1. Department of Anesthesia, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 2C4;
2. Third Department of Internal Medicine;
3. Department of Anesthesiology and Resuscitology, Nagoya City University Medical School, Nagoya, Japan 467-8601; and
4. Department of Physiology, Queen's University, Kingston, Ontario, Canada K7L 3N6