The pulse oximeter is a device that continuously measures the oxygen saturation in arterial blood (how much haemoglobin is bound to oxygen) without blood sampling.
Hemoglobin turns bright red when bound to oxygen, and dark red when unbound. The oxygen saturation of arterial blood is calculated by utilizing the fact that the ease of absorbing light differs depending on the colour. Two types of light with different wavelengths are emitted from one of the small devices attached to the fingertips of the hand, and the sensor on the other side measures the light that passes through the finger without being absorbed and analyzes it.
It can be fatal if there is not enough oxygen in the blood. Blood sampling does not always provide accurate, real-time information about the patient's condition, which changes over time, but using a pulse oximeter does not hurt the patient, and allows the surgeon to understand in real-time, how much oxygen the patient has in their bloodstream.
After graduating from the Faculty of Engineering, Niigata University, Mr. Aoyagi joined the company in 1971 after working for Shimadzu Corporation (Kyoto). One of Mr. Aoyagi's beliefs at the time when he began searching for specific research themes in the development department was, "The ultimate form of patient monitoring is the automation of treatment. To get closer to that ideal, the development of non-invasive continuous monitoring technology is important. "
In 1972, while improving the equipment for measuring arterial blood pumped from the heart, we discovered that the oxygen saturation of arterial blood can be measured by using the pulse of the heart.
Mr. Aoyagi later commented on this finding, "It was hard to believe that such a good discovery was waiting for us in such a convenient place."
Mr. Aoyagi, who continued his research, working on the development of prototype devices, presented this principle at a conference in 1974. There were some opinions that "I think it was an interesting study," but there were some negative opinions, so this presentation did not receive much attention.
The following year, in 1975, we launched the "Oximeter OLV-5100", which uses this principle. It was a truly unique and world-class product, but there was still room for improvement in terms of performance and usability, such as the light source being a miniature bulb and the fact that the sensitivity of the sensor was poor, and demand for the product never really materialized. For these and other reasons development of the pulse oximeter was eventually suspended. The 10 years after we stopped developing the pulse oximeter, saw a great deal of movement in the medical world. With the frequent occurrence of medical accidents in the United States where patients under anesthesia for surgery lose their lives due to lack of oxygen, the usefulness of pulse oximeters came to the forefront of global attention. With many companies competing to launch smaller devices incorporating new technologies such as LEDs, photodiodes, and microcomputers, pulse oximeters became very popular. This movement spread to the domestic market in the latter half of the 1980s, and we also resumed the research and development of the pulse oximeter utilizing the know-how gained during the development of the OLV-5100 and released a new product in 1988. At the time of the development of this product, there was debate over whether to manufacture it in-house, but Mr. Aoyagi said, "Currently, a single device is the mainstream, but in the future it will be essential to incorporate it into a biological information monitoring device. You should make your own products so that there are no restrictions on what you can do with them.
As expected by Aoyagi, the arterial oxygen saturation (SpO2) is a standard parameter for most of today's biological information monitoring devices.
Mr. Aoyagi did not announce the principle of the pulse oximeter in English, but Dr. Severinghaus, a world authority on respiratory physiology who knew Mr. Aoyagi's existence, visited Japan in 1987 and met Mr. Aoyagi. After that, after being introduced in the paper, Aoyagi became known worldwide as the inventor of the pulse oximeter.

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