ABSTRACT
Optical measures of physiologic status are attractive because they can provide a simple, noninvasive, yet real-time assessment of medical condition. Noninvasive optical monitoring is taken here to mean the use of visible or near-infrared light to directly assess the internal physiologic status of a person without the need of extracting a blood of tissue sample or using a catheter. Liquid water strongly absorbs ultraviolet and infrared radiation, and thus these spectral regions are useful only for analyzing thin surface layers or respiratory gases, neither of which will be the subject of this review. Instead, it is the visible and near-infrared portions of the electromagnetic spectrum that provide a unique “optical window” into the human body, opening new vistas for noninvasive monitoring technologies.
