The use of extracorporeal membrane oxygenation (ECMO) has expanded significantly, especially during the COVID-19 pandemic, but membrane lung (ML) function at high altitudes remains unexplored. This study aimed to determine whether ML oxygen delivery (V’O₂ML) capacity during ECMO is lower in high-altitude Xining than at low-altitude Beijing in China.

In this prospective observational study, patients who received ECMO were categorized into the Xining or Beijing group based on treatment center. Patients were monitored for ML gas transfer on the third day of ECMO, and clinical outcomes were compared between the two groups.

Sixty patients were enrolled, 30 in each group. V’O₂ML was significantly lower in the Xining group than in the Beijing group (171 [130-203] ml/min vs. 210 [178-255] ml/min, p = 0.002). Mortality at 60 days showed no significant difference, but ML failure was higher in the Xining group (26.7% vs 6.7%, p = 0.038). V’O₂ML was positively correlated with post-ML arterial partial pressure of oxygen (PaO₂), hemoglobin, and fibrinogen and negatively correlated with D-dimer (all p < 0.001). Older age (OR, 1.075; 95% CI, 1.020-1.132, p = 0.007) and lower V’O₂ML capacity (OR, 0.984; 95% CI, 0.974-0.995, p = 0.005) were independent risk factors for 60-day mortality. The optimal V’O₂ML cutoff for survival was ≥205 ml/min, with higher V’O₂ML associated with better outcomes (p < 0.001).

High altitude is associated with lower V’O₂ML capacity during ECMO, although it does not appear to increase short-term mortality. V’O₂ML is an essential prognostic factor, and further research with larger cohorts and dynamic monitoring of V’O₂ML across different altitudes is recommended.