The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

OBSERVATIONSOF A RUPTURE IN THE ALVEOLAR EPITHELIUM DUE TO HIGH VENTILATORY PRESSURES.

DanielJ Marek BS, Alexander Adams RRT, David Dries MD, John Marini MD,John Hotchkiss MD. Regions Hospital ? HealthPartners, Univ. of Minn., St. Paul,MN.

Background:Patients with ALI or ARDS can require high ventilatory pressures to maintainadequate gas exchange. Such pressures may cause damage to the alveolar epitheliumand lead to ventilator-induced lung injury (VILI). Currently, the relative rolesof inflammation and mechanical stress in the evolution of lung injury are beinginvestigated. The actual damage caused by mechanical stress can be postulatedbut has not been clearly identified. Using scanning electron microscopy (SEM),we obtained images of lung tissue ventilated under low and high mechanical stressconditions.

Methods: In anisolated, perfused rat lung model, rat lungs were extracted, perfused, and ventilatedfor 2 hours at a pressure of either Pset=30/PEEP=3 cmH2O or 20/10cmH2O. The lungs were harvested, CPAP of 20 cmH2O wasapplied and the lungs were fixed with 3% glutaraldehyde. Random samples of lungunderwent SEM preparation using the Murakami and OTO methods followed by criticalpoint drying. Images were captured using a Hitachi S-4700 FESEM scanning electronmicroscope.

Observations:Figure 1 - SEM image of alveolar epithelium from rat lung ventilated at 30/3.NOTE: The obvious rupture in the alveolar epithelium. Figure 2 - SEM image ofalveolar epithelium ventilated at 20/10. NOTE: An alveolar pore of Kohn identifiedin lung ventilated at 20/10. Ruptures were not observed in the 20/10 lung..

Conclusion: Analveolar rupture can be easily identified by SEM. Using SEM, studies that quantifyand locate ruptures may help determine the precise mechanical-stress mechanismsof VILI.

Figure1Figure 2

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