Oxygen tension under hyperbaric conditions in healthy pig brain

Objective: To investigate the effect of hyperbaric conditions on brain oxygenation, intracranial pressure and brain glucose/lactate levels in healthy non-brain-traumatized animals. Design and setting: Prospective animal study in a hyperbaric chamber. Subjects: Twelve adult Landrace/Yorkshire pigs. Interventions: The animals were normoventilated in a pressure-controlled mode according to the open lung concept first at normobaric pressures (FiO₂ of 0.4 and 1.0) and subsequently in the hyperbaric chamber at 1.9 and 2.8 bar (both at an FiO₂ of 1.0). Under these conditions brain oxygen tension and intracranial pressure were recorded and brain glucose/lactate levels were measured by microdialysis. Results: At normobaric conditions, increasing the FiO₂ from 0.4 (baseline) to 1.0 resulted in a significant increase in brain oxygen tension from 33 ± 14 to 63 ± 28 mmHg (P<0.05). Compared with baseline, both hyperbaric conditions (at an FiO₂ Of 1.0) led to a significant increase in brain oxygen tension to 151 ± 65 mmHg (P<0.001) at 1.9 bar and to 294 ± 134 mmHg (P<0.001) at 2.8 bar. Conclusions: If there is a need for increased oxygenation in the brain, then one way to achieve this is to apply hyperbaric conditions at 100% oxygen. Compared with an atmospheric pressure with a FiO₂ of 0.4, a nine-fold increase (900%) in PbrO₂ values can be reached by increasing the FiO₂ to 1.0 and the pressure to 2.8 bar. In this study, hyperbaric oxygen pressure in the brain did not lead to changes in intracranial pressure or in brain glucose/lactate levels.