Two engineers have developed medical procedures and devices that have revolutionized health care. Their contributions are being honored next month at the IEEE Honors Ceremony in New York City.
IEEE Member Takuo Aoyagi is behind the fundamental principles of pulse oximetry, a procedure used to measure the oxygen level and oxygen saturation in the blood. The senior manager at Nihon Kohden Corp., in Tokyo, will be honored with this year’s IEEE Medal for Innovations in Healthcare Technology.
While investigating a noninvasive cardiac output device in 1972, Aoyagi discovered that a noise interfering with the accurate dye dilution curve contained important information about the oxygenation of blood in a person’s arteries. (A dye dilution curve is a graph of the concentrations of Evans Blue, a natural dye found in blood, as it is pumped into and away from the heart.)
Based on this discovery, he invented the first pulse oximeter in 1975. Consisting of a probe containing a light-emitting device and two photodetectors, Aoyagi’s device is clamped on to a thin part of a person’s body—usually a fingertip or earlobe. The oximeter passes two wavelengths of light through the body part to a photodetector on the other side. It measures the changing absorbance at each of the wavelengths, allowing the device to determine the absorbencies due to the blood pulsing through the arteries. The oximeter rapidly and noninvasively assesses blood and respiratory problems in patients and allows clinicians to detect heart abnormalities.
All of today’s oximeters are based on Aoyagi’s principles of pulse oximetry. Pulse oximetry is now considered the standard of care for patients undergoing anesthesia and for those being treated in emergency rooms, intensive care units, and at home. In 2007, the World Health Organization included pulse oximetry as an essential component of its Surgical Safety Checklist for reducing complications.
IEEE Fellow Chris Toumazou has developed silicon microchips and integrated circuits for a number of medical devices, including cochlear implants and wireless heart monitors. The professor of biomedical engineering and director of the Center for Bio-Inspired Technology at Imperial College, in London, will receive this year’s IEEE Biomedical Engineering Award.
In 1994, at age 33, Toumazou was the youngest professor to be appointed at Imperial. There, he has designed components for children’s cochlear implants, an artificial pancreas for people with Type 1 diabetes, and a wireless heart monitor for patients who have recently undergone surgery.
More recently, Toumazou developed the SNP-DR, a portable low-powered device that uses silicon microchips to identify genetic mutations that determine a person’s predisposition to certain hereditary diseases. Rather than sending DNA specimens to a laboratory, doctors can use the SNP-DR to generate test results on site.