A Rationale for Recruitment Maneuvers in ARDS

Evidence from a variety of experimental models, coupled with intriguing clinical data, has intensified interest in using an "open lung" strategy for ventilatory management of acute respiratory distress syndrome (ARDS). In this approach, emphasis is placed on establishing and maintaining patency of potentially recruitable airspaces throughout the tidal cycle. Because positive end-expiratory pressure (PEEP) counterbalances the tendency for airway closure and small tidal volumes limit peak tidal pressure, a high PEEP/low tidal volume strategy may offer the best chance of avoiding injurious cycles of ventilation. It must be understood that PEEP holds open unstable lung units but does not itself open them. Recruitment maneuvers are intended to establish alveolar patency that may be maintained at lower tidal pressures and PEEP levels than would otherwise be required. As we investigate the role of recruitment maneuvers in the laboratory and clinic, many questions remain. Should recruitment be our objective when closed lung regions require such high pressures such that opening and closure would not otherwise occur? What is the most effective recruitment method? How should recruitment be monitored? Are serial maneuvers needed, and if so, how should they be spaced? Definitive answers will require additional laboratory and bedside investigation.