Simulation of Oxygentransport through alveolar Membranes

Background: In higher developed organisms differentiated airways deliver oxygen (O2) deep into alveolar spaces, where O2 and carbon dioxide (CO2) in exchange, had to be transported through different tissues into the blood compartment. A detailed BfR analysis of aspiration cases with liquid preparations of lamp oils showed, that the aspiration risk is clearly associated with the ingestion of distinct aliphatic hydrocarbons (C8 – C16 paraffines) characterised by low viscosity, low surface tension and low vapour pressure. These substances can enter into the deep alveolar spaces combined with signs of the lack of oxygenation. This gives strong clinical indications for an O2 intra-alveolar diffusion barrier effect. To prove this hypothesis, the intra-alveolar surface and the O2 transfer was simulated in an Alveolar Space Chamber (ASC) experiment. Method: A gas-tight Plexiglass®- measuring chamber (diameter 115 mm, height 115 mm, wall thickness 15 mm) is half-filled with Fluorocarbon (FC-43) to generate a liquid-gas surface to simulate the alveolar surface. The O2 transport through the surface is measured in the bottom liquid part of the chamber by a Unisense oxygen micro sensor®, connected to a high-sensitivity Picoam-meter®. Studies were carried out with O2 diffusion through liquid-gas surfaces which had been surface donated with water, distinct C8 – C16 paraffins and surfactant (Curosurf®) for medical care. Results: The results of the experiments reveal that the alveolar surfactant can be considered as a strong accelerator of the O2 transfer into the capillary lung system. In contrast to these findings, generated microfilms of paraffines are reducing the transfer of oxygen through the surface to a high extend (min. 9-15 fold). Transferring these findings to the clinical course of the documented serious lamp oil aspiration, the ASC-experiment could give clear indications of the pathophysiological mechanism. The characteristic physico-chemical properties of ingested lamp oils give these liquids the empowerment to spread deep into the lung, finally into the alveolar spaces with the effect to build up a persistent diffusion barrier for O2. Conclusion: The ASC-experiment could explain the clinical findings in cases of serious lamp oil aspirations and might assign a new physiological surfactant function: Following the results, alveolar surfactant might act as a physiological diffusion accelerator for O2.