chapter  17
16 Pages

Lung Imaging of Ventilator-Associated Injury

WithJean-Jacques Rouby, Qin Lu

The concept of ventilator-induced lung injury includes three different patho-

physiological entities: high permeability type pulmonary edema resulting from high tidal volume ventilation-‘‘volutrauma’’ (1), lung inflammation

resulting from repetitive opening and closure of distal bronchioles-

‘‘biotrauma’’ (2), and mechanical distortion/overinflation of anatomical

lung structures (3). The first two have been identified from experimental stud-

ies (4,5) and have found some indirect confirmation in humans (6,7) but

remain to date a subject of controversy (8). The latter is a hallmark of human

ventilator-induced lung injury. Lung distortion/overinflation was discovered

on human lung autopsies more than 25 years ago (9-12), was recently demonstrated to result from prolonged mechanical ventilation in experimental

animals (13), and is easy to evidence using whole lung computed tomography

(CT) (14,15). Surprisingly, pulmonary edema resulting from ‘‘volutrauma’’

and lung inflammation resulting from ‘‘biotrauma’’ have been the focus,

the attention of most recent reviews on ventilator-induced lung injury despite

their uncertain human clinical relevance, whereas the well-demonstrated

morphological overinflation resulting from mechanical ventilation-induced distortion of human lungs is only incidentally reported. The present article

is aimed at reviewing the imaging of lung overinflation resulting from

mechanical ventilation. In critically ill patients with acute lung injury, whole

lung CT occupies a central role in evidencing pulmonary lesions resulting

from positive pressure ventilation.