Racial Disparities in Pulse Oximetry Persist; Sex Differences in COPD Treatment

NASHVILLE, Tenn. — Racial biases persist in the use of pulse oximetry devices for patients with acute hypoxemic respiratory failure (AHRF) requiring very high levels of oxygen support, a retrospective analysis suggested.

In comparing direct arterial blood gas readings versus pulse oximetry readings among patients at a single intensive care unit (ICU), Black patients had a significantly higher oxygen saturation (SpO2) average compared with white patients (97±4 vs 95±4; P=0.041), reported Julia Balmaceda, a medical student at the University of Kansas School of Medicine in Kansas City.

Meanwhile, results from an observational study showed few significant gender-based differences in the diagnosis and management of chronic obstructive pulmonary disease (COPD), said Amitha Avasarala, MD, of the Mercy Health Clinic in Pittsburgh.

Both studies were presented at CHEST 2022, the annual meeting of the American College of Chest Physicians.

Racial Disparities

In regression analysis of arterial oxygen saturation (SaO2), race was shown to be a significant predictor of SpO2 (P=0.019). SpO2 readings from Black patients overestimated oxygen saturation by 0.814% compared with readings taken from white patients, Balmaceda noted during her presentation.

In assessing clinical management of these patients, Black patients had a significantly lower maximum flow rate on average. However, in regression analysis of flow rate including SaO2, SpO2, PaO2, and race, SpO2 was the only significant predictor (P=0.024). When analyzing for fraction of inspired oxygen — including SaO2, SpO2, PaO2, and race — SaO2 (P=0.0003) and PaO2 (P=0.0230) were significant.

“While race is an imperfect proxy for skin color, it is an ingrained component of persistent inequities in medical practices,” Balmaceda said. “Therefore, more research and development should be done to reduce biases in medical devices and subsequent patient care.”

The increased reliance on pulse oximetry during the COVID-19 pandemic led to greater recognition of race-based inaccuracies in pulse oximetry measurements, specifically that patients with darker skin are more likely to experience occult hypoxemia, defined as substantial arterial hypoxemia that is detected through blood gas, but not pulse oximetry.

Pulse oximetry is based on the fact that oxygenated and deoxygenated hemoglobin absorb light in different wavelengths. While hemoglobin is the main chromophore utilized by pulse oximetry, it is now known that the chromophore melanin can interfere with pulse oximetry findings.

“Several studies have been released that show a discrepancy in patients with darker skin; however, there are few published studies that specifically targeted acute hypoxemic respiratory failure in the intensive care unit,” Balmaceda said.

The study included data on 112 white patients and 32 Black patients with AHRF treated in the ICU at the University of Kansas Medical Center from 2015 through 2020.

Gender Disparities

While women were more likely than men to be on bronchodilator therapy (92.3% vs 83.8%), “overall there appears to be no statistically significant difference in the diagnostic workup and management [of COPD] based on gender,” said Avasarala during her presentation.

Women and men had similar proportions of pulmonary function test referrals (79.2% and 76.3%, respectively), as well as documented pulmonary function tests conducted (69.5% and 67.5%) and pulmonary rehabilitation referrals (14.1% and 12.3%).

Avasarala noted that while their study did not show significant differences in COPD diagnosis and management by gender, other studies have shown significant gender differences in disease presentation.

Despite smoking less, older women have been shown to have more severe dyspnea and COPD than older men, she said.

Furthermore, “there is a female predominance of patients with severe COPD diagnosed at an early age,” she noted. “So, a patient that is younger than 55 with severe COPD is more likely to be female. And younger women with COPD have more severe dyspnea, air flow limitation, and exacerbations than younger men.”

Prior research has suggested that anatomical differences, including smaller lung volume in women, may explain the gender differences observed in disease course. It has also been suggested that hormonal factors may play a role.

Avasarala said more research is needed to explore these and other hypotheses that might explain the differences in COPD presentation and progression between women and men.

This study included 526 patients with a diagnosis of COPD seen at least three times at the Mercy Health Clinic from November 2016 to October 2019. About half of women and men were current smokers.