1. Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
2. Medical School, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
3. Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
4. Department of Surgery, Division of ENT, Clement J. Zablocki VA Medical Center, Milwaukee, Wisconsin, USA
5. Anesthesiology, TVHS VA Medical Center, Nashville, Tennessee, USA
6. Departments of Anesthesiology and Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, USA