How to monitor lung recruitment in patients with acute lung injury.

PURPOSE OF REVIEW: Bedside assessment of lung recruitment is critical for setting mechanical ventilation during acute respiratory distress syndrome. We review recent findings on this topic and attempt to provide a clinical approach to estimating lung recruitment. RECENT FINDINGS: Because of intrinsic limitations in considering single parameters of gas exchange as tools to estimate lung recruitment, investigators have combined different respiratory variables, including respiratory mechanics, to enhance the likelihood of predicting lung recruitment. Confusions on interpreting the physiologic rationale of gas-exchange variations as associated with lung recruitment are still widespread. Techniques of lung imaging, in particular computed-tomography scanning, are still the most applied for reference measurement. Dynamic computed-tomography scanning may allow continuous monitoring of the effects of mechanical ventilation on lung parenchyma. Among the new techniques proposed, electric impedance and positron emission tomography are the most promising. Despite progress, computed-tomography scanning still represents the best technique to measure lung recruitment in clinical practice. SUMMARY: Two approaches should be considered to estimate lung recruitment: the use of computed-tomography scanning and indices combining different respiratory variables. Future studies, especially on lung-perfusion distribution, are warranted to improve our knowledge of the pathophysiology of lung recruitment.