Animal studies have shown that ECMO's can provide one to two weeks' support for the lungs without serious blood damage, in contrast to bubble oxygenators, which allow complete pulmonary bypass for approximately 6 hours, after which severe blood damage occurs at the direct blood-gas interface. If patients with hypoxia secondary to acute reversible lung injury can be supported with ECMO's until the lung lesion heals, improvement in survival rates and avoidance of the hazards of conventional therapy may result. The trial, now completed, was conducted at nine clinical centers in the United States.