[1] University of Pennsylvania School of Medicine,Division of Pulmonary, Allergy & Critical Care
[2] University of Pennsylvania,Leonard Davis Institute of Health Economics
[3] University of Pennsylvania School of Medicine,Center for Clinical Epidemiology & Biostatistics
[4] University of Michigan,Division of Pulmonary and Critical Care Medicine
[5] Sunnybrook Health Sciences Centre,Program in Trauma, Emergency, and Critical Care
[6] University of Pittsburgh School of Medicine,Department of Critical Care Medicine, CRISMA Laboratory
[7] Philadelphia Veterans Affairs Medical Center,Center for Health Equity Research and Promotion