Tissue hemoglobin index: a non-invasive optical measure of total tissue hemoglobin

Abstract
The tissue hemoglobin index (THI) is a hemoglobin signal strength metric provided on the InSpectra™ StO2 Tissue Oxygenation Monitor, Model 650. There is growing interest regarding the physiologic meaning of THI and whether a clinically useful correlation between THI and blood hemoglobin concentration exists. A series of in vitro and in vivo experiments was performed to evaluate whether THI has potential utility beyond its primary purpose of helping InSpectra™ device users optimally position a StO2 sensor over muscle tissue.