Objective: Several options are currently available in neonatal mechanical ventilation: complete breathing synchronization (patient triggered ventilation, synchronized intermittent positive pressure ventilation--SIPPV); positive pressure flow-cycled ventilation (pressure support ventilation, PSV); and volume targeted positive pressure ventilation (volume guarantee, VG). The software algorithm for the guarantee volume attempts to deliver a tidal volume (Vt) as close as possible to what has been selected by the clinician as the target volume. Main objectives of the present study were to compare patient-ventilator interactions and Vt variability in premature infants recovering from respiratory distress syndrome (RDS) who were weaned by various ventilator modes (SIMV/PSV + VG/SIPPV + VG and SIMV + VG).
Methods: This was a short-term crossover trial in which each infant served as his/her own control. Ten premature infants born before the 32nd week of gestation in the recovery phase of RDS were enrolled in the study. All recruited infants started ventilation with SIPPV and in the weaning phase were switched to synchronized intermittent mandatory ventilation (SIMV). Baseline data were collected during an initial 20-min period of monitoring with the infant receiving SIMV alone, then they were switched to SIPPV + VG for a 20-min period and then switched back to SIMV for 15 min. Next, they were switched to PSV + VG for the study period and switched back to SIMV for a further 15 min. Finally, they were switched to SIMV + VG and, at the end of monitoring, they were again switched back to SIMV alone.
Results: Each mode combined with VG discharged comparable Vts, which were very close to the target volume. Among the VG-combined modes, mean variability of Vt from preset Vt was significantly different. Variability from the target value was significantly lower in SIPPV and PSV modes than in SIMV (P < 0.0001 and P < 0.04 respectively). SIPPV + VG showed greater stability of Vt, fewer large breaths, lower respiratory rate, and allowed for lower peak inspiratory pressure than what was delivered by the ventilator during other modes. No significant changes in blood gases were observed after each of the study periods.
Conclusions: With regards to the weaning phase, among combined modes, both of the ones in which every breath is supported (SIPPV/PSV) are likely to be the most effective in the delivery of stable Vt using a low working pressure, thus, at least in the short term, likely more gentle for the neonatal lung. In summary, we can suggest that the VG option, when combined with traditional, patient triggered ventilation, adheres very closely to the proposed theoretical algorithm, achieving highly effective ventilation.
(c) 2007 Wiley-Liss, Inc.