The Compensatory Reserve Index: A New Vital Sign


Humans are able to compensate for large volumes of blood loss with little change in standard vital signs. Research has shown that some subjects can lose up to 20% of their blood volume, with little change in traditional vital signs. Unrecognized volume loss during the compensatory phase can be followed by sudden cardiovascular collapse without warning, a situation in which resuscitative therapy is much less effective and extremely difficult to control.

Flashback Technologies developed The Compensatory Reserve Index (CRI™) in response to the need for an “early warning” system to alert caregivers to a patient’s point of collapse. CRI a groundbreaking new vital sign that monitors a patient’s central volume status from normovolemia to decompensation. CRI is calculated from the pulsatile component of the cardiac cycle, and can be derived from a variety of physiological waveforms and sensors. Our current FDA-cleared device utilizes the PPG or pulse oximetry waveform. CRI provides caregivers continuous and real-time status of how far or near an individual patient may be from the point of decompensation, on an easily readable scale from 1 to 0. Research has demonstrated the technology to be 97% accurate in estimating individual-specific tolerance to central volume loss.


Providing this insight enables caregivers to intervene earlier, when resuscitative therapy is more effective and more lifesaving. CRI trends not only with central volume loss, it provides ongoing real-time monitoring and tracking of a patient’s response to resuscitation therapy. Recognizing CRI’s potential to fill a capability gap with regard to early hemorrhage detection, Flashback’s research has been supported by over $9M in grant funding from the US Department of Defense. Moreover, researchers at the Southwest Texas Regional Advisory Council (STRAC) and US Army Institute of Surgical Research (USAISR) have published independent studies establishing the power of CRI and its superiority to traditional vital signs in detection and monitoring of hemorrhage. Additional grant funding has been provided by the NIH.


Potential Applications In Trauma & Hemorrhage

Hemorrhage is the direct cause of death in approximately 40% of all trauma-related deaths. It is the leading cause of death from trauma in both civilian and military settings. An estimated 25% of trauma deaths on the battlefield are potentially survivable with timely and effective intervention, with 85% of these deaths related to hemorrhage.


Limitations of standard vital signs

The standard vital signs long-used to assess and monitor trauma patients include heart rate, arterial oxygen saturation, respiration, and blood pressure. However, physiological compensatory mechanisms maintain these vital signs to near normal levels despite significant blood loss. Changes occur only after substantial deterioration, when life-saving interventions might be too late. More than 20% of trauma patients with “normal” vital signs end up requiring life-saving intervention.

what if Hemorrhage could be detected earlier?

Early detection and intervention are essential for the treatment of hemorrhage. Research indicates CRI provides clinicians more time to intervene as compared to traditional vital signs. Specifically, research has shown:
· CRI monitoring can reduce the time to recognize the threat of collapse by more than 40%, or 8 minutes.
· Compared to the Shock Index, CRI provided a threefold increase in time to intervene. (A warning of 15 minutes vs. 5 minutes of imminent instability.)

Particularly in the management of acute blood loss: clinicians need to know the clinical trajectory of a patient so that they can anticipate the needs of the patient and intervene early, when the physiology is less complex and more likely to respond to therapy.
— Dr. Steve Moulton; Co-Founder, Flashback & Director of Pediatric Trauma and Burn Services at Children’s Hospital Colorado