Efficacy of Novel Anatomical Sites for Assessment of Muscle Oxygenation During Central Hypovolemia

Background: Muscle tissue oxygenation (SmO2) has been used to track central blood volume loss associated with hemorrhage. Traditional peripheral measurement sites (e.g., forearm) may not be practical due to excessive movement or injury (e.g., amputation). The aim of this study was to evaluate the efficacy of three novel centrally located anatomical loci for assessment of SmO2 under progressive central hypovolemia. Methods: 10 healthy male volunteers were subjected to step-wise prone lower body negative pressure (LBNP) to decrease central blood volume while SmO2 was assessed at the flexor carpi ulnaris (ARM), and 3 novel sites - the deltoid (DELT), latissimus dorsi (LAT), and trapezius (TRAP). SmO2 at the novel sites was compared to the ARM sensor and to stroke volume (SV) responses. Results: A reduction in SmO2 was detected by the ARM sensor at the first level of LBNP (-15 mmHg; p=0.007), and at -30 (DELT), -45 (LAT) and -60 mmHg LBNP (TRAP) by the novel sensors (p≤0.04). SmO2 responses of all novel sensors were correlated with responses at the ARM (R2≥0.80), and tracked the reduction in SV (R2≥0.76), but the LAT site exhibited the strongest linear correlations (table 1). Conclusions: Of the 3 novel sensor sites, the LAT exhibited the strongest linear associations with SmO2 at the ARM, and with reductions in central blood volume. These findings have important implications for detection of hemorrhage in austere environments (e.g., combat) when use of a peripheral sensor may not be ideal, and may facilitate incorporation of these sensors into uniforms.