The Open Lung Concept: pressure controlled ventilation is as effective as high frequency oscillatory ventilation in improving gas exchange and lung mechanics in surfactant-deficient animals

Objective:To demonstrate in experimental animals with respiratory insufficiency that under well-defined conditions, commercially available ventilators allow settings which are as effective as high frequency oscillatory ventilators (HFOV), with respect to the levels of gas exchange, protein infiltration, and lung stability. Design: Prospective, randomized, animal study. Setting: Experimental laboratory of a university. Subjects: 18 adult male Sprague-Dawley rats. Interventions: Lung injury was induced by repeated whole-lung lavage. Thereafter, the animals were assigned to pressure-controlled ventilation (PCV) plus The Open Lung Concept (OLC) or HFOV plus OLC (HFOOLC). In both groups, an opening maneuver was performed by increasing airway pressures to improve the arterial oxygen tension/fractional inspired oxygen (PaO2/FIO2) ratio to greater than or equal to 500 mm Hg; thereafter, airway pressures were reduced to minimal values, which kept PaO2/FIO2 greater than or equal to 500 mm Hg. Pressure amplitude was adjusted to keep CO2 as close as possible in the normal range. Measurements and results: Airway pressure, blood gas tension, and arterial blood pressure were recorded every 30 min. At the end of the 3-h study period, a pressure-volume curve was recorded and bronchoalveolar lavage was performed to determine protein content. After the recruitment maneuver, the resulting mean airway pressure to keep a PaO2/FIO2 greater than or equal to 500 mm Hg was 25 +/- 1.3 cm H2O during PCVOLC and 25 +/- 0.5 cm H2O during HFOVOLC. Arterial oxygenation in both groups was above greater than or equal to 500 mm Hg and arterial carbon dioxide tension was kept close to the normal range. No differences in mean arterial pressure, lung mechanics and protein influx were found between the two groups. Conclusions: This study shows that in surfactant-deficient animals, PCV, in combination with a recruitment maneuver, opens atelectatic lung areas and keeps them open as effectively as HFOV.