Comparison of effects of surfactant and inhaled nitric oxide in rabbits with surfactant-depleted respiratory failure.

Aim: To compare effects of pulmonary surfactant and inhaled nitric oxide (iNO) in improvement of survival and blood oxygenation in ventilated rabbits with acute hypoxic respiratory failure induced by repeated bronchoalveolar lavage (BAL).

Methods: After BAL all the rabbits had more than 50% reduction of dynamic lung compliance (Cdya), 50% increment of resistance of respiratory system (Rrs), and an increase of mean oxygenation index (OI) from 1 to 22. The rabbits were then randomly allocated to groups receiving (1) mechanical ventilation only (Control), (2) iNO 0.8 mumol.L-1 (20 ppm) (NO), (3) intratracheal bolus surfactant phospholipids at 100 mg.kg-1 (Surf), and (4) combined surfactant at 100 mg.kg-1 with inhaled NO at 0.8 mumol.L-1 (Surf + NO). All the rabbits were ventilated with standardized tidal volume (8-10 mL.kg-1) for another 8 h or until early death.

Results: The rabbits in both control and NO groups had the lowest survival rate, deterioration of lung mechanics and OI, whereas those in the Surf and Surf + NO groups had modestly improved Cdyn, Rrs, and OI. Only rabbits in the Surf + NO group had significantly improved survival rate and alveolar expansion.

Conclusion: Surfactant with or without iNO is more effective compared to the control and iNO groups in rabbit, suggesting that iNO is not effective unless a method to recruit alveoli is applied.