Biophysical function of pulmonary surfactant in liquid ventilation

Liquid ventilation is a mechanical ventilation technique in which the entire or part of the lung is filled with oxygen-ated perfluorocarbon (PFC) liquids rather than air in conventional mechanical ventilation. Despite its many ideal bio-physicochemical properties for assisting liquid breathing, a general misconception about PFC is to use it as a replacement for pulmonary surfactant. Because of the high PFC-water interfacial tension (59 mN/m), pulmonary surfactant is indispensable in liquid ventilation to increase lung compliance. However, the biophysical function of pulmonary surfactant in liquid ventilation is still unknown. Here, we have studied the adsorption and dynamic surface activity of a natural surfactant preparation, Infasurf, at the PFC-water interface using constrained drop surfactometry. The constrained drop surfactometry is capable of simulating the intra-alveolar microenvironment of liquid ventilation under physiologically relevant conditions. It was found that Infasurf adsorbed to the PFC-water interface reduces the PFC-water interfacial tension from 59 mN/m to an equilibrium value of 9 mN/m within seconds. Atomic force microscopy revealed that after de novo adsorption, Infasurf forms multilayered structures at the PFC-wa-ter interface with an average thickness of 10-20 nm, depending on the adsorbing surfactant concentration. It was found that the adsorbed Infasurf film is capable of regulating the interfacial tension of the PFC-water interface within a narrow range, between X12 and-1 mN/m, during dynamic compression-expansion cycles that mimic liquid ventilation. These findings have novel im-plications in understanding the physiological and biophysical functions of the pulmonary surfactant film at the PFC-water inter-face, and may offer new translational insights into the development of liquid ventilation and liquid breathing techniques.

Automated summary

Liquid ventilation is a mechanical ventilation technique that uses oxygen-ated perfluorocarbon (PFC) liquids to fill the lung. It is important to use pulmonary surfactant in addition to PFC, as PFC cannot replace the function of surfactant in reducing interfacial tension and increasing lung compliance. This study explores the adsorption and surface activity of a natural surfactant at the PFC-water interface, revealing its role in regulating interfacial tension during liquid ventilation.