Cardiopulmonary Function in Very Preterm Lambs during Liquid Ventilation

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Abstract
Summary: Cardiopulmonary function was evaluated in very preterm lambs (106 ± 0.7 S.E. days gestation, 1.66 ± 0.12 S.E. kg birth weight) during fluorocarbon ventilation. Lambs were delivered by cesarean section after epidural anesthesia. Indwelling arterial, venous, and tracheal cannulae were placed before clamping the cord. Lambs were then mechanically ventilated with oxygenated fluorocarbon for approximately 2 h. During this period it was possible to maintain adequate gas exchange and stable cardiac function. Transpulmonary pressure, liquid flow, and tidal volume tracings enabled determination of lung compliance, CL = 0.58 ± 0.12 S.E. ml · cmH2O · kg-1, inspiratory resistance, R1 = 3600 ± 604 S.E. cmH2O · liter−1 · sec−1, and expiratory resistance, RE = 4034 ± 2183 S.E. cmH2O/liter/sec. Lung compliance of the 106-day-old fluorocarbon-filled lung is similar to the more mature 138-143-day-old air-filled lung in preterm lambs. Based on the data presented herein we have extended the viability of the preterm lamb to the limit of pulmonary capillary development rather than that of the pulmonary surfactant system.