Significant Disparities Exist in Accessing Extracorporeal Membrane Oxygenation

By Betty Tran, MD, MSc

Associate Professor of Medicine, Division of Pulmonary and Critical Care Medicine, Northwestern University Feinberg School of Medicine, Chicago

SYNOPSIS: After extensive sensitivity analyses to account for severity of illness and confounding, a comparison of patient characteristics of those receiving extracorporeal membrane oxygenation (ECMO) to those treated with mechanical ventilation alone revealed that female patients, those with Medicaid, and those living in the lowest-income neighborhoods were less likely to be treated with ECMO.

SOURCE: Mehta AB, Taylor JK, Day G, et al. Disparities in adult patient selection for extracorporeal membrane oxygenation in the United States. A population-level study. Ann Am Thorac Soc 2023;20:1166-1174.

Extracorporeal membrane oxygenation (ECMO) is an advanced, complex, resource-intensive, and expensive intervention that provides cardiac and respiratory support to patients with acute severe cardiac and/or pulmonary failure. Not all hospitals are ECMO-capable and, given that this is a limited resource that has yet to demonstrate a clear mortality benefit, patient selection has yet to be optimized.^1,2 The goal of this study was to explore real-world patient selection for ECMO.

Adult patients who received mechanical ventilation (MV) and ECMO based on discharge billing codes were identified using the Nationwide Readmissions Database (NRD) from 2016-2019. The primary outcome was ECMO receipt, and the primary exposure variables were patient sex, primary insurance, and median income quartile for the zip code in which they lived. Extensive statistical methods were employed to address potential unmeasured confounding and limited ability to adjust for severity of illness in the original database, with the goal of creating a more homogeneous population of those who received ECMO to determine whether the primary exposures were indeed associated with ECMO receipt.

Among the 2,170,752 patients who received MV between 2016-2019, there were 18,725 ECMO cases. Given common criteria used for ECMO exclusion, compared to those receiving MV alone, patients on ECMO tended to be younger and were less likely to have cancer and chronic lung disease. Overall, female patients were less likely to receive ECMO compared to male patients (adjusted odds ratio [aOR], 0.73; 95% confidence interval [CI], 0.70-0.75). Patients with Medicaid and Medicare had lower odds of being treated with ECMO compared to those with private insurance (aOR, 0.55; 95% CI, 0.52-0.57, and aOR, 0.50; 95% CI, 0.48-0.52, respectively).

Compared to patients living in high-income neighborhoods, those in the lowest-income neighborhood were less likely to receive ECMO (aOR, 0.63; 95% CI, 0.60-0.67). Despite these findings, there were no significant differences in hospital mortality based on sex, insurance, or income for patients treated with either ECMO or MV alone. The results of the primary analysis were preserved even after sensitivity analyses restricted the patient cohort to ECMO-capable hospitals, non-elective admissions, pneumonia or sepsis present on admission only, and after stratification by hospital type.

COMMENTARY

This study adds to literature in other arenas that highlights how advanced therapies are distributed inequitably among patients who otherwise have a similar need for them.^3,4 Although reasons for these differences are beyond the scope of this study, the authors provided some potential reasons that are both feasible and rational. Given that most ECMO-capable hospitals are clustered within academic centers in large, urban areas, it may be difficult for patients living in lower-income (especially rural) neighborhoods with Medicaid to have access to these hospitals upfront.

Furthermore, to gain access to these hospitals, patients would have to undergo a transfer request/acceptance process initiated by their safety net hospital. Multiple studies have implicated that hospital-to-hospital transfer practices have a disproportionate impact on racial/ethnic minorities, female patients, and patients with Medicaid or who are uninsured.^5,6 There may be several reasons for these observations, but overall, patients from these subpopulations (and their families) may feel less empowered to request transfers.

Implicit provider bias also may result in certain patients being less likely to be diagnosed accurately with acute respiratory distress syndrome (ARDS) in the first place and subsequently less likely to be considered for interventions such as lung protective ventilation and, ultimately, ECMO.

The study has several limitations. The NRD is primarily a large dataset and is limited in its ability to provide data for many confounders, including accurate measures of severity of illness. It also relies on billing codes; as a result, misclassification bias may be present. The authors attempted to address these limitations via multiple sensitivity analyses to create a more homogenous population from which to derive their models. Given that all the analyses arrived at the same conclusions suggests that there indeed may be a signal for larger-scale disparities among adult ECMO patient selection that would be worth investigating in the future.

REFERENCES

1. Peek GJ, Mugford M, Tiruvoipati R, et al; CESAR trial collaboration. Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): A multicentre randomized controlled trial. Lancet 2009;374:1351-1363.
2. Combes A, Hajage D, Capellier G, et al; EOLIA Trial Group, REVA, and ECMONet. Extracorporeal membrane oxygenation for severe acute respiratory distress syndrome. N Engl J Med 2018;378:1965-1975.
3. Lat TI, McGraw MK, White HD. Gender differences in critical illness and critical care research. Clin Chest Med 2021;42:543-555.
4. Breathett K, Yee E, Pool N, et al. Association of gender and race with allocation of advanced heart failure therapies. JAMA Netw Open 2020;3:e2011044.
5. Hanmer J, Lu X, Rosenthal GE, Cram P. Insurance status and the transfer of hospitalized patients: An observational study. Ann Intern Med 2014;160:81-90.
6. Shannon EM, Zheng J, Orav J, et al. Racial/ethnic disparities in interhospital transfer for conditions with a mortality benefit to transfer among patients with Medicare. JAMA Netw Open 2021;4:e213474.