1. Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts;
2. Department of Anesthesia, Critical Care, and Pain Medicine, Harvard Medical School, Boston, Massachusetts;
3. Electronics Engineering Division, Aeronautics Institute of Technology, Sao Paulo, Brazil; and
4. Disciplina de Pneumologia, Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, Sao Paulo, Brazil