A COMPUTED-TOMOGRAPHY SCAN ASSESSMENT OF REGIONAL LUNG-VOLUME IN ACUTE LUNG INJURY

The lobar and cephalocaudal distribution of aerated and nonaerated lun g and of PEEP-induced alveolar recruitment is unknown in acute lung in jury (ALI). Dimensions of the lungs and volumes of aerated and nonaera ted parts of each pulmonary lobe were measured using a computerized to mographic quantitative analysis and compared between 21 patients with ALI and 10 healthy volunteers. Distribution of PEEP-induced alveolar r ecruitment along the anteroposterior and cephalocaudal axis and influe nce of the resting volume of nonaerated lower lobes were also assessed . Anteroposterior and transverse dimensions of the lungs of the patien ts were similar to those of healthy volunteers, whereas cephalocaudal dimensions were reduced by more than 15%. Total lung volume (aerated p lus nonaerated lung) was reduced by 27%. Volumes of upper and lower lo bes were 99 and 48% of normal values. In addition to an anteroposterio r gradient in the distribution of aerated and nonaerated areas, a ceph alocaudal gradient was also observed. Nonaerated areas were predominan tly found in juxtadiaphragmatic legions. PEEP-induced alveolar recruit ment was more pronounced in nondependent than in dependent regions and in cephalad than in caudal regions. A significant correlation between resting volume of nonaerated lower lobes and regional PEEP-induced al veolar recruitment was observed. In ALI, loss of lung volume involves predominantly lower lobes. The thorax shortens along its cephalocaudal axis. PEEP-induced alveolar recruitment predominates in nondependent and cephalad lung regions and is inversely correlated with the resting volume of nonaerated lung.