PROPOSED MECHANISM OF PULMONARY GAS TRAPPING (PGT) FOLLOWING INTRAVENOUS PERFLUOROCARBON EMULSION ADMINISTRATION

Purpose: To investigate various hypotheses and identify the most likel y mechanism preventing the complete collapse of test animal lungs at s acrifice subsequent to intravenous injection of certain perfluorocarbo n emulsions. Protocol: Literature data were reviewed, experimental dat a were extracted from completed studies and new data were generated in an attempt to delineate reasons why, in certain animals, lungs fail t o collapse normally at necropsy if previously injected with certain pe rfluorocarbon emulsions. The proposed hypothesis involved gas osmosis through endogenous pulmonary surfactant-liquid bridges (micro-bubbles) . Results: The observed effect of incomplete lung collapse upon necrop sy was found to correlate with perfluorocarbon vapor pressure. Results indicated that failure to collapse could be attributed to the formati on of intra-alveolar microbubbles induced by the normal pulmonary elim ination of perfluorocarbon vapor. These micro-bubbles result in a phen omenon which could be characterized by the term, pulmonary gas trappin g. Reduction of the perfluorocarbon concentration gradient across the bubble films by exposure to a perfluorocarbon vapor-containing atmosph ere was found to reduce the effect in-vivo and prevent gas osmosis bub ble growth in-vitro. Conclusion: Experimental observations are consist ent with the proposed theory of perfluorocarbon-related gas osmosis th rough micro-bubbles that prevent complete lung collapse as observed up on opening the thoracic cavity of test animals.