^aBI Stellar-Chance Laboratories, Department of Radiology, Metabolic Magnetic Resonance Research and Computing Center, Hospital of the University of Pennsylvania School of Medicine, 422 Curie Boulevard, Philadelphia, PA 19104-6100, USA

^bDepartment of Otohinolaryngology, Head and Neck Surgery, Johns Hopkins University, Baltimore, MD, USA

^cPulmonary and Critical Care Division, University of Pennsylvania School of Medicine, Philadelphia, PA, USA

^dDepartments of Anesthesia and Bioengineering, University of Pennsylvania School of Medicine, Philadelphia, PA, USA