Pulse Oximetry: A breath-taking historical view

As an anesthesiologist, my job is to keep patients alive and safe from surgical harm. The product I rely on most is a medical device called the pulse oximeter. This simple device clips onto a patient’s finger and measures the saturation of oxygen molecules bound to a patent’s hemoglobin, the protein responsible for carrying oxygen to bodily tissues and sustaining life. Today, it is easy to take this device for granted. After all, you can purchase a pulse oximeter on Amazon for less than $20. Yet the advent of the pulse oximeter in the late 1970s was a large reason why anesthesia-mortality risk has declined from about 1 death in 1000 surgical procedures in the 1940s to 1 in 10,000 in the 1970s and to 1 in 100,000 in the 1990s and early 2000s.

Why is this device so wonderful? Besides solving a critical unmet need (prior to pulse oximetry, anesthesiologists put their finger on a patient’s pulse and watched to see if the patient’s lips turned blue to see if they were asphyxiating), pulse oximetry is the epitome of the simplifying innovation. It converts a complex physiologic process (i.e. the differential absorption of light from the binding of oxygen and carbon dioxide to hemoglobin in pulsatile blood) into a simple percentage which is expressed both visually (numeric display) and aurally (a soothing beeping noise whose pitch varies based on the percentage saturation and rate varies based on the heart rate). It is used widely across almost all medical care settings from operating room to emergency room to doctor’s office to measure vital signs.

Pulse oximetry owes its origins to the anesthesiologists William New and Mark Yelderman of Stanford University Medical School. New recognized the potential importance of and market for a convenient, accurate oximeter in the operating room and all other hospital and clinic sites where patients are sedated, anesthetized, unconscious, comatose, paralyzed, or in some way limited in their ability to regulate their own oxygen supply. New, with engineer Jack Lloyd, founded Nellcor, which began the mass manufacture of the Nellcor pulse oximeters. The Nellcor pulse oximeter was evaluated by Yelderman and New, the manufacturers in 1983 [2. M. Yelderman and W. New, Jr., Evaluation of pulse-oximetry. Anesthesiology 59 (1983), pp. 349–352. View Record in Scopus | Cited By in Scopus (77)2].

After an initial period of skepticism, the Association of Anaesthetists of Great Britain and Ireland recognized the pulse oximeter as their standard for intraoperative monitoring in 1988, and 2 years later, the American Society of Anesthesiologists recognized it as their standard for intraoperative monitoring.

By 1993, there were about 40 companies making and selling pulse oximeters, and over 750 books, reviews, and papers concerning pulse oximetry were published. Nellcor was founded in 1981 and sold to Mallinckrodt (now Covidien) in 1995 for $2 billion.

The pulse oximeter revolutionized patient care in the operating room and in doing so, generated breath-taking clinical and commercial success.

Ellison Pierce and Bill New – who had more impact?

Up to the 1960s and 1980s, Anesthesia deaths occurred 1/10,000 procedures. In 1972, Jeffrey Cooper observed anesthesiologists and observed lack of standardization in the machine which administered anesthetics and then using critical incident analysis studied 359 different errors and published a paper known as “Prevent Anesthesia Mishaps: A study of human factors” in 1978. It took until 1982 when Ellison Piece was elected VP of the ASA that he established a committee on patient safety and in collaboration with Cooper persuaded the FDA to produced a checklist and patient safety videos to be distributed through pharma companies and then started an ongoing international symposium on anesthesia patient safety. He then established the Anesthesia Patient Safety Foundation with a newsletter, funds and channeling grants for use in patient safety research.

This led to redesign of machines, monitoring devices and dropping error rates with 139 papers published by 1995. This launched the field of Patient Safety and anesthesia-related errors had dropped to 1/200,000 cases.

It is very interesting to couple this development with a fairly concurrent development in the traditional entrepreneur model in the development of the pulse oximeter by Bill New

The following is excerpted from an article by Pole, Y. “Evolution of the pulse oximeter” International Congress Series 1242 (2002) 137– 144

Credit for the present enormous interest in pulse oximetry belongs to the anesthesiologists William New and Mark Yelderman of Stanford University Medical School. New recognized the potential importance of and market for a convenient, accurate oximeter in the operating room and all other hospital and clinic sites where patients are sedated, anesthetized, unconscious, comatose, paralyzed, or in some way limited in their ability to regulate their own O₂ supply. New, with engineer Jack Lloyd, founded Nellcor, which began the mass manufacture of the Nellcor pulse oximeters. The Nellcor pulse oximeter was evaluated by Yelderman and New, the manufacturers in 1983 [2. M. Yelderman and W. New, Jr., Evaluation of pulse-oximetry. Anesthesiology 59 (1983), pp. 349–352. View Record in Scopus | Cited By in Scopus (77)2].

After an initial period of scepticism, as of 1988, the Association of Anaesthetists of Great Britain and Ireland recognized the pulse oximeter as their standard for intraoperative monitoring, and 2 years later, as of 1990, the American Society of Anesthesiologists recognized it as their standard for intraoperative monitoring.

By 1993, there were about 40 companies making and selling pulse oximeters, and over 750 books, reviews, and papers concerning pulse oximetry were published. Nellcor was founded in 1981 and sold in 1995 for $2 billion.

Which of these is a more powerful impact for the social good? According to a meta-analysis by the Agency for Healthcare Research and Quality which monitors healthcare quality, the available studies do not automatically attribute an improvement in outcomes to better monitoring. In fact, in a multicenter, randomized, controlled trial of 20,802 surgical patients, Moller et al studied the impact of perioperative pulse oximetry on patient outcome. Despite the large sample, the authors were unable to show a difference in in-hospital mortality or postoperative complications. During anesthesia and in the post-anesthesia care unit (PACU), more episodes of hypoxemia and myocardial ischemia were detected in patients monitored with pulse oximetry.

http://www.ahrq.gov/clinic/ptsafety/chap24.htm

Moller JT, Johannessen NW, Espersen K, Ravlo O, Pedersen BD, Jensen PF, et al. Randomized evaluation of pulse oximetry in 20,802 patients: II. Perioperative events and postoperative complications. Anesthesiology 1993;78:445-453.

Rowland Hill

This man invented pre-paid stamps

In 1840, Hill noticed postal revenues failed to increase despite growth in the economy and analyzed the cost structure of mail delivery 12 cents a letter which was too high for everyone. He found that the majority of the costs were due to time for clerks to appraise how to price the mail by weight. The actual conveyance costs were a fraction of this price. He simplified the process by charging a uniform prepaid “Penny post” price which led to annual mail delivery to rise from 76-642 million letters over the next 25 years.