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