A series of experiments were performed to assess the feasibility of measuring total hemoglobin (HbT) non-invasively using light in the visible to near infrared (NIR) range. The experiments included spectroscopic measurements of both in vitro isolated tissue components and in vivo human tissue (73 subjects) in a clinical setting. Several different methods of estimating HbT, all by optical non-invasive means, were tested and compared for accuracy relative to standard invasive methods. By combining time-resolved optical absorbances at 3 wavelengths, 750, 965, and 1320 nm, in a fashion that is highly analogous to pulse oximetry, HbT was predicted with a standard error of 1.1 g/dL.
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