March 2002 / Volume 47 / Number 3 / Page 0296
Lung Recruitment: The Role of Recruitment Maneuvers
IntroductionThere is increasing appreciation that lung-protective strategies are beneficial in patients with acute respiratory distress syndrome. Using low tidal volume in these patients improves survival. However, low tidal volume ventilation may promote alveolar de-recruitment. This has led some to advocate the use of "open lung" strategies that stress the use of high positive end-expiratory pressure levels and recruitment maneuvers. A recruitment maneuver is a sustained increase in airway pressure with the goal to open collapsed lung tissue. A variety of approaches have been used as recruitment maneuvers, including increasing the level of positive end-expiratory pressure, sustained inflation maneuvers, sigh breaths, spontaneous breathing, and others. There have been a number of recent reports describing improvements in arterial oxygenation with the use of recruitment maneuvers. However, the impact of recruitment maneuvers on patient-important outcomes such as survival is unknown.
Support for Lung Recruitment from Experimental Reports
Atelectasis During General Anesthesia
Acute Respiratory Distress Syndrome
Techniques to Facilitate Lung Recruitment
Increased Positive End-Expiratory Pressure
High-Frequency Oscillatory Ventilation
Biologically Variable Ventilation
One of the important advances in mechanical ventilation in recent years has been the recognition that mechanical ventilation can be not only lifesaving but can increase morbidity and mortality if applied improperly. Accordingly, there has been much attention directed to lung protection strategies during mechanical ventilation—particularly for patients with acute lung injury and acute respiratory distress syndrome (ARDS). Indeed, in such patients, a tidal volume (VT) of 6 mL/kg of predicted body weight has been shown to significantly improve survival, compared to a VT of 12 mL/kg. The lesions in the lungs of patients with early ARDS are heterogeneous, with areas of collapse, consolidation, and edema as well as parts of the lungs that are relatively spared of the disease. Ventilator-induced lung injury may occur secondary to either over-distention of alveoli (ie, a VT too high) or with repetitive opening and closure of lung units throughout the respiratory cycle. This injury can result in an inflammatory response that originates in the lungs and can spill into the systemic circulation, affecting distal organs, and ultimately producing multiple organ dysfunction syndrome.
The application of low VT ventilation may limit injury from alveolar overdistention. However, it will not prevent injury from repetitive alveolar opening and closing, and may promote alveolar collapse. A recruitment maneuver is a sustained increase in airway pressure with the goal to open collapsed lung tissue, after which sufficient positive end-expiratory pressure (PEEP) is applied to maintain the lungs open. The goals of such a technique are as a lung protection strategy, to decrease inflammation in the lungs, and to improve oxygenation. Much enthusiasm for the use of recruitment maneuvers has occurred since the report by Amato et al of a survival benefit associated with an "open lung" strategy. As part of their "open lung" strategy, Amato et al described the use of a "recruiting maneuver: an inspiratory pause of 10-20 s, with a constant airway pressure of 30-35 cm H2O." Herein we review the experimental, clinical, and technical aspects of recruitment maneuvers.