Lung recruitment and lung volume maintenance: a strategy for improving oxygenation and preventing lung injury during both conventional mechanical ventilation and high-frequency oscillation

Objective: To determine whether using a small tidal volume (5 ml/kg) ventil ation following sustained inflation with positive end-expiratory pressure ( PEEP) set above the critical closing pressure (CCP) allows oxygenation equa lly well and induces as little lung damage as high-frequency oscillation fo llowing sustained inflation with a continuous distending pressure (CDP) sli ghtly above the CCP of the lung. Material and methods: Twelve surfactant-depleted adult New Zealand rabbits were ventilated for 4 h after being randomly assigned to one of two groups: group 1, conventional mechanical ventilation, tidal volume 5 ml/kg, sustai ned inflation followed by PEEP > CCP; group 2, high-frequency oscillation, sustained inflation followed by CDP > CCP. Results: In both groups oxygenation improved substantially after sustained inflation (P < 0.05) and remained stable over 4 h of ventilation without an y differences between the groups. Histologically, both groups showed only l ittle airway injury to bronchioles, alveolar ducts, and alveolar airspace, with no difference between the two groups. Myleoperoxidase content in homog enized lung tissue, as a marker of leukocyte infiltration, was equivalent i n the two groups. Conclusions: We conclude that a volume recruitment strategy during small ti dal volume ventilation and maintaining lung volumes above lung closing is a s protective as that of high-frequency oscillation at similar lung volumes in this model of lung injury.