Pulse oximetry: the story behind the finger clip that shows the impact of innovation

If you have ever been triaged in an emergency room or had an operation at the hospital, you will likely have come across a pulse oximeter.

It is a clothespin-like device with a bright red ray that beeps when clipped to a patient’s finger. This device provides health care providers with crucial information about how much oxygen is being carried in the blood — a value known as oxygen saturation. In the COVID-19 pandemic, pulse oximeters have become especially relevant in helping doctors stratify which patients have dangerously low levels of oxygen. It is the standard to determine if patients need oxygen supplementation and when more serious interventions, like intubation and ventilation, is needed.

Today, pulse oximetry is as vital to know as heart rate and blood pressure.

It will come as a surprise to many, including those in the health care field, that the tool used to measure oxygen in the blood was only invented in the 1970s and did not become commercially available until the 1980s. By the 1990s there was still ongoing controversy about the relevance of oximetry in patient care. Today, it is a mandatory checkpoint in triage and often the first monitor on the patient and the last monitor off in the operating room. The widespread availability of oximeters has shaped many of the guidelines that doctors use to decide when to treat certain medical conditions.

The technology behind pulse oximetry was developed in 1972. A Japanese bioengineer named Takuo Aoyagi invented a device that used red and infrared light to measure oxygen in the blood. Infrared light is more easily absorbed by oxygenated hemoglobin and red light is more easily absorbed by deoxygenated hemoglobin. Aoyagi’s patented technology was mainly reserved for pulmonary function labs and research. At the time, the versatility of Aoyagi’s innovation had yet to be cultivated.

It was not until 1978, when Dr. William New, an anesthesiologist at Stanford University popularized oximetry by demonstrating its relevance in the care of patients undergoing anesthesia and those who were severely oxygen deprived. By translating laboratory innovations into clinical care, Dr. New became the catalyst in the expansion of pulse oximetry to redefine the standard of care in almost all medical settings.

Dr. New’s influence was especially relevant in anesthesia and critical care. For 130 years before oximetry, the surgical team monitored anesthetized patients by assessing if the unconscious patient looked “particularly blue.” However this observation often comes too late. During the 1970s, more patients during anesthesia died from undetected oxygenation disturbances than all other causes combined. By the time a patient becomes visibly blue, their oxygen saturation is likely below 85 per cent. That patient would require urgent intervention in the next three to five minutes, offering little time for investigation into the root cause of crisis.

Dr. New wrote an academic article stressing the “poor reliability of (turning blue) as an indicator of inadequate oxygenation” and the advantages of a non-invasive monitor to determine oxygen saturation. He described how pulse oximeters offer a continuous and accurate reading. As an entrepreneur, Dr. New recognized the market potential of monitoring oxygen saturation and co-founded Nellcor to commercially produce pulse oximeters in the 1980s. Nellcor remains one of the top manufacturers of pulse oximeters, in a market that will balloon to a value of $2.8 billion (U.S.) by 2025.

Across the world, tens of thousands of operating rooms are missing this life saving device. Pulse oximetry is often described as the minimum standard for safe anesthesia and surviving surgery. Limited access in low-resource health care systems put millions of lives at risk. Lifebox is a nonprofit organization that has delivered pulse oximeters to more than 20,000 hospitals across 100 countries. You can find more information about Lifebox at lifebox.org/about-us.

The story of pulse oximetry shows the tremendous impact of innovation and entrepreneurship to bring a discovery from the lab to the clinic.

Over the past 50 years, pulse oximetry has transformed patient monitoring in all medical settings, especially in contemporary perioperative and critical care. In its infancy, pulse oximetry was an alarm that allowed us to identify patients in urgent need of medical intervention. However, its widespread adoption has led to an entire school of thought around when and how much oxygen is needed for patients. This wealth of information has improved the ability of health care professionals to plan interventions and reduce complications.