1. Division of Pulmonary, Allergy, and Critical Care
2. Palliative and Advanced Illness Research Center, and
3. Leonard Davis Institute of Health Economics and
4. Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, Pennsylvania; and
5. Center for Emergency Care Policy and Research, Department of Emergency Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
6. Division of Research, Kaiser Permanente, Oakland, California