chapter  13
26 Pages

Biological Markers of Ventilator-Induced Lung Injury

WithThomas R. Martin, Michael A. Matthay

Mechanical ventilation is a lifesaving treatment in patients with acute

respiratory failure, regardless of whether respiratory failure is associated

with acute hypoxemia, acute hypercarbia, or both. Ventilator-induced lung

injury (VILI) occurs when mechanical breaths overdistend the alveolar units (1,2). In patients with normal lungs, such as patients with neuromus-

cular disease or injuries, or patients with acute poisonings who have not

aspirated, mechanical ventilation with relatively large tidal volumes (e.g.,

10-12 mL/kg measured body weight) does not seem to harm the lungs. In

fact, some recommendations for ventilating patients with neuromuscular

disease call for the use of larger tidal volumes (> 10 mL/kg) to prevent atelectasis. However, when major areas of alveolar collapse occur, as in

acute lung injury (ALI), the effective alveolar volume is substantially reduced, and a set tidal volume of 10 mL/kg body weight may be equivalent

to a set tidal volume of 20 mL/kg body weight or greater in a reduced alveo-

lar space. Such relatively high tidal volumes have the potential to overdis-

tend and damage the alveolar walls, but as yet there is no direct way to

estimate the effective alveolar volume in order to appropriately set the tidal volume. Investigators have worked to identify biomarkers of VILI so that

protective measures can be initiated as soon as possible to reduce the

chances of further lung injury. Biological markers also could be used to

make predictions about prognosis and to stratify patients into different risk

groups in order to apply appropriate new treatments. Lastly, biological

markers are useful in studying the pathophysiology of lung injury.