OAKLAND, Calif. \u2014 The patient was in his 60s, an African American man with emphysema. The oximeter placed on his fingertip registered well above the 88% blood oxygen saturation level that signals an urgent risk of organ failure and death.<\/p>\n
Yet his doctor, Noha Aboelata, believed the patient was sicker than the device showed. So she sent him for a lab test, which confirmed her suspicion that he needed supplemental oxygen at home.<\/p>\n
Months later, in December 2020, Aboelata thought back to her patient as she read a New England Journal of Medicine article showing that pulse oximeters were three times as likely<\/a> to miss dangerously low blood oxygen levels in Black patients as in white ones. At a time when Black Americans were dying of covid at high rates and hospitals struggled to find beds and oxygen for those needing them, the finding exposed one of the most blatant examples of institutional racism in American health care.<\/p>\n \u201cI was like, \u2018Were there other patients I missed?\u201d said Aboelata, a family physician and the CEO of Oakland-based Roots Community Health. As she shared the article with colleagues, \u201cthere was so much anger and frustration because we had every reason to believe we could rely on this device, and it was systematically not working in the population that we served.\u201d<\/p>\n State attorneys general<\/a> and U.S. senators<\/a> have pressed the FDA to take steps to eliminate pulse oximetry\u2019s racial bias, which has caused delays in treatment and worse health outcomes, and more recently has raised concern about the reliability of hospital AI tools<\/a> that draw on reams of data from the devices.<\/p>\n Aboelata\u2019s clinic has sued producers and stores that sell oximeters, demanding they pull the devices or add safety warnings to the labels. Many of her patients rely on home oxygen, which requires accurate readings for Medicare to cover.<\/p>\n But getting rid of the devices, central to care for heart and lung diseases, sleep apnea, and other conditions, isn\u2019t an option.<\/p>\n Since the 1990s, the convenient fingertip clamps have come to stand in for many uses of arterial blood gas readings, which are the gold standard for determining oxygen levels but dangerous if not done carefully. Makers of oximeters will sell around $3 billion<\/a> of them this year because they are used in nearly every hospital, clinic, and long-term care facility. During the pandemic, hundreds of thousands of Americans bought them for home use.<\/p>\n One of them was Walter Wilson, a 70-year-old businessman in San Jose who has had two kidney transplants since 2000. Wilson contracted covid last December but delayed visiting a doctor because his home pulse oximetry readings were in the normal range.<\/p>\n \u201cI\u2019m a dark-complected Black guy. I was very sick. Had the oximeter picked that up I would have gotten to the hospital sooner,\u201d he said.<\/p>\n Wilson ended up back on dialysis after several years of good health. Now he\u2019s looking to join a class action lawsuit against the device manufacturers.<\/p>\n \u201cThey\u2019ve known for years that people with darker skin get bad readings,\u201d he said, \u201cbut they tested them on healthy white people.\u201d<\/p>\n After years of little action on the issue, the FDA in 2021 sent a safety warning<\/a> to doctors about oximeters. It has also funded research to improve the devices and promised to issue new guidelines for how to make them.<\/p>\n But as the FDA polishes draft guidelines it had hoped to publish by Oct. 1, clinicians and scientists are unsure what to expect. The agency has indicated it will recommend that manufacturers test new oximeters on more people, including a large percentage with dark-pigmented skin.<\/p>\n Because of industry pushback, however, the guidance isn\u2019t expected to ask device makers to test oximeters under real-world conditions, said Michael Lipnick, a University of California-San Francisco anesthesiologist and researcher.<\/p>\n Hospitalized people are often dehydrated, with restricted blood flow to their extremities. This condition, known as low perfusion \u2014 essentially, poor circulation \u2014 is particularly common with cardiovascular disease, which is more prevalent in Black patients.<\/p>\n Pigmentation and poor perfusion \u201cwork together to degrade pulse oximetry performance,\u201d said Philip Bickler, who directs the Hypoxia Research Lab at UCSF. \u201cDuring covid, Black patients showed up sicker because of all the barriers those patients face in accessing health care. They\u2019re showing up on death\u2019s door, and their perfusion is lower.\u201d<\/p>\n The FDA guidance isn\u2019t expected to require manufacturers to measure how well their devices perform in patients with poor perfusion. All this means that the FDA\u2019s efforts could lead to devices that work in healthy dark-skinned adults but do \u201cnot fix the problem,\u201d said Hugh Cassiere, who chairs a panel for the FDA\u2019s Medical Devices Advisory Committee, at its February meeting.<\/p>\n A History of Inaction<\/strong><\/p>\n Although some recent industry-sponsored studies have shown that certain devices work across skin tones, research dating to the 1980s has found discrepancies in pulse oximetry. In 2005, Bickler and other scientists at the Hypoxia Lab published evidence that three leading devices consistently failed to detect hypoxemia in darkly pigmented patients \u2014 especially those who were severely oxygen-depleted. Noting that these readings could be crucial to directing treatment, the authors called for oximeters to carry warnings.<\/p>\n The FDA\u2019s response was modest. Its regulatory pathway for pulse oximeters clears them for sale as long as they show \u201csubstantial equivalence\u201d to devices already on the market. In a 2007 draft guidance document, the FDA suggested that tests of new oximeters could \u201cinclude a sufficient number of subjects with dark skin pigmentation, e.g., 30%.\u201d However, the final guidance, issued in 2013, recommended \u201cat least 2 darkly pigmented subjects or 15% of your subject pool, whichever is larger.\u201d The studies were required to have only 10 subjects. And the agency did not define \u201cdark-pigmented.\u201d<\/p>\n Testing the devices involves fitting patients with masks that control the gases they breathe, while simultaneously taking pulse oximetry readings and samples of arterial blood that are fed into a highly accurate measuring device, invented by the Hypoxia Lab\u2019s late founder, John Severinghaus.<\/p>\n Bickler, who evinces the bemused skepticism of a seasoned car mechanic when discussing the scores of devices his lab has tested, said \u201cyou can\u2019t always trust what the manufacturers say.\u201d<\/p>\n Their data, he said, ranges from \u201ccompletely inaccurate\u201d to \u201cobtained under absolutely ideal conditions, nothing like a real-world performance.\u201d<\/p>\n During the pandemic, a medical charity approached the lab about donating thousands of oximeters to poor countries. The oximeters it had chosen \u201cweren\u2019t very good,\u201d he said. After that, the lab set up its own ratings page<\/a>, a kind of Consumer Reports for pulse oximeters.<\/p>\n According to its tests, some expensive devices don\u2019t work; a few of the $35 gadgets are more effective than competitors costing $350. Over a third of the marketed devices the lab has tested don\u2019t meet current FDA standards, according to the site.<\/p>\n To investigate whether real-world tests of oximeters are feasible, the FDA funded a UCSF study that has recruited about 200 intensive care unit patients. The data from the study is being prepared to undergo peer review for publication, Bickler said.<\/p>\n He said the lab did not warm the hands of patients in the study, which is the customary practice of manufacturers when they test their devices. Warming assures better circulation in the finger the device is attached to.<\/p>\n \u201cIt affects the signal-to-noise ratio,\u201d Bickler said. \u201cRemember when car radios had AM stations, and you\u2019d get a lot of static? That\u2019s what poor perfusion does \u2014 it causes noise, or static that can obscure a clear signal from the device.\u201d<\/p>\n Hypoxia Lab scientists \u2014 and doctors in the real world \u2014 don\u2019t warm patients\u2019 hands. But \u201cthe industry people can\u2019t agree on how to handle it,\u201d he said.<\/p>\n Masimo, a company that says it has the most accurate pulse oximeters<\/a> on the market, would happily comply with any FDA guidance, Daniel Cantillon, Masimo\u2019s chief medical officer, said in an interview.<\/p>\n How Much To Fix the Problem?<\/strong><\/p>\n The very best devices, according to the Hypoxia Lab, cost $6,000 or more<\/a>. That points to another problem.<\/p>\n With better accuracy, \u201cyou are going to reduce patient access to devices for a large proportion of the world that simply can\u2019t afford them,\u201d Lipnick said.<\/p>\n Even if the FDA can\u2019t please everyone, its anticipated call for more people with darker skin in oximetry tests will \u201cassure there\u2019s real diversity in the development and testing of those devices before they come to market,\u201d Lipnick said. \u201cThat bar has been too low for decades.\u201d<\/p>\n It is difficult to assess harm to individuals from faulty oximeter readings, because these errors are often one factor in a chain of events. But studies at Johns Hopkins University<\/a> and elsewhere indicated that patients whose oxygen depletion wasn\u2019t noticed \u2014 possibly thousands of them \u2014 had delayed treatment and worse outcomes.<\/p>\n Already, Aboelata said, a few manufacturers \u2014 Zewa Medical Technology, Veridian Healthcare, and Gurin Products \u2014 have responded to the Roots Community Health lawsuit by including warnings about their devices\u2019 limitations.<\/p>\n There\u2019s not much she and other clinicians can do in daily practice, she said, other than establish a baseline reading with each new patient and be on the lookout for notable drops. Hospitals have other tools to check oxygen levels, but correct readings are critical for outpatient care, she said. In 2022, Connecticut enacted a law banning insurers from denying home oxygen or other services based solely on pulse oximetry readings.<\/p>\n But \u201cadapting around the crappy device isn\u2019t the solution,\u201d said Theodore Iwashyna, the Johns Hopkins Bloomberg School of Public Health professor who co-authored the New England Journal of Medicine article. \u201cA less crappy device is the solution.\u201d<\/p>\n KFF Health News<\/a> is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF\u2014an independent source of health policy research, polling, and journalism. Learn more about KFF<\/a>.<\/p>\nUSE OUR CONTENT<\/h3>\n