  Objective: Collecting exhaled particles that represent small droplets of the
alveolar lining fluid shows great promise as a tool for pulmonary surfactant
(PS) sampling. For this purpose, we present a setup consisting of two modules,
namely, a module for droplet collecting, called an electrostatic aerosol
trapping (ESAT) system, and a measurement module for studying PS properties. We
suggest the way how to extract numerical values from the experimental data
associated with PS properties.
  Methods: The operating principle of ESAT is based on the electrostatic
precipitation of exhaled particles. The native material was collected directly
on the water surface, where an accumulated adsorbed film of PS was examined
with tensiometric method. The modified capillary waves method adapted to study
small volume samples was utilized. The efficiency of the setup was verified in
the experiments with healthy subjects.
  Conclusion: The accumulation of PS components on the water surface in an
amount sufficient for tensiometric study was reported. It was shown how to
extract the numerical values from the experimental data characterizing PS
properties.
  Significance: The idea underlying the new concept used in this study may give
impetus to further development of point-of-care facilities for collecting PS
samples and for their express analysis.
