Oxygen transport through a model lung surfactant surface layer: influence of the film compression on the kinetics

The influence of the compression state of a model Lung Surfactant Surface Layer LSSL on the oxygen permeation kinetics was studied in vitro at 37 degrees C. In an attempt to mimic in vivo conditions, the oxygen from the air was allowed to cross a dipalmitoylphosphatidylcholine DPPC layer situated at an air/deaerated saline interface in an electrochemical vessel. The time dependent concentration change of the oxygen diffusing through this layer into the deaerated saline hypophase was measured electrochemically using a Hanging Mercury Drop Electrode HMDE, situated at a definite depth in the bulk of the saline. The surface pressure in the monolayer was monitored using a Wilhelmy balance. The oxygen permeability was measured through two differently compressed DPPC layers in which the area/phospholipid molecule differed by 30%. This is consistent with the difference in the alveolar area at the end-points of the compressed and expanded lung. The results, submitted to a linear regression analysis, showed that the DPPC film compression influences the oxygen permeation kinetics. The denser the lipid film, the slower the oxygen uptake by the deaerated hypophase. The results suggest that the LSSL might play an important role in the oxygen transport kinetics, the oxygen permeation through it being dependent on the actual lung area.