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To the proposer’s knowledge, is this achievement subject to litigation? No
Is the achievement you are proposing more than 25 years old? Yes
Is the achievement you are proposing within IEEE’s designated fields as defined by IEEE Bylaw I-104.11, namely: Engineering, Computer Sciences and Information Technology, Physical Sciences, Biological and Medical Sciences, Mathematics, Technical Communications, Education, Management, and Law and Policy. Yes
Did the achievement provide a meaningful benefit for humanity? Yes
Was it of at least regional importance? Yes
Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)? Yes
Has an IEEE Organizational Unit agreed to arrange the dedication ceremony? Yes
Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated? Yes
Has the owner of the site agreed to have it designated as an IEEE Milestone? Yes
Year or range of years in which the achievement occurred:
Title of the proposed milestone:
Invention of Pulse Oximeter, 1972
Plaque citation summarizing the achievement and its significance:
A 'pulse oximeter' is a medical device for monitoring noninvasively a patient’s blood oxygen saturation, invented in 1972 by Dr. Takuo Aoyagi at Nihon Kohden (Japan). Owing to their contents of continuous and immediate oxygen saturation values, ‘pulse oximeters’ are essential to emergency medicine, and are also very useful for patients with respiratory or cardiac problems as well as for diagnosis of sleep disorders such as apnea and hypopnea.
In what IEEE section(s) does it reside?
IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:
IEEE Organizational Unit(s) paying for milestone plaque(s):
Unit: Tokyo Section
Senior Officer Name: Yoshiaki Nakano
IEEE Organizational Unit(s) arranging the dedication ceremony:
Unit: Tokyo Section
Senior Officer Name: Yoshiaki Nakano
IEEE section(s) monitoring the plaque(s):
IEEE Section: Tokyo Section
IEEE Section Chair name: Yoshiaki Nakano
Proposer name: Hiroshi Suzuki
Proposer email: Proposer's email masked to public
Proposer name: Isao Shirakawa
Proposer email: Proposer's email masked to public
Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.
Street address(es) and GPS coordinates of the intended milestone plaque site(s):
Nihon Kohden Corporation. Address: 1-31-4 Nishi-Ochiai, Shinjuku-ku, Tokyo 161-8560, Japan, GPS coordinates: N 35.71951, E 139.67898
Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.
Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need. The entrance hall of Nihon Kohden Corporation.
Are the original buildings extant?
The original building is extant, and presently belongs to Nihon Kohden Corporation.
Details of the plaque mounting:
The plaque will be displayed at the entrance hall of Nihon Kohden Corporation.
How is the site protected/secured, and in what ways is it accessible to the public?
The plaque will be displayed in a showcase placed at the entrance hall of Nihon Kohden Corporation, which can be accessible to the public with permission.
Who is the present owner of the site(s)?
Mr. Hirokazu Ogino, President & CEO of Nihon Kohden Corporation.
What is the historical significance of the work (its technological, scientific, or social importance)?
The major historical significance of developing 'pulse oximeters’ is summarized in what follows.
1. Historical Background of Developing 'Pulse Oximeters'
The supplementary oxygen is indispensable to patients with respiratory or cardiac problems, pilots operating in unpressurized aircraft, mountain climbers at high altitudes, athletes pursuing their physical exercises, etc. Pulse oximetry is based on a unique concept to compute a person's arterial oxygen saturation without need for calibration, using the pulsatile variations in optical density of tissues in the red and infrared wavelengths. Thus, pulse oximetry is particularly convenient for noninvasive continuous measurement of blood oxygen saturation [1,2].
A ‘pulse oximeter’ was invented in 1972 by Dr. Takuo Aoyagi at a Japanese medical electronic equipment manufacturer Nihon Kohden Corporation, and it has since been used as a medical device that noninvasively monitors the oxygen saturation of a patient’s blood and changes in blood volume in the skin [1-5]. A typical 'pulse oximeter' uses an electronic processor and a pair of small LEDs (light-emitting diodes) facing a photodiode through a translucent part of the patient’s body, usually a fingertip or an earlobe, as can be seen from Fig. 1 , where it should be added that one LED is red with wavelength of 660 nm, and the other infrared with wavelength of 940 nm. Media:(Pulse.pdf)
2. Activities for Commercializing Pulse Oximeters
Pulse oximetry is a noninvasive method for monitoring a person’s blood oxygen saturation. In what follows, a number of activities implemented for commercializing 'pulse oximeters' are described.
(1) Pulse oximetry is found not only conducive to noninvasive measurement of a patient's blood oxygen saturation, but also useful in any setting where a patient’s oxygenation is unstable, including intensive care, operating, emergency and hospital ward settings, pilots in unpressurized aircraft, for assessment of any patient's oxygenation, and determining the effectiveness of or need for supplemental oxygen. Thus, the ‘pulse oximeter’ is adopted as a medical device for monitoring noninvasively a patient’s blood oxygen saturation .
(2) Because of their simplicity of use and the ability to provide continuous and immediate oxygen saturation values, ‘pulse oximeters’ are of critical importance in emergency medicine and are also very useful for patients with respiratory or cardiac problems, especially COPD, as well as for diagnosis of sleep disorders such as apnea and hypopnea .
(3) Portable battery-operated ‘pulse oximeters’ are indispensable not only to pilots operating in unpressurized aircraft above 4,000 m where supplemental oxygen is required, but also to mountain climbers and athletes whose oxygen levels may decrease at high altitudes and with exercise, respectively .
(4) Connectivity advancements have made it possible for patients to have their blood oxygen saturation continuously monitored without a cabled connection to a hospital monitor, not sacrificing the flow of patient data back to bedside monitors or centralized patient surveillance systems .
(5) For patients with COVID-19, pulse oximetry helps with early detection of silent hypoxia, in which the patients still look and feel comfortable, but their SpO2 (peripheral oxygen saturation) is perilously low, where it should be noted that such law SpO2 may indicate severe COVID-19 related pneumonia, requiring a ventilator .
(6) Thanks to Dr. Takuo Aoyagi's great achievement of inventing the 'pulse oximeter', he was honored in 2015 with 'IEEE Medal for Innovations in Healthcare Technology' for the first time in Japan .
What obstacles (technical, political, geographic) needed to be overcome?
The idea of pulse oximetry originated in Japan, where device development lagged due to a lack of business, clinical, and academic interest. To the contrary, awareness of the importance of anesthesia safety in USA led to widespread use of pulse oximetry around the world, due to academic foresight and media attention in combination with excellence in technological innovation . In what follows, a number of obstacles needed to be overcome for the progress of pulse oximetry are pointed out:
(1) Pulse oximetry solely measures hemoglobin saturation, but it is not a complete measure of respiratory sufficiency, nor a substitute for blood gases checked in a laboratory, because it gives no indication of base deficit, carbon dioxide levels, blood pH, or bicarbonate concentration. The metabolism of oxygen can be readily measured by monitoring expired CO2, but saturation figures give no information about blood oxygen content .
(2) Since pulse oximeter devices are calibrated in healthy subjects, the accuracy is poor for critically ill patients and preterm newborns .
(3) Obesity, hypotension, and some hemoglobin variants can reduce the accuracy of the results. Some home pulse oximeters have low sampling rates which can significantly underestimate dips in blood oxygen levels. The accuracy of pulse oximetry deteriorates considerably for readings below 80% .
(4) Since pulse oximetry measures only the percentage of bound hemoglobin, a falsely high or falsely low reading will occur when hemoglobin binds to something other than oxygen, as stated below :
- Hemoglobin has a higher affinity to carbon monoxide than it does to oxygen, and a high reading may occur despite the patient’s actually being hypoxemic. In case of carbon monoxide poisoning, this inaccuracy may delay the recognition of hypoxia.
- Cyanide poisoning gives a high reading, because it reduces oxygen extraction from arterial blood. In this case, the reading is not false, since arterial blood oxygen is indeed high in early cyanide poisoning.
- COPD, especially chronic bronchitis, may cause false readings.
What features set this work apart from similar achievements?
Although a number of oximeters were put on the market in the 1940s through the 1960s, any technology to realize today’s pulse oximetry was difficult to implement because of unstable photocells and light sources. In 1964 the first absolute reading ear oximeter was assembled, using eight wavelengths of light .
On the other hand, numbers of 'pulse oximeters' developed successively since the invention in 1972 have realized the following precious features:
(1) The 'pulse oximeters' are widely used for monitoring noninvasively the oxygen saturation of a patient’s blood and changes in blood volume in the skin [1-5].
(2) Owing to the capability to provide continuous and immediate oxygen saturation values, 'pulse oximeters' are essential to emergency medicine, and are also very useful for patients with respiratory or cardiac problems as well as for diagnosis of sleep disorders such as apnea and hypopnea .
(3) Portable battery-operated pulse oximeters offer health benefits to numbers of people, especially pilots, mountain climbers, and athletes. Some portable pulse oximeters employ software that charts a person's blood oxygen and pulse, serving as a reminder to check blood oxygen levels [1-3].
(4) With the use of the connectivity advancements of pulse oximeters, patients can have their own blood oxygen saturation continuously monitored without a cabled connection to a hospital monitor .
(5) A typical 'pulse oximeter' uses an electronic processor and a pair of small LEDs facing a photodiode through a translucent part of the patient's body, usually a fingertip or an earlobe, where it should added that one LED is red with wavelength of 660 nm, and the other infrared with wavelength of 940 nm.
Supporting texts and citations to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or chapters in scholarly books. 'Scholarly' is defined as peer-reviewed, with references, and published. You must supply the texts or excerpts themselves, not just the references. At least one of the references must be from a scholarly book or journal article. All supporting materials must be in English, or accompanied by an English translation.
 J. W. Severinghaus and Y. Honda, “History of blood gas analysis. VII. Pulse oximetry”, J. Clinical Monitoring, vol. 3, pp. 135-138, 1987.
 "Pulse oximetry": https://en.wikipedia.org/wiki/Pulse_oximetry.
 K. Miyasaka, et al., “Tribute to Dr. Takuo Aoyagi, inventor of pulse oximetry”, J. Anesthesia, vol. 35, pp. 671-709, 2021.
 T. Aoyagi and M. Kishi, “Optical device for measuring arterial oxygen saturation”, Japan Patent, 53-26437, 1978. (in Japanese).
 "Mr. Takuo Aoyagi and the pulse oximeter": http://www.nihonkohden.co.jp/information/aoyaggi/. (in Japanese).
References  and  were written in Japanese, for which English abstracts are provided in what follows.
① Reference : This article describes the patent gazette of Japan Patent 53-26437 on the 'Pulse Oximeter' invented by Takuo Aoyagi and Michio Kishi at Nihon Kohden Corporation (Tokyo. Japan), which was applied on March 29, 1974, and obtained on October 9, 1975. This patent gazette claims the extent and distinctive features of invented technologies.
② Reference : This article outlines Dr. Aoyagi's great achievement of inventing pulse oximetry, featuring (i) the principle of pulse oximetry, (ii) the process of inventing pulse oximetry, (iii) the first product 'Ear Oximeter OLV-5100' put on sale in 1975 by Nihon Kohden Corporation, (iv) the diffusion process of pulse oximeters, (v) Dr. Aoyagi's short history, and (vi) the list of patents obtained by Dr. Aoyagi.
Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to firstname.lastname@example.org. Please see the Milestone Program Guidelines for more information.
Please email a jpeg or PDF a letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property, and a letter (or forwarded email) from the appropriate Section Chair supporting the Milestone application to email@example.com with the subject line "Attention: Milestone Administrator." Note that there are multiple texts of the letter depending on whether an IEEE organizational unit other than the section will be paying for the plaque(s).