Liquid ventilation during early development: theory, physiologic processes and application.

Abstract

Clinical statistics indicate that extrauterine viability becomes increasingly compromised at earlier gestational ages. It is generally accepted that this trend is largely due to the immaturity of the pulmonary system. Investigators have attributed the high degree of instability during the perinatal period of the preterm infant to incomplete biochemical development of the lung. Whereas disruption in biochemical development results in alveolar surfactant deficiency, elevated interfacial tension, alveolar instability, and inadequate pulmonary gas exchange, it is possible that incomplete development of other components within the pulmonary as well as other organ systems may also influence ultimate extrauterine viability of the preterm neonate. However, until recently, little was known in this regard as conventional gas ventilation techniques have been unsuccessful in supporting a stable animal preparation for controlled experimental investigation of physiologic processes before approximately 85% gestation. In the early 1970s, the concept of liquid ventilation was applied to the preterm and newborn animal. Since this time, technological advances in liquid delivery systems have established this experimental approach as a viable means to support the preterm infant during the transition from the liquid-filled intrauterine to gas-filled extrauterine environment. Reduction of surface tension, improvement in lung mechanics, effective pulmonary gas exchange, acid-base balance, improved distribution of pulmonary blood flow, and cardiovascular stability in the liquid ventilated preterm animal support the use of this alternative method of ventilation as a valuable experimental tool and potential clinical therapeutic modality during early development. The evolution of this approach is presented in this article.