Liquid-assisted ventilation: physiology and clinical application

Liquid-assisted ventilation, as an alternative ventilation strategy for respiratory distress, is progressing from theory and basic science research to clinical application. Biochemically inert perfluorochemical liquids have low surface tension and high solubility for respiratory gases. From early immersion experiments, two primary techniques for liquid-assisted ventilation have emerged: total liquid ventilation and partial liquid ventilation. While computer-controlled, time-cycled, pressure/volume-limited total liquid ventilators can take maximum advantage of these liquids by completely eliminating the gas phase in the distressed lung, partial liquid ventilation takes advantage of having these liquids in the lung while maintaining gas ventilation. The benefits of both partial and total techniques have been demonstrated in animal models of neonatal and adult respiratory distress syndrome, aspiration syndromes and congenital diaphragmatic hernia and also in combination with other therapeutic modalities including extracorporeal membrane oxygenation, high-frequency ventilation and nitric oxide. Additionally, nonrespiratory applications have expanding potential including pulmonary drug delivery and radiographic imaging. Since its use in neonates in 1989, liquid-assisted ventilation in humans has progressed to a variety of clinical experiences with different aetiologies of respiratory distress. The future holds the opportunity to clarify and optimize the potential of multiple clinical applications for liquid-assisted ventilation.