The pulmonary surfactant (PS) is a complex mixture of lipids and proteins dispersed in the aqueous lining layer of the alveolar surface. Such a layer plays a key role in maintaining the proper lung functionality. It acts as a barrier against inhaled particles and pathogens, including viruses, and may represent an important entry point for drugs delivered via aerosols. Understanding the physicochemical properties of PS is therefore of importance for the comprehension of pathophysiological mechanisms affecting the respiratory system. That can be of particular relevance for supporting the development of novel therapeutic interventions against COVID-19–induced acute respiratory distress syndrome. Owing to the complexity of the in vivo alveolar lining layer, several in vitro methodologies have been developed to investigate the functional and structural properties of PS films or interfacial films made by major constituents of the natural PS. As breathing is a highly dynamic interfacial process, most applied methodologies for studying PSs need to be capable of dynamic measurements, including the study of interfacial dilational rheology. We provide here a review of the most frequently and successfully applied methodologies that have proven to be excellent tools for understanding the biophysics of the PS and of its role in the respiratory mechanics. This overview also discusses recent findings on the dynamics of PS layers and the impact of inhalable particles or pathogens, such as the novel coronavirus, on its functionality.

肺表面活性剂 (PS) 是一种复杂的脂质和蛋白质混合物，分散在肺泡表面的水性衬里层中。这样的层在维持适当的肺功能方面起着关键作用。它可作为抵御吸入颗粒和病原体（包括病毒）的屏障，并且可能是通过气溶胶输送药物的重要切入点。因此，了解 PS 的理化特性对于理解影响呼吸系统的病理生理机制非常重要。这对于支持开发针对 COVID-19 引起的急性呼吸窘迫综合征的新型治疗干预措施尤其重要。由于体内肺泡内衬层的复杂性，已经开发了几种体外方法来研究 PS 膜或由天然 PS 的主要成分制成的界面膜的功能和结构特性。由于呼吸是一个高度动态的界面过程，因此大多数用于研究 PS 的应用方法都需要能够进行动态测量，包括界面扩张流变学的研究。我们在此回顾了最常用和最成功应用的方法，这些方法已被证明是了解 PS 的生物物理学及其在呼吸力学中的作用的绝佳工具。本概述还讨论了关于 PS 层动力学的最新发现以及可吸入颗粒或病原体（例如新型冠状病毒）对其功能的影响。