Interaction between surfactant and ventilatory support in newborns with primary surfactant deficiency

The interaction between exogenous surfactant and various modes of ventilatory support in terms of timing, quality and quantity can influence both short- and long-term outcomes of immature infants. Alterations to the pulmonary surfactant system can occur with all forms of mechanical ventilation. Experimental data suggest possible interaction between ventilatory support and exogenous surfactant even during the first breaths in the delivery room. The adverse effect on surfactant function at this time can increase the need for and duration of ventilatory support. The logical approach to ventilatory support is to be minimally aggressive with optimal recruitment of the lungs to avoid ventilator-induced lung injury. Nasal continuous positive airway pressure (CPAP) in combination with early prophylactic surfactant administration may be an effective and less damaging method capable of reducing the need of artificial ventilation, but its benefit has not been proven in extremely preterm infants less than 28 weeks' gestation. Because of unproven efficacy of nasal CPAP in extremely premature infants, the population most at risk for adverse pulmonary and neurologic outcome, this paper focuses on the comparison of conventional and high-frequency oscillatory ventilation (HFOV) with respect to alteration of surfactant function, and short- and long-term outcomes, in both human and experimental trials. Though the two most recent large clinical trials provide reassurance with respect to the safety of first-intention high-frequency ventilation, the reduction in the risk of chronic lung disease appears to be only modest or absent. Recent laboratory investigations suggest that the key element of HFOV, namely optimization of volume, can, under some circumstances, be replicated with low tidal volume conventional ventilation and high positive end-expiratory pressure. Recent introduction of patient-triggered volume-targeted conventional ventilation into clinical practice offers the promise of a practical means of providing gentle conventional ventilation capable of minimizing ventilator-induced lung injury. Ultimately, well-designed comparative clinical trials with long-term outcomes are essential to accurately quantify risks and benefits of any new approach to mechanical ventilation. Without such data, these experimental results should not be extrapolated into clinical practice, because of the multifactorial pathophysiology of the development of chronic pulmonary disease in extremely premature infants and the risk of unanticipated adverse effects.