“…This physiological phenomenon has been defined as the compensatory reserve, with its measurement relying on a machine learning (ML) approach that incorporates the interrogation of arterial blood pressure waveform features [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Reported measurements of the compensatory reserve have consistently proven to provide greater sensitivity in time (i.e., early) and specificity for identifying individual patient status when compared to traditional standard vital signs in both human experimental [ 2 , 6 , 8 , 9 , 10 , 11 , 12 , 13 ] and clinical [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ] settings. In this regard, the measurement of the compensatory reserve has proven to be “the most informative ‘vital sign’ to be captured in emergency medical care settings” because of its ability to provide earlier and individualized status of patients with hypovolemia [ 2 ].…”