Current monitoring technologies are unable to detect early, compensatory changes that are associated with significant blood loss. We previously introduced a novel algorithm to calculate the Compensatory Reserve Index (CRI) based on the analysis of arterial waveform features obtained from photoplethysmogram recordings. In the present study, we hypothesized that the CRI would provide greater sensitivity and specificity to detect blood loss compared with traditional vital signs and other hemodynamic measures. Continuous noninvasive vital sign waveform data, including CRI, photoplethysmogram, heart rate, blood pressures, SpO2, cardiac output, and stroke volume, were analyzed from 20 subjects before, during, and after an average controlled voluntary hemorrhage of ∼1.2 L of blood. Compensatory Reserve Index decreased by 33% in a linear fashion across progressive blood volume loss, with no clinically significant alterations in vital signs. The receiver operating characteristic area under the curve for the CRI was 0.90, with a sensitivity of 0.80 and specificity of 0.76. In comparison, blood pressures, heart rate, SpO2, cardiac output, and stroke volume had significantly lower receiver operating characteristic area under the curve values and specificities for detecting the same volume of blood loss. Consistent with our hypothesis, CRI detected blood loss and restoration with significantly greater specificity than did other traditional physiologic measures. Single measurement of CRI may enable more accurate triage, whereas CRI monitoring may allow for earlier detection of casualty deterioration.
*US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas; †Medical Research & Materiel Command, Fort Detrick, Maryland; ‡CliniMark, Denver; §Flashback Technologies Inc, Boulder; ∥University of Colorado, Aurora, Colorado; ¶Human Pharmacology & Physiology Lab, Duke University Medical Center, Durham, North Carolina
Received 1 Oct 2014; first review completed 27 Oct 2014; accepted in final form 17 Dec 2014
Address reprint requests to Victor A. Convertino, PhD, US Army Institute of Surgical Research JBSA Fort Sam Houston, TX 78234. E-mail: email@example.com.
This research was supported in part by funding from the US Army Medical Research and Materiel Command Combat Casualty Research Program (under grants W81XWH-09-1-0750, W81XWH-09-C-0160, W81XWH-11-2-0091, W81XWH-11-2-0085, and W81XWH-12-2-0112) and the US Army Small Business Innovative Research program. This study was also supported in part by a postdoctoral fellowship provided by the Oak Ridge Institute of Science and Education.
G.Z.G. and J.M. codeveloped the CRI model used in this study. S.L.M. is a cofounder and medical consultant to Flashback Technologies, Inc. V.A.C., J.T.H., C.H-L., S.C., P.B., and D.B.M. have disclosed no conflicts of interest.
The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.