Measurement of Arterial, Venous, and Interstitial pO2 during Acute Hypoxia in Rat Brain using a Time-Resolved Luminescence-Based Oxygen Sensor

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Abstract
This is the first publication using a fiber optic “optode” and a luminescence based pO2 detection method for assessing neural tissue oxygenation. The system was used to simultaneously monitor pO2 in tissue (PtO2) and venous blood (PVO2) during normoxia, hyperoxia and hypoxia. PaO2 was varied by changing inspired oxygen (FiO2) from 0.3 to 0.13. Tissue and arterial pO2 were measured in 5 rats while the simultaneous venous measurements were undertaken in 3 animals. The PtO2 was 29 ± 10 at an arterial pO2 of 116±10 (mean ± SE, n = 5). The PVO2 was consistently higher than PtO2 although PVO2 approached PtO2 as PaO2 declined to 50mmHg and was lower than tissue pO2 during the complete hypoxic period in one animal. These data indicate that brain venous pO2 is not representative of brain tissue pO2 and support published models predicting that in brain PVO2 is higher than PtO2.