The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

ELECTRICAL IMPEDANCE TOMOGRAPHY CONFIRMS IMPROVEMENT OF LUNG AERATION AND VENTILATION IN SPONTANEOUSLY BREATHING PIGS DURING HFOV.

Karel Roubik1, Marc van Heerde2, Martin C. Kneyber3, Dick G. Markhorst2; 1Dep. of Biomedical Technology, CTU in Prague, Fac. of Biomedical Engineering, Kladno, Czech Republic; 2Department of Pediatric Intensive Care, VU University Medical Center, Amsterdam, Netherlands; 3Department of Pediatric Intensive Care, ChildrenÂ’s Hospital, University Medical Center Groningen, Groningen, Netherlands

Background: Maintenance of spontaneous breathing is advocated in mechanical ventilation. The objective of the study was to evaluate the effect of spontaneous breathing on lung characteristics during high-frequency oscillatory (HFO) ventilation in an animal model of mild lung injury. The HFO ventilator was equipped with a demand flow system to facilitate spontaneous breathing. Electrical impedance tomography (EIT) was used to assess lung aeration and ventilation and the occurrence of hyperinflation on account of spontaneous breathing. Design: Animal experiment. Setting: University animal laboratory. Subjects: Eight pigs (47 - 64 kg). Interventions: Lung injury was induced by lung lavage with normal saline. Spontaneous breathing was preserved during HFO ventilation. HFO ventilation was applied, in runs of 30 minutes, with a continuous fresh gas flow (CF) or a custom-made demand flow (DF) system. In the end animals were studied paralyzed. EIT was used for evaluation of lung characteristics. Results: Comparison of end expiratory lung volume (EELV) showed that lung volume was best preserved when spontaneous breathing was maintained during HFO ventilation compared to HFO ventilation with muscular paralysis. The lung volume was predominantly preserved in the dependent lung regions. A significant shift in ventilation toward the dependent lung regions was observed when HFO ventilation with demand flow was applied compared to HFO ventilation and spontaneous breathing suppressed. Regional filling characteristics of the lung showed no signs of regional hyperinflation on account of spontaneous breathing with either CF or DF. Conclusions: Lung volume is preserved by spontaneous breathing during HFO ventilation in a porcine model of mild (low mean airway pressure) lung injury. Whether similar results would be observed in severe human ARDS will require further research. Acknowledgement: The study was partly supported by grant MSM 6840770012. Sponsored Research - None