Problems encountered during induction to anesthesia......Page 229
13.1.2.2 Thoracic surgery.......Page 230
13.2.1 Intestinal blood flow and bowel viability following surgery......Page 231
13.2.3 Dental pulp blood supply and viability......Page 232
13.3.1 Ambulances......Page 233
13.3.2.3 High performance aircraft.......Page 234
13.4.1 Causes of desaturation in mother and fetus......Page 235
13.4.2 Special apparatus for fetal monitoring......Page 236
13.5 NEONATAL AND PEDIATRIC CARE......Page 238
13.6.1 Sleep......Page 241
13.7 MANAGEMENT OF CARDIOPULMONARY RESUSCITATION......Page 245
13.10 CEREBRAL OXYGEN SATURATION......Page 246
13.11 VETERINARY CARE......Page 247
REFERENCES......Page 248
INSTRUCTIONAL OBJECTIVES......Page 250
GLOSSARY......Page 251