Dynamic preload indices, such as pulse pressure variation (PPV) and stroke volume variation (SVV) are generally accepted as accurate indicator of fluid responsiveness in mechanically ventilated patients. Because SVV and PPV are generated by the pressure transmitted from the airways to the pleural and pericardial spaces, their reliability is limited in patients receiving low tidal volume (VT) ventilation and in those with a driving pressure lower than 20 cm H2O. Lung-protective ventilation using low VT with positive end expiratory pressure (PEEP) has recently been demonstrated to significantly improve postoperative outcome, and its application is gradually increasing in surgical patients. However, protective ventilation alters the predictability of dynamic preload indices and thus limits their use in the operating theatre. Lung recruitment maneuvers (LRMs), used to reopen collapsed lung, and PEEP have been proposed as the key components of lung-protective ventilation strategy. LRM increases intrathoracic pressure, which in turn causes a transient decrease in stroke volume (SV) and arterial pressure; this may depend on preload status. Interestingly, recent study reported that the augmented PPV during LRM using vital capacity maneuver (VCM, continuous positive airway pressure of 30 cm H2O for 10 s) could predict preload responsiveness under open chest condition. Investigators hypothesized that the augmented PPV and SVV by a stepwise LRM with incremental PEEP could represent a functional test to suggest preload responsiveness and, therefore, predict fluid responsiveness. The aims of the current study were (1) to assess the ability of augmented PPV and SVV during stepwise LRM-induced to predict fluid responsiveness in mechanically ventilated patients in the operating room, (2) to assess the ability of stepwise LRM-induced decrease in SV (ΔSV-LRM) to predict fluid responsiveness.
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PPV_augmented
Timeframe: During the last 5 second of lung recruitment maneuver
SVV_augmented
Timeframe: During the last 5 second of lung recruitment maneuver