“…Individual-level primary themes were: 1) differential access to care (28, 30, 33, 106, 114, 122, 168, 170), 2) varying clinical presentations (26, 27, 30, 31, 80, 92, 128, 161, 168), 3) different religious/cultural preferences (26, 27, 80, 89, 93, 168), or other unmeasured individual SDoH as confounders (30, 84, 96). Hospital-level mechanisms included: 1) provider-level treatment variation (26, 31, 80, 93, 167, 169) and 2) between-hospital variability in offering ECMO, timing of initiation, organizational structure, experience, and standardized care practices/processes (27, 30, 31, 80, 90, 106, 122, 123, 129–131, 154, 157, 161, 168–173). Specific systemic/structural factors such as legal frameworks, economic systems, and social policies included: 1) healthcare system adequacy (pay-for-performance measures [31, 122], disparate insurance access and quality [28, 32, 106, 128, 167] and, in countries with universal healthcare, need for enhanced systems to serve marginalized communities [30, 110, 114, 117]) and 2) geographic centralization, balancing consolidated expertise, and quality with accessibility of time-critical technology (106, 171–174).…”