Triage and monitoring of patients consists of several vital sign measurements including blood pressure, oxygen saturation, and heart rate. These measurements show varying correlation with patient survival, Injury Severity Score, and the need for life-saving intervention. The most significant disadvantage of their use as part of patient triage is that they are all retrospective by nature, and a change in these indices occur only after substantial hemodynamic compromise and failure of compensatory mechanisms when life-saving interventions might be too late.