The Effect of Two Levels of Pressure Support Ventilation on Tidal Volume Delivery and Minute Ventilation in Preterm Infants

Abstract

Objective: To study the effect of different levels of pressure support ventilation (PSV) on respiratory parameters in preterm infants during the weaning phase of mechanical ventilation.

Design/Methods: In this quasi-experimental crossover study, a total of 19,154 breaths were analyzed from 10 ventilated infants of <32 weeks’ gestation. Breath-to-breath data on minute ventilation, tidal volume, respiratory rate, peak inspiratory pressure and mean airway pressure were collected during three study epochs: synchronized intermittent mandatory ventilation (SIMV) alone, SIMV with partial PSV (PSmin), and SIMV with full PSV (PSmax). PSmin was set to provide an exhaled tidal volume (Vte) between 2.5-4 mL/kg and PSmax 5-8 mL/kg Vte. Statistical analyses were performed using analysis of variance (ANOVA) for repeated measures.

Results: The addition of full PSV (PSmax ) was associated with a significant increase in total minute ventilation as compared to SIMV alone (392 mL/kg/min vs. 270 mL/kg/min respectively ; p<0.05). This difference in minute ventilation was still present when PSmin was used (332 mL/kg/min as compared to 270 mL/kg/min in SIMV; p<0.05). There was also a concomitant decrease in the respiratory rate with both PSmax (59 breaths per minute) and PSmin (65 breaths per minute) compared to SIMV alone (72 breaths per min) (p<0.05).

Conclusions: Pressure support ventilation increases total minute ventilation and stabilizes breathing in proportion to the level of pressure support used. This may be advantageous and provide a useful ventilation strategy for use during weaning stages of mechanical ventilation in preterm infants.