Validation of Digital Chest-X-ray (CXR) to Assess Lung Recruitment in ARDS

Lung recruitability is essential for optimal Positive end-expiratory pressure (PEEP) selection in ARDS patients. It is defined as the potential for the non aerated or poorly aerated lung mass to become aerated due to the increase in airway pressure. PEEP contributes to lung recruitment mostly by maintaining some amount of the end-inspiratory recruitment at the end of expiration. PEEP also stabilizes patency of the small airways and minimizes the repeated opening and closing of them during the breathing cycle, which is implicated in a further lung inflammation. The gold-standard method for assessing lung recruitability is lung CT scan. For economic and feasibility this technique cannot be used in routine. Therefore, techniques that can be used at the bedside to measure lung recruitability are very well known. The measurement of recruited lung volume (Vrec) by using pressure-volume curve generated by the ventilator is another reference method to approach lung recruitment. It can be done at the bedside. Chest-X-Ray (CXR) is an interesting option as done in routine in this setting. Furthermore, it allows quantifying aeration thanks numerical image processing and a regional approach. In a preliminary one-center study we found a significant negative correlation between the amount of Vrec and the reduction in lung density measured by digital CXR between 5 and 15 cm H2O PEEP. In present study we would like to extend this previous result on a larger number of patients in a multicenter investigation.