Influence of osmolytes on in vivo glucose monitoring using optical coherence tomography

Diabetes mellitus and its complications are the third leading cause of death in the world, exceeded only by cardiovascular disease and cancer. Tighter monitoring and control of blood glucose could minimize complications associated with diabetes. Recently, optical coherence tomography (OCT) for noninvasive glucose monitoring was proposed and tested in vivo. The aim of this work was to investigate the influence of changes in blood glucose concentration (glu]) and sodium concentration (Na+]) on the OCT signal. We also investigated the influence of other important analytes on the sensitivity of glucose monitoring with OCT. The experiments were carried out in anesthetized female pigs. The OCT images were acquired continuously from skin, while glu] and Na+] were experimentally varied within their physiological ranges. Correlations of the OCT signal slope with glu] and Na+] were studied at different tissue depths. The tissue area probed with OCT was marked and cut for histological examination. The correlation of blood glu] and Na+] with the OCT signal slope was observed in separate tissue layers. On average, equimolar changes in glu] produced 2.26 +/- 1.15 greater alterations of the OCT signal slope than changes in Na+]. Variation of concentrations of other analytes did not influence the OCT signal slope. The influence of Na+] on relative changes in the OCT signal slope was generally less than glu]-induced changes. OCT is a promising method for noninvasive glucose monitoring because of its ability to track the influence of changing glu] on individual tissue layers.