Effects of short sustained lung inflations on cerebral blood flow and cerebral tissue oxygenation in the juvenile rabbit

Background. Sustained lung inflations improve oxygenation but may impair hemodynamics. This study aimed to determine effects of short sustained inflations on cerebral blood flow and cerebral tissue oxygenation in experimental lung injury. Methods. Experiments were performed in 6 juvenile ventilated New Zealand white rabbits. The effects of a series of sustained inflations at 20, 25 and 30 cmH₂O pressure for 15 seconds duration each on hemodynamics, cerebral blood flow and cerebral tissue oxygenation were determined by laser Doppler flowmetry and cerebral tissue oxygen tension measurement in naive animals, after surfactant depletion and subsequent fluid filling of the lung. Results. During the series of sustained inflations the mean arterial blood pressure decreased by 73%, 52% and 32% and the mean cerebral blood flow decreased by 73%, 39% and 30% in naive animals, after surfactant depletion and with fluid filling of the lung respectively. Arterial oxygen saturation was maintained or increased, while mean cerebral tissue oxygenation decreased by 48% (naive), 8% (surfactant depletion) or increased by 81% (surfactant depletion and fluid filling). Three minutes after the sustained inflations blood gases were similar to the blood gases prior to the sustained inflations. Conclusion. A series of short sustained lung inflations of 15 seconds duration can impair cerebral blood flow but increase arterial oxygen saturation in this juvenile animal model. The combination of these effects resulted in either a decrease or increase in regional cerebral tissue oxygenation.