In models of ECMO of piglets with healthy or acute respiratory distress syndrome (ARDS), the results of Gregory et al. and Henderson et al. demonstrated that although the hematocrit of the HBOC-201 group was significantly lower than the blood group and the blood pressure and methemoglobin concentration in the HBOC-201 group were slightly increased, HBOC-201-primed ECMO was well-tolerated, maintained hemodynamic stability, and provided good oxygen delivery (89, 90). Here, HBG2 is linked to acute respiratory distress syndrome.