Multislice spiral computed tomography to determine the effects of a recruitment maneuver in experimental lung injury

Although recruitment of atelectatic lung is a common aim in acute respiratory distress syndrome (ARDS), the effects of a recruitment maneuver have not been assessed quantitatively. By multislice spiral CT (MSCT), we analyzed the changes in lung volumes calculated from the changes in the CT values of hyperinflated (V_HYP), normally (V_NORM), poorly (V_POOR) and nonaerated (V_NON) lung in eight mechanically ventilated pigs with saline lavage-induced acute lung injury before and after a recruitment maneuver. This was compared to single slice analysis near the diaphragm. The increase in aerated lung was mainly for V_POOR and the less in V_NORM. Total lung volume and intrathoracic gas increased. No differences were found for tidal volumes measured by spirometry or determined by CT. The inspiratory-expiratory volume differences were not different after the recruitment maneuver in V_NON (from 62±18 ml to 43±26 ml, P=0.114), and in V_NORM (from 216±51 ml to 251±37 ml, P=0.102). Single slice analysis significantly underestimated the increase in normally and poorly aerated lung. Quantitative analysis of lung volumes by whole lung MSCT revealed the increase of poorly aerated lung as the main mechanism of a standard recruitment maneuver. MSCT can provide additional information as compared to single slice CT.