hysiology), "Heart Rate Variability: Standards of Measurement, Physiological Interpretation, and Clinical Use," Circulation 93 (1996): 1043-65. 30 Arpi Minassian, PhD, Mark A. Geyer, PhD, Dewleen G. Baker, MD, Caroline M. Nievergelt, PhD, Daniel T. O'Connor, MD, Victoria B. Risbrough, PhD, and the Marine Res