Determination of oxygen dosage effects on cytochrome oxidase after anoxia in brain.

Recent evidence reports that high doses of O(2) administered via hyperbaric oxygen therapy (HBOT) improve the return of spontaneous circulation (ROSC), and the outcome of damage to the heart following a 25 min normothermic cardiac arrest. However, excessive O(2) during HBOT can be toxic. Near infrared absorbance spectroscopy (NIRS) measures and determines when cytochrome oxidase (aa(3)), the O(2) end user, changes from reduced to oxidized, signifying adequate dosage. Present NIRS monitoring methods do not account for change in scattering expected in severe anoxia. Given this limitation, we simultaneously measured changes in intensity and scattering that occurred over time after 830 nm light traveled 4.25 cm through brain tissue during both normoxia and anoxia. Results indicated increased intensity and scattering during anoxia with correlation between the two, demonstrating that scattering does not remain constant and is associated with intensity. With this additional insight in concurrent scattering and intensity change during anoxia, we believe improvements can be made to our aa(3) measuring technique resulting in a method to ascertain adequate O(2) dosage during HBOT.