Effects of an open lung approach following the ARDS Network ventilatory strategy in patients with early acute lung injury/acute respiratory distress syndrome

Introduction

The beneficial effects of the institution of high levels of positive end-expiratory pressure (PEEP) after recruitment maneuvers are controversial. We aim to compare the effects of the ARDS Network (ARDSNet) ventilatory strategy and open lung approach (OLA) applied in a sequential way, in patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

Methods

Ten patients fulfilling criteria for early ALI/ARDS were recruited. For definitive selection, blood gas collected after 30 minutes application of 5 cmH₂O PEEP and tidal volume (VT) = 10 ml/kg had to demonstrate PaO₂/FIO₂ < 300 mmHg. The patients were initially ventilated for 24 hours according to the ARDSNet protocol. After this period, if the PaO₂/FIO₂ was ≤ 350 mmHg, a recruitment maneuver was performed (sequential 5 cmH₂O increments in PEEP starting from 20 cmH₂O, until PaO₂/FIO₂ > 350 mmHg) and an additional 24 hours of ventilation according to the OLA (VT = 6 ml/kg and PEEP to achieve a PaO₂/FIO₂ > 350 mmHg) was applied. Whole lung computed tomography images (1.0 mm thickness with 10 mm gap) were acquired after 24 hours of each strategy.

Results

The institution of OLA was necessary in nine of the 10 studied patients. The PEEP was significantly higher during OLA (17 cmH₂O (17–19) vs 8 cmH₂O (8–11); P = 0.007) and resulted in a significant improvement of oxygenation sustained for 24 hours of follow-up, with no significant differences in plateau pressure, static compliance, minute ventilation, PaCO₂ and pH (P > 0.1). OLA resulted in a significant reduction of the fraction of nonaerated regions as compared with the ARDSNet protocol (13% (10–23) vs 37% (33–42); P = 0.018) without a significant increase in the percentage of hyperinsufflation (5% (1–13) vs 2% (0–7); P = 0.149). No significant differences were observed in the infused doses of vasopressors, fluid balance and arterial blood pressure.

Conclusion

When compared with the ARDSNet protocol OLA improved oxygenation, reducing the fraction of nonaerated regions without significant increase in hyperinflated areas with comparable levels of hemodynamics and fluid balance.