This study was purposed to study the effect of reoxygenation with room air as compared to FiO2 1.0 in a feline model subjected to hypoxemia followed by reoxygenation. Changes in the brain energy metabolism were investigated by 31P magnetic resonance spectroscopy(31P MRS).

Twelve cats were employed for this study and divided into two groups(6 cats each). Both groups were subjected to hypoxemia for 1 hr with FiO2 0.07 followed by reoxygenation for 2hrs. For group I, the reoxygenation was done by FiO2 1.0 and for group 2, by room air. Brain intracellular pH and the ratio of Pcr/Pi(phosphocreatine/inorganic phosphate) were calculated from the spectra acquired every 15 mimutes of the hypoxemia and reoxygenation periods.

The intracellular pH of the baseline were 7.07±0.01 and 7.04±0.01 for group 1 and group 2, respectively, and dropped to 6.89±0.04 and 6.83±0.06 during hypoxemia. For both groups, the intracellular pH returned to baseline values after 30 minutes of reoxygenation. The ratios of Pcr/Pi of the baseline were 2.41±0.21 and 2.47±0.15, for group 1 and group 2, and dropped to 0.77±0.10 and 0.70±0.11, respectively, during hypoxemia and recovered to the baseline values after 30 minutes of reoxygenation for both groups. For both pH and the ratios of Pcr/Pi, the differences between the groups were statistically insignificant.

From this study, we can conclude that reoxygenation by room air is as effective as FiO2 1.0 in the feline model of hypoxemia investigated by 31P MRS.