Methods: A randomized, controlled trial was conducted on 122 neonates (birth weight = 600 to 1500 gm) requiring mechanical ventilation within 48 hours of birth. Neonates were randomly assigned (stratified at 1000 gm) to AC/FS (n = 60) or IMV (n = 62) ventilation. Failure was defined as the need for high frequency ventilation (air leak and/or failure to oxygenate). The primary outcome was the time to attaining (pre-defined) extubation criteria. Patient demographics revealed no significant differences between groups. To determine whether extremely low birthweight infants benefitted by patient-triggered synchronous ventilation, we stratified the analysis by birthweight.

Results: There were no significant differences in the use of muscle blockade (p=0.16), distribution of intraventricular hemorrhage(p=0.24), pulmonary interstitial emphysema (p=0.24), pneumothorax (p=0.16), diagnosis of bronchopulmonary dysplasia (p=0.62), or number of surfactant doses (p=0.09). There was no difference in death rate between groups (p=0.70). Neonates were successfully managed with AC/FS in 90% of cases vs. 78% in IMV (p=0.07). Neonates on AC/FS ventilation reached extubation criteria sooner than those on IMV (AC/FS=1.9 ±1.7 days, IMV=4.3±6.6 days, p=0.02; excluding patients that failed or expired).

Analysis of birthweight-specific strata revealed an inverse relationship between birthweight and duration of ventilation in the IMV group (6.2 ± 8.9 days for 600-999gm and 2.7 ± 3.3 days for >1000gm). This was not observed with AC/FS mode (1.9 ± 1.5 days for 600-999gm and 1.8 ± 2.0 days for >1000gm) where duration of mechanical ventilation was not related to birthweight. There was a 3.3-fold difference in time to extubation criteria between groups (AC/FS 1.9 days; IMV 6.2 days; p=.038) in neonates 600-999 gram birthweight. There was no significant difference between modes in the larger birthweight strata. The percent of neonates who were excluded due to death and/or failure were higher in IMV groups (600-999 gm: IMV = 29%vs. AC/FS = 16%, p=.20; >1000 gm: IMV = 13% vs. AC/FS = 11%, p=.80), but this did not reach significance.

Conclusion: In VLBW infants, especially those of extremely low birthweight, there is a significant advantage to patient-triggered synchronized modes of ventilation.