1 Division of Critical Care Medicine, St. Paul's Hospital; and Centre for Heart Lung Innovation (HLI), University of British Columbia, Vancouver, BC, Canada Departments of Anesthesiology and Neurosurgery, University of Virginia School of Medicine, Charlottesville, VA Division of Pulmonary, Critical Care, and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA; and Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA.