Regional lung volume changes in children with acute respiratory distress syndrome during a derecruitment maneuver

Objective: Regional differences in lung volume have been described in adults with acute respiratory distress syndrome, but it remains unclear to what extent they occur in children. To quantify regional alveolar collapse that occurred during mechanical ventilation during a standardized suctioning maneuver, we evaluated regional and global relative impedance changes (relative Delta Z) in children with acute respiratory distress syndrome using electrical impedance tomography. Design: Prospective observational trial. Setting: A 30-bed pediatric intensive care unit. Patients: Six children with acute respiratory distress syndrome. Interventions: Standardized suctioning maneuver. Measurements and Main Results: By comparing layers from nondependent (layers 1 and 2) to dependent lung areas (layers 3 and 4), it was demonstrated that the middle layers (2 and 3) had the greatest ventilation-induced change in relative Delta Z; layer 4 showed the least ventilation-induced change in relative Delta Z. During suctioning, layers 1, 2, and 3 showed a negative change in relative Delta Z, whereas layer 4 showed no significant change in relative Delta Z. The derecruitment-induced change in relative Delta Z representing the lung-volume loss was -9.8 (-3.0 mL/kg) during the first suctioning maneuver, -16.1 (-5.4 mL/kg) during the second, and -21.7 (-7.4 mL/kg) during the third. The ventilation-induced change in relative Delta Z during mechanical ventilation remained unchanged after suctioning (mean change in relative Delta Z before vs. after suctioning, 40.1 +/- 9.1 vs. 41.4 +/- 10.8; p = .30). Dynamic compliance was 11.8 +/- 6.1 mL.cm H2O-1 before and 11.8 +/- 6.9 mL.cm H2O-1 after the suctioning sequence (p = .90). Conclusions: Considerable regional heterogeneity was present during ventilation and a derecruitment maneuver. Significantly lower change in relative Delta Z in the most dependent lung regions suggests alveolar collapse during ventilation before suctioning.