A Comparison of Normalization Techniques for Individual Baseline-Free Estimation of Absolute Hypovolemic Status Using a Porcine Model

Hypovolemic shock is one of the leading causes of death in the military. The current methods of assessing hypovolemia in field settings rely on a clinician assessment of vital signs, which is an unreliable assessment of hypovolemia severity. These methods often detect hypovolemia when interventional methods are ineffective. Therefore, there is a need to develop real-time sensing methods for the early detection of hypovolemia. Previously, our group developed a random-forest model that successfully estimated absolute blood-volume status (ABVS) from noninvasive wearable sensor data for a porcine model (n = 6). However, this model required normalizing ABVS data using individual baseline data, which may not be present in crisis situations where a wearable sensor might be placed on a patient by the attending clinician. We address this barrier by examining seven individual baseline-free normalization techniques. Using a feature-specific global mean from the ABVS and an external dataset for normalization demonstrated similar performance metrics compared to no normalization (normalization: R2 = 0.82 +/- 0.025|0.80 +/- 0.032, AUC = 0.86 +/- 5.5 x 10-3|0.86 +/- 0.013, RMSE = 28.30 +/- 0.63%|27.68 +/- 0.80%; no normalization: R2 = 0.81 +/- 0.045, AUC = 0.86 +/- 8.9 x 10-3, RMSE = 28.89 +/- 0.84%). This demonstrates that normalization may not be required and develops a foundation for individual baseline-free ABVS prediction.