Figure 2
Alveolar stability in the control and Tween-injured lung. In the phase I protocol alveolar stability (I-EΔ) was determined for all nine combinations of tidal volume (Vt) and positive end-expiratory pressure (PEEP). (a) Note very stable alveoli (low I-EΔ), regardless of PEEP and Vt, in normal lungs before endotracheal instillation of Tween (Additional file 1). (b) After Tween instillation, ventilation with the highest Vt (15 cc/kg) combined with the lowest PEEP (5 cmH2O) caused the greatest alveolar instability (highest I-EΔ; Additional file 2), whereas ventilation with the lowest tidal volume (6 cc/kg) and highest PEEP (20 cmH2O) resulted in the most stable alveoli (lowest I-EΔ). *The two Vt/PEEP combinations selected for use in the 3-hour ventilator-induced lung injury protocol (phase II).