Work of breathing during SIMV with and without pressure support.

Abstract

In a randomised trial, pressure support with synchronised intermittent mandatory ventilation (SIMV) compared to SIMV alone was associated with a significant reduction in supplementary oxygen duration. The hypothesis that the addition of pressure support to SIMV compared to SIMV alone would reduce the work of breathing was examined. Prospective study. Perinatal service. 20 infants, with a mean gestational age of 31 weeks, being weaned from mechanical ventilation were studied. 1 h periods of SIMV and SIMV with pressure support at 50% of the difference between the peak inflating pressure and positive end expiratory pressures. The work of breathing was assessed by measurement of the transdiaphragmatic pressure time product (PTPdi). The mean PTPdi on SIMV plus pressure support was 112 cm H(2)Oxs/min, approximately 20% lower than that on SIMV alone (141 cm H(2)Oxs/min) (p<0.001). The addition of pressure support to SIMV reduces the work of breathing in infants being weaned from the ventilator.