UNITED STATES PATENT AND TRADEMARK OFFICE
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`APPLE INC.,
`Petitioner,
`
`v.
`
`MASIMO CORPORATION,
`Patent Owner.
`____________
`
`Case IPR2022-01291
`U.S. Patent 10,687,745
`
`DECLARATION OF ANNE KOCH BALAND
`
`1
`
`APPLE 1083
`Apple v. Masimo
`IPR2022-01465
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`I, ANNE KOCH BALAND, hereby declare the following:
`
`1.
`
`I am over the age of 18, have personal knowledge of the facts set forth
`
`herein, and am competent to testify to the same. I am a document delivery
`
`librarian in the library department of Fish & Richardson P.C. (hereafter “FR
`
`Library”).
`
`2.
`
`I earned a Master of Library Science (MLIS) from Dominican
`
`University in 2007. I have over 15 years of experience in the library/information
`
`science field.
`
`3.
`
`I am experienced in library cataloging. My responsibilities at the FR
`
`Library include, among other things, accessing and securing copies of documents
`
`requested by attorneys and other staff at FR.
`
`I.
`
`4.
`
`Exhibit 1039
`
`On or around September 8, 2023, I personally retrieved and viewed
`
`ITC Inv. No. 337-TA-1276 Exhibit RX-0504, which is a copy of a document
`
`entitled “Optimization of Reflectance-Mode Pulse Oximeter Sensors” by Austin
`
`Wareing, included below as Appendix A. I accessed the website of Lexis®
`
`CourtLink® at https://www.lexisnexis.com/en-us/products/courtlink.page and
`
`searched for and located the referenced ITC exhibit. Comparing Exhibit 1039 to
`
`2
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`the document attached as Appendix A to this declaration, I certify that Exhibit
`
`1039 is a true and correct copy of ITC Inv. No. 337-TA-1276 Exhibit RX-0504.
`
`II. Exhibit 1040
`
`5.
`
`On or around September 8, 2023, I personally retrieved and viewed
`
`ITC Inv. No. 337-TA-1276 Exhibit RX-0508, which is a copy of a paper entitled
`
`“Stimulating Student Learning with a Novel ‘In-House’ Pulse Oximeter Design”
`
`by Jianchu Yao and Steve Warren, included below as Appendix B. I accessed the
`
`website of Lexis® CourtLink® at https://www.lexisnexis.com/en-
`
`us/products/courtlink.page and searched for and located the referenced ITC exhibit.
`
`Comparing Exhibit 1040 to the document attached as Appendix B to this
`
`declaration, I certify that Exhibit 1040 is a true and correct copy of ITC Inv. No.
`
`337-TA-1276 Exhibit RX-0508.
`
`III. Exhibit 1041
`
`6.
`
`On or around September 8, 2023, I personally retrieved and viewed
`
`ITC Inv. No. 337-TA-1276 Exhibit RX-0632, included below as Appendix C. I
`
`accessed the website of Lexis® CourtLink® at https://www.lexisnexis.com/en-
`
`us/products/courtlink.page and searched for and located the referenced ITC exhibit.
`
`Comparing Exhibit 1041 to the document attached as Appendix C to this
`
`declaration, I certify that Exhibit 1041 is a true and correct copy of ITC Inv. No.
`
`337-TA-1276 Exhibit RX-0632.
`
`
`
`3
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`IV. Exhibit 1043
`
`7.
`
`I personally obtained and viewed an excerpt including the definition
`
`of “correspond” from The American Heritage Dictionary of the English Language,
`
`Fifth Edition (Houghton Mifflin Harcourt Publishing Company 2011), included
`
`below as Appendix D. The excerpt was obtained from Retriev-It
`
`(https://www.retrievit.com), a document retrieval company, on or around
`
`September 8, 2023. Comparing Exhibit 1043 to the document attached as
`
`Appendix D to this declaration, I certify that Exhibit 1043 is a true and correct
`
`copy of the excerpt from The American Heritage Dictionary of the English
`
`Language, Fifth Edition (Houghton Mifflin Harcourt Publishing Company 2011)
`
`obtained from Retriev-It.
`
`V. Exhibit 1044
`
`8.
`
`I personally obtained and viewed the excerpt including the definition
`
`of “correspond” from Collins Dictionary (HarperCollins Publishers 2010),
`
`included below as Appendix E. The excerpt was obtained from Retriev-It
`
`(https://www.retrievit.com), on or around September 8, 2023. Comparing Exhibit
`
`1044 to the document attached as Appendix E to this declaration, I certify that
`
`Exhibit 1044 is a true and correct copy of the excerpt from Collins Dictionary
`
`(HarperCollins Publishers 2010) obtained from Retriev-It.
`
`
`
`4
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`VI. Exhibit 1045
`
`9.
`
`I personally obtained and viewed an excerpt including the definition
`
`of “correspond” from Merriam-Webster’s Collegiate Dictionary, Eleventh Edition
`
`(Merriam-Webster, Incorporated 2014), included below as Appendix F. The
`
`excerpt was obtained from Retriev-It (https://www.retrievit.com), on or around
`
`September 8, 2023. Comparing Exhibit 1045 to the document attached as
`
`Appendix F to this declaration, I certify that Exhibit 1045 is a true and correct copy
`
`of the excerpt from Merriam-Webster’s Collegiate Dictionary, Eleventh Edition
`
`(Merriam-Webster, Incorporated 2014) obtained from Retriev-It.
`
`VII. Exhibit 1046
`
`10.
`
`I personally obtained and viewed an excerpt from the publication
`
`titled “The Biomedical Engineering Handbook” by Joseph D. Bronzino (CRC
`
`Press, Inc. 1995), included below as Appendix G. The publication was obtained
`
`from Research Solutions (https://www.researchsolutions.com), a document
`
`retrieval company, on or around September 8, 2023. Comparing Exhibit 1046 to
`
`the document attached as Appendix G to this declaration, I certify that Exhibit
`
`1046 is a true and correct copy of the excerpt from “The Biomedical Engineering
`
`Handbook” by Joseph D. Bronzino (CRC Press, Inc. 1995) obtained from Research
`
`Solutions.
`
`
`
`5
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`VIII. Exhibit 1048
`
`11. On or around September 8, 2023, I personally retrieved and viewed
`
`the paper entitled “Recent Developments in Pulse Oximetry,” by John W.
`
`Severinghaus and Joseph F. Kelleher published in Anesthesiology, Vol. 76, No. 6
`
`(June 1992), included below as Appendix H. I accessed the website of
`
`Anesthesiology at https://pubs.asahq.org/anesthesiology and searched for and
`
`located the referenced publication. Comparing Exhibit 1048 to the document
`
`attached as Appendix H to this declaration, I certify that Exhibit 1048 is a true and
`
`correct copy of “Recent Developments in Pulse Oximetry,” by John W.
`
`Severinghaus and Joseph F. Kelleher published in Anesthesiology, Vol. 76, No. 6
`
`(June 1992).
`
`IX. Exhibit 1049
`
`12. On or around September 8, 2023, I personally retrieved and viewed
`
`the article entitled “MIO Alpha BLE Review” by Jill Duffy published on the PC
`
`Magazine website (Jan. 28, 2013), included below as Appendix I. I accessed the
`
`website of PC Magazine at https://www.pcmag.com/reviews/mio-alpha-ble to
`
`retrieve the referenced article. Comparing Exhibit 1049 to the document attached
`
`as Appendix I to this declaration, I certify that Exhibit 1049 is a true and correct
`
`copy of “MIO Alpha BLE Review” by Jill Duffy published on the PC Magazine
`
`website (Jan. 28, 2013).
`
`
`
`6
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`X. Exhibit 1050
`
`13.
`
`I personally retrieved and viewed the publication entitled “A Neo-
`
`Reflective Wrist Pulse Oximeter,” by Grantham Pang and Chao Ma published by
`
`IEEE in IEEE Access, Volume 2 (January 12, 2015), included below as Appendix
`
`J. I accessed the website of IEEE Xplore at
`
`https://ieeexplore.ieee.org/Xplore/home.jsp and searched for and located the
`
`referenced publication. Comparing Exhibit 1050 to the document attached as
`
`Appendix J to this declaration, Exhibit 1050 is a true and correct copy of “A Neo-
`
`Reflective Wrist Pulse Oximeter,” by Grantham Pang and Chao Ma.
`
`XI. Exhibit 1051
`
`14.
`
`I personally retrieved and viewed the publication entitled “A Wireless
`
`Reflectance Pulse Oximeter With Digital Baseline Control for Unfiltered
`
`Photoplethysmograms” by Kejia Li and Steve Warren published in IEEE
`
`Transactions on Biomedical Circuits and Systems, Vol. 6, No. 3 (June 2012),
`
`included below as Appendix K. I accessed the website of IEEE Xplore at
`
`https://ieeexplore.ieee.org/Xplore/home.jsp and searched for and located the
`
`referenced publication on or around September 8, 2023. Comparing Exhibit 1051
`
`to the document attached as Appendix K to this declaration, I certify that Exhibit
`
`1051 is a true and correct copy “A Wireless Reflectance Pulse Oximeter With
`
`
`
`7
`
`

`

`Digital Baseline Control for Unfiltered Photoplethysmograms” by Kejia Li and
`
`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`Steve Warren.
`
`XII. Exhibit 1052
`
`15. On or around September 8, 2023, I personally retrieved and viewed
`
`U.S. Patent Application Publication No. 2006/0253010 issued to Brady et al.,
`
`included below as Appendix L. I accessed the website of Patsnap at
`
`https://www.patsnap.com, accessed a user account, and searched for and located
`
`the referenced publication. Comparing Exhibit 1052 to the document attached as
`
`Appendix L to this declaration, I certify that Exhibit 1052 is a true and correct
`
`copy of U.S. Patent Application Publication No. 2006/0253010 to Brady et al.
`
`XIII. Exhibit 1053
`
`16. On or around September 8, 2023, I personally retrieved and viewed
`
`the publication entitled “Implementation of a Wireless Pulse Oximeter Based on
`
`Wrist Band Sensor” by Cai et al. published for the 3rd International Conference on
`
`Biomedical Engineering and Informatics (BMEI 2010), included below as
`
`Appendix M. I accessed the website of IEEE Xplore at
`
`https://ieeexplore.ieee.org/Xplore/home.jsp and searched for and located the
`
`referenced publication. Comparing Exhibit 1053 to the document attached as
`
`Appendix M to this declaration, I certify that Exhibit 1053 is a true and correct
`
`
`
`8
`
`

`

`copy of “Implementation of a Wireless Pulse Oximeter Based on Wrist Band
`
`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`Sensor” by Cai et al.
`
`XIV. Exhibit 1054
`
`17.
`
`I personally retrieved and viewed International Publication No. WO
`
`2001/17421 by Lindberg et al, included below as Appendix N. I accessed the
`
`website of Patsnap at https://www.patsnap.com, accessed a user account, and
`
`searched for and located the referenced publication on or around September 8,
`
`2023. Comparing Exhibit 1054 to the document attached as Appendix N to this
`
`declaration, I certify that Exhibit 1054 is a true and correct copy of International
`
`Publication No. WO 2001/17421 by Lindberg et al.
`
`XV. Exhibit 1055
`
`18.
`
`I personally retrieved and viewed the publication entitled, “Optimum
`
`Place for Measuring Pulse Oximeter Signal in Wireless Sensor-Belt or Wrist-
`
`Band” by Maattala et al. published for the 2007 International Conference on
`
`Convergence Information Technology by the Institute of Electrical and Electronics
`
`Engineers (IEEE) (2007), included below as Appendix O. I accessed the website
`
`of IEEE Xplore at https://ieeexplore.ieee.org/Xplore/home.jsp and searched for and
`
`located the referenced publication on or around September 8, 2023. Comparing
`
`Exhibit 1055 to the document attached as Appendix O to this declaration, I certify
`
`
`
`9
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`that Exhibit 1055 is a true and correct copy of “Optimum Place for Measuring
`
`Pulse Oximeter Signal in Wireless Sensor-Belt or Wrist-Band,” by Maattala et al.
`
`XVI. Exhibit 1056
`
`19.
`
`I personally retrieved and viewed the publication entitled
`
`“Reflectance-Based Pulse Oximeter for the Chest and Wrist” by Fontaine et al.
`
`submitted to the Worchester Polytechnic Institute, included below as Appendix P.
`
`I accessed the website of the Worcester Polytechnic Institute at
`
`https://www.wpi.edu and searched for and located the referenced publication on or
`
`around September 8, 2023. Comparing Exhibit 1056 to the document attached as
`
`Appendix P to this declaration, I certify that Exhibit 1056 is a true and correct copy
`
`of “Reflectance-Based Pulse Oximeter for the Chest and Wrist” by Fontaine et al.
`
`XVII. Exhibit 1058
`
`20.
`
`I personally retrieved and viewed U.S. Patent No. 7,468,036 issued to
`
`Rulkov et al., included below as Appendix Q. I accessed the website of Patsnap at
`
`https://www.patsnap.com, accessed a user account, and searched for and located
`
`the referenced publication on or around September 8, 2023. Comparing Exhibit
`
`1058 to the document attached as Appendix Q to this declaration, I certify that
`
`Exhibit 1058 is a true and correct copy of U.S. Patent No. 7,468,036 issued to
`
`Rulkov et al.
`
`
`
`10
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`XVIII.
`
`Exhibit 1069
`
`21.
`
`I personally retrieved and viewed the publication entitled “Optical
`
`Oximetry Sensors for Whole Blood and Tissue” by Setsuo Takatani and Jian Ling
`
`published in IEEE Engineering in Medicine and Biology (June/July 1994),
`
`included below as Appendix R. I accessed the website of IEEE Xplore at
`
`https://ieeexplore.ieee.org/Xplore/home.jsp and searched for and located the
`
`referenced publication on or around September 8, 2023. Comparing Exhibit 1069
`
`to the document attached as Appendix R to this declaration, I certify that Exhibit
`
`1069 is a true and correct copy of “Optical Oximetry Sensors for Whole Blood and
`
`Tissue” by Setsuo Takatani and Jian Ling.
`
`XIX. Exhibit 1076
`
`22.
`
`I personally retrieved and viewed the web page entitled “Beam
`
`Shaping with Cylindrical Lenses” published by Newport Corporation at
`
`https://www.newport.com/n/beam-shaping-with-cylindrical-lenses, included below
`
`as Appendix S. I accessed the web page https://www.newport.com/n/beam-
`
`shaping-with-cylindrical-lenses of Newport Corporation’s website and retrieved
`
`the referenced web page on or around September 8, 2023. Comparing Exhibit
`
`1076 to the document attached as Appendix S to this declaration, I certify that
`
`Exhibit 1076 is a true and correct copy of “Beam Shaping with Cylindrical
`
`Lenses,” by the Newport Corporation.
`
`
`
`11
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`XX. Exhibit 1077
`
`23. On or around September 12, 2003, I personally retrieved and viewed
`
`the publication entitled “Laser Beam Shaping Theory and Techniques, Second
`
`Edition” by Fred M. Dickey published by Taylor & Francis Group, LLC (2014). I
`
`accessed the website of Amazon at www.amazon.com, accessed a user account,
`
`and searched for, located, and purchased the Kindle version of the referenced
`
`publication; a receipt of the purchase and screenshots of the Kindle version are
`
`attached as Appendix T. Comparing Exhibit 1077 to the document attached as
`
`Appendix T to this declaration, Exhibit 1077 is a true and correct copy of “Laser
`
`Beam Shaping Theory and Techniques, Second Edition” by Fred M. Dickey.
`
`XXI. Exhibit 1078
`
`24. On or around September 8, 2023, I personally retrieved and viewed
`
`the publication entitled “Micro-LED Technologies and Applications” by Lee et al.
`
`published in Information Display (June 2016), included below as Appendix U. I
`
`accessed the website of The Society for Information Display at
`
`https://sid.onlinelibrary.wiley.com and searched for and located the referenced
`
`publication. Comparing Exhibit 1078 to the document attached as Appendix U to
`
`this declaration, I certify Exhibit 1078 is a true and correct copy of “Micro-LED
`
`Technologies and Applications” by Lee et al.
`
`
`
`
`
`
`
`12
`
`

`

`Case No. IPR2022-01291
`Attorney Docket No. 50095-0045IP1
`
`
`26.
`
`I hereby declare that all statements made herein of my own
`
`knowledge are true and that all statements made on information and belief are
`
`believed to be true; and further that these statements were made with the
`
`knowledge that willful false statements and the like so made are punishable by fine
`
`or imprisonment, or both, under Section 1001 of Title 18 of the United States
`
`Code.
`
`
`
`
`Date: September 12, 2023
`
`
`
`
`
`
`Respectfully submitted,
`
`/Anne Koch Baland/
`
`
`
`
`Anne Koch Baland
`
`
`
`
`
`
`
`
`
`
`13
`
`

`

`
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`
`
`APPENDIX A
`APPENDIX A
`
`14
`
`

`

`RX-0504
`
`RX-0504.0001
`
`APL_MAS_ITC_00377841
`
`expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.
`This material is based upon work supported by the National Science Foundation under grants BES(cid:150)0440183 and BES(cid:150)0093916. Opinions, findings, conclusions, or recommendations
`
`16
`
`14
`
`12
`
`10
`
`time (sec)
`
`8
`
`16
`
`14
`
`12
`
`10
`
`time (sec)
`
`8
`
`6
`
`6
`
`4
`
`4
`
`2
`
`2
`
`Original Data
`
`Finger
`
`0
`
`-4
`
`-2
`
`024
`
`RED AC
`
`0
`
`-1.5
`
`-1
`
`-0.5
`
`0
`
`0.5
`
`1
`
`IR AC
`
`Pulse Oximeter Sensor
`
`14
`
`12
`
`10
`
`14
`
`12
`
`10
`
`8
`
`8
`
`time (sec)
`
`time (sec)
`
`6
`
`6
`
`Original Data
`
`4
`
`4
`
`2
`
`2
`
`0
`
`-0.6
`
`-0.4
`
`-0.2
`
`0
`
`0.2
`
`0.4
`
`0
`
`-1
`
`-0.5
`
`0
`
`0.5
`
`1
`
`IR AC
`
`RED AC
`
`mold to a curved surface.
`(cid:149)More ambient light noise due to holes in plastic and inability to
`(cid:149)Hard plastic material does not conform to most skin surfaces.
`resulting in poor efficiency and a smaller signal-to-noise ratio.
`(cid:149)One photodiode collects reflected red and infrared signals,
`
`primarily forward scattering. Increasing the reliability and quality of reflectance-mode signals will make these sensors a more attractive alternative to traditional transmission-mode designs.
`flexibility since they are only mounted on one side of the skin.However, these sensors are at a disadvantage since they collect only a fraction of the light reflected from tissue, which is
`surface, or reflection-mode, where light is reflected back towards the sensor and collected in the same region as the incident light. Reflectance-mode sensors offer more measurement-site
`the patients skin and underlying tissue. Pulse oximeter sensorscan either be transmission-mode, where light passes completely through the tissue and is collected on an opposing skin
`Pulse oximeters provide physiological information such as heart rate and blood oxygen saturation. These devices acquire measurements using red and infrared light that passes through
`
`Sponsor: National Science Foundation Research Experiences for Undergraduates Program; Advisor: Steve Warren, Ph.D.
`
`PreviousDesign
`
`(cid:149)Head-mounted sensors have also proven to be less obtrusive since theydo not impede
`(cid:149)Measurements from sites on the head are similar to those collected from sites on the finger.
`
`movement or use of the hands.
`
`25
`
`20
`
`15
`
`time (sec)
`
`10
`
`25
`
`20
`
`15
`
`time (sec)
`
`10
`
`5
`
`5
`
`Original Data
`
`Middle Temporal Artery
`
`0
`
`-2
`
`-1
`
`012
`
`0
`
`-2
`
`-1
`
`012
`
`IR AC
`
`RED AC
`
`(cid:149)Wrist
`(cid:149)Frontal branch (along hair line)
`(cid:149)Middle temporal artery (in front of ear)
`Viable and Unobtrusive Measuring Sites
`
`parameters.
`to calculate different physiological
`plethysmograms that can be used
`(cid:149)Provides time-domain
`are unimposing to the wearer.
`(cid:149)Small, Lightweight components
`
`collect viable data.
`previous design; less effort is required to
`(cid:149)Signal is also more reliable than with the
`ratio.
`(cid:149)Output signal exhibits greater signal-to-noise
`
`Measurement Site Comparison
`
`10
`
`9
`
`8
`
`7
`
`6
`
`time (sec)
`
`5
`
`4
`
`3
`
`2
`
`1
`
`0
`
`-3
`
`-2
`
`-1
`
`012
`
`RED AC
`
`10
`
`9
`
`8
`
`7
`
`6
`
`time (sec)
`
`5
`
`4
`
`3
`
`2
`
`1
`
`Original Data
`
`0
`
`-1
`
`-0.5
`
`0
`
`0.5
`
`1
`
`1.5
`
`IR AC
`
`several attempts to collect viable data.
`(cid:149)Signal is often difficult to obtain, requiring
`sensor movement.
`(cid:149)Signal-to-noise ratio is highly dependent on
`
`material and flexible design.
`(cid:149)Less susceptible to ambient noise due to opaque
`measurement site.
`(cid:149)Pliable material allows the sensor to conform to the
`forming a radial pattern around the source(s).
`(cid:149)Multiple photodiodes collect more of the reflected light,
`
`Optimized Design
`
`Optimization of Reflectance-Mode Pulse Oximeter Sensors
`
`Austin Wareing, B.S.
`
`15
`
`

`

`APPENDIX B
`APPENDIX B
`
`16
`
`

`

`RX-0508
`
`RX-0508.0001
`
`APL_MAS_ITC_00378252
`
`Page 10.1138.1
`
`Stimulating Student Learning with a Novel “In-House”
`Pulse Oximeter Design
`
`Jianchu Yao, M.S. and Steve Warren, Ph.D.
`Department of Electrical & Computer Engineering, Kansas State University
`Manhattan, KS 66506, USA
`
`Abstract
`This paper addresses the design of a plug-and-play pulse oximeter and its application to a
`biomedical instrumentation laboratory and other core Electrical Engineering courses. The low-
`cost, microcontroller-based unit utilizes two light-emitting diodes as excitation sources, acquires
`reflectance data with a photodiode, and sends these raw photo-plethysmographic data to a
`personal computer via an RS-232 serial link. A LabVIEW interface running on the personal
`computer processes these raw data and stores the results to a file. The design of this pulse
`oximeter is unique in two ways: the excitation sources are driven just hard enough to always
`keep the photodiode active (meaning the sensor can be used in ambient light), and the hardware
`separates out the derivatives of the red and infrared photo-plethysmograms so that it can amplify
`the pulsatile component of each signal to fill the range of the analog-to-digital converter. Unlike
`commercial pulse oximeters whose packaging hides the hardware configuration from the
`students, the open, unpackaged design stimulates student interest and encourages dialogue with
`the developer; the in-house nature of the design appeals to students. Moreover, most pulse
`oximeters on the market are expensive and provide users with a front panel that displays only
`percent oxygen saturation and heart rate. This low-cost unit provides unfiltered pulsatile data,
`allowing students to investigate tradeoffs between different oxygen saturation calculation
`methods, test different filtering approaches (e.g., for motion artifact reduction), and extract other
`biomedical parameters (e.g., respiration rate and biometric indicators). Time-domain data from
`these units have been used in linear systems and scientific computing courses to teach filtering
`techniques, illustrate discrete Fourier transform applications, introduce time-frequency
`principles, and test data fitting algorithms.
`
`I. Introduction
`An optical pulse oximeter measures the intensity of light passing through heterogeneous tissue
`and uses variations in this light intensity (primarily resulting from the fractional volume variation
`of arterial blood) to calculate blood oxygen saturation. Due to its non-invasive nature, high
`precision in its operational range, and reasonable cost, optical pulse oximetry is widely adopted
`as a standard patient monitoring technique. Although its foundations date back more than fifty
`years,1 many facets of this technology still attract researchers. Current interest areas include
`motion artifact reduction,2, 3 power consumption optimization,4 low-perfusion measurements,5, 6
`and issues germane to various application environments (e.g., wearability for battlefield and
`home care monitors).7-9 It is important for biomedical engineering students to understand the
`principles of pulse oximetry, hardware/software design issues, and signal processing approaches.
`
`Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition
`Copyright © 2005, American Society for Engineering Education
`
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`Pulse oximeter design addresses engineering areas such as optical component selection,
`mechanical layout, circuit design, microprocessor control, digital communication, and signal
`processing. Therefore, a pulse oximeter not only serves as an excellent study vehicle that allows
`students to learn techniques such as photoplethysmographic signal processing; it also provides a
`platform where students can acquire hands-on experience in practical device design. In addition,
`the real-time data that a pulse oximeter offers gives instructors flexibility when assigning
`projects and homework to students of various educational levels (graduate and undergraduate)
`and backgrounds (e.g., electrical engineering or biology).
`
`Many commercial pulse oximeters display calculated parameters (i.e., percent oxygen saturation
`and heart rate) on their front panels, hiding the original unfiltered data from which these
`calculations were made. In this paper, we present an “in-house” pulse oximeter that provides raw
`sensor data for use in the classroom. The device is utilized in bioinstrumentation laboratory
`sessions, and its data provide real-world signals to other core Electrical Engineering courses.
`
`This paper first briefly describes the theory behind photoplethysmographic (PPG) pulse oximetry.
`It then presents the development of a pulse oximeter, emphasizing design features that enable its
`application to education. These features include (a) a stand-alone pulse oximeter module with a
`novel circuit design, an open form-factor, and multiple signal outputs, (b) a personal computer
`station with a flexible, user friendly LabVIEW interface and a variety of signal processing
`options, and (c) the production of raw data that can be used for parameter extraction exercises.
`The paper describes how this device and it features have been applied in classroom environments
`to stimulate student learning. Several examples are introduced in detail, including (a) a pulse
`oximetry laboratory/lecture pair for a bioinstrumentation course sequence, (b) data sources for
`course projects in Linear Systems (EECE 512) and Scientific Computing (EECE 840), and (c) a
`platform upon which undergraduate honors research students can build. This approach can be
`extended to other devices and classes.
`
`II. Theory – Principles of Pulse Oximetry
`PPG pulse oximetry relies on the fractional change in light absorption due to arterial pulsations.
`In a typical configuration, light at two different wavelengths illuminating one side of tissue (e.g.,
`a finger) will be detected on the same side (reflectance mode) or the opposing side (transmission
`mode) after traversing the vascular tissues between the source and the detector.10 When a
`fingertip is simplified as a hemispherical volume that is a homogenous mixture of blood (arterial
`and venous) and tissue, the detected light intensity is described by the Beer-Lambert law: 11
`(
`)(
`)(
`)A
`−
`µ
`µ
`−
`−
`µ
`=
`T
`V
`
`(1)
`
`I
`eI
`e
`e
`av
`aa
`at
`0
`t
`where I0 is the incident light intensity, It is the light intensity detected by the photodetector, and
`µat, µav, and µaa are the absorption coefficients of the bloodless tissue layer, the venous blood
`layer, and the arterial blood layer, respectively, in units of cm-1.
`
`The heart’s pumping action generates arterial pulsations that result in relative changes in arterial
`blood volume, represented by dA, which adds an “ac” component to the detected intensity:
`(
`)(
`)(
`−=
`µµ
`−
`µ
`−
`µ
`−
`T
`V
`A
`dI
`I
`e
`e
`e
`av
`aa
`
`
`
`
`t
`
`0
`
`aa
`
`at
`
`)dA
`
`
`
`(2)
`
`Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition
`Copyright © 2005, American Society for Engineering Education
`
`
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`18
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`Multiple elements contribute to the attenuation of light traveling through tissue, and arterial
`pulsation has only a small relative effect on the amount of light detected (on the order of one
`percent or less; see Figure 1).
`
`
`Absorption due to
`pulsatile arterial blood
`
`1
`
`10
`
`100
`
`Absorption due to non-
`pulsatile arterial blood
`
`Absorption due to
`venous blood
`
`Absorption due to
`skin, bone and tissue
`
`
`Figure 1. Breakdown of the components in the detected photo-plethysmographic signal.12
`
`
`Dividing this change by the dc value normalizes this variation:
`I
`=
`µ−=
`
`dA
`
`aa
`
`t
`
`Id
`
`ac
`
`II
`
`
`
`dc
`t
`The ratio of the above ratio for two wavelengths (‘r’ for red, ‘IR’ for infrared) is given by
`(
`)
`/
`dI
`I
`=
`=
`(
`)
`/
`dI
`I
`,
`
`
`IRa,
`IR
`where µa,i can be expressed as a function of
`,13 arterial oxygen saturation:
`[
`]%0
` ( −+
`
`
`)σ
`µ
`=
`1
`OS
`a
`
`
` IRr,=
`
`are the wavelength-dependent optical absorption cross
`and
`, while
`Here,
`i
`sections of the red blood cells containing totally oxygenated and totally deoxygenated
`hemoglobin, respectively. One can therefore calculate arterial oxygen saturation using
`
`σσ −
`%0
`%0
`R
`(σ
`)+
`( σσ
`)%100
`=
`
`,ra
`
`,IRa
`σ
`
`
`%0
`%0
`R
`
`,IRa
`
`,ra
`
`(3)
`
`(4)
`
`(5)
`
`(6)
`
`µµ
`
`
`
`ra,
`
`OS
`a
`
`2
`
`a
`
`t
`
`t
`
`r
`
`t
`t
`2OSa
`σ
`
`%100
`a
`
`2
`
`R
`
`vH
`
`i
`
`
`
`%100
`
`,ra
`
`−
`
` −
`
`
`
`,IRa
`
`
`
`,
`ia
`
`aσ
`
`%0
`
`aσ
`
`%100
`
`OS
`2
`a
`
`
`
`Equation (6) provides the desired relationship between the experimentally-determined ratio R
`and the arterial oxygen saturation SaO2. Researchers assume this relationship applies to
`monochromatic light sources. In reality, commonly available LEDs are used as light sources and
`typically have spectral widths of 20 to 50 nm. Therefore, the standard molar absorption
`coefficient for hemoglobin cannot be used directly in (6). Furthermore, the simplified
`mathematical description above only approximates a real system that incorporates
`
`Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition
`Copyright © 2005, American Society for Engineering Education
`
`
`
`19
`
`

`

`. + ... :.·+··1
`
`I 911
`JP 10'------
`t
`.
`! i
`: 1
`'
`I, ....................
`··········;=················r---········::::.·:::::::i.·J .... .1.. .......... i .. i
`, .. ::::::········t
`.
`'
`········i··············
`·s········
`t
`,
`____,I
`I
`................
`.................................................................................................... .!
`
`: I
`
`~
`----+
`·········►
`
`RX-0508.0004
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`APL_MAS_ITC_00378255
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`Page 10.1138.4
`
`2
`
`
`
`(7)
`
`2
`
`inhomogeneities and mechanical movement. Consequently, (6) is often represented empirically
`by fitting clinical data to the following generalized function:
`=
`+
`kRk
`OS a
`
`1
`where, e.g., k1= -25.6, k2= 118.814 or k1= -25, k2= 110.15
`
`III. Methods
`A. Pulse Oximeter Development
`As shown in the functional block diagram in Figure 2, a pulse oximeter consists of three main
`units: (1) an optical probe, (2) a circuit module that hosts an analog amplifier, signal
`conditioning element, and microcontroller, and (c) a personal computer that receives data from
`the circuit module and processes, displays, and stores these data.
`
`
`Display
`Processing
`Storage
`
`
`RS-232
`
`Control signals
`
`Microcontroller
`
`Circuit
`Module
`
`Probe
`
`LEDs
`
`Finger
`
`Photodetector
`
`
`
`Current feedback
`
`Light-feedback
`amplifier
`
`Differentiator with
`holding circuit
`
`A/D
`
`Optical signal
`Analog signal
`Digital signal
`
`
`
`Figure 2. Functional block diagram of the pulse oximeter.
`
`
`The analog portion of the pulse oximeter consists of a light-feedback amplifier and an analog
`differentiator with a specialized sample and hold circuit. The current feedback design adjusts the
`light level at the excitation LEDs such that the detected light intensity is constant, keeping the
`photodiode centered in its active region. To improve the stability of this feedback loop, a
`photodiode with smaller gain, rather than a phototransistor, is used as a photodetector. Two
`LEDs with wavelengths of 660 nm and 940 nm were selected as excitation sources.
`
`As discussed earlier, the “ac” component resulting from arterial blood volume variation is very
`small. If A/D conversion is performed on the overall signal, this tiny “ac” component will be
`buried in the “huge” “dc” component after conversion. A differentiator addresses this issue. It
`removes the “dc” component by subtracting the previous signal voltage-level from the present
`signal voltage-level and amplifies this difference, yielding the “ac” component. A hold circuit is
`added to store voltage-levels from the previous sample cycle. The differentiator improves signal
`resolution by allowing one to take advantage of the full range of the A/D converter.
`
`This circuitry is coordinated by a PIC microcontroller. Three output lines control the operation of
`the circuitry, and two A/D inputs sample the desired signal. Two outputs modulate the two light
`sources and switch the charging and discharging of their corresponding hold capacitors. The
`
`Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition
`Copyright © 2005, American Society for Engineering Education
`
`
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`20
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`RX-0508.0005
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`
`other output operates the differentiator. The two A/D inputs acquire and digitize two signals: the
`“dc” signal when the differentiator is turned off (it is actually the original signal that includes
`both “dc” and “ac” components) and the amplified difference of the present and previous voltage
`level when the differentiator is turned on