title: Micromechanics of alveolar edema.
abstract: The decrease of lung compliance in pulmonary edema underlies ventilator-induced lung injury. However, the cause of the decrease in compliance is unknown. We tested the hypothesis that in pulmonary edema, the mechanical effects of liquid-filled alveoli increase tissue stress in adjacent air-filled alveoli. By micropuncture of isolated, perfused rat lungs, we established a single-alveolus model of pulmonary edema that we imaged using confocal microscopy. In this model, we viewed a liquid-filled alveolus together with its air-filled neighbor at different transpulmonary pressures, both before and after liquid-filling. Instilling liquid in an alveolus caused alveolar shrinkage. As a result, the interalveolar septum was stretched, causing the neighboring air-filled alveolus to bulge. Thus, the air-filled alveolus was overexpanded by virtue of its adjacency to a liquid-filled alveolus. Confocal microscopy at different depths of the liquid-filled alveolus revealed a meniscus. Lung inflation to near-total lung capacity (TLC) demonstrated decreased compliance of the air-filled but not liquid-filled alveolus. However, at near TLC, the air-filled alveolus was larger than it was in the pre-edematous control tissue. In pulmonary edema, liquid-filled alveoli induce mechanical stress on air-filled alveoli, reducing the compliance of air-filled alveoli, and hence overall lung compliance. Because of increased mechanical stress, air-filled alveoli may be susceptible to overdistension injury during mechanical ventilation of the edematous lung.
authors.affiliation: Department of Medicine, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
authors.forename: Carrie E
authors.initials: CE
authors.lastname: Perlman
authors.forename: David J
authors.initials: DJ
authors.lastname: Lederer
authors.forename: Jahar
authors.initials: J
authors.lastname: Bhattacharya
mesh_terms: D000399:Air Pressure; D000818:Animals; D005652:Functional Residual Capacity; D008170:Lung Compliance; D008297:Male; D018613:Microscopy, Confocal; D008954:Models, Biological; D010477:Perfusion; D011650:Pulmonary Alveoli / Q000293:injuries / Q000473:pathology / Q000503:physiopathology*; D011654:Pulmonary Edema / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012709:Serum Albumin / Q000008:administration & dosage; D013314:Stress, Mechanical; D013500:Surface Tension; D014109:Total Lung Capacity; D055397:Ventilator-Induced Lung Injury / Q000209:etiology / Q000503:physiopathology
chemical_list: D012709:Serum Albumin