Abstract
Total liquid ventilation (TLV) using perfluorocarbons has shown promising results for the management of neonatal respiratory distress. However, one important safety consideration for TLV is a better understanding of the early events during the transition to TLV, especially regarding the fate of residual air in the non-dependent-lung regions. Our objective was to assess perflubron distribution during transition to TLV using electrical impedance tomography, complemented by fluoroscopy, in a neonatal lamb model of induced surfactant deficiency. Eight lambs were anesthetized and ventilated in supine position. Surfactant deficit was induced by saline lung lavage. After deflation, lungs were filled with 25 ml/kg perflubron over 18 s, and TLV was initiated. Electrical impedance tomography data was recorded from electrodes placed around the chest, during the first 10 and at 120 min of TLV. Lung perfusion was also assessed using hypertonic saline injection during apnea. In addition, fluoroscopic sequences were recorded during initial lung filling with perfluorocarbons, then at 10 and 60 min of TLV. Twelve lambs were used as controls for histological comparisons. Transition to TLV involved a short period of increased total lung volume (p = 0.01) secondary to recruitment of the dependent lung regions. Histological analysis shows that TLV was protective of these same regions when compared to gas-ventilated lambs (p = 0.03). The non-dependent lung regions filled with perflubron over at least 10 min, without showing signs of overdistention. Tidal volume distribution was more homogenous in TLV than during the preceding gas ventilation. Perflubron filling was associated with a non-significant increase in the anterior distribution of the blood perfusion signal, from 46 ± 17% to 53 ± 6% (p = 0.4). However, combined to the effects on ventilation, TLV had an instantaneous effect on ventilation-perfusion relationship (p = 0.03), suggesting better coupling. Conclusion: transition to TLV requires at least 10 min, and involves air evacuation or dissolution in perflubron, dependent lung recruitment and rapid ventilation-perfusion coupling modifications. During that time interval, the total lung volume transiently increases. Considering the potential deleterious effect of high lung volumes, one must manage this transition phase with care and, we suggest using a real-time monitoring system such as electrical impedance tomography.
Highlights
Total liquid ventilation (TLV), where dense liquid perfluorochemicals (PFC) are used to fill and ventilate the lungs, has promising properties for the management of the extremely immature neonate (Wolfson and Shaffer, 2005)
Electrical impedance tomography (EIT) signal was acquired for all 8 lambs in the TLV experimental group
Despite an increase in end-expiratory PFC volume left in the lungs during the first minute of TLV, from 25 ml/kg to 30 ml/kg, end-expiratory global impedance decreased slightly during this same time interval (p = 0.02), suggesting that more air is evacuated than PFC entering the lungs
Summary
Total liquid ventilation (TLV), where dense liquid perfluorochemicals (PFC) are used to fill and ventilate the lungs, has promising properties for the management of the extremely immature neonate (Wolfson and Shaffer, 2005). Conventional gas mechanical ventilation typically used to support these infants generates ventilator-induced lung injury through heterogeneous ventilation (Ramos et al, 2016), volutrauma (Hernandez et al, 1989) and inflammation (Speer, 2006; Ramos et al, 2016). It is associated with the development of bronchopulmonary dysplasia, a chronic disease with long term morbidity (Gough et al, 2012). TLV appears as an excellent candidate for bronchopulmonary dysplasia prevention in the most extreme preterm newborns (Wolfson and Shaffer, 2005), and for which animal studies have been positive to date (Wolfson et al, 1992; Degraeuwe et al, 2000; Cox et al, 2003)
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