Lightweight Noninvasive Trauma Monitor for Early Indication of Central Hypovolemia and Tissue Acidosis.

摘要

Hemorrhage is a major cause of soldier death, particularly in the first hour of injury. Seriously injured soldiers must be quickly identified and appropriate resuscitation techniques applied. Currently available vital sign measurements are inadequate for this task. In previous swine and human studies we have demonstrated that muscle oxygen measurements respond rapidly to internal bleeding and that muscle pH can be used to assess severity of injury and adequacy of resuscitation. We have developed a prototype patient monitor which noninvasively and continuously determines muscle oxygen and pH. We sought to determine whether the application of this noninvasive trauma monitor in a human model of progressive, central hypovolemia by lower body negative pressure (LBNP) would provide an early indication of impending hemodynamic instability. Methods: Healthy human volunteers (30) underwent LBNP in 5 min intervals of -15, -30, -45, and -60 mm Hg, then increasing by -10 mm Hg to presyncope. Mean arterial pressure (MAP), heart rate (HR), arterial oxygen saturation via pulse oximetry (SpO2), stroke volume (SV) and total peripheral resistance (TPR) were measured continuously and noninvasively throughout the study. Muscle oxygen saturation (SmO2) and muscle pH (pHm) were determined noninvasively from near infrared spectra which were corrected for interference from skin pigment and fat. For each LBNP level the last 3 minutes of data were averaged for all variables. For each parameter, linear mixed model analysis was used to determine the first level of LBNP that could be distinguished statistically from baseline.