Relationship to previous studies
ventilator lung injury
PATHOGENESIS, RECRUITMENT, PNEUMOPERITONEUM
In our recent randomised trial of patients undergoing major surgery, we found no overall benefit of LTVV relative to conventional tidal volume ventilation when PEEP was equalised between groups [Previous studies of the effect of LTVV during laparoscopic surgery have been small, underpowered, and focused on physiological rather than clinical outcomes; further, they have been often confined to highly specific operative procedures [Our results could be explained by the physiological effects of the pneumoperitoneum on transpulmonary pressure (particularly in the context of moderate PEEP as in our trial). When only moderate PEEP is applied to patients with raised intrabdominal pressure, prevailing conditions are established which may promote suboptimal recruitment and reduced functional residual capacity. When a higher tidal volume is then applied, it is plausible that patients would be subjected to higher lung strain (defined as a ratio of tidal volume to end expiratory lung volume). Increased lung strain (and its surrogate driving pressure) has been identified as an important factor in the pathogenesis of ventilator lung injury [