Quantifying the Severity of Acute Lung Injury Using Dead-Space Ventilation: Should the Lung Injury Score Be Updated?

During the past decade of research on acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) there has been heightened interest in measuring physio-logic dead-space fraction (VD/VT). Since ARDS first was described 44 years ago, the primary focus on gas exchange abnormalities concerned oxygenation. In fact, until the pub-lication in 2002 by Nuckton et al,1 pulmonary dead-space ventilation was considered relevant only in the subacute or fibroproliferative phase.2 This impression probably re-flected preoccupation with the problem of improving ox-ygenation. In contrast, it was relatively easy to achieve normocapnia simply by raising minute ventilation. In ret-rospect, the advent of lung-protective ventilation and permis-sive hypercapnia focused more attention on the issue of im-paired carbon dioxide excretion in patients with ALI/ARDS