Tribute to Dr. Takuo Aoyagi, inventor of pulse oximetry

Abstract

Introduction Dr. Takuo Aoyagi invented pulse oximetry in 1974. Pulse oximeters are widely used worldwide, most recently making headlines during the COVID-19 pandemic. Dr. Aoyagi passed away on April 18, 2020, aware of the significance of his invention, but still actively searching for the theory that would take his invention to new heights. Method Many people who knew Dr. Aoyagi, or knew of him and his invention, agreed to participate in this tribute to his work. The authors, from Japan and around the world, represent all aspects of the development of medical devices, including scientists and engineers, clinicians, academics, business people, and clinical practitioners. Results While the idea of pulse oximetry originated in Japan, device development lagged in Japan due to a lack of business, clinical, and academic interest. Awareness of the importance of anesthesia safety in the US, due to academic foresight and media attention, in combination with excellence in technological innovation, led to widespread use of pulse oximetry around the world. Conclusion Dr. Aoyagi’s final wish was to find a theory of pulse oximetry. We hope this tribute to him and his invention will inspire a new generation of scientists, clinicians, and related organizations to secure the foundation of the theory.

Wearable Photoplethysmography for Cardiovascular Monitoring

“…It was not until almost half a century later, in the 1980s, that photoplethysmography entered widespread clinical use in the form of pulse oximeters [ 35 ]. Pulse oximeters have had a profound impact on clinical care, initially enabling continuous oxygen saturation monitoring during anesthesia, which had “almost never been done before” [ 36 ]. They are now used in a wide range of clinical settings [ 37 ].…”

Understanding pulse oximetry in hematology patients: Hemoglobinopathies, racial differences, and beyond

“…4 The original technology was measured in healthy adults, who were not selected to represent diverse ethnic backgrounds, and was found to have a correlation with arterial oxygen saturation within 2% of arterial oxygen saturation (SaO 2 ). 1,3,4 It was once said that it would be "impossible to standardize calibration using actual measurements on human beings who cannot be standardized". 3 In recent years, there has been renewed interest in understanding how pulse oximetry is applied to different populations, and where the limitations lie.…”

“…Pulse oximetry was built on principles identified by Dr. Aldrick B. Hertzman in the 1930s that light absorbance and reflection oscillates with cardiac output as the arterial blood volume fluctuates 2 . Dr. Takuo Aoyagi was a Japanese scientist who applied principles of the Beer–Lambert law to a model of in‐vivo dye distribution, ultimately using it to measure oxygenation after observing that arterial pulsations were interfering with his measurements 3 . In order to isolate the effects of these arterial pulsations, he compared differences in absorption between the two wavelengths of light by comparing the ratios of maximal difference in light absorption to the mean light transmission of each wavelength 4 .…”

Towards Real-Time Oxygen Sensing: From Nanomaterials to Plasma

“…The ongoing pandemic has generated an unprecedented demand for PoC devices for pulse oximetry. The basic principle of pulse oximetry has been developing since 1876, and it is one of the imperative life-saving innovations till date (von Vierordt (1876); Nicolai (1930); Tremper (1989); Miyasaka et al (2021)). From the war zone to the intensive care unit, pulse oximetry plays a vital role, and the situation remained unchanged during the COVID-19 pandemic to measure the oxygen saturation level in human blood (Greenhalgh et al (2021)).…”