Optical oximetry, and near infrared spectroscopy (NIRS) in particular, is a tool for assessment of the oxygenation status and hemodynamics of various organs, e.g. muscles or the brain.

All cells in the organs of the body have a constant but variable need for oxygen. However, the body’s stores of oxygen are minimal. Therefore, a constant and adequate supply of oxygen to the tissues through circulation of blood is essential. Any interference with tissue oxygenation will lead rapidly to irreversible damage.

Near infrared spectroscopy, the technique on which the OxyMon, Brite MkII, OctaMon, and PortaMon/PortaLite are based, relies mainly on two characteristics of human tissue. First, the relative transparency of tissue to light in the NIR range, and second, the oxygenation-dependent light absorbing characteristics of hemoglobin. By using a number of different wavelengths, the relative changes in hemoglobin concentration can be displayed continuously.