Conventional tidal volume mechanical ventilation causes lung injury in premature lambs with RDS, characterized by progressive deterioration in gas exchange and lung inflammation. Lung recruitment strategies (HFOV and PLV) improve gas exchange and attenuate lung injury when instituted immediately after birth, however the effects of these strategies when used as rescue treatment after established lung injury are unknown. To determine the separate and combined effects of HFOV and PLV when initiated after the development of lung injury, we studied the effects of HFOV, PLV and HFOV+PLV on gas exchange and histologic injury markers (inflammation, alveolar hemorrhage, inflation) in premature lambs with RDS after 2 hours of conventional mechanical ventilation. At 115-117 days gestation (147 days, term), 18 animals were intubated, treated with surfactant and ventilated in FiO2 1.00 for 4 hours. After the first 2 hours of conventional ventilation, animals were treated with rescue therapies (HFOV, PLV, or HFOV+PLV). There were no significant differences in PaO2 among groups at the start of rescue therapies (2 hour timepoint). However, the control group showed progressive deterioration in gas exchange over the study period. By one hour of rescue therapy, PaO2 in the control group was lower than all other groups (P<0.05), but there were no significant differences in PaO2 among rescue groups. Responses to low-dose inhaled NO (5 ppm, 30 min)were measured at the end of the study. Inhaled NO improved PaO2 in all groups; however the increase in PaO2 was greatest in the HFOV+PLV group (P<0.05), despite a lower mean airway pressure compared to controls and HFOV (P<0.05). Histologic examination showed less alveolar hemorrhage and improved inflation in all rescue groups compared to controls(P<0.05). No differences in lung injury scores were noted among rescue groups, despite significantly higher mean airway pressure requirements in the HFOV group. All rescue therapies enhanced the response to inhaled NO, likely by improving lung recruitment, but the greatest improvement in oxygenation occurred with HFOV+PLV+iNO. We conclude that each lung recruitment strategy was effective in preventing progressive deterioration in oxygenation in premature lambs with established lung injury.