1. Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
2. Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA, USA
3. Spaulding-Harvard SCI Model System, Spaulding Rehabilitation Hospital and Department of Physical Medicine and Rehabilitation, Harvard Medical School, Charlestown, MA, USA
4. Rehabilitation Medicine Service, VA Boston Healthcare System, West Roxbury, MA, USA
5. Pulmonary and Critical Care Medicine Unit and Department of Medicine, Massachusetts General Hospital, Boston, MA, USA
6. Pulmonary and Critical Care Medicine Section, Medical Service, VA Boston Healthcare System, West Roxbury, MA, USA