1. Departments of Surgery, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA 23298-0454, USA
2. Functional Circulation, Northbrook, IL 60062, USA
3. Emergency Medicine, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA 23298-0454, USA
4. Physiology and Biophysics, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA 23298-0454, USA