Who cares about preventing acute respiratory distress syndrome?

Acute respiratory distress syndrome (ARDS) is a common, lethal, and morbid respiratory complication primarily seen in the setting of major trauma and infection. Despite advances in mechanical ventilation for ARDS, many interventions have not been successful in reducing mortality. Recent grant announcements and ongoing clinical trials indicate an interest in preventing ARDS. This Perspective challenges some of the basic assumptions of ARDS prevention and preventive care in the intensive care unit. ARDS is an organ function surrogate outcome. Studies of surrogate outcomes in medicine have repeatedly failed to show an association with patient-centered outcomes that might include mortality, quality of life, patient satisfaction, and cost. Organ failure surrogate outcomes in critical care, including oxygenation, cardiac output, and blood pressure, have similarly failed to show a consistent association with patient-centered benefit. Trials designed to demonstrate an effect on surrogate outcomes will rarely be able to demonstrate small, but important, harms so that the net benefit of prevention can be calculated. This will leave clinicians with insufficient information to balance the unknown benefits of ARDS prevention with imprecisely estimated costs or risks of prevention. Because ARDS diagnosis relies on oxygenation and the chest radiograph that might be directly influenced by the prophylactic intervention, studies must be designed to insure that the prevention is not merely cosmetic. Strategies that prevent ARDS need to be tested in trials sufficiently powered to demonstrate their patient-centered costs, benefits and harms before widespread adoption.