687 possibility remains that the relationship with patient aver- major theoretical advantage of HFV to CMV is delivery ages, such as gestational age and birth weight, across trials of smaller tidal volumes to an optimally recruited lung. was not the same as the relationship for patients within As this meta-regression analysis did not conﬁrm that trials, and therefore an effect of these patient characteris- subgroups of more premature neonates, avoidance of tics cannot be excluded but only considered in relation to CMV prior to initiating HFV, or neonates with higher other covariates [25]. risk of CLD were more likely to beneﬁt form elective Similar ﬁndings of the effects of ventilation strategies HFV in IRDS, future research should be directed at have been reported by us and other authors as well [4, 5]; identifying patients in whom HFV does have a beneﬁt however, meta-analyses are subject to bias when differ- over CMV. To improve the robustness of these conclusions ences among trials are used to explain differences in re- and to avoid the limitations of meta-analysis of trials, an ported RRs. In this meta-regression analysis we were able individual-patient-data-based meta-regression analysis to estimate adjusted association measures, thereby dimin- should be conducted. ishing the effects of possible confounders/effect-modiﬁers. By calculating less biased estimates of the effects of ven- tilation strategies and the effect of using a Sensormedics Conclusion ventilator instead of other ventilators on the outcome in the different HFV trials we were able to reinforce the hy- In conclusion, conﬁning randomized trails to smaller or pothesis that ventilation strategies are more important than more premature children with IRDS did not seem to re- type of ventilator to prevent CLD. sult in better pulmonary outcomes of HFV compared with The results of this meta-analysis stresses the impor- CMV. 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