1. Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Harvard University, Boston, Massachusetts
2. Divisao de Pneumologia, Instituto do Coração, Hospital das Clinícas, Faculdade de Medicina, Universidade de São Paulo, São Paulo, São Paulo, Brazil; and
3. Department of Anesthesia and Critical Care, Niguarda Hospital and University of Milano-Bicocca, Milan, Italy