Novel assessment of acute lung injury by in vivo near-infrared spectroscopy

We investigated the feasibility and validity of near-infrared (NIR) spectro scopy for evaluation of acute lung injury (ALI). In an in vitro model simul ating the spectrophotometric characteristics of the lung, NIR spectroscopy could precisely detect changes in water volume, suggesting its ability to a ssess the extent of pulmonary edema caused by ALI. The different grades of ALI were induced in rats by administering oleic acid and varying the pulmon ary ventilation conditions, and NIR spectroscopy was employed to determine lung water content and hemoglobin (Hb) oxygenation of the lungs. NIR spectr oscopy detected increased water content even in histologically mild ALI. Th e changes in lung water content measured by NIR spectroscopy were significa ntly correlated with gravimetric lung water content (r = 0.877, p < 0.0001) . Deoxy-Hb measured by NIR spectroscopy consistently reflected the histolog ical changes in the lungs, and the deoxy-Hb levels correlated with changes in Sa(O2) (r = -0.798, p < 0.0001). These findings demonstrate that NIR spe ctroscopy can evaluate lung water content and Hb oxygenation quantitatively , and may be a useful tool for assessing pathological status in ALI.