Second, all the trials enrolled in this meta-analysis applied lower VTs, higher PEEP and recruitment manoeuvres in the protective ventilation group; it seems impossible to simply attribute the beneficial effects to just one of these components.
We hypothesized that low VT and low PEEP without RM may result in less biological impact in lung tissue compared to a ventilator strategy with low VT, high PEEP and RMs.
At equal Vt, high PEEP resulted in higher plateau pressure at end-inspiration compared with low PEEP.
In patients with ARDS, the pathophysiology of ΔRESPPP may differ from that of healthy lungs because of low tidal volume (Vt), high respiratory rate, decreased lung and sometimes chest wall compliance, which increase alveolar and/or pleural pressure.
We studied four groups: Low VT-SDD, High VT-SDD, Low VT-vehicle and High VT-vehicle (n=20 per group).
Studies that have addressed this issue in surgical patients have found no differences in the lung inflammatory response or outcome between low Vt or high Vt with short ventilatory times (from 1 to 3 hours) [ 23, 24], but found that high Vt increases proinflammatory mediators with longer ventilatory times [ 25- 27].
In this line, patients with brain damage are usually ventilated with VT higher than 6 mL/kg and low PEEP [ 2], even though it may be associated with lung damage, inflammation and, ultimately, organ failure [ 25].
Furthermore, low VT with high PEEP compared to high VT and low PEEP has been found to prevent postoperative pulmonary complications in patients with non-injured lungs [ 23].
Prior to endotoxin administration (see the "Experimental protocol" section below), animals were allocated sequentially to protective ventilation (low VT and high PEEP) or injurious ventilation (high VT and low PEEP), which was continued for 2 h.
Low VT with high PEEP was lung-protective, and early pentoxifylline reduced the inflammatory response to high VT with high PEEP (and presumed lung overdistention) during mechanical ventilation.
