Physiologic sensors and methods of application are described. These sensors function by detecting recently discovered variations in the spectral
optical density at two or more wavelengths of light diffused through the
skin. These variations in spectral
optical density have been found to consistently and uniquely relate to changes in the availability of
oxygen in the
skin tissue, relative to the
skin tissue's current need for
oxygen, which we have termed
Physiology Index (PI). Current use of
blood gas analysis and
pulse oximetry provides physiologic insight only to blood
oxygen content and cannot detect the status of energy conversion
metabolism at the
tissue level. By contrast, the PI
signal uniquely portrays when the
skin tissue is receiving ‘less than enough oxygen,’‘just the right amount of oxygen,’ or ‘more than enough oxygen’ to enable aerobic energy conversion
metabolism. The PI sensor detects one pattern of photonic response to insufficient
skin tissue oxygen, or tissue hypoxia, (producing negative PI values) and a directly opposite photonic response to excess
tissue oxygen, or tissue
hyperoxia, (producing positive PI values), with a neutral zone in between (centered at PI zero). Additionally, unique patterns of PI
signal response have been observed relative to the level of physical
exertion, typically with a secondary positive-going response trend in the PI values that appears to correspond with increasing fatigue. The PI sensor illuminates the skin with alternating pulses of selected wavelengths of red and
infrared LED light, then detects the respective amount of light that has diffused through the skin to an aperture located a lateral distance from the
light source aperture. Additional structural features include means of internally excluding light from directly traveling from the light emitters to the
photodetector within the sensor. This
physiology sensor and methods of use offer continuous, previously unavailable information relating to tissue-level energy conversion
metabolism. Several alternative embodiments are described, including those that would be useful in
medical care, athletics, and personal
health maintenance applications.