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The Compensatory Reserve Index Following Injury: Results of a Prospective Clinical Trial

Stewart, Camille L.; Mulligan, Jane; Grudic, Greg Z.; Talley, Mark E.; Jurkovich, Gregory J.; Moulton, Steven L.

doi: 10.1097/SHK.0000000000000647
Clinical Aspects

Introduction: Humans are able to compensate for significant blood loss with little change in traditional vital signs. We hypothesized that an algorithm, which recognizes compensatory changes in photoplethysmogram (PPG) waveforms, could detect active bleeding and ongoing volume loss in injured patients.

Methods: Injured adults were prospectively enrolled at a level I trauma center. PPG data collection was conducted using a custom-made pulse oximeter. Waveform data were post-processed by an algorithm to calculate the compensatory reserve index (CRI), measured on a scale of 1 to 0, with 1 indicating fully compensated and 0 indicating no reserve, or decompensation. CRI was compared to clinical findings.

Results: Fifty patients were enrolled in the study; 3 had incomplete data, 3 had indeterminate bleeding, 12 were actively bleeding, and 32 were not bleeding. The mean initial CRI of bleeding patients was significantly lower compared with the non-bleeding patients (CRI 0.17, 95% CI = 0.13–0.22 vs. CRI 0.56, 95% CI = 0.49–0.62, P < 0.001). Using a cut-off of 0.21 had a sensitivity of 0.97 and specificity of 0.83 for identifying bleeding patients. CRI had a higher sensitivity than heart rate (75%), systolic blood pressure (63%), shock index (27%), base deficit (29%), lactate (80%), hemoglobin (50%), and hematocrit (50%). During ongoing bleeding, CRI decreased following fluid resuscitation, and conversely increased for patients who were not bleeding.

Conclusions: A novel computational algorithm that recognizes subtle changes in PPG waveforms can quickly and noninvasively discern which patients are actively bleeding and continuing to bleed with high sensitivity and specificity in acutely injured patients.

*University of Colorado School of Medicine, Aurora, Colorado

Flashback Technologies Inc., Boulder, Colorado

Children's Hospital Colorado, Aurora, Colorado

§Denver Health Medical Center, Denver, Colorado

Address reprint requests to Camille L. Stewart, MD, Department of Surgery, University of Colorado School of Medicine, 12631 E 17th Ave, C-305, Aurora, CO 80045. E-mail:

Received 29 February, 2016

Revised 25 March, 2016

Accepted 4 May, 2016

Drs GZG, JM, and SLM developed the Compensatory Reserve Index (CRI) algorithm utilized in this study. The underlying intellectual property is assigned to the Regents of the University of Colorado. Drs GZG and SLM licensed the technology from the University in 2009 and co-founded Flashback Technologies, Inc. Drs GZG and JM are employed and Dr SLM is a consultant at Flashback Technologies. Dr CLS, Mr MET, and Dr GJJ have declared no conflicts of interest.

The views, opinions and/or findings contained in this report are those of the authors and should not be construed as an official Department of the Army position, policy or decision unless so designated by other documentation.

This research was supported by funding from the United States Army Medical Research and Materiel Command Combat Casualty Research Program, and the US Army Small Business Innovative Research (SBIR) program under grants: W81XWH-09-1-0750, W81XWH-09-C-0160, W81XWH-11-2-0091, W81XWH-11-2-0085, W81XWH-12-2-0112, W81XWH-13-CCCJPC6, and W81XWH-13-C-0121.

The authors report no conflicts of interest.

© 2016 by the Shock Society