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 insuffici ency that under well-defined conditions, commercially available ventilators allow settings which are as effective as high frequency oscillatory ventil ators (HFOV), with respect to the levels of gas exchange, protein infiltrat ion, 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. There after, the animals were assigned to pressure-controlled ventilation (PCV) p lus 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 t o greater than or equal to 500 mm Hg; thereafter, airway pressures were red uced to minimal values, which kept PaO2/FIO2 greater than or equal to 500 m m Hg. Pressure amplitude was adjusted to keep CO2 as close as possible in t he 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 peri od, a pressure-volume curve was recorded and bronchoalveolar lavage was per formed to determine protein content. After the recruitment maneuver, the re sulting mean airway pressure to keep a PaO2/FIO2 greater than or equal to 5 00 mm Hg was 25 +/- 1.3 cm H2O during PCVOLC and 25 +/- 0.5 cm H2O during H FOVOLC. 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 nor mal range. No differences in mean arterial pressure, lung mechanics and pro tein 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.