Effect on respiratory function of pressure support ventilation versus synchronised intermittent mandatory ventilation in preterm infants.

Our objective was to compare the effects of pressure support ventilation and synchronized intermittent mandatory ventilation on respiratory function in preterm babies. Twenty preterm infants (mean gestational age, 29 weeks; mean weight at study, 1,354 g) were evaluated. Patients received two repeated cycles of synchronized intermittent mandatory ventilation, alternated with pressure support ventilation, for a total of four alternated phases, each phase lasting 4 hr. Spontaneous respiratory rate, tidal volume, minute volume, and mean airway pressure were recorded hourly. The tidal volume released by the ventilator was limited to 6 ml/kg. During the two pressure support ventilation phases, a statistically significant reduction of respiratory rate and a significant increase of tidal and minute volume were noted, as compared to the two synchronized intermittent mandatory ventilation periods. Mean airway pressure significantly increased only after the first shift from synchronized intermittent mandatory ventilation to pressure support ventilation. The changes of minute volume and respiratory rate observed during pressure support ventilation did not persist after the return to synchronized intermittent mandatory ventilation. In conclusion, pressure support ventilation, as compared to synchronized intermittent mandatory ventilation, seemed to improve respiratory function in preterm infants.