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Overestimation of Oxygen Saturation Delayed COVID-19 Care Across Races

Pulse oximetry, which noninvasively estimates arterial oxygen saturation, was first developed in the 1970s and became especially important during the COVID-19 pandemic when oxygen saturation thresholds were used to define disease severity. Find out what a new study found out about the significant downsides of relying on pulse oximetry.

BALTIMORE, MD – COVID-19 treatment was delayed and hospital readmissions were more likely to increase because of the overestimation of oxygen saturation by pulse oximetry in patients, according to a new study.

The report in JAMA Network Open suggests that Black patients were more likely to have an unrecognized need for therapy and that led to possible population-level health disparities.

The new cohort study, led by Johns Hopkins University School of Medicine researchers, involved 24 504 patients with concurrently measured pulse oximetry and arterial oxygen saturation. It found that pulse oximeters more commonly overestimated arterial oxygen saturation in patients from minority racial and ethnic groups and led to delayed recognition of the need for COVID-19 therapy among Black patients compared with white patients.

Focusing on a subset of 8,635 patients without immediate need for therapy on admission, “overestimation of oxygen saturation by pulse oximetry was associated with delayed delivery of COVID-19 therapy and increased risk of hospital readmission, irrespective of patient race,” the study pointed out.

The study team advised that its results confirm the possibility of racial and ethnic disparities in the measurement of oxygen saturation by pulse oximetry, the risk of hospital admission is increased regardless of patient race.

“Many pulse oximeters have been shown to overestimate oxygen saturation in persons of color, and this phenomenon has potential clinical implications,” the study team noted, adding that the relationship between overestimation of oxygen saturation with the timing of COVID-19 medication delivery and clinical outcomes had been unclear.

That’s why the investigators sought to investigate the association between overestimation of oxygen saturation by pulse oximetry and delay in administration of COVID-19 therapy, hospital length of stay, risk of hospital readmission, and in-hospital mortality.

Participants were hospitalized for COVID-19 at 186 acute care facilities in the United States All had at least 1 functional arterial oxygen saturation (SaO₂) measurement between March 2020 and October 2021.

In addition, a subset of patients was admitted after July 1, 2020, without immediate need for COVID-19 therapy based on pulse oximeter saturation (SpO₂ levels of 94% or higher without supplemental oxygen).

The focus was on self-reported race and ethnicity, the difference between concurrent SaO₂ and pulse oximeter saturation (SpO₂) within 10 minutes, and the initially unrecognized need for COVID-19 therapy (first SaO₂ reading below 94% despite SpO₂ levels of 94% or above).

Patients included in the age had a median age of 63.9 and were 41.9% female. The greatest percentage was white, 41.1%, followed by Hispanic, 32.2%, and Black, 16%, with 10.4% being Asian, Native American or Alaskan Native, Hawaiian or Pacific Islander, or another race or ethnicity.

The study reported that “pulse oximetry overestimated SaO₂ for Black (adjusted mean difference, 0.93 [95% CI, 0.74-1.12] percentage points), Hispanic (0.49 [95% CI, 0.34-0.63] percentage points), and other (0.53 [95% CI, 0.35-0.72] percentage points) patients compared with White patients. In a subset of 8,635 patients with a concurrent SpO₂ − SaO₂ pair without immediate need for COVID-19 therapy,”

Black patients were much more likely to have pulse oximetry values that “masked’ any indication to receive COVID-19 therapy compared with White patients (adjusted odds ratio [aOR], 1.65; 95% CI, 1.33-2.03), the researchers pointed out, adding, “Patients with an unrecognized need for COVID-19 therapy were 10% less likely to receive COVID-19 therapy (adjusted hazard ratio, 0.90; 95% CI, 0.83-0.97) and higher odds of readmission (aOR, 2.41; 95% CI, 1.39-4.18) regardless of race (P for interaction = .45 and P = .14, respectively). There was no association of unrecognized need for COVID-19 therapy with in-hospital mortality (aOR, 0.84; 95% CI, 0.71-1.01) or length of stay (mean difference, −1.4 days; 95% CI, −3.1 to 0.2 days).”

Background information in the article recounted how pulse oximetry, which noninvasively estimates arterial oxygen saturation, was first developed in the 1970s and now has become ubiquitous in healthcare settings and influences clinical decision-making.

^“During the COVID-19 pandemic, oxygen saturation thresholds were used to define disease severity, making the pulse oximeter particularly important for triage and treatment decisions,” the authors write.

Observational data and laboratory studies suggest, however, that pulse oximeters “systematically overestimate arterial oxygen saturation among patients from minority racial and ethnic groups, leading to a greater risk of occult hypoxemia, generally defined as a true arterial oxygen saturation (SaO₂) below 88% with an oxygen saturation by pulse oximetry (SpO₂) in a normal range above 92%. The presence of occult hypoxemia has been associated with lower rates of supplemental oxygen among critically ill patients.”