The late J. S. Gravenstein was the founder and a long-time faculty member of the Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL, USA. Michael B. Jaffe is a biomedical engineer working in advanced technology for Philips-Respironics, Wallingford, CT and currently serves on international standards committees relating to respiratory gas monitoring. Nikolaus Gravenstein is Professor in the Department of Anesthesiology and Department of Neurosurgery, University of Florida College of Medicine, Gainesville, FL, USA. David A. Paulus is Professor in the Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL, USA.