Fig. 1

Exposure of the natural PSurf to e-cigarette vapor. a Schematic diagram of the e-cigarette vapor exposure system. An electric air pump was used to blow the e-cigarette vapor into the measurement chamber with the vessel containing the natural PSurf film. A sensor probe for measuring surface pressure was inserted through an opening in the lid of the chamber. b The vaping protocol consisted of 5 vaping sessions 10 min apart. c Each vaping session contained 10 puffs of 3 s with a 15 s interval between puffs. d1 Control measurement of surface pressure (sPres) for natural PSurf, where the system is stabilized during the first 8 min after which the PSurf film is added (between 8 and 9 min), followed by a second stabilization phase for ~ 20 min, and the actual measurement starts at 30 min. In this control measurement, e-cigarette vapor is not added. d2 PSurf exposed to the e-liquid base solution, where the exposure is initiated at 30 min. d3 PSurf exposed to 50% vitamin E acetate (VEA) in a base solution. d4 PSurf exposed to a pure VEA solution. e Changes in the surface pressure of pulmonary surfactant model corresponding with representative curves depicted in panels d1–d4