Photonics-based in vivo total hemoglobin monitoring and clinical relevance

Anemia is a serious disorder which, as a result of antiquated invasive blood testing, is undiagnosed in millions of people in the U.S. As a result of the clinical need, many technological solutions have been proposed to measure total blood hemoglobin, and thus diagnose anemia, noninvasively. Because hemoglobin is the strongest chromophore in tissue, spectroscopic methods have been the most prevalently investigated. Difficulties in extracting a quantitative estimation of hemoglobin based on tissue absorption include variability in the absorption spectra of hemoglobin derivatives, interference from other tissue chromophores, and interpatient physiological variations affecting the effective optical path length of light propagating in tissue. In spite of these challenges, studies with a high degree of correlation between in vitro and in vivo measured total hemoglobin have been disclosed using variants of transmission and diffuse reflection spectroscopy in assorted physiological locations. A review of these technologies and the relevant advantages/disadvantages are presented here.