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Mechanisms of recruitment in oleic acid-injured lungs.

Authors
Type
Published Article
Journal
Journal of applied physiology (Bethesda, Md. : 1985)
Publication Date
Volume
90
Issue
5
Pages
1744–1753
Identifiers
PMID: 11299264
Source
Medline
License
Unknown

Abstract

Lung recruitment strategies, such as the application of positive end-expiratory pressure (PEEP), are thought to protect the lungs from ventilator-associated injury by reducing the shear stress associated with the repeated opening of collapsed peripheral units. Using the parenchymal marker technique, we measured regional lung deformations in 13 oleic acid (OA)-injured dogs during mechanical ventilation in different postures. Whereas OA injury caused a marked decrease in the oscillation amplitude of dependent lung regions, even the most dependent regions maintained normal end-expiratory dimensions. This is because dependent lung is flooded as opposed to collapsed. PEEP restored oscillation amplitudes only at pressures that raised regional volumes above preinjury levels. Because the amount of PEEP necessary to promote dependent lung recruitment increased the end-expiratory dimensions of all lung regions (nondependent AND dependent ones) compared with their preinjury baseline, the "price" for recruitment is a universal increase in parenchymal stress. We conclude that the mechanics of the OA-injured lung might be more appropriately viewed as a partial liquid ventilation problem and not a shear stress and airway collapse problem and that the mechanisms of PEEP-related lung protection might have to be rethought.

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