Studies on the mechanisms of VILI have identified several beneficial ventilation strategies, among them low tidal volume (V T ) ventilation and application of recruitment manoeuvres (RM) as well as high positive end-expiratory pressure (PEEP). Although RM have a sound physiological basis, it remains unclear how they should be applied [15] . In principal, RM may be used to reopen atelectatic lung areas in injured lungs or to prevent atelectasis in healthy lungs. The latter application requires lower recruitment pressures and hence can be applied more frequently. Without RM, pulmonary compliance is likely to decrease as shown already many years ago in anesthetized dogs both during spontaneous breathing and during mechanical ventilation [16] . In addition, regular short recruitment manoeuvres have proved to be useful in models of isolated rat and mouse lungs [17, 18] . In mechanically ventilated mice the usefulness of RM with the specific aim to keep pulmonary compliance and other lung functions constant has been explored only sporadically. Previous RM studies in healthy mice have focused on short periods of ventilation and potential lung injury, but did not compare ventilation with and without RM over several hours [4, 5] . In addition, the effect of RM on blood pressure in mice is not well defined, although increased intrathoracic pressure might decrease cardiac output [19] . The beneficial effects of PEEP have been demonstrated in several animal studies [20] [21] [22] . PEEP helps to prevent repetitive alveolar collapse and preserves surfactant function [1, 23] . While it is widely accepted that adequate PEEP together with low V T is a protective ventilation strategy, the effects of recurrent RM in this setting are unknown.