Radial oxygen gradients over rat cortex arterioles

Purpose We present the results of the visualisation of radial oxygen gradients in rats’ cortices and their potential use in neurocritical management. Methods PO 2 maps of the cortex of ten sedated, intubated and controlled ventilated Wistar rats were obtained with a camera (SensiMOD, PCO, Kelheim, Germany). Those pictures were analysed and edited by a custom-made software. A virtual matrix, designed to evaluate the cortical O 2 partial pressure, was placed vertically to the artery under investigation, and afterwards multiple regions of interest were measured (width 10 pixels, length 15–50 pixels). The results showed a map of the cerebral oxygenation, which allowed us to calculate radial oxygen gradients over arterioles. Three groups were defined according to the level of the arterial pO 2 : PaO 2 < 80, PaO 2 80–120 and PaO 2 > 120. Gradients were analysed from the middle of the vessel to its border (1), from the border into the parenchyma next to the vessel (2) and a combination of both (3). Results Gradient 1 showed significantly different cortical pO 2 values between the three different groups. The mean pO 2 values were 2.62, 5.29 and 5.82 mmHg/mm. Gradient 2 measured 0.56, 0.90 and 1.02 mmHg/mm respectively. Gradient 3 showed significant results between the groups with values of 3.18, 6.19 and 6.84 mmHg/mm. Conclusion Using these gradients, it is possible to describe and compare the distribution of oxygen to the brain parenchyma. With the presented technique, it is possible to detect pO 2 changes in the oxygen supply of the brain cortex.