A review of thousands of cases from the first years of the Covid-19 pandemic – using pulse oximeters – found levels of oxygen in the blood of darker-skinned Covid patients were routinely over-estimated, leading to delays in treatment and hospital readmissions, say researchers.
The review focused on the initial chaos of the coronavirus pandemic when patients overwhelmed hospitals, and blood-oxygen levels were a key factor – then – in deciding which patients got limited hospital beds and received treatment.
The researchers from Baylor College, Johns Hopkins University and HCA Healthcare reviewed the cases of about 24 500 patients whose blood-oxygen levels were first measured with a pulse oximeter via a fingertip, and whose blood was then drawn and tested to further examine those levels.
They, and other experts, suggested that the pulse oximeter readings via fingertip of people with darker skin pigment often showed flawed results.
The issue has already led to reviews by federal regulators, with some efforts under way to determine how to produce more accurate readings, reports The New York Times.
Readings influence patient care
Pulse oximeter readings are used routinely to help shape medical care for various illnesses, including heart failure, sleep apnoea and respiratory conditions. A normal reading for a healthy patient should be an oxygen saturation level in the blood of about 95% or higher. If the readings are falsely high, patients may look fine on paper – but may not get the level of care they need.
The patients in the latest study, published in JAMA Network Open, were the ones researchers would have expected to have fared the best: their doctors saw the need to take a more precise measure of their blood-oxygen levels. (The fingertip reading of most patients is never double-checked with a blood draw.)
Those with a fingertip pulse-oximeter reading of 94% or more but whose blood tests showed lower levels were deemed to have an unrecognised need for Covid therapy. Black patients were found to be nearly 50% more likely than white patients to have their condition undetected. Hispanic patients were 18% more likely than white patients to have an unrecognised need.
Patients with unrecognised needs, regardless of race, experienced delays of roughly an hour that translated into a 10% higher risk of delayed Covid treatment. They were also more than twice as likely to be readmitted to hospital.
The new study did not include patients whose oxygen levels might have mistakenly appeared normal via the pulse oximeter but had no follow-up blood test, and perhaps were sent home even though they might have been seriously ill.
“That’s the patient population we’re really truly concerned about,” said Dr Ashraf Fawzy, a study author and Johns Hopkins assistant professor and intensive care physician.
Flaws might mean greater disparities
The US Food and Drug Administration approves the type of fingertip pulse oximeter used in hospitals and sold by prescription. The agency issued a safety communication about the flaws in early 2021, and held a hearing, before an expert panel, with researchers outlining studies pointing to the role the device might have in deepening health disparities for patients with darker skin tone.
The agency approved those devices through its so-called 510(k) programme, which clears devices that are similar to existing ones — with some additional scrutiny. The programme has been criticised over the years because the standards for clearing devices are typically lower than those for the agency’s approval of new drugs.
During the hearing in November, the FDA noted that the pulse oximeters sold over the counter are subject to even less oversight, prompting agency advisers to call for warnings to consumers who use the devices to gauge their own respiratory health.
Further review promised
The FDA said last week it planned to publish a discussion paper for feedback on the issue and convene another meeting with experts to discuss potential approaches.
“It is a high priority to ensure oximetry device performance is equitable and accurate for all patients,” the agency said in a statement.
Some work has also begun to design a better pulse oximeter.
For now, though, Fawzy said doctors should trust their overall impression of a patient’s condition when considering a pulse-oximeter reading.
“It’s important to recognise this device may lead to inaccurate clinical decisions,” he said, “or that we may be under-treating certain people or under-recognising their needs.”
Study details
Clinical outcomes associated with overestimation of oxygen saturation by pulse oximetry in patients with Covid-19
Ashraf Fawzy, Tianshi David Wu, Kunbo Wang, et al
Published in JAMA Network Open on 24 August 2023
Abstract
Importance
Many pulse oximeters have been shown to overestimate oxygen saturation in persons of colour, and this phenomenon has potential clinical implications. The relationship between overestimation of oxygen saturation with timing of Covid-19 medication delivery and clinical outcomes remains unknown.
Objective
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.
Design, Setting, and Participants
This cohort study included patients hospitalised for Covid-19 at 186 acute care facilities in the US with at least one functional arterial oxygen saturation (SaO2) measurement between March 2020 and October 2021. A subset of patients were 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).
Exposures
Self-reported race and ethnicity, difference between concurrent SaO2 and pulse oximeter saturation (SpO2) within 10 minutes, and initially unrecognised need for Covid-19 therapy (first SaO2 reading below 94% despite SpO2 levels of 94% or above).
Main Outcome and Measures
The association of race and ethnicity with degree of pulse oximeter measurement error (SpO2 − SaO2) and odds of unrecognised need for Covid-19 therapy were determined using linear mixed-effects models. Associations of initially unrecognised need for treatment with time to receipt of therapy (remdesivir or dexamethasone), in-hospital mortality, 30-day hospital readmission, and length of stay were evaluated using mixed-effects models. All models accounted for demographics, clinical characteristics, and hospital site. Effect modification by race and ethnicity was evaluated using interaction terms.
Results
Among 24 504 patients with concurrent SpO2 and SaO2 measurements (mean [SD] age, 63.9 [15.8] years; 10 263 female [41.9%]; 3922 black [16.0%], 7 895 Hispanic [32.2%], 2 554 Asian, Native American or Alaskan Native, Hawaiian or Pacific Islander, or another race or ethnicity [10.4%], and 10 133 white [41.4%]), 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 8635 patients with a concurrent SpO2 − SaO2 pair without immediate need for Covid-19 therapy, Black patients were significantly more likely to have pulse oximetry values that masked an indication for Covid-19 therapy compared with white patients (adjusted odds ratio [aOR], 1.65; 95% CI, 1.33-2.03).
Patients with an unrecognised 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 unrecognised 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).
Conclusions and Relevance
In this cohort study, overestimation of oxygen saturation by pulse oximetry led to delayed delivery of Covid-19 therapy and higher probability of readmission regardless of race. Black patients were more likely to have unrecognised need for therapy with potential implications for population-level health disparities.
See more from MedicalBrief archives:
Race versus skin tone debate in resolving pulse oximeters' false readings
Pulse oximeters deliver unreliable readings across ethnic groups
UK investigation into racial and gender bias in medical devices
Pulse oximetry accuracy varies between race groups – US cohort study