Experimental study for the effect of artificial ventilation and environment on the cardiac autonomic nervous system activity in the central nervous system ischemia

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Artificial ventilation with positive end-expiratory pressure (PEEP) is commonly applied for brain damaged patients. However, the effect of the ventilation on brain function including cardiovascular autonomic nervous system (CANS) activity is not well elucidated. In a first study, we investigate the effect of 5 cmH2O PEEP on CANS activity in the brain damaged rabbits under general anesthesia. We found that 5 cmH2O PEEP depressed CANS activity during the progression of brain damage in rabbits and it was partly due to aggravated brain function induced by PEEP. In a second study, we measured heart rate (HR) variability and systolic arterial pressure (SAP) variability, and analyzed impulse response analysis results between HR and SAP in brain damaged rabbits in order to determine spinal cord function under a brain damaged condition. We found that HR variability was mainly controlled by the brain and SAP variability was mediated by the brain through the spinal cord, while SAP variability was related to HR variability through the spinal cord in brain damaged rabbits. We then concluded that CANS activity was depressed in the animals with acute brain damage during mechanical ventilation using 5 cmH_2O PEEP, and that HR variability is mainly controlled by the brain and SAP variability is mediated by the brain through the spinal cord. 10. KEY WORDS