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Box and Whisker plots of one-minute average CRI values, before blood loss, at maximum blood
loss (at end of blood withdrawal for subjects completing ~20% blood volume withdrawal), during
symptoms (at end of blood withdrawal for subjects experiencing symptoms and not completing ~20%
blood loss), and after blood replacement. For each panel above, the number of subjects was 42, 32, 7, and
32, respectively.
Conclusions
The results of this study met the pre-specified pass/fail criteria and thus provide supporting evidence that
CRI trends with intravascular volume changes as compared to direct measurement of blood volume
decrease and increase. It should be noted that this clinical validation of CRI was performed using healthy
volunteers aged 19-36 years under supine, non-motion conditions.
Clinical Use Considerations
Clinical users of the M1 should understand the basic principles regarding the derivation of the CRI value
as well as the strengths and limitations of research conducted to date. As noted above, in normal
volunteers under laboratory conditions, CRI was found to correlate closely with changes in intravascular
blood volume (up to ~ 20% of blood volume loss).
Nonetheless, this device is intended as an adjunct in
patient assessment. It must be used in conjunction with other methods of assessing clinical signs and
symptoms.
CRI estimates are based on reference data collected in ideal conditions. Progressive declines to low CRI
values indicate measurements based on subjects in clinical studies exhibiting symptoms of increasing
hemodynamic instability, most notably precipitous hypotension and clinical symptoms associated with
shock. However, since many known and unknown factors (artifacts, advanced age, cardiovascular disease,
medications, acute trauma, etc.) may affect these measurements, changes in CRI should always be
interpreted cautiously as a
potential
indicator of changes in patient status due to volume change. It is
recommended that users carefully consider the clinical conditions and evaluate conventional vital signs
when interpreting changes in CRI.
References
Convertino, V, G. Grudic, J. Mulligan, and S. Moulton. 2013. "Estimation of individual-specific progression
to impending cardiovascular instability using arterial waveforms."
Journal of Applied Physiology
115 (8): 1196-202.
Convertino, V, J Howard, C Laborde, S Cardin, P Batchelder, J Mulligan, G Grudic, and D Macleod. 2015.
“
Individual-specific, beat-to-beat trending of significant human blood loss: The compensatory
reserve.”
SHOCK
44: 27
–
32.
Moulton, S, J Mulligan, M.A. Santoro, K Bui, G Grudic, and D MacLeod.
2017. “
Validation of a noninvasive
monitor to continuously trend indiv
idual responses to hypovolemia.”
Journal of Trauma and Acute
Care Surgery
83 (1): S104
–
S111.
Moulton, S., J. Mulligan, G. Gr
udic, and V. Convertino. 2013. “
Running on empty? The compensatory
reserve index.”
Journal of Trauma and Acute Care Surgery
75 (6): 1053-1059.
